[1,2]Callum Witten

1]Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge,
CB3 0HA, UK

2]Kavli Institute for Cosmology, University of Cambridge, Madingley Road,
Cambridge, CB3 0HA, UK

3]Cavendish Labratory, University of Cambridge, Madingley Road, Cambridge, CB3
9BB, UK

4]Kavli Institute for Particle Astrophysics and Cosmology, Stanford
University, Stanford, CA 94305, USA

5]Institute for Astronomy, University of Edinburgh, Royal Observatory,
Edinburgh, EH9 3HJ, UK

6]Department of Physics and Astronomy, University College London, Gower
Street, London, WC1E 6BT, UK

7]Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD
21218, USA

8]Department of Astronomy and Astrophysics, University of California, Santa
Cruz, CA 95064, USA

9]Department of Physics, University of Oxford, Denys Wilkinson Building, Keble
Road, Oxford, OX1 3RH, UK

10]UCO/Lick Observatory, University of California, Santa Cruz, CA 95064, USA

11]Centro de Astrobiología, CSIC-INTA, Ctra. de Ajalvir km 4, Torrejón de
Ardoz, Madrid, E-28850, Spain

12]Department of Physics and Astronomy, University of California, Los Angeles,
CA 90095, USA

13]INAF - Osservatorio Astronomico di Roma, via di Frascati 33, 00078 Monte
Porzio Catone, Italy

# Deciphering Lyman-$\alpha$ Emission Deep into the Epoch of Reionisation

<EMAIL_ADDRESS>Nicolas Laporte  Sergio Martin-Alvarez  Debora Sijacki  Yuxuan
Yuan  Martin G. Haehnelt  William M. Baker  James S. Dunlop  Richard S. Ellis
Norman A. Grogin  Garth Illingworth  Harley Katz  Anton M. Koekemoer  Daniel
Magee  Roberto Maiolino  William McClymont  Pablo G. Pérez-González  Dávid
Puskás  Guido Roberts-Borsani  Paola Santini  Charlotte Simmonds  [  [ [ [ [ [
[ [ [ [ [ [ [

###### Abstract

During the epoch of reionisation the first galaxies were enshrouded in
pristine neutral gas, with one of the brightest emission lines in star-forming
galaxies, Lyman-$\alpha$ (Ly$\rm{\alpha}$), expected to remain undetected
until the Universe became ionised. Providing an explanation for the surprising
detection of Ly$\rm{\alpha}$ in these early galaxies is a major challenge for
extra-galactic studies. Recent JWST observations have reignited the debate on
whether residence in an overdensity of galaxies is a sufficient and necessary
condition for Ly$\rm{\alpha}$ to escape. Here, we take unique advantage of
both high-resolution and high-sensitivity images from the JWST instrument
NIRCam to reveal that all galaxies in a sample of $z>7$ Ly$\rm{\alpha}$
emitters have close companions. We exploit novel on-the-fly radiative transfer
magnetohydrodynamical simulations with cosmic ray feedback to show that
galaxies with frequent mergers have very bursty star formation which drives
episodes of high intrinsic Ly$\rm{\alpha}$ emission and facilitates the escape
of Ly$\rm{\alpha}$ photons along channels cleared of neutral gas. We conclude
that the rapid build up of stellar mass through mergers presents a compelling
solution to the long-standing puzzle of the detection of Ly$\rm{\alpha}$
emission deep into the epoch of reionisation.

Young, vigorously star-forming galaxies have been identified in the very early
Universe Curtis-Lake_2023 ; Arrabal-Haro23 ; Williams23 . These galaxies
should be excellent sources of Lyman-$\alpha$ emission (Ly$\rm{\alpha}$,
$\lambda$=1215.67Å) – the intrinsically brightest emission line
2014PASA…31…40D – which stems from the recombination of hydrogen that has been
ionised by their young stellar populations. However, deep in the epoch of
reionisation galaxies are expected to be exceptionally gas-rich such that
their stellar nurseries are enshrouded in copious amounts of neutral hydrogen,
which leads to extreme damped absorption of Ly$\rm{\alpha}$ Heintz+23 .
Furthermore, the intergalactic medium (IGM) is increasingly neutral as we
probe to higher redshift Robertson_2015 ; deBarros_2017 and this neutral gas
is expected to resonantly scatter Ly$\rm{\alpha}$ emission. Hence, due to
‘local’ attenuation by a gas-rich interstellar medium (ISM) and scattering by
a neutral IGM, Ly$\rm{\alpha}$ emission should only be detectable towards the
end of the reionisation era, about one billion years after the Big Bang
2014PASA…31…40D ; Endsley22 ; Bolan22 ; Hsiao23 .

While the decreasing observability of Ly$\rm{\alpha}$ emission with increasing
redshift has been repeatedly claimed to be observed Stark+17 ; deBarros+2019 ;
Jones+23 , this picture has been challenged by the occasional, surprising
detection of Ly$\rm{\alpha}$ emission in several galaxies deep in the
reionisation era Bunker+23 ; Jung2023 . It has been suggested that
Ly$\rm{\alpha}$ can escape through the neutral IGM if the galaxies reside in
sufficiently large ionised bubbles embedded within the neutral IGM, driven
either by active galactic nuclei (AGN) Laporte+17 ; Larson23 ; Maiolino+23_AGN
or by an enhanced radiation field produced by an overdensity of associated
objects Castellano+16 ; Tilvi+20 ; Leonova+22 ; Morishita+22 ; Tang+23 ;
Tacchella+23 ; Witstok+23 . However, a solution to the escape of
Ly$\rm{\alpha}$ emission through the ISM and CGM of what are expected to be
very gas-rich galaxies remains elusive. Before the advent of JWST, the
sensitivity and resolution of imaging instruments meant that studies of
Ly$\rm{\alpha}$ emitters (LAEs) at high redshift were spatially unresolved.
Hence, it was not possible to probe the physical processes that could explain
the escape of Ly$\rm{\alpha}$ emission from the ISM.

To address this crucial issue we study a sample of nine galaxies that have
been spectroscopically confirmed with the detection of Ly$\rm{\alpha}$
emission at $z>7$ with high-resolution spectrographs and which have been
observed with publicly-available JWST Near Infrared Camera (NIRCam) Rieke+23
imaging (the properties of which are reported in Table 1). These galaxies fall
within the GOODS-North, GOODS-South, EGS and COSMOS fields, and have been
observed as part of five different programs: PRIMER (PI: Dunlop), FRESCO (PI:
Oesch)Oesch+23 , CEERS (PI: Finkelstein)Bagley+23 , JADES (PI:
Eisenstein)Rieke+23b and DDT program 4426 (providing NIRSpec IFU observations
of GN-z11, PI: Maiolino)Maiolino+23_PopIII . Six of these nine
Ly$\rm{\alpha}$-emitting galaxies are known to lie within overdensities
Tang+23 ; Jung+2022 ; Leonova+22 ; Tacchella+23 ; Witstok+23 , three of which
also likely host accreting black holes Laporte+17 ; Larson23 ; Maiolino+23_AGN
. Moreover, it has been shown that the remaining galaxies are incapable of
alone blowing a large enough ionised bubble to facilitate the escape of
Ly$\rm{\alpha}$ through the neutral IGM, suggesting that an underlying
population of faint galaxies must be surrounding these LAEs Witstok+23 .

However, the presence of spectroscopically confirmed galaxies within known
ionised bubbles that do not show Ly$\rm{\alpha}$ emission Tang+23 ; Jones+23 ;
Witstok+23 indicates that there must be further local processes at play
driving Ly$\rm{\alpha}$ emission deep into the epoch of reionisation. With
this in mind, we use the unparalleled sensitivity and resolution of
JWST/NIRCam in order to accurately determine the properties of these nine
LAEs, with equivalent width (EW) greater than 10Å, at $z>7$.

Figure 1: An abundance of galaxy mergers seen with NIRCam. Cutouts of JWST
images (as different surveys make use of different filters, the filter within
which the companion is most clearly present is shown: F182M for GSDY and
z7-GSD-3811, F200W for EGSY8p68, F115W for CEERS-1027, JADES-GS-z7-LA and COSY
and F150W for JADES-GS+53.15682-27.7671 and z7-13433) showing the multiple
components of each system. All images are smoothed with a Gaussian of FWHM
$\sim 0.7$ kpc to enhance the visibility of the companion, except for EGSY8p68
where the three components become unresolved if we smooth the images. We
include the unsmoothed images as sub-panels in the top right of each panel in
order to emphasise that the companion is always visible before smoothing. We
use different colorbar ranges for each system in order to make the companion
galaxy well defined, hence some unsmoothed images can have what appears like a
nosier background than others. The position of the main target (*A in the
text) is displayed by an orange arrow, the position of the first companion
(*B) is indicated by a blue arrow and the third companion, if any, by a green
arrow. The name of each candidate is indicated in the bottom right corner, and
in the bottom left of each panel is a black scale showing 0.5′′.

Remarkably, NIRCam images of these galaxies reveal the presence of multiple
components to all of these LAEs, as shown in Figure 1. Given the tight
redshift constraints provided by strong [OIII]4959,5007 emission falling into
medium band filters, we estimate the probability of these being unrelated,
high-redshift objects and find this is always below $14\%$ for each of our
systems and is often just $1\%$ (see Methods for further details). We estimate
the redshift of each candidate companion by carefully extracting the Spectral
Energy Distribution (SED) of both the main component and its companions in
Extended Figure 2 and 3. We then fit each SED by assuming several parametric
star formation histories (SFH - burst, constant, delayed, exponential),
allowing a large range for all parameters Carnall2018 . In all cases, we
deduce the photometric redshifts of the companions to be consistent with that
of their spectroscopically-confirmed main component.

ID | z |  log($\rm{M_{*}[M_{\odot}]}$) |  SFR $\rm{[M_{\odot}/yr]}$ | Separation [kpc] |  LLyα [1043 erg/s] | $f_{esc}(\rm{Ly\alpha})$ | Reference
---|---|---|---|---|---|---|---
COSY-A | 7.142 |  8.77 ${}^{+0.02}_{-0.02}$ |  5.91 ${}^{+0.27}_{-0.25}$ | $-$ | 1.37 | $<0.1$ |  RB+16 ,Witten+23
COSY-B† | 7.142 |  7.59 ${}^{+0.13}_{-0.11}$ |  0.39 ${}^{+0.14}_{-0.08}$ | 2.8 | $-$ | $-$ |
JADES-GS-z7-LA-A | 7.278 |  6.72 ${}^{+0.14}_{-0.12}$ |  1.13${}^{+0.05}_{-0.03}$ | $-$ | 0.15 | $0.96\pm 0.22$ | Saxena+23
JADES-GS-z7-LA-B |  7.27${}^{+0.07}_{-0.06}$ |  7.68${}^{+0.18}_{-0.19}$ |  2.44${}^{+0.82}_{-0.47}$ | 1.2 | $-$ | $-$ |
z7-13433-A | 7.482 |  9.62 ${}^{+0.01}_{-0.01}$ |  42.19 ${}^{+1.09}_{-1.00}$ | $-$ | 1.00 | $-$ | Jung+2022
z7-13433-B | 7.478 |  8.67 ${}^{+0.03}_{-0.04}$ |  4.65 ${}^{+0.33}_{-0.36}$ | 2.6 | $-$ | $-$ |
z7-GSD-3811-A | 7.661 |  8.96 ${}^{+0.12}_{-0.13}$ |  9.25 ${}^{+2.79}_{-2.39}$ | $-$ | 0.386 | $0.22\pm 0.08$ |  Song+2016 , this work
z7-GSD-3811-B | 7.658 |  8.77 ${}^{+0.21}_{-0.21}$ |  5.88 ${}^{+3.73}_{-2.28}$ | 1.0 | $-$ | $-$ |
CEERS-1027-A | 7.819 |  7.94 ${}^{+0.05}_{-0.04}$ |  0.87 ${}^{+0.10}_{-0.08}$ | $-$ | 0.432 | $0.085\pm 0.018$ | Tang+23
CEERS-1027-B |  8.07 ${}^{+0.12}_{-0.14}$ |  7.90 ${}^{+0.28}_{-0.21}$ |  0.80 ${}^{+0.74}_{-0.30}$ | 8.6 | $-$ | $-$ |
GSDY-A | 7.957 |  8.75 ${}^{+0.21}_{-0.27}$ |  17.80 ${}^{+4.56}_{-5.02}$ | $-$ | $0.19$ | $>0.11$ |  RB+22 , this work
GSDY-B | 7.958 |  7.75 ${}^{+0.21}_{-0.28}$ |  2.73 ${}^{+1.02}_{-0.73}$ | 2.2 | $-$ | $-$ |
JADES-GS-A‡ | 7.982 |  7.82${}^{+0.11}_{-0.09}$ |  3.97${}^{+1.78}_{-0.88}$ | $-$ | 0.056 | $0.09\pm 0.01$ | Jones+23
JADES-GS-B‡ |  8.11${}^{+0.10}_{-0.08}$ |  8.33${}^{+0.14}_{-0.16}$ |  10.47${}^{+5.16}_{-3.46}$ | 1.5 | $-$ | $-$ |
EGSY8p68-A | 8.683 |  8.88 ${}^{+0.10}_{-0.18}$ |  7.62 ${}^{+1.87}_{-2.54}$ | $-$ | 1.59 | $<0.1$ |  Zitrin+2015 ,Witten+23
EGSY8p68-B† |  8.40${}^{+0.37}_{-0.27}$ |  8.34 ${}^{+0.28}_{-0.36}$ |  2.22 ${}^{+1.99}_{-1.25}$ | 0.5 | $-$ | $-$ |
EGSY8p68-C† |  8.74${}^{+0.50}_{-0.46}$ |  8.63 ${}^{+0.26}_{-0.40}$ |  4.26 ${}^{+3.49}_{-2.55}$ | 0.6 | $-$ | $-$ |
GN-z11-A | 10.603 |  9.1 ${}^{+0.3}_{-0.4}$ |  21 ${}^{+22}_{-10}$ | $-$ | 0.324 |  0.03 ${}^{+0.05}_{-0.02}$ | Bunker+23
GN-z11-B | 10.62 | * | * | 1.6 | $-$ | $-$ | Scholtz+23
GN-z11-C | 10.603 | * | * | 2.5 | $-$ | $-$ | Maiolino+23_PopIII
Table 1: The properties of Ly$\rm{\alpha}$-emitting galaxies. Physical
properties of all the systems studied in this paper. The columns are : (1)
spectroscopic (italic) or photometric redshift of the candidate, (2) stellar
mass, (3) Star formation rate averaged over at most the last 100 Myr, (4)
separation between the main component (A) and each companion, (5) luminosity
of observed Ly$\rm{\alpha}$ emission (6) escape fraction of Ly$\alpha$ photons
and (7) reference for the original spectroscopic confirmation and the
Ly$\alpha$ escape fraction measurement. * The companions of GN-z11 are
spectroscopically confirmed Scholtz+23 ; Maiolino+23_PopIII however given that
they are very UV-faint we cannot estimate their properties. † The companions
of both COSY and EGSY8p68 have recently been spectroscopically confirmed by
NIRSpec IFU observations Ubler+23 ;[Carniani et al. in prep.]. ‡ JADES-
GS+53.15682-27.76716 has been abbreviated to JADES-GS.

To spectroscopically confirm their identity as companions we exploit existing
XSHOOTER/VLT Vernet2011 , MOSFIRE/Keck MOSFIRE1 ; MOSFIRE2 , Near-Infrared
Spectrograph (NIRSpec) on-board JWST Jakobsen22 and NIRCam wide-field slitless
spectroscopy (WFSS) observations Rieke2005 of these galaxies. For three
systems in our sample we have no spectroscopic information on their companions
given the limitations of seeing at ground-based telescopes and the small
aperture size of JWST/NIRSpec observations. For the remaining six systems in
our sample we are able to spectroscopically confirm the companion galaxy as it
falls within the FoV of the observations of the main LAE. For two companions
in our sample we see tentative ($\sim 3\sigma$) evidence of Ly$\rm{\alpha}$
emission in Extended Figure 4 (one of which has recently been confirmed by
NIRSpec IFU observations Ubler+23 . For a further two companions we observe
the [OIII]5007 emission line at $>8\sigma$ (as seen in Extended Figure 5 with
fluxes reported in Extended Table 1), and NIRSpec IFU observations
spectroscopically confirm the companions of the final two systems
Maiolino+23_PopIII ; Scholtz+23 and [Carniani et al. in prep.]. We therefore
conclude that for all systems for which we have resolved spectroscopic
observations of the companion ($\sim 67\%$), we spectroscopically confirm its
nature as a physical companion (see the Methods for further details of the
spectrosocopic analysis).

To confirm that the presence of a close companion is the primary factor
governing the visibility of Ly$\rm{\alpha}$, we determine the fraction of
companions seen in a mass-matched sample of $z>7$ galaxies with high-
resolution spectroscopic data for which Ly$\rm{\alpha}$ is not detected
Jones+23 . We find that 43% of these galaxies have photometric-candidate
companions within 5′′ of the central galaxy which is consistent with the
companion fraction determined by a more comprehensive study [Puskás et al., in
prep]. The lower fraction of close companions among samples that are not
selected for Ly$\rm{\alpha}$ emission is evidence that the 100% rate of
companions for our sample of LAEs is atypical of $z>7$ galaxies.

To reinforce the observational evidence supporting the idea that ongoing
interactions drive an increase in the detectability of Ly$\rm{\alpha}$
emission during the epoch of reionisation, we explore comparable galaxy
mergers using the novel Azahar simulation suite (Martin-Alvarez et al., in
prep.). This simulation suite was performed before we obtained the NIRCam
data, but remarkably, we find many simulated galaxies that match the
photometry and the spatial geometry of our objects. Azahar is a cosmological,
high-resolution, zoom-in simulation which employs a magnetohydrodynamical
solver together with state-of-the-art cosmic ray feedback (see the pathfinder
Pandora project Martin-Alvarez+2023 and Methods). Most importantly for this
work, Azahar also features on-the-fly radiative transfer Rosdahl2015 ;
Rosdahl2018 ; Rosdahl2022 , capable of self-consistently reproducing
reionisation while fully modelling the ISM of galaxies (with a maximum spatial
resolution of $10$ pc), and crucially resolving the propagation and escape of
ionising radiation on the ISM scales Kimm2014 ; Garel2021 . We post-process
our simulations with the publicly available RASCAS code Michel-Dansac20 to
account for both the production and resonant scattering of Ly$\rm{\alpha}$
photons as well as scattering or absorption of Ly$\rm{\alpha}$ photons by dust
Laursen09b .

Figure 2: Comparison of Azahar to an observed galaxy merger. (Left panels)
NIRCam F150W (above) and HST F160W (below) imaging of the LAE EGSY8p68. The
NIRCam imaging reveals three components to the system that were previously
unresolved by HST. (Right panels) Analogue galaxy merger from the Azahar
simulation: a) large-scale view of the filaments encompassing the galaxy
merger (blue: HI density, grey-black: HII density, yellow-white: F150W
intensity); b) simulated NIRCam F150W observation of the Azahar merger; c)
fully resolved simulated observation in the NIRCam filters; and d) hydrogen
gas and ionising radiation properties (blue: HI density, grey-black: HII
density, yellow-white: F150W intensity, purple: LyC radiation energy density,
orange: HeII ionising radiation energy density). The appearance of the
observed system is very well reproduced by an ongoing merger of three
galaxies, with an extended escaping LyC radiation field.

Figure 3: The evolution of galaxy properties with an ongoing merger. (Rows
1-2) The time evolution of our simulated merger system at $z=8.1$ (close up
and large scale view), $7.3$ and $6.1$. First row: maps of HI density (blue),
HII density (grey-black), NIRCam F150W intensity (yellow-white), LyC radiation
energy density (purple) and HeII ionising radiation energy density (orange).
Second row: the RASCAS intrinsic Ly$\rm{\alpha}$ flux (blue) and scattered
Ly$\rm{\alpha}$ flux (orange). (Rows 3-5) The SFR for each of the three
galaxies and the final system (black line). Dot symbols show mergers with
companions (filled markers) and with other secondary systems (open markers);
the intrinsic Ly$\rm{\alpha}$ luminosity of the three galaxies and the entire
system; the fraction of escaped Ly$\rm{\alpha}$ luminosity filtered for pixels
with fluxes higher than a given limit (median (dark green curve), quartiles
(darker band), and min-max of the distribution across 12 lines-of-sight
(lighter band)). Distance between the main progenitor and its companions is
shown as well. The grey vertical lines in Rows 3-5 correspond to the redshifts
shown in Rows 1-2. The rightmost panels show key physical relations for the
observations (black) and the simulations (pink).

Due to a substantial overdensity of galaxies in our simulated volume, the main
progenitor undergoes repeated mergers with multiple other galaxies brought in
by the cosmic filaments, often involving several companions or mergers in
rapid succession as has been observed in Asada+23 . To highlight one such
merger occurring at $z\sim 7.3$, the four rightmost panels of Figure 2 show
different projections of Azahar. This particular interaction features three
merging galaxies that will constitute the main progenitor of the spiral galaxy
formed by $z\sim 1$. These are very good analogues to the EGSY8p68
observations shown on the left (modelling of the observations with Galfit in
Extended Figure 1 confirms the presence of three components), with very
similar individual galaxy sizes, mutual distances and merger configuration.
Specifically, the three simulated galaxies have stellar masses of
$M_{*,1}=2\cdot 10^{8}\,M_{\odot}$, $M_{*,2}=3\cdot 10^{8}\,M_{\odot}$, and
$M_{*,3}=8\cdot 10^{7}\,M_{\odot}$ at this redshift, which are comparable to
the stellar masses of the EGSY8p68 galaxies (see Table 1). Furthermore, the
simulated SFRs vary between $1-10\,\rm{M_{\odot}yr^{-1}}$ (shown in Figure 3)
and are consistent with the SFRs of the EGSY8p68 galaxies
($7.62\,\rm{M_{\odot}yr^{-1}},2.22\,\rm{M_{\odot}yr^{-1}},4.26\,\rm{M_{\odot}yr^{-1}}$).
We also consider the total Ly$\rm{\alpha}$ luminosity of the simulated system
and find that, while it varies, its average value is $\sim 10^{43}$ erg/s
(shown in Figure 3), in agreement with the value for EGSY8p68, reported in
Table 1. Finally we note that simulated volume hosts a substantial overdensity
of galaxies, which is consistent with the local environments of the observed
LAEs in our sample (as discussed earlier), including EGSY8p68 Leonova+22 . We
thus conclude that the simulated system matches all key observed photometric
and spectrosopic properties of EGSY8p68 (see also Methods).

The observations shown on the left clearly indicate the superior resolution
and sensitivity of JWST (top panel) over HST (bottom panel). The tri-component
nature of EGSY8p68 is entirely unresolved in existing HST observations, but
clearly identifiable in the F150W NIRCam imaging. Panel (a) shows the large-
scale view (150 kpc across) of the three filaments encompassing the merging
system, where large amounts of HI gas (blue) along the filaments are feeding
the star formation in these systems, resulting in significant NIRCam F150W
emission (yellow-white). This active star formation is driving ionised
hydrogen bubbles (grey) away from the filaments and into the low density
regions. Panel (b) shows the simulated JWST-like 150W observation (with dust
extinction modelled as an absorption screen along the line-of-sight), where we
select the line-of-sight to illustrate the resemblance with EGSY8p68. Note
that the simulated merging system is displayed at a slightly earlier stage of
the merger with respect to EGSY8p68, with our simulated galaxies approaching
the likely physical separation of the observed galaxies at $z\sim 7$.
Interestingly, the mock F150W emission reveals compact galactic cores
analogous to these JWST observations, with diffuse emission (blending with the
background) emerging from the extended, low density stellar discs. Panel (c)
shows a synthetic colour-composite observation using the JWST filters at the
full resolution of our simulation. While the two companion galaxies are more
diffuse, with stars actively forming in their discs, the main galaxy has a
much more compact core due to the preceding rapid growth through repeated
mergers. Panel (d) is a colour composite of various simulated properties
relevant for Ly$\rm{\alpha}$ detectability. The emission from LyC ionising
photons (purple) and HeII ionising photons (orange) is distributed on a scale
of a few (physical) kpc. Importantly, there is a clear separation of the
stellar emission and the HI gas during the merger event, with the ionising
radiation escaping from star forming regions.

To provide a quantitative confirmation and in-depth physical understanding of
this effect, we explore in Figure 3 the time evolution of the three merging
galaxies in detail. In the top row the colours encode the same quantities as
in panel (d) of Figure 2, while in the second row we show the intrinsic
Ly$\rm{\alpha}$ emission (blue) and resonantly scattered Ly$\rm{\alpha}$
emission (orange), produced by post-processing our simulations with RASCAS.
The first column shows a larger scale view of the main progenitor (galaxy 2)
and its approaching companions at $z\sim 8.1$. The second column shows a close
up views of the main progenitor at $z\sim 8.1$ undergoing a minor merger, with
a complex topology of neutral gas and channels through which Ly$\rm{\alpha}$
photons are escaping. The third column shows the ongoing merger of our
galaxies 1, 2 and 3 at $z\sim 7.3$ (with a different orientation with respect
to Figure 2), where bursty star formation drives ionised channels through the
ISM, with a significant amount of gas also tidally stripped from the galaxies.
The fourth column shows a post-merger view of the newly formed disc-dominated
galaxy at $z\sim 6.1$. Here, the HI is confined to the merger remnant galaxy,
and the radiation can only escape through the channels opened by collimated,
cosmic ray-driven bi-conical outflows. Focusing now on the Ly$\rm{\alpha}$
radiation, all three galaxies have significant intrinsic Ly$\rm{\alpha}$
emission due to their ongoing star formation. However, at this particular
viewing angle, due to absorption by dust, Ly$\rm{\alpha}$ scattered emission
is only present around merging galaxy 2 at $z\sim 8.1$ and around galaxies 1
and 3 at $z\sim 7.3$. At $z\sim 7.3$, the remaining emission, not absorbed by
dust, is very diffuse on large scales and hence not observable.

To understand what drives the observable Ly$\rm{\alpha}$ emission, in the
third row we show the SFR evolution for our three merging galaxies, together
with the SFR history of the merger remnant at $z\sim 6.1$. SFRs of all three
galaxies undergo repeated cycles of bursts, driven by numerous mergers
(‘major’ mergers [filled dots] and ‘minor’ mergers [empty dots]) and a high
SFR ‘plateau’ during the final merger episode from $z\sim 7$ to $6$. This is
mirrored in the evolution of the intrinsic Ly$\rm{\alpha}$ emission of each
galaxy as well as the total emission integrated across our three simulated
galaxies, as shown in the fourth row, where there is a clear correspondence
between the SFR peaks and peaks of intrinsic Ly$\rm{\alpha}$. Our simulations
hence demonstrate that high SFR triggered by gas-rich mergers results in
brighter intrinsic Ly$\rm{\alpha}$ emission, which enhances the probability of
these systems being detected.

To constrain this more robustly, we select an observable Ly$\rm{\alpha}$ flux
threshold of $10^{-18}\rm{erg}\,\rm{s}^{-1}\,\rm{cm}^{-2}$ consistent with our
observations, and compute the ratio of scattered to intrinsic Ly$\rm{\alpha}$
emission over the spatial extent of our mock observations of the galaxies.
This is shown in the fifth row, where the dark green curve denotes the median
of the ratio of scattered to intrinsic Ly$\rm{\alpha}$ flux and the shaded
bands (quartiles and minimum-maximum values) show its distribution computed
over 12 different lines-of-sight. As the fraction of escaping Ly$\rm{\alpha}$
emission has a number of high peaks we conclude that the Ly$\rm{\alpha}$
emission should be detectable for a number of the redshifts studied here.
Interestingly, during close galactic encounters (as shown by the distance
trajectories of three main galaxies shown in the same panel by coloured lines)
and mergers, significant gas tidal stripping and bursty star formation
feedback leads to the opening of more low-column density sight-lines, hence
facilitating the escape of Ly$\rm{\alpha}$ radiation. This effect can be
clearly seen when comparing the most important merger instances to the peaks
(high-tails) in the distribution of Ly$\rm{\alpha}$ escape fraction. Our
findings regarding higher intrinsic Ly$\rm{\alpha}$ emission and enhanced
Ly$\rm{\alpha}$ escape fraction in mergers are robust to the assumed dust
model (see Methods and Extended Figure 6). It is worth noting that inclusion
of AGN feedback in our simulations would only reinforce our findings, as
expected black hole fuelling during mergers would power AGN Costa_2022 .

The rightmost panels of Figure 3 show various physical relations for the
observations (black points) and the simulations (pink ‘violin’ symbols,
denoting the distribution of Ly$\rm{\alpha}$ escape fraction over 12 lines-of-
sight), using the same flux filter as above, demonstrating a very good
correspondence between our simulations and our observed LAEs. Interestingly,
both for observations and simulations we do not find any clear correlations
between the Ly$\rm{\alpha}$ escape fraction and any other galaxy properties
(distance, SFR, stellar mass), further corroborating our finding that
‘favourable’ lines-of-sights with evacuated neutral hydrogen channels lead to
directional Ly$\rm{\alpha}$ photon leakage.

In this paper, we introduce a new interpretation to explain the unexpected
detection of Ly$\rm{\alpha}$ in $z\geq 7$ galaxies in an epoch where the IGM
is mostly neutral and gas-rich, early galaxies are heavily ‘locally’
Ly$\rm{\alpha}$ damped. Combining the high-resolution and high-sensitivity of
JWST data with state-of-the-art radiative transfer on-the-fly
magnetohydrodynamics simulations, we demonstrate that three ingredients are
key to making Ly$\rm{\alpha}$ emission detectable from our sample of galaxies
deep in the epoch of reionisation: galactic mergers driving high intrinsic
Ly$\rm{\alpha}$ emission in the host galaxy; a ‘favourable’ line-of-sight
cleared of local neutral hydrogen in the host galaxy by tidal interactions
with companions and by star-formation feedback; a sufficiently large ionised
bubble facilitating the escape of Ly$\rm{\alpha}$ emission through the IGM.

Methods

Data

The emergence of JWST with its significant technical advancements over both
ground- and space-based telescopes, has the potential to reveal new hints as
to the driving forces behind the observed Ly$\rm{\alpha}$ emission discussed
in this paper. We therefore decided to analyse all spectroscopically-confirmed
LAEs at $z>7$, with JWST/NIRCam imaging. This search originally revealed
eleven such LAEs, however, further constraints on the SED of these galaxies
from NIRCam imaging reveals the Ly$\rm{\alpha}$ emission line detected in two
of these LAEs is in fact not Ly$\rm{\alpha}$ (discussed in more detail below).
Therefore, the sample becomes nine LAEs (seen in Table 1), eight of which have
companions that are identifiable in publicly available NIRCam imaging and
GN-z11 that has spectrosocpically confirmed companions that do not show a UV
continuum Maiolino+23_PopIII ; Scholtz+23 . These galaxies are found in the
GOODS-North and GOODS-South, EGS and COSMOS fields which have been observed
with NIRCam by FRESCO (PI: Oesch, ID: 1895) and JADES (PI: Eisenstein, ID:
1180), CEERS (PI: Finkelstein, ID: 1345) and PRIMER (PI: Dunlop, ID: 1837),
respectively.

The PRIMER survey covers $\sim 150\rm{arcmin}^{2}$ of the COSMOS field with
the F090W, F115W, F150W, F200W, F277W, F356W, F410M and F444W filters all at a
$5\sigma$ limiting depth of $m_{\rm AB}>28$. The CEERS survey took imaging of
$100\rm{arcmin}^{2}$ of the EGS field in the F115W, F150W, F200W, F277W,
F356W, F410M and F444W filters, reaching a $5\sigma$ limiting depth of $m_{\rm
AB}>29$ in the short-wavelength or $m_{\rm AB}>28.4$ in the long-wavelength
filters Finkelstein+22 . The June 2023 JADES data release surveys a $\sim 36$
arcmin2 area of the GOODS-S field using the F090W, F115W, F150W, F200W, F277W,
F335M, F356W, F410M and F444W, reaching $5\sigma$ limiting depths of $m_{\rm
AB}\sim 30$ Eisenstein+23 .

The FRESCO survey’s primary aim is to obtain NIRCam Long-Wavelength (LW) Grism
spectra over the F444W filter for galaxies across GOODS-S and GOODS-N.
However, the simultaneous imaging in the short-wavelength channel provides
imaging in both F182M and F210M filters, and direct imaging also obtained in
the F444W filter additionally provides us with a total of 3 filters for our
galaxies in GOODS-S/GOODS-N. FRESCO’s LW WFSS brings significant advantages as
the F444W filter covers the wavelength range of $3.9-5\mu$m, therefore
observing both [OIII]4959,5007 and H$\rm{\beta}$ at $z\sim 7-9$. These
emission lines ordinarily contaminate imaging in the F444W filter and hence
constraints on the fluxes of these emission lines allow us to reduce the
uncertainty in galaxy properties such as stellar mass, star-formation rate and
age. We use these constraints on the emission lines present in F444W to create
a mock F430M filter. Furthermore, when we fit the SED (discussed further
below) we check the fluxes of the [OIII]4959,5007 and H$\rm{\beta}$ emission
lines in the best-fit SED model and confirm that these are consistent with the
measured fluxes from the WFSS spectrum.

Data Reduction

Throughout our analysis we use the final reduced data products created by the
PRIMER team for the COSMOS field, the publicly available reduced data products
from the CEERS team for the EGS field, the publicly available reduced data
products from the JADES team for the deep HST region of GOODS-S and our own
reduction of the GOODS-S FRESCO imaging for regions outside of the publicly
available JADES imaging. In order to produce the GOODS-S images, we take all
available NIRCam imaging data of GOODS-S, available from the FRESCO survey,
and reduce them using version 1.8.5 of the JWST pipeline. We first download
the uncalibrated files from the MAST archive and follow the steps of the JWST
pipeline: (Stage 1) detector-level corrections and ramp fitting, (Stage 2)
instrument-level and observing-mode corrections producing fully calibrated
exposures, (Stage 3) producing the final mosaic. We take additional care after
Stage 1 to ensure the removal of horizontal and vertical striping that can be
present in the rate files.

We extract the photometry of our objects using SEXtractor SEXtractor on PSF-
matched images extracting all objects with more than 4 pixels (DETECT_MINAREA
4) detected at more than 1.5$\sigma$ (DETECT_THRESH and ANALYSIS_THRESH 1.5).
We used large deblending parameters to allow efficient separation of each
component (DEBLEND_NTHRESH 64 and DEBLEND_MINCOUNT 0.000001), however, the
small separation between the components of the EGSY8p68 and JADES-GS-z7-LA
systems makes the extraction of each component’s photometry impossible with
SEXtractor. For JADES-GS-z7-LA we employ the photometry of the LAE and its
companion reported in Saxena+23 while for EGSY8p68 we model the shape of each
component using Galfit Galfit assuming a Sersic profile and NIRCam PSFs,
simulated using WebbPSF. We first run Galfit on one of the NIRCam images where
all the components are clearly resolved (F115W), and we then fix the resultant
position, Sersic index, axis ratio and angle for each component when
extracting the photometry for the remaining images. Extended Figure 1 shows
the modelling of the components for this system.

Figure 1: Example of Galfit modelling for the EGSY8p68 system for which the
separation between each component is too small for the photometry to be
extracted by SEXtractor.

As discussed earlier, it is desirable to spectroscopically confirm as many
companion galaxies as possible. The use of the Mutli-Shutter Array with
NIRSpec to observe three of the systems (EGSY8p68, CEERS-1027 and JADES-
GS+53.15682-27.76716) means that, given the small shutter size, the companion
is not coincident with the shutter position. Instead, we make use of all
existing ground-based observations of our sample of LAEs, of which four of the
sample have been observed by MOSFIRE (z7-13433 - ID: N199, PI: Jung; EGSY8p68
- ID: C228M, PI: Zitrin; GSDY - ID: U069, PI: Treu; z7-GSD-3811 - ID: C182M,
PI: Scoville) and one with X-shooter (COSY - ID: 097.A-0043, PI: Ellis).

We reduce the spectroscopic data using the standard MOSFIRE data reduction
pipeline and EsoReflex. These pipelines perform wavelength callibration, sky
subtraction and flat fielding as well as further standard data reduction steps
in order to produce two-dimensional (2D) spectra. The resultant 2D spectra
span the length of the original slit used for the observations and have
spectral and spatial resolutions of $R\sim 3380$, 0.1798 ′′/px and $R\sim
8900$, 0.158 ′′/px for MOSFIRE and X-shooter respectively, but are limited by
the seeing of each observation which can be as poor as $\sim 0.9$′′.

Two of our sample are located in the GOODS-S field (z7-GSD-3811 and GSDY).
This field was the target of WFSS observations by the NIRCam Long-wavelength
(LW) Grism as part of the FRESCO observing program. FRESCO’s LW WFSS covers
the wavelength range of $3.9-5\mu$m using the F444W filter, therefore
observing both the [OIII]4959,5007 and H$\rm{\beta}$ emission lines for $z\sim
7-9$ galaxies, which are expected to be bright in high-redshift galaxies.
These lines have previously been observed in $z>7$ galaxies using the publicly
available FRESCO data Laporte+23 ; Oesch+23 . Moreover, the significantly
superior spatial resolution of NIRCam LW WFSS (60 milli-arcesconds) allows us
to resolve emission lines where MOSFIRE and X-shooter would fail to do so.

We reduced the Grism data following the steps described in Sun+22 including
flat fielding, background subtraction, 1/f noise subtraction and WCS
assignment. We also perform a careful astrometric analysis to avoid any
offsets between the LW direct imaging in F444W and the LW channel Grism
spectra in F444W. This allows us to extract the 2D Grism spectra associated
with the astrometric position of any source, these spectra are then stacked
and the 1D spectrum at the position of the source with an aperture of 3 pixels
is extracted. We also perform a continuum subtraction from the 1D spectrum to
remove any contaminant continuum and we focus on measuring [OIII]4959,5007 and
H$\rm{\beta}$ emission line fluxes.

Figure 2: Best SED-fits for all systems with strong Ly$\alpha$. The yellow
dots are the observed photometry, the grey line shows the best fit. The
physical parameters of the best fit are also indicated (see text for details).
Figure 3: Same as Extended Figure 2.

Redshift Determination

We initially take care to ensure that, for galaxies that only have
Ly$\rm{\alpha}$ emission detected in their spectra, the emission line detected
is indeed Ly$\rm{\alpha}$. There are initially five LAEs at $z>7$ in the
literature, imaged by NIRCam, for which Ly$\rm{\alpha}$ is the only observed
emission line (z7-GSD-3811, z8-19326, z7-13433, z7-20237 and GSDY). In order
to confirm that this emission line is Ly$\rm{\alpha}$, we use the SED-fitting
code Bagpipes Carnall2018 on the available NIRCam data to produce an improved
photometric redshift of each LAE. One of the key diagnostics in this fitting
becomes the bright [OIII]4959,5007 emission lines, expected from high redshift
objects, that fall into either the medium-band filter F410M (for $z\sim
6.8-7.6$)/F430M (for $z\sim 7.3-7.8$) or a lower flux consistent with
continuum emission in this filter but a boost in the F444W filter (for $z\sim
6.8-9$). This photometric-redshift fitting results in a redshift that is
consistent with the redshift of the emission lines observed being
Ly$\rm{\alpha}$ in all but two of these galaxies (z8-19326 and z7-20237). The
photometric redshift, constrained by a significant boost in F410M ($z\sim
7.1$) for z8-19326, becomes inconsistent with the emission line detected being
Ly$\rm{\alpha}$ and therefore this galaxy is not included in our sample. While
boosts in both F356W and F444W strongly indicate that z7-20237 is in fact at
$z\sim 6$. The original HST photometry reported in Jung+2022 also slightly
favoured a $z\sim 6$ solution making the observed emission line likely to be C
IV. The removal of these two galaxies as contaminants underlines the
challenges in determining galaxy redshifts with just one emission line and
wide-band HST filters pre-JWST. The JWST offers significant advancement in
this area given NIRSpec’s sensitivity allowing the detection of multiple
lines, but also given the frequency of programs that exploit the NIRCam
medium-band filters around $\sim 4\mu$m. All of the galaxies in our final
sample show a clear [OIII]4959,5007 excess in NIRCam imaging. We can therefore
be confident that the emission line detected is indeed Ly$\rm{\alpha}$.

Following this previous step, in order to confirm that all components of each
system are at a similar redshift, we again employ Bagpipes to estimate their
photometric redshifts. We then compare these with the spectroscopic redshift
of the main component. This fitting confirms that all the companion galaxies
preferentially have high photometric redshifts, all of which are consistent
with the spectroscopic redshift of the massive galaxy. In combination with the
prior of the companion being closely located to a confirmed high-redshift
galaxy, these become strong-photometric candidate companion galaxies. We also
exploit all available ground and space based spectroscopic observations that
cover the companions and use these to spectroscopically confirm the companion
galaxy where possible. Below we discuss the available redshift constraints on
our sample.

EGSY8p68, CEERS-1027 and JADES-GS+53.15682-27.76716 constitute the sub-sample
of LAEs that have photometric candidate companions with no spectroscopic
confirmation. This lack of confirmation is due to a combination of factors.
The observations of CEERS-1027 and JADES-GS+53.15682-27.76716 were made with
the NIRSpec MSA and the positioning of the shutter misses the companion, and
as such there is no ability to place any spectroscopic constraints on these
companions. EGSY8p68 has been observed by both the NIRSpec MSA and the ground-
based telescope MOSFIRE/Keck. The MOSFIRE observations of the system cover the
companion galaxies, however due to the seeing of the observations ($\sim
0.7$′′) and the small separation between the components of the system ($\sim
0.1$′′) resolving the components was not possible. Follow-up observations with
the NIRSpec MSA reveal EGSY8p68 is likely an AGN given the presence of high-
ionisation emission lines and a significant broadening of the H$\rm{\beta}$
emission line Larson23 . While one of the companion galaxies lies in the
shutter of this observation, the available spatial resolution and strength of
the emission lines from EGSY8p68 makes it challenging to disentangle the
emission from each component. However, the reported NIRSpec MSA flux is seven
times fainter than that observed in the MOSFIRE spectrum Zitrin+2015 . Given
the MSA shutter size is significantly smaller than the MOSFIRE slit, one
solution to this discrepancy in flux is that some of the Ly$\rm{\alpha}$
emission is extended outside of the MSA slit. We note that the component
EGSY8p68-C sits outside of the MSA slit position and as such this component
may additionally host Ly$\rm{\alpha}$ emission at the same redshift as the
main component. Moreover, Larson23 claim that the system is consistent with
being involved in a major merger and recent NIRSpec IFU observations of
EGSY8p68 spectroscopically confirm they are physical companions [Carniani et
al. in prep.]. However, given these results are not yet published and the data
is not yet public we continue our analysis of the redshift constraints
assuming we do not have this spectroscopic confirmation.

Despite the lack of spectroscopic constraints on this sub-sample, the
similarities in the SEDs of the main and companion galaxies are distinct. The
galaxies in each system show similar colours, Lyman-breaks that are consistent
and an emission-line boost, driven by [OIII]4959,5007 and H$\rm{\beta}$
emission, in the same filters, as can be seen in Extended Figure 2 and 3. This
results in a photometric redshift for each of the companions that clearly
favours a $z>7$ solution, and given the emission line feature in the F444W
filter, the photometric redshift is further constrained to $z=7.6-9$. While
the redshift of these components are very confidently constrained to within
this $\Delta z=1.4$, further constraining their redshift is challenging
without spectroscopy. However, we make use of the UV luminosity function from
Bouwens+15 in order to estimate the expected number of galaxies within the
volume that the [OIII]4959,5007 emission redshift constraint constrains the
companion galaxies to. We note that the photometric redshift from BAGPIPES
(reported in Table 1) is much more tightly constrained than that provided by
the [OIII]4959,5007 boost alone, however we use this wider redshift constraint
($\Delta z=1.4$) to provide an upper limit on the expected number of galaxies.
Given that we have searched for companions in a 3′′x3′′ region, we use this as
the area for this estimate and the [OIII]4959,5007 redshift constraints to
produce a volume. We then integrate the $z=7$ or $z=8$ (dependent on the
spectroscopic redshift of the main component) UV luminosity function down to
the 5$\sigma$ magnitude limit of the NIRCam images. We estimate that the
expected number of galaxies in this field-of-view that are consistent with
H$\rm{\beta}$ and [OIII]4959,5007 producing the excess F444W flux and with
observed UV magnitude is $0.09^{+0.16}_{-0.04}$ for JADES-
GS+53.15682-27.76716, $0.007^{+0.009}_{-0.002}$ for CEERS-1027 and
$0.003^{+0.006}_{-0.001}$ for EGSY8p68. It is therefore very unlikely that
another galaxy that is not associated with the spectroscopically confirmed LAE
would be present in this volume.

JADES-GS-z7-LA is an extremely high EW LAE (400 Å) discovered in JADES NIRSpec
observations of galaxies in the GOODS-S field Saxena+23 . The presence of a
photometric candidate companion galaxy to this LAE has already been reported
Saxena+23 , but the companion lies outside of the NIRSpec MSA shutter, and
hence is not spectroscopically confirmed. We perform the same analysis as
above, noting that the [OIII]4959,5007 emission is in the F410M filter,
limiting the redshift to between $z=6.8-7.6$, and find the expected number of
galaxies to be $0.13^{+0.14}_{-0.05}$. Therefore, once again, it is unlikely
that the observed companion is at a redshift that makes it unrelated to the
spectroscopically confirmed LAE. Moreover, we note the observed excess in the
F115W filter that may be driven by Ly$\rm{\alpha}$ emission in both the main
and companion galaxy Saxena+23 , supporting the conclusion that these two
galaxies are at the same redshift.

COSY and z7-13433 have companions that show excess fluxes in the F410M filter
driven by [OIII]4959,5007 emission. SED-fitting of their companions strongly
prefers a $z>7$ solution, and the presence of [OIII]4959,5007 emission
confines the redshift to $z=6.8-7.6$. We again perform the same analysis as
above, estimating the expected number of galaxies in the FoV. The expected
number of galaxies is $0.03^{+0.03}_{-0.01}$ for COSY and
$0.04^{+0.03}_{-0.01}$ for z7-13433 and thus we conclude it is very likely
that the central and companion galaxies are associated with each other.

Moreover, the companions of both COSY and z7-13433 are within the slits used
for the observations with X-shooter and MOSFIRE, respectively. The two
components of each system are shown in Extended Figure 3, where we can
identify both the positive (white) and negative (black) traces of the objects,
caused by the ABBA nodding pattern of the observations. We find that, for
z7-13433, two emission lines are offset by $\sim 3$ pixels, which is
consistent with the $\sim 0.5$′′ offset between the two components in the
slit. The Ly$\rm{\alpha}$ emission that is coincident with the position of the
companion is detected at $2.8\sigma$ and corresponds to $z=7.479$, while the
Ly$\rm{\alpha}$ flux associated with the main galaxy is at $4\sigma$
corresponding to $z=7.482$. Therefore, these two components are offset by
$\sim 125$ km/s. In the case of COSY, we expect a similar spatial offset
between the two components, but the $\sim 0.7$′′ seeing during the
observations makes distinguishing between the two components very challenging.
However, there is a second, previously unidentified, component to the
Ly$\rm{\alpha}$ emission of COSY at $\sim 0.9898\mu$m. We attribute this
$2.7\sigma$ emission line to COSY-B and note a velocity offset of $\sim 280$
km/s between COSY-A and COSY-B. While these Ly$\rm{\alpha}$ detections are
clearly tentative, given they are coincident with the expected position in the
2D spectra of strong-photometric candidate galaxies and given their proximity
to confirmed LAEs this boosts their likelihood of being a true detection.

Finally, we note that recent NIRSpec IFU observations of COSY
spectroscopically confirm its companion galaxy Ubler+23 . However, as with
EGSY8p68, given these results are not yet published and the data is not yet
public we continue our analysis without this spectroscopic information.

Figure 4: The X-shooter (above) and MOSFIRE (below) Gaussian-smoothed 2D
spectra of COSY and z7-13433, respectively. These cover the wavelength range
of the previously spectroscopically confirmed Ly$\rm{\alpha}$ emission of the
system. White circular apertures indicate the proposed two components of the
Ly$\rm{\alpha}$ emission that are coincident with the expected positions of
the main and companion galaxies in the slit. The positive trace of the
emission is indicated by white pixels, the negative trace by black pixels,
this effect of positive and negative traces is caused due to the ABBA nodding
procedure employed by both instruments.

z7-GSD-3811 and GSDY are both in the FoV of the FRESCO NIRCam WFSS survey.
Their final 2D WFSS spectra, shown in Extended Figure 5 show [OIII]4959,5007
emission lines for both z7-GSD-3811, GSDY and their companions. For
z7-GSD-3811 both components of the [OIII]4959,5007 emission are present and
there is a $\sim 3\sigma$, faint detection of H$\rm{\beta}$. Moreover,
[OIII]4959,5007 emission is also detected in the companion galaxy. This
emission is offset from the central galaxy by $170\pm 70$ km/s. The 2D
spectrum of GSDY shows a clear detection of [OIII]5007 in both the central and
companion galaxies, and there is a very faint indication of [OIII]4959 and
H$\rm{\beta}$ in the companion galaxy, but at a less than 3$\sigma$ confidence
for both. The emission detected in the central and companion galaxy are offset
by just $\sim 26$ km/s, but given the low spectral resolution of the NIRCam
WFSS, this is significantly smaller than the $\sim 70$ km/s uncertainty on
this measurement.

We discuss in the main text the use of H$\rm{\beta}$ to estimate the intrinsic
Ly$\rm{\alpha}$ flux and hence the escape fraction of Ly$\rm{\alpha}$ photons,
however, it can also be used as a probe of the instantaneous SFR. We assume a
H$\alpha$ to H$\rm{\beta}$ ratio of 2.85 and Case B recombination at $T_{\rm
e}=10,000$ K and $N_{\rm{e}}=10^{4}\ \rm{cm^{-3}}$ and following Kennicutt+98
we estimate the instantaneous SFR which is reported in Extended Table 1. Given
the lack of constraints on the redenning of these galaxies, we do not dust-
correct the H$\rm{\beta}$ flux and as such these measured instantaneous SFRs
are lower bounds.

The observation of multiple, spatially resolved components to each emission
line is taken as spectroscopic confirmation of the companion galaxies.
Moreover, the velocity offset observed in all of these galaxies is indicative
of either a line-of-sight separation, or more likely, a difference in the
line-of-sight velocities of the two objects as they interact with each other.
We therefore consider this as further evidence that the systems are indeed
interacting, as opposed to being two components of the same stable system.

Figure 5: NIRCam WFSS Grism spectra of z7-GSD-3811 (above) and GSDY (below). Within each panel, the continuum subtracted 2D spectrum (above) and 1D spectrum (below) of the central galaxy are shown. The upper left sub-panel shows the F444W image of the system where two components can be identified. The horizontal dashed lines indicate the position of the central galaxy in both the image and 2D spectrum. The three dashed lines in the 1D spectrum denote the expected positions of the [OIII]4959,5007 doublet (central and right dashed lines) and H$\rm{\beta}$ (left dashed line) emission lines given the object’s spectroscopic redshift, while the grey shaded region denotes the one-sigma noise level. ID | $z$ | $\rm{[OIII]_{5007}}$ | $\rm{[OIII]_{4959}}$ |  H$\rm{\beta}$ |  SFR${}_{\rm{inst}}\rm{[M_{\odot}/yr]}$
---|---|---|---|---|---
z7-GSD-3811-A | $7.663$ | $8.3\pm 0.4$ | $2.7\pm 0.4$ | $1.0\pm 0.3$ | $16.5\pm 4.9$
z7-GSD-3811-B | $7.658$ | $4.8\pm 0.4$ | $1.5\pm 0.3$ | $<0.5$ | $<8.2$
GSDY-A | $7.956$ | $5.8\pm 0.7$ | $1.0\pm 0.4$ | $<0.5$ | $<9.0$
GSDY-B | $7.957$ | $3.1\pm 0.6$ | $1.5\pm 0.6$ | $0.8\pm 0.3$ | $14.4\pm 5.4$
Table 1: Properties inferred from NIRCam Grism spectroscopy. The observed
redshift and fluxes of emission lines (in units of $10^{-18}$ erg/s/cm2)
detected in the NIRCam/WFSS spectra. The instantaneous star-formation rate
(SFR) is not dust-corrected given the lack of constraints on dust in these
galaxies.

GN-z11 was recently observed with the NIRSpec IFU which has revealed the
presence of three regions emitting either HeII (GN-z11-C) Maiolino+23_PopIII
or Ly$\rm{\alpha}$ emission (GN-z11-B and a more tentative candidate)
Scholtz+23 . While none of these regions show evidence of a UV continuum in
deep NIRCam imaging, a tentative indication of CIV]$\lambda\lambda$1548,1551
emission in GN-z11-B and analysis of the emission in GN-z11-C
Maiolino+23_PopIII indicate they are indeed being driven by a UV-faint stellar
population in these regions. As such, we conclude that GN-z11 does have
spectroscopically-confirmed companion galaxies. Moreover, the presence of
multiple LAEs in the local vicinity of GN-z11 suggests that peculiar velocity
is not playing a vital role in the escape of Ly$\rm{\alpha}$ through the
neutral IGM (see Scholtz+23 for a detailed analysis of the Ly$\rm{\alpha}$
emission present in this system). Moreover, the density of objects in this
field makes GN-z11 a likely protocluster core Scholtz+23 .

SED fitting

We then use Bagpipes, with the redshift fixed to that of the spectroscopic
redshift of the system, using different SFHs (constant, delayed, burst and
burst+constant) to fit the SED of all central and companion galaxies, as seen
in Extended Figure 2 and 2. The best fit model is then obtained by taking the
SFH that leads to the smallest Bayesian Information Criterion (BIC) as
described in Laporte21 . We then report the galaxy properties returned from
this method in Table 1.

Close companion fraction of non-LAEs

In order to ascertain the companion fraction of a mass-matched sample of $z>7$
galaxies, we take 30 galaxies with stellar masses from
$7.4<\rm{log(M}_{*}[$M${}_{\odot}])<9.3$ from Laporte+22 ; Tang+23 ;
Harikane+22 ; Bouwens+22 . We find that 47% of these galaxies have
photometric-candidate companions within 5′′ of the central galaxy. However,
many of these galaxies have not been spectroscopically followed-up and as
such, we do not have constraints on their Ly$\rm{\alpha}$ emission.

Unfortunately, examples of spectroscopically confirmed $z>7$ non-
Ly$\rm{\alpha}$ emitting galaxies that have been observed by high-resolution
spectrographs are rare in the literature. As such it is challenging to probe
the companion fraction for known non-LAE galaxies. Moreover, the challenges of
slit/aperture spectroscopy mean that it is incredibly rare to have
spectroscopic information on the local environment of such galaxies and hence,
while a galaxy may be confirmed as non-LAE, there is no information regarding
the Ly$\rm{\alpha}$ emission of any companion that may or may not be present.

The recent JADES data release of NIRSpec and NIRCam observations in GOODS-S
includes seven $z>7$ galaxies, observed using the NIRSpec high-resolution
G140M grating, that show no Ly$\rm{\alpha}$ emission Jones+23 . This does not
provide any Ly$\rm{\alpha}$ information on any would-be companion galaxies,
however, the companion fraction for this sample, $\sim 43\%$, is once again
consistent with both our larger sample, and that of Puskás et al. (in prep.).
We therefore conclude that the $100\%$ companion fraction of our LAE sample is
clearly atypical compared to the companion fractions of samples not selected
for Ly$\rm{\alpha}$ emission.

Close companions are necessary but not sufficient for Ly$\alpha$ emission

We note the recently reported $z=9.3$ merging system Boyett+23 with an absence
of detected Ly$\rm{\alpha}$ emission. The reported specific-star-formation
rate of this galaxy (sSFR $\sim-8$) is consistent with the high sSFR seen in
our sample of merging LAEs, and therefore, one may naively posit that this is
a contradiction to our results. We argue that non-detection of Ly$\rm{\alpha}$
emission from a merging system is entirely reasonable and in fact our
simulation modelling predicts this. While we see significant boosts in the SFR
and hence intrinsic Ly$\rm{\alpha}$ emission from merging systems, the escape
of Ly$\rm{\alpha}$ emission is only possible when the escape fraction of
Ly$\rm{\alpha}$ emission out of both the host galaxy and the surrounding IGM
is non-zero. We explore the effect of viewing angle on the observed
Ly$\rm{\alpha}$ emission escaping our simulated merging systems and find that
while the majority of viewing angles facilitate the escape of Ly$\rm{\alpha}$,
several viewing angles exist for which the only Ly$\rm{\alpha}$ emission
escaping the galaxy is diffuse and is therefore unobservable. Moreover,
without the presence of a large ionised bubble, the neutral IGM will not
facilitate the escape and observation of Ly$\rm{\alpha}$ emission. Ultimately
we conclude that close companions are necessary but not sufficient for the
observation of Ly$\alpha$ from galaxies deep in the epoch of reionisation. A
combination of a large-scale ionised bubble and a preferable line-of-sight,
stripped of neutral hydrogen by the interaction with the companion, are also
required.

Azahar simulations

Figure 6: Dust opacities superimposed on synthetic Ly$\rm{\alpha}$ images at
$z=7.3$. The top row shows the intrinsic Ly$\rm{\alpha}$ emission, the middle
row shows the scattered Ly$\rm{\alpha}$ emission generated with a default dust
model, and the bottom row shows the scattered Ly$\rm{\alpha}$ emission with
practically no dust (dust opacity reduced by a factor of $10^{6}$). The three
different columns show the galaxy from three different directions. Red and
orange iso-contours correspond to a dust optical depth of 0.2 at the
Ly$\rm{\alpha}$ wavelength and H$\alpha$ wavelength, correspondingly. Note
that the dust does not act as a screen for the Ly$\rm{\alpha}$ emission
because of the resonant nature of Ly$\rm{\alpha}$ scattering.

The new Azahar simulations are a suite of multiple models spanning various
combinations of canonical hydrodynamics, magnetic fields, radiative transfer,
and cosmic rays physics with the aim of understanding their effects on galaxy
formation as well as their complex interplay. The simulations are generated
using the magneto-hydrodynamical code ramses Teyssier2002 , which employs a
constrained transport method for divergence-less evolution of the magnetic
field Teyssier2006 . The main target of study for Azahar is a massive spiral
galaxy with $M_{\text{halo}}\,(z=1)\sim 2\cdot 10^{12}\,M_{\odot}$ in a
relatively large zoom-in region, approximately $8$ cMpc across along its
largest axis. Azahar has a maximum spatial resolution in cells with a full
cell-width of $\Delta x\sim 20\,\text{pc}$ (or equivalently, an approximate
cell half-size or radius of $10\,\text{pc}$), and refinement is triggered
whenever its size is larger than a quarter of its Jeans length, or it contains
a total mass larger than $8\,m_{\text{DM}}$, where $m_{\text{DM}}\sim 4.5\cdot
10^{5}M_{\odot}$ is the mass of dark matter particles in the zoom region. The
stellar mass particle is $m_{*}\sim 4\cdot 10^{4}M_{\odot}$. Azahar follows
the set of physics presented by the pathfinder Pandora Martin-Alvarez+2023 .
We provide here a brief summary, and refer the reader to that reference and
Martin-Alvarez et al. (in prep.) for further details.

In this work, we investigate one of the most complete simulations in the
Azahar suite, the RTnsCRiMHD model. In this manuscript, we refer to the
RTnsCRiMHD simulation simply as Azahar. Radiative cooling is modelled both
above and below $10^{4}\text{K}$ Ferland1998 ; Rosen1995 . The model adopts a
magneto-thermo-turbulent prescription for star formation Kimm2017 ; Martin-
Alvarez2020 , mechanical supernova (SN) feedback Kimm2014 and astrophysically-
seeded magnetic fields through magnetised SN feedback Martin-Alvarez2021 .
This feedback injects 1% of the SN energy as magnetic energy, and intends to
reproduce the approximate magnetisation of SN remnants. This particular
simulation of Azahar also includes cosmic rays modelled as an energy density
allowed to anisotropically diffuse, evolved with an implicit solver Dubois2016
; Dubois2019 . In Azahar, cosmic rays are exclusively sourced by SN feedback,
with each event injecting 10% of their total energy as cosmic rays. We assume
a constant diffusion coefficient for cosmic rays of $\kappa_{\text{CR}}=3\cdot
10^{28}\,\text{cm}^{2}\,\text{s}^{-1}$, and do not account for cosmic ray
streaming in this model. This model also includes on-the-fly radiative
transfer Rosdahl2015 , with a configuration similar to that of the SPHINX
simulations Rosdahl2018 , featuring three energy bins for radiation spanning
the ionisation energy intervals from $13.6$ eV to $24.59$ eV (HI ionisation),
$24.59$ eV to $54.42$ eV (HeI ionisation), and above $54.42$ eV (HeII
ionisation). Finally, recent work has shown that when expanding simulation
models to account for cosmic ray feedback physics at comparable resolutions,
the escape fractions of LyC photons from galaxies is lower than in their
absence Farcy2022 .

Therefore, Azahar features a realistic (yet computationally taxing) ISM model
that considerably approaches the resolution required to converge in the
propagation and escape of ionising photons from galaxies Kimm2014 . We note
that, while close, our resolution still falls short from that regime and that
even more sophisticated ISM models Katz2022 may be important for a complete
understanding of photon propagation in the ISM. Opportunely, a considerable
part of our results relies on gas being ejected from galaxies during merger
events, which implies that our estimate of LAE detectability during these
events will be more resilient to these caveats.

Simulated ionised bubble evolution in the neutral IGM

In the high resolution patch of the Universe probed by our simulation
($\lesssim 8$ Mpc on a side), centred on the main progenitor of our $z\sim 1$
galaxy, the first ionised bubbles emerge at $z\sim 20$. By $z\sim 15$ several
ionised bubbles exist that are a few (physical) kpc in radius, and rapidly
begin merging as redshift approaches $z\sim 10$. This drastically increases
the mean free path of ionising photons, with the coalesced bubble reaching
scales of $100$ kpc. The resulting main bubble continues to grow, reaching a
radius $\sim 0.5$ Mpc at $z\sim 7.3$.

For intrinsically bright LAEs, as studied here, a $\lesssim 0.5$ Mpc local
ionised bubble may be sufficient for these sources to be detectable Hayes+23 .
We further note that due to ongoing mergers our simulated galaxies have
considerable relative peculiar velocities of up to $230$ km s-1. Sufficiently
large velocities relative to the intervening neutral IGM gas may reduce
damping wing suppression for particular lines-of-sight, hence requiring
smaller local ionised bubbles to facilitate the detection of Ly$\rm{\alpha}$.
Our simulation also does not consider star formation outside of the high-
resolution zoom-in region. Hence, our simulated ionised bubbles could be even
larger in size, e.g. due to the presence of a neighbouring, large-scale
overdensity or large-scale clustering Weinberger2019 on spatial scales beyond
our zoom-in region.

Nevertheless, knowing from our observations that the LAEs sit in sufficiently
large ionised bubbles, here we primarily focus on the probability of
Ly$\rm{\alpha}$ photons escaping the host galaxy and its intermediate
surroundings. We find that a large amount of gas remains neutral within the
local ionised bubble, actively feeding the galaxies along the cosmic web.

Galaxy selection and measurements in the simulations

In order to select galaxies in our simulation, we employ the halomaker
software Tweed2009 to detect and characterise dark matter halos. We identify
the three progenitor galaxies of interest (as well as the galaxy merging with
the main progenitor at $z\sim 8.1$) and follow them through time by tracking
their innermost stellar particles. Their centres are determined using a
shrinking spheres algorithm applied to their stellar component Power2003 , and
they are assigned their corresponding halo as obtained by halomaker. In order
to select the system for study, we broadly reviewed the evolution of all
galaxies with stellar masses $M_{*}>10^{7}M_{\odot}$ in the redshift interval
$z\in[9.0,6.0]$. The most promising candidate, the main progenitor of the main
Azahar galaxy was selected for further investigation.

In order to assign measurements to individual galaxies, we measure values
within their galactic region, defined by the radius
$r_{\text{gal}}<0.2\;r_{\text{rvir}}$. During the merging stages, we employ
$r=\text{min}[r_{\text{gal}},0.45D_{ij}]$, where $D_{ij}$ is the distance
between the $i$ and $j$ progenitors, down to a minimum distance of $1.5$ kpc.

We have briefly reviewed the observability of lower mass pairs within the
simulated domain. While these present a similar behaviour during mergers to
that of our main studied system, their observability and that of other
galaxies with similar masses remains low. This is due to their low stellar
masses generating low luminosities. Their low stellar masses also make them
more vulnerable to disruption during powerful star formation bursts, which
increases their escape fractions Rosdahl2022 . Despite this, most isolated
systems present quiet star formation histories and in the absence of mergers,
have low observabilities throughout their evolution.

RASCAS post-processing

We post-process the simulation with the publicly available, massively parallel
code RASCAS Michel-Dansac20 , for modelling the Ly$\rm{\alpha}$ emission and
resonant scattering in our simulations. RASCAS accounts for two sources for
the Ly$\rm{\alpha}$ emission, recombination and collisional excitation. For
recombination, RASCAS adopts the case B recombination coefficient from
Hui&Gnedin97 , and the fraction of recombinations producing Ly$\rm{\alpha}$
photons from Cantalupo08 . For collisional excitation, RASCAS uses the fitting
function for the collisional excitation rate from level 1s to 2p from Goerdt10
. We cast $N_{\rm MC}=10^{6}$ Monte Carlo photon packets to sample the real
Ly$\rm{\alpha}$ photon distributions, from recombination and collisional
excitation, respectively. We sample $N_{\rm MC}=10^{7}$ photon packets for the
images along the LOS in Extended Figure 4.

After each scattering event, the Ly$\rm{\alpha}$ photon changes its frequency
and direction according to a phase function as implemented in RASCAS. RASCAS
adopts the phase function in Hamilton40 ; Dijkstra&Loeb08 for the scattering
of Ly$\rm{\alpha}$ photons around line centre and Rayleigh scattering for
Ly$\rm{\alpha}$ photons in the line wing. At high H i column density,
Ly$\rm{\alpha}$ photons will scatter many times locally until they shift in
frequency large enough so that they can have a long mean free path. To reduce
the associated computation cost, RASCAS adopts a core-skipping mechanism
Smith15 to transit the photons to line wings while avoiding local scattering
in space. RASCAS also implements the recoil effect and the transition due to
deuterium with an abundance of D/H = $3\times 10^{-5}$. The dust distribution
is modelled according to the dust model described in Laursen09b . Dust can
either scatter or absorb Ly$\rm{\alpha}$ photons. The probability of
scattering is given by the dust albedo $a_{\rm dust}=0.32$ following
Li&Draine01 . The dust scattering with the Henyey-Greenstein phase function
Henyey&Greenstein41 and the asymmetry parameter is set to $g=0.73$ following
Li&Draine01 . We generate synthetic images and spectra with a peeling
algorithm described in Yusef-Zadeh84 ; Wood&Reynold99 ; Costa22 , along 12
lines-of-sight uniformly sampled using the healpix algorithm Gorski05 .

Finally, we note that the dust distribution has a large effect on the
Ly$\rm{\alpha}$ radiative transfer as well as the [OIII]4959,5007 and
H$\rm{\beta}$ emission that is used to infer the intrinsic Ly$\rm{\alpha}$
emission from observations. In Extended Figure 6, we show how reducing the
amount of dust changes the observed Ly$\rm{\alpha}$ images. We see the dust is
able to completely mask the Ly$\rm{\alpha}$ emission of some individual
galaxies as resonant scattering of H i increases the probability of
Ly$\rm{\alpha}$ photons encountering dust grains. The dust can suppress the
H$\rm{\alpha}$ emission by up to 20% around the center of the three merging
galaxies, if we assume intrinsic Ly$\rm{\alpha}$ can be converted directly to
intrinsic H$\rm{\alpha}$ emission. We therefore conclude that inclusion of
dust modelling, as done here, is fundamental for understanding observed
Ly$\rm{\alpha}$ emission. However, our results regarding the boosted intrinsic
Ly$\rm{\alpha}$ emission in star formation bursts and enhanced Ly$\rm{\alpha}$
escape fraction in mergers, due to the channels cleared of local neutral
hydrogen are robust to the assumed dust model.

We further consider the Ly$\rm{\alpha}$ profiles escaping along the line-of-
sight shown on the upper panel of Extended Figure 4 at $z=7.3$ after applying
a reasonable IGM damping wing from Keating23 . We note that the shape of the
Ly$\rm{\alpha}$ profile is very complex and sensitive to both the LOS
Blaizot+23 and IGM attenuation Witten+23 . As such, further analysis of this
is needed to constrain the expected Ly$\rm{\alpha}$ profiles from simulations
requiring a larger simulated galaxy sample with careful IGM attenuation
modelling as well as a larger observational sample to compare to, which is
beyond the scope of this work. However, as an immediate consistency test, we
take the Ly$\rm{\alpha}$ profile from our simulated system at $z=7.3$ after
IGM attenuation Keating23 and compare the velocity offset and FWHM to that
reported in our observational comparison, EGSY8p68. We find that the observed
Ly$\rm{\alpha}$ profile Larson23 is well matched with the simulated profile’s
velocity offset of $\sim 200$ km/s and FWHM of $\sim 200$ km/s, and shows a
clear asymmetric line shape as observed.

Data availability

The JWST data used in this analysis is publicly available from the STScI MAST
Archive.

Code availability

The WebbPSF tool can be found at https://www.stsci.edu/jwst/science-
planning/proposal-planning-toolbox/psf-simulation-tool. The standard MOSFIRE
data reduction pipeline can be found at https://keck-
datareductionpipelines.github.io/MosfireDRP/ and EsoReflex can be found at
https://www.eso.org/sci/software/esoreflex/.

Acknowledgments

The authors would like to acknowledge the work of the PRIMER core team in
obtaining and reducing the NIRCam data for the COSMOS field used in this work
(PI: Dunlop, ID: 1837). The authors would also like to acknowledge the work of
the CEERS team in obtaining and reducing the NIRCam data of the EGS field used
in this work (PI: Finkelstein, ID: 1345). The authors would like to
acknowledge the FRESCO team’s work in obtaining observations of the GOODS-S
and GOODS-N fields (PI: Oesch, ID: 1895). The authors would also like to thank
Joki Rosdahl for their support with the generation of radiative transfer
RAMSES simulations, and Thibault Garel for their support with the usage of
RASCAS. The authors also thank Mengtao Tang, Daniel Stark and Hannah Übler for
providing additional information on the properties of some of our sample.

Support for this work was provided by NASA through grant JWST-GO-01837 awarded
by the Space Telescope Science Institute, which is operated by the Association
of Universities for Research in Astronomy, Inc., under NASA contract NAS
5-26555. This research has made use of the Keck Observatory Archive (KOA),
which is operated by the W. M. Keck Observatory and the NASA Exoplanet Science
Institute (NExScI), under contract with the National Aeronautics and Space
Administration. Based on observations collected at the European Southern
Observatory. This work used the DiRAC@Durham facility managed by the Institute
for Computational Cosmology on behalf of the STFC DiRAC HPC Facility
(www.dirac.ac.uk). The equipment was funded by BEIS capital funding via STFC
capital grants ST/P002293/1, ST/R002371/1 and ST/S002502/1, Durham University
and STFC operations grant ST/R000832/1. DiRAC is part of the National
e-Infrastructure. CW thanks the Science and Technology Facilities Council
(STFC) for a PhD studentship, funded by UKRI grant 2602262. NL acknowledges
support from the Kavli foundation. DS, MGH and JSD acknowledge STFC support.
PS acknowledges INAF Mini Grant 2022 “The evolution of passive galaxies
through cosmic time”. RSE acknowledges financial support from ERC Advanced
Grant FP7/669253. PGP-G acknowledges support from Spanish Ministerio de
Ciencia e Innovación MCIN/AEI/10.13039/501100011033 through grant
PGC2018-093499-B-I00. DP acknowledges support by the Huo Family Foundation
through a P.C. Ho PhD Studentship. RM, WB and WM acknowledge support by the
Science and Technology Facilities Council (STFC) and ERC Advanced Grant 695671
”QUENCH”. RM also acknowledges funding from a research professorship from the
Royal Society. This research was supported in part by the National Science
Foundation under Grant No. NSF PHY-1748958.

Author Contributions

CW reduced and analysed NIRCam imaging and WFSS, MOSFIRE and X-shooter data.
NL extracted the photometry of each candidate and performed the SED-fitting
analysis. SMA developed the Azahar simulations, performed their basic analysis
and extracted the Lyman-$\alpha$ luminosity for all the merging systems. YY
ran the RASCAS simulations and showed the influence of line of sights. DS and
MGH coordinated the simulations part of this paper. CW, NL, SMA, DS, YY and
MGH wrote the paper, and developed the main interpretation of the results. RM,
GRB, RSE, WM, WB, DP, CS and HK were key in interpreting the observational
results. JSD, RSE, NG, GI, AMK, DM, PGP-G and PS were involved in obtaining
and reducing the data for the PRIMER program which was used in this study. All
authors discussed the results and commented on the manuscript.

Competing interests

The authors declare no competing interests.

## References

  *   * (1) Curtis-Lake, E., Carniani, S., Cameron, A., Charlot, S., Jakobsen, P., Maiolino, R., Bunker, A., Witstok, J., Smit, R., Chevallard, J., Willott, C., Ferruit, P., Arribas, S., Bonaventura, N., Curti, M., D’Eugenio, F., Franx, M., Giardino, G., Looser, T.J., Lützgendorf, N., Maseda, M.V., Rawle, T., Rix, H.-W., Rodríguez del Pino, B., Übler, H., Sirianni, M., Dressler, A., Egami, E., Eisenstein, D.J., Endsley, R., Hainline, K., Hausen, R., Johnson, B.D., Rieke, M., Robertson, B., Shivaei, I., Stark, D.P., Tacchella, S., Williams, C.C., Willmer, C.N.A., Bhatawdekar, R., Bowler, R., Boyett, K., Chen, Z., de Graaff, A., Helton, J.M., Hviding, R.E., Jones, G.C., Kumari, N., Lyu, J., Nelson, E., Perna, M., Sandles, L., Saxena, A., Suess, K.A., Sun, F., Topping, M.W., Wallace, I.E.B., Whitler, L.: Spectroscopic confirmation of four metal-poor galaxies at z = 10.3-13.2. Nature Astronomy (2023) arXiv:2212.04568 [astro-ph.GA]. https://doi.org/10.1038/s41550-023-01918-w
  * (2) Arrabal Haro, P., Dickinson, M., Finkelstein, S.L., Kartaltepe, J.S., Donnan, C.T., Burgarella, D., Carnall, A., Cullen, F., Dunlop, J.S., Fernández, V., Fujimoto, S., Jung, I., Krips, M., Larson, R.L., Papovich, C., Pérez-González, P.G., Amorín, R.O., Bagley, M.B., Buat, V., Casey, C.M., Chworowsky, K., Cohen, S.H., Ferguson, H.C., Giavalisco, M., Huertas-Company, M., Hutchison, T.A., Kocevski, D.D., Koekemoer, A.M., Lucas, R.A., McLeod, D.J., McLure, R.J., Pirzkal, N., Trump, J.R., Weiner, B.J., Wilkins, S.M., Zavala, J.A.: Spectroscopic verification of very luminous galaxy candidates in the early universe. arXiv e-prints, 2303–15431 (2023) arXiv:2303.15431 [astro-ph.GA]. https://doi.org/10.48550/arXiv.2303.15431
  * (3) Williams, H., Kelly, P.L., Chen, W., Brammer, G., Zitrin, A., Treu, T., Scarlata, C., Koekemoer, A.M., Oguri, M., Lin, Y.-H., Diego, J.M., Nonino, M., Hjorth, J., Langeroodi, D., Broadhurst, T., Rogers, N., Perez-Fournon, I., Foley, R.J., Jha, S., Filippenko, A.V., Strolger, L., Pierel, J., Poidevin, F., Yang, L.: A Magnified Compact Galaxy at Redshift 9.51 with Strong Nebular Emission Lines. arXiv e-prints, 2210–15699 (2022) arXiv:2210.15699 [astro-ph.GA]. https://doi.org/10.48550/arXiv.2210.15699
  * (4) Dijkstra, M.: Ly$\alpha$ Emitting Galaxies as a Probe of Reionisation. PASA 31, 040 (2014) arXiv:1406.7292 [astro-ph.CO]. https://doi.org/10.1017/pasa.2014.33
  * (5) Heintz, K.E., Watson, D., Brammer, G., Vejlgaard, S., Hutter, A., Strait, V.B., Matthee, J., Oesch, P.A., Jakobsson, P., Tanvir, N.R., Laursen, P., Naidu, R.P., Mason, C.A., Killi, M., Jung, I., Hsiao, T.Y.-Y., Abdurro’uf, Coe, D., Arrabal Haro, P., Finkelstein, S.L., Toft, S.: Extreme damped Lyman-$\alpha$ absorption in young star-forming galaxies at $z=9-11$. arXiv e-prints, 2306–00647 (2023) arXiv:2306.00647 [astro-ph.GA]. https://doi.org/10.48550/arXiv.2306.00647
  * (6) Robertson, B.E., Ellis, R.S., Furlanetto, S.R., Dunlop, J.S.: Cosmic Reionization and Early Star-forming Galaxies: A Joint Analysis of New Constraints from Planck and the Hubble Space Telescope. ApJ 802(2), 19 (2015) arXiv:1502.02024 [astro-ph.CO]. https://doi.org/10.1088/2041-8205/802/2/L19
  * (7) De Barros, S., Pentericci, L., Vanzella, E., Castellano, M., Fontana, A., Grazian, A., Conselice, C.J., Yan, H., Koekemoer, A., Cristiani, S., Dickinson, M., Finkelstein, S.L., Maiolino, R.: VLT/FORS2 view at z 6: Lyman-$\alpha$ emitter fraction and galaxy physical properties at the edge of the epoch of cosmic reionization. A&A 608, 123 (2017) arXiv:1710.01784 [astro-ph.GA]. https://doi.org/10.1051/0004-6361/201731476
  * (8) Endsley, R., Stark, D.P., Bouwens, R.J., Schouws, S., Smit, R., Stefanon, M., Inami, H., Bowler, R.A.A., Oesch, P., Gonzalez, V., Aravena, M., da Cunha, E., Dayal, P., Ferrara, A., Graziani, L., Nanayakkara, T., Pallottini, A., Schneider, R., Sommovigo, L., Topping, M., van der Werf, P., Hutter, A.: The REBELS ALMA Survey: efficient Ly-$\alpha$ transmission of UV-bright z = 7 galaxies from large velocity offsets and broad line widths. MNRAS 517(4), 5642–5659 (2022) arXiv:2202.01219 [astro-ph.GA]. https://doi.org/10.1093/mnras/stac3064
  * (9) Bolan, P., Lemaux, B.C., Mason, C., Bradač, M., Treu, T., Strait, V., Pelliccia, D., Pentericci, L., Malkan, M.: Inferring the intergalactic medium neutral fraction at z 6-8 with low-luminosity Lyman break galaxies. MNRAS 517(3), 3263–3274 (2022) arXiv:2111.14912 [astro-ph.GA]. https://doi.org/10.1093/mnras/stac1963
  * (10) Hsiao, T.Y.-Y., Abdurro’uf, Coe, D., Larson, R.L., Jung, I., Mingozzi, M., Dayal, P., Kumari, N., Kokorev, V., Vikaeus, A., Brammer, G., Furtak, L.J., Adamo, A., Andrade-Santos, F., Antwi-Danso, J., Bradac, M., Bradley, L.D., Broadhurst, T., Carnall, A.C., Conselice, C.J., Diego, J.M., Donahue, M., Eldridge, J.J., Fujimoto, S., Henry, A., Hernandez, S., Hutchison, T.A., James, B.L., Norman, C., Park, H., Pirzkal, N., Postman, M., Ricotti, M., Rigby, J.R., Vanzella, E., Welch, B., Wilkins, S.M., Windhorst, R.A., Xu, X., Zackrisson, E., Zitrin, A.: JWST NIRSpec spectroscopy of the triply-lensed $z=10.17$ galaxy MACS0647$-$JD. arXiv e-prints, 2305–03042 (2023) arXiv:2305.03042 [astro-ph.GA]. https://doi.org/10.48550/arXiv.2305.03042
  * (11) Stark, D.P., Ellis, R.S., Charlot, S., Chevallard, J., Tang, M., Belli, S., Zitrin, A., Mainali, R., Gutkin, J., Vidal-García, A., Bouwens, R., Oesch, P.: Ly$\alpha$ and C III] emission in z = 7-9 Galaxies: accelerated reionization around luminous star-forming systems? MNRAS 464(1), 469–479 (2017) arXiv:1606.01304 [astro-ph.GA]. https://doi.org/10.1093/mnras/stw2233
  * (12) De Barros, S., Oesch, P.A., Labbé, I., Stefanon, M., González, V., Smit, R., Bouwens, R.J., Illingworth, G.D.: The GREATS H $\beta$ \+ [O III] luminosity function and galaxy properties at z $\sim$ 8: walking the way of JWST. MNRAS 489(2), 2355–2366 (2019) arXiv:1903.09649 [astro-ph.GA]. https://doi.org/10.1093/mnras/stz940
  * (13) Jones, G.C., Bunker, A.J., Saxena, A., Witstok, J., Stark, D.P., Arribas, S., Baker, W.M., Bhatawdekar, R., Bowler, R., Boyett, K., Cameron, A.J., Carniani, S., Charlot, S., Chevallard, J., Curti, M., Curtis-Lake, E., Eisenstein, D.J., Hainline, K., Hausen, R., Ji, Z., Johnson, B.D., Kumari, N., Looser, T.J., Maiolino, R., Maseda, M.V., Parlanti, E., Rix, H.-W., Robertson, B.E., Sandles, L., Scholtz, J., Smit, R., Tacchella, S., Ubler, H., Williams, C.C., Willott, C.: JADES: The emergence and evolution of Ly-alpha emission & constraints on the IGM neutral fraction. arXiv e-prints, 2306–02471 (2023) arXiv:2306.02471 [astro-ph.GA]. https://doi.org/10.48550/arXiv.2306.02471
  * (14) Bunker, A.J., Saxena, A., Cameron, A.J., Willott, C.J., Curtis-Lake, E., Jakobsen, P., Carniani, S., Smit, R., Maiolino, R., Witstok, J., Curti, M., D’Eugenio, F., Jones, G.C., Ferruit, P., Arribas, S., Charlot, S., Chevallard, J., Giardino, G., de Graaff, A., Looser, T.J., Luetzgendorf, N., Maseda, M.V., Rawle, T., Rix, H.-W., Rodriguez Del Pino, B., Alberts, S., Egami, E., Eisenstein, D.J., Endsley, R., Hainline, K., Hausen, R., Johnson, B.D., Rieke, G., Rieke, M., Robertson, B.E., Shivaei, I., Stark, D.P., Sun, F., Tacchella, S., Tang, M., Williams, C.C., Willmer, C.N.A., Baker, W.M., Baum, S., Bhatawdekar, R., Bowler, R., Boyett, K., Chen, Z., Circosta, C., Helton, J.M., Ji, Z., Lyu, J., Nelson, E., Parlanti, E., Perna, M., Sandles, L., Scholtz, J., Suess, K.A., Topping, M.W., Uebler, H., Wallace, I.E.B., Whitler, L.: JADES NIRSpec Spectroscopy of GN-z11: Lyman-$\alpha$ emission and possible enhanced nitrogen abundance in a $z=10.60$ luminous galaxy. arXiv e-prints, 2302–07256 (2023) arXiv:2302.07256 [astro-ph.GA]. https://doi.org/10.48550/arXiv.2302.07256
  * (15) Jung, I., Finkelstein, S.L., Arrabal Haro, P., Dickinson, M., Ferguson, H.C., Hutchison, T.A., Kartaltepe, J.S., Larson, R.L., Simons, R.C., Papovich, C., Park, H., Pentericci, L., Trump, J.R., Amorin, R.O., Backhaus, B.E., Casey, C.M., Cheng, Y., Cleri, N.J., Cooper, M.C., Cooper, O.R., Gardner, J.P., Gawiser, E., Grazian, A., Hathi, N.P., Hirschmann, M., Koekemoer, A.M., Lucas, R.A., Mobasher, B., Ravindranath, S., Straughn, A.N., Yung, L.Y.A., de la Vega, A.: CEERS: Diversity of Lyman-Alpha Emitters during the Epoch of Reionization. arXiv e-prints, 2304–05385 (2023) arXiv:2304.05385 [astro-ph.GA]. https://doi.org/10.48550/arXiv.2304.05385
  * (16) Laporte, N., Nakajima, K., Ellis, R.S., Zitrin, A., Stark, D.P., Mainali, R., Roberts-Borsani, G.W.: A Spectroscopic Search for AGN Activity in the Reionization Era. ApJ 851(1), 40 (2017) arXiv:1708.05173 [astro-ph.GA]. https://doi.org/10.3847/1538-4357/aa96a8
  * (17) Larson, R.L., Finkelstein, S.L., Kocevski, D.D., Hutchison, T.A., Trump, J.R., Arrabal Haro, P., Bromm, V., Cleri, N.J., Dickinson, M., Fujimoto, S., Kartaltepe, J.S., Koekemoer, A.M., Papovich, C., Pirzkal, N., Tacchella, S., Zavala, J.A., Bagley, M., Behroozi, P., Champagne, J.B., Cole, J.W., Jung, I., Morales, A.M., Yang, G., Zhang, H., Zitrin, A., Amorín, R.O., Burgarella, D., Casey, C.M., Chávez Ortiz, Ó.A., Cox, I.G., Chworowsky, K., Fontana, A., Gawiser, E., Grazian, A., Grogin, N.A., Harish, S., Hathi, N.P., Hirschmann, M., Holwerda, B.W., Juneau, S., Leung, G.C.K., Lucas, R.A., McGrath, E.J., Pérez-González, P.G., Rigby, J.R., Seillé, L.-M., Simons, R.C., Weiner, B.J., Wilkins, S.M., Yung, L.Y.A., The CEERS Team: A CEERS Discovery of an Accreting Supermassive Black Hole 570 Myr after the Big Bang: Identifying a Progenitor of Massive z ¿ 6 Quasars. arXiv e-prints, 2303–08918 (2023) arXiv:2303.08918 [astro-ph.GA]. https://doi.org/10.48550/arXiv.2303.08918
  * (18) Maiolino, R., Scholtz, J., Witstok, J., Carniani, S., D’Eugenio, F., de Graaff, A., Uebler, H., Tacchella, S., Curtis-Lake, E., Arribas, S., Bunker, A., Charlot, S., Chevallard, J., Curti, M., Looser, T.J., Maseda, M.V., Rawle, T., Rodriguez Del Pino, B., Willott, C.J., Egami, E., Eisenstein, D., Hainline, K., Robertson, B., Williams, C.C., Willmer, C.N.A., Baker, W.M., Boyett, K., DeCoursey, C., Fabian, A.C., Helton, J.M., Ji, Z., Jones, G.C., Kumari, N., Laporte, N., Nelson, E., Perna, M., Sandles, L., Shivaei, I., Sun, F.: A small and vigorous black hole in the early Universe. arXiv e-prints, 2305–12492 (2023) arXiv:2305.12492 [astro-ph.GA]. https://doi.org/10.48550/arXiv.2305.12492
  * (19) Castellano, M., Dayal, P., Pentericci, L., Fontana, A., Hutter, A., Brammer, G., Merlin, E., Grazian, A., Pilo, S., Amorin, R., Cristiani, S., Dickinson, M., Ferrara, A., Gallerani, S., Giallongo, E., Giavalisco, M., Guaita, L., Koekemoer, A., Maiolino, R., Paris, D., Santini, P., Vallini, L., Vanzella, E., Wagg, J.: First Observational Support for Overlapping Reionized Bubbles Generated by a Galaxy Overdensity. ApJ 818(1), 3 (2016) arXiv:1601.03442 [astro-ph.GA]. https://doi.org/10.3847/2041-8205/818/1/L3
  * (20) Tilvi, V., Malhotra, S., Rhoads, J.E., Coughlin, A., Zheng, Z., Finkelstein, S.L., Veilleux, S., Mobasher, B., Wang, J., Probst, R., Swaters, R., Hibon, P., Joshi, B., Zabl, J., Jiang, T., Pharo, J., Yang, H.: Onset of Cosmic Reionization: Evidence of an Ionized Bubble Merely 680 Myr after the Big Bang. ApJ 891(1), 10 (2020) arXiv:2001.00873 [astro-ph.GA]. https://doi.org/10.3847/2041-8213/ab75ec
  * (21) Leonova, E., Oesch, P.A., Qin, Y., Naidu, R.P., Wyithe, J.S.B., de Barros, S., Bouwens, R.J., Ellis, R.S., Endsley, R.M., Hutter, A., Illingworth, G.D., Kerutt, J., Labbé, I., Laporte, N., Magee, D., Mutch, S.J., Roberts-Borsani, G.W., Smit, R., Stark, D.P., Stefanon, M., Tacchella, S., Zitrin, A.: The prevalence of galaxy overdensities around UV-luminous Lyman-$\alpha$ emitters in the Epoch of Reionization. MNRAS 515(4), 5790–5801 (2022) arXiv:2112.07675 [astro-ph.GA]. https://doi.org/10.1093/mnras/stac1908
  * (22) Morishita, T., Roberts-Borsani, G., Treu, T., Brammer, G., Mason, C.A., Trenti, M., Vulcani, B., Wang, X., Acebron, A., Bahé, Y., Bergamini, P., Boyett, K., Bradac, M., Calabrò, A., Castellano, M., Chen, W., De Lucia, G., Filippenko, A.V., Fontana, A., Glazebrook, K., Grillo, C., Henry, A., Jones, T., Kelly, P.L., Koekemoer, A.M., Leethochawalit, N., Lu, T.-Y., Marchesini, D., Mascia, S., Mercurio, A., Merlin, E., Metha, B., Nanayakkara, T., Nonino, M., Paris, D., Pentericci, L., Santini, P., Strait, V., Vanzella, E., Windhorst, R.A., Rosati, P., Xie, L.: Early results from GLASS-JWST. XVIII: A spectroscopically confirmed protocluster 650 million years after the Big Bang. arXiv e-prints, 2211–09097 (2022) arXiv:2211.09097 [astro-ph.GA]. https://doi.org/10.48550/arXiv.2211.09097
  * (23) Tang, M., Stark, D.P., Chen, Z., Mason, C., Topping, M., Endsley, R., Senchyna, P., Plat, A., Lu, T.-Y., Whitler, L., Robertson, B., Charlot, S.: JWST/NIRSpec Spectroscopy of $z=7-9$ Star Forming Galaxies with CEERS: New Insight into Bright Ly$\alpha$ Emitters in Ionized Bubbles. arXiv e-prints, 2301–07072 (2023) arXiv:2301.07072 [astro-ph.GA]. https://doi.org/10.48550/arXiv.2301.07072
  * (24) Tacchella, S., Eisenstein, D.J., Hainline, K., Johnson, B.D., Baker, W.M., Helton, J.M., Robertson, B., Suess, K.A., Chen, Z., Nelson, E., Puskás, D., Sun, F., Alberts, S., Egami, E., Hausen, R., Rieke, G., Rieke, M., Shivaei, I., Williams, C.C., Willmer, C.N.A., Bunker, A., Cameron, A.J., Carniani, S., Charlot, S., Curti, M., Curtis-Lake, E., Looser, T.J., Maiolino, R., Maseda, M.V., Rawle, T., Rix, H.-W., Smit, R., Übler, H., Willott, C., Witstok, J., Baum, S., Bhatawdekar, R., Boyett, K., Danhaive, A.L., de Graaff, A., Endsley, R., Ji, Z., Lyu, J., Sandles, L., Saxena, A., Scholtz, J., Topping, M.W., Whitler, L.: JADES Imaging of GN-z11: Revealing the Morphology and Environment of a Luminous Galaxy 430 Myr After the Big Bang. arXiv e-prints, 2302–07234 (2023) arXiv:2302.07234 [astro-ph.GA]. https://doi.org/10.48550/arXiv.2302.07234
  * (25) Witstok, J., Smit, R., Saxena, A., Jones, G.C., Helton, J.M., Sun, F., Maiolino, R., Stark, D.P., Bunker, A.J., Arribas, S., Baker, W.M., Bhatawdekar, R., Boyett, K., Cameron, A.J., Carniani, S., Charlot, S., Chevallard, J., Curti, M., Curtis-Lake, E., Eisenstein, D.J., Endsley, R., Hainline, K., Ji, Z., Johnson, B.D., Kumari, N., Looser, T.J., Nelson, E., Perna, M., Rix, H.-W., Robertson, B.E., Sandles, L., Scholtz, J., Simmonds, C., Tacchella, S., Übler, H., Williams, C.C., Willmer, C.N.A., Willott, C.: Inside the bubble: exploring the environments of reionisation-era Lyman-$\alpha$ emitting galaxies with JADES and FRESCO. arXiv e-prints, 2306–04627 (2023) arXiv:2306.04627 [astro-ph.GA]. https://doi.org/10.48550/arXiv.2306.04627
  * (26) Rieke, M.J., Kelly, D.M., Misselt, K., Stansberry, J., Boyer, M., Beatty, T., Egami, E., Florian, M., Greene, T.P., Hainline, K., Leisenring, J., Roellig, T., Schlawin, E., Sun, F., Tinnin, L., Williams, C.C., Willmer, C.N.A., Wilson, D., Clark, C.R., Rohrbach, S., Brooks, B., Canipe, A., Correnti, M., DiFelice, A., Gennaro, M., Girard, J., Hartig, G., Hilbert, B., Koekemoer, A.M., Nikolov, N.K., Pirzkal, N., Rest, A., Robberto, M., Sunnquist, B., Telfer, R., Wu, C.R., Ferry, M., Lewis, D., Baum, S., Beichman, C., Doyon, R., Dressler, A., Eisenstein, D.J., Ferrarese, L., Hodapp, K., Horner, S., Jaffe, D.T., Johnstone, D., Krist, J., Martin, P., McCarthy, D.W., Meyer, M., Rieke, G.H., Trauger, J., Young, E.T.: Performance of NIRCam on JWST in Flight. PASP 135(1044), 028001 (2023). https://doi.org/10.1088/1538-3873/acac53
  * (27) Oesch, P.A., Brammer, G., Naidu, R.P., Bouwens, R.J., Chisholm, J., Illingworth, G.D., Matthee, J., Nelson, E., Qin, Y., Reddy, N., Shapley, A., Shivaei, I., van Dokkum, P., Weibel, A., Whitaker, K., Wuyts, S., Covelo-Paz, A., Endsley, R., Fudamoto, Y., Giovinazzo, E., Herard-Demanche, T., Kerutt, J., Kramarenko, I., Labbe, I., Leonova, E., Lin, J., Magee, D., Marchesini, D., Maseda, M., Mason, C., Matharu, J., Meyer, R.A., Neufeld, C., Prieto Lyon, G., Schaerer, D., Sharma, R., Shuntov, M., Smit, R., Stefanon, M., Wyithe, J.S.B., Xiao, M.: The JWST FRESCO Survey: Legacy NIRCam/Grism Spectroscopy and Imaging in the two GOODS Fields. arXiv e-prints, 2304–02026 (2023) arXiv:2304.02026 [astro-ph.GA]. https://doi.org/10.48550/arXiv.2304.02026
  * (28) Bagley, M.B., Finkelstein, S.L., Koekemoer, A.M., Ferguson, H.C., Arrabal Haro, P., Dickinson, M., Kartaltepe, J.S., Papovich, C., Pérez-González, P.G., Pirzkal, N., Somerville, R.S., Willmer, C.N.A., Yang, G., Yung, L.Y.A., Fontana, A., Grazian, A., Grogin, N.A., Hirschmann, M., Kewley, L.J., Kirkpatrick, A., Kocevski, D.D., Lotz, J.M., Medrano, A., Morales, A.M., Pentericci, L., Ravindranath, S., Trump, J.R., Wilkins, S.M., Calabrò, A., Cooper, M.C., Costantin, L., de la Vega, A., Hilbert, B., Hutchison, T.A., Larson, R.L., Lucas, R.A., McGrath, E.J., Ryan, R., Wang, X., Wuyts, S.: CEERS Epoch 1 NIRCam Imaging: Reduction Methods and Simulations Enabling Early JWST Science Results. ApJ 946(1), 12 (2023) arXiv:2211.02495 [astro-ph.IM]. https://doi.org/10.3847/2041-8213/acbb08
  * (29) Rieke, M., the JADES Collaboration: JADES Initial Data Release for the Hubble Ultra Deep Field: Revealing the Faint Infrared Sky with Deep JWST NIRCam Imaging. arXiv e-prints, 2306–02466 (2023) arXiv:2306.02466 [astro-ph.GA]. https://doi.org/10.48550/arXiv.2306.02466
  * (30) Maiolino, R., Uebler, H., Perna, M., Scholtz, J., D’Eugenio, F., Witten, C., Laporte, N., Witstok, J., Carniani, S., Tacchella, S., Baker, W., Arribas, S., Nakajima, K., Eisenstein, D., Bunker, A., Charlot, S., Cresci, G., Curti, M., Curtis-Lake, E., de Graaff, A., Ji, Z., Johnson, B.D., Kumari, N., Looser, T.J., Maseda, M., Robertson, B., Rodriguez Del Pino, B., Sandles, L., Simmonds, C., Smit, R., Sun, F., Venturi, G., Williams, C., Willmer, C.: JWST-JADES. Possible Population III signatures at z=10.6 in the halo of GN-z11. arXiv e-prints, 2306–00953 (2023) arXiv:2306.00953 [astro-ph.GA]. https://doi.org/10.48550/arXiv.2306.00953
  * (31) Jung, I., Finkelstein, S.L., Larson, R.L., Hutchison, T.A., Straughn, A.N., Bagley, M.B., Castellano, M., Cleri, N.J., Cooper, M.C., Dickinson, M., Ferguson, H.C., Holwerda, B.W., Kartaltepe, J.S., Kim, S., Koekemoer, A.M., Papovich, C., Park, H., Pentericci, L., Perez-Gonzalez, P.G., Song, M., Tacchella, S., Weiner, B.J., Willmer, C.N.A., Zavala, J.A.: New $z>7$ Lyman-alpha Emitters in EGS: Evidence of an Extended Ionized Structure at $z\sim 7.7$. arXiv e-prints, 2212–09850 (2022) arXiv:2212.09850 [astro-ph.GA]. https://doi.org/10.48550/arXiv.2212.09850
  * (32) Carnall, A.C., McLure, R.J., Dunlop, J.S., Davé, R.: Inferring the star formation histories of massive quiescent galaxies with BAGPIPES: evidence for multiple quenching mechanisms. MNRAS 480(4), 4379–4401 (2018) arXiv:1712.04452 [astro-ph.GA]. https://doi.org/10.1093/mnras/sty2169
  * (33) Roberts-Borsani, G.W., Bouwens, R.J., Oesch, P.A., Labbe, I., Smit, R., Illingworth, G.D., van Dokkum, P., Holden, B., Gonzalez, V., Stefanon, M., Holwerda, B., Wilkins, S.: z $\gtrsim$ 7 Galaxies with Red Spitzer/IRAC [3.6]-[4.5] Colors in the Full CANDELS Data Set: The Brightest-Known Galaxies at z $\sim$ 7-9 and a Probable Spectroscopic Confirmation at z = 7.48. ApJ 823(2), 143 (2016) arXiv:1506.00854 [astro-ph.GA]. https://doi.org/10.3847/0004-637X/823/2/143
  * (34) Witten, C.E.C., Laporte, N., Katz, H.: Evidence for a Low Lyman Continuum Escape Fraction in Three Massive, Ultraviolet-bright Galaxies at z $>$ 7\. ApJ 944(1), 61 (2023) arXiv:2301.03599 [astro-ph.GA]. https://doi.org/10.3847/1538-4357/acac9d
  * (35) Saxena, A., Robertson, B.E., Bunker, A.J., Endsley, R., Cameron, A.J., Charlot, S., Simmonds, C., Tacchella, S., Witstok, J., Willott, C., Carniani, S., Curtis-Lake, E., Ferruit, P., Jakobsen, P., Arribas, S., Chevallard, J., Curti, M., D’Eugenio, F., De Graaff, A., Jones, G.C., Looser, T.J., Maseda, M.V., Rawle, T., Rix, H.-W., Rodríguez Del Pino, B., Smit, R., Übler, H., Eisenstein, D.J., Hainline, K., Hausen, R., Johnson, B.D., Rieke, M., Williams, C.C., Willmer, C.N.A., Baker, W.M., Bhatawdekar, R., Bowler, R., Boyett, K., Chen, Z., Egami, E., Ji, Z., Nelson, E., Perna, M., Sandles, L., Scholtz, J., Shivaei, I.: JADES: Discovery of extremely high equivalent width Lyman-alpha emission from a faint galaxy within an ionized bubble at z=7.3. arXiv e-prints, 2302–12805 (2023) arXiv:2302.12805 [astro-ph.GA]. https://doi.org/%****␣Main.bbl␣Line␣1450␣****10.48550/arXiv.2302.12805
  * (36) Song, M., Finkelstein, S.L., Livermore, R.C., Capak, P.L., Dickinson, M., Fontana, A.: Keck/MOSFIRE Spectroscopy of z = 7-8 Galaxies: Ly$\alpha$ Emission from a Galaxy at z = 7.66. ApJ 826(2), 113 (2016) arXiv:1602.02160 [astro-ph.GA]. https://doi.org/10.3847/0004-637X/826/2/113
  * (37) Roberts-Borsani, G., Treu, T., Mason, C., Ellis, R.S., Laporte, N., Schmidt, T., Bradač, M., Fontana, A., Morishita, T., Santini, P.: Nature and Nurture? Comparing Ly$\alpha$ Detections in UV Bright and Fainter [O III]+H$\beta$ Emitters at $z\sim 8$ With Keck/MOSFIRE. arXiv e-prints, 2207–01629 (2022) arXiv:2207.01629 [astro-ph.GA]. https://doi.org/10.48550/arXiv.2207.01629
  * (38) Zitrin, A., Labbé, I., Belli, S., Bouwens, R., Ellis, R.S., Roberts-Borsani, G., Stark, D.P., Oesch, P.A., Smit, R.: Lyman$\alpha$ Emission from a Luminous z = 8.68 Galaxy: Implications for Galaxies as Tracers of Cosmic Reionization. ApJ 810(1), 12 (2015) arXiv:1507.02679 [astro-ph.GA]. https://doi.org/10.1088/2041-8205/810/1/L12
  * (39) Scholtz, J., Witten, C., Laporte, N., Ubler, H., Perna, M., Maiolino, R., Arribas, S., Baker, W., Bennett, J., D’Eugenio, F., Tacchella, S., Witstok, J., Bunker, A., Carniani, S., Charlot, S., Curtis-Lake, E., Eisenstein, D., Robertson, B., Rodriguez Del Pino, B., Simmonds, C., Smit, R., Venturi, G., Williams, C., Willmer, C.: GN-z11: The environment of an AGN at $z=$10.603. arXiv e-prints, 2306–09142 (2023) arXiv:2306.09142 [astro-ph.GA]
  * (40) Übler, H., Maiolino, R., Pérez-González, P.G., D’Eugenio, F., Perna, M., Curti, M., Arribas, S., Bunker, A., Carniani, S., Charlot, S., Rodríguez Del Pino, B., Baker, W., Böker, T., Cresci, G., Dunlop, J., Grogin, N.A., Jones, G.C., Kumari, N., Lamperti, I., Laporte, N., Marshall, M.A., Mazzolari, G., Parlanti, E., Rawle, T., Scholtz, J., Venturi, G., Witstok, J.: GA-NIFS: JWST discovers an offset AGN 740 million years after the Big Bang. arXiv e-prints, 2312–03589 (2023) arXiv:2312.03589 [astro-ph.GA]. https://doi.org/10.48550/arXiv.2312.03589
  * (41) Vernet, J., Dekker, H., D’Odorico, S., Kaper, L., Kjaergaard, P., Hammer, F., Randich, S., Zerbi, F., Groot, P.J., Hjorth, J., Guinouard, I., Navarro, R., Adolfse, T., Albers, P.W., Amans, J.-P., Andersen, J.J., Andersen, M.I., Binetruy, P., Bristow, P., Castillo, R., Chemla, F., Christensen, L., Conconi, P., Conzelmann, R., Dam, J., de Caprio, V., de Ugarte Postigo, A., Delabre, B., di Marcantonio, P., Downing, M., Elswijk, E., Finger, G., Fischer, G., Flores, H., François, P., Goldoni, P., Guglielmi, L., Haigron, R., Hanenburg, H., Hendriks, I., Horrobin, M., Horville, D., Jessen, N.C., Kerber, F., Kern, L., Kiekebusch, M., Kleszcz, P., Klougart, J., Kragt, J., Larsen, H.H., Lizon, J.-L., Lucuix, C., Mainieri, V., Manuputy, R., Martayan, C., Mason, E., Mazzoleni, R., Michaelsen, N., Modigliani, A., Moehler, S., Møller, P., Norup Sørensen, A., Nørregaard, P., Péroux, C., Patat, F., Pena, E., Pragt, J., Reinero, C., Rigal, F., Riva, M., Roelfsema, R., Royer, F., Sacco, G., Santin, P., Schoenmaker, T., Spano, P., Sweers, E., Ter Horst, R., Tintori, M., Tromp, N., van Dael, P., van der Vliet, H., Venema, L., Vidali, M., Vinther, J., Vola, P., Winters, R., Wistisen, D., Wulterkens, G., Zacchei, A.: X-shooter, the new wide band intermediate resolution spectrograph at the ESO Very Large Telescope. A&A 536, 105 (2011) arXiv:1110.1944 [astro-ph.IM]. https://doi.org/10.1051/0004-6361/201117752
  * (42) McLean, I.S., Steidel, C.C., Epps, H., Matthews, K., Adkins, S., Konidaris, N., Weber, B., Aliado, T., Brims, G., Canfield, J., Cromer, J., Fucik, J., Kulas, K., Mace, G., Magnone, K., Rodriguez, H., Wang, E., Weiss, J.: Design and development of MOSFIRE: the multi-object spectrometer for infrared exploration at the Keck Observatory. In: McLean, I.S., Ramsay, S.K., Takami, H. (eds.) Ground-based and Airborne Instrumentation for Astronomy III. Society of Photo-Optical Instrumentation Engineers (SPIE) Conference Series, vol. 7735, p. 77351 (2010). https://doi.org/10.1117/12.856715
  * (43) McLean, I.S., Steidel, C.C., Epps, H.W., Konidaris, N., Matthews, K.Y., Adkins, S., Aliado, T., Brims, G., Canfield, J.M., Cromer, J.L., Fucik, J., Kulas, K., Mace, G., Magnone, K., Rodriguez, H., Rudie, G., Trainor, R., Wang, E., Weber, B., Weiss, J.: MOSFIRE, the multi-object spectrometer for infra-red exploration at the Keck Observatory. In: McLean, I.S., Ramsay, S.K., Takami, H. (eds.) Ground-based and Airborne Instrumentation for Astronomy IV. Society of Photo-Optical Instrumentation Engineers (SPIE) Conference Series, vol. 8446, p. 84460 (2012). https://doi.org/10.1117/12.924794
  * (44) Jakobsen, P., Ferruit, P., Alves de Oliveira, C., Arribas, S., Bagnasco, G., Barho, R., Beck, T.L., Birkmann, S., Böker, T., Bunker, A.J., Charlot, S., de Jong, P., de Marchi, G., Ehrenwinkler, R., Falcolini, M., Fels, R., Franx, M., Franz, D., Funke, M., Giardino, G., Gnata, X., Holota, W., Honnen, K., Jensen, P.L., Jentsch, M., Johnson, T., Jollet, D., Karl, H., Kling, G., Köhler, J., Kolm, M.-G., Kumari, N., Lander, M.E., Lemke, R., López-Caniego, M., Lützgendorf, N., Maiolino, R., Manjavacas, E., Marston, A., Maschmann, M., Maurer, R., Messerschmidt, B., Moseley, S.H., Mosner, P., Mott, D.B., Muzerolle, J., Pirzkal, N., Pittet, J.-F., Plitzke, A., Posselt, W., Rapp, B., Rauscher, B.J., Rawle, T., Rix, H.-W., Rödel, A., Rumler, P., Sabbi, E., Salvignol, J.-C., Schmid, T., Sirianni, M., Smith, C., Strada, P., te Plate, M., Valenti, J., Wettemann, T., Wiehe, T., Wiesmayer, M., Willott, C.J., Wright, R., Zeidler, P., Zincke, C.: The Near-Infrared Spectrograph (NIRSpec) on the James Webb Space Telescope. I. Overview of the instrument and its capabilities. A&A 661, 80 (2022) arXiv:2202.03305 [astro-ph.IM]. https://doi.org/10.1051/0004-6361/202142663
  * (45) Rieke, M.J., Kelly, D., Horner, S.: Overview of James Webb Space Telescope and NIRCam’s Role. In: Heaney, J.B., Burriesci, L.G. (eds.) Cryogenic Optical Systems and Instruments XI. Society of Photo-Optical Instrumentation Engineers (SPIE) Conference Series, vol. 5904, pp. 1–8 (2005). https://doi.org/10.1117/12.615554
  * (46) Martin-Alvarez, S., Sijacki, D., Haehnelt, M.G., Farcy, M., Dubois, Y., Belokurov, V., Rosdahl, J., Lopez-Rodriguez, E.: The Pandora project. I: the impact of radiation and cosmic rays on baryonic and dark matter properties of dwarf galaxies. MNRAS, submitted, 2211–09139 (2022) arXiv:2211.09139 [astro-ph.GA]. https://doi.org/10.48550/arXiv.2211.09139
  * (47) Rosdahl, J., Teyssier, R.: A scheme for radiation pressure and photon diffusion with the M1 closure in RAMSES-RT. MNRAS 449(4), 4380–4403 (2015) arXiv:1411.6440 [astro-ph.IM]. https://doi.org/10.1093/mnras/stv567
  * (48) Rosdahl, J., Katz, H., Blaizot, J., Kimm, T., Michel-Dansac, L., Garel, T., Haehnelt, M., Ocvirk, P., Teyssier, R.: The SPHINX cosmological simulations of the first billion years: the impact of binary stars on reionization. MNRAS 479(1), 994–1016 (2018) arXiv:1801.07259 [astro-ph.GA]. https://doi.org/10.1093/mnras/sty1655
  * (49) Rosdahl, J., Blaizot, J., Katz, H., Kimm, T., Garel, T., Haehnelt, M., Keating, L.C., Martin-Alvarez, S., Michel-Dansac, L., Ocvirk, P.: LyC escape from SPHINX galaxies in the Epoch of Reionization. MNRAS 515(2), 2386–2414 (2022) arXiv:2207.03232 [astro-ph.GA]. https://doi.org/10.1093/mnras/stac1942
  * (50) Kimm, T., Cen, R.: Escape Fraction of Ionizing Photons during Reionization: Effects due to Supernova Feedback and Runaway OB Stars. ApJ 788(2), 121 (2014) arXiv:1405.0552 [astro-ph.GA]. https://doi.org/10.1088/0004-637X/788/2/121
  * (51) Garel, T., Blaizot, J., Rosdahl, J., Michel-Dansac, L., Haehnelt, M.G., Katz, H., Kimm, T., Verhamme, A.: Ly $\alpha$ as a tracer of cosmic reionization in the SPHINX radiation-hydrodynamics cosmological simulation. MNRAS 504(2), 1902–1926 (2021) arXiv:2104.03339 [astro-ph.GA]. https://doi.org/10.1093/mnras/stab990
  * (52) Michel-Dansac, L., Blaizot, J., Garel, T., Verhamme, A., Kimm, T., Trebitsch, M.: RASCAS: RAdiation SCattering in Astrophysical Simulations. A&A 635, 154 (2020) arXiv:2001.11252 [astro-ph.GA]. https://doi.org/10.1051/0004-6361/201834961
  * (53) Laursen, P., Sommer-Larsen, J., Andersen, A.C.: Ly$\alpha$ Radiative Transfer with Dust: Escape Fractions from Simulated High-Redshift Galaxies. ApJ 704(2), 1640–1656 (2009) arXiv:0907.2698 [astro-ph.CO]. https://doi.org/10.1088/0004-637X/704/2/1640
  * (54) Asada, Y., Sawicki, M., Desprez, G., Abraham, R., Bradač, M., Brammer, G., Harshan, A., Iyer, K., Martis, N.S., Mowla, L., Muzzin, A., Noirot, G., Ravindranath, S., Sarrouh, G.T.E., Strait, V., Willott, C.J., Zabl, J.: JWST catches the assembly of a z 5 ultra-low-mass galaxy. MNRAS 523(1), 40–45 (2023) arXiv:2212.07540 [astro-ph.GA]. https://doi.org/10.1093/mnrasl/slad054
  * (55) Costa, T., Arrigoni Battaia, F., Farina, E.P., Keating, L.C., Rosdahl, J., Kimm, T.: AGN-driven outflows and the formation of Ly$\alpha$ nebulae around high-z quasars. MNRAS 517(2), 1767–1790 (2022) arXiv:2203.11232 [astro-ph.GA]. https://doi.org/10.1093/mnras/stac2432
  * (56) Finkelstein, S.L., Bagley, M.B., Ferguson, H.C., Wilkins, S.M., Kartaltepe, J.S., Papovich, C., Yung, L.Y.A., Arrabal Haro, P., Behroozi, P., Dickinson, M., Kocevski, D.D., Koekemoer, A.M., Larson, R.L., Le Bail, A., Morales, A.M., Perez-Gonzalez, P.G., Burgarella, D., Dave, R., Hirschmann, M., Somerville, R.S., Wuyts, S., Bromm, V., Casey, C.M., Fontana, A., Fujimoto, S., Gardner, J.P., Giavalisco, M., Grazian, A., Grogin, N.A., Hathi, N.P., Hutchison, T.A., Jha, S.W., Jogee, S., Kewley, L.J., Kirkpatrick, A., Long, A.S., Lotz, J.M., Pentericci, L., Pierel, J.D.R., Pirzkal, N., Ravindranath, S., Ryan, J. Russell E., Trump, J.R., Yang, G., Bhatawdekar, R., Bisigello, L., Buat, V., Calabro, A., Castellano, M., Cleri, N.J., Cooper, M.C., Croton, D., Daddi, E., Dekel, A., Elbaz, D., Franco, M., Gawiser, E., Holwerda, B.W., Huertas-Company, M., Jaskot, A.E., Leung, G.C.K., Lucas, R.A., Mobasher, B., Pandya, V., Tacchella, S., Weiner, B.J., Zavala, J.A.: CEERS Key Paper I: An Early Look into the First 500 Myr of Galaxy Formation with JWST. arXiv e-prints, 2211–05792 (2022) arXiv:2211.05792 [astro-ph.GA]. https://doi.org/10.48550/arXiv.2211.05792
  * (57) Eisenstein, D.J., Willott, C., Alberts, S., Arribas, S., Bonaventura, N., Bunker, A.J., Cameron, A.J., Carniani, S., Charlot, S., Curtis-Lake, E., D’Eugenio, F., Endsley, R., Ferruit, P., Giardino, G., Hainline, K., Hausen, R., Jakobsen, P., Johnson, B.D., Maiolino, R., Rieke, M., Rieke, G., Rix, H.-W., Robertson, B., Stark, D.P., Tacchella, S., Williams, C.C., Willmer, C.N.A., Baker, W.M., Baum, S., Bhatawdekar, R., Boyett, K., Chen, Z., Chevallard, J., Circosta, C., Curti, M., Danhaive, A.L., DeCoursey, C., de Graaff, A., Dressler, A., Egami, E., Helton, J.M., Hviding, R.E., Ji, Z., Jones, G.C., Kumari, N., Lützgendorf, N., Laseter, I., Looser, T.J., Lyu, J., Maseda, M.V., Nelson, E., Parlanti, E., Perna, M., Puskás, D., Rawle, T., Rodríguez Del Pino, B., Sandles, L., Saxena, A., Scholtz, J., Sharpe, K., Shivaei, I., Silcock, M.S., Simmonds, C., Skarbinski, M., Smit, R., Stone, M., Suess, K.A., Sun, F., Tang, M., Topping, M.W., Übler, H., Villanueva, N.C., Wallace, I.E.B., Whitler, L., Witstok, J., Woodrum, C.: Overview of the JWST Advanced Deep Extragalactic Survey (JADES). arXiv e-prints, 2306–02465 (2023) arXiv:2306.02465 [astro-ph.GA]. https://doi.org/10.48550/arXiv.2306.02465
  * (58) Bertin, E., Arnouts, S.: SExtractor: Software for source extraction. A&AS 117, 393–404 (1996). https://doi.org/10.1051/aas:1996164
  * (59) Peng, C.Y., Ho, L.C., Impey, C.D., Rix, H.-W.: Detailed Structural Decomposition of Galaxy Images. AJ 124(1), 266–293 (2002) arXiv:astro-ph/0204182 [astro-ph]. https://doi.org/10.1086/340952
  * (60) Laporte, N., Ellis, R.S., Witten, C.E.C., Roberts-Borsani, G.: Resolving Ambiguities in the Inferred Star Formation Histories of Intense [O III] Emitters in the Reionisation Era. arXiv e-prints, 2212–05072 (2022) arXiv:2212.05072 [astro-ph.GA]. https://doi.org/10.48550/arXiv.2212.05072
  * (61) Sun, F., Egami, E., Pirzkal, N., Rieke, M., Baum, S., Boyer, M., Boyett, K., Bunker, A.J., Cameron, A.J., Curti, M., Eisenstein, D.J., Gennaro, M., Greene, T.P., Jaffe, D., Kelly, D., Koekemoer, A.M., Kumari, N., Maiolino, R., Maseda, M., Perna, M., Rest, A., Robertson, B.E., Schlawin, E., Smit, R., Stansberry, J., Sunnquist, B., Tacchella, S., Williams, C.C., Willmer, C.N.A.: First Sample of H$\alpha$+[O III] $\lambda$5007 Line Emitters at $z>6$ through JWST/NIRCam Slitless Spectroscopy: Physical Properties and Line Luminosity Functions. arXiv e-prints, 2209–03374 (2022) arXiv:2209.03374 [astro-ph.GA]. https://doi.org/10.48550/arXiv.2209.03374
  * (62) Bouwens, R.J., Illingworth, G.D., Oesch, P.A., Trenti, M., Labbé, I., Bradley, L., Carollo, M., van Dokkum, P.G., Gonzalez, V., Holwerda, B., Franx, M., Spitler, L., Smit, R., Magee, D.: UV Luminosity Functions at Redshifts z $\sim$ 4 to z $\sim$ 10: 10,000 Galaxies from HST Legacy Fields. ApJ 803(1), 34 (2015) arXiv:1403.4295 [astro-ph.CO]. https://doi.org/10.1088/0004-637X/803/1/34
  * (63) Kennicutt, J. Robert C.: Star Formation in Galaxies Along the Hubble Sequence. ARA&A 36, 189–232 (1998) arXiv:astro-ph/9807187 [astro-ph]. https://doi.org/10.1146/annurev.astro.36.1.189
  * (64) Laporte, N., Meyer, R.A., Ellis, R.S., Robertson, B.E., Chisholm, J., Roberts-Borsani, G.W.: Probing cosmic dawn: Ages and star formation histories of candidate z $\geq$ 9 galaxies. MNRAS 505(3), 3336–3346 (2021) arXiv:2104.08168 [astro-ph.GA]. https://doi.org/10.1093/mnras/stab1239
  * (65) Laporte, N., Zitrin, A., Dole, H., Roberts-Borsani, G., Furtak, L.J., Witten, C.: A lensed protocluster candidate at z = 7.66 identified in JWST observations of the galaxy cluster SMACS0723$-$7327\. A&A 667, 3 (2022) arXiv:2208.04930 [astro-ph.GA]. https://doi.org/10.1051/0004-6361/202244719
  * (66) Harikane, Y., Ouchi, M., Oguri, M., Ono, Y., Nakajima, K., Isobe, Y., Umeda, H., Mawatari, K., Zhang, Y.: A Comprehensive Study of Galaxies at z 9-16 Found in the Early JWST Data: Ultraviolet Luminosity Functions and Cosmic Star Formation History at the Pre-reionization Epoch. ApJS 265(1), 5 (2023) arXiv:2208.01612 [astro-ph.GA]. https://doi.org/10.3847/1538-4365/acaaa9
  * (67) Bouwens, R., Illingworth, G., Oesch, P., Stefanon, M., Naidu, R., van Leeuwen, I., Magee, D.: UV Luminosity Density Results at z¿8 from the First JWST/NIRCam Fields: Limitations of Early Data Sets and the Need for Spectroscopy. arXiv e-prints, 2212–06683 (2022) arXiv:2212.06683 [astro-ph.CO]. https://doi.org/10.48550/arXiv.2212.06683
  * (68) Boyett, K., Trenti, M., Leethochawalit, N., Calabró, A., Metha, B., Roberts-Borsani, G., Dalmasso, N., Yang, L., Santini, P., Treu, T., Jones, T., Henry, A., Mason, C.A., Morishita, T., Nanayakkara, T., Roy, N., Wang, X., Fontana, A., Merlin, E., Castellano, M., Paris, D., Bradac, M., Marchesini, D., Mascia, S., Pentericci, L., Vanzella, E., Vulcani, B.: A massive interacting galaxy 525 million years after the Big Bang. arXiv e-prints, 2303–00306 (2023) arXiv:2303.00306 [astro-ph.GA]. https://doi.org/10.48550/arXiv.2303.00306
  * (69) Teyssier, R.: Cosmological hydrodynamics with adaptive mesh refinement. A new high resolution code called RAMSES. A&A 385, 337–364 (2002) arXiv:astro-ph/0111367 [astro-ph]. https://doi.org/10.1051/0004-6361:20011817
  * (70) Teyssier, R., Fromang, S., Dormy, E.: Kinematic dynamos using constrained transport with high order Godunov schemes and adaptive mesh refinement. Journal of Computational Physics 218(1), 44–67 (2006) arXiv:astro-ph/0601715 [astro-ph]. https://doi.org/10.1016/j.jcp.2006.01.042
  * (71) Ferland, G.J., Korista, K.T., Verner, D.A., Ferguson, J.W., Kingdon, J.B., Verner, E.M.: CLOUDY 90: Numerical Simulation of Plasmas and Their Spectra. PASP 110(749), 761–778 (1998). https://doi.org/10.1086/316190
  * (72) Rosen, A., Bregman, J.N.: Global Models of the Interstellar Medium in Disk Galaxies. ApJ 440, 634 (1995). https://doi.org/10.1086/175303
  * (73) Kimm, T., Katz, H., Haehnelt, M., Rosdahl, J., Devriendt, J., Slyz, A.: Feedback-regulated star formation and escape of LyC photons from mini-haloes during reionization. MNRAS 466(4), 4826–4846 (2017) arXiv:1608.04762 [astro-ph.GA]. https://doi.org/10.1093/mnras/stx052
  * (74) Martin-Alvarez, S., Slyz, A., Devriendt, J., Gómez-Guijarro, C.: How primordial magnetic fields shrink galaxies. MNRAS 495(4), 4475–4495 (2020) arXiv:2005.10269 [astro-ph.GA]. https://doi.org/10.1093/mnras/staa1438
  * (75) Martin-Alvarez, S., Katz, H., Sijacki, D., Devriendt, J., Slyz, A.: Unravelling the origin of magnetic fields in galaxies. MNRAS 504(2), 2517–2534 (2021) arXiv:2011.11648 [astro-ph.GA]. https://doi.org/10.1093/mnras/stab968
  * (76) Dubois, Y., Commerçon, B.: An implicit scheme for solving the anisotropic diffusion of heat and cosmic rays in the RAMSES code. A&A 585, 138 (2016) arXiv:1509.07037 [astro-ph.GA]. https://doi.org/10.1051/0004-6361/201527126
  * (77) Dubois, Y., Commerçon, B., Marcowith, A., Brahimi, L.: Shock-accelerated cosmic rays and streaming instability in the adaptive mesh refinement code Ramses. A&A 631, 121 (2019) arXiv:1907.04300 [astro-ph.GA]. https://doi.org/10.1051/0004-6361/201936275
  * (78) Farcy, M., Rosdahl, J., Dubois, Y., Blaizot, J., Martin-Alvarez, S.: Radiation-magnetohydrodynamics simulations of cosmic ray feedback in disc galaxies. MNRAS 513(4), 5000–5019 (2022) arXiv:2202.01245 [astro-ph.GA]. https://doi.org/10.1093/mnras/stac1196
  * (79) Katz, H., Liu, S., Kimm, T., Rey, M.P., Andersson, E.P., Cameron, A.J., Rodriguez-Montero, F., Agertz, O., Devriendt, J., Slyz, A.: PRISM: A Non-Equilibrium, Multiphase Interstellar Medium Model for Radiation Hydrodynamics Simulations of Galaxies. arXiv e-prints, 2211–04626 (2022) arXiv:2211.04626 [astro-ph.GA]. https://doi.org/10.48550/arXiv.2211.04626
  * (80) Hayes, M.J., Scarlata, C.: On the sizes of ionized bubbles around the highest redshift galaxies. Spectral shapes of the Lyman-alpha emission from galaxies III. arXiv e-prints, 2303–03160 (2023) arXiv:2303.03160 [astro-ph.GA]. https://doi.org/10.48550/arXiv.2303.03160
  * (81) Weinberger, L.H., Haehnelt, M.G., Kulkarni, G.: Modelling the observed luminosity function and clustering evolution of Ly-$\alpha$ emitters: growing evidence for late reionization. MNRAS 485(1), 1350–1366 (2019) arXiv:1902.05077 [astro-ph.GA]. https://doi.org/10.1093/mnras/stz481
  * (82) Tweed, D., Devriendt, J., Blaizot, J., Colombi, S., Slyz, A.: Building merger trees from cosmological N-body simulations. Towards improving galaxy formation models using subhaloes. A&A 506(2), 647–660 (2009) arXiv:0902.0679 [astro-ph.CO]. https://doi.org/10.1051/0004-6361/200911787
  * (83) Power, C., Navarro, J.F., Jenkins, A., Frenk, C.S., White, S.D.M., Springel, V., Stadel, J., Quinn, T.: The inner structure of $\Lambda$CDM haloes - I. A numerical convergence study. MNRAS 338(1), 14–34 (2003) arXiv:astro-ph/0201544 [astro-ph]. https://doi.org/%****␣Main.bbl␣Line␣2775␣****10.1046/j.1365-8711.2003.05925.x
  * (84) Hui, L., Gnedin, N.Y.: Equation of state of the photoionized intergalactic medium. MNRAS 292(1), 27–42 (1997) arXiv:astro-ph/9612232 [astro-ph]. https://doi.org/10.1093/mnras/292.1.27
  * (85) Cantalupo, S., Porciani, C., Lilly, S.J.: Mapping Neutral Hydrogen during Reionization with the Ly$\alpha$ Emission from Quasar Ionization Fronts. ApJ 672(1), 48–58 (2008) arXiv:0709.0654 [astro-ph]. https://doi.org/10.1086/523298
  * (86) Goerdt, T., Dekel, A., Sternberg, A., Ceverino, D., Teyssier, R., Primack, J.R.: Gravity-driven Ly$\alpha$ blobs from cold streams into galaxies. MNRAS 407(1), 613–631 (2010) arXiv:0911.5566 [astro-ph.CO]. https://doi.org/10.1111/j.1365-2966.2010.16941.x
  * (87) Hamilton, D.R.: On Directional Correlation of Successive Quanta. Physical Review 58(2), 122–131 (1940). https://doi.org/10.1103/PhysRev.58.122
  * (88) Dijkstra, M., Loeb, A.: Ly$\alpha$-driven outflows around star-forming galaxies. MNRAS 391(1), 457–466 (2008) arXiv:0807.2645 [astro-ph]. https://doi.org/10.1111/j.1365-2966.2008.13920.x
  * (89) Smith, A., Safranek-Shrader, C., Bromm, V., Milosavljević, M.: The Lyman $\alpha$ signature of the first galaxies. MNRAS 449(4), 4336–4362 (2015) arXiv:1409.4480 [astro-ph.CO]. https://doi.org/%****␣Main.bbl␣Line␣2875␣****10.1093/mnras/stv565
  * (90) Li, A., Draine, B.T.: Infrared Emission from Interstellar Dust. II. The Diffuse Interstellar Medium. ApJ 554(2), 778–802 (2001) arXiv:astro-ph/0011319 [astro-ph]. https://doi.org/10.1086/323147
  * (91) Henyey, L.G., Greenstein, J.L.: Diffuse radiation in the Galaxy. ApJ 93, 70–83 (1941). https://doi.org/10.1086/144246
  * (92) Yusef-Zadeh, F., Morris, M., White, R.L.: Bipolar reflection nebulae : Monte Carlo simulations. ApJ 278, 186–194 (1984). https://doi.org/10.1086/161780
  * (93) Wood, K., Reynolds, R.J.: A Model for the Scattered Light Contribution and Polarization of the Diffuse H$\alpha$ Galactic Background. ApJ 525(2), 799–807 (1999) arXiv:astro-ph/9905289 [astro-ph]. https://doi.org/10.1086/307939
  * (94) Costa, T., Arrigoni Battaia, F., Farina, E.P., Keating, L.C., Rosdahl, J., Kimm, T.: AGN-driven outflows and the formation of Ly$\alpha$ nebulae around high-z quasars. arXiv e-prints, 2203–11232 (2022) arXiv:2203.11232 [astro-ph.GA]
  * (95) Górski, K.M., Hivon, E., Banday, A.J., Wandelt, B.D., Hansen, F.K., Reinecke, M., Bartelmann, M.: HEALPix: A Framework for High-Resolution Discretization and Fast Analysis of Data Distributed on the Sphere. ApJ 622(2), 759–771 (2005) arXiv:astro-ph/0409513 [astro-ph]. https://doi.org/%****␣Main.bbl␣Line␣2975␣****10.1086/427976
  * (96) Keating, L.C., Bolton, J.S., Cullen, F., Haehnelt, M.G., Puchwein, E., Kulkarni, G.: JWST observations of galaxy damping wings during reionization interpreted with cosmological simulations. arXiv e-prints, 2308–05800 (2023) arXiv:2308.05800 [astro-ph.GA]. https://doi.org/10.48550/arXiv.2308.05800
  * (97) Blaizot, J., Garel, T., Verhamme, A., Katz, H., Kimm, T., Michel-Dansac, L., Mitchell, P.D., Rosdahl, J., Trebitsch, M.: Simulating the diversity of shapes of the Lyman-$\alpha$ line. MNRAS 523(3), 3749–3772 (2023) arXiv:2305.10047 [astro-ph.GA]. https://doi.org/10.1093/mnras/stad1523