1Indian Institute of Astrophysics, Bangalore 560034, India.
2Tata Institute of Fundamental Research, Colaba, Mumbai 400005,India.
3 Homi Bhabha Centre for Science Education (TIFR) Mumbai 400088, India.

# Planetary Nebulae with UVIT: A Progress Report.

N. Kameswara Rao1,* Sutaria F. 1 Murthy J.1 Ray A.2,3 Pandey G. 1

###### Abstract

The spectral region between 1250 $\AA$ -3000 $\AA$ contains important spectral
lines to understand the morphological structures and evolution of planetary
nebulae. This is the region sampled by UVIT through various filter bands both
in the continuum and in emission lines (e.g.. C iv, He i, Mg ii etc.). We have
mapped several planetary nebulae with different characteristics, ranging in
morphology from bipolar to wide and diffuse, and in various states of
ionization, comparing the UV with the x-ray morphologies wherever the x-ray
images were also available. The major unanticipated discovery with UVIT has
been the detection of previously undetected, cold, fluorescent, H2 gas
surrounding some planetary nebulae. This may be a possible solution to the
missing mass problem. Here we present a review of our studies so far done
(both published and on going) with UVIT.

###### keywords:

Star: AGB and post — AGB stars, winds, outflows — planetary nebulae: ISM:
Planetary nebulae: general — planetary nebulae: individual: NGC 6302.

<EMAIL_ADDRESS>
7 Nov. 2020–

12.3456/s78910-011-012-3 #### 000 0000 1– 1

##  1 Introduction

Planetary nebulae (PNs) are splendid remnants of extraordinary deaths of
ordinary stars in the mass range of 1 – 8 M⊙. They disburse the
nucleosynthetically processed stellar material like Carbon and s-process
elements into the interstellar medium, thus enriching the matter which forms
the next generation of stars. The extensive, slow, stellar wind, moving at
speeds of 10 to 15 km s-1, with a mass-loss rate of $\sim 10^{-7}$ M⊙ yr-1,
that starts on the thermally pulsing asymptotic giant branch (AGB) – double
shell (He & H) burning sources – transforms into a heavy super-wind with mass-
loss rates of $\sim 10^{-4}$ M⊙ yr-1 (Delfosse et al. 1997) as the star
evolves to the tip of AGB in the H-R diagram. In a relatively short time most
of the mass is lost through a super-wind till the envelope mass falls below
$10^{-3}$ \- $10^{-4}$ M⊙, when a structural change occurs to the star as a
degenerate CO oxygen core (which ultimately becomes a white dwarf) develops.
The photospheric radius shrinks and the effective temperature Teff starts to
increase keeping the luminosity almost constant. Consequently, the mass-loss
rate stellar wind decreases to about $10^{-8}$ M⊙ yr-1 and the wind speed
picks up to 200 to 2000 km s-1. This fast stellar wind plows into the material
that was earlier lost through super-wind generating a shock at the interface,
while the stellar radiation heats and ionizes the ejecta. The circumstellar
material starts to glow as the planetary nebula, and “illuminates the pages of
the book that tells the star’s story” (Bianchi 2012). In the interacting
stellar wind model (Kwok 1978), it the interaction of the the high speed
stellar wind and the slowly expanding super-wind material that shapes the
planetary nebulae. Presence of a companion and or magnetic fields may further
alter the morphology of the PN. In general, PNe show very many shapes ranging
from spherical to bipolar to multipolar, with some even having chaotic
geometries. Morphological studies of these objects reveal their past history
of mass ejections, their time scales, kinematics, properties of the ionizing
source, wind interactions as well as interactions with interstellar medium
etc.. The UV region is important for the study of both the central stars
(CSPNs) as well as the nebula, because the most important lines of the most
abundant elements and their ionization states like C ii 1335 Å, C iv 1550 Å,
He ii 1640 Å,N iii] 1760 ÅC ii] 2326 Åetc., fall in this region. These lines
are important for modeling the ionization structure, shocked regions, chemical
composition etc., and for the estimation of the Teff of the hot CSPNs.
Moreover, the interstellar extinction through 2179 Åbump can be studied only
in the UV band. The Ultraviolet Imaging Telescope(s) (UVIT) on ASTROSAT
(ref.), with broad and narrow band filters which cover important spectral
lines and continuum with an angular resolution of about 1”.5, over a 28’ field
of view, are well suited for the study of PNs.

Details of UVIT are provided in Kumar et al. (2012) and its in-orbit
performance is described in Tandon et al. (2017a) and in Tandon et al. (2020).
UVIT is one of the five payloads on the multiwavelength Indian astronomical
satellite ASTROSAT that was launched on 2015 September 28. It consists of two
38 cm aperture telescopes, one of which is optimized for FUV, while the other
has a dichroic beam splitter that reflects NUV and transmits the optical. Each
UV channel can be studied in five broad and narrow band filters, as well as by
low resolution transmission gratings. The Visual channel (VIS channel), which
operates only in the integration mode, is used for tracking. Our project uses
UVIT imaging of x-ray bright and x-ray faint Planetary Nebulae of different
morphologies in various UV emission lines, particularly C iv 1550 Å, C ii]
2326 Å, [O ii] 2470 Å, Si iv 1400 Å, Mg ii] 2800 Å, He ii 1640 Å etc., using
various filters of the UVIT-FUV and -NUV channels. We aim to study the UV
morphologies, shocked regions and correspondence of UV and X-ray emissions in
PNs, and to that end, several PNs of varied morphological types in both near
(NUV) and far (FUV) UV ranges have been observed. Unfortunately, the NUV
channel became dysfunctional after 2017. In this paper, we discuss our
observations conducted so far of the selected PNs (Table 1), as well as some
of the results and surprises that emerged. Detailed studies of individual
objects would be presented else where but some salient observational features
particularly brought out by UV studies are dealt in the current presentation.
Detailed discussion of NGC 40 and NGC 6302 have been presented in Kameswara
Rao (2018a,b).

Table 1 shows a broad morphological classification of the nebulae we observed
with UVIT so far which range from compact bipolar nebulae (B) to large
elliptical (E) and round (R) nebulae. Some are irregular. Figure 1 illustrates
typical nebular emission lines that are enclosed by UVIT filters that were
used for our PN studies.

Figure 1:  IUE low resolution nebular spectra of NGC6302 are shown to
illustrate the wavelength range of UVIT filters. FUV is plotted on top and NUV
at the bottom. Relative effective areas of various UVIT filters used for PN
studies and typical nebular emission lines they include are shown.

##  2 Results and Discussion

###  2.1 Bipolar Nebulae -FUV Halos and Arcs

Most of the nebulae we have observed so far belong to the group of PNe with
bipolar morphology. Our sample includes NGC 40 (the ”Bow tie nebula”), NGC
650, NGC 2440, OH231.8+4.2 (the ”Calabash nebula”), NGC 2818, Mz 3, NGC 6302
and NGC 7027. One of the reasons we observed them is to look for systematic
featufres (aspects) in the UV that would characterise the group - e.g. the
cold circumnebular H2 gas. Detail UVIT imaging studies of NGC 40 and NGC 6302
are to be found in (Kameswara Rao et al. 2018a,b), while and for NGC 2818 in
(Kameswara Rao et al., A& A, submitted). Although observations of NGC 650,
OH231.8+4.2, Mz3, (and IC 4997) have been done the data is not yet available
from ISSDC.

The compact low excitation planetary nebula, NGC 40, was the first object we
studied with a view to look for correspondence of high excitation UV line
regions with Chandra X-ray images. It has been imaged in the far-ultraviolet
filters F169M (UVIT/FUV-F3 with $\lambda_{\rm eff}=1608$ Å ) and F172M
(UVIT/FUV-F5 with $\lambda_{\rm eff}$ of 1717 Å), as well as in the near-
ultraviolet (UVIT/NUV) filters N245M (UVIT/NUV-B13) and N279N (UVIT/NUV-N2
with $\lambda_{\rm eff}$ of 2792 Å). The filters selected would allow imaging
in C iv 1550Å (F169M) and C ii] 2326Å (N245M) emission lines, as well as in
the continuumn (F172M) and (N263). Morphological studies in optical and
infrared (IR) show that NGC 40 has ionized high density central core
surrounded by faint filamentary halo with circumnebular rings that are seen
only in H$\alpha$ but not in [O iii]. UVIT studies show that C ii] 2326Å
emission is confined mostly to the core and shows similar morphology as low
excitation lines in optical. However, strong C iv 1550Å emission is present in
the core and shows similar morphology and extent as that of X-ray (0.3-8 keV)
emission observed by Chandra, suggesting interaction of the high-speed wind
from WC8 central star (CS) with the nebula. An unexpected UVIT discovery is
the presence of faint large emission halo in FUV F169M surrounding the central
core (Figure 2-top). This FUV halo is absent in the other filters. This
emission halo is unlikely to be due to C iv 1550Å emission, or due to dust
scattering. Instead, it most likely is due to UV fluorescence emission from
Lyman bands of H2 molecules since a few vib-rotational lines have already been
detected in the IR from Spitzer spectra. The FUV halo in NGC 40 highlights the
extensive existence of cold H2 molecules in the regions even beyond the
optical and IR halos. Thus UV studies are important to estimate the amount of
H2, which is probably the most dominant molecule and significant for mass-loss
studies. Central star and the nebular core occur in the north-west edge of the
FUV halo in the direction of the star’s proper motion vector suggesting a
possible interaction with the surrounding interstellar medium (ISM).

Figure 2: (Top:) FUV images of NGC 40 in F172M (left) and in F169M (right).
The faint FUV halo in F169M, extending beyond the bright central region, is
absent in the F172M image. (Kameswara Rao et. al 2018a). (Bottom:) The
extensive FUV lobes and jets in NGC 6302 are shown in the F169M image which
extends much beyond the optical image. The F172M image (not shown) does not
show these lobes and jets.

Presence of much bigger and more extensive FUV halo was discovered around the
famous high excitation PN, NGC 6302 the butterfly nebula (Kameswara Rao et al.
2018b). It has been imaged in F169M and F172M, as well as in N279N and in
N219M (UVIT/NUV-B15 with $\lambda_{\rm eff}$ of 2196 Å).

Figure 3: (Top) :NUV N219M image (left) is compared with UVIT image in F169M
(F3) of NGC 2440.

Figure 4: Top left panel: Images of NGC 2440 in the filter F169M (left) is
shown along with [O iii] 5007Åobtained with HST. The FUV halo and jet are
indicated in UVIT image. In the right panel the same image is shown with the
three bipolar orientations (PA 35∘ (a) and 85∘ (b) are shown. Bottom left
panel shows UVIT image of NGC 2440 in F172M shown along with HST image in [N
ii] 6584Å. The bottom right panel shows the UVIT image in N265M compared with
the HST image in [N ii] 6584Å.

Very detailed Hubble Space Telescope (HST) images have been discussed by
Szyska et al. (2009) who also identified the elusive central star. The optical
narrow band images show two main lobes with complicated clumpy small scale
structure in the east-west direction separated by a dark lane of a very dense
disc of gas (neutral and molecular) and dust, stretching to north-south. It
formed into a toroid, that obscures the central star with visual extinction of
about 8 magnitudes (Matsuura et al. 2005, Peretto et al. 2007, Szyska et al.
2009 , Wright et al. 2011) . Meaburn et al. (2008) determined the distance to
the nebula as 1.17$\pm$0.14 kpc from expansion parallax using proper motions
of features in the north-west lobe. This estimate seems to be consistent with
measurements of proper motions from Hubble images of the eastern lobe (Szyszka
et al. 2011). From 3D photoionization modelling of the nebula Wright et al.
(2011) derived the properties of the central star as hydrogen deficient with
Teff of 220000 K , log $g$ of 7 , L∗ of 14300 L⊙and mass of 0.73-0.82 M⊙. They
also estimated the initial mass to be around 5.5 M⊙ .

Extensive studies of the circumstellar torus from infrared to radio
wavelengths ( Lester & Dinerstein 1984, Kemper et al. 2002, Matsuura et al.
2005, Peretto et al. 2007, and Santander-Garcia et al. 20017) suggest the
structure is that of a broken disc containing 2.2 M⊙ of dust and molecular gas
expanding at 8 km s-1, presumably ejected from the star some 5000 years ago,
over a duration of $\sim 2000$ years. The torus also obscures both the star
and an ionized gas disc (detected in 6 cm free-free continuum) around the
star. Kinematical studies of the east and west lobes seem to suggest that an
explosive event initiated a kind of Hubble flow (i.e. a flow in which the
velocity increases outward in proportion to its distance from the star) in
both lobes about 2200 years back (Meaburn et al. 2008, Szyszka et al., 2009).
The formation and flow of matter probably was directed by the torus into east
- west lobes.

Our F169M image of this nebula shows faint emission lobes that extend to about
5’ arc minutes on either side of the central source. Faint orthogonal jets are
also present on either side of the FUV lobes through the central source
(Figure 2-bottom). These lobes and jets are not present in either of the two
NUV filters or in FUV F172M. Optical and IR images of NGC 6302 show brightly
emitting bipolar lobes in the east-west direction with a massive torus of
molecular gas. Dust is seen as a dark lane in the north-south direction. FUV
lobes are much more extended and oriented at a position angle of 113∘. The FUV
lobes and jets might be remnants of earlier (binary star) evolution, prior to
the dramatic explosive event that triggered the Hubble type bipolar flows
about 2200 years back. The source of the FUV lobe and jet emission is not
known, but most likely is due to fluorescent emission from H2 molecules. The
cause of the difference in orientation of optical and FUV lobes is also
indeterminate, although we speculate that it could be related to the binary
interactions.

####  2.1.1 NGC 2440:

A different kind of FUV halo is seen in the bipolar (multi-polar) PN NGC 2440
in our UVIT observations. The two prominent lobes of bipolar structure
prominently seen in the optical images (eg. HST heritage image) are resolved
in the various nebular line filter images in to at least two interlocking,
differently oriented, bipolar structures (Lopez et al. 1998). They are
oriented at position angles (PA) of 35∘ and 85∘, with a third one at 60∘
(Lopez et al. 1998). These multipolar structures suggest changes in the
direction of sporadic mass outflows from the central object (Lopez et al.
1995, Manchado et al. 1996). Many molecular emissions and outflows have have
been mapped. Mapping of H2 ($v=1-0$ S(1)) rotational transition shows a spiky
spherical structure of $\sim 73"$ diameters (Muthu Mariappan et al. 2007, Wang
et al. 2008) with spokes emanating from the centre. CO (3-2) emission closely
follows the PA 35∘ bipolar axis in three clumps extending to about a radius of
$\sim 36"$ from the central clump (Wang et al. 2008). HCN, HCO+ emission is
also detected within the nebular diameter of $\sim 71"$ (Schmidt & Ziurys
2016). Cuesta & Phillips (2000) analysed and modeled the optical nebular line
filter images. Ramos-Larios & Phillips (2009) show the Spitzer images at 3.6,
4.8, and 8 $\mu$ infra-red emission extending to $\sim 80"$ diameter centered
on the central source where two bright nebular knots (NK and SK) separated by
$\sim 6.2"$ occur and define another axis. Thus the, ionized, molecular gas
and dust are all confined within $\sim$80” diameter centered around the
centre. Logo & Costa (2016) modeled the morphokinematical structure with two
bipolar components with PA 35∘ and 85∘. The nebular abundances and the central
star properties have been studied recently by Miller et al. (2019).

Figure 5:  UVIT/FUV F154W image of NGC 2818 shows a faint, narrow, nebular,
partial ring like feature about 370” east of the nebula and also two nebular
arcs at about 170” north-west of the nebula (figures on the right). These
features are absent in F172M (top, left) and GALEX NUV (bottom, left) images.
Figure 6:  UVIT/FUV F169M image of NGC 2818 is compared with [O iii] 5007 Å
ground based, image (inset, Vazquez, 2012). While several features are in
common, a major difference is the prominence of radial streamers (or emission
filaments) in the F169M image, marked by green arrows. The bandpass of F169M
filter covers mainly He ii $\lambda$1640 Å, and C iv $\lambda$ 1550 Å emission
lines. Presence of these streamers suggest that they might have been swept up
by strong stellar wind from the central star.

Our UVIT images are obtained in the FUV filters F169M and F172M as well as in
the NUV filters N219M, N245M and N263M (Figure 3). F169M includes the lines of
C iv 1550 Å, He ii 1640 Å close to the star whereas F172M mostly displays the
continuum and a weakly, the N iii] 1760 Å emission feature. The images of
N245M includes C ii] 2326 Å, N263M Mg ii and the continuum. Comparison of UV
images with optical nebular lines ground based (Lopez et al. 1998, Cuesta &
Phillips 2000) and HST show that N245M and N263M are very similar to[N ii]
6584 Åwhere as F172M image is similar to that of continuum emission (Cuesta &
Phillips 2000) both in size as well as in the presence of the features
consistent with low excitation line contribution. However, the images obtained
with F169M differ from those of the other UV filters and the optical lines.
The bright central part of the image shows broadly similar to the [O iii] 5007
Åimage and shows the two bipolar systems at PA 35∘ and 85∘ (Figure 4 ). The
orientation of the central knots also is similar.

The most intriguing features of the F169M image are the faint halo extending
beyond the central bright nebula in the north-east (NE), and to a lesser
extent, on the south west (SW). The faint halo extends beyond the $\sim 80"$
nebular diameter estimated from dust and molecular emission. It extends to
$\sim 38"$ beyond the bright nebula on the NE side and $\sim$18” on the SW.
The axis of this halo seem to coincide with PA 35∘ nebular axis. In addition,
the most interesting is a thin jet that extends to $\sim 44"$ to the south
west beyond the nebula, parallel to the PA $35^{\circ}$ axis. (the bright
condensation at the southern end of the jet is a field star. It is also
present in the F172M image). The FUV halo in NGC 2440 is similar in nature to
the other two systems NGC 40 and NGC 6302 and most likely caused by the
fluorescent emission from cold H2 molecules, excited by the diffuse UV
radiation of the hot central star. This cold H2 might be a product of much
earlier mass loss from the system when it (or possibly, the primary) was on
early AGB phase. The FUV jet might also be an earlier ejection from the binary
system.

####  2.1.2 NGC 2818:

The bipolar PN NGC2818 presents a different kind of FUV emission. Instead of a
FUV halo around the PN, NGC 2818 shows FUV emitting circum-nebular arcs at a
distance from the nebula, possible remnants of much earlier mass ejections and
mass-loss.

The PN NGC 2818 is one of the few known PNs that are members of galactic
clusters which makes it possible to estimate a lower limit to the original
main sequence mass from the cluster turnoff. In the cse of NGC 2818 it is
around 2.0 to 2.2 M⊙. NGC 2818 is a high excitation nebula with lines of He
ii, C iv, N v same time strong lines of low excitation as well as vibrational-
rotational lines of H2 in the near and mid-IR. The Spitzer images in mid-IR
wavelengths show dust emission extending beyond the optical nebula,
particularly on the western lobe (Hora 2007). From the optical spectral
analysis the Teff of the central star is estimated to be $\sim$ 169000 K (Mata
et al. 2016). Very detailed Hubble Space telescope (HST) images (Hubble
Heritage image collection) have been discussed by Vazquez(2012) along with its
kinematical structure. The kinematical age of the wide lobes is estimated as
$\sim$ 8400$\pm$3400 years. The optical narrow band images show bipolar lobes
in the east-west direction with complicated small scale structure and a
pinched, hourglass type narrow equatorial waist in the middle stretching to
north-south. The semi-major axis is estimated to extend to 75” through optical
nebular lobes in east-west and a minor axis extending to 55” north-south with
14” diameter central region, which is potentially the remnant of an equatorial
enhancement A number of cometary knots are seen in images of low excitation
lines eg. [N ii], that are preferentially located inside a radius of 20”
around the central star Vazquez(2012).

Figure 7: (Top):FUV F154W,F169M and F172M images of NGC 7027. Note that the
south-east part is fainter and affected by extinction. FUV is very sensitive
to dust extinction. The differential extinction can be studied from UV images.
Figure 8:  (Bottom): FUV F154W image (left) is shown along with the x-ray
(Kastner et al. 2001) and HST optical image. The faint circular rings seen the
optical image are absent in FUV image.

Figure 9: Top: FUV UVIT F169M (left),N245M and N263M (right) images of NGC
1514. The nebula is brighter in NUV N245M than in FUV F169M. Bottom: The UVIT
N245M image of NGC 1514 is compared with optical image (bottom right)
(Resseler et al. 2010). The UV emission is confined to the inner ring and
centered around the central star.

The bipolar planetary nebula, NGC 2818 and the open cluster have been imaged
in three far-ultraviolet (FUV) filters , F154W: $\lambda$eff of 1541, F169M :
$\lambda$eff of 1608 and F172M: $\lambda$eff of 1717 with UVIT. The F154W
image shows faint emission of a partial nebular ring and couple of nebular
arcs (shell) that surround the central nebula at a distance of 370” and 170”
from the central star (Figure 5). F169M image also shows traces of these
features but not as prominently as in F154W image. But the images in F172M
filter, NUV from GALEX and optical filters do not show any trace of these
emission features. The FUV emission from partial ring at a distance of 6.4 pc
from the star suggests an ejection that took place about 60000 years back (or
more) from the central star. The observed expansion velocity of 105 km s-1 of
the polar lobes and the distance of 3.56 kpc determined from Gaia parallaxes
for both the cluster and the nebula suggests such an age. This is by far the
most distant and oldest relic of mass ejection observed for a planetary
nebula. The FUV emission in these nebular features is most likely due to UV
fluorescent H2 molecules. From the Teff and luminosity of the star it appears
that enough stellar UV radiation reaches the nebular arc to produce sufficient
H2 fluorescence. The original formation of the shell (or a ring) might have
involved shocks or high temperature and high velocity gas, but in due course
that gas has recombined and cooled to the present cold molecular gas.

The FUV images of the central bipolar nebula show bright emission region
dominated by He ii $\lambda$1640 and to lesser extent C iv $\lambda$ 1550
emission, around the star. Another prominent morphological aspect of FUV
emission, particularly seen in F169M image is the presence of radial filaments
(Figure 6) diverging from the central star in almost all directions. These
filaments are spread more in the direction of eastern lobe than towards
western lobe. They extend to about 48” into eastern lobe. These filaments are
much more prominent in F169M image than in [O iii] or F172M images, suggesting
that they represent He ii ( and C iv ) line emitting regions. The filaments
have a width of about 0.065 pc at the distance of the nebula. This structure
of the filaments is very similar to the radial rays surrounding the main ring
in Helix nebula as shown by O’Dell (2004) . These radial filaments seem to
provide channels for the hot stellar wind to flow.

It is amazing that FUV studies could bring out relics of 60000 years past
mass-loss from the pre-CSPN star of NGC 2818.

Figure 10: (Top:) PN A30 in various UVIT FUV and NUV filters is shown in the
top panel. (Bottom:) The UVIT/FUV F169M image of PN A30 (left) is compared
with ground based [O iii] image (right). The Knots and cometary-tail like
filaments in the centre of the [O III] image appear to have counterparts in
the F169M image. The [O iii] image was supplied by Arturo Manchado (personal
comm.).

####  2.1.3 NGC 7027:

Although our analysis of this PN is on going, we illustrate here F154W, F169M
and F172M filters image (Figure 7) from our observations and point out some
interesting features. NGC 7027 (PN G084.9-03.4) – also known as the ”Magic
carpet” nebula or ”Pink pillow” nebula – is located at 1 kpc (Zijlstra et al.
2008) and has a kinematical age of just 600 years (based on its radio flux -
Masson 1989). It is a compact and young PN, one of the brightest nebulae in
the sky and the most extensively studied one. NGC 7027 is a carbon-rich nebula
with a very high-excitation spectrum showing lines of O iv, Mg V etc. It hosts
one of the hottest central stars known to date, with a Teff $\sim 200000$ K
(Latter et al. 2000). A small, essentially ellipsoidal, expanding ionized
shell surrounds the central star (Masson 1989). Further outwards, a thin shell
indicates the presence of H2 a photo-dissociation region (PDR) and shows signs
of recent interaction with collimated outflows (Cox et al. 2002). The nebula
also shows many molecular emission lines, e.g. lines of CO, CH+, H2O, and even
HeH+ ion have been detected from beyond the PDR (Wesson et. al 2010,
Santander-García et al. 2012, Gusten et ai. 2019).

Figure 11: (Top, left): A30 image in F169M showing radial streamers from CSPN
showing channels of streaming stellar wind (green arrows). The pink arrows
point to the arches where the channeled flow hit the outer boundary. (Right):
Ground based [O iii] image superposed by an inset showing the region of
Chandra X-ray emission (Guerrero et al. 2012). (Bottom): Image of A30 F169M
superposed by the XMMNewton X-ray continuum counters.  Figure 12:  Images of
A30 in F154W , F169M and F172M showing the FUV halo around F154 and F169M
images and the absence of it around F172M image.

The PN was discovered to be an X-ray source by Kastner et al. (2001), who
attributed the X-ray emission to shock heating by a fast wind from the central
star impacting the slow wind which the progenitor star ejected while on the
asymptotic giant branch (AGB). Zhang et al. detected in the spectrum of this
bright young PN of Raman-scattered O vi features at 6830Å and 7088Å pointing
to the existence of abundant neutral hydrogen around the ionized region

FUV is very sensitive to the internal and external extinction. NGC 7027 has
high and variable extinction across the nebula that has been mapped by Walton
et al. (1988). Montez et al. (2018) link the X-ray emission to the
distribution of extinction across the nebula. UVIT images in FUV would reflect
such extinction variations (Figure 8) that would explored later. UVIT images
do not show presence of FUV halo or arcs as in other bipolar PNs listed
earlier although deep images in optical (HST) do show faint circular rings
around the main nebula. One possible reason is that because of high internal
extinction no UV photons from the central star reach to the outer H2 region.

###  2.2 Round Nebulae -FUV Halos

The members of this group that were observed by UVIT are NGC 1514, A 30 , EGB
6, and NGC 3587

####  2.2.1 NGC 1514:-shining fluid!

Observing NGC 1514 on 1790 November 13, William Herschel called it ‘a most
singular phenomenon!’.This PN is unusual because of its very bright central
star and large diameter low surface brightness nebulosity. The observation by
Herschel is termed as ‘an important event in the history of astronomy’ (Seaton
1980) because of his realisation that ‘we therefore either have a central body
which is not a star or have a star which is involved in a shining fluid, of a
nature totally unknown to us’ (Seaton 1980). It turns out that there is not
one star at the centre but two, a sdO + A0III. Recent observations show that
the binary system has a period of 3306 days and eccentricity of 0.46. The
estimates of the mass for the cooler secondary is about 2.3 M⊙ and the hot
primary is of 0.9 M⊙ (Jones et al. 2017).

Ressler et al. (2010) described the morphological structure of NGC 1514 (see
their figure 1) as a nebula with two shells, inner and outer with diameters of
132” and 183”. The inner shell has numerous bubble structures at its edge
pushing into the outer shell. The monochromatic optical images of NGC 1514
show that the amorphous appearance of the nebula contains very little nebular
emission within about 30” of the nucleus (Balick 1987). This is also confirmed
by the absence of C iii ] $\lambda$1909 emission which is normally the
strongest nebular feature in IUE spectra of PNe (Ressler et al. 2010).

A pair of infrared bright axisymmetric rings that surround the visible nebula
were discovered by Ressler et al. (2010), particularly dominant in 22 $\mu$ m.
Such a structure is not suggested in any of the visible wavelength images
which is probably resulted from binary interaction. NGC 1514 is also a X-ray
source (Tarafdar & Apparao 1988, Montez et al. 2015).

We have obtained UVIT images in F154W, F169M, F172M as well as in N245M,
N263M, and N279N. Although our analysis is ongoing and not complete ,we
present few images and show the comparison with the optical image (a
combination of B, V, R+I -Resseler et al. 2010) in Figure 9. The UV emission
seem to be mostly to the inner shell. There is UV (nebular) emission within
30”. The nebular extent in FUV is less than that in near UV and optical. There
seems to be streams connecting the central region to the inner shell
particularly in F245M. The structure in NUV F245M is very similar to the
optical except the bubbles look sharper.

####  2.2.2  Born-again Planetary Nebula A30 -

Abell 30 (PNG208.5+33.2, A30) is archetypal born-again PN of about 2 arc
minute diameter. The central star of A30 is believed to have undergone a very
late thermal pulse (VLTP) that caused the ejection of hydrogen deficient
material, prominently seen in the light of [O iii] lines, about 850 years
back. The inner parts of the nebula are filled with this material whereas the
outer rim of the nebula is of H-normal composition and of about 12500 yrs of
age. A30 is also an X-ray source showing both a diffuse source covering the
inner few arc seconds covering the hydrogen deficient knots and a point source
located on the central star.

Figure 13:  Top: Images of NGC 3587 (Owl Nebula) in F169M and Galex NUV
showing the halos around the deep images (marked as (a)). The nebula in F169M
and Galex NUV with two shells are shown marked as (b). Ground based H$\alpha$,
[N ii] and [O iii] images (from Garcìa-Dìaz et al. 2018) are shown for
comparison with UV images. The features of F169M and Galex NUV are similar to
[O iii] and H$\alpha$ respectively. Bottom: Image of NGC 3587 in F154W (left)
and F169M (right). F169M image shows a jet like feature (shown by the arrow)
that is absent in F154W image.

Born-again planetary nebulae (PNe) are believed to have experienced a VLTP
(Iben et al. 1983) while the star was descending the white dwarf cooling
track. During this event, the remaining stellar helium envelope reaches the
critical mass required to ignite its fusion into carbon and oxygen (e.g.,
Herwig 2005; Miller Bertolami & Althaus 2006; Lawlor & MacDonald 2006); the
sudden increase of pressure leads to the ejection of the newly processed
material and, as the stellar envelope expands, its temperature decreases and
the star returns in the Hertzsprung–Russell (HR) diagram to the locus of the
asymptotic giant branch (AGB) stars. Soon after, the contraction of the
envelope will increase the stellar effective temperature, boosting the UV
flux, and giving rise to a new fast stellar wind. So far, the only bona fide
born-again PNe are Abell 30 (A 30), Abell 58 (A 58, Nova Aql 1919), Abell 78
(A 78), and V4334 Sgr (the Sakurai’s object). Among them, A30 and A78 are the
more evolved ones, with large limb-brightened, H-rich outer nebulae
surrounding the H-poor, irregular-shaped structures that harbor the “cometary”
knots in the innermost regions (Jacoby 1979; Hazard et al. 1980, Meaburn &
López 1996; Meaburn et al. 1998). HST images in the [O iii] emission line of
the central regions have revealed equatorial rings (ERs) and compact polar
outflows (POs) in the central regions of both PNe (Borkowski et al. 1993,
1995). The dynamics are revealing: while the outer nebulae show shell-like
structures expanding at velocities of 30 to 40 km -1, the H-poor clumps
present complex structures, with velocity spikes of 200 km -1 (Meaburn & López
1996; Chu et al. 1997; Meaburn et al. 1998). The morphology and kinematics of
the H-poor knots unveil rich dynamical processes in the nebulae. The material
photo-evaporated from the knots by the stellar radiation is swept up
downstream by the fast stellar wind, which is otherwise mass loaded and slowed
down (Pittard et al. 2005). The interactions are complex, resulting in
sophisticated velocity structures, as well as x-ray emitting hot gas (Chu $\&$
Ho 1995; Guerrero et al. 2012; Toalà et al. 2014).

Figure 14:  Top, 3 Panels :UVIT image of EGB 6 in F148W filter showing the
fainter outer nebula and smaller central nebula (shown by the arrow) along
with an optical image of EGB 6 in H$\alpha$ and [N ii] (Jacoby et al. 1995)
and an optical colour image of the outer nebula from Don Goldman
(astrodonimaging.com). Note that the inner smaller neb is not present in the
two optical images. Bottom: Galex FUV image of EGB 6 (left) is compared with
UVIT image in F148W. The inner small nebula is shown by the arrow. Note the
absence of inner small nebula in the Galex image.

Figure 15:  Top, 2 Panels: UVIT image of EGB 6 in F154W filter showinging the
fainte outer nebula and smaller central nebula along with F148W image of the
outer nebula. Note that an inner, smaller, nebula is present in the two FUV
images. Bottom: FUV image of EGB 6 in F148W. Note that the bow of inner small
nebula is towards south-west direction.

To study the correspondence of UV emission with the X-ray emission as well as
the hydrogen deficient ejecta, we imaged A30 with UVIT in 3 FUV and 2 NUV
filters. Two FUV filters, F154M (F2) and F169M (F3; $\lambda_{\rm eff}$ 1608
Å) transmit the high excitation lines of He ii, C iv etc. as shown in fig. 1).
The other FUV filter F172M (F5 with $\lambda_{\rm eff}$ 1717 Å) allows mostly
the nebular continuum. The NUV filters N219M (B15 with $\lambda_{\rm eff}$
2196 Å) and N279N2 (N2 with $\lambda_{\rm eff}$ 2796 Å) allow mostly low
excitation lines or continuum. The images of the nebula in these filters are
shown in Figure 10. The nebula is most intense in F169M and F154W where He ii
line emission dominates. The UVIT provides a spatial resolution of $\sim
1."3$. In the present work, we contrast the UV images with both X-ray contours
as well as ground based [O iii] and H-alpha images (Arturo Manchado -personal
communication). In the FUV F2, F3 images, the hydrogen deficient nebular knots
are not as conspicuous as in the [O iii] image (Figure 10). The FUV F2, F3
show radial streamers, which are quite prominent almost extending from central
region (Figure 11) to the edge of the nebula. They provide the channels for
the material photoevaporated from the knots by the stellar radiation is swept
up downstream by the fast stellar wind, which is otherwise mass loaded and
slowed down (Pittard et al. 2005). At the edge of the channel where it
interacts with the nebular boundary, arch type structures are seen suggesting
that the boundary is being pushed out by the flow of stellar wind swept
material. X-ray emission has been detected within A30 (e.g., Guerrero et al.
2012; Kastner et al. 2012; Montez et al. 2015). This born-again PN has been
studied with ROSAT (PSPC and HRI), Chandra, and XMM-Newton X-ray satellites
(Chu & Ho 1995; Chu et al. 1997; Guerrero et al. 2012). Its X-ray emission
originates from the CSPN, but there is also diffuse emission spatially
coincident with the cloverleaf-shaped H-poor structure detected in [O iii].
The X-ray emission from both the CSPN and the diffuse extended emission is
extremely soft. The XMM/Newton x-ray continuum contours (Chu et al. 1997) are
shown in Figure 11 superposed on F169M image. They are confined mostly to the
inner nebular region where the He ii dominated gas is present. The Chandra
X-ray region is displayed in Figure 11 as an inset displaying the HST image of
the inner 10” radius of the nebula. The X-ray region contains both diffuse
emission and knots.

####  2.2.3 FUV Halo:

The most surprising result of our UV imaging of A 30 is the presence of a FUV
halo in the F154M and F169M filters, extending beyond the known optical and
NUV nebular size (Figure 12). The halo is not present in the F172M image, nor
in any of the NUV images or even in the optical images. This situation is
similar to that in NGC 40, NGC 6302 and NGC 2440. The FUV emission is very
likely, the result of H2 molecular fluorescent emission from the AGB ejecta,
from molecules excited by the diffuse UV radiation from the CSPN seeping
through to the cold molecular region. Inspite of the presence of a very hot
central star, with Teff of 115000 K (Toalà et al. 2014 ), and an earlier
excursion to hot PN stage (born-again), the nebula seems to still possess some
unionized molecular gas. Is this gas a survivor of 12000 years of the PN
evolution? The FUV halo seem to be distributed asymetrically only on one side
of the nebula. Earlier, Dinnerstin & Lester (1989) discovered an infra-red
disk inside the nebula. A possible connection of this dust disk to the FUV
halo needs to be explored.

Figure 16: Top left panel: Images of A 21 in H$\alpha$ (Manchado et al. 1996)
and in N263M showing the similarity of the filamentary structure. right panel:
The FUV images in F169M and F172M. The arrow points to the faint filament that
connects to the CSPN. Bottom: UVIT composite image of A 21 in three colours
F169M (blue) N263M (green) N245M(red).

####  2.2.4  NGC 3587 -The Owl Nebula

This is a well studied PN with an angular size of $\sim$3’ and of symmetrical
morphology consisting of triple shell structure with a round double shell
which forms the main bright nebula, and a faint outer halo (Chu et al. 1987;
Kwitter et al. 1992, Guerrero et al. 2003). The bright inner shell is about
$182"\times 168"$ and resembles the face of the owl with each eye being of
$\sim 35"$. The outer shell is almost circular with a diameter of $\sim 208"$.
The outer shell is about 25% larger than innershell. The surface brightness of
the outer shell decreases outward in H$\alpha$ and [O iii]. It shows a limb
brightening along the PA -15∘ to 13∘ and in PA 180∘ to 230∘ (Custeo et al.
2000).

The halo is prominent in [O iii] images than in H$\alpha$ or [N ii] but is
present in all the optical images (Hajian et al. 1997). This behavior is also
common to other PN halos and is most likely an effect of the hardening of
ionizing radiation (Guerrero & Manchado 1999). At the faintest level the halo
is circular with a radius of 350” (Guerrero et al. 2003) although overall
morphology is asymmetrical (Figure 13). The halo is kinematically independent
of the main nebula (Chu et al. 1998). The relative line strength in the halo
are also different from the main nebula. The [N ii]/H$\alpha$ ratio of the
halo is a factor of 4 higher than the other parts of the main nebula which
indicates that the halo is photo- ionized. The morphology of the halo suggests
an interaction with the surrounding interstellar medium and the gas in the
halos is ionized by stellar UV radiation leaking through the material of the
main nebula(Guerrero & Manchado 1999, Guerrero et al. 2003)

IUE spectra obtained 1.5’ away from the central star, almost into the halo,
still show weak He ii 1640Å and C iii] 1909ÅṪhe halo gas is clearly ionized
but of low density. The hot CSPN with $T_{\rm eff}=104000$ K and
$\log_{g}=7.0$ shows weak stellar wind (Werner et al. 2019, García-Díaz et al.
2018). A detailed spatiokinematical study was presented by García-Díaz et al.
(2018), who treat the Owl kind of nebulae as a seperate class. One of the
puzzles presented by the Owl is the existance of cavities (the eyes of the
owl) and how are they maintained. At a Gaia distance of 880 pc the halo
extends to 0.4 pc from the central star. Halo expansion velocity is assesed as
about $10$ km -1 (Guerrero et al. 2003) which suggests an age $>40,000$ years.
The time scales indicate that the main nebula consists of super-wind from AGB
phase and the faint halo from an early AGB wind.

Our observation with UVIT consists of FUV images in F154W, F169M, and F172M.
We coupled these with the NUV image from GALEX (GI6-015012-PK148p57d1pp-nd-
int), and compare them with image in the optical narrowband H-$\beta$ and N ii
filters. Images in all filters show the same general features as in the
optical – i.e.. the two shells, and halo. However, the cavities (the eyes) are
not as prominent in the FUV as in optical. Moreover, the NUV image shows a
sharp wiggly boundary on the north-east showing the interaction with ISM in
the direction of motion. The south western side is more diffuse and faint but
more extended than NE. The FUV F169M image possibly dominated by He ii
emission, shows a more diffuse but brighter halo that extends all around the
outer shell similar to NUV. The asymmetrical distribution of the halo does
suggest interaction with ISM.

One of the special features seen in the F169M image is a jet in the north-west
cavity (see Figure 13) that is not seen either in F154W or F172M or even NUV
images. This could be a hot He ii emitting jet, a real sign of activity in a
docile nebula.

####  2.2.5 EGB6:

EGB 6 (PN G221.6+46.4) is a large ($13^{\prime}\times 11^{\prime}$) and very
low-surface-brightness planetary nebula, serendipitously discovered by Bond on
POSS prints in 1978. The central star, PG 0950+139 is a very hot DAOZ white
dwarf with $T_{\rm eff}=105000\pm 5000$ K, $\log_{g}=7.4\pm 0.4$ (Werner et
al. 2018). The CSPN has an apparent cool dwarf companion shrouded in dust at a
separation of 0.”16, which was initially detected through near infrared
excesses (Bond et al. 2016). Initial spectroscopic observations showed the
central star has strong [O iii] emission. Later Liebert et al. (1989) showed
that the strong [O iii] nebular lines arise from a compact emission knot
(CEK), which is unresolved and appears to coincide with the PNN in ground-
based images. However, recent HST observations (Bond et al. (2016)) showed
that even the emission knot is associated with a companion at 0.”166 away from
the CSPN. This corresponds to a projected linear separation of $\sim$118 AU,
for a nominal distance of about 725 pc. The electron density of the CEK is
remarkably high, about $2.2\times 10^{6}$ cm-3, according to an emission-line
analysis by Dopita & Liebert (1989).

Thus, EGB 6 raises several astrophysical puzzles, including how to explain the
existence and survival of a compact dense [O iii] emission nebula apparently
associated with a cool M dwarf, located at least 118 AU from the source of
ionizing radiation (Bond et al. 2016). It is to be noted that very weak [O
iii] $\lambda$5007 emission attributed to the large PN has been detected
serendipitously in the SDSS spectra of two faint galaxies that happen to lie
behind EGB 6 (Yuan & Liu 2013). Acker et al. (1992) list the relative
intensities of H$\alpha$, H$\beta$, and 5007Å.

Bond et al. (2016) suggest a scenario in which the EGB 6 nucleus is descended
from a wide binary similar to the Mira system, in which a portion of the wind
from an AGB star was captured into an accretion disk around a companion star;
a remnant of this disk has survived to the present time and is surrounded by
gas photoionized by UV radiation from the WD.

Our UVIT observation include imaging EGB 6 in F148W, F154W, F169M and F172M
filters. The low surface brightness PN is present in all the filters with
about same dimensions and appearance as the H$\alpha$ and [N ii] images
(Jacoby et al. 1995). The south-west part of the nebula is the brightest and
even the F148 image shows wavy appearence which coincides with proper motion
direction of the star.

The most interesting and unique structure that is only present in FUV filters
F148W, F154W and F169M is a smaller nebula close to the CSPN extending to
about 2.’4 away from it. It has a bow like appearence away from the central
star (Figures 14, 15) in the general direction of proper motion of the star.
This central nebula is not even present in Galex image. The existence of this
small nebula adds a new puzzle to the already listed ones by Bond et al.
(2016).

###  2.3 Elliptical Nebulae

The members of this group from Table 1 are A 21, Jr Er 1, LoTr5, A70 ,Hu 1-2
and NGC 7293. Reduced level 2 data of LoTr5,, Jr Er1, A 70, Hu 1-2 is not
available. We present the results on thee PNs A21, and NGC 7293 in the
following sections.

####  2.3.1  Abell 21, Medusa Nebula, A21:

A21 (PNG205.1+14.2) is a very wide (685” x 530”) evolved PN with a very hot
white dwarf central star WD0726+133 also known as YM29. The Teff and log g of
the CSPN are estimated to be 140000 K and 6.5 respectively.

The WD central star appears as a point source superposed on diffuse emission
in the MIPS 24$\mu$m image (Chu et al. 2009). The flux density in the MIPS
24$\mu$m band is almost three orders of magnitude higher than the expected
photospheric emission. However, WD 0726+133 remains as a puzzle since no
companion has been detected (Ciardullo et al. 1999). The IR excess is
attributed to a dust disk. The orgin of the dust is unclear whether it is
accreted material or remnants of the dusty AGB phase. Whether the star is a
binary is also a possibility (Clayton et al. 2014). A21 shares this property
with JrEr 1 and NGC 7293.

Short exposure UVIT observations have been obtained in F169M and F172M in FUV
and N263M and N245 in NUV filters. The central star as expected is
conspicuous. The images are very similar to the optical ones. The NUV images
show great similarity to H$\alpha$ image with a large number of filaments
(Figure 16). However the FUV images look more diffuse similar to [O iii]
$\lambda$5007 image (Manchado et al. 1996). The F169M (includes He ii 1640Å
and C iv 1540Å ) image shows a faint filament connecting the central star.
However better observations are required.

Figure 17:  NUV image of NGC7293 in N245M (left) compared with Galex NUV
image. Image in N263M (right)is again compared with NUV Galex image of NGC
7293. Note the highier spatial resolution of UVIT images and the radial
filments.

Figure 18:  Top, 2 Panels: UVIT image of NGC 7293 in F169M filter (red)
showing the outer nebula and the He ii filament (marked by arrow) connecting
the central region (and the star). The top right panel shows the absence of He
ii filament in the N245M image. Bottom 2 Panels: Inner 4’ regions of NGC 7293
in F169M (left) and F172M (right) superposed with intensity contours. The He
ii filament is seen in the F169M image (marked by arrow) where as it is absent
in the F172M image.  Figure 19: A surface and contour study of NGC 7293 in
UVIT/FUV F169 and F172M bands. Top: Surface contours of the central source in
F169 (left) and F172M (right) showing distored contours for F169M indicating
the possible presence of He ii bright clouds or clumps around the CSPN. In
F172M the contours more circular and suggests the presence of CSPN alone.
Bottom: The figure shows the volume contours of the central source in F169M
(He ii emission line) and F172M (continuum) filters. The CSPN is seen to be
accompanied by three He ii clumps in F169M where as the profile in F172M shows
CSPN alone.  Figure 20:  Details of UVIT image of NGC 7293 in the N263M
filter. There are some new structures that are not seen in optical images.
Figure 21:  Details of UVIT image of NGC 7293 in the N263M filter. The fine
optical knots detected in HST image (left) (O’Dell 2005) are seen UV image in
F263M (right) obtained with UVIT. The same knots are shown in both images.
Some of the cometary knots are also present in UV images.

####  2.3.2 NGC 7293, Helix Nebula:

Helix Nebula (PNG036.1-57.1) is one of the nearest (Gaia distance of 201 pc)
and well studied PN in almost all wavelengths (O’Dell et al. 2004,2005, 2007;
Meaburn et al. 2005,2008; Hora et al. 2006; Mentez et al. 2015; Van de Steene
et al. 2015). It is also the largest PN in the sky with a diameter of about
13.’5. A Wide verity of phenomena has been studied in this PN ranging from
exotic molecules, to X-rays, number of intriguing structures, from small
cometary knots to large-scale arcs, to bipolar outflows, dusty disks, shock
fronts etc. The inner helical structure is composed of thousands of cometary
knots of lowly ionized and molecular gas (O’Dell et al. 2007, Etxaluze et al.
2014).

The white dwarf central star WD 2226-210 with a surface temperature of
103600$\pm$ 5500 K (Napiwotzki 1999) ionizes the AGB nebula. Su et al. (2007)
also showed the presence of a 35-150 AU diameter debris disk around this
central star.

The main nebula consists of two rings of highly ionized gas and a faint outer
filament. The three-dimensional (3D) structure of the main nebula has been
investigated by Zeigler et al. (2013) who noted that the structure of the
Helix projects as if it were a thick walled barrel composed of red and blue-
shifted halves in a bipolar geometry. The barrel axis of the Helix is tilted
about 10∘ east and 6∘ south relative to the line of sight .

There are two intriguing aspects that were revealed by infrared studies.
Strong emission lines of [O iv] 25.9$\mu$m and [Ne v] 24.3 $\mu$m have been
detected in the Spitzer spectrum. This source of emission is identified with a
point soure centred on the CSPN. The excitation of [O iv] requires photons of
54.9 e.v . In such a case, He ii lines which also needs 54.4 e.v for
ionization (and recombination)are expected to produce a strong point source
centered on the star. Images of He ii $\lambda$4686 have not shown such a
point source. Secondly it has been known that Chandra X-ray imaging showed a
hard X-ray point source, even at subarc second resolution, centered on the
CSPN. The source of X-rays is unknown. The surface temperature of CSPN is not
hot enough to generate hard X-rays from its photosphere. FUV region contains
He ii 1640Å line, which is expected to be about 16 times stronger
(recombination) than He ii $\lambda$4686, occurs in the F169M filter of UVIT.
With a view to map the hot gas at higher spatial resolution (1.”3) we observed
the central regions of Helix nebula.

We observed the central region of Helix in the first instance in two FUV
filters F169M and F172M and two NUV filters N245M and N263M. F172M images
expected to provide the continuum emission in contrast to F169M. NUV filters
might include mostly the nebular continuum inaddition to some low excitation
emissions. IUE spectra up to 2 arc minutes away from CSPN show that He ii
1640Å line provides strongest emission in the inner regions. Figure 17 show
the relative comparision of the spatial resolution of UVIT with respect to
Galex both in FUV and NUV. Several nebular knots (cometary) seen in HST
optical images (O’Dell 2007) are also present in UV (Figure 20, 21).

F169 images of the central region of Helix showed mainly two surprising
features in contrast to F172M (and N245M and N263M). The region around CSPN
has nebulous clumps surrounding the point source (Figure 17). The intensity
contours around the central source show few arc seconds extended regions
suggesting that the central source is surrouned by clouds of He ii (Figure
19). Secondly, there is a nebulous streamer connecting the central region to
the outer ring (Figure 18). The He ii streamers could possibly be providing
mass flow to and from the central source. Could this be the source of
accretion to the central WD?

Although NGC 7293 is of great astrophysical interest, it is not an easy object
to observe because of its low surface brightness and its large angular extent
in the sky. The field of view of UVIT is adequate to cover major portions of
the nebula at any given pointing. We have observed two more locations in NGC
7293 covering the whole nebula including the shocked regions. Some of the data
is not yet available. We hope to present a detailed paper later.

##  3 Concluding remarks:

In this paper, we have presented UVIT observations of 11 of the 19 proposed
objects in our program. This compendium forms an ”atlas” of sorts, of deep UV
imaging of thise objects, with a spatial resolution of 1”.5. The data for the
8 objects is not yet available. The main theme that has been developed here is
existence of the FUV haloes. Halos around PN are well known and well studied
(Ramos-Larios & Phillips 2009). E.g., in NGC 3587, the halo is seen in all
wavelengths from UV (sec.2.2.3) to the optical, and consists mainly of ionized
gases (Guerrero & Manchado 1999). Extended ionized halo has been found around
60% of the PNs for which proper imaging has been done (Corradi et al. 2003).
The halos are thought to be a result of mass-loss at the end of the AGB phase,
their edges being the signature of the last thermal pulse (Shteffer &
Schonberner 2003). In contrast, the UVIT discovered FUV halos, and jets around
bipolar nebulae and A 30 are only seen in wavelengths shortward of
$\lambda$1650 not in longer wavelength images. Warner and Lyman bands of H2
start appearing shortward of $\lambda$1650\. Ultraviolet fluoresence spectra
of H2 as modeled by France et al. (2005) with IC 63, show strong emission peak
at $\lambda$1608 ($\lambda$eff of F169M filter) and no emission shortward of
$\lambda$1650.

UVIT studies have brought out a totally new aspect to the hidden mass of the
planetary nebulae namely existence of FUV halos, jets and arcs, mostly due to
very cold H2 gas around young, bipolar and even some old PNs like born-again
PNs as well. Such cold gas could only be seen through UV fluorescence of H2
molecule. Big FUV lobes, and jets much bigger than optical nebule have been
detected through FUV studies by UVIT.

UV imaging in each case of PNs we studied, revealed a new aspect
observationally which reiterates the importance of UV studies.

‘Planetary nebulae are like a box of chocolates, you never know what you are
going to get’ – Monic Yourcg

##  4 Acknowledgements:

We would like to express our sincere thanks to several people who have helped
us in carrying out this study of PNs, especially K. Sriram, Arturo Manchado
for supplying ground based images of some the PN in nebular lines, Don Goldman
for the colour image of EGB 6, and Annapurni Subramaniam for the contour
images of NGC 7293.

This publication uses the data from the AstroSat mission of the Indian Space
Research Organisation (ISRO), archived at the Indian Space Science Data Centre
(ISSDC).

UVIT and ASTROSAT observatory development took about two decades before
launch. Several people from several agencies were involved in this effort. We
would like to thank them all collectively. NKR would like thank Department of
Science and Technology for their support through grant SERB/F/2143/2016-17
‘Aspects in Stellar and Galactic Evolution’.

Some of the data presented in this paper (eg. Galex, IUE, HST) were obtained
from the Mikulski Archive for Space Telescopes (MAST). STScI is operated by
the Association of Universities for Research in Astronomy, Inc., under NASA
contract NAS5-26555. Support for MAST for non-HST data is provided by the NASA
Office of Space Science via grant NNX09AF08G and by other grants and
contracts.

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Target characteristics, and observation log of the PNs selected for our
program. The morphological classification is as follows: Compact Bipolar
nebulae (B), large Elliptical (E) and round (R). Subscipts ”s”, ”m” and ”a”
refer to inner structure, multiple shells and ansae respectively. Objects that
have been proposed but not observed to date are noted in the last column as
”n.d.”.  Nebula $\alpha$,$\delta$(2000) type (a) size proposal Date FUV NUV
Comments h m s $\circ$ ’ ” arcmin ID filter filter NGC 40 00 13 01.0 +72 31
19.1 B 0.61$\times$ 0.61 G06-065 2016.12.09 F3,F5 B4,N2,Gr A&A NGC 650 01 42
19.7 +51 34 31.5 Br 3.2 $\times$ 1.97 A07-059To1 2019.10.04 F2,F3,F5 n.d. NGC
1514 04 09 17.0 +30 46 33.5 R 1.67 $\times$ 1.67 G06-066 2016.12.26 F2,F3,F5
B4,B13,N2 A 21 07 29 02.7 +13 14 48.4 Es 10.25 $\times$ 10.25 G05-178T01
2016.09.30 F3,F5 B4,B13 A07-134T02 2019.11.04 F2,F3,F5 NGC 2440 07 41 54.9 -18
12 29.7 B,M 0.55 $\times$ 0.55 G07-034 2017.04.04 F3,F5 B4,B13 OH231.8+4.2 07
42 16.9 -14 42 50.2 B 0.5 $\times$ 0.83 A05-103 2019.03.03 F3,F5 n.d,ppn
Calabash JrEr1 07 57 51.6 +53 25 16.9 Es 6.3 $\times$ 6.3 G06-061 2018.01.22
F2,F3,F5 PNG164.8+31.1 A 30 08 46 53.5 +17 52 46.8 Rs 0.29 $\times$ 0.13
G06-068 2016.12.26 F2,F3,F5 B15,N2,Gr Hyd.def NGC 2818 09 16 01.5 -36 37 37.4
B 0.67 $\times$ 0.67 A05-149 2018.12.21 F2,F3,F5,Gr A$\&$A(p) A09-047
2020.06.09 F1,F2,F3,F5 (d.n.r) EGB6 09 52 59.0 +13 44 34.9 R 0.16 $\times$
0.16 G08-029 2018.04.04 F1,F2,F3,F5 B4,B13,N2,B15 NGC 3587 11 14 52.8 +55 02
00.0 Rsm 3.5 $\times$ 3.5 A05-149T03 2018.12.22 F2,F3,F5 Lo Tr5 12 55 33.8 +25
53 30.6 E 0.18 $\times$ 0.18 G05-182 2016.06.04 F3,F5 B13,B4 0’.5x0’.5,n.d
MyCn18 13 39 35.1 -67 22 51.7 0.21 $\times$ 0.21 G09-061T02 2020.06.06
F2,F3,F5 n.d,Hour glass Mz 3 16 17 15.0 -51 59 42.2 B A05-103 2019.07.26
F2,F3,F5 n.d 2019.06.07 NGC 6302 17 13 44.4 -37 06 11.0 B 1.0 $\times$ 4.85
G06-071 2017.03.18 F2,F3,F5 B15,Gr,N2 A$\&$A A05-103T06 2019.07.24 F2,F3,F5
n.d A 70 20 31 33.2 -07 05 18.0 E 0.8 $\times$ 0.65 A07-134T03 2020.05.14
F2,F3,F5 n.d NGC 7027 21 07 01.8 +42 14 10.0 B 0.5 $\times$ 0.4 A05-149T01
2018.10.05 F2,F3,F5 Hu 1-2 21 33 08.3 +39 38 09.5 Ea 0.67 $\times$ 0.3
A07-059T05 2019.10.24 F2,F3,F5 n.d NGC 7293 22 29 38.5 -20 50 13.6 E 13.4
$\times$ 13.4 G05-187 2016.09.30 F3,F5 B4,B13 Helix G07-31 2017.07.24 F3,F5
position 2,n.d A07-134T01 2019.10.25 F3,F5 Position 3,n.d
a: The types are taken from IAC Morphological Catalog of Northern Galactic
Planetary Nebulae (Manchado et al. 1996).
$*1$: n.d- data is not available, level2 data not received from ISSDC
$*2$:Galex FUV size is bigger -7’