# Low-ionization structures in planetary nebulae - II. Densities,
temperatures, abundances and excitation of 6 PNe

M. Belén Mari${}^{1\href https://orcid.org/0000-0002-2363-6568{}}$ , Denise R.
Gonçalves1 and Stavros Akras${}^{2\href
https://orcid.org/0000-0003-1351-7204{}}$
1Observatório do Valongo, Universidade Federal do Rio de Janeiro, Ladeira
Pedro Antonio 43, Rio de Janeiro 20080-090, Brazil
2Institute for Astronomy, Astrophysics, Space Applications and Remote Sensing,
National Observatory of Athens, Penteli GR 15236, Greece E-mail:
<EMAIL_ADDRESS>
(Accepted XXX. Received YYY; in original form ZZZ)

###### Abstract

Here we present the spatially resolved study of six Galactic planetary nebulae
(PNe), namely IC 4593, Hen 2-186, Hen 2-429, NGC 3918, NGC 6543 and NGC 6905,
from intermediate-resolution spectra of the 2.5 m Isaac Newton Telescope and
the 1.54 m Danish telescope. The physical conditions (electron densities, Ne,
and temperatures, Te), chemical compositions and dominant excitation
mechanisms for the different regions of these objects are derived, in an
attempt to go deeper on the knowledge of the low-ionization structures (LISs)
hosted by these PNe. We reinforce the previous conclusions that LISs are
characterized by lower (or at most equal) Ne than their associated rims and
shells. As for the Te, we point out a possible different trend between the N
and O diagnostics. Te[N ii] does not show significant variations throughout
the nebular components, whereas Te[O iii] appears to be slightly higher for
LISs. The much larger uncertainties associated with the Te[O iii] of LISs do
not allow robust conclusions. Moreover, the chemical abundances show no
variation from one to another PN components, not even contrasting LISs with
rims and shells, as also found in a number of other works. By discussing the
ionization photon flux due to shocks and stellar radiation, we explore the
possible mechanisms responsible for the excitation of LISs. We argue that the
presence of shocks in LISs is not negligible, although there is a strong
dependence on the orientation of the host PNe and LISs.

###### keywords:

ISM: kinematics and dynamics – ISM: abundances – ISM: jets and outflows –
planetary nebulae: individual: IC 4593, Hen 2-186, Hen 2-429, NGC 3918, NGC
6543, NGC 6905.

††pubyear: 2022††pagerange: Low-ionization structures in planetary nebulae -
II. Densities, temperatures, abundances and excitation of 6 PNe–A

##  1 Introduction

Planetary nebulae (PNe) represent the final stages on the evolution of low-
and intermediate-mass stars. They are formed after the ejection of their outer
envelopes, from the multiple stellar wind episodes occurred in the previous
evolutionary stages and resulting in a complex bulk of ionized matter. Besides
the large-scale components of PNe, such as shells, rims or halos, identified
mainly from the emission of bright forbidden [O iii] together with H
recombination lines, much smaller components are also recognized in PNe, due
to their enhanced emission from low-ionization species, such as [N ii], [O
ii], [S ii] or [O i] (see e.g. Corradi et al., 1996; Balick et al., 1998;
Gonçalves et al., 2001; Akras & Gonçalves, 2016, hereafter Paper I). These
macro- and micro-structures are clearly recognizable in PNe’ imaging catalogs
such as Balick (1987), Schwarz et al. (1992), Manchado et al. (1996), Corradi
et al. (1996) or Górny et al. (1999).

Gonçalves et al. (2001) compiled and classified these structures – in terms of
their morphology and kinematics – as knots, filaments, jets and jet-like
systems, which show up in axisymmetric pairs or isolated. To account for such
variety of features, specific nomenclatures also appear in the literature
(Balick et al., 1993; Lopez et al., 1995; Perinotto, 2000). Moreover, in the
above quoted compilation the morphological and kinematic properties of low-
ionization structures (LISs) of the 50 PNe sample were also compared with the
predictions from theoretical models. The main conclusions then guided other
studies with the aim of better constrain LISs’ formation models. However, the
enhanced low-ionization emission lines of LISs, relative to their surrounding
medium, is still a perplexing issue, although observational evidence for their
association with a not-insignificant molecular counterpart is becoming more
and more appealing (Reay et al., 1988). For recent ideas on the relation
between the intensity of low-ionization emission lines and the H2 content of
PNe, focusing the small-scale structures, see e.g. Gonçalves et al. (2009);
Manchado et al. (2015); Ramos-Larios et al. (2017); Akras et al. (2017,
2020b).

Several observational works, sometimes with tailored models to explain the
observations, have been conducted to characterise LISs’ physical and chemical
properties (e.g. Balick et al., 1993, 1994, 1998; Hajian et al., 1997;
Gonçalves et al., 2003; Gonçalves et al., 2004, 2006; Gonçalves et al., 2009;
Akras & Gonçalves, 2016; Danehkar et al., 2016; Ali & Dopita, 2017; Monreal-
Ibero & Walsh, 2020; Miranda et al., 2021). The overall conclusions derived
thus far are: (i) LISs occur in PNe of all different morphological types; (ii)
LISs’ electron temperatures are similar to those of the main nebular
components; (iii) the electron densities of the main structures are higher
than or equal to those measured for LISs; and (vi) there is no chemical
abundance enrichment in LISs, i.e., all the nebular components have similar
chemical composition.

Even though, the LISs’ kinematics were studied in detail for a number of PNe
(for instance in Steffen et al., 2001; García-Díaz et al., 2012; Corradi et
al., 1999; Corradi et al., 2000a; Corradi et al., 2000b; Akras & López, 2012;
Derlopa et al., 2019), a general knowledge about the kinematics of the LISs
was missing until recently, when, at least for the case of pairs of
jets/knots, this issue was solved. From a sample of 85 jets hosted by 58 PNe,
Guerrero et al. (2020b) found that jets can be divided into two populations:
(i) those with spatial velocities below 100 km s-1, which represent $\sim$70%
of the sample, and (ii) those with mean velocities near 180 km s-1. Comparing
the observed spatial and velocity distribution of jets, authors concluded that
jets are mainly coeval with their parent PNe.

Regarding the knots, it is necessary to consider whether they occur in pairs
or isolated, since it is counter-intuitive to necessarily link the formation
of both kinds to the same physical processes. For the latter, Matsuura et al.
(2009) convincingly showed that the isolated knots are part of the nebula’s
inner ring being swamp by the faster stellar wind. Similar conclusions were
reached by Manchado et al. (2015) by studying the molecular waist of NGC 2346.
These two results are not in conflict with the argument that isolated knots
(or part of them) originate in situ from the neutral AGB wind and are
subsequently excited by shocks (e.g. García-Segura et al., 2006) or by the
central star radiation field (Dyson et al., 1989; Soker, 1998).

For the case of the pairs of knots, whilst a consensus has not yet been
reached, the most promising recent models of magneto- or purely-hydrodynamic
jet launching are converging to binaries with magnetic fields as the minimum
requirement for the formation of collimated outflows. This is particularly
true to account for highly collimated pairs of jets and knots. A number of
works explore these arguments, and we refer the readers to Gonçalves et al.
(2001); Balick & Frank (2002); Guerrero et al. (2020b) works, on which the
theoretical efforts are reviewed, almost 2 decades apart. Moreover, the state
of the art of such models (simulations) can be found in the following latest
contributions: García-Segura et al. (2018, 2020, 2021) as well as Balick et
al. (2019, 2020). Also to be mentioned is the series of studies starting with
Akashi & Soker (2008), that simulate light-jets – whose density are much lower
than the density of the slow wind – which end up producing collimated PN
shells and dense pairs of knots.

Explicitly meant to form jets/pairs of knots, Balick et al. (2020) had
convincingly shown, via magneto-hydrodynamic simulations, that very dense
axial knots formed in the slow, heavy flows that account for collimated pre-
PNe and mature PNe eventually become the observed low-ionization knots, once
their surfaces start to become ionized. This simulation predicts that these
LISs’ high densities (105-7 cm-3; their Fig. 6) and related UV opacities
assure that LISs’ interiors remain neutral and cold (3$\times$100-2 K; their
Fig. 6); and with kinematics compatible with Guerrero et al. (2020b)
compilation. Such high densities in LISs have also been suggested for
providing the necessary condition to self-shield the molecular hydrogen (H2)
recently discovered in some LISs from the stellar far-UV radiation (Marquez-
Lugo et al., 2013; Manchado et al., 2015; Fang et al., 2015, 2018; Akras et
al., 2017, 2020b).

In this paper, we present the analysis of spectroscopic data of a sample of 6
PNe with LISs, in order to obtain the spatial physico-chemical properties
together with the excitation mechanisms present in these intriguing structures
and their surrounding nebulae. The observations and the procedure to analyse
the data are described in section 2 and 3, respectively. In section 4 we
present the results of spectroscopic analysis of the different structural
components for the six PNe. Finally, in sections 5 and 6, we present the
discussions and conclusions.

##  2 Observations

Low-resolution spectra of six PNe with embedded LISs were ob- tained using the
2.5 m Isaac Newton Telescope (INT) at the Obser- vatorio Roque de los
Muchachos, Spain, and the 1.54 m Danish telescope at the European Southern
Observatory (ESO) at La Silla, Chile. INT and Danish data were taken,
respectively, in August and September of 2001, and April 1997.

The Intermediate Dispersion Spectrograph (IDS) mounted on the INT was used in
conjunction with the 235 mm camera providing a spatial scale of 0.70 arcsec
pixel-1 with the TEK5 CCD and the R300V grating, thus providing a spectral
resolution of 3.3 Å pixel-1 and a wavelength covering of 3650-7000 Å. The slit
width and length were 1.5 arcsec and 4 arcmin, respectively.

The Danish Faint Object Spectrograph mounted in the Danish telescope was used
in conjunction with the DFOSC 2000$\times$2000 CDD camera, resulting in a
spatial scale of 0.40 arcsec pixel-1, and the Grism$\\#$4 (300 lines mm-1),
which results in a wavelength range of 3600-8000 Å and spectral resolution of
2.2 Å pixel-1. The slit width was 1.0 arcsec and the slit length was $>$13.7
arcmin.

Table 1: Log of observations obtained with INT telescope in 2001 (1) and the
Danish telescope in 1997 (2).

PN name | Date | PA | Exposure [s] |  Seeing† | Airmass
---|---|---|---|---|---
IC 4593(1) | 08-29 | 62° | 120, 300, 1200 |  $1.1$-$1.2$ | 1.21
08-29 | 139° | 120, 300, 1200 |  $1.0$-$1.2$ | 1.66
Hen 2-186(2) | 04-11 | 29° | 60, 300, 1800 | $2.1$ | 1.11
Hen 2-429(1) | 08-29 | 89° | 1800 | $1.8$ | 1.44
NGC 3918(2) | 04-11 | 30° | 60,300 | $1.6$ | 1.14
04-11 | 40° | 300 | $1.7$ | 1.17
04-10 | 42° | 1800 | $1.7$ | 1.18
04-10 | 70° | 20, 300 | $1.7$ | 1.39
NGC 6543(1) | 08-28 | 5° | 20, 300 |  $1.3$-$1.4$ | 1.27
09-04 | 163° | 300, 1200 |  $1.2$-$1.3$ | 1.43
NGC 6905(1) | 08-31 | 161° | 300, 2700 | $1.4$ | 1.17

Note: †Obtained through the FWHM of the stellar continuum measured in the
spectra.

Several spectra have been obtained per PN, in different position angles (PA)
and/or different exposure times (in order to avoid possible saturation of the
usually brightest emission lines; e.g. [O iii], H$\alpha$). The log of the
observations is listed in Table 1. The reduction/analysis of the data was made
using the longslit package in IRAF following the standard procedure: bias
subtraction, flat-field correction and wavelength calibration using lamp
frames. For the flux calibration of the spectra, spectro-photometric standard
stars were observed and the flux calibration was also made with IRAF.

Observations were carried out taking into account the parallactic angle in
order to avoid the differential chromatic refraction (DCR) effect, which
mainly affects the blue side of the spectrum (see e.g., Montoro-Molina et al.,
2022). However, in some cases the PA used did not coincide with the
parallactic angle and the DCR effect on these spectra was estimated. Taking
into account the airmass (or sec(z)), altitudes of $\sim$2 km, and latitudes
of $\sim\pm$30∘ per telescope, the DCR were derived from the equations of
Filippenko (1982). Considering the bluest ([O ii]$\lambda 3727$) and reddest
([S ii]$\lambda 6731$) lines of interest, we observe that the DCR effect could
be present only in two cases. In IC 4593 (PA=139∘) and in NGC 3918 (PA=70∘),
which amount at most to $\sim$1.9 arcsec and $\sim$1.4 arcsec, respectively.
Nevertheless, comparing the results obtained for different PA and structures
of these nebulae (see Tables LABEL:tab:ic4593_1 and LABEL:tab:n3918_1), we
observe that DCR does not substantially affect the measurements on which we
based our conclusions in this work.

##  3 Nebular diagnostics

First, the emission line fluxes were computed considering a Gaussian
distribution in IRAF. Then, the Nebular Empirical Analysis Tool (NEAT, Wesson
et al., 2012) was employed for the analysis. NEAT was used to identify the
lines, compute the extinction coefficient (cβ), electron densities (Ne) and
temperatures (Te) as well as ionic (Xi+/H+) and total abundances (X/H). NEAT
uses the flux-weighted ratios of H$\alpha$, H$\gamma$ and H$\delta$ to
H$\beta$ to calculate and correct the line fluxes for the interstellar
extinction adopting the Galactic reddening law of Howarth (1983), with
$R_{V}=A_{V}/E(B-V)=3.1$.

The emission line intensities, in units of H$\beta$=100, together with cβ, Ne
and Te are listed in odd tables (LABEL:tab:ic4593_1-LABEL:tab:n6905_1) for
several nebular components extracted from specific windows that are
illustrated in Figures 1 to 7. Electron temperatures and densities were
computed for different diagnostic lines. For the particular case of Ne
estimation using the [Ar iv] diagnostic lines, the theoretical value of He i
4713/4471=0.146 (Benjamin et al., 1999) was used (considering Te=104 K and
Ne=104 cm-3) to correct the blended [Ar iv] $\lambda$4711+He i $\lambda$4713
emission from the contribution of the He recombination line.

For the ionic and total abundance calculations, as discussed by Wesson et al.
(2012), the temperatures and densities that are more appropriate for the
ionization potentials of the ionized gas are used. To correct for the
unobserved ions, the ionization correction factors (ICF) of Delgado-Inglada et
al. (2014) were adopted, except for Ar/H and S/H, in which the ICFs from
Kingsburgh & Barlow (1994) were used. The ionic and total abundances, per PN
nebular components, are listed in even tables
(LABEL:tab:ic4593_2-LABEL:tab:n6905_2). For the Ne2+/H+ derived from the [Ne
iii] $\lambda$3967 line, we applied the correction for the contribution of the
H$\epsilon$ $\lambda$3970 line, considering the theoretical ratio
H$\epsilon$/H$\beta\sim 0.158$ (Osterbrock & Ferland, 2006).

It should be noted that NEAT uses a Monte Carlo scheme to calculate the
statistical uncertainties of the parameters, based on the flux uncertainties
and their propagation through the diagnostics 111For further information about
this tool and its error propagation, readers are directed to Wesson et al.
(2012).. Errors related with Ne and Te were obtained directly from the
uncertainties of the lines involved on the diagnostic ratio, as in the
previous papers of the series (Gonçalves et al., 2003; Gonçalves et al., 2004;
Gonçalves et al., 2009; Akras & Gonçalves, 2016; Mari et al., 2020).

##  4 Results

In the next subsections we present the spectroscopic analysis of six PNe, for
the different morphological structures – LISs, shells, rims and a portion of
the nebula along the various slit positions, generally of high-ionization,
labeled as Neb. We also summarize the main results from the literature.

Figures 1 to 4, 6 and 7 show the above defined components, per nebula. The
normalized flux distribution of the [N ii]$\lambda$ 6584 (solid-line) and [O
iii]$\lambda$ 5007 (dashed-line) along the slits, as well as the ratio of
these emission lines, are presented in the middle and lower panels of the
figures. The line-ratio plots are extremely useful to define the the regions
of the spectra to extract the regions under analysis. Ideally, the underlying
nebular emission should be subtracted from the LISs emission lines, to insure
that LISs’ properties are not contaminated by those of the large-scale nebular
structures. However, with the current data, this is a cumbersome task. This
kind of correction can be better addressed with IFU data, by computing the
large-scale nebula structures emission from the surrounding region. A good
example of such correction is by Montoro-Molina et al. (2022) who managed to
resolve the inner region from the surrounding nebular emission in the velocity
space. Therefore, we compute the emission lines from different nebular
structures such as Neb, LISs and rims/shells, and compare the outcomes among
these structures.

For the six PNe, the emission line fluxes, absolute flux of H$\beta$
(observed), cβ, Ne and Te are presented in the odd tables (from Table
LABEL:tab:ic4593_1 to LABEL:tab:n6905_1). On the other hand, the ionic and
total abundances of the nebular components are show on the even tables (from
Table LABEL:tab:ic4593_2 to LABEL:tab:n6905_2). The literature with which we
compared the results of our diagnostics are listed in the captions of Figures
8 and 9.

###  4.1 IC 4593

In the optical, IC 4593 is a complex multiple-shell PN, with a roundish bright
filamentary outer shell, with $\sim$16” in extension. The (H$\alpha$+[N
ii])/[O iii] ratio images from Corradi et al. (1996) revealed the presence of
a pair of knots, which authors called jet-like features, located near
$\sim$12” from the center and oriented along PA=139∘, as well as an isolated
knot embedded in the inner layers along PA=62∘ (Fig. 1). According to Corradi
et al. (1997) the jet-like features have radial velocities of 2 km s-1,
whereas for the isolated knot this value is of 1 km s-1.

For the analysis of this nebula we selected the slit which contains the pair
of LISs (PA=139∘) and the isolated one (PA=62∘), together with the inner shell
(4 regions) and Neb. We, previously, studied this nebula and the results were
presented in Mari et al. (2020), however, the emission-line fluxes were
remeasured in an attempt to reduce uncertainties. The improved results are
presented here.

Figure 1: Upper panel: HST [N ii] image of IC 4593. All regions and nebular
components selected for the spectroscopic analysis, LISs, shells and Neb are
highlighted with green, cyan and red coloured boxes, respectively. The
extracted window of the LISs is 3.5 arcsec for the PA=139∘ slits (regions A
and B) and 2.1 for the PA=62∘ slit (region C), for the shells is 3.5 arcsec
for the slit at PA=62∘ and 6.3 arcsec for the slit at PA=139∘ and 15 arcsec
for both Neb regions regardless the slit position. The size of the image is
30$\times$25 arcsec2. Lower panels: the flux distribution of the [Nii] and
[Oiii] emission lines, normalized to 1.0 – in logarithmic scale – and the [N
ii]/[O iii] line ratio, along the slits at PA=139∘ (panels a and b) and PA=62∘
(panels c and d). The coloured regions correspond to the equivalent
region/component in the upper panel.

The interstellar extinction coefficient of IC 4593 varies significantly
between the components and slit positions, from 0.02 to 0.22, with an average
value of $0.11\pm 0.02$. Interestingly, a similar wide range of cβ is found in
the literature, from 0.01 (Costa et al., 1996, along E-W direction), 0.05
(Tylenda et al., 1992), 0.125 (Barker, 1978a), 0.17 (Robertson-Tessi &
Garnett, 2005, along E-W direction) up to 0.24$\pm$0.16 (Delgado Inglada et
al., 2009, PA=0). This wide range of cβ values likely indicates a significant
variation across the nebula, which could, for instance, be associated with
mass loss variations or the dust ejected in the AGB phase (e.g. Walsh et al.,
2016). Integral field spectroscopy should be very helpful to investigate the
variation of cβ in both spatial directions of this nebula.

From the IC 4593’s spectra it was possible to estimate the Ne and Te using the
diagnostic line ratios of sulphur, nitrogen and oxygen (see Table
LABEL:tab:ic4593_1). Considering both slit positions, Te[O iii] varies from
(8100$\pm$1800) K to (8800$\pm$1100) K. Taking into account the uncertainties
of Te, our results are in agreement with the previously published values (for
the literature references, see caption of Fig. 8). The only exception is the
pair of LISs along 139∘, which has higher values exceeding 11000 K. However,
due to the large relative errors, we cannot argue for any variation in Te[O
iii] between the different components. In the case of Te[N ii], the values
computed in this work vary between 9510 K and 11400 K, again in agreement with
the literature. Here as well, the LISs at PA 139∘ are characterized by higher
values ($\sim$13000 K) and higher uncertainties. On the other hand, Ne is
solely determined from the [S ii] doublet lines and takes values from
2100$\pm$1200 cm-3 to 2800$\pm$600 cm-3 that agrees with some published
values, but is higher than others, as shown in Fig. 8. According to the
analysis above, we can see that both Te and Ne do not show any significant
spatial variation among either the shells and LISs, or even from one to
another PA (Neb).

The ionic and total abundances for IC 4593 are listed in Table
LABEL:tab:ic4593_2. No variation in He abundance between components is
observed. The average value is 0.100$\pm$0.004, in good agreement with the
majority of the literature (see Fig. 8), but lower than 0.11 reported by
(Kwitter & Henry, 1998) or 0.127 by Stanghellini et al. (2006). As for O/H,
there is also no trend among nebular components, except for both LISs located
along 139∘ that show lower values, variation related to the face values higher
Te [O iii] of these LISs222We note that, at variance with Te and Ne
uncertainties, obtained directly from the propagation of the emission-line
ones, the ionic and total abundance uncertainties were estimated via Monte
Carlo approach, within NEAT. This is why X/H uncertainties seems to be small,
even when the Te uncertainties are severe.. Comparing with the published
abundances, we note that our results of O/H are sometimes higher but,
considering the errors, in agreement with Bohigas & Olguín (1996) and
Stanghellini et al. (2006). For N/H our results are similar to those reported
by Bohigas & Olguín (1996) and Kwitter & Henry (1998), and higher than those
achieved in other works. Our results could indicate a possible variation in
N/H abundances through the structures. However, Gruenwald & Viegas (1998)
while analyzing the empirical abundances determinations, argued that
abundances estimations through line intensities depend on the line of sight.
Hence, the empirical abundances at different regions in a nebula may not be
representative. In fact, we obtain a variation in the N/O abundance ratio,
with the highest values found for the LISs along 139∘. This result is, though,
closely correlated with the problem of the much higher face values of the [O
iii] temperature, as discussed above. Ne/H abundances derived in this work are
higher than in the literature. On the other hand, when performing the Ne/O
ratio, the values fall close to those published by Barker (1978b); Bohigas &
Olguín (1996); Stanghellini et al. (2006), within errors. Our Ar/H abundance
is lower than the literature, while Cl/H abundance has not yet been reported.
Following the criteria giving by Peimbert (1978) and Kingsburgh & Barlow
(1994) to define Type I PNe – as He/H$\geq$0.125 and N/O$\geq$0.5 – this
nebula is classified as non-Type I PN.

###  4.2 Hen 2-186

Hen 2-186 is a relatively small PN with an angular extension of $\sim$3.5”.
The (H$\alpha$+[N ii])/[O iii] ratio images from Corradi et al. (1996) have
revealed a pair of LISs about $\sim$4.5” from the center, and oriented along
29∘ in position angle. The clump located near to the center of the nebula is
actually a field star. Three components were selected for the analysis of this
nebula: the pair of LISs and the inner nebula (Neb), all of them along the PA
of 29∘ (see Fig. 2). This particular nebula belongs to a specific group of
PNe, whose jets (LISs) have radial velocities greater than 100 km s-1, with a
value of 135 km s-1 (Corradi et al., 2000a; Guerrero et al., 2020b). Corradi
et al. (2000a) suggested these LISs might be prominent point-symmetrical
features within a more general structure containing faint bipolar lobes.

Figure 2: Upper panel: HST [N ii] image of Hen 2-186. The size of the field is
20$\times$14 arcsec2. The nebular components under analysis are indicated by
the boxes: the nebular region (Neb, 5.2 arcsec, in red) and the LISs (A and B,
2 arcsec, in green). Lower panels: Same as Fig 1.

Table LABEL:tab:h186_1 shows the diagnostics derived for the different
structures of the nebula. cβ of Hen 2-186 has an average value of
0.70$\pm$0.04, which agrees with the most recent estimation from Cavichia et
al. (2010, cβ=0.75), but is higher than that presented by Kaler (1970,
c${}_{\beta}=0.4$) and lower than the value of 0.93 from Tylenda et al.
(1992). The Neb component has a Te[O iii] of 14600$\pm$330 K, slightly higher
than Te[N ii]=11300$\pm$240 K. These figures coincide, within the
uncertainties, with those presented so far in the literature (see Fig. 8). We
were also able to derive Te[O i], though with larger uncertainty, as being
12700$\pm$3200 K. As for the Ne, we estimated Ne[Cl iii] of 8100$\pm$1600
cm-3, Ne[Ar iv] of 5420$\pm$210 cm-3 and Ne[S ii] of 3990$\pm$130 cm-3, for
Neb. The latter is in good agreement with that reported by Cavichia et al.
(2010). Taking into account the LISs and Neb Te, we argue that Hen 2-186 does
not reveal any important temperature spatial variation. With regard to the Ne,
LISs are found to be less dense than Neb, by a factor between $\sim$2.3 and
$\sim$3.7. The higher densities found using the argon and chlorine line ratios
may imply a density stratification in the inner nebula. Further spatially-
resolved analysis is needed to confirm this trend.

Hen 2-186’s ionic and total abundances are presented on Table
LABEL:tab:h186_2. He abundances are found unchanged among the nebular
components, with an average of 0.133$\pm$0.009, in good agreement with the
literature (see Fig. 8). For the N abundance no variation is detected through
the components, and the Neb result coincides with that published by Cavichia
et al. (2010), but is lower than that reported by Ventura et al. (2017).
Nonetheless, for O/H we can see that the LISs exhibit higher values than the
nebula by a factor between $\sim$2.1 and $\sim$2.5 333An over- or under-
abundance of around two is not high enough to allow a firm conclusion of
abundance variation across the nebula, due to the cavities of the ICF scheme
(Kingsburgh & Barlow, 1994; Delgado-Inglada et al., 2014)., and if errors are
taken into account Neb value matches the published ones (see the caption of
Fig. 8). A similar behavior is observed for Ne/H, for which LISs show higher
abundances by a factor between $\sim$1.9 and $\sim$2.3. With regard to Ar/H,
it can be seen that it does not vary significantly among regions, and our
estimations are lower than those reported in literature. On the other hand,
the average of S/H abundance is similar to previous works. According to its
chemical abundances, Hen 2-186 can be classify as non-type I PNe.

###  4.3 Hen 2-429

The PN Hen 2-429 possesses a point-symmetric morphology with an elliptical
shell and a pair of faint jet-like features, the latter only prominent in low-
ionization emission (Guerrero et al., 1999). These LISs are located at
$\sim$6.5” from the center, oriented along the PA of 89∘, and have systemic
radial velocities of 5 km s-1, according to Guerrero et al. (2020b). Our study
of this nebula selects three components: the pair of LISs and the main body of
the nebula (Neb), all of them along the position angle of 89∘, as it can be
seen in Fig. 3.

Figure 3: Upper panel: [N ii] image of Hen 2-429 from Manchado et al. (1996).
The size of the field is 33$\times$23 arcsec2. The nebular components under
analysis are indicated by the boxes: the nebular region (Neb, 10.5 arcsec, in
red) and the LISs (A and B, 3.5 arcsec, in green). Lower panels: Same as
previous Figures. Note: the bottom panel, which shows the line ratio, shows
peaks that are not related to the features of the nebula, but to the
displacement between spatial distribution of the emission lines. The [Nii] and
[Oiii] spectra are misaligned for a fraction of pixel, which generates the
false peaks near the continuum, within the Neb region.

Our results in terms of the spectroscopic characterization (line intensities,
H$\beta$ flux, cβ, Ne and Te) of He 2-429’s components are given in Table
LABEL:tab:h429_1. As the table shows, its extinction coefficient is the
highest in our sample, with an average value of 2.08$\pm$0.09, which agrees
with (or is close enough to) the values reported in Giammanco et al. (2011,
2.12), Tylenda et al. (1992, 2.3) and Girard et al. (2007, 2.21). The electron
temperatures of Hen 2-429 are provided only for Neb, Te[O iii] of
9800$\pm$2400 K and Te[N ii] of 9400$\pm$700 K, as neither the [N ii]
$\lambda$5755 nor the [O iii] $\lambda$4363 auroral lines were detected in the
LISs. Our estimations are consistent, within the errors, with the previous
ones reported in the literature (see Fig.8). As for Ne, we derived Ne[S ii] of
5710$\pm$270 cm-3 and Ne[Cl iii] of 5200$\pm$2400 cm-3 for the Neb component,
values that are slightly smaller than previously reported. Compared to Neb,
the Ne of the LISs are lower by a factor of $\sim$1.8 and $\sim$1.3 for A and
B, respectively.

Ionic and total abundances are shown in Table LABEL:tab:h429_2. Taking into
account the errors, Neb abundances are in good agreement with Girard et al.
(2007), with the exception of He/H for which our value (0.151$\pm$0.019) is
higher than the published one (see Fig. 8). As it can be seen in Table
LABEL:tab:h429_1, no electron temperature was computed for the LISs. However,
the abundances of LISs were estimated adopting the mean- and low-ionization
temperatures of the Neb. Within the uncertainties, we find no significant
variation of abundances between LISs and Neb. Values on Table LABEL:tab:h429_2
allow us to classify Hen 2-429 as non-type I PN.

###  4.4 NGC 3918

NGC 3918 is a widely studied planetary nebula and characterized by a complex
morphology – various models have been used to reproduce its morphological
properties. Clegg et al. (1987) proposed a biconical geometry, whereas
Ercolano et al. (2003) adopted, besides the biconical one, two spindle-like
models. Both representations have integrated emission-line spectra which are
in agreement with the observations. Peña et al. (2017) came to the conclusion
that NGC 3918 has a complex point-symmetric morphology. Aside from the large-
scale structures, it has LISs located outside the main PN body and oriented
approximately along the major axis. (H$\alpha$+[N ii])/[O iii] ratio images
from Corradi et al. (1996) initially revealed the presence of one jet and one
knot on radially opposite sides. In this work, we present the spectroscopic
analysis of several NGC 3918’s structures, by adopting the nomenclature
defined by Corradi et al. (1999), including also two other micro-structures
named B’ and B”. All nebular components under our analysis are shown in the
HST [N ii] image of the nebula in Fig. 4.

The properties that the present data allow us to derive, for the different
nebular components, are shown in Table LABEL:tab:n3918_1. Note that the
recombination lines of C ii at $\lambda$4267 Å , C iii at $\lambda$4647 Å and
C iv at $\lambda$5801/12 Å are detected in our spectra and also reported by
Clegg et al. (1987) and Górny (2014). In the latter, these recombination lines
were considered as mimics of emission-line stars. As Górny (2014), we also
suggest that the origin of these lines is not stellar, and base our argument
on their spatial distribution in the 2D spectra (see Fig. 5).

Figure 4: HST [N ii] image of NGC 3918. The size of the field is 44$\times$31
arcsec2. The nebular components under analysis are indicated by the boxes: the
nebular regions (Neb, same extension in all directions: 16.8 arcsec, in red);
the rims (in cyan; for PA=30∘ 1.6 arcsec and for PA=70∘ 1.2 arcsec); the LISs
(in green; for A 2 arcsec, for A’ 1.2 arcsec, for B 2.4 arcsec, for B’ 1.2
arcsec and for B” 1.6 arcsec).

Figure 5: Two different regions of the 2D spectra of NGC 3918 to highlight the
mimics of emission-line stars. Left panel: the arrows correspond to the lines
of C ii at $\lambda$4267 Å (left) and C iii at $\lambda$4647 Å (right). Right
panel: the arrow indicates the position of the C iv at $\lambda$5801/12 Å
line.

The interstellar extinction of NGC 3918 has an average value of 0.28$\pm$0.01,
without a significant variation among the different structures. Our value is
lower than those obtained by Pena & Torres-Peimbert (1985), Tsamis et al.
(2003), and Robertson-Tessi & Garnett (2005), which amount to 0.40, 0.44 and
0.40, respectively. Nevertheless, our result is consistent, within the
uncertainties, with the values found in Clegg et al. (1987, 0.33$\pm$0.14)
(using the Balmer decrement), Kwitter et al. (2003, 0.27) and García-Rojas et
al. (2015, 0.26$\pm$0.06). Ne and Te were estimated using the diagnostic line
ratios of sulphur, chlorine, argon, nitrogen and oxygen. No significant
variation is found for Te[N ii] among the different structures. For Neb we
obtained Te[N ii] of 11100$\pm$500 K, along 30∘, and 11200$\pm$800 K for the
PA of 70∘, both agree well with the literature. The average value of Te[O iii]
for Neb is 12700$\pm$140 K, which is also in good agreement with the published
values. This latter temperature also has no significant variation across the
nebular components, though LIS B”, along the PA of 40∘, has higher Te[O iii]
face values, with far higher errors than the other structures. As for the Ne,
we computed 5230$\pm$190 cm-3, 5700$\pm$800 cm-3 and 4220$\pm$80 cm-3 as the
average values for Neb, from the [S ii], [Cl iii] and [Ar iv] diagnostic
lines, respectively. Ne[S ii] is consistent with the literature, but lower
than the value determined by Richer et al. (1991, 5700 cm-3) and higher than
that of Kwitter et al. (2003, 3800$\pm$380 cm-3). The mean value of Ne[Cl iii]
is also in good agreement with the literature, whereas for the case of Ne[Ar
iv] our value is lower than those published by Stanghellini & Kaler (1989) and
García-Rojas et al. (2015), of 6166 cm-3 and 6500${}^{+1300}_{-1200}$ cm-3,
respectively. Regarding the variation among different nebular components, it
should be noted that for the case of LISs, the Ne could only be calculated
using the sulfur diagnostic lines that, in comparison with Neb, is lower by a
factor that varies from $\sim$2.6 to $\sim$3.9.

Ionic and total abundances are listed in Table LABEL:tab:n3918_2, from which
no variation in He abundances is observed. The average He/H is
0.104$\pm$0.003, in good agreement with the literature (see Fig. 9). For O/H
there is no much contrast among nebular components, except for the LIS B”,
along 40∘, for which we find a value of approximately half that of the other
structures. Similarly to the case of IC 4593, this under-abundance of B” is
related with the much higher, and much uncertain, Te[O iii]. Excluding this
LIS, the average O/H is (4.0$\pm$0.1)$\times 10^{-4}$, which is lower than
those obtained previously by some authors, but considering the errors agrees
with Henry et al. (2018). The N/O abundance ratio also agrees with the
published values in the literature. Considering the quantities in Table
LABEL:tab:n3918_2, we conclude that this nebula classifies as non-type I. The
neon abundance behaves as O/H, without any variation among nebular components
(with the exception of B”, whose value is lower than the average of the other
structures, by a factor $\sim$5.7). Given that B” is the faintest nebular
component of NGC 3918, and also the fact the its behaviour differs
significantly from that of the other LISs of the nebula, we do not argue that
the variation in either Te or X/H is real. At variance with Ar abundance, the
average Cl/H and S/H are consistent with those published by Kwitter et al.
(2003).

###  4.5 NGC 6543

NGC 6543 is among the most widely studied PNe and several works have focused
on understanding its complex morphology (e.g. Balick et al., 1987; Miranda &
Solf, 1992; Balick et al., 1994; Reed et al., 1999; Ramos-Larios et al., 2016;
Guerrero et al., 2020a) concluding that it is formed by a geometrically thick
expanding ellipsoid with two bright shells. NGC 6543 also posses a pair of
LISs with radial velocities of 39 km s-1 (Miranda & Solf, 1992; Reed et al.,
1999; Guerrero et al., 2020b). Moreover, recent near-IR narrow-band imagery of
the nebula has revealed the presence of H2 emission in the [N ii] emission
between the rims/shells and LISs (Akras et al., 2020b).

The analysis we present here follows the same nomenclature proposed by Miranda
& Solf (1992). Our study is based on two slit positions (5∘ and 163∘), and the
nebular components under analysis are denoted as A, D and J (in the northern
half), with their counterparts A’, D’, J’, and Neb. The J and J’ LISs are
covered by the slit at PA of 5∘ (see Fig. 6).

Table LABEL:tab:n6543_1 shows the line intensities, observed H$\beta$ flux,
cβ, Ne and Te derived for the above structures, along both slits. From Table
LABEL:tab:n6543_1 it is straightforward noticing that cβ varies among the
components, from $\sim$0.02 up to 0.26. The average extinction coefficient is
0.11$\pm$0.02, which is in good agreement with Perinotto et al. (1999, 0.12)
and Williams et al. (2008, 0.14). Interestingly, cβ values in the range from
0.08 up to 0.3 have also been reported by other authors as Robertson-Tessi &
Garnett (2005, 0.08), Wesson & Liu (2004, 0.1), Kaler (1970, 0.22) and Hyung
et al. (2000, 0.3). As in the case of IC 4593, this non-negligible variation
in cβ points to spatial variations within the nebula. Such a spatial variation
is also obtained, for instance, from the 2D cβ map of NGC 7009 computed for
MUSE IFU data (Walsh et al., 2018).

Figure 6: Upper panel: HST [N ii] image of NGC 6543. The size of the field is
63$\times$48 arcsec2. The nebular components under analysis are indicated by
the boxes: the nebular regions (Neb, same extension in both directions: 23.1
arcsec, in red); the shells (A, A’, D, D’, 3.5 arcsec in cyan); the LISs (J
and J’, 6.3 arcsec, in green). Lower panels: Same as previous Figures, along
the slit which contains the LISs, PA=5∘.

For the estimation of electron temperature and density, the diagnostic line
ratios of sulphur, chlorine, argon, nitrogen and oxygen were used. Considering
all nebular components, except the LISs, along both slit positions, the
computed average value of Te[O iii] is 8150$\pm$210 K in very good agreement
with the literature (see Fig. 9). As for the J and J’ (LISs), Te[O iii] is
12100$\pm$7500 K and 10000$\pm$7000 K, respectively. These results may be
indicative of extra heating mechanisms, such as shocks. However, the much
higher uncertainties obtained for the LISs’ do not allow firm conclusions
about the possibility of real variations of Te[O iii] among the nebular
components. Regarding the Te[N ii] of components A, A’, D and D’, we obtain an
average value of 10000$\pm$500 K, in good agreement with previous estimations.
As for the J and J’ contrast with the other components, the errors again
prevent robust conclusions. Balick et al. (1994) also studied three different
regions of this nebula, named rim, cap and ansae (the latter are equivalent to
our LISs), with a long-slit along the position angle of 14∘. Balick et al.
(1994) electron temperatures for the three structures are Te[O iii] (Te[N ii])
of 8000 K (9300 K), 7900 K (9000 K) and 8200 K (7400 K), respectively.
Therefore, for the rim and cap components their values are coincident with
ours, while for the ansae our results are higher, with higher uncertainties,
though strictly speaking, ours and Balick et al. (1994) derived quantities are
in good agreement.

Sulfur, chlorine and argon lines allowed the derivation of the electron
densities. A subtle variation is found among the nebular components, but J/J’,
the LISs, are showing much lower electron densities. In particular, the
average value for Ne[S ii] is 5060$\pm$100 cm-3 for the slit at along 5∘ and
5220$\pm$130 cm-3 for the 163∘ one. As for the J and J’ LISs, we determined
Ne[S ii] of 950$\pm$240 cm-3 and 930$\pm$210 cm-3, respectively. These values
are lower when compared to the other components, by factors of $\sim$5.3 for J
and $\sim$5.5 for J’. The comparison with the literature shows that our
densities are close to the previous calculations (see Fig. 9). Moreover,
Balick et al. (1994) computed the electron density for the rim, cap and ansae
obtaining 4600 cm-3, 5000 cm-3 and 2200 cm-3, respectively. Ne[Cl iii] and
Ne[Ar iv] were also computed for the main nebular structures (Neb) and their
average are 4630$\pm$310 cm-3 and 6800$\pm$900 cm-3, respectively. The
resultant values again are in agreement with the previous estimations of Ne[Cl
iii] of Wesson & Liu (2004, 4660 cm-3) and Williams et al. (2008,
5000${}^{+2100}_{-1400}$ cm-3), but slightly larger than Ne[Ar iv] of
Robertson-Tessi & Garnett (2005, 5020$\pm$800 cm-3) and Williams et al. (2008,
4500${}^{+1100}_{-900}$ cm-3).

Table LABEL:tab:n6543_2 shows the derived values of the ionic and total
abundances. He abundances are spread within the range from 0.098$\pm$0.002 to
0.124$\pm$0.024 for the different nebular components. Hyung et al. (2000)
studied two regions of this nebula (named east and north) and they found a
similar helium abundance behaviour of 0.1 and 0.13, respectively, for these
two regions. Though no errors are quoted for the latter results, authors argue
that this dissimilitude gives room for a possible spatial variation in the
nebula. For the O abundance, there is no trend among nebular components, and
our results are in agreement with published values (see Fig. 9), except for
both LISs located along the position angle of 5∘. The latter have slightly
lower oxygen abundances, which are actually on the limit to, within the
errors, agree with that of the other components. As far as N/H is concerned,
there could be a very small variation across the nebula, with the highest
values found in the A and D rims, together with the J’ LISs (all along the
same PA, 5∘), possible variation that was also reported by Balick et al.
(1994). The Ne abundance also follows the possible small variation through the
components (peaking at the position of the rims AA’ and DD’) and in average it
is in good agreement with the literature. Considering the average of N/O and
He/H, we conclude that this nebula is of non-Type I class. The total Ar
abundances present some subtle variations, being the lowest in the DD’ (rim)
and invaluable for the LISs. For Neb, Ar/H is sub-estimated by one order of
magnitude, when compared with some authors, but close to the values reported
by Perinotto et al. (2004), as it can be seen in Fig. 9.

###  4.6 NGC 6905

This nebula has a bright, broadly spheroidal shell, with a roughly conical
shape extending over $\sim$82 arcsec, with a pair of LISs located $\sim$35”
from the central star. The H$\alpha$+[N ii] images from Corradi et al. (2003)
reveal this pair of LISs, and also another one near the NW LIS, which we refer
to as NW knot 2. The opposite knot of the pair (SE knot) is close enough to a
field star to be contaminated, so it was excluded from our spectroscopic
analysis. The nebular components that we selected for analysis are shown in
Fig. 7, while the results of their analysis appear in Table LABEL:tab:n6905_1.

Figure 7: Upper panel: H$\alpha+$[N ii] image of NGC 6905 from Corradi et al.
(2003). The size of the field is 130$\times$104 arcsec2. The nebular
components under analysis are indicated by the boxes: the nebular region (Neb,
42 arcsec, in red); the rims (4.2 arcsec for south and 5.6 arcsec for north
one, in cyan); the LISs (5.6 arcsec for NW knot and 4.2 arcsec for NW knot2,
in green). Lower panels: Same as previous Figures.

The interstellar extinction coefficient of NGC 6905 does not shown significant
variation from one to another nebular component, with an average of
0.05$\pm$0.02. Our cβ agrees with one of the previous works, 0.11$\pm$0.18
(Cahn, 1976). Other authors reported extinctions of 0.27 (Kingsburgh & Barlow,
1994, for a PA of 90∘) or 0.23, 0.22, 0.29 (Pena et al., 1998, three different
slit positions), 0.55 (Kaler, 1970) and 0.93 (Kaler, 1986). In fact, recently
Gómez-González et al. (2022) studied almost the same low- and high-ionization
structures as in the present work (and named A1, A2 and A3 our NWknot, NWknot2
and north rim, as well as A6 for our south rim), by using longslit spectra
with a PA of 155∘. These authors also obtain a similar cβ variation, from 0.05
to 0.23.

We did not find significant difference in Te[O iii] among the structures,
being the mean 13960$\pm$1088 K. This temperature is higher than some previous
measurements (see Fig. 9), but close to that of Kaler (1970, 14300 K). Gómez-
González et al. (2022) obtained Te[O iii] of $12840\pm 1010$ K for A1,
$12430\pm 800$ K for A2, $12030\pm 380$ K for A3 and $12930\pm 440$ K for A6,
all comparable with ours (nevertheless the central value we found for NWknot
is a factor $\sim$1.3 higher). Pena et al. (1998) also studied this nebula
using three different positions angles: (i) 90∘, passing through the central
star; (ii) 0∘, with 5” offset to the north of the central star; and (iii) 90∘
for the SE LIS. Their Te[O iii] of (12100$\pm$800) K, (13100$\pm$800) K and
(14000$\pm$3000) K for each of these slits, respectively, are not in
disagreement with our mean Te[O iii]. Notice that a spatial variation in Te[O
iii] may be indicated from the Te[O iii] of Pena et al. (1998), but the
uncertainties do not allow for a robust conclusion. An analysis of cβ and Te
with IFU will be useful to further investigate the possibility of their
spatial variation in NGC 6905. As for the electron density, the Neb value we
derived from the [S ii] doublet is (740$\pm$150) cm-3, whereas densities of
the rims are much lower having values of 350$\pm$80 and 280$\pm$40, and LISs
are less dense by a factor of $\sim$2.5 and $\sim$3.4. Yet, the Neb density
agrees, within the errors, with Stanghellini & Kaler (1989, 850 cm-3), but it
is lower than that of Pena et al. (1998, 1500 cm-3). Regarding the LIS,
despite the fact that both sulfur diagnostic lines were detected, the line
ratio lies outside the theoretical curve (e.g. Osterbrock & Ferland, 2006;
Stanghellini & Kaler, 1989), indicating a very low electron density. Thus, we
argue for Ne[S ii]$<$220 cm-3 for NW knot. Accounting for the errors, Gómez-
González et al. (2022) LISs ($500\pm 290$ cm-3) and north rim ($480\pm 220$
cm-3) densities are also in agreement with our results.

NGC 6905 abundances are listed in Table LABEL:tab:n6905_2. As expected, there
is no variation in He abundance from one to another component, being
He/H=$0.118\pm 0.038$, the average value, in agreement with previous
literature reports (see Fig. 9). It should be noted that a strong variation in
the He ii $\lambda$4686/H$\beta$ has been reported by Vorontsov-Vel’Yaminov
(1961), with an intensity ratio varying from 0.5 to 1.3 over $\sim$15 years
(between 1945 and 1959). In our analysis we find, for Neb, a He ii
$\lambda$4686/H$\beta$ ratio of $\sim$1.05. Gómez-González et al. (2022)
succeed in separating the central star from the nebular emission. Ours and
theirs He ii 4686 Å for both structures match well, apparently indicating both
emissions are blended. With the exception of the NW knot, for which we find an
under-abundance of a factor $\sim$2.8 respect to the Neb, the O/H does not
change among the components. Per structure, N/H are higher than those reported
by Gómez-González et al. (2022), which may be due to need of applying the Te[O
iii] instead of Te[N ii] to derive the nitrogen abundance. On one hand, N/O is
similar throughout the nebular components, but, on the other hand, higher in
the NW knot by a factor $\sim$1.4. Considering He/H and N/O in Table
LABEL:tab:n6905_2, we can conclude that NGC 6905 classifies as Type I. The
total Ne/H abundances are also similar among the nebular components and in
agreement with the values reported in literature. On the other hand, Ar/H
presents a variation with the higher value found for one of the rims (also
higher than in the literature, as in Fig. 9) but not measurable for NW knot.
S/H is found to be nearly constant among the nebular components except the NW
LIS, for which it is lower by a factor of $\sim$3.2 respect to the Neb,
difference that was also reported by Gómez-González et al. (2022). As in the
case of a couple of LISs previously mentioned, some X/H are lower in the LIS
than in the rest of the components, as a consequence of the Te[Oiii] that is
also much higher (and highly uncertain).

Figure 8: Variation of total abundances, electronic density and temperature
across nebular components for IC 4593, Hen 2-186 and Hen 2-429. The horizontal
lines represent values published in the literature, only for comparison with
our results. When a studied nebula has more than one PA, different symbols
represent different PAs. References for IC 4593: (1) Perinotto (1991), (2)
Bohigas & Olguín (1996), (3) Kwitter & Henry (1998), (4) Stanghellini et al.
(2006), (5) Barker (1978a), (6) Delgado Inglada et al. (2009), (7)
Stanghellini & Kaler (1989), (8) Phillips (1998), (9) Kaler (1986), (10) Kaler
(1978), (11) Robertson-Tessi & Garnett (2005). References for Hen 2-186: (1)
Cavichia et al. (2010), (2) Ventura et al. (2017). References for Hen 2-429:
(1) Girard et al. (2007), (2) Górny & Tylenda (2000), (3) Medina et al.
(2006).

Figure 9: Same as Fig. 8 for NGC 3918, NGC 6543 and NGC 6905. References for
NGC 3918: (1) Perinotto (1991), (2) Kwitter et al. (2003), (3) Henry et al.
(2004), (4) Henry et al. (2018), (5) Clegg et al. (1987), (6) Stanghellini &
Kaler (1989), (7) Phillips (1998), (8) García-Rojas et al. (2015), (9) Richer
et al. (1991). References for NGC 6543: (1) Kaler (1970), (2) Perinotto et al.
(1999), (3) Hyung et al. (2000), (4) Perinotto et al. (2004), (5) Wesson & Liu
(2004), (6) Williams et al. (2008), (7) Phillips (1998), (8) Robertson-Tessi &
Garnett (2005). References for NGC 6905: (1) Perinotto (1991), (2) Kingsburgh
& Barlow (1994), (3) Stanghellini et al. (1995), (4) Stanghellini & Kaler
(1989), (5) Pena et al. (1998), (6) Cahn (1976), (7) Kaler (1986), (8) Kaler
(1970).

##  5 Discussion

In the following we discuss different aspects of the physical, chemical and
excitation properties of the six PNe whose results were given above, focusing
on their variation across slits and/or components, and also allowing for the
comparison with the literature.

###  5.1 Extinction variation

For two of the PNe in the sample we found variations in the extinction
coefficient. The first case is IC 4593, for which this coefficient is ranging
from $0.02\pm 0.02$ to $0.22\pm 0.01$. We also want to note that the
intensities of H$\gamma$ and H$\delta$ lines display a small variation from
one another structure, suggesting a real internal spatial variation in this
coefficient. The second case is NGC 6543, which has a cβ that takes values
from $0.02\pm 0.02$ to $0.26\pm 0.01$. For this nebula, there is a PA in which
the H$\alpha$ line was saturated, therefore cβ was estimated using only
H$\gamma$ and H$\delta$. Even so, the other PA studied, whose cβ were
calculated also using H$\alpha$, presents as well extinction coefficient
variations. As with the previous nebula, we note that the intensity of
H$\gamma$ and H$\delta$ lines show small variation. In addition, in recent
works of Akras et al. (2020a) and Akras et al. (2022), in which longslit were
simulated on IFU data, the authors verify that variations in the extinction
coefficient are present even as a result of only changing the PA. Therefore,
these spatial variations in the extinction coefficient, in both nebulae, are
likely real, and they can only be much better studied through IFU data.

###  5.2 Densities and temperatures

Figure 10 displays Ne[S ii] as a function of Te from the [N ii] (upper panel)
and the [O iii] (lower panel) lines. The main conclusions drawn from these
plots are: (i) Te[N ii] is almost invariant through the components considering
their uncertainties, whereas LISs’ Te[O iii] is higher compared to the
rims/shells, although the large uncertainties do not allow for a robust
conclusion; and (ii) Ne[S ii] is generally lower for LISs relative to the rest
of the components.

Figure 10: Te versus Ne for all the components in our PNe’s sample. Upper
panel: Te using [N ii] diagnostic lines versus log(Ne[S ii]). Lower panel: Te
using [O iii] diagnostic lines versus log(Ne[S ii]). Arrows are indicating
these quantities for NGC 6905, which it was not possible to determine Te[N
ii].

The comparison between the two Te indicators – from [N ii] and [O iii] lines –
is presented in Fig. 11. In particular, we find that the mean value for Te[N
ii] is 11000$\pm$1600 and Te[O iii] is 12600$\pm$1200 K for the group of LISs,
whereas for the group of rims/shells these values are 10200$\pm$800 and
9510$\pm$220 K, respectively. This difference in Te between the two indicators
is also present for the sample of PNe discussed by Osterbrock & Ferland (2006)
(see their Fig.5.3) and attributed to excitation differences among the
nebulae.

Figure 11: Te[N ii] versus Te[O iii] for all the components in our PNe’s
sample. The dashed gray line represents the identity.

###  5.3 Abundance trends

Fig. 12 shows that the range of log(N/H) and log(O/H) we derived are $-$4.4 to
$-$3.0 and $-$4.2 to $-$3.0, respectively. A negligible variation in log(N/H),
for Te[N ii], was observed, regardless the nebular components. On the
contrary, the derived O abundances show a non-negligible variation with Te[O
iii]. In particular, most of log(O/H) lie within the range of $-$3.6 to
$-$3.1. regardless of Te[O iii]. But there are four cases with
log(O/H)$<-$3.7: two LISs in IC 4593, one LIS in NGC 3918 and one in NGC 6905.
The latter cases are also characterized by Te[O iii]$>$15000 K, which is thus
responsible for the resulting lower O abundances relative to the rest of the
components in these PNe. Notice that all these cases are also described by
very large uncertainties in Te[O iii] due to the detection of weak [O iii]
4363Å emission line.

Figure 12: Variation of oxygen and nitrogen abundances as a function of
electronic temperature. Upper panel: Te[N ii] versus log(N/H), in which there
is no tendency considering the errors. Lower panel: Te[O iii] versus log(O/H).
Arrows are indicating the position of the LISs having lower O/H than the rest
of the points (see text).

Figure 13 presents the correlation among various abundance ratios. The dashed
lines in the He/H versus log(N/O) plot, define the limits of Type I PNe
(He/H$\geq$0.125 and log(N/O)$\geq-0.3$, Peimbert, 1978). All but one PNe (NGC
6905) are classified as non-Type I. The log(N/H)+12 versus log(N/O) plot gives
the best linear relation as $log(N/O)=0.85(log(N/H)+12)-7.37$, with a
goodness-of-fit ($R^{2}$) equal to $0.83$, if eliminating the LISs marked with
arrows (the same highlighted in Fig. 12). Our analysis returns a slightly
different slope and intercept when compared to a sample of PNe with [WR]-type
central stars (0.73 and $-$6.50, García-Rojas et al., 2013) or a sample of PNe
with LISs (0.74 and $-$6.50, Paper I).

The correlations between log(X/H)+12 and log(X/O) for X = Ar, Ne, S and Cl are
also presented in Fig. 13. No significant contrast between LISs and the
rims/shells are found for these chemical abundances, in agreement with the
conclusions from Paper I, and other previously published analyses.

Figure 13: Upper panels: N/O abundance ratio plotted against He abundance
(left) for our PN sample. The dashed lines are delimiting the criteria giving
by Peimbert (1978) to define Type I PNe. In the right panel, log(N/O) versus
log(N/H)+12, where the dashed line is representing the best linear fit to our
data (see text). Middle panels: relationship between Ar/O (Ne/O) abundance
ratio and the total Ar (Ne) abundance on the left (right). Lower panels:
relationship between S/O (Cl/O) abundance ratio and the total S (Cl) abundance
on the left (right).

###  5.4 Central star properties

Table 2: General characteristics of central star planetary nebulae (CSPNe)
from Weidmann et al. (2020).

| Type | Teff [K] | L [L⊙] | log(g)
---|---|---|---|---
IC 4593 | O(H)5f |  $\sim$48000 |  $\sim$5500 | 3.70
Hen 2-186 | Cont. † |  $\sim$107500 |  $\sim$7900 | 5.40
Hen 2-429 | [WC 4] (1) |  $\sim$23000 †† |  $\sim$5900 | -
NGC 3918 | O(H) |  $\sim$150000 |  $\sim$5000 | 5.56
NGC 6543 | Of-WR(H) (2) |  $\sim$60400 |  $\sim$3800 | 4.70
NGC 6905 | [WO 2] (3) |  $\sim$130900 |  $\sim$10200 | 4.70

Notes: † Type cont. means that its spectrum has a high S/N ratio with no
stellar features. †† Such a low temperature contradicts our spectroscopic data
in which we detect the He ii $\lambda$4686 line.
(1) We detected emission lines from this type of CSPN (see Table
LABEL:tab:h429_1) having FWHM in good agreement with the literature De Araújo
et al. (2002, 37$\pm$1).
(2) We identify emission lines with a stellar origin (see Table
LABEL:tab:n6543_1).
(3) According to Aller (1968) and Cuesta et al. (1993), this nebula owns one
of the most broadened O vi emission lines observed among PNe, which are also
detected in our spectra (see Table LABEL:tab:n6905_1) and reported by Gómez-
González et al. (2022)

Concerning the central stars of the PNe studied here (Table 2), we find that
these PNe containing LISs have either [WR]- or O(H)-type (see also, Miszalski
et al., 2009) covering a large range of Teff, $\sim$45000 K to $\sim$150000 K,
L ranging from $\sim$3800 L⊙ up to $\sim$10000 L⊙, and log(g) taking values
from 3.7 to 5.5.

###  5.5 Photo- versus shock-excitation of LISs

The long-standing problem of the excitation mechanism of LISs can also be
addressed for our sample of PNe. In Paper I, the $f_{\rm shocks}/f_{\rm star}$
ratio was defined to explore the contribution of shocks on LISs and their host
PNe. This ratio describes the ionizing photon flux emitted from the central
star ($f_{\rm star}$) and the ionizing photon flux produced by a potential
shock interaction ($f_{\rm shocks}$). Paper I authors concluded that
log$(f_{\rm shocks}/f_{\rm star})>-1$ defines the zone of shock-dominated
structures, while log$(f_{\rm shocks}/f_{\rm star})<-2$ encompasses the
photoionization-dominated structures, and the transition between the two,
$-2<log(f_{\rm shocks}/f_{\rm star})<-1$, is where both mechanisms are
present. Given the (generally uncertain) parameters entering this ratio, a
deeper understanding of it is in place, before further dedicated analyses.

The ionizing photon flux, $f_{\rm shocks}$, is determined from the total
radiative flux, $F_{\rm shocks}=2.28\times 10^{-3}(V_{\rm
shock}/100kms^{-1})^{3}(N_{e}/cm^{-3})$ ergs cm-2 s-1, where $V_{shock}$ is
the shock velocity and $N_{e}$ is the density of the pre-shocked gas (Dopita &
Sutherland, 1996), divided by the average energy of a photon emitted from the
central star $(L/S_{*})$. Thus, the equation becomes $f_{\rm shocks}/f_{\rm
star}=9.12\times 10^{-3}(V_{shock}/100kms^{-1})^{3}(N_{e}/cm^{-3})(\pi
d^{2}/L)$, where $d$ is the LISs’ distance from the central star (in cm) and
$L$ is the luminosity of the central star (in erg s-1) (Lago et al., 2019).
The issue here is that the usually uncertain distances to PNe ($\propto$ d2),
the unknown density of pre-shocked gas ($\propto$ Npre-shock) and the exact
velocity of the shock wave ($\propto$ V${}_{\rm shock}^{3}$) prevent a
unequivocal determination of the $f_{\rm shocks}/f_{\rm star}$ ratio. The
explicit contribution of these parameters is as below.

_(i) Distances_ \- The distances of the PNe in our sample were mainly adopted
from Frew et al. (2016); Guerrero et al. (2020b), otherwise additional
references are quoted.

_(ii) Pre-shock density_ \- Because there is very little known about the pre-
shock density, the $f_{\rm shocks}/f_{\rm star}$ ratio is determined for a
range of Npre-shock from 0.1 to 10000 cm-3. We also point out that the density
of the post-shocked gas (LISs) and pre-shocked gas (surrounding gas) are
dependent parameters. At the shock jump, contact discontinuity, we get Npost-
shock = (($\gamma$+1)$M^{2}$)/(($\gamma$-1)$M^{2}$+2)$\times$Npre-shock (see
e.g. Mellema, 2004), where $\gamma$ is the adiabatic index (5/3 for an ideal
gas) and M is the Mach number of the shock wave, defined as Vshock/Vsound,
where Vsound is the sound speed in the pre-shocked gas and its value is
$\sim$12-15 km s-1 for a gas with T$\sim$10000 K. For the case of a strong
shock (M$\gg$1) and ideal monoatomic gas, N${}_{\rm post-shock}\approx
4\times$Npre-shock. The post-shocked gas becomes less dense for lower Mach
numbers (or Vshock). In particular Vshock $>$45 km s-1 yields Npost-
shock/Npre-shock $>$3, and 25$<$Vshock $<$45 km s-1 yields Npost-shock/Npre-
shock $>$2 (for Vsound=15 km s-1). Therefore, $f_{\rm shocks}/f_{\rm star}$
ratio is computed considering a Npre-shock that is consistent with the
observed Npost-shock of LISs.

_(iii) Inclination_ \- The limited information about the inclination of PNe
and LISs does not allow for a direct determination of the expansion
velocities. Hence, to derive the $f_{\rm shocks}/f_{\rm star}$ ratio a range
of velocities, 20 to 140 km s-1, with steps of 20 km s-1, is considered. The
radial velocities were adopted from Guerrero et al. (2020b) and Cuesta et al.
(1993), and they are illustrated in Fig. 14 as lower limits (vertical dashed
lines).

In an attempt of applying these ideas to the LISs of each PN in our sample,
Fig. 14 displays the log($f_{\rm shocks}/f_{\rm star}$) ratio as function of
the expansion velocity, for different distances from the central star (circle,
triangle and square points) and various pre-shock densities (colour-bars).

Figure 14: Variation of the $log(f_{\rm shocks}/f_{\rm star})$ ratio as a
function of the shock velocity, for three distance from the central stars
(circle, triangle and square symbols), and a range of pre-shock densities from
0.1 up to 10000 cm-1 for each nebula of our sample. The velocities are taken
from Guerrero et al. (2020b) for all PNe except NGC 6905 Cuesta et al. (1993).
The parameters of the central stars are taken from Table 2. The vertical
dashed-line indicate the projected spectroscopic velocities of the LISs and
host PNe. The horizontal arrows denote the lower limit of the observed
velocities. The horizontal dashed-lines indicate the limits of the photo-
ionization and shock dominated regions defined by Akras & Gonçalves (2016).

  * •

IC 4593 (top-left panel): The very small radial velocity of the LISs (1$-$2 km
s-1) suggests a highly inclined nebula, which gives a expansion velocity up to
100 km s-1. These LISs have Ne of $\sim$ 2000-3000 cm-3 corresponding to Npre-
shock of $\sim$ 500$-$750 cm-3. We argue that shock interaction becomes
important for Vexp $>$60 km s-1. Lower pre-shock densities would require
higher shock velocities. The minimum inclination angle with respect to the
light of sight, for an expansion velocity of 60 km s-1 is $\sim$88∘. The
contribution of shocks in the excitation of the LISs of IC 4593 is as likely
as that of pure photo-ionization processes.

  * •

Hen 2-186 (top-right panel): This nebula shows the fastest LISs in our sample,
with Vexp $\gtrsim$ 135 km s-1. Such a high velocity is very likely
responsible for shocked-heated gas. We get $-$1<log($f_{\rm shocks}/f_{\rm
star}$)<$-$2 (in the transition zone), for 2$<$log(Npre-shock)$<$3, and higher
ratios for higher densities. Npre-shock $\sim$250$-$450 cm-3 are implied from
the LISs electron densities, $\sim$ 1000-1700 cm-3. There is strong indication
for a non-negligible contribution of shocks for the LISs of Hen 2-186.

  * •

Hen 2-429 (middle-left panel): LISs embedded in this nebula have Ne in the
range of $\sim$ 3000-4000 cm-3, which corresponds to log(N${}_{\rm pre-
shock})$ between 2.8 and 3.0. The radial velocity of the LISs is 5.9 km s-1.
Only V${}_{\rm exp}\gtrsim 40$ km s-1 (inclination angle of $\sim$81∘-82∘
respect to the light of sight) would be indicative of significant shocks
contribution, even though, shock-excitation in the spectrum of the LISs of Hen
2-429 cannot be ruled out.

  * •

NGC 3918 (middle-right panel): An electron density of $\sim$1500$-$2000 cm-3
has been estimated for its LISs that correspond to N${}_{\rm pre-shock}\sim
400-500$ cm-3, depending on the Mach number. For such pre-shock densities only
Vexp $>$40 km s-1 yield to a non-negligible contribution of shocks, at a
distance from the central star of 6$\times$10-17 cm (square symbols). The
radial velocities of the LISs in NGC 3918 are 27 km s-1 (A) and 10 km s-1 (B).
The excitation of both LISs can be attributed to shocks if Vexp $>$60 km s-1,
or equivalently, their inclination angles respect to the light of sight are at
least of 63∘ and 80∘, respectively.

  * •

NGC 6543 (bottom-left panel): In this nebula the LISs are characterized by
$N_{e}\sim 950-1000$ cm-3, or equivalently N${}_{\rm pre-shock}\sim 250$ cm-3.
Their radial velocity is 39 km s-1 (Miranda & Solf, 1992; Reed et al., 1999;
Guerrero et al., 2020b). A distance of 1.2 kpc (Gómez-Gordillo et al., 2020)
to NGC 6543 is considered. The contribution of shocks becomes noteworthy for
Vexp $>$60 km s-1. The morpho-kinematic analysis of NGC 6543 gives an
inclination angle of $\sim$55 (Miranda & Solf, 1992) implying a de-projected
expansion velocity of $\sim$68 km s-1. The LISs excitation ratio in NGC 6543
is very likely between $-$2 and $-$1, in the transition zone, and therefore
shock contribution cannot be ruled out.

  * •

NGC 6905 (bottom-right panel): It is characterized by very low LIS’ Ne,
between 200 and 300 cm-3, or N${}_{\rm pre-shock}\sim 55-70~{}cm^{-3}\approx
100~{}cm^{-3}$. The radial velocity of the PN and LIS are 30 and 50 km s-1,
respectively. For such low Npre-shock, we obtain ratios greater than $-$2, for
Vexp between 60 and 80 km s-1, or inclination angles of 45∘-65∘ with respect
to the light of sight. Both mechanisms, photo-ionization and shock-heating
likely contribute to the LISs’ excitation in this PN.

Overall, taking into account the radial velocities, the LISs distances to the
central stars, as well as the pre- and post-shock densities, we conclude that
shock contribution cannot be ruled out as a possible excitation mechanism for
most of the LISs in our sample. However, only the LISs in Hen 2-186, with
radial velocity of 135 km s-1, unequivocally lie in the shock-dominated zone.
We also note that pre-shock densities lower than 100 cm-1 result in negligible
shock contribution and log($f_{\rm shocks}/f_{\rm star}$)>$-$2 for Vexp up to
100$-$120 km s-1.

Another commonly used way of investigating the photo- versus shock-excitation
of astrophysical objects is through diagnostic diagrams such as Sabbadin,
Minello & Bianchini (1977) or Riesgo & López (2006), which are based on line
ratios sensitive to these excitation processes. In Paper I, we discussed these
diagnostic tools, and given their relevance, our forthcoming work will analyse
these and other diagnostic diagrams for a statistically significant sample of
PNe that host low-ionization structures combined with predictions from
photoionization and shock models.

##  6 Conclusions

The spectroscopic analysis of six PNe with embedded LISs was carried out.
Physico-chemical properties of the PNe with different structural components
were computed and compared with the results in the literature.

After analyzing the properties of the LISs and their host PNe, we reinforce
the conclusions of previous works that the electron density of LISs are lower
(or at most equal) than those of the PN main structures (rims and shells).
Regarding electron temperatures, we point out a possible different trends
between estimations based on the nitrogen or the oxygen diagnostic lines. Te[N
ii] does not exhibit significant variations throughout the components, whereas
Te[O iii] appears to take slightly higher values for LISs relative to rims and
shells, but also with much higher uncertainties, therefore not allowing robust
conclusions.

In terms of abundances, as on Paper I (and the previous ones in the series),
we do not find any trend between components. We have to mention the lower O/H
for a couple of LISs, which would thus imply a non-negligible variation.
However, these LISs also have extremely uncertain (higher, sometimes exceeding
15000 K) Te[O iii], which result in suspicious face values for their oxygen
abundances.

In an attempt to better understand the excitation mechanisms present in LISs,
the diagnostic diagram defined on Paper I – log($f_{\rm shocks}/f_{\rm star}$)
– was used, together with LISs kinematics. Considering that there are
uncertainties on distances, pre-shock densities and radial velocities, we
argue that the contribution of shocks to the excitation appears to be non-
negligible for the PNe in our sample. In particular, shocks seems to be
unambiguously associated with Hen 2-186’ LISs, while for the remaining PNe the
dependence on the inclination angle is much stronger, and since PNe do not
have preferential orientations, shock excitation is not mandatory.

It seems evident the need to increase the sample of LISs to be able to perform
a statistical analysis that takes into account all the properties found in
recent years for these poorly understood structures. That is why these six PNe
with LISs, jointly with a compilation of those already published in previous
works, will be analysed in a forthcoming work. For this purpose, a statistical
approach will be followed to derive the distribution of physical, chemical and
main excitation mechanism of the low-ionization structures in planetary
nebulae.

## Acknowledgements

We would like to thank Martín Guerrero, the referee, for his constructive
comments and suggestions that helped to improve this work. This paper contains
data taken jointly with A. Mampaso and R. Corradi, back in 2001, during a
wonderful week of observations at the Roque de los Muchachos. We are also as
much as thankful to H. Schwarz (in memoriam), the observer of the Danish data.
This research is support by a PhD grant from CAPES – the Brazilian Federal
Agency for Support and Evaluation of Graduate Education within the Education
Ministry. DGR acknowledges the CNPq grants 428330/2018-5 and 313016/2020-8. SA
thanks the support under the grant 5077 financed by IAASARS/NOA.

## Data Availability

Some of the spectroscopic data underlying this article are available at the
Isaac Newton Group Archive.

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##  Appendix A flux lines together with ionic and total abundances

The flux emission lines measurements and obtained results are present in this
section. The fluxes were corrected for interstellar reddening and then they
were used to estimate Te, Ne, ionic and total abundances for all nebulae
present in this paper together with the smaller structures as rims, shells and
LISs.

Table A1: IC 4593

|  | PA=62 | PA=139
---|---|---|---
Line | Ion | NE shell | Neb | SW Shell | C | A | SE Shell | Neb | NW Shell | B
|  | 5px-3.5” | 22px-15” | 5px-3.5” | 3px-2.1” | 5px-3.5” | 9px-6.3” | 22px-15” | 9px-6.3” | 5px-3.5”
3727.00 |  [O ii]b |  55$\pm$1 |  45$\pm$1 |  54$\pm$2 |  126$\pm$4 |  151$\pm$17 |  42$\pm$2 |  44$\pm$4 |  38$\pm$6 |  74$\pm$8
3868.75 |  [Ne iii] |  28.3$\pm$0.4 |  33.3$\pm$0.8 |  23.2$\pm$0.9 |  22.7$\pm$1.7 |  31.5$\pm$10.3 |  25.9$\pm$0.6 |  30.8$\pm$1.3 |  20.0$\pm$1.1 |  23.4$\pm$7.3
3889.05 |  H i+He i |  20.4$\pm$0.3 |  14.3$\pm$0.8 |  19.2$\pm$0.8 |  21.2$\pm$1.3 |  24.5$\pm$12.3 |  18.0$\pm$0.5 |  17.7$\pm$1.1 |  16.1$\pm$1.7 |  18.8$\pm$6.6
3967.46 |  [Ne iii] |  9.4$\pm$0.4 |  5.1$\pm$0.9 |  5.9$\pm$0.8 |  6.4$\pm$1.4 |  8.8$\pm$7.6 |  5.9$\pm$0.3 |  7.2$\pm$0.9 |  2.2$\pm$1.4 |  3.8$\pm$3.4
3970.07 |  H i |  16.8$\pm$0.4 |  16.2$\pm$0.9 |  16.2$\pm$0.8 |  15.8$\pm$1.5 |  17.0$\pm$7.8 |  17.6$\pm$0.3 |  16.2$\pm$0.9 |  16.5$\pm$1.4 |  17.3$\pm$6.3
4101.74 |  H i |  27.1$\pm$0.4 |  22.8$\pm$0.6 |  25.2$\pm$0.8 |  26.5$\pm$1.3 |  33.1$\pm$10.4 |  25.4$\pm$0.3 |  23.2$\pm$0.7 |  28.5$\pm$1.2 |  27.2$\pm$6.9
4340.47 |  H i |  47.8$\pm$0.3 |  44.6$\pm$0.7 |  44.6$\pm$0.6 |  45.7$\pm$1.1 |  51.7$\pm$8.1 |  45.1$\pm$0.8 |  45.3$\pm$0.5 |  48.4$\pm$1.3 |  50.6$\pm$3.9
4363.21 |  [O iii] |  1.8$\pm$0.1 |  1.8$\pm$0.4 |  1.9$\pm$0.3 |  2.2$\pm$0.6 |  6.0$\pm$4.3 |  1.8$\pm$0.3 |  2.3$\pm$0.3 |  1.7$\pm$0.5 |  4.3$\pm$2.5
4471.50 |  He i |  5.3$\pm$0.2 |  5.0$\pm$0.5 |  5.2$\pm$0.4 |  5.3$\pm$0.9 | - |  5.2$\pm$0.4 |  4.8$\pm$0.3 |  4.0$\pm$0.7 | -
4685.68 |  He ii | - |  2.0$\pm$0.4 | - | - | - | - |  2.8$\pm$0.3 | - | -
4711.37 |  [Ar iv] |  0.6$\pm$0.1 |  0.8$\pm$0.3 |  0.5$\pm$0.2 | - | - |  0.6$\pm$0.3 |  0.8$\pm$0.2 | - | -
4861.33 |  H i | 100 | 100 | 100 | 100 | 100 | 100 | 100 | 100 | 100
4958.91 |  [O iii] |  173$\pm$1 |  192$\pm$1 |  177$\pm$1 |  183$\pm$2 |  149$\pm$10 |  167$\pm$1 |  183$\pm$1 |  168$\pm$2 |  150$\pm$10
5006.84 |  [O iii] |  517$\pm$3 |  569$\pm$3 |  523$\pm$5 |  528$\pm$8 |  415$\pm$33 |  534$\pm$1 |  542$\pm$3 |  505$\pm$3 |  431$\pm$14
5517.66 |  [Cl iii] |  0.4$\pm$0.1 |  0.4$\pm$0.2 |  0.5$\pm$0.1 |  0.7$\pm$0.3 | - |  0.2$\pm$0.1 |  0.5$\pm$0.4 |  0.3$\pm$0.2 | -
5537.60 |  [Cl iii] |  0.4$\pm$0.1 |  0.4$\pm$0.2 |  0.4$\pm$0.2 |  0.9$\pm$0.4 | - |  0.2$\pm$0.1 |  0.5$\pm$0.4 |  0.3$\pm$0.2 | -
5754.60 |  [N ii] |  0.2$\pm$0.1 |  0.2$\pm$0.1 |  0.2$\pm$0.1 |  0.4$\pm$0.3 |  3.0$\pm$1.8 |  0.12$\pm$0.09 |  0.2$\pm$0.1 |  0.2$\pm$0.1 |  1.9$\pm$1.0
5875.66 |  He i |  15.7$\pm$0.1 |  15.8$\pm$0.3 |  12.7$\pm$0.2 |  17.0$\pm$0.6 |  15.4$\pm$2.7 |  15.2$\pm$0.3 |  15.5$\pm$0.3 |  15.8$\pm$0.5 |  14.6$\pm$2.9
6300.30 |  [O i] | - | - |  0.15$\pm$0.08 |  0.4$\pm$0.2 |  4.4$\pm$1.8 | - | - | - |  4.2$\pm$1.8
6312.10 |  [S iii] |  0.8$\pm$0.1 |  0.7$\pm$0.2 |  0.8$\pm$0.1 |  0.9$\pm$0.3 | - |  0.4$\pm$0.1 |  0.8$\pm$0.2 |  0.8$\pm$0.2 | -
6548.10 |  [N ii] |  4.5$\pm$0.1 |  4.5$\pm$0.2 |  5.4$\pm$0.2 |  11.2$\pm$0.7 |  30.5$\pm$1.9 |  2.9$\pm$0.1 |  4.2$\pm$0.1 |  5.4$\pm$0.3 |  16.6$\pm$3.0
6562.77 |  H i |  292$\pm$2 |  275$\pm$2 |  281$\pm$2 |  269$\pm$5 |  273$\pm$22 |  284$\pm$3 |  279$\pm$2 |  292$\pm$4 |  281$\pm$15
6583.50 |  [N ii] |  12.1$\pm$0.1 |  12.3$\pm$0.2 |  13.2$\pm$0.3 |  26.7$\pm$0.9 |  81.8$\pm$7.1 |  7.9$\pm$0.2 |  11.7$\pm$0.2 |  14.4$\pm$0.5 |  53.5$\pm$4.9
6678.16 |  He i |  3.5$\pm$0.1 |  4.3$\pm$0.2 |  4.4$\pm$0.2 |  3.5$\pm$0.3 |  3.5$\pm$1.4 |  2.4$\pm$0.1 |  4.1$\pm$0.1 |  3.6$\pm$0.3 |  4.2$\pm$2.3
6716.44 |  [S ii] |  0.5$\pm$0.1 |  0.5$\pm$0.1 |  0.8$\pm$0.1 |  1.6$\pm$0.2 |  4.9$\pm$1.8 |  0.3$\pm$0.1 |  0.6$\pm$0.1 |  0.7$\pm$0.1 |  5.4$\pm$2.5
6730.82 |  [S ii] |  0.7$\pm$0.1 |  0.7$\pm$0.1 |  1.2$\pm$0.2 |  2.4$\pm$0.2 |  7.2$\pm$1.8 |  0.4$\pm$0.1 |  0.8$\pm$0.1 |  1.0$\pm$0.2 |  7.3$\pm$2.6
$log~{}F(H\beta)$ | $-12.30$ | $-11.22$ | $-11.74$ | $-13.03$ | $-13.85$ | $-11.68$ | $-11.22$ | $-11.79$ | $-13.55$
$c(H\beta)$ |  0.13$\pm$0.01 |  0.05$\pm$0.01 |  0.06$\pm$0.01 |  0.02$\pm$0.02 |  0.14$\pm$0.09 |  0.22$\pm$0.01 |  0.05$\pm$0.01 |  0.12$\pm$0.02 |  0.16$\pm$0.08
Electron densities (cm-3) and temperatures (K)
Ne[S ii] |  2610$\pm$155 |  2840$\pm$626 |  2290$\pm$477 |  2360$\pm$355 |  2750$\pm$1222 |  2220$\pm$758 |  2810$\pm$545 |  2220$\pm$546 |  2100$\pm$1227
Te[N ii] |  9950$\pm$4956 |  10300$\pm$5153 |  9550$\pm$4779 |  9510$\pm$7138 |  13900$\pm$9314 |  9630$\pm$7225 |  11400$\pm$5701 |  9550$\pm$4783 |  13800$\pm$6992
Te[O iii] |  8470$\pm$472 |  8120$\pm$1805 |  8560$\pm$1353 |  8610$\pm$1465 |  13100$\pm$8770 |  8340$\pm$1390 |  8800$\pm$1148 |  8310$\pm$2445 |  11400$\pm$5710

Table A2: Ionic and total abundances of IC 4593.

| PA=62 | PA=139
---|---|---
Abundances | NE shell | Neb | SW Shell | C | A | SE Shell | Neb | NW Shell | B
10${}^{2}\times$ He+/H |  10.3$\pm$0.2 |  10.5$\pm$0.3 |  9.5$\pm$0.3 |  10.7$\pm$0.6 |  8.9$\pm$2.1 |  9.9$\pm$0.3 |  10.5$\pm$0.4 |  9.8$\pm$0.5 |  9.6$\pm$2.3
10${}^{3}\times$ He2+/H | - |  1.6$\pm$0.3 | - | - | - | - |  2.2$\pm$0.3 | - | -
10${}^{2}\times$ He/H |  10.3$\pm$0.2 |  10.7$\pm$0.3 |  9.5$\pm$0.3 |  10.7$\pm$0.6 |  8.9$\pm$2.1 |  9.9$\pm$0.3 |  10.7$\pm$0.4 |  9.8$\pm$0.5 |  9.6$\pm$2.3
10${}^{6}\times$ N+/H |  2.6$\pm$0.9 |  2.6$\pm$1.3 |  3.6$\pm$1.6 |  7.2$\pm$3.0 |  8.5$\pm$4.2 |  2.2$\pm$1.1 |  2.1$\pm$1.0 |  3.7$\pm$1.5 |  7.3$\pm$4.8
icf(N) |  47.7$\pm$25.0 |  25.0$\pm$18.0 |  32.6$\pm$22.2 |  14.1$\pm$9.1 |  9.4$\pm$7.9 |  44.8$\pm$37.5 |  22.4$\pm$15.5 |  56.2$\pm$41.1 |  29.7$\pm$27.5
10${}^{5}\times$ N/H |  12.4$\pm$2.6 |  6.6$\pm$2.3 |  11.7$\pm$4.6 |  10.3$\pm$3.8 |  8.7$\pm$4.2 |  10.0$\pm$5.9 |  4.7$\pm$1.7 |  20.6$\pm$16.8 |  16.1$\pm$9.5
10${}^{7}\times$ O0/H | - | - |  3.0$\pm$2.0 |  7.7$\pm$5.0 |  25.6$\pm$8.8 | - | - | - |  25.9$\pm$17.4
10${}^{5}\times$ O+/H |  2.9$\pm$0.9 |  2.5$\pm$1.7 |  4.0$\pm$2.6 |  8.8$\pm$5.3 |  2.5$\pm$1.7 |  3.3$\pm$2.4 |  1.8$\pm$1.2 |  2.6$\pm$1.6 |  1.2$\pm$0.9
10${}^{4}\times$ O2+/H |  3.3$\pm$0.2 |  4.3$\pm$1.3 |  3.2$\pm$0.5 |  3.2$\pm$1.6 |  0.6$\pm$0.3 |  3.5$\pm$0.5 |  2.9$\pm$0.7 |  3.4$\pm$0.8 |  1.0$\pm$0.4
icf(O) |  1.00$\pm$0.00 |  1.01$\pm$0.01 |  1.00$\pm$0.00 |  1.00$\pm$0.00 |  1.00$\pm$0.00 |  1.00$\pm$0.00 |  1.01$\pm$0.01 |  1.00$\pm$0.00 |  1.00$\pm$0.00
10${}^{4}\times$ O/H |  3.6$\pm$0.3 |  4.8$\pm$0.9 |  3.7$\pm$0.6 |  4.4$\pm$1.3 |  1.1$\pm$0.6 |  4.0$\pm$0.7 |  3.3$\pm$1.1 |  3.9$\pm$1.1 |  1.3$\pm$0.6
10${}^{4}\times$ Ne2+/H |  0.7$\pm$0.1 |  0.8$\pm$0.3 |  0.5$\pm$0.1 |  0.5$\pm$0.3 |  0.12$\pm$0.07 |  0.6$\pm$0.2 |  0.6$\pm$0.1 |  0.5$\pm$0.2 |  0.14$\pm$0.07
icf(Ne) |  1.6$\pm$0.2 |  1.6$\pm$0.3 |  1.8$\pm$0.9 |  2$\pm$1 |  3$\pm$1 |  1.6$\pm$0.3 |  1.07$\pm$0.07 |  1.6$\pm$0.2 |  1.8$\pm$0.4
10${}^{4}\times$ Ne/H |  1.1$\pm$0.2 |  1.4$\pm$0.4 |  0.9$\pm$0.5 |  1.1$\pm$0.4 |  0.4$\pm$0.3 |  1.0$\pm$0.2 |  0.6$\pm$0.2 |  0.8$\pm$0.3 |  0.3$\pm$0.2
10${}^{6}\times$ Ar2+/H | - | - | - | - | - | - | - | - | -
10${}^{6}\times$ Ar3+/H |  0.3$\pm$0.1 |  0.5$\pm$0.2 |  0.2$\pm$0.1 | - | - |  0.4$\pm$0.2 |  0.4$\pm$0.1 | - | -
10${}^{6}\times$ Ar4+/H | - | - | - | - | - | - | - | - | -
icf(Ar)(4) |  1.08$\pm$0.06 |  1.07$\pm$0.04 |  1.11$\pm$0.26 |  1.00$\pm$0.00 |  1.00$\pm$0.00 |  1.08$\pm$0.65 |  1.07$\pm$0.18 |  1.00$\pm$0.00 |  1.00$\pm$0.00
10${}^{6}\times$ Ar/H |  0.4$\pm$0.1 |  0.6$\pm$0.3 |  0.3$\pm$0.1 | - | - |  0.4$\pm$0.2 |  0.4$\pm$0.2 | - | -
10${}^{8}\times$ S+/H |  3.7$\pm$1.3 |  4.1$\pm$2.2 |  7.7$\pm$3.4 |  14.7$\pm$6.1 |  20.0$\pm$10.3 |  2.8$\pm$1.4 |  3.9$\pm$1.9 |  6.3$\pm$2.7 |  20.8$\pm$11.8
10${}^{6}\times$ S2+/H |  4.3$\pm$0.5 |  4.6$\pm$2.3 |  4.0$\pm$0.8 |  4.2$\pm$1.8 |  1.3$\pm$1.1 |  2.5$\pm$0.8 |  3.3$\pm$1.3 |  4.3$\pm$1.7 |  1.3$\pm$0.7
icf(S)(4) |  1.6$\pm$0.5 |  1.7$\pm$0.8 |  1.5$\pm$1.1 |  1.2$\pm$0.7 |  1.2$\pm$1.0 |  1.7$\pm$1.2 |  1.7$\pm$1.0 |  1.7$\pm$1.2 |  1.2$\pm$0.7
10${}^{6}\times$ S/H |  6.9$\pm$2.2 |  7.9$\pm$3.7 |  6.1$\pm$4.5 |  5.2$\pm$3.0 |  1.8$\pm$1.5 |  4.3$\pm$3.0 |  5.7$\pm$3.4 |  7.4$\pm$5.2 |  2.0$\pm$1.2
10${}^{7}\times$ Cl2+/H |  0.8$\pm$0.2 |  1.1$\pm$0.6 |  0.9$\pm$0.3 |  1.8$\pm$0.7 | - |  0.5$\pm$0.3 |  1.0$\pm$0.6 |  0.6$\pm$0.3 | -
icf(Cl) |  1.7$\pm$0.2 |  1.3$\pm$0.3 |  1.5$\pm$0.5 |  1.4$\pm$0.2 |  1.00$\pm$0.00 |  1.4$\pm$0.4 |  1.3$\pm$0.4 |  1.4$\pm$0.4 |  1.00$\pm$0.00
10${}^{7}\times$ Cl/H |  1.3$\pm$0.3 |  1.4$\pm$0.9 |  1.2$\pm$0.5 |  2.5$\pm$1.1 | - |  0.7$\pm$0.4 |  1.3$\pm$0.6 |  0.9$\pm$0.4 | -
(4)Calculated using Kingsburgh & Barlow (1994). When no S+2 is present, it was
calculated using $S^{+2}=S^{+}[4.677+(O^{+2}/O^{+})^{0.433}]$ from the same
work.

Table A3: Hen 2-186.

|  | PA=29
---|---|---
Line | Ion | A | Neb | B
|  | 5px-2” | 13px-5.2” | 5px-2”
3727.00 |  [O ii]b |  346$\pm$55 |  127$\pm$4 |  302$\pm$39
3868.75 |  [Ne iii] |  169$\pm$26 |  137$\pm$2 |  135$\pm$21
3889.05 |  He i+He i | - |  17.7$\pm$0.9 | -
3968.43 |  [Ne iii] |  60$\pm$15 |  28$\pm$2 |  39$\pm$13
3970.07 |  H i |  22$\pm$15 |  23$\pm$2 |  17$\pm$13
4101.74 |  H i |  27$\pm$8 |  33$\pm$1 |  22$\pm$7
4340.47 |  H i |  38.9$\pm$4.7 |  47.2$\pm$0.5 |  47.4$\pm$5.8
4363.21 |  [O iii] |  21.6$\pm$4.1 |  27.2$\pm$0.6 |  14.2$\pm$4.3
4471.50 |  He i | - |  4.0$\pm$0.2 | -
4685.68 |  He ii |  58.5$\pm$4.3 |  57.5$\pm$0.5 |  46.4$\pm$5.2
4711.37 |  [Ar iv] | - |  6.9$\pm$0.2 | -
4713.17 |  He i | - |  0.5$\pm$0.2 | -
4740.17 |  [Ar iv] | - |  7.9$\pm$0.2 | -
4861.33 |  H i | 100 | 100 | 100
4958.91 |  [O iii] |  629$\pm$14 |  543$\pm$1 |  535$\pm$12
5006.84 |  [O iii] |  1980$\pm$50 |  1400$\pm$10 |  1530$\pm$60
5517.66 |  [Cl iii] | - |  0.6$\pm$0.1 | -
5537.60 |  [Cl iii] | - |  1.0$\pm$0.1 | -
5577.34 |  [O i] | - |  0.4$\pm$0.1 | -
5754.60 |  [N ii] |  10.0$\pm$2.1 |  4.9$\pm$0.1 |  5.1$\pm$1.4
5875.66 |  He i |  15.8$\pm$2.6 |  12.4$\pm$0.2 |  14.9$\pm$1.9
6300.30 |  [O i] |  30.1$\pm$4.0 |  16.9$\pm$0.3 |  34.1$\pm$3.1
6312.10 |  [S iii] |  5.7$\pm$2.5 |  4.1$\pm$0.1 |  3.3$\pm$2.3
6363.78 |  [O i] |  11.3$\pm$2.2 |  5.9$\pm$0.2 |  9.7$\pm$2.4
6434.73 |  [Ar v] |  2.8$\pm$1.9 |  1.5$\pm$0.1 | -
6548.10 |  [N ii] |  119$\pm$8 |  73$\pm$1 |  137$\pm$10
6562.77 |  H i |  274$\pm$13 |  283$\pm$2 |  279$\pm$16
6583.50 |  [N ii] |  355$\pm$23 |  222$\pm$1 |  395$\pm$26
6678.16 |  He i |  2.1$\pm$1.5 |  3.4$\pm$0.1 |  4.0$\pm$1.8
6716.44 |  [S ii] |  21.6$\pm$2.7 |  10.3$\pm$0.3 |  28.1$\pm$3.0
6730.82 |  [S ii] |  27.6$\pm$2.9 |  17.3$\pm$0.2 |  32.3$\pm$3.1
7135.80 |  [Ar iii] |  18.6$\pm$3.0 |  20.1$\pm$0.3 |  18.7$\pm$2.7
$log~{}F(H\beta)$ | $-14.68$ | $-12.58$ | $-14.87$
$c(H\beta)$ | $0.69\pm 0.08$ |  0.74$\pm$0.01 | $0.67\pm 0.08$
Electron densities (cm-3) and temperatures (K)
Ne[S ii] | $1710\pm 297$ |  3990$\pm$125 |  1070$\pm$152
Ne[Cl iii] | - |  8070$\pm$1569 | -
Ne[Ar iv] | - |  5420$\pm$209 | -
Te[N ii] | $13000\pm 2684$ |  11300$\pm$237 |  9280$\pm$2027
Te[O i] | - |  12700$\pm$3181 | -
Te[O iii] | $11900\pm 2177$ |  14600$\pm$331 |  11200$\pm$3217

Table A4: Ionic and total abundances of Hen 2-186.

| PA=29
---|---
Abundances | A | Neb | B
10${}^{1}\times$ He+/H |  0.92$\pm$0.20 |  0.68$\pm$0.02 |  1.01$\pm$0.20
10${}^{2}\times$ He2+/H |  4.9$\pm$0.4 |  5.02$\pm$0.04 |  3.8$\pm$0.5
10${}^{1}\times$ He/H |  1.41$\pm$0.20 |  1.18$\pm$0.02 |  1.40$\pm$0.20
10${}^{5}\times$ N+/H |  3.9$\pm$0.8 |  3.3$\pm$0.2 |  10.0$\pm$3.9
icf(N) |  5.4$\pm$1.6 |  4.9$\pm$0.5 |  2.9$\pm$1.3
10${}^{4}\times$ N/H |  2.1$\pm$0.4 |  1.6$\pm$0.1 |  3.0$\pm$0.9
10${}^{5}\times$ O0/H |  2.3$\pm$0.7 |  1.9$\pm$0.2 |  7.8$\pm$2.3
10${}^{4}\times$ O+/H |  1.0$\pm$0.3 |  0.53$\pm$0.08 |  2.2$\pm$0.8
10${}^{4}\times$ O2+/H |  3.8$\pm$0.7 |  1.65$\pm$0.05 |  3.6$\pm$0.9
icf(O) |  1.31$\pm$0.07 |  1.44$\pm$0.02 |  1.21$\pm$0.05
10${}^{4}\times$ O/H |  6.5$\pm$1.1 |  3.1$\pm$0.1 |  7.7$\pm$1.9
10${}^{5}\times$ Ne2+/H |  9.8$\pm$2.3 |  3.9$\pm$0.1 |  9.4$\pm$2.9
icf(Ne) |  1.31$\pm$0.08 |  1.45$\pm$0.02 |  1.22$\pm$0.05
10${}^{4}\times$ Ne/H |  1.3$\pm$0.3 |  0.6$\pm$0.1 |  1.1$\pm$0.7
10${}^{6}\times$ Ar2+/H |  1.2$\pm$0.3 |  0.9$\pm$0.1 |  1.3$\pm$0.3
10${}^{7}\times$ Ar3+/H | - |  7.3$\pm$0.3 | -
10${}^{7}\times$ Ar4+/H |  7.8$\pm$5.2 |  2.7$\pm$0.2 | -
icf(Ar)(5) |  1.00$\pm$0.30 |  1.19$\pm$0.23 |  1.87$\pm$0.01
10${}^{6}\times$ Ar/H |  2.0$\pm$0.5 |  2.2$\pm$0.1 |  2.5$\pm$0.8
10${}^{7}\times$ S+/H |  7.8$\pm$1.7 |  6.9$\pm$0.5 |  19.2$\pm$4.5
10${}^{6}\times$ S2+/H |  6.8$\pm$3.1 |  2.5$\pm$0.1 |  5.0$\pm$3.6
icf(S)(5) |  1.4$\pm$0.5 |  1.3$\pm$0.2 |  1.2$\pm$0.5
10${}^{6}\times$ S/H |  10.6$\pm$3.8 |  4.1$\pm$0.6 |  8.3$\pm$3.4
10${}^{8}\times$ Cl2+/H | - |  4.5$\pm$0.5 | -
icf(Cl) |  1.00$\pm$0.00 |  2.01$\pm$0.04 |  1.00$\pm$0.00
10${}^{8}\times$ Cl/H | - |  9.0$\pm$1.1 | -
(5)Calculated using Kingsburgh & Barlow (1994)

Table A5: Hen 2-429.

|  | PA=89
---|---|---
Line | Ion | Neb |  B(6) | A
|  | 15px-10.5” | 5px-3.5” | 5px-3.5”
3727.00 |  [O ii]b |  121$\pm$12 |  347$\pm$129 |  368$\pm$99
3868.75 |  [Ne iii] |  30$\pm$5 | - | -
3889.05 |  He i+He i |  23$\pm$4 | - | -
3968.43(7) |  [Ne iii]+H i |  28$\pm$4 | - | -
4101.74 |  H i |  27$\pm$4 | - | -
4340.47 |  H i |  51$\pm$4 | - | -
4363.21 |  [O iii] |  4$\pm$1 | - | -
4471.50 |  He i |  7$\pm$1 | - | -
4685.68 |  He ii |  15$\pm$1 | - | -
4861.33 |  H i | 100 | 100 | 100
4958.91 |  [O iii] |  184$\pm$3 |  244$\pm$31 |  196$\pm$26
5006.84 |  [O iii] |  562$\pm$5 |  655$\pm$46 |  594$\pm$45
5517.66 |  [Cl iii] |  0.8$\pm$0.3 | - | -
5537.60 |  [Cl iii] |  1.1$\pm$0.3 | - | -
5754.60 |  [N ii] |  4.0$\pm$0.3 | - | -
5875.66 |  He i |  21.5$\pm$0.6 |  13.2$\pm$7.8 |  13.7$\pm$4.6
6300.30 |  [O i] |  4.5$\pm$0.2 |  6.9$\pm$2.7 |  9.3$\pm$3.8
6312.10 |  [S iii] |  2.5$\pm$0.2 |  3.1$\pm$2.1 | -
6363.78 |  [O i] |  1.5$\pm$0.1 | - | -
6548.10 |  [N ii] |  88$\pm$2 |  168$\pm$23 |  131$\pm$22
6562.77 |  H i |  287$\pm$6 |  271$\pm$35 |  272$\pm$36
6583.50 |  [N ii] |  271 $\pm$6 |  417$\pm$58 |  363$\pm$57
6678.16 |  He i |  5.5$\pm$0.3 |  4.8$\pm$3.6 |  8.9$\pm$2.7
6716.44 |  [S ii] |  8.6$\pm$0.3 |  9.6$\pm$3.6 |  15.4$\pm$3.2
6730.82 |  [S ii] |  16.0$\pm$0.5 |  16.5$\pm$3.6 |  24.8$\pm$4.1
$log~{}F(H\beta)$ | $-13.04$ | $-15.26$ | $-15.26$
$c(H\beta)$ | $2.12\pm 0.03$ | $2.11\pm 0.19$ |  2.02$\pm$0.20
Electron densities (cm-3) and temperatures (K)
Ne[S ii] | $5710\pm 267$ |  4310$\pm$1870 |  3200$\pm$850
Ne[Cl iii] | $5150\pm 2388$ | - | -
Te[N ii] | $9390\pm 723$ | - | -
Te[O iii] | $9790\pm 2449$ | - | -
|  Stellar line fluxes from CSPN (erg/s/cm2) | FWHM (Å)
C iii $\lambda$4650 |  (3.19$\pm$0.49)$\times 10^{-14}$ |  33$\pm$5
C iv $\lambda$5470 |  (7.51$\pm$1.40)$\times 10^{-15}$ |  36$\pm$8
O iii $\lambda$5592 |  (6.85$\pm$1.80)$\times 10^{-15}$ |  40$\pm$16
C iv $\lambda\lambda$5810,5812 |  (1.40$\pm$0.04)$\times 10^{-13}$ |  38$\pm$1
(6)A problem is detected in the H$\beta$ line of this LIS, so the proposed
solution was to use the
F(H$\beta$) of the other LIS (A), therefore, the results found should be taken
with caution.
(7)Separation of these two emission lines was not possible in this case.

Table A6: Ionic and total abundances of Hen 2-429.

| PA=89
---|---
Abundances | Neb |  B(8) |  A(9)
10${}^{1}\times$ He+/H |  1.39$\pm$0.09 |  0.98$\pm$0.50 |  1.23$\pm$0.29
10${}^{2}\times$ He2+/H |  1.21$\pm$0.09 | - | -
10${}^{1}\times$ He/H |  1.51$\pm$0.09 |  0.98$\pm$0.50 |  1.23$\pm$0.29
10${}^{5}\times$ N+/H |  6.9$\pm$0.6 |  12.3$\pm$9.1 |  9.9$\pm$1.4
icf(N) |  3.1$\pm$0.7 |  3.6$\pm$2.2 |  3.6$\pm$1.3
10${}^{4}\times$ N/H |  2.1$\pm$0.4 |  4.3$\pm$1.4 |  3.5$\pm$1.5
10${}^{5}\times$ O0/H |  1.0$\pm$0.1 |  5.0$\pm$1.4 |  3.3$\pm$1.3
10${}^{4}\times$ O+/H |  1.1$\pm$0.2 |  3.0$\pm$1.3 |  2.7$\pm$1.3
10${}^{4}\times$ O2+/H |  2.1$\pm$0.6 |  2.6$\pm$0.2 |  2.2$\pm$0.2
icf(O) |  1.05$\pm$0.01 |  1.00$\pm$0.00 |  1.00$\pm$0.00
10${}^{4}\times$ O/H |  3.4$\pm$0.7 |  5.5$\pm$1.3 |  4.9$\pm$1.3
10${}^{5}\times$ Ne2+/H |  3.5$\pm$1.2 | - | -
icf(Ne) |  1.05$\pm$0.01 |  1.00$\pm$0.00 |  1.00$\pm$0.00
10${}^{5}\times$ Ne/H |  3.6$\pm$1.2 | - | -
10${}^{7}\times$ Ar3+/H | - | - | -
icf(Ar)(10) |  1.00$\pm$0.00 |  1.00$\pm$0.00 |  1.00$\pm$0.00
10${}^{7}\times$ Ar/H | - | - | -
10${}^{6}\times$ S+/H |  1.2$\pm$0.1 |  1.3$\pm$0.4 |  1.7$\pm$0.6
10${}^{6}\times$ S2+/H |  6.4$\pm$2.2 |  8.6$\pm$5.8 |  6.4$\pm$3.1
icf(S)(10) |  1.1$\pm$0.3 |  1.0$\pm$0.2 |  1.0$\pm$0.5
10${}^{6}\times$ S/H |  8.4$\pm$2.3 |  9.9$\pm$2.0 |  11.2$\pm$5.6
10${}^{7}\times$ Cl2+/H |  1.4$\pm$0.9 | - | -
icf(Cl) |  1.39$\pm$0.02 |  1.00$\pm$0.00 |  1.00$\pm$0.00
10${}^{7}\times$ Cl/H |  2.0$\pm$0.7 | - | -
(8)Estimated using Te for [N ii] and [O iii] from Neb
(9)Estimated using Te for [N ii] and [O iii] from Neb
(10)Calculated using Kingsburgh & Barlow (1994). When no S+2
is present, it was calculated using
$S^{+2}=S^{+}[4.677+(O^{+2}/O^{+})^{0.433}]$
from the same work.

Table A7: NGC 3918

|  | PA=30 | PA=70 | PA=40 | PA=42
---|---|---|---|---|---
Line | Ion | Neb | Rim | Rim1 | Neb | Rim2 | B’ | B | B” | A’ | A
|  | 42px-16.8” | 4px-1.6” | 3px-1.2” | 42px-16.8” | 3px-1.2” | 3px-1.2” | 6px-2.4” | 4px-1.6” | 3px-1.2” | 5px-2”
3727.00 |  [O ii]b |  76 $\pm$ 2 |  86 $\pm$ 2 |  82 $\pm$ 2 |  72 $\pm$ 2 |  64 $\pm$ 2 |  118 $\pm$ 21 |  174 $\pm$ 20 |  89 $\pm$ 22 |  370 $\pm$ 15 |  222 $\pm$ 9
3868.75 |  [Ne iii] |  122 $\pm$ 1 |  122 $\pm$ 2 |  147 $\pm$ 2 |  121 $\pm$ 2 |  126 $\pm$ 2 |  156 $\pm$ 12 |  151 $\pm$ 12 |  59 $\pm$ 12 |  169$\pm$ 11 |  162 $\pm$ 7
3889.05 |  H i+He i |  18.4 $\pm$ 0.5 |  16.9 $\pm$ 0.7 |  20.7 $\pm$ 0.7 |  18.9 $\pm$ 0.7 |  17.9 $\pm$ 0.5 |  15.3 $\pm$ 4.3 |  29.8 $\pm$ 6.1 | - |  22.2 $\pm$3.5 |  22.5 $\pm$2.2
3967.46 |  [Ne iii] |  33.8 $\pm$0.6 |  34.2 $\pm$ 1.0 |  40.5 $\pm$ 1.1 |  34.3 $\pm$ 0.9 |  36.6$\pm$1.0 |  65.6 $\pm$9.2 |  48.9 $\pm$6.8 | - |  43.4 $\pm$3.8 |  46.7$\pm$3.1
3970.07 |  H i |  18.2$\pm$0.6 |  18.3$\pm$1.0 |  18.3$\pm$1.0 |  18.0$\pm$0.9 |  17.7$\pm$1.0 |  18.2$\pm$9.3 |  17.7$\pm$6.6 |  18.2$\pm$8.4 |  18.7$\pm$3.5 |  18.0$\pm$3.2
4101.74 |  H i |  27.5 $\pm$ 0.5 |  24.8 $\pm$ 0.5 |  25.9 $\pm$ 0.6 |  26.9 $\pm$ 0.5 |  27.2 $\pm$ 0.6 |  25.1 $\pm$3.9 |  26.4 $\pm$2.6 |  25.5 $\pm$6.0 |  24.7$\pm$5.2 |  26.7$\pm$1.0
4267.15 |  C ii |  0.6$\pm$0.2 | - |  0.6$\pm$0.2 |  0.5$\pm$0.2 |  0.5$\pm$0.2 | - | - | - | - | -
4340.47 |  H i |  47.6 $\pm$ 0.4 |  45.4 $\pm$ 0.5 |  44.4 $\pm$ 0.5 |  45.9 $\pm$ 0.5 |  46.7 $\pm$ 0.5 |  47.0 $\pm$3.6 |  47.5 $\pm$3.3 |  46.5$\pm$6.4 |  43.3$\pm$5.7 |  46.3$\pm$1.3
4363.21 |  [O iii] |  20.1 $\pm$ 0.3 |  17.9 $\pm$ 0.3 |  18.9 $\pm$ 0.4 |  20.1 $\pm$ 0.3 |  22.1 $\pm$ 0.4 |  22.9 $\pm$2.8 |  23.0 $\pm$2.6 |  25.3 $\pm$5.8 |  18.3 $\pm$1.4 |  23.3$\pm$1.1
4471.50 |  He i |  3.7 $\pm$ 0.2 |  4.6 $\pm$ 0.2 |  3.9 $\pm$ 0.2 |  3.3 $\pm$ 0.2 |  3.9 $\pm$ 0.2 |  4.6 $\pm$1.5 |  4.9 $\pm$ 1.5 | - |  5.0 $\pm$1.2 |  4.5 $\pm$ 0.6
4647.40 |  C iii |  6.3$\pm$0.2 |  4.9$\pm$0.2 |  1.8$\pm$0.1 |  5.2$\pm$0.1 |  6.2$\pm$0.2 | - | - | - | - | -
4685.68 |  He ii |  47.1 $\pm$ 0.4 |  19.9 $\pm$ 0.3 |  24.7 $\pm$ 0.3 |  48.9 $\pm$ 0.4 |  46.2 $\pm$ 0.4 |  10.1 $\pm$ 1.8 |  22.6 $\pm$1.8 |  29.0 $\pm$4.3 |  14.8$\pm$1.2 |  29.0 $\pm$ 0.9
4711.37 |  [Ar iv] |  7.6 $\pm$ 0.1 |  4.7 $\pm$ 0.2 |  4.7 $\pm$ 0.2 |  8.0 $\pm$ 0.2 |  8.5 $\pm$ 0.2 |  4.9$\pm$1.4 |  6.2 $\pm$1.3 |  5.6$\pm$3.4 |  3.7 $\pm$ 0.7 |  5.4 $\pm$ 0.4
4713.17 |  He i |  0.5 $\pm$ 0.1 |  0.6 $\pm$ 0.2 |  0.5 $\pm$ 0.2 |  0.5 $\pm$ 0.2 |  0.5 $\pm$ 0.2 | - | - | - | - |  0.6 $\pm$ 0.4
4740.17 |  [Ar iv] |  8.3 $\pm$ 0.2 |  4.8 $\pm$ 0.2 |  4.9 $\pm$ 0.2 |  8.6 $\pm$ 0.2 |  8.9 $\pm$ 0.2 | - | - | - |  3.5 $\pm$ 0.7 |  4.3 $\pm$ 0.5
4861.33 |  H i | 100 | 100 | 100 | 100 | 100 | 100 | 100 | 100 | 100 | 100
4958.91 |  [O iii] |  506 $\pm$ 1 |  515 $\pm$ 1 |  578 $\pm$ 1 |  515 $\pm$ 1 |  579 $\pm$ 1 |  624 $\pm$ 8 |  595 $\pm$ 8 |  353 $\pm$ 11 |  511 $\pm$ 6 |  610 $\pm$ 5
5006.84 |  [O iii] |  1520 $\pm$ 10 |  1570 $\pm$ 10 |  1640 $\pm$ 10 |  1520 $\pm$ 10 |  1670 $\pm$ 10 |  1820 $\pm$ 20 |  1780 $\pm$ 20 |  1080 $\pm$20 |  1470 $\pm$ 10 |  1800 $\pm$ 10
5200.26 |  [N i] |  0.7 $\pm$ 0.1 |  0.6 $\pm$ 0.1 |  0.8 $\pm$ 0.2 |  0.7 $\pm$ 0.1 |  0.5 $\pm$ 0.1 | - |  4.1 $\pm$ 1.0 | - |  7.9 $\pm$ 0.7 |  3.9 $\pm$ 0.4
5411.52 |  He ii |  3.6 $\pm$ 0.1 |  1.1 $\pm{0.1}$ |  2.3 $\pm$ 0.1 |  3.9 $\pm$ 0.1 |  3.2 $\pm$ 0.1 | - |  1.9 $\pm$ 0.6 | - |  1.6 $\pm$ 0.5 |  2.3 $\pm$ 0.3
5517.66 |  [Cl iii] |  0.56 $\pm$0.08 |  0.74 $\pm{0.08}$ |  0.61 $\pm$ 0.09 |  0.55 $\pm$ 0.09 |  0.75 $\pm$0.09 | - | - | - | - |  1.19 $\pm$0.29
5537.60 |  [Cl iii] |  0.81 $\pm$0.09 |  0.85 $\pm{0.09}$ |  0.89 $\pm$ 0.09 |  0.81 $\pm$ 0.11 |  1.04 $\pm$0.09 | - | - | - | - |  0.97$\pm$0.25
5754.60 |  [N ii] |  1.8 $\pm$ 0.1 |  1.8 $\pm{0.1}$ |  2.0 $\pm$ 0.1 |  1.6 $\pm$ 0.1 |  1.3 $\pm$ 0.1 |  1.8 $\pm$0.7 |  4.2 $\pm$ 0.9 |  3.5$\pm$1.6 |  5.3 $\pm$ 0.7 |  3.9 $\pm$ 0.4
5812.14 |  C iv |  0.29$\pm$0.09 | - | - |  0.13$\pm$0.09 | - | - | - | - | - | -
5875.66 |  He i |  10.5 $\pm$ 0.2 |  11.8 $\pm$ 0.2 |  13.2 $\pm$ 0.2 |  10.4 $\pm$ 0.2 |  11.7 $\pm$ 0.2 |  13.0 $\pm$1.7 |  10.2 $\pm$ 1.3 |  13.5$\pm$2.7 |  15.3 $\pm$ 0.9 |  13.1 $\pm$ 0.6
6300.30 |  [O i] |  5.6 $\pm$ 0.1 |  4.6 $\pm$ 0.2 |  6.4 $\pm$ 0.2 |  4.7 $\pm$ 0.2 |  3.4 $\pm$ 0.1 |  8.5$\pm$1.5 |  14.5 $\pm$1.7 |  18.1 $\pm$2.1 |  33.5 $\pm$1.8 |  20.9 $\pm$ 0.9
6312.10 |  [S iii] |  2.3 $\pm$ 0.1 |  2.1 $\pm$ 0.1 |  2.7 $\pm$ 0.1 |  2.4 $\pm$ 0.1 |  2.3 $\pm$ 0.1 | - |  1.4 $\pm$ 0.5 |  5.4$\pm$1.8 |  2.7 $\pm$ 0.5 |  2.4 $\pm$ 0.3
6363.77 |  [O i] |  1.93 $\pm$ 0.09 |  1.52 $\pm$0.09 |  2.20 $\pm$ 0.11 |  1.58 $\pm$ 0.09 |  1.16$\pm$ 0.10 | - |  5.0 $\pm$0.9 | - |  11.4 $\pm$ 0.9 |  6.94$\pm$0.55
6434.73 |  [Ar v] |  1.27 $\pm$ 0.08 | - |  0.41 $\pm$0.07 |  1.20 $\pm$0.09 |  0.44 $\pm$0.07 | - | - | - | - | -
6548.10 |  [N ii] |  26.3 $\pm$ 0.2 |  29.0 $\pm$ 0.3 |  30.9 $\pm$ 0.3 |  23.8 $\pm$ 0.3 |  20.8 $\pm$ 0.3 |  42.7 $\pm$2.8 |  63.8$\pm$3.1 |  71.1$\pm$6.1 |  95.9$\pm$4.8 |  64.3 $\pm$1.5
6562.77 |  H i |  284 $\pm$ 1 |  277 $\pm$ 1 |  277 $\pm$ 1 |  280 $\pm$ 1 |  281 $\pm$ 1 |  280 $\pm$ 9 |  282 $\pm$ 8 |  273 $\pm$ 13 |  274 $\pm$ 10 |  281 $\pm$ 4
6583.50 |  [N ii] |  84.1 $\pm$ 0.5 |  87.4 $\pm$ 0.6 |  89.5 $\pm$ 0.6 |  69.9 $\pm$ 0.6 |  60.3 $\pm$ 0.5 |  131.0 $\pm$ 5.0 |  198.0$\pm$ 8.0 |  214.0$\pm$13.0 |  274.0 $\pm$13.0 |  191.0 $\pm$3.0
6678.16 |  He i |  2.9 $\pm$ 0.1 |  3.1 $\pm$ 0.1 |  3.3 $\pm$ 0.1 |  2.8 $\pm$ 0.1 |  3.3 $\pm$ 0.1 |  3.5 $\pm$0.9 |  3.6 $\pm$ 0.9 |  3.9$\pm$1.9 |  4.1 $\pm$ 0.6 |  3.3 $\pm$ 0.4
6716.44 |  [S ii] |  2.8 $\pm$ 0.1 |  3.7 $\pm$ 0.1 |  3.8 $\pm$ 0.1 |  2.3 $\pm$ 0.1 |  2.5 $\pm$ 0.1 |  6.3 $\pm$ 1.0 |  8.2 $\pm$1.1 |  11.4 $\pm$1.9 |  22.5 $\pm$1.6 |  10.5 $\pm$ 0.5
6730.82 |  [S ii] |  5.0 $\pm$ 0.1 |  6.7 $\pm$ 0.2 |  6.9 $\pm$ 0.2 |  4.2 $\pm$ 0.1 |  4.6 $\pm$ 0.1 |  8.2 $\pm$ 1.0 |  11.2 $\pm$1.3 |  15.5$\pm$1.9 |  27.3$\pm$1.7 |  13.9 $\pm$ 0.5
$log~{}F(H\beta)$ | $-10.91$ | $-12.14$ | $-12.25$ | $-11.04$ | $-12.25$ | $-13.86$ | $-13.46$ | $-14.11$ | $-14.28$ | $-13.75$
$c(H\beta)$ | ${0.29}\pm{0.01}$ | ${0.29}\pm{0.01}$ | ${0.30}\pm{0.01}$ | ${0.28}\pm{0.01}$ | ${0.25}\pm{0.01}$ | ${0.30}\pm{0.05}$ | ${0.25}\pm{0.04}$ | ${0.28}\pm{0.08}$ | ${0.33}\pm{0.05}$ | ${0.27}\pm{0.02}$
Electron densities (cm-3) and temperatures (K)
Ne[S ii] | ${5070}\pm{220}$ | ${5720}\pm 250$ | ${5450}\pm{220}$ | ${5380}\pm 310$ | ${5710}\pm 290$ | ${1620}\pm{324}$ | ${2030}\pm 360$ | ${1920}\pm{397}$ | ${1340}\pm 127$ | ${1860}\pm 111$
Ne[Cl iii] | ${5590}\pm{1028}$ | ${3060}\pm 460$ | ${5600}\pm{980}$ | ${5780}\pm 1210$ | ${4810}\pm 800$ | - | - | - | - |  702$\pm$249
Ne[Ar iv] | ${4300}\pm{77}$ | ${3670}\pm 219$ | ${3790}\pm{223}$ | ${4140}\pm 141$ | ${3780}\pm 123$ | - | - | - |  2300$\pm$633 | -
Te[N ii] | ${11100}\pm{530}$ | ${10700}\pm 620$ | ${11300}\pm{520}$ | ${11200}\pm{820}$ | ${11000}\pm 980$ | ${9430}\pm{3675}$ | ${11300}\pm 2675$ | ${10000}\pm{4660}$ | ${10900}\pm{1520}$ | ${11100}\pm 1380$
Te[O iii] | ${12700}\pm{170}$ | ${12100}\pm 220$ | ${12000}\pm{250}$ | ${12700}\pm{210}$ | ${12700}\pm 240$ | ${12500}\pm{1600}$ | ${12600}\pm 1550$ | ${16300}\pm{3800}$ | ${12400}\pm{890}$ | ${12700}\pm 600$

Table A8: Ionic and total abundances of NGC 3918.

| PA=30 | PA=70 | PA=40 | PA=42
---|---|---|---|---
Abundances | Neb | Rim | Rim1 | Neb | Rim2 | B’ | B | B” | A’ | A
| 42px-16.8” | 4px-1.6” | 3px-1.2” | 42px-16.8” | 3px-1.2” | 3px-1.2” | 6px-2.4” | 4px-1.6” | 3px-1.2” | 5px-2”
10${}^{2}\times$ He+/H | $6.4\pm 0.1$ | ${7.6}\pm 0.2$ | $7.8\pm 0.2$ | $6.1\pm 0.2$ | $7.1\pm 0.2$ | $8.5\pm 1.1$ | $8.7\pm 1.0$ | $7.9\pm 1.7$ | $9.9\pm 1.4$ | $8.9\pm 0.7$
10${}^{2}\times$ He2+/H | $4.02\pm 0.03$ | $1.66\pm 0.02$ | $2.13\pm 0.03$ | $4.19\pm 0.03$ | $3.91\pm 0.03$ | $0.90\pm 0.20$ | $1.90\pm 0.20$ | $2.50\pm 0.40$ | $1.30\pm 0.10$ | $2.46\pm 0.07$
10${}^{2}\times$ He/H | $10.4\pm 0.1$ | $9.3\pm 0.2$ | $9.9\pm 0.2$ | $10.3\pm 0.2$ | $11.0\pm 0.2$ | $9.4\pm 1.1$ | $10.6\pm 1.0$ | $10.3\pm 1.7$ | $11.3\pm 1.3$ | $11.3\pm 0.7$
10${}^{5}\times$ N+/H | ${1.4}\pm 0.1$ | ${1.6}\pm 0.1$ | $1.4\pm 0.1$ | $1.1\pm 0.1$ | $1.0\pm 0.1$ | ${3.1}\pm 2.1$ | $3.0\pm 1.0$ | $4.3\pm 1.5$ | $4.6\pm 0.7$ | $3.1\pm 0.4$
icf(N) | ${9.7}\pm 1.2$ | ${8.0}\pm 1.2$ | $10.7\pm 1.3$ | $10.7\pm 1.8$ | $11.3\pm 1.9$ | $5.7\pm 2.7$ | $6.9\pm 2.4$ | $3.4\pm 1.5$ | $3.4\pm 0.6$ | $5.6\pm 0.9$
10${}^{5}\times$ N/H | ${13.2}\pm 0.9$ | ${12.4}\pm 1.0$ | $15.3\pm 1.1$ | $12.0\pm 1.1$ | $11.6\pm 1.1$ | ${18.3}\pm 3.8$ | $20.8\pm 3.9$ | $16.4\pm 3.9$ | $15.7\pm 1.6$ | $17.0\pm 1.3$
10${}^{6}\times$ O0/H | ${7.2}\pm 0.6$ | ${6.5}\pm 0.7$ | $7.8\pm 0.7$ | $5.7\pm 0.8$ | $4.5\pm 0.7$ | $18.6\pm 7.7$ | $17.2\pm 5.1$ | $31.3\pm 13.9$ | $45.0\pm 8.2$ | $26.2\pm 5.1$
10${}^{5}\times$ O+/H | ${3.3}\pm 0.5$ | ${4.4}\pm 0.6$ | $3.4\pm 0.5$ | $3.0\pm 0.7$ | $2.9\pm 0.7$ | ${7.3}\pm 3.5$ | $5.3\pm 1.9$ | $4.2\pm 2.2$ | $11.6\pm 3.0$ | $6.9\pm 1.6$
10${}^{4}\times$ O2+/H | ${2.48}\pm 0.04$ | ${2.94}\pm 0.06$ | $3.18\pm 0.08$ | $2.50\pm 0.05$ | $2.75\pm 0.06$ | $3.14\pm 0.48$ | $2.95\pm 0.41$ | $0.93\pm 0.33$ | $2.61\pm 0.23$ | $2.98\pm 0.16$
icf(O) | ${1.37}\pm{0.01}$ | ${1.12}\pm{0.01}$ | $1.15\pm 0.01$ | $1.39\pm 0.01$ | $1.32\pm 0.01$ | ${1.06}\pm 0.01$ | $1.12\pm 0.02$ | $1.18\pm 0.07$ | $1.07\pm 0.01$ | $1.16\pm 0.01$
10${}^{4}\times$ O/H | ${3.8}\pm 0.1$ | ${3.8}\pm 0.1$ | $4.1\pm 0.1$ | $3.9\pm 0.1$ | $4.0\pm 0.1$ | ${4.2}\pm 0.6$ | $4.0\pm 0.7$ | $1.7\pm 0.5$ | $4.1\pm 0.4$ | $4.2\pm 0.3$
10${}^{5}\times$ Ne2+/H | ${5.4}\pm 0.1$ | ${6.5}\pm 0.2$ | $7.8\pm 0.2$ | $5.4\pm 0.1$ | $5.6\pm 1.5$ | ${8.3}\pm 1.5$ | $7.1\pm 1.2$ | $1.2\pm 0.6$ | $8.0\pm 0.9$ | $7.3\pm 0.5$
icf(Ne) | ${1.37}\pm{0.01}$ | ${1.12}\pm{0.01}$ | $1.15\pm 0.01$ | $1.40\pm 0.01$ | $1.32\pm 0.01$ | ${1.06}\pm 0.01$ | $1.12\pm 0.02$ | $1.18\pm 0.07$ | $1.08\pm 0.01$ | $1.16\pm 0.01$
10${}^{5}\times$ Ne/H | ${7.4}\pm 0.2$ | ${7.2}\pm 0.2$ | $9.0\pm 0.3$ | $7.6\pm 0.2$ | $7.4\pm 0.2$ | ${8.8}\pm 1.6$ | $8.0\pm 1.3$ | $1.4\pm 0.7$ | $8.6\pm 0.9$ | $8.4\pm 0.6$
10${}^{6}\times$ Ar3+/H | ${1.12}\pm 0.03$ | $0.77\pm 0.02$ | $0.79\pm 0.03$ | $1.18\pm 0.04$ | $1.23\pm 0.04$ | $0.67\pm 0.22$ | $0.83\pm 0.23$ | $0.38\pm 0.24$ | $0.53\pm 0.09$ | $0.67\pm 0.06$
10${}^{7}\times$ Ar4+/H | ${3.07}\pm 0.20$ | - | $1.13\pm 0.19$ | $2.92\pm 0.23$ | $1.07\pm 0.16$ | - | - | - | - | -
icf(Ar)(11) | ${1.00}\pm{0.00}$ | ${1.29}\pm{0.35}$ | $1.00\pm 0.00$ | $1.00\pm 0.00$ | $1.00\pm 0.00$ | $1.29\pm{0.32}$ | $1.33\pm 0.14$ | $1.67\pm 0.31$ | $1.52\pm 0.13$ | $1.42\pm 0.07$
10${}^{6}\times$ Ar/H | ${1.43}\pm 0.04$ | $0.99\pm 0.40$ | $0.91\pm 0.04$ | $1.48\pm 0.05$ | $1.34\pm 0.04$ | $0.89\pm 0.27$ | $1.12\pm 0.33$ | $0.71\pm 0.45$ | $0.82\pm 0.15$ | $0.96\pm 0.09$
10${}^{7}\times$ S+/H | ${2.3}\pm 0.3$ | ${3.5}\pm 0.4$ | $3.2\pm 0.3$ | $1.9\pm 0.3$ | $2.3\pm 0.4$ | $4.8\pm 3.2$ | $4.3\pm 1.7$ | $7.9\pm 2.8$ | $10.9\pm 1.7$ | $5.4\pm 0.8$
10${}^{6}\times$ S+2/H |  2.2$\pm$0.1 |  2.4$\pm$0.2 |  3.2$\pm$0.2 |  2.3$\pm$0.1 |  2.2$\pm$0.1 |  1.3$\pm$0.6 |  1.4$\pm$0.6 |  2.3$\pm$0.9 |  2.8$\pm$0.6 |  2.3$\pm$0.4
icf(S)(11) |  1.6$\pm$0.2 |  1.5$\pm$0.2 |  1.6$\pm$0.2 |  1.7 $\pm$0.4 |  1.7 $\pm$0.4 |  1.3$\pm$0.7 |  1.4$\pm$0.6 |  1.2$\pm$0.7 |  1.2$\pm$0.3 |  1.3$\pm$0.3
10${}^{6}\times$ S/H |  3.9$\pm$0.5 |  4.1$\pm$0.5 |  5.6$\pm$0.7 |  4.2$\pm$1.0 |  4.1$\pm$ 1.0 |  2.3$\pm$1.2 |  2.6$\pm$1.1 |  3.7$\pm$2.2 |  4.7$\pm$1.2 |  3.7$\pm$0.9
10${}^{8}\times$ Cl2+/H | ${4.8}\pm 0.5$ | ${6.1}\pm 0.5$ | $6.1\pm 0.5$ | $4.9\pm 0.6$ | $6.2\pm 0.5$ | - | - | - | - | $6.9\pm 1.3$
icf(Cl) | ${2.19}\pm{0.06}$ | ${1.76}\pm{0.05}$ | $1.92\pm 0.05$ | $2.28\pm 0.09$ | $2.19\pm 0.09$ | $1.00\pm{0.00}$ | $1.00\pm 0.00$ | $1.00\pm 0.00$ | $1.00\pm 0.00$ | $1.69\pm 0.06$
10${}^{8}\times$ Cl/H | ${10.5}\pm 1.1$ | ${10.7}\pm 1.0$ | $11.6\pm 1.1$ | $11.0\pm 1.4$ | $13.7\pm 1.1$ | - | - | - | - | $11.6\pm 2.2$
(11)Calculated using Kingsburgh & Barlow (1994). When no S+2 is present, it
was calculated using $S^{+2}=S^{+}[4.677+(O^{+2}/O^{+})^{0.433}]$ from the
same work.

Table A9: NGC 6543

|  | PA=5 |  PA=163(12)
---|---|---|---
Line | Ion | J | D | A | Neb | A’ | D’ | J’ | D | A | Neb | A’ | D’
|  | 9px-6.3” | 5px-3.5” | 5px-3.5” | 33px-23.1” | 5px-3.5” | 5px-3.5” | 9px-6.3” | 5px-3.5” | 5px-3.5” | 33px-23.1” | 5px-3.5” | 5px-3.5”
3727.00 |  [O ii]b |  103 $\pm$ 19 |  79 $\pm$2 |  24 $\pm$ 1 |  38$\pm$1 |  22.4$\pm$0.6 |  77$\pm$1 |  106$\pm$17 |  39$\pm$1 |  14$\pm$1 |  22$\pm$1 |  23$\pm$1 |  31$\pm$1
3868.75 |  [Ne iii] |  67.6 $\pm$11.8 |  52.1$\pm$1.0 |  47.4 $\pm$ 0.5 |  55.1$\pm$0.9 |  50.1$\pm$0.5 |  57.6$\pm$0.7 |  72.6$\pm$8.6 |  50.2$\pm$0.9 |  47.6$\pm$0.4 |  40.3$\pm$0.6 |  45.9$\pm$0.4 |  44.2$\pm$1.2
3889.05 |  H i+He i |  25.8 $\pm$8.1 |  20.4$\pm$0.7 |  18.2 $\pm$ 0.3 |  20.5$\pm$0.5 |  19.5$\pm$0.3 |  19.4$\pm$0.4 |  28.3$\pm$9.6 |  16.7$\pm$0.4 |  15.9$\pm$0.2 |  16.5$\pm$0.4 |  16.2$\pm$0.2 |  18.8$\pm$0.6
3967.46 |  [Ne iii] |  26.3$\pm$9.9 |  13.8$\pm$0.8 |  14.4 $\pm$ 0.4 |  17.1$\pm$0.7 |  16.3$\pm$0.4 |  21.6$\pm$0.6 |  28.8$\pm$8.2 |  15.1$\pm$0.4 |  13.6$\pm$0.3 |  13.8$\pm$0.6 |  13.1$\pm$0.3 |  12.5$\pm$0.8
3970.07 |  H i |  16.5$\pm$9.8 |  18.0$\pm$0.8 |  16.0$\pm$0.4 |  17.6$\pm$0.7 |  15.8$\pm$0.4 |  16.3$\pm$0.6 |  16.7$\pm$7.8 |  16.7$\pm$0.4 |  15.8$\pm$0.3 |  15.8$\pm$0.6 |  15.8$\pm$0.3 |  15.8$\pm$0.8
4101.74 |  H i |  27.8$\pm$8.7 |  23.7$\pm$0.6 |  25.1 $\pm$ 0.3 |  28.8$\pm$0.6 |  27.1$\pm$0.3 |  31.7$\pm$0.4 |  29.4$\pm$7.3 |  26.3$\pm$0.3 |  26.2$\pm$0.3 |  25.1$\pm$0.4 |  24.4$\pm$0.3 |  24.4$\pm$1.0
4340.47 |  H i |  55.5$\pm$8.6 |  46.5$\pm$0.5 |  45.2 $\pm$ 0.3 |  49.2$\pm$0.5 |  46.4$\pm$0.3 |  49.3$\pm$0.4 |  51.8$\pm$7.1 |  46.2$\pm$0.3 |  46.0$\pm$0.3 |  45.8$\pm$0.5 |  43.6$\pm$0.3 |  44.7$\pm$0.8
4363.21 |  [O iii] |  8.0$\pm$4.9 |  2.1$\pm$0.2 |  2.1 $\pm$ 0.1 |  2.3$\pm$0.2 |  2.3$\pm$0.1 |  2.3$\pm$0.1 |  4.7$\pm$3.4 |  2.0$\pm$0.1 |  2.0$\pm$0.1 |  2.0$\pm$0.2 |  1.9$\pm$0.1 |  1.9$\pm$0.3
4471.50 |  He i |  7.8$\pm$6.3 |  5.8$\pm$0.3 |  6.0 $\pm$ 0.2 |  6.4$\pm$0.3 |  6.1$\pm$0.2 |  5.4$\pm$0.2 |  6.3$\pm$4.2 |  6.9$\pm$0.2 |  5.6$\pm$0.1 |  5.8$\pm$0.3 |  5.5$\pm$0.2 |  5.9$\pm$0.3
4685.68 |  He ii | - | - | - |  7.7$\pm$0.4 | - | - | - | - | - |  6.1$\pm$0.4 | - | -
4711.37 |  [Ar iv] | - |  0.4$\pm$ 0.2 |  0.8 $\pm$0.2 |  0.8$\pm$0.3 |  1.0$\pm$0.1 |  0.3$\pm$0.1 | - |  0.3$\pm$0.1 |  0.8$\pm$0.1 |  0.9$\pm$0.2 |  0.6$\pm$0.1 |  0.3$\pm$0.2
4713.17 |  He i | - |  0.8 $\pm$0.2 |  0.9 $\pm$0.2 |  0.9$\pm$0.3 |  0.9$\pm$0.1 |  0.8$\pm$0.1 | - |  1.0$\pm$0.1 |  0.8$\pm$0.1 |  0.8$\pm$0.2 |  0.8$\pm$0.1 |  0.9$\pm$0.2
4740.17 |  [Ar iv] | - |  0.5 $\pm$0.2 |  1.1 $\pm$0.1 |  1.1$\pm$0.2 |  1.2$\pm$0.1 |  0.4$\pm$0.1 | - |  0.6$\pm$0.1 |  1.1$\pm$0.1 |  1.2$\pm$0.2 |  0.8$\pm$0.1 |  0.5$\pm$0.2
4861.33 |  H i | 100 | 100 | 100 | 100 | 100 | 100 | 100 | 100 | 100 | 100 | 100 | 100
4958.91 |  [O iii] |  242 $\pm$ 19 |  209 $\pm$ 5 |  233 $\pm$ 3 |  234$\pm$1 |  229$\pm$1 |  232$\pm$1 |  260$\pm$12 |  229$\pm$1 |  216$\pm$1 |  229$\pm$1 |  223$\pm$1 |  234$\pm$2
5006.84 |  [O iii] |  724 $\pm$ 62 |  613 $\pm$8 |  691 $\pm$ 4 |  697$\pm$6 |  703$\pm$4 |  741$\pm$6 |  775$\pm$70 |  685$\pm$1 |  649$\pm$1 |  688$\pm$1 |  669$\pm$1 |  702$\pm$2
5517.66 |  [Cl iii] | - |  0.62 $\pm 0.11$ |  0.49$\pm$0.05 |  0.43$\pm$0.11 |  0.51$\pm$0.06 |  0.61$\pm$0.07 | - |  0.47$\pm$0.05 |  0.39$\pm$0.03 |  0.44$\pm$0.11 |  0.43$\pm$0.05 |  0.66$\pm$0.14
5537.60 |  [Cl iii] | - |  0.81 $\pm 0.10$ |  0.69$\pm$0.07 |  0.59$\pm$0.13 |  0.71$\pm$0.06 |  0.93$\pm$0.08 | - |  0.72$\pm$0.06 |  0.55$\pm$0.04 |  0.60$\pm$0.15 |  0.64$\pm$0.06 |  0.89$\pm$0.14
5754.60 |  [N ii] |  1.31$\pm$0.58 |  1.23 $\pm 0.10$ |  0.49 $\pm$ 0.06 |  0.65$\pm$0.10 |  0.38$\pm$0.05 |  2.03$\pm$0.08 |  1.77$\pm$1.66 |  1.08$\pm$0.06 |  0.26$\pm$0.04 |  0.44$\pm$0.15 |  0.46$\pm$0.05 |  0.50$\pm$0.10
5875.66 |  He i |  15.5$\pm$2.5 |  14.2$\pm$0.2 |  18.0 $\pm$0.1 |  16.4$\pm$0.2 |  18.0$\pm$0.2 |  19.5$\pm$0.2 |  18.0$\pm$2.2 |  17.8$\pm$0.3 |  16.4$\pm$0.1 |  17.8$\pm$0.2 |  17.2$\pm$0.1 |  19.6$\pm$0.3
6300.30 |  [O i] |  7.30$\pm$1.84 |  2.44$\pm$0.11 |  0.40 $\pm$ 0.04 |  0.93$\pm$0.08 |  0.23$\pm$0.04 |  4.33$\pm$0.09 |  6.41$\pm$1.57 |  2.04$\pm$0.06 |  0.06$\pm$0.03 |  0.50$\pm$0.06 |  0.45$\pm$0.03 |  0.12$\pm$0.09
6312.10 |  [S iii] | - |  1.14$\pm$0.07 |  1.24 $\pm$ 0.07 |  1.21$\pm$0.08 |  1.16$\pm$0.07 |  2.36$\pm$0.07 |  1.38$\pm$1.08 |  1.48$\pm$0.06 |  0.87$\pm$0.04 |  1.05$\pm$0.09 |  1.11$\pm$0.05 |  0.92$\pm$0.11
6363.77 |  [O i] |  2.68$\pm$1.65 |  0.93$\pm$0.08 |  0.13 $\pm$ 0.06 |  0.34$\pm$0.09 |  0.06$\pm$0.03 |  1.57$\pm$0.08 |  1.84$\pm$1.42 |  0.70$\pm$0.04 |  0.07$\pm$0.02 |  0.17$\pm$0.11 |  0.14$\pm$0.04 | -
6548.10 |  [N ii] |  51.0 $\pm$5.1 |  27.6$\pm$0.4 |  9.8 $\pm$ 0.1 |  13.5$\pm$0.2 |  7.2$\pm$0.1 |  43.5$\pm$0.4 |  31.0$\pm$3.8 |  26.5$\pm$0.5 |  4.1$\pm$0.1 |  10.9$\pm$0.2 |  10.0$\pm$0.1 |  10.7$\pm$0.3
6562.77 |  H i |  273 $\pm$ 15 |  286 $\pm$2 |  281 $\pm$ 3 |  296$\pm$1 |  280$\pm$2 |  292$\pm$1 |  277$\pm$19 | - | - | - | - | -
6583.50 |  [N ii] |  138.0 $\pm$11.0 |  75.9$\pm$0.6 |  25.9 $\pm$ 0.2 |  35.5$\pm$0.3 |  19.6$\pm$0.2 |  121.0$\pm$1.0 |  97.2$\pm$8.0 |  73.8$\pm$1.4 |  11.8$\pm$0.1 |  27.9$\pm$0.3 |  29.2$\pm$0.2 |  27.4$\pm$0.4
6678.16 |  He i |  3.95$\pm$2.51 |  3.88$\pm$0.15 |  4.67 $\pm$ 0.08 |  4.13$\pm$0.11 |  4.85$\pm$0.11 |  5.04$\pm$0.11 |  4.88$\pm$2.91 |  4.12$\pm$0.11 |  4.41$\pm$0.06 |  4.52$\pm$0.09 |  4.55$\pm$0.08 |  4.37$\pm$0.17
6716.44 |  [S ii] |  12.30$\pm$2.30 |  4.33$\pm$0.12 |  1.34 $\pm$ 0.05 |  1.78$\pm$0.07 |  1.04$\pm$0.05 |  6.46$\pm$0.10 |  14.4$\pm$2.4 |  4.59$\pm$0.11 |  0.65$\pm$0.02 |  1.36$\pm$0.07 |  1.38$\pm$0.04 |  1.67$\pm$0.13
6730.82 |  [S ii] |  13.90$\pm$2.40 |  7.49$\pm$0.19 |  2.44 $\pm$ 0.06 |  3.31$\pm$0.09 |  1.89$\pm$0.05 |  11.42$\pm$0.16 |  15.4$\pm$2.4 |  7.99$\pm$0.18 |  1.20$\pm$0.03 |  2.56$\pm$0.09 |  2.55$\pm$0.06 |  2.96$\pm$0.15
$log~{}F(H\beta)$ | $-13.16$ | $-11.74$ | $-11.28$ | $-10.57$ | $-11.25$ | $-11.42$ | $-13.07$ | $-11.27$ | $-11.08$ | $-10.49$ | $-11.15$ | $-11.89$
$c(H\beta)$ | $0.09\pm 0.08$ | ${0.26}\pm{0.01}$ | ${0.03}\pm{0.01}$ | $0.22\pm 0.01$ | $0.02\pm 0.02$ |  0.07$\pm$0.01 |  0.08$\pm$0.08 |  0.11$\pm$0.03 |  0.03$\pm$0.01 |  0.06$\pm$0.01 |  0.20$\pm$0.03 |  0.14$\pm$0.08
Electron densities (cm-3) and temperatures (K)
Ne[S ii] | $951\pm 242$ | $4280\pm 161$ | $5390\pm 241$ | $5740\pm 274$ | $5240\pm 286$ |  4660$\pm$97 |  926$\pm$211 |  4310$\pm$142 |  5580$\pm$221 |  5870$\pm$366 |  5620$\pm$210 |  4700$\pm$437
Ne[Cl iii] | - | $3840\pm 1154$ | $4630\pm 666$ | $4260\pm 1438$ | $4340\pm 629$ |  5510$\pm$790 | - |  5520$\pm$746 |  4720$\pm$500 |  4070$\pm$1439 |  5230$\pm$781 |  4200$\pm$1109
Ne[Ar iv] | - | $6300\pm 4034$ | $6730\pm 1790$ | $6050\pm 2521$ | $5960\pm 706$ |  $5500\pm$2292 | - |  $10300\pm$3839 | $6980\pm 1079$ |  $5960\pm$1656 |  $7380\pm$1538 | $7280\pm 5660$
Te[N ii] | $8340\pm 3731$ | $9820\pm 801$ | $10200\pm 1251$ | $10200\pm 1459$ | $10600\pm 1378$ |  9930$\pm$397 | $11600\pm 10908$ |  9460$\pm$544 |  11000$\pm$1695 |  9350$\pm$3189 |  9680$\pm$1054 |  10100$\pm$2024
Te[O iii] | ${12100}\pm 7487$ | $8300\pm 796$ |  ${8140}\pm$390 | $8310\pm 724$ | $8360\pm 368$ |  8320$\pm$365 |  10000$\pm$7167 |  8010$\pm$401 |  8180$\pm$409 |  8020$\pm$802 |  8020$\pm$422 |  7820$\pm$1235
|  |  Stellar line fluxes from CSPN (erg/s/cm2) | FWHM (Å) |  |  Stellar line fluxes form CSPN (erg/s/cm2) | FWHM (Å)
C iv $\lambda$5801 |  |  |  (1.68$\pm$0.07)$\times 10^{-12}$ |  14$\pm$1 |  |  (1.96$\pm$0.07)$\times 10^{-12}$ |  13$\pm$1
C iv $\lambda$5812 |  |  |  (8.61$\pm$0.60)$\times 10^{-13}$ |  14$\pm$1 |  |  (9.07$\pm$0.60)$\times 10^{-13}$ |  13$\pm$1
(12)In this PA the [O iii]$\lambda$5007 Å emission line was saturated, then it
was estimated using the theoretical line ratio I(5007)/I(4959)=3.01$\pm$0.23
from Acker et al. (1989).

Table A10: Ionic and total abundances of NGC 6543.

| PA=5 |  PA=163(13)
---|---|---
Abundances | J | D | A | Neb | A’ | D’ | J’ | D | A | Neb | A’ | D’
10${}^{2}\times$ He+/H | $11.5\pm 2.8$ | ${9.8}\pm 0.2$ | $11.8\pm 0.1$ |  11.1$\pm$0.2 |  11.9$\pm$0.01 |  12.3$\pm$0.2 |  12.4$\pm$2.4 |  11.7$\pm$0.2 |  10.9$\pm$0.1 |  11.6$\pm$0.2 |  11.2$\pm$0.1 |  12.2$\pm$0.2
10${}^{2}\times$ He2+/H | - | - | - |  0.60$\pm$0.03 | - | - | - | - | - |  0.48$\pm$0.03 | - | -
10${}^{2}\times$ He/H | $11.5\pm 2.8$ | $9.8\pm 0.2$ | $11.8\pm 0.1$ |  11.7$\pm$0.2 |  11.9$\pm$0.01 |  12.3$\pm$0.2 |  12.4$\pm$2.4 |  11.7$\pm$0.2 |  10.9$\pm$0.1 |  12.1$\pm$0.2 |  11.2$\pm$0.1 |  12.2$\pm$0.2
10${}^{5}\times$ N+/H | $4.81\pm 1.62$ | $1.73\pm 0.16$ | $0.55\pm 0.07$ |  0.77$\pm$0.11 |  0.39$\pm$0.06 |  2.69$\pm$0.12 |  1.50$\pm$0.73 |  1.86$\pm$0.10 |  0.20$\pm$0.01 |  0.75$\pm$0.20 |  0.69$\pm$0.08 |  0.60$\pm$0.17
icf(N) | $5.7\pm 3.4$ | $33.7\pm 7.3$ | $77.6\pm 28.9$ |  22.5$\pm$6.0 |  78.0$\pm$19.8 |  10.9$\pm$1.2 |  32.2$\pm$10.2 |  18.6$\pm$8.7 |  76.6$\pm$28.5 |  32.4$\pm$16.1 |  48.2$\pm$11.0 |  33.1$\pm$17.0
10${}^{5}\times$ N/H | $28.0\pm 11.6$ | $58.3\pm 8.8$ | $41.3\pm 10.3$ |  17.5$\pm$2.7 |  30.2$\pm$4.9 |  29.1$\pm$2.3 |  54.8$\pm$28.0 |  34.6$\pm$2.7 |  15.6$\pm$2.5 |  23.7$\pm$7.4 |  33.4$\pm$3.9 |  19.7$\pm$5.8
10${}^{6}\times$ O0/H | $26.6\pm 12.2$ | ${5.0}\pm 0.6$ | $0.7\pm 0.2$ |  1.7$\pm$0.5 |  0.3$\pm$0.1 |  8.3$\pm$0.5 |  7.4$\pm$4.6 |  4.6$\pm$0.4 |  0.2$\pm$0.1 |  1.1$\pm$0.9 |  0.9$\pm$0.2 |  0.2$\pm$0.1
10${}^{5}\times$ O+/H | $10.3\pm 5.2$ | $5.3\pm 0.9$ | $1.4\pm 0.4$ |  2.5$\pm$0.9 |  1.3$\pm$0.4 |  5.0$\pm$0.4 |  2.9$\pm$1.9 |  3.1$\pm$0.3 |  0.6$\pm$0.2 |  2.1$\pm$0.9 |  1.9$\pm$0.4 |  1.9$\pm$0.6
10${}^{4}\times$ O2+/H | $1.4\pm 0.6$ | ${4.2}\pm 0.5$ | $5.1\pm 0.3$ |  4.8$\pm$0.5 |  4.8$\pm$0.2 |  4.9$\pm$0.3 |  2.6$\pm$1.2 |  5.5$\pm$0.3 |  4.7$\pm$0.2 |  5.4$\pm$0.6 |  5.3$\pm$0.2 |  6.2$\pm$1.1
icf(O) | $1.00\pm 0.00$ | $1.00\pm 0.00$ | $1.00\pm 0.00$ |  1.03$\pm$0.01 |  1.00$\pm$0.00 |  1.00$\pm$0.00 |  1.00$\pm$0.00 |  1.00$\pm$0.00 |  1.00$\pm$0.01 |  1.02$\pm$0.01 |  1.00$\pm$0.01 |  1.00$\pm$0.00
10${}^{4}\times$ O/H | $2.9\pm 1.2$ | ${4.7}\pm 0.5$ | $5.3\pm 0.3$ |  5.2$\pm$0.6 |  4.9$\pm$0.2 |  5.5$\pm$0.3 |  3.2$\pm$1.4 |  5.8$\pm$0.3 |  4.8$\pm$0.2 |  5.8$\pm$0.7 |  5.5$\pm$0.2 |  6.4$\pm$1.2
10${}^{5}\times$ Ne2+/H | $3.9\pm 1.8$ | ${12.6}\pm 1.2$ | $13.1\pm 0.8$ |  13.9$\pm$1.8 |  12.8$\pm$0.7 |  15.2$\pm$1.1 |  8.3$\pm$4.0 |  15.0$\pm$0.9 |  12.7$\pm$0.6 |  14.2$\pm$1.8 |  13.5$\pm$0.8 |  14.6$\pm$2.4
icf(Ne) | $3.54\pm 1.44$ | $1.76\pm 0.09$ | $1.39\pm 0.03$ |  1.03$\pm$0.01 |  1.11$\pm$0.07 |  1.67$\pm$0.04 |  1.77$\pm$0.69 |  1.50$\pm$0.02 |  1.10$\pm$0.01 |  1.03$\pm$0.01 |  1.13$\pm$0.01 |  1.40$\pm$0.08
10${}^{5}\times$ Ne/H | $16.3\pm 7.5$ | $22.3\pm 2.2$ | $18.2\pm 1.1$ |  14.3$\pm$1.9 |  14.3$\pm$0.7 |  25.5$\pm$1.6 |  16.4$\pm$8.3 |  22.6$\pm$1.2 |  13.9$\pm$0.8 |  14.6$\pm$1.8 |  15.2$\pm$0.8 |  20.7$\pm$4.6
10${}^{7}\times$ Ar3+/H | - | $2.7\pm 0.8$ | $6.4\pm 0.7$ |  5.7$\pm$1.2 |  6.6$\pm$0.5 |  2.0$\pm$0.5 | - |  3.2$\pm$0.4 |  6.3$\pm$0.4 |  7.0$\pm$1.4 |  4.7$\pm$0.4 |  3.1$\pm$1.1
icf(Ar)(14) | $1.00\pm 0.00$ | $1.11\pm 0.24$ | $1.03\pm 0.01$ |  1.09$\pm$0.02 |  1.03$\pm$0.01 |  1.09$\pm$0.01 |  1.00$\pm$0.00 |  1.05$\pm$0.01 |  1.01$\pm$0.01 |  1.07$\pm$0.05 |  1.04$\pm$0.01 |  1.03$\pm$0.02
10${}^{7}\times$ Ar/H | - | $3.0\pm 0.9$ | $6.6\pm 0.7$ |  6.2$\pm$1.1 |  6.8$\pm$0.5 |  2.2$\pm$0.5 | - |  3.4$\pm$0.4 |  6.3$\pm$0.4 |  7.6$\pm$1.6 |  4.9$\pm$0.4 |  3.3$\pm$1.3
10${}^{7}\times$ S+/H | $11.0\pm 3.8$ | ${4.4}\pm 0.4$ | $1.4\pm 0.2$ |  2.0$\pm$0.5 |  1.0$\pm$0.2 |  6.7$\pm$0.4 |  6.0$\pm$2.8 |  5.2$\pm$0.3 |  0.6$\pm$0.1 |  1.9$\pm$0.9 |  1.7$\pm$0.2 |  1.7$\pm$0.6
10${}^{6}\times$ S+2/H |  6.4$\pm$4.2 |  6.8$\pm$0.8 |  8.3$\pm$0.7 |  7.2$\pm$0.9 |  7.0$\pm$0.6 |  14.0$\pm$0.9 |  3.0$\pm$2.5 |  10.8$\pm$0.8 |  5.7$\pm$0.4 |  7.6$\pm$1.1 |  8.1$\pm$0.5 |  7.5$\pm$1.5
icf (S)(14) |  1.1$\pm$0.7 |  1.5$\pm$0.3 |  2.3$\pm$0.7 |  1.9$\pm$0.7 |  2.3$\pm$0.7 |  1.6$\pm$0.2 |  1.6$\pm$1.3 |  1.9$\pm$0.2 |  3.0$\pm$1.0 |  2.1$\pm$0.9 |  2.2$\pm$0.5 |  2.3 $\pm$0.8
10${}^{6}\times$ S/H |  8.2$\pm$5.2 |  10.9$\pm$2.2 |  19.4$\pm$5.9 |  14.1$\pm$5.2 |  16.3$\pm$5.0 |  23.5$\pm$2.9 |  5.8$\pm$4.7 |  21.5$\pm$2.3 |  17.3$\pm$5.8 |  16.4$\pm$7.0 |  18.2$\pm$4.1 |  17.6$\pm$6.1
10${}^{8}\times$ Cl2+/H | - | $17.9\pm 2.8$ | $16.0\pm 1.7$ |  12.9$\pm$2.7 |  14.9$\pm$1.3 |  19.3$\pm$4.3 | - |  17.9$\pm$2.6 |  12.4$\pm$1.0 |  14.9$\pm$3.7 |  15.3$\pm$1.5 |  25.0$\pm$12.9
icf(Cl) | $1.00\pm 0.00$ | $1.62\pm 0.06$ | $1.00\pm 0.00$ |  1.00$\pm$0.09 |  1.00$\pm$0.00 |  1.69$\pm$0.04 |  1.00$\pm$0.00 |  1.88$\pm$0.04 |  1.00$\pm$0.00 |  1.00$\pm$0.81 |  1.00$\pm$0.00 |  1.00$\pm$0.00
10${}^{8}\times$ Cl/H | - | $29.1\pm 4.9$ | $16.0\pm 1.7$ |  17.7$\pm$5.8 |  14.9$\pm$1.3 |  32.5$\pm$7.6 | - |  32.0$\pm$4.8 |  12.4$\pm$1.0 |  17.7$\pm$5.3 |  15.3$\pm$1.7 |  25.0$\pm$12.9
(13)In this PA, abundance estimation may not be reliable. |  |
(14)Calculated using Kingsburgh & Barlow (1994). When no S+2 is present, it was calculated using $S^{+2}=S^{+}[4.677+(O^{+2}/O^{+})^{0.433}]$ from the same work. |  |

Table A11: NGC 6905.

|  | PA=161
---|---|---
Line | Ion | South Rim | Neb | North Rim | NW knot 2 | NW knot
|  | 6px-4.2” | 60px-42” | 8px - 5.6” | 6px-4.2” | 8px-5.6”
3727.00 |  [O ii]b |  11.6$\pm$2.5 |  19.6$\pm$3.8 |  30.0$\pm$3.1 |  54.4$\pm$8.3 |  214$\pm$27
3868.75 |  [Ne iii] |  71.5$\pm$3.2 |  94.9$\pm$3.2 |  102.0$\pm$3.0 |  112.0$\pm$7.0 |  134.0$\pm$14.0
3889.05 |  H i+He i |  12.3$\pm$1.5 |  29.3$\pm$3.2 |  14.7$\pm$1.3 |  16.2$\pm$3.6 |  21.2$\pm$6.8
3967.46 |  [Ne iii] |  23.0$\pm$2.0 |  23.1$\pm$3.3 |  33.4$\pm$2.4 |  38.7$\pm$5.1 |  41.3$\pm$8.3
3970.07 |  H i |  16.0$\pm$1.9 |  15.8$\pm$3.4 |  15.9$\pm$2.4 |  16.2$\pm$5.1 |  16.9$\pm$8.2
4101.74 |  H i |  28.5$\pm$1.6 |  27.4$\pm$1.9 |  26.9$\pm$0.9 |  28.9$\pm$4.4 |  29.7$\pm$8.7