J/MNRAS/495/1016 Spectra quality impact on nebular abundances (Rodriguez, 2020)
The impact of spectra quality on nebular abundances.
Rodriguez M.
<Mon. Not. R. Astron. Soc., 495, 1016-1034 (2020)>
=2020MNRAS.495.1016R 2020MNRAS.495.1016R (SIMBAD/NED BibCode)
ADC_Keywords: Planetary nebulae ; Milky Way ; Abundances, peculiar ;
Spectra, optical
Keywords: ISM: abundances - planetary nebulae: general
Abstract:
I explore the effects of observational errors on nebular chemical
abundances using a sample of 179 optical spectra of 42 planetary
nebulae (PNe) observed by different authors. The spectra are analysed
in a homogeneous way to derive physical conditions and ionic and total
abundances. The effects of recombination on the [OII] and [NII]
emission lines are estimated by including the effective recombination
coefficients in the statistical equilibrium equations that are solved
for O+ and N+. The results are shown to be significantly different
than those derived using previous approaches. The O+ abundances
derived with the blue and red lines of [OII] differ by up to a factor
of 6, indicating that the relative intensities of lines widely
separated in wavelength can be highly uncertain. In fact, the HeII
lines in the range 4000-6800Å imply that most of the spectra are
bluer than expected. Scores are assigned to the spectra using
different criteria and the spectrum with the highest score for each PN
is taken as the reference spectrum. The differences between the
abundances derived with the reference spectrum and those derived with
the other spectra available for each object are used to estimate the
1σ observational uncertainties in the final abundances: 0.11dex
for O/H and Ar/H, 0.14dex for N/H, Ne/H, and Cl/H, and 0.16dex for
S/H.
Description:
The sample consists of 179 optical spectra of 42 PNe, each of them
with 3-7 spectra. The spectra were compiled from the literature by
looking for PNe that have three or more available spectra that
contain: at least one working density diagnostic (from among
[SII]λ6716/λ6731, [OII]λ3726/λ3729,
[ClIII]λ5518/λ5538, and
[ArIV]λ4711/λ4740), the two most used temperature
diagnostics ([OIII]λ4363/(λ4959+λ5007) and
[NII]λ5755/(λ6548+λ6583)), and the
[OII]λ3727 lines.
The [OII] lines are required for the calculation of the total
abundances not only of oxygen, but of most of the other elements
through the use of ionization correction factors (see, e.g.
Delgado-Inglada, Morisset & Stasinska 2014MNRAS.440..536D 2014MNRAS.440..536D). The O+
abundance can be calculated using either the [OII]λ3727 lines
or the [OII]λ7325 lines. The red [OII] lines are weaker than
their blue counterparts and can be severely contaminated by telluric
emission lines. The blue [OII] lines are not without problems, since
they lie in a spectral region where instruments can have a low
efficiency and the effects of atmospheric differential refraction
might be important (Filippenko 1982PASP...94..715F 1982PASP...94..715F), but they seem a
safer bet.
The sample objects are Galactic PNe, although the halo PN BoBn 1 might
be located in the Sagittarius dwarf spheroidal galaxy (Zijlstra et al.
2006MNRAS.369..875Z 2006MNRAS.369..875Z). These objects and the spectra used for their
analysis are listed in Tables B1-B5.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
tableb1.dat 63 179 Physical conditions of the sample PNe
tableb2.dat 66 179 Ionic abundances derived from collisionally
excited lines
tableb3.dat 75 179 Ionic and total abundances of helium
tableb4.dat 81 179 Total abundances
tableb5.dat 64 179 Partial and final scores for the sample spectra
refs.dat 82 69 References for tables B1-B5
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Byte-by-byte Description of file: tableb1.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 7 A7 --- Name Planetary nebula name
9- 15 A7 --- Ref Reference
17- 18 A2 --- f_Ref Flag on Ref (G1)
20- 24 I5 cm-3 ne[SII] ? Electron density derived from the
[SII]λ6716/λ6731 diagnosis
26- 30 I5 cm-3 ne[OII] ? Electron density derived from the
[OII]λ3726/λ3729 diagnosis
32- 36 I5 cm-3 ne[ClIII] ? Electron density derived from the
[ClIII]λ5518/λ5538 diagnosis
38- 42 I5 cm-3 ne[ArIV] ? Electron density derived from the
[ArIV]λ4711/λ4740 diagnosis
44- 48 I5 cm-3 ne Geometric mean of the electron density (1)
50- 54 I5 K Te[NII] Electron temperature obtained from the
diagnostics [NII]λ5755/
(λ6548+λ6583)
56- 60 I5 K Te[OIII] Electron temperature obtained from the
diagnostics [OIII]λ4363/
(λ4959+λ5007)
62- 63 I2 --- ptot Final score of the spectrum (see Section 6.9)
--------------------------------------------------------------------------------
Note (1): The geometric mean, i.e. the average of the logarithmic values, is
used because it is more robust to the large variations in ne
introduced by observational or atomic-data uncertainties when the
diagnostics are near the limits of their validity.
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Byte-by-byte Description of file: tableb2.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 7 A7 --- Name Planetary nebula name
9- 15 A7 --- Ref Reference
17- 18 A2 --- f_Ref Flag on Ref (G1)
20- 23 F4.2 --- O+(b) 12+log(O+/H+) abundance calculated using the
blue [OII] lines
25- 28 F4.2 --- O+(r) ? 12+log(O+/H+) abundance calculated using
the red [OII] lines
30- 33 F4.2 --- O++ 12+log(O++/H+) abundance
35- 38 F4.2 --- N+ 12+log(N+/H+) abundance
40- 43 F4.2 --- Ne++ ? 12+log(Ne++/H+) abundance
45- 48 F4.2 --- S+ 12+log(S+/H+) abundance
50- 53 F4.2 --- S++ ? 12+log(S++/H+) abundance
55- 58 F4.2 --- Ar++ ? 12+log(Ar++/H+) abundance
60- 63 F4.2 --- Cl++ ? 12+log(Cl++/H+) abundance
65- 66 I2 --- ptot Final score of the spectrum (see Section 6.9)
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Byte-by-byte Description of file: tableb3.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 7 A7 --- Name Planetary nebula name
9- 15 A7 --- Ref Reference
17- 18 A2 --- f_Ref Flag on Ref (G1)
20- 24 F5.2 --- He+4026 ? 12+log(He+/H) abundance derived from the
λ4026 line
26- 30 F5.2 --- He+4388 ? 12+log(He+/H) abundance derived from the
λ4388 line
32- 36 F5.2 --- He+4922 ? 12+log(He+/H) abundance derived from the
λ4922 line
38- 42 F5.2 --- He+4471 ? 12+log(He+/H) abundance derived from the
λ4471 line
44- 48 F5.2 --- He+5876 12+log(He+/H) abundance derived from the
λ5876 line
50- 54 F5.2 --- He+6678 ? 12+log(He+/H) abundance derived from the
λ6678 line
56- 60 F5.2 --- He+ 12+log(He+/H) abundance
62- 66 F5.2 --- He++ ? 12+log(He++/H) abundance
68- 72 F5.2 --- He 12+log(He/H) abundance
74- 75 I2 --- ptot Final score of the spectrum (see Section 6.9)
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Byte-by-byte Description of file: tableb4.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 7 A7 --- Name Planetary nebula name
9- 15 A7 --- Ref Reference
17- 18 A2 --- f_Ref Flag on Ref (G1)
20- 23 F4.2 --- O(b) 12+log(O/H) abundance calculated using the blue
[OII] lines
25- 28 F4.2 --- N(b) 12+log(N/H) abundance calculated using the blue
[OII] lines
30- 33 F4.2 --- Ne(b) ? 12+log(Ne/H) abundance calculated using the
blue [OII] lines
35- 38 F4.2 --- S(b) ? 12+log(S/H) abundance calculated using the
blue [OII] lines
40- 43 F4.2 --- Ar(b) ? 12+log(Ar/H) abundance calculated using the
blue [OII] lines
45- 48 F4.2 --- Cl(b) ? 12+log(Cl/H) abundance calculated using the
blue [OII] lines
50- 53 F4.2 --- O(r) ? 12+log(O/H) abundance calculated using the red
[OII] lines
55- 58 F4.2 --- N(r) ? 12+log(N/H) abundance calculated using the red
[OII] lines
60- 63 F4.2 --- Ne(r) ? 12+log(Ne/H) abundance calculated using the
red [OII] lines
65- 68 F4.2 --- S(r) ? 12+log(S/H) abundance calculated using the red
[OII] lines
70- 73 F4.2 --- Ar(r) ? 12+log(Ar/H) abundance calculated using the
red [OII] lines
75- 78 F4.2 --- Cl(r) ? 12+log(Cl/H) abundance calculated using the
red [OII] lines
80- 81 I2 --- ptot Final score of the spectrum (see Section 6.9)
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Byte-by-byte Description of file: tableb5.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 7 A7 --- Name Planetary nebula name
9- 15 A7 --- Ref Reference
17- 18 A2 --- f_Ref Flag on Ref (G1)
20- 21 I2 --- p0 [0/10] Score indicating whether the spectra was
obtained with a CCD (p0=10) or not (p0=0)
23- 24 I2 --- p1 [20] Score related to the available temperature
diagnostics
26 I1 --- N Number of density diagnostics
28- 29 I2 --- p2 Score related to the density diagnosis
(p2=9-15 for 1-4 working density diagnostics)
31- 34 F4.2 --- [NII] ? [NII] λ6584/λ6548 line ratio
36- 37 I2 --- p3 [0/10] Score associated to [NII]
39- 42 F4.2 --- [OIII] ? [OIII] λ5007/λ4959 line ratio
44- 45 I2 --- p4 [0/10] Score associated to [OIII]
47 I1 --- NHeI Number of HeI lines unaffected by optical depth
effects available in the spectra
49- 50 I2 --- p5 [2/20] Score assigned to NHeI (1)
52 I1 --- NBL Number of balmer lines (out of Hα,
Hγ and Hδ) whose intensities are
listed in the spectra
54- 58 F5.2 --- P-B ? Difference between the median deviations of
the Paschen and Balmer lines from their
expected values (see Section 6.7)
60- 61 I2 --- p6 [0/15] Score assigned using the behaviour of
all these lines
63- 64 I2 --- ptot Final score of the spectrum (obtained from the
addition of the previous scores)
--------------------------------------------------------------------------------
Note (1): Score assigned according to how consistent are the He+ abundances
implied by them (p5=2-20, where 2 is the score when only one HeI line
is available)
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Byte-by-byte Description of file: refs.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 7 A7 --- Ref Reference
9- 27 A19 --- BibCode BibCode
29- 61 A33 --- Aut Author's name
63- 82 A20 --- Com Comments
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Global Notes:
Note (G1): Flag as follows:
* = Spectra used as reference for the object
a = O/H, N/H, and S/H are within 0.1dex of the reference spectrum for
calculations based on the blue [OII] lines
b = O/H, N/H, and S/H are within 0.1dex of the reference spectrum for
calculations based on the red [OII] lines
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History:
From electronic version of the journal
(End) Ana Fiallos [CDS] 08-Jun-2023