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Start Over Subject chemical abundances Subject galaxies Subject h ii regions Rights public
1. Abundance gradients in low SB spirals
ID:
ivo://CDS.VizieR/J/MNRAS/454/3664
Title:
Abundance gradients in low SB spirals
Short Name:
J/MNRAS/454/3664
Date:
21 Oct 2021
Publisher:
CDS
Description:
We acquired spectra of 141 HII regions in 10 late-type low surface brightness galaxies (LSBGs). The analysis of the chemical abundances obtained from the nebular emission lines shows that metallicity gradients are a common feature of LSBGs, contrary to previous claims concerning the absence of such gradients in this class of galaxies. The average slope, when expressed in units of the isophotal radius, is found to be significantly shallower in comparison to galaxies of high surface brightness. This result can be attributed to the reduced surface brightness range measured across their discs, when combined with a universal surface mass density-metallicity relation. With a similar argument we explain the common abundance gradient observed in high surface brightness galaxy (HSBG) discs and its approximate dispersion. This conclusion is reinforced by our result that LSBGs share the same common abundance gradient with HSBGs, when the slope is expressed in terms of the exponential disc scalelength.
2. Abundances in blue compact galaxies
ID:
ivo://CDS.VizieR/J/ApJ/511/639
Title:
Abundances in blue compact galaxies
Short Name:
J/ApJ/511/639
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present high-quality ground-based spectroscopic observations of 54 supergiant H II regions in 50 low-metallicity blue compact galaxies with oxygen abundances 12+Log[O/H] between 7.1 and 8.3. We use the data to determine abundances for the elements N, O, Ne, S, Ar, and Fe. We also analyze Hubble Space Telescope (HST) Faint Object Spectrograph archival spectra of 10 supergiant H II regions to derive C and Si abundances in a subsample of seven blue compact galaxies. The main result of the present study is that none of the heavy element-to-oxygen abundance ratios studied here (C/O, N/O, Ne/O, Si/O, S/O, Ar/O, Fe/O) depend on oxygen abundance for blue compact galaxies with 12+Log[O/H]{<=}7.6 (Z{<=}Z_{solar}/20).
3. Abundances in HII regions and PNe of M81
ID:
ivo://CDS.VizieR/J/A+A/521/A3
Title:
Abundances in HII regions and PNe of M81
Short Name:
J/A+A/521/A3
Date:
21 Oct 2021
Publisher:
CDS
Description:
M81 is an ideal laboratory to investigate the galactic chemical and dynamical evolution through the study of its young and old stellar populations. We analyze the chemical abundances of planetary nebulae and HII regions in the M81 disk for insight on galactic evolution, and compare it with that of other galaxies, including the Milky Way.
4. Abundances in HII regions of M81
ID:
ivo://CDS.VizieR/J/A+A/567/A88
Title:
Abundances in HII regions of M81
Short Name:
J/A+A/567/A88
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present a new set of weak-line abundances of HII regions in M81, based on Gemini Multi-Object Spectrograph (GMOS) observations. The aim is to derive plasma and abundance analysis for a sizable set of emission-line targets to study the galactic chemical contents in the framework of galactic metallicity gradients. We used the weak-line abundance approach by deriving electron density and temperatures for several HII regions in M81. Gradient analysis is based on oxygen abundances. Together with a set of HII region abundances determined similarly by us with Multi-Mirror Telescope (MMT) spectra, the new data yield to a radial oxygen gradient of -0.088+/-0.013dex/kpc, which is steeper than the metallicity gradient obtained for planetary nebulae (-0.044+/-0.007dex/kpc). This result could be interpreted as gradient evolution with time: Models of galactic evolution with inside-out disk formation associated to pre-enriched gas infall would produce such difference of gradients, although stellar migration effects would also induce a difference in the metallicity gradients between the old and young populations.
5. Abundances in M33 HII regions
ID:
ivo://CDS.VizieR/J/ApJ/675/1213
Title:
Abundances in M33 HII regions
Short Name:
J/ApJ/675/1213
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present a new determination of the metallicity gradient in M33, based on Keck LRIS measurements of oxygen abundances using the temperature-sensitive emission line [OIII] {lambda}4363 in 61 HII regions. These data approximately triple the sample of direct oxygen abundances in M33. We find a central abundance of 12+log(O/H)=8.36+/-0.04 and a slope of -0.027+/-0.012dex/kpc, in agreement with infrared measurements of the neon abundance gradient but much shallower than most previous oxygen gradient measurements. There is substantial intrinsic scatter of 0.11dex in the metallicity at any given radius in M33, which imposes a fundamental limit on the accuracy of gradient measurements that rely on small samples of objects. We also show that the ionization state of neon does not follow the ionization state of oxygen as is commonly assumed, suggesting that neon abundance measurements from optical emission lines require careful treatment of the ionization corrections.
6. Abundances of emission galaxies in SDSS-DR3
ID:
ivo://CDS.VizieR/J/A+A/448/955
Title:
Abundances of emission galaxies in SDSS-DR3
Short Name:
J/A+A/448/955
Date:
21 Oct 2021
Publisher:
CDS
Description:
We have re-evaluated empirical expressions for the abundance determination of N, O, Ne, S, Cl, Ar and Fe taking into account the latest atomic data and constructing an appropriate grid of photoionization models with state-of-the art model atmospheres. Using these expressions we have derived heavy element abundances in the ~310 emission-line galaxies from the Data Release 3 of the Sloan Digital Sky Survey (SDSS, <III/241>) with an observed Hbeta flux F(Hbeta)>10^-14^erg/s/cm^2^ and for which the [O III] 4363 emission line was detected at least at a 2sigma level, allowing abundance determination by direct methods. The oxygen abundance 12+logO/H of the SDSS galaxies lies in the range from ~7.1 (Z_{sun}_/30) to ~8.5 (0.7Z_{sun}_). The SDSS sample is merged with a sample of 109 blue compact dwarf (BCD) galaxies with high quality spectra, which contains extremely low-metallicity objects. We use the merged sample to study the abundance patterns of low-metallicity emission-line galaxies. We find that extremely metal-poor galaxies (12+logO/H<7.6, i.e. Z<Z_{sun}_/12) are rare in the SDSS sample. The alpha element to oxygen abundance ratios do not show any significant trends with oxygen abundance, in agreement with previous studies, except for a slight increase of Ne/O with increasing metallicity, which we interpret as due to a moderate depletion of O onto grains in the most metal-rich galaxies. The Fe/O abundance ratio is smaller than the solar value, by up to 1 dex at the high metallicity end. We also find that Fe/O increases with decreasing Hbeta equivalent width EW(Hbeta). We interpret this as a sign of strong depletion onto dust grains, and gradual destruction of those grains on a time scale of a few Myr. All the galaxies are found to have logN/O>-1.6, implying that they have a different nature than the subsample of high-redshift damped Lyalpha systems with log N/O of ~-2.3 and that their ages are larger than 100-300Myr. We confirm the apparent increase in N/O with decreasing EW(Hbeta), already shown in previous studies, and explain it as the signature of gradual nitrogen ejection by massive stars from the most recent starburst.
7. Abundances of HII regions in blue galaxies
ID:
ivo://CDS.VizieR/J/AZh/79/867
Title:
Abundances of HII regions in blue galaxies
Short Name:
J/AZh/79/867
Date:
21 Oct 2021
Publisher:
CDS
Description:
New expression for the ionization correction factors (ICF) are used to find the nebular-gas compositions in HII regions in blue compact dwarf galaxies (BCD). The abundances of He, N, O, Ne, S, and Ar in 41 HII regions are determined.
8. Abundances of M33 HII regions
ID:
ivo://CDS.VizieR/J/A+A/512/A63
Title:
Abundances of M33 HII regions
Short Name:
J/A+A/512/A63
Date:
21 Oct 2021
Publisher:
CDS
Description:
We analyze the spatial distribution of metals in M33 using a new sample and literature data of HII regions, constraining a model of galactic chemical evolution with HII region and planetary nebula (PN) abundances. We consider chemical abundances of a new sample of HII regions complemented with previous literature data-sets. Supported by a uniform sample of nebular spectroscopic observations, we conclude that: i) the metallicity distribution in M33 is very complex, showing a central depression in metallicity probably due to observational bias; ii) the metallicity gradient in the disk of M33 has a slope of -0.037+/-0.009dex/kpc in the whole radial range up to ~8kpc, and -0.044+/-0.009dex/kpc excluding the central kpc; iii) there is a small evolution of the slope with time from the epoch of PN progenitor formation to the present-time. Description: Emission line fluxes, observed and dereddened of 33 HII regions are presented. Physical and chemical properties, such as electron temperatures and density, ionic and total chemical abundances of He, O, N, Ne, Ar, S, are derived.
9. Abundances of nearby late-type galaxies. I. Data
ID:
ivo://CDS.VizieR/J/AJ/147/131
Title:
Abundances of nearby late-type galaxies. I. Data
Short Name:
J/AJ/147/131
Date:
21 Oct 2021
Publisher:
CDS
Description:
We investigate the oxygen and nitrogen abundance distributions across the optical disks of 130 nearby late-type galaxies using around 3740 published spectra of HII regions. We use these data in order to provide homogeneous abundance determinations for all objects in the sample, including HII regions in which not all of the usual diagnostic lines were measured. Examining the relation between N and O abundances in these galaxies we find that the abundances in their centers and at their isophotal R_25_ disk radii follow the same relation. The variation in N/H at a given O/H is around 0.3dex. We suggest that the observed spread in N/H may be partly caused by the time delay between N and O enrichment and the different star formation histories in galaxies of different morphological types and dimensions. We study the correlations between the abundance properties (central O and N abundances, radial O and N gradients) of a galaxy and its morphological type and dimension.
10. Abundances of PNe in NGC 300
ID:
ivo://CDS.VizieR/J/A+A/552/A12
Title:
Abundances of PNe in NGC 300
Short Name:
J/A+A/552/A12
Date:
21 Oct 2021
Publisher:
CDS
Description:
We have obtained deep spectroscopy of 26 planetary nebulae (PNe) and 9 compact HII regions in the nearby spiral galaxy NGC 300, and analyzed them together with the giant HII regions observed by Bresolin et al. (2009ApJ...700..309B). We have determined the physical properties of all those objects and their content in He, N, O, Ne, S and Ar in a consistent way. We find that compact HII regions have abundances similar to those of giant HII regions, while PNe have systematically larger N/O ratios and similar Ne/O and Ar/O ratios. We demonstrate that this nitrogen enhancement in PNe cannot be due to second dredge-up in the progenitor stars, since their initial masses are around 2-2.5M_{sun}_. An extra mixing process is required, perhaps be driven by rotation. Concerning the radial abundance distribution, PNe behave differently from HII regions: In the central parts, they show an average O/H smaller by 0.15dex. Their abundance dispersion at any galactocentric radius is significantly larger than for HII regions and many of them have O/H values higher than HII regions at the same galactocentric distance, suggesting that oxygen production in the PN progenitors in NGC 300 is common. PN abundance gradients in O/H, Ne/H and Ar/He are significantly shallower than those of HII regions. We argue that this indicates a steepening of the metallicity gradient in NGC 300 during the last Gr, rather than the effect of radial stellar motions.

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