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371. Chemical abundances in Galactic PNe
ID:
ivo://CDS.VizieR/J/A+A/567/A12
Title:
Chemical abundances in Galactic PNe
Short Name:
J/A+A/567/A12
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present new low-resolution (R~800) optical spectra of 22 Galactic PNe with Spitzer spectra. These data are combined with recent optical spectroscopic data available in the literature to construct representative samples of compact (and presumably young) Galactic disc and bulge PNe with Spitzer spectra. Attending to the nature of the dust features seen in their Spitzer spectra, Galactic disc and bulge PNe are classified according to four major dust types (oxygen chemistry or OC, carbon chemistry or CC, double chemistry or DC, featureless or F) and subtypes (amorphous and crystalline, and aliphatic and aromatic). Nebular gas abundances of He, N, O, Ne, S, Cl, and Ar, as well as plasma parameters (e.g. Ne, Te) are homogeneously derived and we study the median chemical abundances and nebular properties in Galactic disc and bulge PNe depending on their Spitzer dust types and subtypes. A comparison of the derived median abundance patterns with AGB nucleosynthesis predictions show mainly that i) DC PNe, both with amorphous and crystalline silicates, display high-metallicity (solar/supra-solar) and the highest He abundances and N/O ratios, suggesting relatively massive (~3-5M_{sun}_) hot bottom burning AGB stars as progenitors; ii) PNe with O-rich and C-rich unevolved dust (amorphous and aliphatic) seem to evolve from subsolar metallicity (z~0.008) and lower mass (<3M_{sun}_) AGB stars; iii) a few O-rich PNe and a significant fraction of C-rich PNe with more evolved dust (crystalline and aromatic, respectively) display chemical abundances similar to DC PNe, suggesting that they are related objects. A comparison of the derived nebular properties with predictions from models combining the theoretical central star evolution with a simple nebular model is also presented. Finally, a possible link between the Spitzer dust properties, chemical abundances, and evolutionary status is discussed.
372. Chemical abundances in 52 M-giant stars
ID:
ivo://CDS.VizieR/J/AJ/161/183
Title:
Chemical abundances in 52 M-giant stars
Short Name:
J/AJ/161/183
Date:
18 Jan 2022
Publisher:
CDS
Description:
We measured ^35^Cl abundances in 52-M giants with metallicities in the range -0.5<[Fe/H]<0.12. Abundances and atmospheric parameters were derived using infrared spectra from CSHELL on the NASA Infrared Telescope Facility and from optical echelle spectra. We measured Cl abundances by fitting a H^35^Cl molecular feature at 3.6985{mu}m with synthetic spectra. We also measured the abundances of O, Ca, Ti, and Fe using atomic absorption lines. We find that the [Cl/Fe] ratio for our stars agrees with chemical evolution models of Cl, and the [Cl/Ca] ratio is broadly consistent with the solar ratio over our metallicity range. Both indicate that Cl is primarily made in core-collapse supernovae with some contributions from Type Ia supernovae. We suggest that other potential nucleosynthesis processes, such as the {nu}-process, are not significant producers of Cl. Finally, we also find our Cl abundances are consistent with HII and planetary nebular abundances at a given oxygen abundance, although there is scatter in the data.
373. Chemical abundances in red giants with Magellan
ID:
ivo://CDS.VizieR/J/AJ/160/181
Title:
Chemical abundances in red giants with Magellan
Short Name:
J/AJ/160/181
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present high-resolution Magellan/MIKE spectroscopy of 42 red giant stars in seven stellar streams confirmed by the Southern Stellar Stream Spectroscopic Survey (S5): ATLAS, Aliqa Uma, Chenab, Elqui, Indus, Jhelum, and Phoenix. Abundances of 30 elements have been derived from over 10000 individual line measurements or upper limits using photometric stellar parameters and a standard LTE analysis. This is currently the most extensive set of element abundances for stars in stellar streams. Three streams (ATLAS, Aliqa Uma, and Phoenix) are disrupted metal-poor globular clusters, although only weak evidence is seen for the light-element anticorrelations commonly observed in globular clusters. Four streams (Chenab, Elqui, Indus, and Jhelum) are disrupted dwarf galaxies, and their stars display abundance signatures that suggest progenitors with stellar masses ranging from 106 to 107M{sun}. Extensive description is provided for the analysis methods, including the derivation of a new method for including the effect of stellar parameter correlations on each star's abundance and uncertainty. This paper includes data gathered with the 6.5m Magellan Telescopes located at Las Campanas Observatory, Chile.
374. Chemical abundances in the PN Wray16-423
ID:
ivo://CDS.VizieR/J/MNRAS/452/4070
Title:
Chemical abundances in the PN Wray16-423
Short Name:
J/MNRAS/452/4070
Date:
21 Oct 2021
Publisher:
CDS
Description:
We performed a detailed analysis of elemental abundances, dust features, and polycyclic aromatic hydrocarbons (PAHs) in the C-rich planetary nebula (PN) Wray16-423 in the Sagittarius dwarf spheroidal galaxy, based on a unique data set taken from the Subaru/HDS, MPG/ESO FEROS, HST/WFPC2, and Spitzer/IRS. We performed the first measurements of Kr, Fe, and recombination O abundance in this PN. The extremely small [Fe/H] implies that most Fe atoms are in the solid phase, considering into account the abundance of [Ar/H]. The Spitzer/IRS spectrum displays broad 16-24 {mu}m and 30 {mu}m features, as well as PAH bands at 6-9 and 10^-14^ {mu}m. The unidentified broad 16-24 {mu}m feature may not be related to iron sulphide (FeS), amorphous silicate, or PAHs. Using the spectral energy distribution model, we derived the luminosity and effective temperature of the central star, and the gas and dust masses. The observed elemental abundances and derived gas mass are in good agreement with asymptotic giant branch nucleosynthesis models for an initial mass of 1.90 M_{sun}_ and a metallicity of Z=0.004. We infer that respectively about 80, 50, and 90 per cent of the Mg, S, and Fe atoms are in the solid phase. We also assessed the maximum possible magnesium sulphide (MgS) and iron-rich sulphide (Fe50S) masses and tested whether these species can produce the band flux of the observed 30 {mu}m feature. Depending on what fraction of the sulphur is in sulphide molecules such as CS, we conclude that MgS and Fe50S could be possible carriers of the 30 {mu}m feature in this PN.
375. Chemical abundances in UV-selected galaxies
ID:
ivo://CDS.VizieR/J/MNRAS/330/75
Title:
Chemical abundances in UV-selected galaxies
Short Name:
J/MNRAS/330/75
Date:
21 Oct 2021
Publisher:
CDS
Description:
We discuss the chemical properties of a sample of UV-selected intermediate-redshift (0<=z<=0.4) galaxies in the context of their physical nature and star-formation history. This work represents an extension of our previous studies of the rest-frame UV-luminosity function (Treyer et al., 1998, Cat. <J/MNRAS/300/303>) and the star-formation properties of the same sample (Sullivan et al., 2000, Cat. <J/MNRAS/312/442>). We revisit the optical spectra of these galaxies and perform further emission-line measurements restricting the analysis to those spectra with the full set of emission lines required to derive chemical abundances. Our final sample consists of 68 galaxies with heavy-element abundance ratios and both UV and CCD B-band photometry.
376. Chemical abundances of giants and subgiants
ID:
ivo://CDS.VizieR/J/A+A/574/A50
Title:
Chemical abundances of giants and subgiants
Short Name:
J/A+A/574/A50
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present fundamental stellar parameters, chemical abundances, and rotational velocities for a sample of 86 evolved stars with planets (56 giants; 30 subgiants), and for a control sample of 137 stars (101 giants; 36 subgiants) without planets. The analysis was based on both high signal-to-noise and resolution echelle spectra. The main goals of this work are i) to investigate chemical differences between evolved stars that host planets and those of the control sample without planets; ii) to explore potential differences between the properties of the planets around giants and subgiants; and iii) to search for possible correlations between these properties and the chemical abundances of their host stars. Implications for the scenarios of planet formation and evolution are also discussed. The fundamental stellar parameters (T_eff_, logg, [Fe/H], {xi}_t_) were computed homogeneously using the FUNDPAR code. The chemical abundances of 14 elements (Na, Mg, Al, Si, Ca, Sc, Ti, V, Cr, Mn, Co, Ni, Zn, and Ba) were obtained using the MOOG code. Rotational velocities were derived from the full width at half maximum of iron isolated lines. In agreement with previous studies, we find that subgiants with planets are, on average, more metal-rich than subgiants without planets by ~0.16dex. The [Fe/H] distribution of giants with planets is centered at slightly subsolar metallicities and there is no metallicity enhancement relative to the [Fe/H] distribution of giants without planets. Furthermore, contrary to recent results, we do not find any clear difference between the metallicity distributions of stars with and without planets for giants with M_*_>1.5M_{sun}_. With regard to the other chemical elements, the analysis of the [X/Fe] distributions shows differences between giants with and without planets for some elements, particularly V, Co, and Ba. Subgiants with and without planets exhibit similar behavior for most of the elements. On the other hand, we find no evidence of rapid rotation among the giants with planets or among the giants without planets. Finally, analyzing the planet properties, some interesting trends might be emerging: i) multi-planet systems around evolved stars show a slight metallicity enhancement compared with single-planet systems; ii) planets with a<~0.5AU orbit subgiants with [Fe/H]>0 and giants hosting planets with a<~1AU have [Fe/H]<0; iii) higher-mass planets tend to orbit more metal-poor giants with M_*_<=1.5M_{sun}_, whereas planets around subgiants seem to follow the planet-mass metallicity trend observed on dwarf hosts; iv) [X/Fe] ratios for Na, Si, and Al seem to increase with the mass of planets around giants; v) planets orbiting giants show lower orbital eccentricities than those orbiting subgiants and dwarfs, suggesting a more efficient tidal circularization or the result of the engulfment of close-in planets with larger eccentricities.
377. Chemical abundances of solar neighbourhood dwarfs
ID:
ivo://CDS.VizieR/J/A+A/562/A71
Title:
Chemical abundances of solar neighbourhood dwarfs
Short Name:
J/A+A/562/A71
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present a detailed elemental abundance study of 714 F and G dwarf and subgiant stars in the Solar neighbourhood. The analysis is based on high-resolution spectra obtained with MIKE on the Magellan telescope, FEROS on the ESO 1.5m and 2.2m telescopes, HARPS on the ESO 3.6m telescope, UVES on the ESO Very Large Telescope, SOFIN and FIES on the Nordic Optical Telescope. Our data show that there is an old and alpha-enhanced disk population, and a younger and less alpha-enhanced disk population. While they overlap greatly in metallicity between -0.7<[Fe/H]<+0.1, they show a bimodal distribution in [alpha/Fe]. This bimodality becomes even clearer if stars where stellar parameters and abundances show larger uncertainties (Teff<5400K) are discarded, showing that it is important to constrain the data set to a narrow range in the stellar parameters if small differences between stellar populations are to be revealed. In addition, we find that the alpha-enhanced population has orbital parameters placing the stellar birthplaces in the inner Galactic disk while the low-alpha stars mainly come from the outer Galactic disk, fully consistent with the recent claims of a short scale-length for the alpha-enhanced Galactic thick disk. We have also investigated the properties of the Hercules stream and the Arcturus moving group.
378. CHemical Abundances of Spirals (CHAOS) II. M51
ID:
ivo://CDS.VizieR/J/ApJ/808/42
Title:
CHemical Abundances of Spirals (CHAOS) II. M51
Short Name:
J/ApJ/808/42
Date:
21 Oct 2021
Publisher:
CDS
Description:
We have observed NGC 5194 (M51a) as part of the CHemical Abundances of Spirals project (CHAOS). Using the Multi Object Double Spectrographs on the Large Binocular Telescope we are able to measure one or more of the temperature-sensitive auroral lines ([OIII]{lambda}4363, [NII]{lambda}5755, [SIII]{lambda}6312) and thus measure "direct" gas-phase abundances in 29 individual HII regions. [OIII]{lambda}4363 is only detected in two HII regions, both of which show indications of excitation by shocks. We compare our data to previous direct abundances measured in NGC 5194 and find excellent agreement ({Delta}[log(O/H)]~0.05) for all but one region. We find no evidence of trends in Ar/O, Ne/O, or S/O within NGC 5194 or compared to other galaxies. We find modest negative gradients in both O/H and N/O with very little scatter ({sigma}<=0.08dex), most of which can be attributed to random error and not to intrinsic dispersion. The gas-phase abundance gradient is consistent with the gradients observed in other interacting galaxies, which tend to be shallower than gradients measured in isolated galaxies. The N/O ratio (<log(N/O)>=-0.62) suggests secondary nitrogen production is responsible for a significantly larger fraction of nitrogen (e.g., factor of 8-10), relative to primary production mechanisms than predicted by theoretical models.
379. CHemical Abundances of Spirals (CHAOS). I. NGC628
ID:
ivo://CDS.VizieR/J/ApJ/806/16
Title:
CHemical Abundances of Spirals (CHAOS). I. NGC628
Short Name:
J/ApJ/806/16
Date:
21 Oct 2021
Publisher:
CDS
Description:
The CHemical Abundances of Spirals (CHAOS) project leverages the combined power of the Large Binocular Telescope (LBT) with the broad spectral range and sensitivity of the Multi Object Double Spectrograph (MODS) to measure "direct" abundances (based on observations of the temperature-sensitive auroral lines) in large samples of HII regions in spiral galaxies. We present LBT MODS observations of 62 HII regions in the nearby spiral galaxy NGC 628, with an unprecedentedly large number of auroral lines measurements (18 [OIII]{lambda}4363, 29 [NII]{lambda}5755, 40 [SIII]{lambda}6312, and 40 [OII]{lambda}{lambda}7320,7330 detections) in 45 HII regions. We conduct a uniform abundance analysis prioritizing the temperatures derived from [SIII]{lambda}6312 and [NII]{lambda}5755, and report the gas-phase abundance gradients for NGC 628. Relative abundances of S/O, Ne/O, and Ar/O are constant across the galaxy, consistent with no systematic change in the upper IMF over the sampled range in metallicity. These alpha-element ratios, along with N/O, all show small dispersions ({sigma}~0.1dex) over 70% of the azimuthally averaged radius. We interpret these results as an indication that, at a given radius, the interstellar medium in NGC 628 is chemically well-mixed. Unlike the gradients in the nearly temperature-independent relative abundances, O/H abundances have a larger intrinsic dispersion of ~0.165dex. We posit that this dispersion represents an upper limit to the true dispersion in O/H at a given radius and that some of that dispersion is due to systematic uncertainties arising from temperature measurements.
380. Chemical analysis of NGC 4636 globular clusters
ID:
ivo://CDS.VizieR/J/ApJ/759/116
Title:
Chemical analysis of NGC 4636 globular clusters
Short Name:
J/ApJ/759/116
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present a spectroscopic analysis of the metallicities, ages, and alpha-elements of the globular clusters (GCs) in the giant elliptical galaxy (gE) NGC 4636 in the Virgo Cluster. Line indices of the GCs are measured from the integrated spectra obtained with Faint Object Camera and Spectrograph on the Subaru 8.2m Telescope. We derive [Fe/H] values of 59 GCs based on the Brodie & Huchra (1990ApJ...362..503B) method, and [Z/H], age, and [{alpha}/Fe] values of 33 GCs from the comparison of the Lick line indices with single stellar population models. The metallicity distribution of NGC 4636 GCs shows a hint of a bimodality with two peaks at [Fe/H]=-1.23({sigma}=0.32) and -0.35({sigma}=0.19). The age spread is large from 2Gyr to 15Gyr and the fraction of young GCs with age <5Gyr is about 27%. The [{alpha}/Fe] of the GCs shows a broad distribution with a mean value [{alpha}/Fe]{approx}0.14dex. The dependence of these chemical properties on the galactocentric radius is weak. We also derive the metallicities, ages, and [{alpha}/Fe] values for the GCs in other nearby gEs (M87, M49, M60, NGC 5128, NGC 1399, and NGC 1407) from the line index data in the literature using the same methods as used for NGC 4636 GCs. The metallicity distribution of GCs in the combined sample of seven gEs including NGC 4636 is found to be bimodal, supported by the KMM test with a significance level of >99.9%. All these gEs harbor some young GCs with ages less than 5Gyr. The mean age of the metal-rich GCs ([Fe/H]>-0.9) is about 3Gyr younger than that of the metal-poor GCs. The mean value of [{alpha}/Fe] of the gE GCs is smaller than that of the Milky Way GCs. We discuss these results in the context of GC formation in gEs.

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