- 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.
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Search Results
- 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.
- 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.
- 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.
- 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.
- 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.
- 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.
- ID:
- ivo://CDS.VizieR/J/ApJ/695/L134
- Title:
- Chemical anomalies in old LMC clusters
- Short Name:
- J/ApJ/695/L134
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- By using the multifiber spectrograph FLAMES mounted at the ESO-VLT, we have obtained high-resolution spectra for 18 giant stars, belonging to three old globular clusters of the Large Magellanic Cloud (namely NGC 1786, 2210, and 2257). While stars in each cluster showed quite homogeneous iron content, within a few cents of dex (the mean values being [Fe/H]=-1.75+/-0.01dex, -1.65+/-0.02dex and -1.95+/-0.02dex for NGC 1786, 2210, and 2257, respectively), we have detected significant inhomogeneities for the [Na/Fe], [Al/Fe], [O/Fe], and [Mg/Fe] abundance ratios, with evidence of [O/Fe] versus [Na/Fe] and [Mg/Fe] versus [Al/Fe] anticorrelations. The trends detected nicely agree with those observed in Galactic Globular Clusters, suggesting that such abundance anomalies are ubiquitous features of old stellar systems and they do not depend on the parent galaxy environment. In NGC 1786 we also detected two extreme O-poor, Na-rich stars. This is the first time that a firm signature of extreme chemical abundance anomalies has been found in an extragalactic stellar cluster.
- ID:
- ivo://CDS.VizieR/J/A+A/281/465
- Title:
- Chemical Composition of alf UMi and V473 Lyr
- Short Name:
- J/A+A/281/465
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The spectrograms of the s-Cepheids alpha-UMi and HR 7308, taken at reciprocal dispersion of 9 A/mm with the Main Stellar Spectrograph at the Special Astrophysical Observatory's 6-m telescope, were analysed for determining chemical elements abundance. The results include the equivalent width, and the abundances in the two stars.
- ID:
- ivo://CDS.VizieR/J/MNRAS/359/865
- Title:
- Chemical composition of delta Sct
- Short Name:
- J/MNRAS/359/865
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present chemical abundances in the photosphere of delta Scuti (delta Sct) - a prototype of the class of pulsating variables - determined from the analysis of a spectrum obtained by using the 2-m telescope at the Peak Terskol Observatory and a high-resolution spectrometer with R=52000, a signal-to-noise ratio 250 and from International Ultraviolet Explorer spectra. The abundance pattern of delta Sct consists of 49 chemical elements. The abundances of 19 elements have not been investigated previously. The abundances of Pr and Nd obtained from the lines of the second and third spectra are equal. The abundances of heavy elements indicate the overabundances with respect to the solar system values up to 1dex. The abundance pattern of delta Sct is similar to the abundance patterns of Am-Fm or delta Del type stars. A splitting of the cores of all clean lines is observed for the spectra of Sct and HD 57749. This can signify evidence of non-radial pulsations in these stars
