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- ID:
- ivo://CDS.VizieR/J/A+A/423/867
- Title:
- Abundances of distant luminous infrared galaxies
- Short Name:
- J/A+A/423/867
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- One hundred and five 15{mu}m-selected objects in three ISO (Infrared Space Observatory) deep survey fields (CFRS 3h, UDSR and UDSF) are studied on the basis of their high-quality optical spectra with resolution R>1000 from VLT/FORS2. ~92 objects (88%) have secure redshifts, ranging from 0 to 1.16 with a median value of z_med_=0.587.
- 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.
- ID:
- ivo://CDS.VizieR/J/MNRAS/372/1259
- Title:
- Abundances of extragalactic globular clusters
- Short Name:
- J/MNRAS/372/1259
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present measurements of ages, metallicities and [alpha/Fe] ratios for 16 globular clusters (GCs) in NGC 147, 185 and 205 and of the central regions of the diffuse galaxy light in NGC 185 and 205. Our results are based on spectra obtained with the SCORPIO multislit spectrograph at the 6-m telescope of the Russian Academy of Sciences. We include in our analysis high-quality Hubble Space Telescope/WFPC2 photometry of individual stars in the studied GCs to investigate the influence of their horizontal branch (HB) morphology on the spectroscopic analysis. All our sample GCs appear to be old (T>8Gyr) and metal-poor ([Z/H]<1.1), except for the GCs Hubble V in NGC 205 (T=1.2+/-0.6Gyr, [Z/H]=0.6+/-0.2), Hubble VI in NGC 205 (T=4+/-2Gyr, [Z/H]=0.8+/-0.2) and FJJVII in NGC 185 (T=7+/-3Gyr, [Z/H]=0.8+/-0.2). The majority of our GCs sample has solar [alpha/Fe] enhancement in contrast to the halo population of GCs in M31 and the Milky Way. The HB morphologies for our sample GCs follow the same behaviour with metallicity as younger halo Galactic GCs. We show that it is unlikely that they bias our spectroscopic age estimates based on Balmer absorption-line indices. Spectroscopic ages and metallicities of the central regions in NGC 205 and 185 coincide with those obtained from colour-magnitude diagrams. The central field stellar populations in these galaxies have approximately the same age as their most central GCs (Hubble V in NGC 205 and FJJIII in NGC 185), but are more metal-rich than the central GCs.
- 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.
- ID:
- ivo://CDS.VizieR/J/ApJ/817/41
- Title:
- Abundances of 4 metal-poor red giants in BooII
- Short Name:
- J/ApJ/817/41
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present high-resolution Magellan/MIKE spectra of the four brightest confirmed red giant stars in the ultra-faint dwarf galaxy Bootes II (Boo II). These stars all inhabit the metal-poor tail of the BooII metallicity distribution function. The chemical abundance pattern of all detectable elements in these stars is consistent with that of the Galactic halo. However, all four stars have undetectable amounts of neutron-capture elements Sr and Ba, with upper limits comparable to the lowest ever detected in the halo or in other dwarf galaxies. One star exhibits significant radial velocity variations over time, suggesting it to be in a binary system. Its variable velocity has likely increased past determinations of the Boo II velocity dispersion. Our four stars span a limited metallicity range, but their enhanced {alpha}-abundances and low neutron-capture abundances are consistent with the interpretation that Boo II has been enriched by very few generations of stars. The chemical abundance pattern in Boo II confirms the emerging trend that the faintest dwarf galaxies have neutron-capture abundances distinct from the halo, suggesting the dominant source of neutron-capture elements in halo stars may be different than in ultra-faint dwarfs.
- ID:
- ivo://CDS.VizieR/J/ApJ/852/99
- Title:
- Abundances of 3 metal-poor stars in Horologium I
- Short Name:
- J/ApJ/852/99
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present chemical abundance measurements of three stars in the ultrafaint dwarf galaxy Horologium I, a Milky Way satellite discovered by the Dark Energy Survey. Using high-resolution spectroscopic observations, we measure the metallicity of the three stars, as well as abundance ratios of several {alpha}-elements, iron-peak elements, and neutron-capture elements. The abundance pattern is relatively consistent among all three stars, which have a low average metallicity of [Fe/H]~-2.6 and are not {alpha}-enhanced ([{alpha}/Fe]~0.0). This result is unexpected when compared to other low-metallicity stars in the Galactic halo and other ultrafaint dwarfs and suggests the possibility of a different mechanism for the enrichment of Hor I compared to other satellites. We discuss possible scenarios that could lead to this observed nucleosynthetic signature, including extended star formation, enrichment by a Population III supernova, and or an association with the Large Magellanic Cloud.
- 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.
- 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.
- ID:
- ivo://CDS.VizieR/J/A+A/565/A23
- Title:
- Abundances of NGC5897 red giants
- Short Name:
- J/A+A/565/A23
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report for the first time on the chemical composition of the halo cluster NGC 5897 (R_{sun}_=12.5kpc), based on chemical abundance ratios for 27 {alpha}-, iron-peak, and neutron-capture elements in seven red giants. From our high-resolution, high signal-to-noise spectra obtained with theMagellan/MIKE spectrograph, we find a mean iron abundance from the neutral species of [Fe/H]=-2.04+/-0.01(stat.)+/-0.15(sys.), which is more metal-poor than implied by previous photometric and low-resolution spectroscopic studies. NGC 5897 is {alpha}-enhanced (to 0.34+/-0.01dex) and shows Fe-peak element ratios typical of other (metal-poor) halo globular clusters (GCs) with no overall, significant abundance spreads in iron nor in any other heavy element.
