- ID:
- ivo://CDS.VizieR/J/A+A/626/A15
- Title:
- Sculptor Red Giant Branch stars abundances
- Short Name:
- J/A+A/626/A15
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present detailed chemical abundances for 99 Red Giant Branch stars in the centre of the Sculptor dwarf spheroidal galaxy, which have been obtained from high-resolution VLT/FLAMES spectroscopy. The abundances of Li, Na, alpha-elements (O, Mg, Si, Ca Ti), iron-peak elements (Sc, Cr, Fe, Co, Ni, Zn), r- and s-process elements (Ba, La, Nd, Eu) were all derived using stellar atmosphere models and semi-automated analysis techniques. The iron abundances, covering the range -2.3<[Fe/H]<-0.9, populate the whole metallicity distribution of the galaxy with the exception of the very low metallicity tail. There is a marked decrease in [{alpha}/Fe] over our sample, from the Galactic halo plateau value at low [Fe/H] and then, after a 'knee', a decrease to sub-solar [alpha/Fe] at high [Fe/H]. This is consistent with products of core-collapse supernovae dominating at early times, followed by the onset of supernovae type Ia as early as ~12Gyr ago. The products from low-mass AGB stars, as traced by the s-process, also participate in the chemical evolution of Sculptor with a timescale comparable to that of supernovae type Ia. However, the r-process is consistent with having no time delay relative to core-collapse supernovae, at least at the later stages of the chemical evolution in Sculptor. Using the simple and well-behaved chemical evolution of Sculptor, we further derive empirical constraints on the relative importance of massive stars and supernovae type Ia to the nucleosynthesis of individual iron-peak and alpha-elements. The most important contribution of supernovae typeIa is to the iron-peak elements: Fe, Cr and Mn; but there is also a modest but non-negligible contribution to both the heavier alpha-elements: S, Ca and Ti, and some of the iron-peak elements: Sc and Co. We see only very small or no contribution to O, Mg, Ni and Zn from supernovae type Ia in Sculptor. The observed chemical abundances in Sculptor show no evidence of a significantly different initial mass function, compared to that of the Milky Way. With the exception of neutron-capture elements at low [Fe/H], the scatter around mean trends in Sculptor for [Fe/H]>-2.3 is extremely low, and compatible with observational errors. Combined with the small scatter in the age-elemental abundances relation, this calls for an efficient mixing of metals in the gas in the centre of Sculptor since ~12Gyr ago.
Number of results to display per page
Search Results
- ID:
- ivo://CDS.VizieR/J/A+A/577/A9
- Title:
- Sc, V, Mn, and Co in Milky Way stars
- Short Name:
- J/A+A/577/A9
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the elemental abundances of a large sample of F and G dwarfs in the solar neighborhood. 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. We focused our study on odd-Z iron-peak elements Sc, V, Mn and Co. Our results show that Sc, V, and Co present similar trend as the alpha elements and in Co case, this is true also when non-local thermodynamic equilibrium corrections (non-LTE, NLTE) are applied. On the contrary Mn is generally underabundant relative the Sun but when NLTE corrections are applied the trend is basically flat with [Mn/Fe]=0. Considering the age as selection criterion for thin and thick disk we did not find any difference for V, Co, and Mn LTE while for Sc and Mn NLTE a small difference seem to be present. Comparisons with the alpha-element Ti show flat trends for all the elements except Mn that present well separated [Mn/Ti]-[Ti/H] for thin and thick disk.
- ID:
- ivo://CDS.VizieR/J/ApJ/869/122
- Title:
- SDSS-DR14 and LAMOST DR6 spectra in GD-1 stream
- Short Name:
- J/ApJ/869/122
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Combining data from Gaia DR2, SDSS DR14, and LAMOST DR6, we update the fit to model of the properties of the stellar stream GD-1 and find that it has an age of ~13Gyr, [Fe/H] of -2.2+/-0.12, and a distance from the Sun of ~8kpc. We tabulate six-dimensional (6D) phase-space fiducial points along the GD-1 stream orbit over a 90{deg} arc. The fitted orbit shows that the stream has an eccentricity e~0.3, perigalacticon of 14.2kpc, apogalacticon of 27.0kpc, and inclination i~40{deg}. There is evidence along the arc for four candidate stellar overdensities, one candidate gap, two candidate stellar underdensities, and that the stream is cut off at {phi}_1_~2{deg} (in the stream-aligned ({phi}_1_, {phi}_2_) coordinate system of Koposov+ 2010ApJ...712..260K). The spur originating at {phi}_1_~-40{deg} implies stars were pulled away from the stream trace by an encounter (potentially a dark matter subhalo). The narrowest place (FWHM~44.6pc) of the GD-1 trace is at ({phi}_1_, {phi}2^c^)~(-14{deg}, 0.15{deg}), which is ~(178.18{deg}, 52.19{deg}) in (RA, DE), where the progenitor is possibly located. We also find six blue horizontal branch and 10 blue stragglers spectroscopic stars in the GD-1 stream.
- ID:
- ivo://CDS.VizieR/J/ApJ/751/130
- Title:
- SDSS-DR7 red HB stars spectroscopic data
- Short Name:
- J/ApJ/751/130
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have selected 556 red horizontal branch stars along the streams of the Sagittarius (Sgr) dwarf galaxy from Sloan Digital Sky Survey DR7 spectroscopic data using a theoretical model. The metallicity and {alpha}-element distributions are investigated for stars in the Sgr streams and for Galactic stars at the same locations. We find that the Sgr stars have two peaks in the metallicity distribution while the Galactic stars have a more prominent metal-poor peak. Meanwhile, [{alpha}/Fe] ratios of the Sgr stars are lower than those of the Galactic stars. Among the Sgr stars, we find a difference in the metallicity distribution between the leading and trailing arms of the Sgr tidal tails. The metallicity and [{alpha}/Fe] distribution of the leading arm is similar to that of the Galaxy. The trailing arm is composed mainly of a metal-rich component and [{alpha}/Fe] is obviously lower than that of the Galactic stars. The metallicity gradient is -(1.8+/-0.3)x10^-3^dex/deg in the first wrap of the trailing arm and -(1.5+/-0.4)x10^-3^dex/deg in the first wrap of the leading arm. No significant gradient exists along the second wraps of the leading or trailing arms. It seems that the Sgr dwarf galaxy initially lost the metal-poor component in the second wrap (older) arms due to the tidal force of our Galaxy and then the metal-rich component is disrupted in the first wrap (younger) arms. Finally, we found that the velocity dispersion of the trailing arm from 88{deg}<{Lambda}_{sun}_<112{deg} is {sigma}=9.808+/-1.0km/s, which is consistent with previous work in the literature.
- ID:
- ivo://CDS.VizieR/J/A+A/546/A122
- Title:
- SDSS extremely metal-poor emission-line galaxies
- Short Name:
- J/A+A/546/A122
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present 6.5-m MMT and 3.5m APO spectrophotometry of 69 HII regions in 42 low-metallicity emission-line galaxies, selected from the data release 7 of the Sloan Digital Sky Survey to have mostly [OIII]{lambda}4959/H{beta}<~1 and [NII]{lambda}6583/H{beta}<~0.1. The electron temperature-sensitive emission line [OIII]{lambda}4363 is detected in 53 HII regions allowing a direct abundance determination. The oxygen abundance in the remaining 16 HII regions is derived using a semi-empirical method. The oxygen abundance of the galaxies in our sample ranges from 12+logO/H~7.1 to ~7.9, with 14 HII regions in 7 galaxies with 12+logO/H<=7.35. In 5 of the latter galaxies, the oxygen abundance is derived here for the first time. Including other known extremely metal-deficient emission-line galaxies from the literature, e.g. SBS 0335-052W, SBS 0335-052E and I Zw 18, we have compiled a sample of the 17 most metal-deficient (with 12+logO/H<=7.35) emission-line galaxies known in the local universe. There appears to be a metallicity floor at 12+log O/H~6.9, suggesting that the matter from which dwarf emission-line galaxies formed was pre-enriched to that level by e.g. Population III stars.
- ID:
- ivo://CDS.VizieR/J/ApJ/863/134
- Title:
- SDSS low-metallicity blue compact dwarf galaxies
- Short Name:
- J/ApJ/863/134
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report a method of identifying candidate low-metallicity blue compact dwarf galaxies (BCDs) from the Sloan Digital Sky Survey (SDSS) imaging data, and present 3m Lick Observatory and 10m W.M. Keck Observatory optical spectroscopic observations of 94 new systems that have been discovered with this method. The candidate BCDs are selected from Data Release 12 (DR12) of SDSS on the basis of their photometric colors and morphologies. Using the Kast spectrometer on the 3m telescope, we confirm that the candidate low-metallicity BCDs are emission-line galaxies, and we make metallicity estimates using the empirical R and S calibration methods. Follow-up observations on a subset of the lowest-metallicity systems are made at Keck using the Low Resolution Imaging Spectrometer, which allow for a direct measurement of the oxygen abundance. We determine that 45 of the reported BCDs are low-metallicity candidates with 12+log(O/H)<=7.65, including six systems which are either confirmed or projected to be among the lowest-metallicity galaxies known, at 1/30 of the solar oxygen abundance, or 12+log(O/H)~7.20.
1187. SDSS RGB stars distances
- ID:
- ivo://CDS.VizieR/J/ApJ/794/60
- Title:
- SDSS RGB stars distances
- Short Name:
- J/ApJ/794/60
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present distance determinations for a large and clean sample of red giant branch stars selected from the ninth data release of the Sloan Digital Sky Survey (Adelman-McCarthy et al. 2012ApJS..203...21A, Cat. V/139). The distances are calculated based on both observational cluster fiducials and theoretical isochrones. Distributions of distances from the two methods are very similar with peaks at about 10 kpc and tails extending to more than 70 kpc. We find that distances from the two methods agree well for the majority of the sample stars; though, on average, distances based on isochrones are 10% higher than those based on fiducials. We test the accuracy of our distance determinations using 332 stars from 10 Galactic globular and open clusters. The average relative deviation from the literature cluster distances is 4% for the fiducial-based distances and 8% for the isochrone-based distances, both of which are within the uncertainties. We find that the effective temperature and surface gravity derived from low-resolution spectra are not accurate enough to essentially improve the performance of distance determinations. However, for stars with significant extinction, effective temperature may help to better constrain their distances to some extent. We make our sample stars and their distances available from an online catalog. The catalog comprises 17941 stars with reasonable distance estimations reaching to more than 70 kpc, which is suitable for the investigation of the formation and evolution of the Galaxy, especially the Galactic halo.
- ID:
- ivo://CDS.VizieR/J/ApJS/153/429
- Title:
- SDSS strong emission line HII galaxies
- Short Name:
- J/ApJS/153/429
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the first edition of the SDSS HII galaxies with Oxygen abundances Catalog (SHOC), which is a listing of strong emission-line galaxies (ELGs) from the Sloan Digital Sky Survey (SDSS, see http://www.sdss.org). We present 612 SDSS emission-line galaxies (624 separate SDSS targets in total), for which the oxygen abundances 12+log(O/H) have rms uncertainties <=0.20dex. The subsample of 263 ELGs (272 separate SDSS targets) have an uncertainty <=0.10dex, while 459 ELGs (470 separate SDSS targets) have an uncertainty <=0.15dex. The catalog includes the main parameters of all selected ELGs, the intensities and equivalent widths of hydrogen and oxygen emission lines, as well as oxygen abundances with their uncertainties. The information on the presence of Wolf-Rayet blue and/or red bumps in 109 galaxies is also included. With the use of combined g, r, i SDSS images we performed visual morphological classification of all SHOC galaxies. Four hundred sixty-one galaxies (75%) are classified as confident or probable blue compact galaxies (BCG/BCG?), 78 as irregular ones, 20 as low surface brightness galaxies (LSBG), 10 as obviously interacting, and 43 as spiral galaxies. In creating the catalog, 30 narrow-line active galactic nuclei and 69 LINERs were also identified; these are also presented apart of the main catalog.
- ID:
- ivo://CDS.VizieR/J/AJ/157/70
- Title:
- Search for sodium-rich stars among metal-poor stars
- Short Name:
- J/AJ/157/70
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Sodium-rich stars are often found in globular clusters giants. However, some sodium-rich stars have been found among field metal-poor stars. These stars are considered as evaporated from globular clusters. Identified such kind of stars among the field stars in the Galaxy may provide insights of which mechanism was responsible for the ejection from a globular cluster and may reveal some chemical peculiarity. Therefore, we started a search, using high-resolution spectroscopy, among metal-poor stars from several sources of the literature to find a sodium-rich star. Here we present the results for the temperature, gravity, metallicity, and sodium abundances for the stars of our sample. For many of them we determined the temperature, gravity, metallicity, and sodium abundances for the first time. As a result of our search we found one star, CD-23{deg}16310, which has a [Na/Fe] ratio of +1.09. We also show that CD-23{deg}16310 is not a carbon-enhanced metal-poor (CEMP) star since carbon is not enriched but is nitrogen-rich. We did not detect any variation of the radial velocity that would support the hypothesis of mass transfer. Thus, the high sodium and nitrogen abundance could be due to a strong internal mixing process, suggesting that CD-23{deg}16310 is an early asymptotic giant branch star.
- ID:
- ivo://CDS.VizieR/J/AJ/159/124
- Title:
- Searching Kepler data. I. 17 new planets
- Short Name:
- J/AJ/159/124
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of an independent search of all ~200000 stars observed over the four year Kepler mission (Q1-Q17) for multiplanet systems, using a three-transit minimum detection criterion to search orbital periods up to hundreds of days. We incorporate both automated and manual triage, and provide estimates of the completeness and reliability of our vetting pipeline. Our search returned 17 planet candidates (PCs) in addition to thousands of known Kepler Objects of Interest (KOIs), with a 98.8% recovery rate of already confirmed planets. We highlight the discovery of one candidate, KIC-7340288b, that is both rocky (radius=<1.6R_{Earth}_) and in the Habitable Zone (insolation between 0.25 and 2.2 times the Earth's insolation). Another candidate is an addition to the already known KOI-4509 system. We also present adaptive optics imaging follow-up for six of our new PCs, two of which reveal a line-of-sight stellar companion within 4".
