- ID:
- ivo://CDS.VizieR/J/PASJ/60/739
- Title:
- Emission-line stars in the W5E HII region
- Short Name:
- J/PASJ/60/739
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have made a new survey of emission-line stars in the W5 E HII region to investigate the population of PMS stars near the OB stars by using the Wide Field Grism Spectrograph 2 (WFGS2). A total of 139 Halpha emission stars were detected and their g'i'-photometry was performed. Their spatial distribution shows three aggregates, i.e., two aggregates near the bright-rimmed clouds at the edge of the W5 E HII region (BRC 13 and BRC 14) and one near the exciting O7V star. The age and mass of each Halpha star were estimated from an extinction-corrected color-magnitude diagram and theoretical evolutionary tracks. We found, for the first time in this region, that the young stars near the exciting star are systematically older (4Myr) than those near the edge of the HII region (1Myr). This result supports that the formation of stars proceeds sequentially from the center of HII region to the eastern bright rim. We further suggest a possibility that the birth of low-mass stars near the exciting star of the HII region precedes the production of massive OB stars in the pre-existing molecular cloud.
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Search Results
- ID:
- ivo://CDS.VizieR/J/MNRAS/469/1186
- Title:
- Emission-line strengths for 129 galaxies
- Short Name:
- J/MNRAS/469/1186
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We propose a method to substantially increase the flexibility and power of template fitting-based photometric redshifts by transforming a large number of galaxy spectral templates into a corresponding collection of 'fuzzy archetypes' using a suitable set of perturbative priors designed to account for empirical variation in dust attenuation and emission-line strengths. To bypass widely separated degeneracies in parameter space (e.g. the redshift-reddening degeneracy), we train self-organizing maps (SOMs) on large 'model catalogues' generated from Monte Carlo sampling of our fuzzy archetypes to cluster the predicted observables in a topologically smooth fashion. Subsequent sampling over the SOM then allows full reconstruction of the relevant probability distribution functions (PDFs). This combined approach enables the multimodal exploration of known variation among galaxy spectral energy distributions with minimal modelling assumptions. We demonstrate the power of this approach to recover full redshift PDFs using discrete Markov chain Monte Carlo sampling methods combined with SOMs constructed from Large Synoptic Survey Telescope ugrizY and Euclid YJH mock photometry.
- ID:
- ivo://CDS.VizieR/J/ApJ/711/1236
- Title:
- Equivalent width of H_2_ from FUSE
- Short Name:
- J/ApJ/711/1236
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Far Ultraviolet Spectroscopic Explorer (FUSE) has allowed precise determinations of the column densities of molecular hydrogen (H_2_) in Galactic lines of sight with a wide range of pathlengths and extinction properties. However, survey studies of lines of sight with greater extinction have been mostly restricted to the low-J states (lower total angular momentum) in which most molecular hydrogen is observed. This paper presents a survey of column densities for the molecular hydrogen in states of greater rotational excitation (J>=2) in Galactic lines of sight with log N(H_2_)>~20. This study is comprehensive through the highest excited state detectable in each line of sight. J=5 is observed in every line of sight, and we detect J=7 in four lines of sight, J=8 in one line of sight, and vibrationally excited H_2_ in two lines of sight.
- ID:
- ivo://CDS.VizieR/J/AJ/132/85
- Title:
- Equivalent width of 33 metal-poor RHB
- Short Name:
- J/AJ/132/85
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have conducted spectrum analyses of 24 field metal-poor ([Fe/H]<-2) red horizontal-branch (RHB) stars identified in the HK objective-prism survey and 6 such stars in the globular cluster M15, based on high-quality spectra (R~40000, S/N~100) obtained with the Magellan Inamori Kyocera Echelle spectrograph at the Clay 6.5m telescope at Las Campanas Observatory. The atmospheric parameters of the RHB stars provide interesting bridges between turnoff stars of similar temperature and red giant branch (RGB) stars of similar gravity, and they permit investigations of abundance trends [X/Fe] versus [Fe/H] in a relatively unexplored region of the temperature-gravity plane. We find that the Teff, logg, vt, and [Fe/H] values determined from our spectra are consistent with expectations from literature spectroscopic studies of other evolved metal-poor stellar classes.
- ID:
- ivo://CDS.VizieR/J/MNRAS/447/2404
- Title:
- Equivalent width of 21 RR Lyrae stars
- Short Name:
- J/MNRAS/447/2404
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have analysed a sample of 18 RR Lyrae stars (17 fundamental-mode - RRab - and one first overtone - RRc) and three Population II Cepheids (two BL Her stars and one W Vir star), for which high-resolution (R>=30000), high signal-to-noise (S/N>=30) spectra were obtained with either SARG at the Telescopio Nazionale Galileo (La Palma, Spain) or UVES at the ESO Very Large Telescope (Paranal, Chile). Archival data were also analyzed for a few stars, sampling >~3 phases for each star. We obtained atmospheric parameters (T_eff_, logg, v_t_, and [M/H]) and abundances of several iron-peak and {alpha}-elements (Fe, Cr, Ni, Mg, Ca, Si, and Ti) for different pulsational phases, obtaining <[{alpha}/Fe]>=+0.31+/-0.19dex over the entire sample covering -2.2<[Fe/H]<-1.1dex. We find that silicon is indeed extremely sensitive to the phase, as reported by previous authors, and cannot be reliably determined. Apart from this, metallicities and abundance ratios are consistently determined, regardless of the phase, within 0.10-0.15 dex, although caution should be used in the range 0<~{phi}<~0.15. Our results agree with literature determinations for both variable and non-variable field stars, obtained with very different methods, including low and high-resolution spectroscopy. W Vir and BL Her stars, at least in the sampled phases, appear indistinguishable from RRab from the spectroscopic analysis point of view. Our large sample, covering all pulsation phases, confirms that chemical abundances can be obtained for RR Lyrae with the classical EW-based technique and static model atmospheres, even rather close to the shock phases.
- ID:
- ivo://CDS.VizieR/J/MNRAS/448/42
- Title:
- Equivalent widths and atomic data for GCs
- Short Name:
- J/MNRAS/448/42
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Detailed chemical abundances for five stars in two Galactic globular clusters, NGC 5466 and NGC 5024, are presented from high-resolution optical (from the Hobby-Eberley Telescope) and infrared spectra (from the SDSS-III APOGEE survey). We find [Fe/H]=-1.97+/-0.13 dex for NGC 5466, and [Fe/H]=-2.06+/-0.13 dex for NGC 5024, and the typical abundance pattern for globular clusters for the remaining elements, e.g. both show evidence for mixing in their light element abundance ratios (C, N), and asymptotic giant branch contributions in their heavy element abundances (Y, Ba, and Eu). These clusters were selected to examine chemical trends that may correlate them with the Sgr dwarf galaxy remnant, but at these low metallicities no obvious differences from the Galactic abundance pattern are found. Regardless, we compare our results from the optical and infrared analyses to find that oxygen and silicon abundances determined from the infrared spectral lines are in better agreement with the other {alpha}-element ratios and with smaller random errors.
- ID:
- ivo://CDS.VizieR/J/A+A/404/187
- Title:
- Equivalent widths for metal-poor stars
- Short Name:
- J/A+A/404/187
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present element-to-element abundance ratios measured from high dispersion spectra for 150 field subdwarfs and early subgiants with accurate Hipparcos parallaxes (errors<20%). For 50 stars new spectra were obtained using the UVES on Kueyen (VLT UT2), the McDonald 2.7m telescope, and SARG at TNG. Additionally, literature equivalent widths were taken from the works by Nissen & Schuster (1997, Cat. <J/A+A/326/751>), Fullbright (2000AJ....120.1841F), and Prochaska et al. (2000AJ....120.2513P) to complement our data. The whole sample includes both thick disk and halo stars (and a few thin disk stars); most stars have metallicities in the range -2<[Fe/H]<-0.6. We found our data, that of Nissen & Schuster, and that of Prochaska to be of comparable quality; results from Fulbright scatter a bit more, but they are still of very good quality and are extremely useful due to the large size of his sample. The results of the present analysis will be used in forthcoming papers to discuss the chemical properties of the dissipational collapse and accretion components of our Galaxy.
- ID:
- ivo://CDS.VizieR/J/ApJ/740/60
- Title:
- Equivalent widths for NGC2419 and NGC7099 RGB stars
- Short Name:
- J/ApJ/740/60
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- NGC 2419 is a massive outer halo Galactic globular cluster (GC) whose stars have previously been shown to have somewhat peculiar abundance patterns. We have observed seven luminous giants that are members of NGC 2419 with Keck/HIRES at reasonable signal-to-noise ratio. One of these giants is very peculiar, with an extremely low [Mg/Fe] and high [K/Fe] but normal abundances of most other elements. The abundance pattern does not match the nucleosynthetic yields of any supernova model. The other six stars show abundance ratios typical of inner halo Galactic GCs, represented here by a sample of giants in the nearby GC M30. Although our measurements show that NGC 2419 is unusual in some respects, its bulk properties do not provide compelling evidence for a difference between inner and outer halo GCs.
- ID:
- ivo://CDS.VizieR/J/ApJ/760/86
- Title:
- Equivalent widths for 13 NGC2419 RGB stars
- Short Name:
- J/ApJ/760/86
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present new Keck/HIRES observations of six red giants in the globular cluster (GC) NGC 2419. Although the cluster is among the most distant and most luminous in the Milky Way, it was considered chemically ordinary until very recently. Our previous work showed that the near-infrared Ca II triplet line strength varied more than expected for a chemically homogeneous cluster, and that at least one star had unusual abundances of Mg and K. Here, we confirm that NGC 2419 harbors a population of stars, comprising about one-third of its mass, that is depleted in Mg by a factor of eight and enhanced in K by a factor of six with respect to the Mg-normal population. Although the majority, Mg-normal population appears to have a chemical abundance pattern indistinguishable from ordinary, inner-halo GCs, the Mg-poor population exhibits dispersions of several elements. The abundances of K and Sc are strongly anti-correlated with Mg, and some other elements (Si and Ca among others) are weakly anti-correlated with Mg. These abundance patterns suggest that the different populations of NGC 2419 sample the ejecta of diverse supernovae in addition to asymptotic giant branch ejecta. However, the abundances of Fe-peak elements except Sc show no star-to-star variation. We find no nucleosynthetic source that satisfactorily explains all of the abundance variations in this cluster. Because NGC 2419 appears like no other GC, we reiterate our previous suggestion that it is not a GC at all, but rather the core of an accreted dwarf galaxy.
- ID:
- ivo://CDS.VizieR/J/A+A/412/495
- Title:
- Equivalent widths for 6 RS CVn systems
- Short Name:
- J/A+A/412/495
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Photospheric parameters and abundances are presented for a sample of single-lined chromospherically active binaries from a differential LTE analysis of high-resolution spectra. Abundances have been derived for 13 chemical species, including several key elements such as Li, Mg, and Ca.
