- ID:
- ivo://CDS.VizieR/J/A+A/581/A70
- Title:
- Grid of NLTE EW and NLTE corrections BaII lines
- Short Name:
- J/A+A/581/A70
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a grid of computed non-local thermodynamic equilibrium (NLTE) equivalent widths (EW) and NLTE abundance corrections for four Ba II lines: 4554, 5853, 6141, and 6496{AA}. The grid can be useful in deriving the NLTE barium abundance in stars having parameters in the following ranges: effective temperature from 4000K to 6500K, surface gravity log g from 0 to 5, microturbulent velocity 0km/s to 3km/s, metallicity [Fe/H] from -2 to +0.5, and [Ba/Fe] from -0.4 to +0.6. The NLTE abundance can be either derived by EW interpolation (using the observed Ba II line EW) or by using the NLTE correction applied to a previously determined LTE abundance. Ba II line equivalent widths and the NLTE corrections were calculated using the updated MULTI code and the Ba II atomic model that was previously applied to determine the NLTE barium abundance in different types of stars. The grid is available on-line through the web, and we find that the grid Ba NLTE corrections are almost as accurate as direct NLTE profile fitting (to within 0.05-0.08dex). For the weakest Ba II line (5853{AA}) the LTE abundances almost agree with the NLTE abundances, whereas the other three Ba II lines, 4554, 6141, and 6496{AA}, need NLTE corrections even at the highest metallicities tested here. The 4554{AA} line is extremely strong and should not be used for abundance analysis above [Fe/H]=-1. Furthermore, we tested the impact of different model atmospheres and spectrum synthesis codes and found average differences of 0.06 dex and 0.09 dex, respectively, for all four lines. At these metallicities we find an average Delta NLTE of +/-0.1dex for the three useful Ba lines for subsolar cool dwarfs.
Number of results to display per page
Search Results
- ID:
- ivo://CDS.VizieR/J/ApJS/256/41
- Title:
- Grid of synthetic spectra for subdwarfs
- Short Name:
- J/ApJS/256/41
- Date:
- 22 Feb 2022
- Publisher:
- CDS
- Description:
- A new grid of detailed atmosphere model spectra for hot and moderately cool subdwarf stars is presented. High-resolution spectra and synthetic photometry are calculated in the range from 1000{AA} to 10,000{AA} using Non-LTE fully line- blanketed atmosphere structures. Our grid covers eight temperatures within 10000<Teff[K]<65000, three surface gravities in the range 4.5<logg[cgs]<6.5, two helium abundances matching two extreme helium-rich and helium-poor scenarios, and two limiting metallicity boundaries regarding both solar ([Fe/H]=0) and Galactic halo ([Fe/H]=-1.5 and [alpha/Fe]=+0.4). Besides its application in the determination of fundamental parameters of subdwarfs in isolation and in binaries, the resulting database is also of interest for population synthesis procedures in a wide variety of stellar systems.
- ID:
- ivo://CDS.VizieR/VI/134
- Title:
- Grids of ATLAS9 Model Atmospheres and MOOG spectra
- Short Name:
- VI/134
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A grid of ATLAS9 model atmospheres has been computed, spanning Teff in 3500--8000K, log.g in 0.0--5.0, [Fe/H] in -4.0--0.0, [{alpha}/Fe] in -0.08--1.2. These parameters are appropriate for stars in the red giant branch, subgiants, and the lower main sequence. The main difference from a previous, similar grid (Castelli & Kurucz 2003, "Modelling of Stellar Atmospheres", 210, astro-ph/0405087) is the range of [{alpha}/Fe] values. A grid of synthetic spectra, calculated from the model atmospheres, is also presented. The fluxes are computed every 0.02{AA} from 630nm to 910nm. The microturbulent velocity is given by a relation to the surface gravity. This relation is appropriate for giants, but not for subgiants or dwarfs. Therefore, caution is urged for the synthetic spectra with log.g>3.5.
- ID:
- ivo://CDS.VizieR/J/ApJ/812/114
- Title:
- Grism Lens-Amplified Survey from Space (GLASS). I.
- Short Name:
- J/ApJ/812/114
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We give an overview of the Grism Lens Amplified Survey from Space (GLASS), a large Hubble Space Telescope program aimed at obtaining grism spectroscopy of the fields of 10 massive clusters of galaxies at redshift z=0.308-0.686, including the Hubble Frontier Fields (HFF). The Wide Field Camera 3 (WFC3) yields near-infrared spectra of the cluster cores covering the wavelength range 0.81-1.69{mu}m through grisms G102 and G141, while the Advanced Camera for Surveys in parallel mode provides G800L spectra of the infall regions of the clusters. The WFC3 spectra are taken at two almost orthogonal position angles in order to minimize the effects of confusion. After summarizing the scientific drivers of GLASS, we describe the sample selection as well as the observing strategy and data processing pipeline. We then utilize MACS J0717.5+3745, a HFF cluster and the first one observed by GLASS, to illustrate the data quality and the high-level data products. Each spectrum brighter than H_AB_=23 is visually inspected by at least two co-authors and a redshift is measured when sufficient information is present in the spectra. Furthermore, we conducted a thorough search for emission lines through all of the GLASS WFC3 spectra with the aim of measuring redshifts for sources with continuum fainter than H_AB_=23. We provide a catalog of 139 emission-line-based spectroscopic redshifts for extragalactic sources, including three new redshifts of multiple image systems (one probable, two tentative).
- ID:
- ivo://CDS.VizieR/J/AJ/157/21
- Title:
- Ground-based spectroscopy of the exoplanet XO-2b
- Short Name:
- J/AJ/157/21
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Exoplanets orbiting close to their host star are expected to support a large ionosphere, which extends to larger pressures than witnessed in our solar system. These ionospheres can be investigated with ground-based transit observations of the optical signatures of alkali metals, which are the source of the ions. However, most ground-based transit spectra do not systematically resolve the wings of the features and continuum, as needed to constrain the alkali abundances. Here we present new observations and analyses of optical transit spectra that cover the Na doublet in the atmosphere of the exoplanet XO-2b. To assess the consistency of our results, observations were obtained from two separate platforms: Gemini/GMOS and Mayall/KOSMOS. To mitigate the systematic errors, we chose XO-2, because it has a binary companion of the same brightness and stellar type, which provides an ideal reference star to model Earth's atmospheric effects. We find that interpretation of the data is highly sensitive to time-varying translations along the detector, which change according to wavelength and differ between the target and reference star. It was necessary to employ a time-dependent cross-correlation to align our wavelength bins and correct for atmospheric differential refraction. This approach allows us to resolve the wings of the Na line across five wavelength bins at a resolution of ~1.6 nm and limit the abundance of Na. We obtain consistent results from each telescope with an Na amplitude of 521+/-161 and 403+/-186 ppm for GMOS and KOSMOS, respectively. The results are analyzed with a radiative transfer model that includes the effects of ionization. The data are consistent with a clear atmosphere between ~1 and 100 mbar that establishes a lower limit on Na at 0.4_-0.3_^+2^ ppm ([Na/H]=-0.64_-0.6_^+0.78^), consistent with solar. However, we cannot rule out the presence of clouds at ~10 mbar that allow for higher Na abundances, which would be consistent with the stellar metallicity measured for the host star ([Na/H]=0.485+/-0.043).
- ID:
- ivo://CDS.VizieR/J/A+A/573/A111
- Title:
- Group-dominant elliptical galaxies CO spectra
- Short Name:
- J/A+A/573/A111
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present IRAM 30m telescope observations of the CO(1-0) and (2-1) lines in a sample of 11 group-dominant elliptical galaxies selected from the CLoGS nearby groups sample. Our observations confirm the presence of molecular gas in 4 of the 11 galaxies at >4{sigma} significance, and combining these with data from the literature we find a detection rate of 43+/-14%, significantly higher than for the wider population of elliptical galaxies, and comparable to the detection rate for nearby radio galaxies. Those group-dominant galaxies which are detected typically contain ~2x10^8^M_{sun}_ of molecular gas, and although most have low star formation rates (<1M_{sun}_/yr) they have short depletion times, indicating that the gas must be replenished on timescales 10^8^yr. Almost all of the galaxies contain active nuclei, and we note that while CO detections are more common in the most radio-loud galaxies, the mass of molecular gas required to power the active nuclei through accretion is small compared to the masses observed. We consider the possible origin mechanisms for the gas, through cooling of stellar ejecta within the galaxies, group-scale cooling flows, and gas-rich mergers, and find probable examples of each type within our sample, confirming that a variety of processes act to drive the build up of molecular gas in group-dominant ellipticals.
- ID:
- ivo://CDS.VizieR/J/ApJ/833/194
- Title:
- Group of galaxies in gravitational lens fields
- Short Name:
- J/ApJ/833/194
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- With a large, unique spectroscopic survey in the fields of 28 galaxy-scale strong gravitational lenses, we identify groups of galaxies in the 26 adequately sampled fields. Using a group-finding algorithm, we find 210 groups with at least 5 member galaxies; the median number of members is 8. Our sample spans redshifts of 0.04<=z_grp_<=0.76 with a median of 0.31, including 174 groups with 0.1<z_grp_<0.6. The groups have radial velocity dispersions of 60<={sigma}_grp_<=1200km/s with a median of 350km/s. We also discover a supergroup in field B0712+472 at z=0.29 that consists of three main groups. We recover groups similar to ~85% of those previously reported in these fields within our redshift range of sensitivity and find 187 new groups with at least five members. The properties of our group catalog, specifically, (1) the distribution of {sigma}_grp_, (2) the fraction of all sample galaxies that are group members, and (3) the fraction of groups with significant substructure, are consistent with those for other catalogs. The distribution of group virial masses agrees well with theoretical expectations. Of the lens galaxies, 12 of 26 (46%) (B1422+231, B1600+434, B2114+022, FBQS J0951+2635, HE0435-1223, HST J14113+5211, MG0751+2716, MGJ1654+1346, PG 1115+080, Q ER 0047-2808, RXJ1131-1231, and WFI J2033-4723) are members of groups with at least five galaxies, and one more (B0712+472) belongs to an additional, visually identified group candidate. There are groups not associated with the lens that still are likely to affect the lens model; in six of 25 (24%) fields (excluding the supergroup), there is at least one massive ({sigma}_grp_>=500km/s) group or group candidate projected within 2' of the lens.
- ID:
- ivo://CDS.VizieR/J/ApJ/826/71
- Title:
- Growth curves of CALIFA spiral galaxies
- Short Name:
- J/ApJ/826/71
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This paper aims to provide aperture corrections for emission lines in a sample of spiral galaxies from the Calar Alto Legacy Integral Field Area Survey (CALIFA; Sanchez+, 2012A&A...538A...8S) database. In particular, we explore the behavior of the log([OIII]{lambda}5007/H{beta})/([NII]{lambda}6583/H{alpha}) (O3N2) and log[NII]{lambda}6583/H{alpha} (N2) flux ratios since they are closely connected to different empirical calibrations of the oxygen abundances in star-forming galaxies. We compute the median growth curves of H{alpha}, H{alpha}/H{beta}, O3N2, and N2 up to 2.5R_50_ and 1.5 disk Reff. These distances cover most of the optical spatial extent of the CALIFA galaxies. The growth curves simulate the effect of observing galaxies through apertures of varying radii. We split these growth curves by morphological types and stellar masses to check if there is any dependence on these properties. The median growth curve of the H{alpha} flux shows a monotonous increase with radius with no strong dependence on galaxy inclination, morphological type, and stellar mass. The median growth curve of the H{alpha}/H{beta} ratio monotonically decreases from the center toward larger radii, showing for small apertures a maximum value of ~10% larger than the integrated one. It does not show any dependence on inclination, morphological type, and stellar mass. The median growth curve of N2 shows a similar behavior, decreasing from the center toward larger radii. No strong dependence is seen on the inclination, morphological type, and stellar mass. Finally, the median growth curve of O3N2 increases monotonically with radius, and it does not show dependence on the inclination. However, at small radii it shows systematically higher values for galaxies of earlier morphological types and for high stellar mass galaxies. Applying our aperture corrections to a sample of galaxies from the SDSS survey at 0.02<=z<=0.3 shows that the average difference between fiber-based and aperture-corrected oxygen abundances, for different galaxy stellar mass and redshift ranges, reaches typically to ~11%, depending on the abundance calibration used. This average difference is found to be systematically biased, though still within the typical uncertainties of oxygen abundances derived from empirical calibrations. Caution must be exercised when using observations of galaxies for small radii (e.g., below 0.5 Reff) given the high dispersion shown around the median growth curves. Thus, the application of these median aperture corrections to derive abundances for individual galaxies is not recommended when their fluxes come from radii much smaller than either R_50_ or Reff.
- ID:
- ivo://CDS.VizieR/J/other/JAD/14.1
- Title:
- GSC04778-00152 photometry and spectroscopy
- Short Name:
- J/other/JAD/14.1
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Photometric and spectroscopic data of the southern contact binary GSC 04778-00152 are presented. Six new times of minimum are listed. For modelling purposes, we provide UBVRI phase diagrams of the contact binary with the contribution of the nearby companion removed.
- ID:
- ivo://CDS.VizieR/J/A+A/598/A59
- Title:
- G31.41+0.31 SMA spectra
- Short Name:
- J/A+A/598/A59
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The detection of complex organic molecules related with prebiotic chemistry in star-forming regions allows us to investigate how the basic building blocks of life are formed. Ethylene glycol (CH_2_OH)_2_ is the simplest sugar alcohol and the reduced alcohol of the simplest sugar glycoladehyde (CH_2_OHCHO). We study the molecular abundance and spatial distribution of (CH_2_OH)_2_, CH_2_OHCHO and other chemically related complex organic species (CH_3_OCHO, CH_3_OCH_3_, and C_2_H_5_OH) towards the chemically rich massive star-forming region G31.41+0.31. We analyzed multiple single-dish (Green Bank Telescope and IRAM 30m) and interferometric (Submillimeter Array) spectra towards G31.41+0.31, covering a range of frequencies from 45 to 258GHz. We fitted the observed spectra with a local thermodynamic equilibrium (LTE) synthetic spectra, and obtained excitation temperatures and column densities. We compared our findings in G31.41+0.31 with the results found in other environments, including low- and high-mass star-forming regions, quiescent clouds and comets.
