- ID:
- ivo://CDS.VizieR/J/AJ/142/136
- Title:
- Spectroscopy of Cepheids. l=30-250{deg}
- Short Name:
- J/AJ/142/136
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This paper reports on the spectroscopic investigation of 238 Cepheids in the northern sky. Of these stars, about 150 are new to the study of the galactic abundance gradient. These new Cepheids bring the total number of Cepheids involved in abundance distribution studies to over 400. In this work, we also consider systematics between various studies and also those which result from the choice of models.
Number of results to display per page
Search Results
- ID:
- ivo://CDS.VizieR/J/ApJS/175/462
- Title:
- Spectroscopy of Coma early-type galaxies
- Short Name:
- J/ApJS/175/462
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The long-slit spectra obtained along the minor axis, offset major axis, and diagonal axis are presented for 12 E and S0 galaxies of the Coma Cluster drawn from a magnitude-limited sample studied before. The rotation curves, velocity dispersion profiles, and the H_3_ and H_4_ coefficients of the Hermite decomposition of the line-of-sight velocity distribution are derived. The radial profiles of the H{beta}, Mg, and Fe line strength indices are measured too. In addition, the surface photometry of the central regions of a subsample of four galaxies recently obtained with the Hubble Space Telescope is presented. The data will be used to construct dynamical models of the galaxies and study their stellar populations.
- ID:
- ivo://CDS.VizieR/J/ApJ/769/54
- Title:
- Spectroscopy of Damped Ly{alpha} (DLA) systems
- Short Name:
- J/ApJ/769/54
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Using a sample of 100 H I-selected damped Ly{alpha} (DLA) systems, observed with the High Resolution Echelle Spectrometer on the Keck I telescope, we present evidence that the scatter in the well-studied correlation between the redshift and metallicity of a DLA is largely due to the existence of a mass-metallicity relationship at each redshift. To describe the fundamental relations that exist between redshift, metallicity, and mass, we use a fundamental plane description, which is described by the following equation: [M/H]=(-1.9+/-0.5)+(0.74+/-0.21)*log{Delta}v_90_-(0.32+/-0.06)*z. Here, we assert that the velocity width, {Delta}v_90_, which is defined as the velocity interval containing 90% of the integrated optical depth, traces the mass of the underlying dark matter halo. This description provides two significant improvements over the individual descriptions of the mass-metallicity correlation and metallicity-redshift correlation. Firstly, the fundamental equation reduces the scatter around both relationships by about 20%, providing a more stringent constraint on numerical simulations modeling DLAs. Secondly, it confirms that the dark matter halos that host DLAs satisfy a mass-metallicity relationship at each redshift between redshifts 2 through 5.
- ID:
- ivo://CDS.VizieR/J/ApJ/730/128
- Title:
- Spectroscopy of DA WD from the SDSS-DR4
- Short Name:
- J/ApJ/730/128
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present an improved spectroscopic and photometric analysis of hydrogen-line DA white dwarfs from the Sloan Digital Sky Survey Data Release 4 (SDSS DR4) based on model atmospheres that include improved Stark broadening profiles with non-ideal gas effects. We also perform a careful visual inspection of all spectroscopic fits with high signal-to-noise ratios (S/Ns>12) and present improved atmospheric parameters (T_eff_ and logg) for each white dwarf. Through a comparison of spectroscopic and photometric temperatures, we report the discovery of 35 DA+DB/DC double degenerate candidates and two helium-rich DA stars. We also determine that a cutoff at S/N=15 optimizes the size and quality of the sample for computing the mean mass of DA white dwarfs, for which we report a value of 0.613M_{sun}_. We compare our results to previous analyses of the SDSS DR4 and find a good agreement if we account for the shift produced by the improved Stark profiles. Finally, the properties of DA white dwarfs in the SDSS are weighed against those of the Villanova White Dwarf Catalog sample of Gianninas et al. (2009JPhCS.172a2021G).
- ID:
- ivo://CDS.VizieR/J/A+A/628/A49
- Title:
- Spectroscopy of dwarf stars
- Short Name:
- J/A+A/628/A49
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- New space missions, such as NASA TESS or ESA PLATO, will focus on bright stars, which have been largely ignored by modern large surveys, especially in the northern sky. Spectroscopic information is of paramount importance in characterising the stars and analysing planets possibly orbiting them, and in studying the Galactic disc evolution. The aim of this work was to analyse all bright (V<8mag) F, G, and K dwarf stars using high-resolution spectra in the selected sky fields near the northern celestial pole. The observations were carried out with the 1.65m diameter telescope at the Molttai Astronomical Observatory and a fibre-fed high-resolution spectrograph covering a full visible wavelength range (4000-8500{AA}). The atmospheric parameters were derived using the classical equivalent width approach while the individual chemical element abundances were determined from spectral synthesis. For both tasks the one-dimensional plane-parallel LTE MARCS stellar model atmospheres were applied. Results. We determined the main atmospheric parameters, kinematic properties, orbital parameters, and stellar ages for 109 newly observed stars and chemical abundances of 23 chemical species for 249 F, G, and K dwarf stars observed in the present study and in our previous study. The [MgI/FeI] ratio was adopted to define the thin-disc ({alpha}-poor) and thick-disc ({alpha}-rich) stars in our sample. We explored the behaviour of 21 chemical species in the [El/FeI] versus [FeI/H] and [El/FeI] versus age planes, and compared the results with the latest Galactic chemical evolution models. We also explored [El/FeI] gradients according to the mean Galactocentric distances and maximum height above the Galactic plane.
- ID:
- ivo://CDS.VizieR/J/AJ/144/78
- Title:
- Spectroscopy of early-type galaxies in A262
- Short Name:
- J/AJ/144/78
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present new radially resolved spectroscopy of eight early-type galaxies in the A262 cluster. The measurements include stellar rotation, velocity dispersion, H_3_ and H_4_coefficients of the line-of-sight velocity distribution along the major and minor axes and an intermediate axis as well as line-strength index profiles of Mg, Fe, and H{beta}. The ionized-gas velocity and velocity dispersion is measured for six sample galaxies along different axes. We derive dynamical mass-to-light ratios and dark matter densities from orbit-based dynamical models, complemented by the galaxies' ages, metallicities, and {alpha}-element abundances from single stellar-population models. The ionized-gas kinematics give a valuable consistency check for the model assumptions about orientation and intrinsic shape of the galaxies. Four galaxies have a significant detection of dark matter and their halos are about 10 times denser than in spirals of the same stellar mass. By calibrating dark matter densities to cosmological simulations we find assembly redshifts of z_DM_{approx}1-3, as previously reported for the Coma Cluster. The dynamical mass that follows the light is larger than expected for a Kroupa stellar initial mass function (IMF), especially in galaxies with high velocity dispersion {sigma}_eff_ inside the effective radius r_eff_. This could indicate a "massive" IMF in massive galaxies. Alternatively, some of the dark matter in massive galaxies could follow the light very closely. In combination with our comparison sample of Coma early-type galaxies, we now have 5 of 24 galaxies where (1) mass follows light to 1-3r_eff_, (2) the dynamical mass-to-light ratio of all the mass that follows the light is large ({approx}8-10 in the Kron-Cousins R band), and (3) the dark matter fraction is negligible to 1-3r_eff_. Unless the IMF in these galaxies is particularly "massive" and somehow coupled to the dark matter content, there seems to be a significant degeneracy between luminous and dark matter in at least some early-type galaxies. The role of violent relaxation is briefly discussed.
- ID:
- ivo://CDS.VizieR/J/ApJ/757/161
- Title:
- Spectroscopy of 56 exoplanet host stars
- Short Name:
- J/ApJ/757/161
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report homogeneous spectroscopic determinations of the effective temperature, metallicity, and projected rotational velocity for the host stars of 56 transiting planets. Our analysis is based primarily on the stellar parameter classification (SPC) technique. We investigate systematic errors by examining subsets of the data with two other methods that have often been used in previous studies (Spectroscopy Made Easy (SME) and MOOG). The SPC and SME results, both based on comparisons between synthetic spectra and actual spectra, show strong correlations between T_eff_, [Fe/H], and log g when solving for all three quantities simultaneously. In contrast the MOOG results, based on a more traditional curve-of-growth approach, show no such correlations. To combat the correlations and improve the accuracy of the temperatures and metallicities, we repeat the SPC analysis with a constraint on log g based on the mean stellar density that can be derived from the analysis of the transit light curves. Previous studies that have not taken advantage of this constraint have been subject to systematic errors in the stellar masses and radii of up to 20% and 10%, respectively, which can be larger than other observational uncertainties, and which also cause systematic errors in the planetary mass and radius.
- ID:
- ivo://CDS.VizieR/J/ApJ/771/107
- Title:
- Spectroscopy of faint KOI stars
- Short Name:
- J/ApJ/771/107
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Stellar properties are measured for a large set of Kepler mission exoplanet candidate host stars. Most of these stars are fainter than 14th magnitude, in contrast to other spectroscopic follow-up studies. This sample includes many high-priority Earth-sized candidate planets. A set of model spectra are fitted to R~3000 optical spectra of 268 stars to improve estimates of T_eff_, log(g), and [Fe/H] for the dwarfs in the range 4750<=T_eff_<=7200K. These stellar properties are used to find new stellar radii and, in turn, new radius estimates for the candidate planets. The result of improved stellar characteristics is a more accurate representation of this Kepler exoplanet sample and identification of promising candidates for more detailed study. This stellar sample, particularly among stars with T_eff_>~5200K, includes a greater number of relatively evolved stars with larger radii than assumed by the mission on the basis of multi-color broadband photometry. About 26% of the modeled stars require radii to be revised upward by a factor of 1.35 or greater, and modeling of 87% of the stars suggest some increase in radius. The sample presented here also exhibits a change in the incidence of planets larger than 3-4R_{Earth}_ as a function of metallicity. Once [Fe/H] increases to >=-0.05, large planets suddenly appear in the sample while smaller planets are found orbiting stars with a wider range of metallicity.
- ID:
- ivo://CDS.VizieR/J/AJ/149/79
- Title:
- Spectroscopy of 299 galaxies from NewHa survey
- Short Name:
- J/AJ/149/79
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Using a sample of 299 H{alpha}-selected galaxies at z~~0.8, we study the relationship between galaxy stellar mass, gas-phase metallicity, and star formation rate (SFR), and compare to previous results. We use deep optical spectra obtained with the IMACS spectrograph at the Magellan telescope to measure strong oxygen lines. We combine these spectra and metallicities with (1) rest-frame UV-to-optical imaging, which allows us to determine stellar masses and dust attenuation corrections, and (2) H{alpha} narrowband imaging, which provides a robust measurement of the instantaneous SFR. Our sample spans stellar masses of ~10^9^-6x10^11^M_{sun}_, SFRs of 0.4-270M_{sun}_/yr, and metal abundances of 12+log(O/H)~~8.3-9.1(~~0.4-2.6Z_{sun}_). The correlations that we find between the H{alpha}-based SFR and stellar mass (i.e., the star-forming "main sequence") and between the stellar mass and metallicity are both consistent with previous z~1 studies of star-forming galaxies. We then study the relationship between the three properties using various plane-fitting techniques and a curve-fitting projection. In all cases, we exclude strong dependence of the M_{star}_-Z relation on SFR, but are unable to distinguish between moderate and no dependence. Our results are consistent with previous mass-metallicity-SFR studies. We check whether data set limitations may obscure a strong dependence on the SFR by using mock samples drawn from the Sloan Digital Sky Survey. These experiments reveal that the adopted signal-to-noise ratio cuts may have a significant effect on the measured dependence. Further work is needed to investigate these results, and to test whether a "fundamental metallicity relation" or a "fundamental plane" describes star-forming galaxies across cosmic time.
- ID:
- ivo://CDS.VizieR/J/A+A/613/A56
- Title:
- Spectroscopy of globular clusters
- Short Name:
- J/A+A/613/A56
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present new abundance measurements for eleven GCs in the Local Group galaxies NGC 147, NGC 6822, and Messier 33. These are combined with previously published observations of four GCs in the Fornax and WLM galaxies. The abundances were determined from analysis of integrated-light spectra, obtained with HIRES on the Keck I telescope and with UVES on the VLT. We find that the clusters with [Fe/H]<-1.5 are all alpha-enhanced at about the same level as Milky Way GCs. Their Na abundances are also generally enhanced relative to Milky Way halo stars, suggesting that these extragalactic GCs resemble their Milky Way counterparts in containing significant fractions of Na-rich stars. For [Fe/H]>-1.5, the GCs in M33 are also alpha-enhanced, while the GCs that belong to dwarfs (NGC 6822 SC7 and Fornax 4) have closer to Solar-scaled alpha-element abundances. The abundance patterns in SC7 are remarkably similar to those in the Galactic GC Ruprecht 106, including significantly sub-solar [Na/Fe] and [Ni/Fe] ratios. In NGC 147, the GCs with [Fe/H]<-2.0 account for about 6% of the total luminosity of stars in the same metallicity range, a lower fraction than those previously found in the Fornax and WLM galaxies, but substantially higher than in the Milky Way halo.