- ID:
- ivo://CDS.VizieR/J/ApJ/886/10
- Title:
- Dwarfs or giants? Stellar metallicities & distances
- Short Name:
- J/ApJ/886/10
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a new fully data-driven algorithm that uses photometric data from the Canada-France Imaging Survey (CFIS; u), Pan-STARRS 1 (PS1; griz), and Gaia (G) to discriminate between dwarf and giant stars and to estimate their distances and metallicities. The algorithm is trained and tested using the Sloan Digital Sky Survey (SDSS)/SEGUE spectroscopic data set and Gaia photometric/astrometric data set. At [Fe/H]<-1.2, the algorithm succeeds in identifying more than 70% of the giants in the training/test set, with a dwarf contamination fraction below 30% (with respect to the SDSS/SEGUE data set). The photometric metallicity estimates have uncertainties better than 0.2dex when compared with the spectroscopic measurements. The distances estimated by the algorithm are valid out to a distance of at least ~80kpc without requiring any prior on the stellar distribution and have fully independent uncertainties that take into account both random and systematic errors. These advances allow us to estimate these stellar parameters for approximately 12 million stars in the photometric data set. This will enable studies involving the chemical mapping of the distant outer disk and the stellar halo, including their kinematics using the Gaia proper motions. This type of algorithm can be applied in the southern hemisphere to the first release of LSST data, thus providing an almost complete view of the external components of our Galaxy out to at least ~80kpc. Critical to the success of these efforts will be ensuring well-defined spectroscopic training sets that sample a broad range of stellar parameters with minimal biases. A catalog containing the training/test set and all relevant parameters within the public footprint of CFIS is available online.
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- ID:
- ivo://CDS.VizieR/J/A+A/645/A92
- Title:
- Dwarf spheroidal galaxies in CenA group
- Short Name:
- J/A+A/645/A92
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Dwarf spheroidal galaxies (dSphs) have been extensively investigated in the Local Group, but their low luminosity and surface brightness make similar work in more distant galaxy groups challenging. Modern instrumentation unlocks the possibility of scrutinizing these faint systems in other environments, expanding the parameter space of group properties. We use MUSE spectroscopy to study the properties of 14 known or suspected dSph satellites of Cen A. Twelve targets are confirmed to be group members based on their radial velocities. Two targets are background galaxies at ~50Mpc: KK 198 is a face-on spiral galaxy, and dw1315-45 is an ultra-diffuse galaxy with an effective radius of ~2300pc. The 12 confirmed dSph members of the Cen A group have old and metal-poor stellar populations and follow the stellar metallicity-luminosity relation defined by the dwarf galaxies in the Local Group. In the three brightest dwarf galaxies (KK 197, KKs 55, and KKs 58), we identify globular clusters, as well as a planetary nebula in KK197, although its association with this galaxy and/or the extended halo of Cen A is uncertain. Using four discrete tracers, we measure the velocity dispersion and dynamical mass of KK197. This dSph appears dark matter dominated and lies on the radial acceleration relation of star-forming galaxies within the uncertainties. It also is consistent with predictions stemming from modified Newtonian dynamics (MOND). Surprisingly, in the dwarf KK203 we find an extended H ring. Careful examination of Hubble Space Telescope photometry reveals a very low level of star formation at ages between 30-300Myr. The H{alpha} emission is most likely linked to a ~40Myr old supernova remnant, although other possibilities for its origin cannot be entirely ruled out.
- ID:
- ivo://CDS.VizieR/J/other/NatAs/5.707
- Title:
- Dwarf stars asteroseismic rotation rates
- Short Name:
- J/other/NatAs/5.
- Date:
- 17 Jan 2022 00:29:40
- Publisher:
- CDS
- Description:
- Studies using asteroseismic ages and rotation rates from star-spot rotation have indicated that standard age-rotation relations may break down roughly half way through the main sequence lifetime, a phenomenon referred to as weakened magnetic braking. Although rotation rates from spots can be difficult to determine for older, less active stars, rotational splitting of asteroseismic oscillation frequencies can provide rotation rates for both active and quiescent stars, and so can confirm whether this effect really takes place on the main sequence. We obtained asteroseismic rotation rates of 91 main sequence stars showing high signal-to-noise modes of oscillation. Using these new rotation rates, along with effective temperatures, metallicities and seismic masses and ages, we built a hierarchical Bayesian mixture model to determine whether the ensemble more closely agreed with a standard rotational evolution scenario, or one where weakened magnetic braking takes place. The weakened magnetic braking scenario was found to be 98.4% more likely for our stellar ensemble, adding to the growing body of evidence for this stage of stellar rotational evolution. This work presents a large catalogue of seismic rotation rates for stars on the main sequence, which opens up possibilities for more detailed ensemble analysis of rotational evolution with Kepler.
- ID:
- ivo://CDS.VizieR/J/A+A/658/A47
- Title:
- Dwarf stars limb-darkening coefficients
- Short Name:
- J/A+A/658/A47
- Date:
- 22 Feb 2022
- Publisher:
- CDS
- Description:
- Stellar models applied to large stellar surveys of the Milky Way need to be properly tested against a sample of stars with highly reliable fundamental stellar parameters. We have established a program aiming to deliver such a sample of stars. Here we present new fundamental stellar parameters of nine dwarf stars that will be used as benchmark stars for large stellar surveys. One of these stars is the solar-twin 18Sco, which is also one of the Gaia-ESO benchmarks. The goal is to reach a precision of 1% in effective temperatures (Teff). This precision is important for accurate determinations of the full set of fundamental parameters and abundances of stars observed by the surveys. We observed HD131156 (xi Boo), HD146233 (18 Sco), HD152391, HD173701, HD185395 (theta Cyg), HD186408 (16 Cyg A), HD186427 (16 Cyg B), HD190360 and HD207978 (15 Peg) using the high angular resolution optical interferometric instrument PAVO at the CHARA Array. We derived limb-darkening corrections from 3D model atmospheres and determined Teff directly from the Stefan-Boltzmann relation, with an iterative procedure to interpolate over tables of bolometric corrections. Surface gravities were estimated from comparisons to Dartmouth stellar evolution model tracks. We collected spectroscopic observations from the ELODIE spectrograph and estimated metallicities ([Fe/H]) from a 1D non-local thermodynamic equilibrium (NLTE) abundance analyses of unblended lines of neutral and singly ionized iron. For eight of the nine stars we measure the Teff less than 1%, and for one star better than 2%. We determined the median uncertainties in log g and [Fe/H] as 0.015dex and 0.05dex, respectively. This study presents updated fundamental stellar parameters of nine dwarf stars that can be used as new set of benchmarks. All fundamental stellar parameters were based on consistently combining interferometric observations, 3D limb-darkening modelling and spectroscopic analysis. The next paper in this series will extend our sample to giants in the metal-rich range.
- ID:
- ivo://nasa.heasarc/morbbincat
- Title:
- Dynamical Masses of Selected Orbital Binary Systems
- Short Name:
- MORBBINCAT
- Date:
- 27 Sep 2024
- Publisher:
- NASA/GSFC HEASARC
- Description:
- Orbital binary stars are essential objects for determining dynamical and physical properties of stars through a combined analysis of photometric and astrometric data. The authors have compiled a set of orbital binaries with known trigonometric parallaxes and orbits of high quality, using data from current versions of the Observatorio Astronomico Ramon Maria Aller Catalog (OARMAC) of Orbits and Ephemerides of Visual Double Stars (Docobo et al. 2001, AcA, 51, 353) and the Sixth Catalog of Orbits of Visual Binary Stars (ORB6: Mason and Hartkopf 2007, IAUS 240, 575; Hartkopf et al. 2001, AJ, 122, 3472), as well as including updated information from the Washington Double Star (WDS) Catalog and SIMBAD. They constructed distributions of orbital binaries of the dynamical mass, period, semi-major axis, and eccentricity of systems, which characterize the set. Some problems related to the parametrization of orbital binaries are also discussed in the paper. To compile the orbit list, the authors combined data from both OARMAC and ORB6. At this stage, they maintained systems without parallaxes, but removed systems without a period or semi-major axis. The resulting list contained 3139 orbits for 2278 pairs: 1588 pairs have a single orbit, 548 pairs have two orbits, 120 pairs have three orbits, 19 pairs have four orbits, one pair has five orbits, and two pairs have seven orbits. Table 1 in the reference paper (not part of this HEASARC table) contains a compiled set of 3139 orbit solutions for visual binary stars. Separate entries are provided for different pairs in multiple systems. Several solutions per pair are possible. Each entry includes main orbital elements (Semi-major axis, period, eccentricity with corresponding uncertainties), indication of multiplicity and number of solutions, as well as visual magnitudes, spectral classes of the components, parallax and interstellar extinction estimate. Table 2 in the reference paper (on which this HEASARC table is based) contains a refined set of 652 solely binary systems with reliable orbits and determined parallaxes. One entry in this table corresponds to one system. Three mass estimates are provided: (1) The dynamical mass with its uncertainty derived from Kepler's third law and its trigonometric parallax, (2) a photometric mass estimated from the visual magnitudes, parallax and mass-luminosity relation, and (3) a spectroscopic mass based on the mass-spectrum relation introduced by Straizys and Kuriliene (1981, Ap&SS, 80, 353). Also provided for each system are the main orbital elements, the parallax, and the component magnitudes and spectral types. This table was created by the HEASARC in October 2014 based on the list of orbital binaries given in <a href="https://cdsarc.cds.unistra.fr/ftp/cats/J/A+A/546/A69">CDS Catalog J/A+A/546/A69</a> file table2.dat. Note that this table does not include the information on individual orbits which given listed in file table1.dat of this CDS catalog. This is a service provided by NASA HEASARC .
- ID:
- ivo://CDS.VizieR/J/ApJ/771/85
- Title:
- Dynamical masses of z~2 quiescent galaxies
- Short Name:
- J/ApJ/771/85
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Using stellar kinematics measurements, we investigate the growth of massive, quiescent galaxies from z~2 to today. We present X-Shooter spectra from the UV to NIR and dynamical mass measurements of five quiescent massive (>10^11^M_{sun}_) galaxies at z~2. This triples the sample of z>1.5 galaxies with well-constrained ({delta}{sigma}<100km/s) velocity dispersion measurements. From spectral population synthesis modeling we find that these galaxies have stellar ages that range from 0.5 to 2Gyr, with no signs of ongoing star formation. We measure velocity dispersions (290-450km/s) from stellar absorption lines and find that they are 1.6-2.1 times higher than those of galaxies in the Sloan Digital Sky Survey at the same mass. Sizes are measured using GALFIT from Hubble Space Telescope Wide Field Camera 3 H_160_ and UDS K-band images. The dynamical masses correspond well to the spectral energy distribution based stellar masses, with dynamical masses that are ~15% higher.
- ID:
- ivo://CDS.VizieR/J/AZh/89/674
- Title:
- Dynamical parameters of open clusters
- Short Name:
- J/AZh/89/674
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Presented are the estimates of open cluster dynamical parameters: the cluster core density contrast, the stellar velocity dispersions allowing for influence of Galaxy external field and non-stationarity of the cluster, the oscillation periods of the cluster and the cluster core, the amplitudes of oscillations of a cluster virial factor and a radius of the cluster core. All the values were analytically received as a result solution of the gross dynamical equations for spherical and ellipsoidal cluster models.
- ID:
- ivo://CDS.VizieR/J/MNRAS/370/1223
- Title:
- Dynamical properties of 15 nearby galaxy groups
- Short Name:
- J/MNRAS/370/1223
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Here, we present an investigation of the properties of 15 nearby galaxy groups and their constituent galaxies. The groups are selected from the Group Evolution Multiwavelength Study (GEMS) and all have X-ray as well as wide-field neutral hydrogen (HI) observations. Group membership is determined using a friends-of-friends algorithm on the positions and velocities from the 6-degree Field Galaxy Survey and NASA/IPAC Extragalactic Database. For each group we derive their physical properties using this membership, including: velocity dispersions (sigma_v_), virial masses (M_V_), total K-band luminosities [L_K_(Tot)] and early-type fractions (f_early_) and present these data for the individual groups.
- ID:
- ivo://CDS.VizieR/J/AJ/137/4795
- Title:
- Dynamical state of brightest cluster galaxies
- Short Name:
- J/AJ/137/4795
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A large sample of Abell clusters of galaxies, selected for the likely presence of a dominant galaxy, is used to study the dynamical properties of the brightest cluster members (BCMs). From visual inspection of Digitized Sky Survey images combined with redshift information we identify 1426 candidate BCMs located in 1221 different redshift components associated with 1169 different Abell clusters. This is the largest sample published so far of such galaxies. From our own morphological classification we find that ~92% of the BCMs in our sample are early-type galaxies and 48% are of cD type. We confirm what was previously observed based on much smaller samples, namely, that a large fraction of BCMs have significant peculiar velocities. From a subsample of 452 clusters having at least 10 measured radial velocities, we estimate a median BCM peculiar velocity of 32% of their host clusters' radial velocity dispersion. This suggests that most BCMs are not at rest in the potential well of their clusters. This phenomenon is common to galaxy clusters in our sample, and not a special trait of clusters hosting cD galaxies. We show that the peculiar velocity of the BCM is independent of cluster richness and only slightly dependent on the Bautz-Morgan type. We also find a weak trend for the peculiar velocity to rise with the cluster velocity dispersion. The strongest dependence is with the morphological type of the BCM: cD galaxies tend to have lower relative peculiar velocities than elliptical galaxies. This result points to a connection between the formation of the BCMs and that of their clusters. Our data are qualitatively consistent with the merging-groups scenario, where BCMs in clusters formed first in smaller subsystems comparable to compact groups of galaxies. In this scenario, clusters would have formed recently from the mergers of many such groups and would still be in a dynamically unrelaxed state.
- ID:
- ivo://CDS.VizieR/J/PAZh/34/446
- Title:
- Dynamical study of wide pairs of stars from WDS
- Short Name:
- J/PAZh/34/446
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Using the method of apparent motion parameters, we have studied the relative motion of the components in 561 pairs of wide (rho>2") and relatively nearby (Hipparcos parallaxes >0.01") visual double stars based on data from the WDS catalog. The minimum masses of the double stars have been calculated at given parallaxes. We have identified 358 optical pairs. For 11 stellar pairs, we have found the minimum mass to exceed the estimate corresponding to their spectral types and luminosities. This excess is 5-7M_{sun}_ for two stars, ADS7446 and 9701.