- ID:
- ivo://CDS.VizieR/J/ApJ/859/L8
- Title:
- Properties of TriAnd stars
- Short Name:
- J/ApJ/859/L8
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The nature of the Triangulum-Andromeda (TriAnd) system has been debated since the discovery of this distant, low-latitude Milky Way (MW) overdensity more than a decade ago. Explanations for its origin are either as a halo substructure from the disruption of a dwarf galaxy, or a distant extension of the Galactic disk. We test these hypotheses using the chemical abundances of a dozen TriAnd members from the Sloan Digital Sky Survey-IV's (SDSS-IV's) 14th Data Release (DR14) of Apache Point Observatory Galactic Evolution Experiment (APOGEE) data to compare to APOGEE abundances of stars with similar metallicity from both the Sagittarius (Sgr) dSph and the outer MW disk. We find that TriAnd stars are chemically distinct from Sgr across a variety of elements, (C+N), Mg, K, Ca, Mn, and Ni, with a separation in [X/Fe] of about 0.1 to 0.4dex depending on the element. Instead, the TriAnd stars, with a median metallicity of about -0.8, exhibit chemical abundance ratios similar to those of the lowest metallicity ([Fe/H]~-0.7) stars in the outer Galactic disk, and are consistent with expectations of extrapolated chemical gradients in the outer disk of the MW. These results suggest that TriAnd is associated with the MW disk, and, therefore, that the disk extends to this overdensity-i.e., past a Galactocentric radius of 24kpc-albeit vertically perturbed about 7kpc below the nominal disk midplane in this region of the Galaxy.
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Search Results
- ID:
- ivo://CDS.VizieR/J/ApJ/812/34
- Title:
- Properties of UCD candidates in M87/M49/M60 regions
- Short Name:
- J/ApJ/812/34
- Date:
- 14 Jan 2022 08:28:26
- Publisher:
- CDS
- Description:
- We use imaging from the Next Generation Virgo cluster Survey (NGVS) to present a comparative study of ultra-compact dwarf (UCD) galaxies associated with three prominent Virgo sub-clusters: those centered on the massive red-sequence galaxies M87, M49, and M60. We show how UCDs can be selected with high completeness using a combination of half-light radius and location in color-color diagrams (u*iK_s_ or u*gz). Although the central galaxies in each of these sub-clusters have nearly identical luminosities and stellar masses, we find large differences in the sizes of their UCD populations, with M87 containing ~3.5 and 7.8 times more UCDs than M49 and M60, respectively. The relative abundance of UCDs in the three regions scales in proportion to sub-cluster mass, as traced by X-ray gas mass, total gravitating mass, number of globular clusters (GCs), and number of nearby galaxies. We find that the UCDs are predominantly blue in color, with ~85% of the UCDs having colors similar to blue GCs and stellar nuclei of dwarf galaxies. We present evidence that UCDs surrounding M87 and M49 may follow a morphological sequence ordered by the prominence of their outer, low surface brightness envelope, ultimately merging with the sequence of nucleated low-mass galaxies, and that envelope prominence correlates with distance from either galaxy. Our analysis provides evidence that tidal stripping of nucleated galaxies is an important process in the formation of UCDs.
- ID:
- ivo://CDS.VizieR/J/AJ/155/207
- Title:
- Properties of yellow supergiant stars in the SMC
- Short Name:
- J/AJ/155/207
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We recently discovered a yellow supergiant (YSG) in the Small Magellanic Cloud (SMC) with a heliocentric radial velocity of ~300 km/s, which is much larger than expected for a star at its location in the SMC. This is the first runaway YSG ever discovered and only the second evolved runaway star discovered in a galaxy other than the Milky Way. We classify the star as G5-8 I and use de-reddened broad-band colors with model atmospheres to determine an effective temperature of 4700+/-250 K, consistent with what is expected from its spectral type. The star's luminosity is then log L/L_{sun}_~4.2~0.1, consistent with it being a ~30 Myr 9 M_{sun}_ star according to the Geneva evolution models. The star is currently located in the outer portion of the SMC's body, but if the star's transverse peculiar velocity is similar to its peculiar radial velocity, in 10 Myr the star would have moved 1.6{deg} across the disk of the SMC and could easily have been born in one of the SMC's star-forming regions. Based on its large radial velocity, we suggest it originated in a binary system where the primary exploded as a supernovae, thus flinging the runaway star out into space. Such stars may provide an important mechanism for the dispersal of heavier elements in galaxies given the large percentage of massive stars that are runaways. In the future, we hope to look into additional evolved runaway stars that were discovered as part of our other past surveys.
- ID:
- ivo://CDS.VizieR/J/AJ/154/129
- Title:
- PSYM-WIDE: planetary-mass companions to YMG members
- Short Name:
- J/AJ/154/129
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of a direct imaging survey for very large separation (>100 AU), low-mass companions around 95 nearby young K5-L5 stars and brown dwarfs. They are high-likelihood candidates or confirmed members of the young (~<150 Myr) {beta} Pictoris and AB Doradus moving groups (ABDMG) and the TW Hya, Tucana-Horologium, Columba, Carina, and Argus associations. Images in i' and z' filters were obtained with the Gemini Multi-Object Spectrograph (GMOS) on Gemini South to search for companions down to an apparent magnitude of z'~22-24 at separations >~20" from the targets and in the remainder of the wide 5.5'x5.5' GMOS field of view. This allowed us to probe the most distant region where planetary-mass companions could be gravitationally bound to the targets. This region was left largely unstudied by past high-contrast imaging surveys, which probed much closer-in separations. This survey led to the discovery of a planetary-mass (9-13 M_Jup_) companion at 2000 AU from the M3V star GU Psc, a highly probable member of ABDMG. No other substellar companions were identified. These results allowed us to constrain the frequency of distant planetary-mass companions (5-13 M_Jup_) to 0.84_-0.66_^+6.73^% (95% confidence) at semimajor axes between 500 and 5000 AU around young K5-L5 stars and brown dwarfs. This is consistent with other studies suggesting that gravitationally bound planetary-mass companions at wide separations from low-mass stars are relatively rare.
- ID:
- ivo://CDS.VizieR/III/252
- Title:
- Pulkovo radial velocities for 35493 HIP stars
- Short Name:
- III/252
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Pulkovo Compilation of Radial Velocities (PCRV) has been made to study the stellar kinematics in the local spiral arm. The PCRV contains weighted mean absolute radial velocities for 35495 Hipparcos stars of various spectral types and luminosity classes over the entire celestial sphere mainly within 500 pc of the Sun. The median accuracy of the radial velocities obtained is 0.7km/s. Results from 203 publications were used in the catalogue. Four of them were used to improve the radial velocities of standard stars from the IAU list. The radial velocities of 155 standard stars turned out to be constant within 0.3km/s. These stars were used to analyze 47768 mean radial velocities for 37200 stars from 12 major publications (80% of all the data used). Zero-point discrepancies and systematic dependences on radial velocity, B-V color index, right ascension, and declination were found in radial velocity differences of the form "publication minus IAU list of standards". These discrepancies and dependences were approximated and taken into account when calculating the weighted mean radial velocities. 1128 stars whose independent radial-velocity determinations were available at least in three of these publications and agreed within 3km/s were chosen as the work list of secondary standards. Radial-velocity differences of the form "publication minus list of secondary standards" were used by analogy to correct the zero points and systematic dependences in the radial velocities from 33 more publications (13% of the data used). In addition, the radial velocities from 154 minor publications (7% of the data used) pertaining to well-known instruments were used without any corrections. Data are also available at: http://www.geocities.com/orionspiral/
- ID:
- ivo://CDS.VizieR/J/MNRAS/391/1009
- Title:
- Radial kinematics in bright cluster galaxies
- Short Name:
- J/MNRAS/391/1009
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This is the first of a series of papers devoted to the investigation of a large sample of brightest cluster galaxies (BCGs), their kinematic and stellar population properties, and the relationships between those and the properties of the cluster. We have obtained high signal-to-noise ratio, long-slit spectra of these galaxies with Gemini and William Herschel Telescope with the primary purpose of investigating their stellar population properties. This paper describes the selection methods and criteria used to compile a new sample of galaxies, concentrating on BCGs previously classified as containing a halo (cD galaxies), together with the observations and data reduction. Here, we present the full sample of galaxies, and the measurement and interpretation of the radial velocity and velocity dispersion profiles of 41 BCGs.
- ID:
- ivo://CDS.VizieR/J/MNRAS/419/2844
- Title:
- Radial metallicity gradient from RAVE DR3
- Short Name:
- J/MNRAS/419/2844
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We investigate radial metallicity gradients for a sample of dwarf stars from the RAdial Velocity Experiment (RAVE) Data Release 3 (DR3, Cat. III/265). We select a total of approximately 17000 F-type and G-type dwarfs, using a selection of colour, log g and uncertainty in the derived space motion, and calculate for each star a probabilistic (kinematic) population assignment to a thick or thin disc using space motion and additionally another (dynamical) assignment using stellar vertical orbital eccentricity. We additionally subsample by colour, to provide samples biased toward young thin-disc and older thin-disc stars. We derive a metallicity gradient as a function of Galactocentric radial distance, i.e. d[M/H]/dRm=-0.051+/-0.005dex/kpc, for the youngest sample, F-type stars with vertical orbital eccentricities e_v_<=0.04. Samples biased toward older thin-disc stars show systematically shallower abundance gradients.
- ID:
- ivo://CDS.VizieR/J/ApJ/838/83
- Title:
- Radial velocities, abundances & membership in TriII
- Short Name:
- J/ApJ/838/83
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Among the Milky Way satellites discovered in the past three years, Triangulum II has presented the most difficulty in revealing its dynamical status. Kirby+ (2015ApJ...814L...7K) identified it as the most dark-matter-dominated galaxy known, with a mass-to-light ratio within the half-light radius of 3600_-2100_^+3500^M_{sun}_/L_{sun}_. On the other hand, Martin+ (2016ApJ...818...40M) measured an outer velocity dispersion that is 3.5+/-2.1 times larger than the central velocity dispersion, suggesting that the system might not be in equilibrium. From new multi-epoch Keck/DEIMOS measurements of 13 member stars in Triangulum II, we constrain the velocity dispersion to be {sigma}_v_<3.4km/s (90%C.L.). Our previous measurement of {sigma}_v_, based on six stars, was inflated by the presence of a binary star with variable radial velocity. We find no evidence that the velocity dispersion increases with radius. The stars display a wide range of metallicities, indicating that Triangulum II retained supernova ejecta and therefore possesses, or once possessed, a massive dark matter halo. However, the detection of a metallicity dispersion hinges on the membership of the two most metal-rich stars. The stellar mass is lower than galaxies of similar mean stellar metallicity, which might indicate that Triangulum II is either a star cluster or a tidally stripped dwarf galaxy. Detailed abundances of one star show heavily depressed neutron-capture abundances, similar to stars in most other ultra-faint dwarf galaxies but unlike stars in globular clusters.
- ID:
- ivo://CDS.VizieR/III/154
- Title:
- Radial Velocities along Southern Galactic Equator
- Short Name:
- III/154
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This catalog contains a list of radial velocities, obtained from "Grand Prisme Objectif" (GPO) plates from La Silla, for 764 stars in three fields in the Vela-Carina region of the galaxy. The method of reduction is described in Duflot and Fehrenbach (1955) and Duflot et al. (1958).
- ID:
- ivo://CDS.VizieR/J/ApJ/454/788
- Title:
- Radial velocities and BV photometry of NGC 3201
- Short Name:
- J/ApJ/454/788
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- BV CCD frames have been used to derive surface brightness profiles for NGC 3201 which extend out to ~18'. A total of 857 radial velocities with median precision ~1km/s for 399 member giants have been used to trace the velocity dispersion profile out to 32.1' (the approximate tidal radius determined from fits of single-mass, isotropic King-Michie models to the cluster surface brightness profiles). The median difference in radial velocity for stars on either side of an imaginary axis stepped through the cluster in 1 deg increments shows a statistically significant maximum amplitude of 1.22+/-0.25km/s. We discuss several possible explanations of this result, including (1) cluster rotation, (2) preferential stripping of stars on prograde orbits near the limiting radius, (3) the projection of the cluster space velocity onto the plane of the sky, and (4) a slight drift in the velocity zero point. It is difficult to unambiguously identify the primary cause of the observed structure in the velocity field, however, and we suspect that all of the above processes may play a role. The BV surface brightness profiles and radial velocities have been modeled with both single- and multimass King-Michie models and nonparametric techniques. The corresponding density profiles and M/L profiles show good agreement over the interval 1.5<~R<~10pc, and both approaches suggest a steady rise in M/L with distance from the cluster center. Due to the low cluster luminosity we are unable to place useful constraints on the anisotropy of M/L_B~M/L_V~2.0+/-0.2 for the multimass and nonparametric models, compared to ~1.65+/-0.15 for models having equal-mass stars. Our best-fit, multimass models have mass function slopes of x~0.75+/-0.25, consistent with recent findings that the form of the mass function depends on the position relative to the potential of the Galaxy.