- ID:
- ivo://CDS.VizieR/J/A+A/659/A181
- Title:
- J-PLUS DR1 stellar param, and abundances
- Short Name:
- J/A+A/659/A181
- Date:
- 25 Mar 2022 09:03:05
- Publisher:
- CDS
- Description:
- The Javalambre Photometric Local Universe Survey (J-PLUS) has obtained precise photometry in twelve specially designed filters for large numbers of Galactic stars. Deriving their precise stellar atmospheric parameters and individual elemental abundances is crucial for studies of Galactic structure, and the assembly history and chemical evolution of our Galaxy. Our goal is to estimate not only stellar parameters (effective temperature, Teff, surface gravity, logg, and metallicity, [Fe/H]), but also [{alpha}/Fe] and four elemental abundances ([C/Fe], [N/Fe], [Mg/Fe], and [Ca/Fe]) using data from J-PLUS DR1. By combining recalibrated photometric data from J-PLUS DR1, Gaia DR2, and spectroscopic labels from LAMOST, we design and train a set of cost-sensitive neural networks, the CSNet, to learn the non-linear mapping from stellar colors to their labels. We have achieved precisions of {delta}Teff~55K, {delta}logg~0.15dex, and {delta}[Fe/H]~0.07dex, respectively, over a wide range of temperature, surface gravity, and metallicity. The uncertainties of the abundance estimates for [{alpha}/Fe] and the four individual elements are in the range 0.04-0.08 dex. We compare our parameter and abundance estimates with those from other spectroscopic catalogs such as APOGEE and GALAH, and find an overall good agreement. Conclusions. Our results demonstrate the potential of well-designed, high-quality photometric data for determinations of stellar parameters as well as individual elemental abundances. Applying the method to J-PLUS DR1, we have obtained the aforementioned parameters for about two million stars, providing an outstanding data set for chemo-dynamic analyses of the Milky Way.
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Search Results
- ID:
- ivo://CDS.VizieR/J/ApJ/809/143
- Title:
- K-band spectra of stars within central 1pc of the MW
- Short Name:
- J/ApJ/809/143
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a metallicity analysis of 83 late-type giants within the central 1pc of the Milky Way. K-band spectroscopy of these stars was obtained with the medium spectral resolution integral-field spectrograph NIFS on Gemini North using laser-guided star adaptive optics. Using spectral template fitting with the MARCS synthetic spectral grid, we find that there is a large variation in the metallicity, with stars ranging from [M/H]<-1.0 to above solar metallicity. About 6% of the stars have [M/H]<-0.5. This result is in contrast to previous observations with smaller samples that show stars at the Galactic center having approximately solar metallicity with only small variations. Our current measurement uncertainties are dominated by systematics in the model, especially at [M/H]>0, where there are stellar lines not represented in the model. However, the conclusion that there are low-metallicity stars, as well as large variations in metallicity, is robust. The metallicity may be an indicator of the origin of these stars. The low-metallicity population is consistent with that of globular clusters in the Milky Way, but their small fraction likely means that globular cluster infall is not the dominant mechanism for forming the Milky Way nuclear star cluster. The majority of stars are at or above solar metallicity, which suggests they were formed closer to the Galactic center or from the disk. In addition, our results indicate that it will be important for star formation history analyses using red giants at the Galactic center to consider the effect of varying metallicity.
- ID:
- ivo://CDS.VizieR/J/other/RAA/17.76
- Title:
- K giant stars along Sagittarius streams
- Short Name:
- J/other/RAA/17.7
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Large Sky-Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) Data Release 3 provided 341 691 K giant stars with stellar parameters. Based on the models of Law & Majewski (2010ApJ...714..229L), we identified 252 K giant stars in the leading stream associated with the Sagittarius (Sgr) dwarf galaxy. We obtained 132 K giant stars belonging to the trailing arm of Sgr using the model of Belokurov et al. We studied the metallicity distribution of member stars along the streams and found a flat gradient in the first wrap of the leading stream, -(0.88+/-0.3)x10^-3^dex/deg in the second wrap of the leading stream and -(1.2+/-0.3)x10^-3^dex/deg in the first wrap of the trailing stream. Moreover, we obtained a combined metallicity gradient with our sample and data from the literature. We also analyzed the properties of an overdensity, which is located in the leading stream of the Sgr.
- ID:
- ivo://CDS.VizieR/J/other/ApSS/365.112
- Title:
- Kinematic data for high luminosity stars
- Short Name:
- J/other/ApSS/365
- Date:
- 22 Feb 2022
- Publisher:
- CDS
- Description:
- We calculated the median parallaxes for 47 OB associations including at least 10 stars with known Gaia DR2 parallaxes. A comparison between trigonometric and photometric parallaxes of OB associations reveals a zero-point offset of {Delta}_{pi}_=-0.11+/-0.04mas indicating that Gaia DR2 parallaxes are, on average, underestimated and the distances derived from them are overestimated. The correction of {Delta}_{pi}=-0.11 mas is consistent with the estimate that Arenou et al. (2018A&A...616A..17A) obtained for bright stars. An analysis of parallaxes of OB associations and high-luminosity field stars confirms our previous conclusion (Dambis et al., 2001AstL...27...58D) that the distance scale for OB stars established by Blaha and Humphreys (1989AJ.....98.1598B) must be reduced by 10-20%. Spurious systematic motions of 10-20km/s at the distances of 2-3kpc from the Sun are found to arise from the use of the uncorrected Gaia DR2 parallaxes.
- ID:
- ivo://CDS.VizieR/J/MNRAS/472/3887
- Title:
- Kinematic data for stars in OB-associations
- Short Name:
- J/MNRAS/472/3887
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We use stellar proper motions from the catalog TGAS (2016, Cat. I/337) to study the kinematics of OB-associations identified by Blaha and Humphreys (1989AJ.....98.1598B). The TGAS proper motions of OB-associations generally agree well with the Hipparcos proper motions. The parameters of the Galactic rotation curve obtained with TGAS and Hipparcos proper motions agree within the errors. The average internal velocity dispersion calculated for 18 OB-associations with more than 10 TGAS stars is sigma_v_=3.9km/s, which is considerably smaller, by a factor of 0.4, than the velocity dispersions derived from Hipparcos data. The effective contribution from binary OB-stars into the velocity dispersion sigma_v inside OB-associations is sigma_b_=1.2km/s. The median virial and stellar masses of OB-associations are equal to 7.1x10^5^ and 9.0x10^3^M_{sun}_, respectively. Thus OB-associations must be unbound objects provided they do not include a lot of dense gas. The median star-formation efficiency is epsilon=2.1%. Nearly one third of stars of OB-associations must lie outside their tidal radius. We found that the Per OB1 and Car OB1 associations are expanding with the expansion started in a small region of 11-27pc 7-10Myr ago. The average expansion velocity is 6.3km/s.
- ID:
- ivo://CDS.VizieR/J/ApJ/829/108
- Title:
- Kinematic data of Galactic globular clusters
- Short Name:
- J/ApJ/829/108
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present mass and mass profile estimates for the Milky Way (MW) Galaxy using the Bayesian analysis developed by Eadie et al. (2015ApJ...806...54E) and using globular clusters (GCs) as tracers of the Galactic potential. The dark matter and GCs are assumed to follow different spatial distributions; we assume power-law model profiles and use the model distribution functions described in Evans et al. (1997MNRAS.286..315E) and Deason et al. (2012MNRAS.424L..44D). We explore the relationships between assumptions about model parameters and how these assumptions affect mass profile estimates. We also explore how using subsamples of the GC population beyond certain radii affect mass estimates. After exploring the posterior distributions of different parameter assumption scenarios, we conclude that a conservative estimate of the Galaxy's mass within 125kpc is 5.22x10^11^M_{sun}_, with a 50% probability region of (4.79,5.63)x10^11^M_{sun}_. Extrapolating out to the virial radius, we obtain a virial mass for the MW of 6.82x10^11^M_{sun}_ with 50% credible region of (6.06,7.53)x10^11^M_{sun}_ (r_vir_=185_-7_^+7^kpc). If we consider only the GCs beyond 10 kpc, then the virial mass is 9.02(5.69,10.86)x10^11^M_{sun}_ (r_vir_=198_-24_^+19^kpc). We also arrive at an estimate of the velocity anisotropy parameter {beta} of the GC population, which is {beta}=0.28 with a 50% credible region (0.21, 0.35). Interestingly, the mass estimates are sensitive to both the dark matter halo potential and visible matter tracer parameters, but are not very sensitive to the anisotropy parameter.
- ID:
- ivo://CDS.VizieR/J/ApJ/783/131
- Title:
- Kinematic of stars in Galactic center
- Short Name:
- J/ApJ/783/131
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present new kinematic measurements and modeling of a sample of 116 young stars in the central parsec of the Galaxy in order to investigate the properties of the young stellar disk. The measurements were derived from a combination of speckle and laser guide star adaptive optics imaging and integral field spectroscopy from the Keck telescopes. Compared to earlier disk studies, the most important kinematic measurement improvement is in the precision of the accelerations in the plane of the sky, which have a factor of six smaller uncertainties ({sigma}~10{mu}as/yr2). We have also added the first radial velocity measurements for eight young stars, increasing the sample at the largest radii (6''-12'') by 25%. We derive the ensemble properties of the observed stars using Monte Carlo simulations of mock data. There is one highly significant kinematic feature (~20{sigma}), corresponding to the well-known clockwise disk, and no significant feature is detected at the location of the previously claimed counterclockwise disk. The true disk fraction is estimated to be ~20%, a factor of ~2.5 lower than previous claims, suggesting that we may be observing the remnant of what used to be a more densely populated stellar disk. The similarity in the kinematic properties of the B stars and the O/WR stars suggests a common star formation event. The intrinsic eccentricity distribution of the disk stars is unimodal, with an average value of <e> =0.27+/-0.07, which we show can be achieved through dynamical relaxation in an initially circular disk with a moderately top-heavy mass function.
- ID:
- ivo://CDS.VizieR/J/A+A/555/A91
- Title:
- Kinematics of bulge red clump stars
- Short Name:
- J/A+A/555/A91
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Galactic bulge is X-shaped, caused by the two southern arms of the X both crossing the lines of sight, producing a double red clump (one bright and one faint) in the color magnitude diagram. In this paper the authors measure the radial velocities and proper motions for a sample of 454 individual bulge giant stars, roughly equally distributed between the two red clumps to determine how such a structure could be formed from bar instabilities. The radial velocity distribution of stars in the bright red clump, which traces the closer overdensity of bulge stars, shows an excess of stars moving towards the Sun. Similarly, an excess of stars receding from the Sun is seen in the more distant overdensity, which is traced by faint red clump stars. This can be explained by the presence of stars on elongated orbits, which are most likely streaming along the arms of the X-shaped bulge. Proper motions for these stars are consistent with qualitative predictions of dynamical models of peanut-shaped bulges. Surprisingly, stars on elongated orbits have preferentially metal-poor (subsolar) metallicities, while the metal rich ones, in both overdensities, are preferentially found in more axisymmetric orbits.
- ID:
- ivo://CDS.VizieR/J/MNRAS/421/3362
- Title:
- Kinematics of galactic red clump stars
- Short Name:
- J/MNRAS/421/3362
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We investigate radial and vertical metallicity gradients for a sample of red clump stars from the RAdial Velocity Experiment (RAVE) Data Release 3. We select a total of 6781 stars, using a selection of colour, surface gravity and uncertainty in the derived space motion, and calculate for each star a probabilistic (kinematic) population assignment to a thin or thick disc using space motion and additionally another (dynamical) assignment using stellar vertical orbital eccentricity.
- ID:
- ivo://CDS.VizieR/J/A+A/542/A101
- Title:
- LABOCA 870um mapping of 4 Galactic plane fields
- Short Name:
- J/A+A/542/A101
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Imaging surveys of dust emission at (sub)millimetre wavelengths provide a powerful tool for studying molecular clouds and the early stages of star formation. Through submm dust continuum mapping, we attempt to search for genuine infrared-dark clouds (IRDCs) and precursors to massive stars and stellar clusters in the Galactic plane, and to determine their basic physical properties. We have mapped four selected fields of about 0.5degx0.5deg that contain Spitzer 8-um dark regions with LABOCA at 870um. Selected positions in the fields were observed in C^17^O(2-1) to obtain kinematic information. The obtained LABOCA maps are used in conjunction with the Spitzer IR images.
