- ID:
- ivo://CDS.VizieR/J/AJ/126/2487
- Title:
- T dwarfs in the southern hemisphere
- Short Name:
- J/AJ/126/2487
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the discovery of three new southern hemisphere T dwarfs identified in the Two Micron All Sky Survey (Cat. <II/246>). These objects, 2MASS 0348-6022, 2MASS 0516-0445, and 2MASS 2228-4310, have classifications T7, T5.5, and T6.5, respectively. Using linear absolute magnitude/spectral type relations derived from T dwarfs with measured parallaxes, we estimate spectrophotometric distances for these discoveries; the closest, 2MASS 0348-6022, is likely within 10pc of the Sun. Proper motions and estimated tangential velocities are consistent with membership in the Galactic disk population. We also list southern hemisphere T dwarf candidates that were either not found in subsequent near-infrared imaging observations and are most likely uncataloged minor planets, or have near-infrared spectra consistent with background stars.
Number of results to display per page
Search Results
- ID:
- ivo://CDS.VizieR/J/ApJ/892/31
- Title:
- Teff and metallicities of M dwarfs in APOGEE DR14
- Short Name:
- J/ApJ/892/31
- Date:
- 07 Mar 2022 13:23:27
- Publisher:
- CDS
- Description:
- M dwarfs have enormous potential for our understanding of structure and formation on both Galactic and exoplanetary scales through their properties and compositions. However, current atmosphere models have limited ability to reproduce spectral features in stars at the coolest temperatures (Teff<4200K) and to fully exploit the information content of current and upcoming large-scale spectroscopic surveys. Here we present a catalog of spectroscopic temperatures, metallicities, and spectral types for 5875 M dwarfs in the Apache Point Observatory Galactic Evolution Experiment (APOGEE) and Gaia-DR2 surveys using The Cannon (Ness+ 2015, J/ApJ/808/16 ; Casey+ 2016, arXiv:1603.03040; Ho+ 2017, J/ApJ/836/5; Behmard+ 2019ApJ...876...68B): a flexible, data-driven spectral-modeling and parameter-inference framework demonstrated to estimate stellar-parameter labels (Teff, logg, [Fe/H], and detailed abundances) to high precision. Using a training sample of 87 M dwarfs with optically derived labels spanning 2860K<Teff<4130K calibrated with bolometric temperatures, and -0.5<[Fe/H]<0.5dex calibrated with FGK binary metallicities, we train a two-parameter model with predictive accuracy (in cross-validation) to 77K and 0.09dex respectively. We also train a one-dimensional spectral classification model using 51 M dwarfs with Sloan Digital Sky Survey optical spectral types ranging from M0 to M6, to predictive accuracy of 0.7 types. We find Cannon temperatures to be in agreement to within 60 K compared to a subsample of 1702 sources with color-derived temperatures, and Cannon metallicities to be in agreement to within 0.08 dex metallicity compared to a subsample of 15 FGK+M or M+M binaries. Finally, our comparison between Cannon and APOGEE pipeline (ASPCAP DR14) labels finds that ASPCAP is systematically biased toward reporting higher temperatures and lower metallicities for M dwarfs.
- ID:
- ivo://CDS.VizieR/J/ApJ/851/26
- Title:
- Teff, metallicity and Ti abundance of M dwarfs
- Short Name:
- J/ApJ/851/26
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The ability to perform detailed chemical analysis of Sun-like F-, G-, and K-type stars is a powerful tool with many applications, including studying the chemical evolution of the Galaxy and constraining planet formation theories. Unfortunately, complications in modeling cooler stellar atmospheres hinders similar analyses of M dwarf stars. Empirically calibrated methods to measure M dwarf metallicity from moderate-resolution spectra are currently limited to measuring overall metallicity and rely on astrophysical abundance correlations in stellar populations. We present a new, empirical calibration of synthetic M dwarf spectra that can be used to infer effective temperature, Fe abundance, and Ti abundance. We obtained high-resolution (R~25000), Y-band (~1{mu}m) spectra of 29 M dwarfs with NIRSPEC on Keck II. Using the PHOENIX stellar atmosphere modeling code (version 15.5), we generated a grid of synthetic spectra covering a range of temperatures, metallicities, and alpha-enhancements. From our observed and synthetic spectra, we measured the equivalent widths of multiple Fe I and Ti I lines and a temperature-sensitive index based on the FeH band head. We used abundances measured from widely separated solar-type companions to empirically calibrate transformations to the observed indices and equivalent widths that force agreement with the models. Our calibration achieves precisions in Teff, [Fe/H], and [Ti/Fe] of 60K, 0.1dex, and 0.05dex, respectively, and is calibrated for 3200K<Teff<4100K, -0.7<[Fe/H]<+0.3, and -0.05<[Ti/Fe]<+0.3. This work is a step toward detailed chemical analysis of M dwarfs at a precision similar to what has been achieved for FGK stars.
- ID:
- ivo://CDS.VizieR/J/ApJS/244/25
- Title:
- The BAaDE SiO maser survey at 86GHz with ALMA
- Short Name:
- J/ApJS/244/25
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report on the first 1432 sources observed using the Atacama Large Millimeter/submillimeter Array, from the Bulge Asymmetries and Dynamical Evolution survey, which aims to obtain tens of thousands of line-of-sight velocities from SiO masers in Asymptotic Giant Branch (AGB) stars in the Milky Way. A 71% detection rate of 86GHz SiO masers is obtained from the infrared color-selected sample and increases to 80% when considering the likely oxygen-rich stars using Midcourse Space Experiment colors isolated in a region where [D]-[E]<=1.38. Based on Galactic distributions, the presence of extended CS emission, and likely kinematic associations, the population of sources with [D]-[E]>1.38 probably consists of young stellar objects, or alternatively, of planetary nebulae. For the SiO detections, we examined whether individual SiO transitions provide comparable stellar line-of-sight velocities and found that any SiO transition is suitable for determining a stellar AGB line-of-sight velocity. Finally, we discuss the relative SiO detection rates and line strengths in the context of current pumping models.
- ID:
- ivo://CDS.VizieR/II/363
- Title:
- The band-merged unWISE Catalog
- Short Name:
- II/363
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the unWISE Catalog, containing the positions and fluxes of roughly 2 billion objects observed by the Wide-field Infrared Survey Explorer (WISE) over the full sky. The unWISE Catalog has two advantages over the existing WISE catalog (AllWISE): first, it is based on significantly deeper imaging, and second, it features improved modeling of crowded regions. The deeper imaging used in the unWISE Catalog comes from the coaddition of all publicly available 3-5um WISE imaging, including that from the ongoing NEOWISE-reactivation mission, thereby increasing the total exposure time by a factor of 5 relative to AllWISE. At these depths, even at high Galactic latitudes, many sources are blended with their neighbors; accordingly, the unWISE analysis simultaneously fits thousands of sources to obtain accurate photometry. Our new catalog detects sources roughly 0.7mag fainter than the AllWISE catalog at 5{sigma}, and more accurately models millions of faint sources in the Galactic plane, enabling a wealth of Galactic and extragalactic science. In particular, relative to AllWISE, unWISE doubles the number of galaxies detected between redshifts 0 and 1 and triples the number between redshifts 1 and 2, cataloging more than half a billion galaxies over the whole sky.
- ID:
- ivo://CDS.VizieR/J/ApJ/808/16
- Title:
- The Cannon: a new approach to determine abundances
- Short Name:
- J/ApJ/808/16
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- New spectroscopic surveys offer the promise of stellar parameters and abundances ("stellar labels") for hundreds of thousands of stars; this poses a formidable spectral modeling challenge. In many cases, there is a subset of reference objects for which the stellar labels are known with high(er) fidelity. We take advantage of this with The Cannon, a new data-driven approach for determining stellar labels from spectroscopic data. The Cannon learns from the "known" labels of reference stars how the continuum-normalized spectra depend on these labels by fitting a flexible model at each wavelength; then, The Cannon uses this model to derive labels for the remaining survey stars. We illustrate The Cannon by training the model on only 542 stars in 19 clusters as reference objects, with Teff, logg, and [Fe/H] as the labels, and then applying it to the spectra of 55000 stars from APOGEE DR10. The Cannon is very accurate. Its stellar labels compare well to the stars for which APOGEE pipeline (ASPCAP) labels are provided in DR10, with rms differences that are basically identical to the stated ASPCAP uncertainties. Beyond the reference labels, The Cannon makes no use of stellar models nor any line-list, but needs a set of reference objects that span label-space. The Cannon performs well at lower signal-to-noise, as it delivers comparably good labels even at one-ninth the APOGEE observing time. We discuss the limitations of The Cannon and its future potential, particularly, to bring different spectroscopic surveys onto a consistent scale of stellar labels.
- ID:
- ivo://CDS.VizieR/J/ApJ/823/114
- Title:
- The Cannon: a new approach to determine masses
- Short Name:
- J/ApJ/823/114
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The mass of a star is arguably its most fundamental parameter. For red giant stars, tracers luminous enough to be observed across the Galaxy, mass implies a stellar evolution age. It has proven to be extremely difficult to infer ages and masses directly from red giant spectra using existing methods. From the Kepler and APOGEE surveys, samples of several thousand stars exist with high-quality spectra and asteroseismic masses. Here we show that from these data we can build a data-driven spectral model using The Cannon, which can determine stellar masses to ~0.07dex from APOGEE DR12 spectra of red giants; these imply age estimates accurate to ~0.2dex (40%). We show that The Cannon constrains these ages foremost from spectral regions with CN absorption lines, elements whose surface abundances reflect mass-dependent dredge-up. We deliver an unprecedented catalog of 70000 giants (including 20000 red clump stars) with mass and age estimates, spanning the entire disk (from the Galactic center to R~20kpc). We show that the age information in the spectra is not simply a corollary of the birth-material abundances [Fe/H] and [{alpha}/Fe], and that, even within a monoabundance population of stars, there are age variations that vary sensibly with Galactic position. Such stellar age constraints across the Milky Way open up new avenues in Galactic archeology.
- ID:
- ivo://CDS.VizieR/II/365
- Title:
- The CatWISE2020 catalog (updated version 28-Jan-2021)
- Short Name:
- II/365
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The CatWISE2020 Catalog consists of 1,890,715,640 sources over the entire sky selected from WISE and NEOWISE survey data at 3.4 and 4.6um (W1 and W2) collected from 2010 Jan 7 to 2018 Dec 13. This dataset adds two years to that used for the CatWISE Preliminary Catalog (Eisenhardt+ 2020ApJS..247...69E), bringing the total to six times as many exposures spanning over sixteen times as large a time baseline as the AllWISE catalog. The other major change from the CatWISE Preliminary Catalog is that the detection list for CatWISE2020 was generated using "crowdsource" software (Schlafly+ 2019ApJS..240...30S), while the Preliminary Catalog used the detection software used for AllWISE (II/328). These two factors result in roughly twice as many sources in CatWISE2020. The scatter with respect to Spitzer photometry at faint magnitudes in the COSMOS field, which is out of the Galactic plane and at low ecliptic latitude (corresponding to lower WISE coverage depth) is similar to that for the CatWISE Preliminary Catalog. The 90% completeness depth for CatWISE2020 is at roughly W1=17.7 and W2=17.5, about 1.7 mag deeper than in the Preliminary Catalog. From comparison to Gaia, CatWISE2020 motions are over a dozen times more accurate than those from AllWISE.
- ID:
- ivo://CDS.VizieR/J/ApJ/884/66
- Title:
- The CGM-GRB study. I. GRB hosts at z~2-6
- Short Name:
- J/ApJ/884/66
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Recent studies have revealed a dynamic interplay between the galaxy ecosystem and circumgalactic medium (CGM). We investigate the CGM at high redshifts (z>~2) by using bright afterglows of gamma-ray bursts (GRBs) as background sources. We compiled a sample of medium-resolution ({Delta}v<50km/s) and high signal-to-noise ratio (typical S/N~10) spectra from 27 GRB afterglows covering z~2-6, with six of them at z>~4. We analyzed the high- and low-ionization absorption features within +/-400km/s to extract the CGM and interstellar medium (ISM) kinematics. In the stacked spectra, high-ionization absorption profiles (e.g., CIV, SiIV) present significant absorption excess in their blue wings (v{<}-100km/s) relative to the red wings (v>100km/s). The stronger blue wings in high-ionization species are indicative of the presence of ubiquitous warm outflows in the GRB hosts at high redshifts. We used simple toy models to kinematically distinguish the CGM and ISM absorption and estimate the CGM mass and outflow velocity. We find tentative evidence of the evolution of the CGM metal mass by ~0.5dex between two redshift bins, each spanning 1 Gyr, z1: 2-2.7 and z2: 2.7-5. By comparing with past studies, we find that over the course of evolution of present-day galaxies with M_*_>10^10^M_{sun}_, the ratio of CIV mass in the CGM to the stellar mass remains fairly uniform, with log(M_CIV_/M_*_)~-4.5 within +/-0.5dex from z~4 to z~0, suggesting CGM-galaxy coevolution.
920. The DENIS database
- ID:
- ivo://CDS.VizieR/B/denis
- Title:
- The DENIS database
- Short Name:
- B/denis
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This catalogue is the latest incremental release of the DENIS project. It consists of a set of 355,220,325 point sources detected by the DENIS survey in 3662 strips (covering each 30 degrees in declination and 12 arcmin in right ascension). The data in this release cover approximately 16700 square degrees of the Southern sky. Multiple detections of single point sources have been merged in image overlaps within individual strips, but sources can have multiple detections in overlaping strips. DENIS is the only astronomical survey of the Southern sky made in two near-infrared bands (J at 1.25{mu}m, and K_s_ at 2.15{mu}m) and one optical band (Gunn-i at 0.82{mu}m), with limiting magnitudes 16.5, 14 and 18.5, respectively. Saturation magnitudes are K_s_=6, J=7.5 and Gunn-i=9.8mag. It was conducted by a European consortium, using the 1m telescope at ESO, La Silla (Chile). The DENIS instrument is made up of a 3-channel camera built of commercially available detector arrays by the Observatoire de Paris and with major contributions from other European Institutes, notably: the IAS in Frascati, the Observatoire de Grenoble, the University of Innsbruck, the Observatoire de Lyon, and the IAC in Tenerife. The survey is carried out by observing strips of 30{deg} in declination and 12arcminutes in Right Ascension with an overlap of 2 arcminutes between consecutive strips. The survey started at the end of 1995 and has been completed up to 97% in 2001. The data have been reduced at the Institut d'Astrophysique de Paris and Observatoire de Paris. The position of a general extracted point source is provided with an accuracy better than 1arcsec and its magnitude to better than 0.1 mag. The Centre de Donnees Astronomiques de Strasbourg (CDS) is releasing the final databases and provides access of the processed and calibrated data to the worldwide community. The principal investigator of the DENIS project is N. Epchtein (Observatoire de la Cote d'Azur); the Co-PI in charge of data processing is G. Simon (observatoire de Paris); J. Borsenberger and B. de Batz, with the help of F. Tanguy, S. Begon and P. Texier, processed the data and implemented the working data base at PDAC; S. Derriere is in charge of the data release at CDS. Scientists and engineers from seven European countries and from Brazil are involved in the data qualification and analysis.
