- ID:
- ivo://CDS.VizieR/J/AJ/126/2421
- Title:
- 2MASS-Selected sample of ultracool dwarfs
- Short Name:
- J/AJ/126/2421
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the initial results of our effort to create a statistically robust, volume-limited sample of ultracool dwarfs from the Two Micron All Sky Survey Second Incremental Data Release (<II/241>). We are engaged in a multifaceted search for nearby late-type objects, and this is the first installment of our search using purely photometric selection. The goal of this work is a determination of the low-mass star and brown dwarf luminosity function in the infrared. Here we outline the construction of the sample, dubbed 2MU2, and present our first results, including the discovery of 186 M7-L6 dwarfs, 47 of which are likely to be within 20pc of the Sun. These results represent 66% of the ultracool candidates in our sample yet constitute a 127% increase in the number of ultracool dwarfs known within the volume searched (covering 40% of the sky out to 20pc). In addition, we have identified 10 M4-M6.5 objects that are likely to be within 20pc (or within 1{sigma}). Finally, based on these initial data, we present a preliminary luminosity function and discuss several interesting features of the partial sample presented here. Once our sample is complete, we will use our measured luminosity function to constrain the mass function of low-mass stars and brown dwarfs.
Number of results to display per page
Search Results
- ID:
- ivo://CDS.VizieR/J/ApJ/662/413
- Title:
- 2MASS survey of wide multiplicity in 3 associations
- Short Name:
- J/ApJ/662/413
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of a search for wide binary systems among 783 members of three nearby young associations: Taurus-Auriga, Chamaeleon I, and two subgroups of Upper Scorpius. Near-infrared (JHK) imagery from 2MASS was analyzed to search for wide (1"-30"; ~150-4500AU) companions to known association members, using color-magnitude cuts to reject likely background stars. We identify a total of 131 candidate binary companions with colors consistent with physical association, of which 39 have not been identified previously in the literature.
- ID:
- ivo://CDS.VizieR/J/ApJ/756/74
- Title:
- 2MASS view of Sgr dSph. VII. Kinematics
- Short Name:
- J/ApJ/756/74
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have assembled a large-area spectroscopic survey of giant stars in the Sagittarius (Sgr) dwarf galaxy core. Using medium resolution (R~15000), multifiber spectroscopy we have measured velocities of these stars, which extend up to 12{deg} from the galaxy's center (3.7 core radii or 0.4 times the King limiting radius). From these high-quality spectra we identify 1310 Sgr members out of 2296 stars surveyed, distributed across 24 different fields across the Sgr core. Additional slit spectra were obtained of stars bridging from the Sgr core to its trailing tail. Our systematic, large-area sample shows no evidence for significant rotation, a result at odds with the ~20km/s rotation required as an explanation for the bifurcation seen in the Sgr tidal stream; the observed small (<=4km/s) velocity trend primarily along the major axis is consistent with models of the projected motion of an extended body on the sky with no need for intrinsic rotation. The Sgr core is found to have a flat velocity dispersion (except for a kinematically colder center point) across its surveyed extent and into its tidal tails, a property that matches the velocity dispersion profiles measured for other Milky Way dwarf spheroidal (dSph) galaxies. We comment on the possible significance of this observed kinematical similarity for the dynamical state of the other classical Milky Way dSphs in light of the fact that Sgr is clearly a strongly tidally disrupted system.
- ID:
- ivo://CDS.VizieR/II/281
- Title:
- 2MASS 6X Point Source Working Database / Catalog
- Short Name:
- II/281
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A special set of observations that utilized exposure times six times longer than the main 2MASS survey measurements were conducted in the final year of 2MASS observatory operations. The 2MASS "6x" observations achieved sensitivities ~1 mag deeper than the main 2MASS survey, and covered approximately 590 deg2 of sky in 30 discrete regions. The 2MASS 6x Point Source Working Databases (6x-PSWDB and 6x-XSWDB) contain all detections extracted from the raw 6x imaging data during pipeline data reduction. The 6x WDB entries include reliable detections of astrophysical sources, as well as spurious detections of noise excursions, image artifacts and transient events such as meteor trails, cosmic rays and hot pixels. In addition, the WDBs may contain multiple, independent detections of objects scanned more than once during the 6x observations. The 2MASS 6x Point Source Catalogs (6x-PSC and 6x-XSC) is a subset of extractions in the 6x-PSWDB that have been identified to be high reliability source detections, with only one measurement of sources detected multiple times for uniformity.
- ID:
- ivo://CDS.VizieR/J/AJ/125/2521
- Title:
- 2MASS6x survey of the Lockman Hole
- Short Name:
- J/AJ/125/2521
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have carried out a survey of the Lockman Hole covering over 24deg^2^ using the Two Micron All Sky Survey (2MASS) observing system in a special mode that reaches roughly 1mag deeper than the nominal 2MASS survey. The resultant point-source catalog reaches to approximately (J, H, Ks)<(17.8, 16.5, 16.0)mag with completeness and reliability in excess of 90%-95% at the faintest levels. These data will be useful in identifying sources in SIRTF surveys of this area. We have cataloged 69,115 objects, almost twice as many as in the nominal 2MASS survey of this region. The sample includes a large number of potential new active galaxies, as well as a T dwarf candidate.
- ID:
- ivo://CDS.VizieR/IV/33
- Title:
- Master Catalogue towards the Magellanic Clouds (MC2)
- Short Name:
- IV/33
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Master Catalogue of stars towards the Magellanic Clouds (MC2) is a multi-wavelength reference catalogue. The current paper presents the first results of the MC2 project. We started with a massive cross-identification of the two recently released near-infrared surveys: the DENIS Catalogue towards the Magellanic Clouds (DCMC) with more than 1.3 million sources identified in at least two of the three DENIS filters (I J Ks) and the 2nd Incremental Release of the 2MASS point source catalogue (J H Ks) covering the same region of the sky. Both point source catalogues provide an unprecedented wealth of data on the stellar populations of the Magellanic Clouds (MCs). The cross-matching procedure has been extended to optical wavelength ranges, including the UCAC1 (USNO) and GSC2.2 catalogues. New cross-matching procedures for very large catalogues have been developed and important results on the astrometric and photometric accuracy of the cross-identified catalogues were derived. The cross-matching of large surveys is an essential tool to improve our understanding of their specific contents. This study has been partly supported by the ASTROVIRTEL project that aims at improving access to astronomical archives as virtual telescopes. This work has been supported by ASTROVIRTEL, a project funded by the European Commission under FP5 Contract No. HPRI-CT-1999-00081.
- ID:
- ivo://CDS.VizieR/J/ApJ/872/148
- Title:
- 2MASX/NVSS galaxies brighter than K_20fe_=12.25
- Short Name:
- J/ApJ/872/148
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We identified 15658 NRAO VLA Sky Survey (NVSS) radio sources among the 55288 2 Micron All-Sky Survey eXtended (2MASX) galaxies brighter than k_20fe_=12.25 at {lambda}=2.16{mu}m and covering the {Omega}=7.016sr of sky defined by J2000 {delta}>-40{deg} and |b|>20{deg}. The complete sample of 15043 galaxies with 1.4GHz flux densities S>=2.45mJy contains a 99.9% spectroscopically complete subsample of 9517 galaxies with k_20fe_<=11.75. We used only radio and infrared data to quantitatively distinguish radio sources powered primarily by recent star formation from those powered by active galactic nuclei. The radio sources with log[L(W/Hz)]>19.3 that we used to derive the local spectral luminosity and power-density functions account for >99% of the total 1.4GHz spectral power densities U_SF_=(1.54+/-0.20)x10^19^W/Hz/Mpc^3^ and U_AGN_=(4.23+/-0.78)x10^19^W/Hz/Mpc^3^ in the universe today, and the spectroscopic subsample is large enough that the quoted errors are dominated by cosmic variance. The recent comoving star formation rate density indicated by USF is {psi}~0.015M_{sun}_/yr/Mpc^3^.
1728. M 4 CCD photometry
- ID:
- ivo://CDS.VizieR/J/AJ/114/189
- Title:
- M 4 CCD photometry
- Short Name:
- J/AJ/114/189
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- With the ESO NTT, we have obtained accurate CCD UBVI photometry of 1649 stars in an extended field in the globular cluster M 4 = NGC 6121. The position of the main-sequence turnoff is found to be at V_TO_=17.0+/-0.1mag, (B-V)=0.863+/-0.007, (V-I)=1.224+/-0.010, (B-I)=2.084+/-0.010. Our turnoff point is redder and fainter than those found for M 4 in the majority of recent studies, probably because of our field being located in the western, most reddened part of the cluster. The spread of stars around the main-sequence locus has an unusual shape (broadening near the turnoff point and close to the photometric limit), earlier noticed by Richer et al. (1995ApJ...451L..17R) and attributed by them to photometric effects. We have analyzed the possible reasons for this effect and concluded that, at least in our case, it is most probably due to differential absorption. We confirm the deviation of theoretical isochrones from the fainter parts of the M 4 main-sequence locus found by Alcaino et al. (1988ApJ...330..569A). Several curious structural details (a depression and an excess of stars) have been revealed in the brighter parts of the main-sequence luminosity function of M 4.
- ID:
- ivo://CDS.VizieR/J/AJ/145/106
- Title:
- M31 Cepheid disk sample of 1st year of PS1
- Short Name:
- J/AJ/145/106
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a sample of Cepheid variable stars towards M31 based on the first year of regular M31 observations of the PS1 survey in the r_P1 and i_P1 filters. We describe the selection procedure for Cepheid variable stars from the overall variable source sample and develop an automatic classification scheme using Fourier decomposition and the location of the instability strip. We find 1440 fundamental mode (classical {delta}) Cep stars, 126 Cepheids in the first overtone mode, and 147 belonging to the Population II types. 296 Cepheids could not be assigned to one of these classes and 354 Cepheids were found in other surveys. These 2009 Cepheids constitute the largest Cepheid sample in M31 known so far and the full catalog is presented in this paper. We briefly describe the properties of our sample in its spatial distribution throughout the M31 galaxy, in its age properties, and we derive an apparent period-luminosity relation (PLR) in our two bands. The Population I Cepheids nicely follow the dust pattern of the M31 disk, whereas the 147 Type II Cepheids are distributed throughout the halo of M31. We outline the time evolution of the star formation in the major ring found previously and find an age gradient. A comparison of our PLR to previous results indicates a curvature term in the PLR.
1730. MDFC Version 10
- ID:
- ivo://CDS.VizieR/II/361
- Title:
- MDFC Version 10
- Short Name:
- II/361
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the Mid-infrared stellar Diameters and Fluxes compilation Catalogue (MDFC) dedicated to long-baseline interferometry at mid-infrared wavelengths (3-13um). It gathers data for half a million stars, i.e. nearly all the stars of the Hipparcos-Tycho catalogue whose spectral type is reported in the SIMBAD data base. We cross-match 26 data bases to provide basic information, binarity elements, angular diameter, magnitude and flux in the near and mid-infrared, as well as flags that allow us to identify the potential calibrators. The catalogue covers the entire sky with 465857 stars, mainly dwarfs and giants from B to M spectral types closer than 18kpc. The smallest reported values reach 0.16uJy in L and 0.1uJy in N for the flux, and 2-microarcsec for the angular diameter. We build four lists of calibrator candidates for the L and Nbands suitable with the Very Large Telescope Interferometer (VLTI) sub- and main arrays using the MATISSE instrument. We identify 1621 candidates for L and 44 candidates for N with the Auxiliary Telescopes (ATs), 375 candidates for both bands with the ATs, and 259 candidates for both bands with the Unit Telescopes (UTs). Predominantly cool giants, these sources are small and bright enough to belong to the primary lists of calibrator candidates. In the near future, we plan to measure their angular diameter with 1 per cent accuracy.
