There is strong evidence that globular cluster systems (GCSs) of massive galaxies are largely assembled by infall/accretion processes. Therefore, we expect the GCSs of isolated elliptical galaxies to be poor. Although not completely isolated, NGC 7507 is a massive field elliptical galaxy with an apparently very low dark matter content. We determine the richness, the colour distribution, and the structural properties of the GCS of NGC 7507. We performed wide-field Washington photometry with data obtained with the MOSAIC II camera at the 4m-Blanco telescope (CTIO, Chile).
We describe a deep multi-colour NIR survey (TCS-CAIN) that has been recently completed at the Instituto de Astrofisica de Canarias (Spain). The survey is of selected areas distributed along the Galactic plane and it goes deeper than 2MASS or DENIS. Its aim was to explore the large-scale structure of the Milky Way and the Galactic components, in particular the Galactic bar. This survey has about 10 million point-source detections in J, H, and Ks filters with a photometric accuracy of about 0.1mag in the three bands and a positional accuracy of about 0.2" (based on the 2MASS catalogue as the astrometric reference).
The Belgian/UK Ultraviolet Sky Survey Telescope (S2/68) in the ESRO TD1 satellite carried out a controlled scan of the entire sky. It measured the absolute ultraviolet flux distribution between 2740A and 1350A of point sources down to 10th visual magnitude for unreddened early B stars. The S2/68 experiment has been described by Boksenberg et al. (1973MNRAS.163..291B), and the absolute calibration by Humphries et al. (1976A&A....49..389H). The TD1 Catalog of Stellar Ultraviolet Fluxes represents results from the sky-scan experiment on the TD1 satellite of the European Space Research Organization (ESRO), now part of ESA. It lists the absolute fluxes, in four passbands, for 31,215 stars: <pre> Passband Center: 274.0nm 236.5nm 196.5nm 156.5nm Effective Width: 31.0nm 33.0nm 33.0nm 33.0nm </pre> The stars have been selected subject to the constraint that the signal-to-noise ratio should be at least 10.0 in any one of the four passbands. Null values of a flux field and an error field indicate there are no valid data for the star. This usually arises with close pairs of stars whose spectra overlap. Five standard flux error values are greater than 99.99, and were too large for the format of the flux field in the original table. Thus, the flux error values which were greater than 99.99 are given as 99.99. Many of the fainter stars of spectral type later than A5 do not have significant signals in all of the spectrophotometric channels (particularly the 1565A channel). Consequently, after the removal of the background, they can randomly give rise to small negative values of flux. Those negative values were not suppressed, but are given together with their error, as they can be significant when considered as part of a statistical sample. Although the sky coverage is essentially complete, the catalog does not contain the fluxes for all stars that fall within the limit of the sensitivity of the instrument. If any star expected to be present is missing, then its signal is probably blended with that of a nearby star, in which case the data have been discarded. The original contents of the HEASARC's TD1 database table came from a magnetic tape sent to NASA/Goddard Space Flight Center by Dr. G.I. Thompson of the Royal Observatory in Edinburgh, Scotland. The HEASARC recreated this database table in August 2005, based on the <a href="https://cdsarc.cds.unistra.fr/ftp/cats/II/59B">CDS Catalog II/59B</a> file catalog.dat.gz, in an effort to modernize its parameter names and documentation, as well as to add Galactic coordinates. The data in the CDS version originally came from "Selected Astronomical Catalogs" Vol. 1 CD-ROM released by the NASA Astronomical Data Center (ADC) in 1991. This is a service provided by NASA HEASARC .
We report observational techniques, results, and Monte Carlo population analyses from a Spitzer Infrared Array Camera imaging survey for substellar companions to 117 nearby M, L, and T dwarf systems (median distance of 10pc, mass range of 0.6 to ~0.05M_{sun}_). The two-epoch survey achieves typical detection sensitivities to substellar companions of [4.5um]<=17.2mag for angular separations between about 7" and 165". Based on common proper motion analysis, we find no evidence for new substellar companions. Using Monte Carlo orbital simulations (assuming random inclination, random eccentricity, and random longitude of pericenter), we conclude that the observational sensitivities translate to an ability to detect 600-1100K brown dwarf companions at semimajor axes >~35AU and to detect 500-600 K companions at semimajor axes >~60AU. The simulations also estimate a 600-1100K T dwarf companion fraction of <3.4% for 35-1200AU separations and <12.4% for the 500-600K companions for 60-1000AU separations.
We report the discovery of 87 new T dwarfs uncovered with the Wide-field Infrared Survey Explorer (WISE) and 3 brown dwarfs with extremely red near-infrared colors that exhibit characteristics of both L and T dwarfs. Two of the new T dwarfs are likely binaries with L7+/-1 primaries and mid-type T secondaries. In addition, our follow-up program has confirmed 10 previously identified T dwarfs and 4 photometrically selected L and T dwarf candidates in the literature. This sample, along with the previous WISE discoveries, triples the number of known brown dwarfs with spectral types later than T5. Using the WISE All-Sky Source Catalog we present updated color-color and color-type diagrams for all the WISE-discovered T and Y dwarfs. Near-infrared spectra of the new discoveries are presented along with spectral classifications.
We report the discovery of 76 new T dwarfs from the UKIRT Infrared Deep Sky Survey (UKIDSS) Large Area Survey (LAS). Near-infrared broad- and narrow-band photometry and spectroscopy are presented for the new objects, along with Wide-field Infrared Survey Explorer (WISE) and warm-Spitzer photometry. Proper motions for 128 UKIDSS T dwarfs are presented from a new two epoch LAS proper motion catalogue. We use these motions to identify two new benchmark systems: LHS 6176AB, a T8p+M4 pair and HD 118865AB, a T5.5+F8 pair. Using age constraints from the primaries and evolutionary models to constrain the radii, we have estimated their physical properties from their bolometric luminosity. We compare the colours and properties of known benchmark T dwarfs to the latest model atmospheres and draw two principal conclusions. First, it appears that the H-[4.5] and J-W2 colours are more sensitive to metallicity than has previously been recognized, such that differences in metallicity may dominate over differences in Teff when considering relative properties of cool objects using these colours. Secondly, the previously noted apparent dominance of young objects in the late-T dwarf sample is no longer apparent when using the new model grids and the expanded sample of late-T dwarfs and benchmarks. This is supported by the apparently similar distribution of late-T dwarfs and earlier type T dwarfs on reduced proper motion diagrams that we present. Finally, we present updated space densities for the late-T dwarfs, and compare our values to simulation predictions and those from WISE.
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.
We present the Team Keck Redshift Survey 2 (TKRS2), a near-infrared spectral observing program targeting selected galaxies within the CANDELS subsection of the GOODS-North Field. The TKRS2 program exploits the unique capabilities of the Multi-Object Spectrometer For Infra-Red Exploration (MOSFIRE), which entered service on the Keck I telescope in 2012 and contributes substantially to the study of galaxy spectral features at redshifts inaccessible to optical spectrographs. The TKRS2 project targets 97 galaxies drawn from samples that include z~2 emission-line galaxies with features observable in the JHK bands as well as lower-redshift targets with features in the Y band. We present a detailed measurement of MOSFIRE's sensitivity as a function of wavelength, including the effects of telluric features across the YJHK filters. The largest utility of our survey is in providing rest-frame-optical emission lines for z>1 galaxies, and we demonstrate that the ratios of strong, optical emission lines of z~2 galaxies suggest the presence of either higher N/O abundances than are found in z~0 galaxies or low-metallicity gas ionized by an active galactic nucleus. We have released all TKRS2 data products into the public domain to allow researchers access to representative raw and reduced MOSFIRE spectra.
Teegarden's Star is the brightest and one of the nearest ultra-cool dwarfs in the solar neighbourhood. For its late spectral type (M7.0 V), the star shows relatively little activity and is a prime target for near-infrared radial velocity surveys such as CARMENES. As part of the CARMENES search for exoplanets around M dwarfs, we obtained more than 200 radial-velocity measurements of Teegarden's Star and analysed them for planetary signals. We find periodic variability in the radial velocities of Teegarden's Star. We studied photometric measurements to rule out stellar brightness variations mimicking planetary signals. We find evidence for two planet candidates, each with 1.1M_{Earth}_ minimum mass, orbiting at periods of 4.91d and 11.4d, respectively. No evidence for planetary transits could be found in archival and follow-up photometry. Small photometric variability is suggestive of slow rotation and old age. The two planets are among the lowest-mass planets discovered so far, and they are the first Earth-mass planets around an ultra-cool dwarf for which the masses have been determined using radial velocities.
We present empirical metallicity-dependent calibrations of effective temperature against colours for dwarfs of luminosity classes IV and V and for giants of luminosity classes II and III, based on a collection from the literature of about two hundred nearby stars with direct effective temperature measurements of better than 2.5 per cent. The calibrations are valid for an effective temperature range 3100-10000K for dwarfs of spectral types M5 to A0 and 3100-5700K for giants of spectral types K5 to G5. A total of 21 colours for dwarfs and 18 colours for giants of bands of four photometric systems, i.e. the Johnson (UBVR_J_I_J_JHK), the Cousins (R_C_I_C_), the Sloan Digital Sky Survey (gr) and the Two Micron All Sky Survey (JHKs), have been calibrated. Restricted by the metallicity range of the current sample, the calibrations are mainly applicable for disc stars ([Fe/H]>~-1.0). The normalized percentage residuals of the calibrations are typically 2.0 and 1.5 per cent for dwarfs and giants, respectively. Some systematic discrepancies at various levels are found between the current scales and those available in the literature (e.g. those based on the infrared flux method or spectroscopy). Based on the current calibrations, we have re-determined the colours of the Sun. We have also investigated the systematic errors in effective temperatures yielded by the current on-going large-scale low- to intermediate-resolution stellar spectroscopic surveys. We show that the calibration of colour (g-Ks) presented in this work provides an invaluable tool for the estimation of stellar effective temperature for those on-going or upcoming surveys.