- ID:
- ivo://CDS.VizieR/J/A+AS/135/133
- Title:
- First DENIS I-band extragalactic catalog
- Short Name:
- J/A+AS/135/133
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- REDCAT is the release of the provisional extragalactic catalogue constructed from the "Deep Near Infrared Southern Sky Survey" (DENIS). This catalogue contains 20260 galaxies with coordinates and I-band photometry (magnitude, diameter, axis ratio, position angle and a parameter related to the morphological type). In this new version photometric parameters are homogeneized to I-band measurements by Mathewson and Ford (1997, Cat. <J/ApJS/107/97>). Additional information on galaxies cross-identified with known objects can be obtained through the LEDA database at: http://www-obs.univ-lyon1.fr/leda/leda-consult.html This catalogue is the result of a tremendous work done along the chain Chile-Paris-Lyon. Many people are involved in this programm conducted by the P.I. N. Epchtein. We will not take the risk to mention them all. Their names will appear in forthcoming papers. The distribution on the sky is made of strips of 30 degrees in declination (180 frames per strip) south of +02{deg}. If you are satisfied with this catalogue, try to push the Community to support the DENIS project. Your suggestions are welcome for any improvement of this first release.
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- ID:
- ivo://CDS.VizieR/J/ApJ/757/51
- Title:
- FIRST-2MASS dust-reddened QSO spectra
- Short Name:
- J/ApJ/757/51
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a sample of 120 dust-reddened quasars identified by matching radio sources detected at 1.4GHz in the Faint Images of the Radio Sky at Twenty Centimeters survey (FIRST) with the near-infrared Two Micron All Sky Survey catalog (2MASS) and color-selecting red sources. Optical and/or near-infrared spectroscopy provide broad wavelength sampling of their spectral energy distributions that we use to determine their reddening, characterized by E(B-V). We demonstrate that the reddening in these quasars is best described by Small-Magellanic-Cloud-like dust. This sample spans a wide range in redshift and reddening (0.1<~z<~3, 0.1<~E(B-V)<~1.5), which we use to investigate the possible correlation of luminosity with reddening. At every redshift, dust-reddened quasars are intrinsically the most luminous quasars. We interpret this result in the context of merger-driven quasar/galaxy co-evolution where these reddened quasars are revealing an emergent phase during which the heavily obscured quasar is shedding its cocoon of dust prior to becoming a "normal" blue quasar. When correcting for extinction, we find that, depending on how the parent population is defined, these red quasars make up <~15%-20% of the luminous quasar population. We estimate, based on the fraction of objects in this phase, that its duration is 15%-20% as long as the unobscured, blue quasar phase.
- ID:
- ivo://CDS.VizieR/J/ApJ/607/60
- Title:
- FIRST-2MASS faint sources
- Short Name:
- J/ApJ/607/60
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have constructed a sample of bright near-infrared sources that are detected at radio wavelengths but undetected on the first-generation Palomar Observatory Sky Survey (POSSI) plates in order to search for a population of dust-obscured quasars. Optical and infrared spectroscopic follow-up of the sample has led to the discovery of 17 heavily reddened quasars (B-K>6.5), 14 of which are reported here for the first time. This has allowed us to define a region in the R-K, J-K color plane in which 50% of the radio-selected objects are highly reddened quasars. We compare the surface density of this previously overlooked population to that of ultraviolet-excess radio-selected quasars, finding that they make up ~20% of the total quasar population for K<~15.5.
- ID:
- ivo://CDS.VizieR/J/ApJ/883/175
- Title:
- First release of the MaNGA Stellar Library (MaStar)
- Short Name:
- J/ApJ/883/175
- Date:
- 29 Nov 2021 07:46:33
- Publisher:
- CDS
- Description:
- We present the first release of the MaNGA Stellar Library (MaStar), which is a large, well-calibrated, high-quality empirical library covering the wavelength range 3622-10354{AA} at a resolving power of R~1800. The spectra were obtained using the same instrument as used by the Mapping Nearby Galaxies at Apache Point Observatory (MaNGA) project, by piggybacking on the Sloan Digital Sky Survey (SDSS-IV)/Apache Point Observatory Galaxy Evolution Experiment 2-N (APOGEE-2N) observations. Compared to previous empirical libraries, the MaStar library will have a higher number of stars and a more comprehensive stellar-parameter coverage, especially of cool dwarfs, low-metallicity stars, and stars with different [{alpha}/Fe], achieved by a sophisticated target-selection strategy that takes advantage of stellar-parameter catalogs from the literature. This empirical library will provide a new basis for stellar-population synthesis and is particularly well suited for stellar-population analysis of MaNGA galaxies. The first version of the library contains 8646 high-quality per-visit spectra for 3321 unique stars. Compared to photometry, the relative flux calibration of the library is accurate to 3.9% in g-r, 2.7% in r-i, and 2.2% in i-z. The data are released as part of SDSS Data Release 15. We expect the final release of the library to contain more than 10000 stars.
- ID:
- ivo://CDS.VizieR/J/A+A/561/A87
- Title:
- FLAMES observations of Terzan 8
- Short Name:
- J/A+A/561/A87
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Massive globular clusters (GCs) contain at least two generations of stars with slightly different ages and clearly distinct light elements abundances. The Na-O anticorrelation is the best studied chemical signature of multiple stellar generations. Low-mass clusters appear instead to be usually chemically homogeneous. We are investigating low-mass GCs to understand what is the lower mass limit where multiple populations can form, mainly using the Na and O abundance distribution. We used VLT/FLAMES spectra of giants in the low-mass, metal-poor GC Terzan 8, belonging to the Sagittarius dwarf galaxy, to determine abundances of Fe, O, Na, alpha-, Fe-peak, and neutron-capture elements in six stars observed with UVES and 14 observed with GIRAFFE. The average metallicity is [Fe/H]=-2.27+/-0.03 (rms=0.08), based on the six high-resolution UVES spectra. Only one star, observed with GIRAFFE, shows an enhanced abundance of Na and we tentatively assign it to the second generation. In this cluster, at variance with what happens in more massive GCs, the second generation seems to represent at most a small minority fraction. We discuss the implications of our findings, comparing Terzan 8 with the other Sgr dSph GCs, to GCs and field stars in the Large Magellanic Cloud, Fornax, and in other dwarfs galaxies.
- ID:
- ivo://CDS.VizieR/J/ApJ/881/79
- Title:
- Flamingos-2 near-infrared photometry in NGC 2244
- Short Name:
- J/ApJ/881/79
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- As part of the ongoing effort to characterize the low-mass (sub)stellar population in a sample of massive young clusters, we have targeted the ~2Myr old cluster NGC2244. The distance to NGC2244 from Gaia DR2 parallaxes is 1.59kpc, with errors of 1% (statistical) and 11% (systematic). We used the Flamingos-2 near-infrared camera at the Gemini-South telescope for deep multi- band imaging of the central portion of the cluster (~2.4pc^2^). We determined membership in a statistical manner, through a comparison of the cluster's color-magnitude diagram to that of a control field. Masses and extinctions of the candidate members are then calculated with the help of evolutionary models, leading to the first initial mass function (IMF) of the cluster extending into the substellar regime, with the 90% completeness limit around 0.02M{sun}. The IMF is well represented by a broken power law (dN/dM{prop}M-{alpha}) with a break at ~0.4M{sun}. The slope on the high- mass side (0.4-7M{sun}) is {alpha}=2.12{+/-}0.08, close to the standard Salpeter slope. In the low-mass range (0.02-0.4M{sun}), we find a slope {alpha}=1.03{+/-}0.02, which is at the high end of the typical values obtained in nearby star-forming regions ({alpha}=0.5-1.0), but still in agreement within the uncertainties. Our results reveal no clear evidence for variations in the formation efficiency of brown dwarfs (BDs) and very low-mass stars due to the presence of OB stars, or for a change in stellar densities. Our finding rules out photoevaporation and fragmentation of infalling filaments as substantial pathways for BD formation.
- ID:
- ivo://CDS.VizieR/J/ApJ/814/35
- Title:
- Flare events in M dwarf of M37
- Short Name:
- J/ApJ/814/35
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Based on one-month long MMT time-series observations of the open cluster M37, we monitored light variations of nearly 2500 red dwarfs and successfully identified 420 flare events from 312 cluster M dwarf stars. For each flare light curve, we derived observational and physical parameters, such as flare shape, peak amplitude, duration, energy, and peak luminosity. We show that cool stars produce serendipitous flares energetic enough to be observed in the r-band, and their temporal and peak characteristics are almost the same as those in traditional U-band observations. We also found many large-amplitude flares with inferred {Delta}u>6mag in the cluster sample which had been rarely reported in previous ground-based observations. Following the ergodic hypothesis, we investigate in detail statistical properties of flare parameters over a range of energy (E_r_~=10^31^-10^34^erg). As expected, there are no statistical differences in the distributions of flare timescales, energies, and frequencies among stars of the same age and mass group. We note that our sample tend to have longer rise and decay timescales compared to those seen in field flare stars of the same spectral type and be more energetic. Flare frequency distributions follow power-law distributions with slopes {beta}~0.62-1.21 for all flare stars and {beta}~0.52-0.97 for stars with membership information (P_mem_>=0.2). These are in general agreement with previous works on flare statistics of young open clusters and nearby field stars. Our results give further support to the classical age-activity relations.
- ID:
- ivo://CDS.VizieR/J/ApJ/723/1469
- Title:
- Flux calibrations and WZ Oph photometry
- Short Name:
- J/ApJ/723/1469
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Among several EB distance algorithms, direct comparison of observed and theoretical fluxes is particularly straightforward, although it requires absolute flux calibrations for which only a modest number of publications exist. Here, we measure UBV RI and uvby flux calibrations and calibration ratios from astronomical objects in ways not previously tried, specifically for EBs, single stars within 80pc, and the Sun. All of the single stars are below about 6500K temperature. Interstellar extinction is avoided by a restriction to nearby targets. Some photometric band calibrations in the literature are accurate enough for very good EB distance determinations if star temperatures are accurately known, especially considering that estimated distance has only a square-root dependence on calibration constant, but accurate band-to-band calibration ratios are keys to the combined temperature-distance problem. Band-independent canceling factors (star radii and distances) allow calibration ratio measurement with enhanced accuracy, compared to individual band calibrations. A physical EB model with embedded stellar atmosphere emission optimally matches theory to observations for the binaries. Single star candidates are identified as reliably single if their radial velocity variations are below 100m/s. For the most part, we find good agreement with some of the previous calibrations and the ratios are improved.
- ID:
- ivo://CDS.VizieR/J/ApJ/706/553
- Title:
- Fluxes in nearby star-forming galaxies
- Short Name:
- J/ApJ/706/553
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Compared to starburst galaxies, normal star-forming galaxies have been shown to display a much larger dispersion of the dust attenuation at fixed reddening through studies of the IRX-{beta} diagram (the IR/UV ratio "IRX" versus the UV color "{beta}"). To investigate the causes of this larger dispersion and attempt to isolate second parameters, we have used GALEX UV, ground-based optical, and Spitzer infrared imaging of eight nearby galaxies, and examined the properties of individual UV and 24um selected star-forming regions. We concentrated on star-forming regions, in order to isolate simpler star formation histories than those that characterize whole galaxies.
- ID:
- ivo://CDS.VizieR/J/ApJ/864/71
- Title:
- Fluxes & physical param. of blended YSOs
- Short Name:
- J/ApJ/864/71
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Despite significant evidence suggesting that intermediate- and high-mass stars form in clustered environments, how stars form when the available resources are shared is still not well understood. A related question is whether the initial mass function (IMF) is in fact universal across galactic environments, or whether it is an average of IMFs that differ, for example, in massive versus low-mass molecular clouds. One of the long-standing problems in resolving these questions and in the study of young clusters is observational: how to accurately combine multiwavelength data sets obtained using telescopes with different spatial resolutions. The resulting confusion hinders our ability to fully characterize clustered star formation. Here we present a new method that uses Bayesian inference to fit the blended spectral energy distributions and images of individual young stellar objects (YSOs) in confused clusters. We apply this method to the infrared photometry of a sample comprising 70 Spitzer-selected, low-mass (M_cl_<100M_{sun}_) young clusters in the galactic plane, and we use the derived physical parameters to investigate how the distribution of YSO masses within each cluster relates to the total mass of the cluster. We find that for low-mass clusters this distribution is indistinguishable from a randomly sampled Kroupa IMF for this range of cluster masses. Therefore, any effects of self-regulated star formation that affect the IMF sampling are likely to play a role only at larger cluster masses. Our results are also compatible with smoothed particle hydrodynamics models that predict a dynamical termination of the accretion in protostars, with massive stars undergoing this stopping at later times in their evolution.
