- ID:
- ivo://CDS.VizieR/J/AJ/160/217
- Title:
- 342 FGK-dwarfs ages using GALEX FUV magnitudes
- Short Name:
- J/AJ/160/217
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Stellar age cannot be directly measured, yet age determinations are fundamental to understanding the evolution of stars, planets, and galaxies. The work presented here builds upon the idea of a stellar-activity age. We utilized far-ultraviolet (FUV) photometry acquired by the Galaxy Evolution Explorer (GALEX) space telescope as an indicator of chromospheric activity to infer ages of late-F, G, and K type dwarf stars. We derived a purely empirical correlation between FUV magnitudes and stellar age in conjunction with (B-V) color. Our attention is restricted to Sun-like stars with color range 0.55<=(B-V)<=0.71 and absolute magnitude range 4.3<=MV<=5.3. The correlation is defined in terms of a FUV-excess parameter Q(FUV-B,B-V). We related stellar age, {tau}, to Q through the relation log_e_({tau})=log_e_(a)+bQ, where a and b are fit parameters and functions of (B-V). This correlation is functional up to 6Gyr for FGK dwarfs. With such a correlation, one only needs Johnson (B-V) and FUV measurements to estimate the stellar age for Population i dwarf stars of solar-like temperature and metallicity. Such a calibration has utility in population studies of FGK dwarfs for further understanding of the chemical evolution of the Milky Way. As an illustration of one such application, we have constructed activity and FUV-age distributions for a sample of thin and thick disk stars, as distinguished by their chemical abundances. Considerable overlap is found between the activity distribution and age range of the two populations. We discuss the possibility that some high-[{alpha}/Fe] thick disk stars were formed as a result of the accretion of dwarf galaxies as recently as 4Gyr ago.
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- 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/MNRAS/446/2030
- Title:
- FUV and NUV magnitudes of ETG
- Short Name:
- J/MNRAS/446/2030
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We extend our initial study of the connection between the UV colour of galaxies and both the inferred stellar mass-to-light ratio, {Upsilon}*, and a mass-to-light ratio referenced to Salpeter initial mass function (IMF) models of the same age and metallicity, {Upsilon}*/{Upsilon}_Sal_, using new UV magnitude measurements for a much larger sample of early-type galaxies, ETGs, with dynamically determined mass-to-light ratios. We confirm the principal empirical finding of our first study, a strong correlation between the GALEX FUV-NUV colour and {Upsilon}*. We show that this finding is not the result of spectral distortions limited to a single passband (e.g. metallicity-dependent line-blanketing in the NUV band), or of the analysis methodology used to measure {Upsilon}*, or of the inclusion or exclusion of the correction for stellar population effects as accounted for using {Upsilon}*/{Upsilon}_Sal_. The sense of the correlation is that galaxies with larger {Upsilon}*, or larger {Upsilon}*/{Upsilon}_Sal_, are bluer in the UV. We conjecture that differences in the low-mass end of the stellar IMF are related to the nature of the extreme horizontal branch stars generally responsible for the UV flux in ETGs. If so, then UV colour can be used to identify ETGs with particular IMF properties and to estimate {Upsilon}*. We also demonstrate that UV colour can be used to decrease the scatter about the Fundamental Plane and Manifold, and to select peculiar galaxies for follow-up with which to further explore the cause of variations in {Upsilon}* and UV colour.
- ID:
- ivo://CDS.VizieR/J/ApJ/504/113
- Title:
- F175W and F275W photometry of M31 and M32
- Short Name:
- J/ApJ/504/113
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present Faint Object Camera (FOC) ultraviolet images of the central 14"x14" of Messier 31 and Messier 32. The hot stellar populations detected in the composite UV spectra of these nearby galaxies are partially resolved into individual stars, and their individual colors and apparent magnitudes are measured. We detect 433 stars in M31 and 138 stars in M32, down to detection limits m_F275W_=25.5mag and m_F175W_=24.5mag.
- ID:
- ivo://CDS.VizieR/J/AJ/112/359
- Title:
- Galaxies in the Hubble Deep Field
- Short Name:
- J/AJ/112/359
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a catalog of morphological and color data for galaxies with 21<I_814<25mag in the Hubble Deep Field (Williams et al. 1996, in Science with the Hubble Space Telescope II). Galaxies have been inspected and (when possible) independently visually classified on the MDS and DDO systems. Measurements of central concentration and asymmetry are also included in the catalog. The fraction of interacting and merging objects is seen to be significantly higher in the Hubble Deep Field than it is among nearby galaxies. Barred spirals are essentially absent from the deep sample. The fraction of early-type galaxies in the Hubble Deep Field is similar to the fraction of early-types in the Shapley-Ames Catalog, but the fraction of galaxies resembling archetypal grand-design late-type spiral galaxies is dramatically lower in the distant HDF sample.
- ID:
- ivo://CDS.VizieR/J/ApJ/790/76
- Title:
- Galaxies near NGC 891 properties
- Short Name:
- J/ApJ/790/76
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report the results of a survey of the region within 40 arcmin of NGC 891, a nearby nearly perfectly edge-on spiral galaxy. Candidate "non-stars" with diameters greater than 15 arcsec were selected from the GSC 2.3.2 catalog and cross-comparison of observations in several bands using archived GALEX, DSS2, WISE, and Two Micron All Sky Survey images identified contaminating stars, artifacts, and background galaxies, all of which were excluded. The resulting 71 galaxies, many of which were previously uncataloged, comprise a size-limited survey of the region. A majority of the galaxies are in the background of NGC 891 and are for the most part members of the A347 cluster at a distance of about 75 Mpc. The new finds approximately double the known membership of A347, previously thought to be relatively sparse. We identify a total of seven dwarf galaxies, most of which are new discoveries. The newly discovered dwarf galaxies are dim and gas-poor and may be associated with the previously observed arcs of red giant branch halo stars in the halo and the prominent H I filament and the lopsided features in the disk of NGC 891. Several of the dwarfs show signs of disruption, consistent with being remnants of an ancient collision.
- ID:
- ivo://CDS.VizieR/J/ApJ/872/95
- Title:
- GALEX and Gaia data for APOGEE red clump stars
- Short Name:
- J/ApJ/872/95
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Although core helium-burning red clump (RC) stars are faint at ultraviolet wavelengths, their ultraviolet (UV)-optical color is a unique and accessible probe of their physical properties. Using data from the Galaxy Evolution Explorer All Sky Imaging Survey (GALEX AIS), Gaia Data Release 2, and the Sloan Digital Sky Survey Apache Point Observatory Galactic Evolution Experiment (APOGEE) DR14 survey, we find that spectroscopic metallicity is strongly correlated with the location of an RC star in the UV-optical color-magnitude diagram. The RC has a wide spread in (NUV-G)_0_ color of over 4mag compared to a 0.7mag range in (G_BP_-G_RP_)_0_. We propose a photometric, dust-corrected, UV-optical (NUV-G)_0_ color-metallicity [Fe/H] relation using a sample of 5175 RC stars from APOGEE. We show that this relation has a scatter of 0.16dex and is easier to obtain for large, wide-field samples than for spectroscopic metallicities. Importantly, the effect may be comparable to the spread in RC color attributed to extinction in other studies.
- ID:
- ivo://CDS.VizieR/J/A+A/611/A42
- Title:
- GALEX BCG galaxies sample properties
- Short Name:
- J/A+A/611/A42
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- At low redshift, early-type galaxies often exhibit a rising flux with decreasing wavelength in the 1000-2500{AA} range, called "UV upturn". The origin of this phenomenon is debated, and its evolution with redshift is poorly constrained. The observed GALEX FUV-NUV color can be used to probe the UV upturn up to redshift about 0.5. We aim to provide constraints on the existence of the UV upturn up to redshift ~0.4 in Brightest Cluster Galaxies (BCG) galaxies located behind the Virgo cluster, using data from the GUViCS survey. We estimate the FUV and NUV observed magnitudes for BCGs from the maxBCG catalog in the GUViCS fields. We increase the number of non local galaxies identified as BCGs with GALEX photometry from a few tens of galaxies to 166 (64 when restricting this sample to relatively small error-bars). We also estimate a central color within a 20-arcsec aperture. By using the r band luminosity from the maxBCG catalog, we can separate blue FUV-NUV due to recent star formation and candidate upturn cases. We use Lick indices to verify their similitude to redshift 0 upturn cases. We clearly detect a population of blue FUV-NUV BCGs in the redshift range 0.10-0.35, vastly improving the existing constraints at these epochs by increasing the number of galaxies studied, and by exploring a redshift range with no previous data (beyond 0.2), spanning 1 more Gyr in the past. These galaxies bring new constrains that can help distinguish between assumptions concerning the stellar populations causing the UV upturn phenomenon. The existence of a large number of UV upturns around redshift 0.25 favors the existence of a binary channel among the sources proposed in the literature.
- ID:
- ivo://CDS.VizieR/J/ApJS/199/37
- Title:
- GALEX catalog of star clusters in M31
- Short Name:
- J/ApJS/199/37
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a comprehensive catalog of 700 confirmed star clusters in the field of M31 compiled from three major existing catalogs. We detect 418 and 257 star clusters in Galaxy Evolution Explorer near-ultraviolet and far-ultraviolet (FUV) imaging, respectively. Our final catalog includes photometry of star clusters in up to 16 passbands ranging from FUV to NIR as well as ancillary information such as reddening, metallicity, and radial velocities. In particular, this is the most extensive and updated catalog of UV-integrated photometry for M31 star clusters. Ages and masses of star clusters are derived by fitting the multi-band photometry with model spectral energy distribution (SED); UV photometry enables more accurate age estimation of young clusters. Our catalog includes 182 young clusters with ages less than 1Gyr. Our estimated ages and masses of young clusters are in good agreement with previously determined values in the literature. The mean age and mass of young clusters are about 300Myr and 10^4^M_{sun}_, respectively.
- ID:
- ivo://CDS.VizieR/II/312
- Title:
- GALEX-DR5 (GR5) sources from AIS and MIS
- Short Name:
- II/312
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Galaxy Evolution Explorer (GALEX) is an ultraviolet space telescope launched in 2003. It observes in 2 ultraviolet bands, FUV (far-UV) and NEV (near-UV), which characteristics are: -------------------------------------------------------------------- FUV NUV -------------------------------------------------------------------- Bandwidth 1344-1786 1771-2831 ({AA}) Effective wavelength 1538.6 2315.7 ({AA}) Astrometry (R<0.6deg) 0.59 0.49 (arcsec) Photometry 0.05 0.03 (ABmag) Zero point 18.82 20.08 (ABmag) Image resolution 4.2 5.3 (arcsec/pix) Spectral resolution 200 118 ({delta}{lambda}/{lambda}) -------------------------------------------------------------------- Two catalogs of UV sources from GALEX surveys are provided: * the All-sky Imaging Survey (AIS), containing 65.3million sources over 21435 square degrees, has a 5{sigma} depth in FUV/NUV of 19.9/20.8 (AB magnitudes); * the Medium-depth Imaging Survey (MIS), with 12.6million sources, covers 1579 square degrees and has a 5{sigma} depth in FUV/NUV of 22.6/22.7 (AB magnitudes). See also the description by Bianchi et al. (2011MNRAS.411.2770B)
