- ID:
- ivo://CDS.VizieR/J/AJ/157/212
- Title:
- Ultra-diffuse galaxies at ultraviolet wavelengths
- Short Name:
- J/AJ/157/212
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We measure near-ultraviolet (NUV) aperture magnitudes from Galaxy Evolution Explorer images for 258 ultra-diffuse galaxy (UDG) candidates drawn from the initial Systematically Measuring Ultra-Diffuse Galaxies (SMUDGes) survey of ~300 square degrees surrounding, and including, the Coma galaxy cluster. For the vast majority, 242 of them, we present flux upper limits due either to a lack of significant flux in the aperture or confusion with other objects projected within the aperture. These limits often place interesting constraints on the UDG candidates, indicating that they are non-star-forming or quiescent. In particular, we identify field, quiescent UDG candidates, which are a challenge for formation models and are, therefore, compelling prospects for spectroscopic follow-up and distance determinations. We present far-ultraviolet (FUV) and NUV magnitudes for 16 detected UDG candidates and compare those galaxies to the local population of galaxies on color-magnitude and specific star formation rate diagrams. The NUV-detected UDG candidates form mostly an extension toward lower stellar masses of the star-forming galaxy sequence, and none of these lie within regions of high local galaxy density. UDG candidates span a range of properties, although almost all are consistent with being quiescent, low surface brightness galaxies, regardless of environment.
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Search Results
- ID:
- ivo://CDS.VizieR/J/ApJ/844/157
- Title:
- Ultradiffuse galaxies found in deep HST images of HFF
- Short Name:
- J/ApJ/844/157
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the detection of a large population of ultradiffuse galaxies (UDGs) in two massive galaxy clusters, Abell S1063 at z=0.348 and Abell 2744 at z=0.308, based on F814W and F105W images in the Hubble Frontier Fields Program. We find 47 and 40 UDGs in Abell S1063 and Abell 2744, respectively. Color-magnitude diagrams of the UDGs show that they are mostly located at the faint end of the red sequence. From the comparison with simple stellar population models, we estimate their stellar mass to range from 10^8^ to 10^9^M_{sun}_. Radial number density profiles of the UDGs show a turnover or a flattening in the central region at r<100kpc. We estimate the total masses of the UDGs using the galaxy scaling relations. A majority of the UDGs have total masses M_200_=10^10^-10^11^M_{sun}_, and only a few of them have total masses M_200_=10^11^-10^12^M_{sun}_. The total number of UDGs within the virial radius is estimated to be N(UDG)=770+/-114 for Abell S1063 and N(UDG)=814+/-122 for Abell 2744. Combining these results with data in the literature, we fit the relation between the total numbers of UDGs and the masses of their host systems for M_200_>10^13^M_{sun}_ with a power law, N(UDG)=M_200_^1.05+/-0.09^. These results suggest that a majority of the UDGs have a dwarf galaxy origin, while only a small number of the UDGs are massive L* galaxies that failed to form a normal population of stars.
- ID:
- ivo://CDS.VizieR/J/ApJ/894/75
- Title:
- Ultra-diffuse & LSB dwarf galaxies in A370 from HFF
- Short Name:
- J/ApJ/894/75
- Date:
- 19 Jan 2022 13:03:46
- Publisher:
- CDS
- Description:
- We report the discovery of ultra-diffuse galaxies (UDGs) in Abell 370 (A370; z=0.375). We find 46 UDGs in A370 from the images of the Hubble Frontier Fields. Most UDGs are low-luminosity red sequence galaxies, while a few of them are blue UDGs. We estimate the abundance of UDGs in A370, N(UDG)=644+/-104. Combining these results with those of Abell S1063 (z=0.348) and Abell 2744 (z=0.308), we derive a mean radial number density profile of UDGs in the three clusters. The number density profiles of UDGs and bright galaxies show a discrepancy in the central region of the clusters: the profile of UDGs shows a flattening as clustercentric distance decreases, while that of bright galaxies shows a continuous increase. This implies that UDGs are prone to disruption in the central region of the clusters. The relation between the abundance of UDGs and virial masses of their host systems is described by a power law with an index of nearly one: N(UDG){propto}M_200_^0.99+/-0.05^ for M_200_>10^13^M_{sun}_. We estimate approximately dynamical masses of UDGs using the fundamental manifold method and find that most UDGs have dwarf-like masses (M_200_<10^11^M_{sun}_). This implies that most UDGs have a dwarf-like origin and a small number of them could be failed L* galaxies. These results suggest that multiple origins may contribute to the formation and evolution of UDGs in massive galaxy clusters.
- ID:
- ivo://CDS.VizieR/J/ApJ/739/57
- Title:
- Ultra hard X-ray AGNs in the Swift/BAT survey
- Short Name:
- J/ApJ/739/57
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have assembled the largest sample of ultra hard X-ray selected (14-195keV) active galactic nucleus (AGN) with host galaxy optical data to date, with 185 nearby (z<0.05), moderate luminosity AGNs from the Swift BAT sample. The BAT AGN host galaxies have intermediate optical colors (u-r and g-r) that are bluer than a comparison sample of inactive galaxies and optically selected AGNs from the Sloan Digital Sky Survey (SDSS) which are chosen to have the same stellar mass. Based on morphological classifications from the RC3 and the Galaxy Zoo, the bluer colors of BAT AGNs are mainly due to a higher fraction of mergers and massive spirals than in the comparison samples. BAT AGNs in massive galaxies (logM*>10.5) have a 5-10 times higher rate of spiral morphologies than in SDSS AGNs or inactive galaxies. We also see enhanced far-infrared emission in BAT AGN suggestive of higher levels of star formation compared to the comparison samples. BAT AGNs are preferentially found in the most massive host galaxies with high concentration indexes indicative of large bulge-to-disk ratios and large supermassive black holes. The narrow-line (NL) BAT AGNs have similar intrinsic luminosities as the SDSS NL Seyferts based on measurements of [OIII]5007. There is also a correlation between the stellar mass and X-ray emission. The BAT AGNs in mergers have bluer colors and greater ultra hard X-ray emission compared to the BAT sample as a whole.
- ID:
- ivo://CDS.VizieR/J/A+A/635/A205
- Title:
- Ultra-hot Jupiter WASP-121b transits
- Short Name:
- J/A+A/635/A205
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Ultra-hot Jupiters offer interesting prospects for expanding our theories on dynamical evolution and the properties of extremely irradiated atmospheres. In this context, we present the analysis of new optical spectroscopy for the transiting ultra-hot Jupiter WASP-121b. We first refine the orbital properties of WASP-121b, which is on a nearly polar (obliquity Psi^North^=88.1+/-0.25{deg} or Psi^South^=91.11+/-0.20{deg}) orbit, and exclude a high differential rotation for its fast-rotating (P<1.13-days), highly inclined (i*^North_=8.1^+3.0^_-2.6_{deg} or i*_South_=171.9^+2.5^_-3.4_{deg}) star. We then present a new method that exploits the reloaded Rossiter-McLaughlin technique to separate the contribution of the planetary atmosphere and of the spectrum of the stellar surface along the transit chord. Its application to HARPS transit spectroscopy of WASP-121b reveals the absorption signature from metals, likely atomic iron, in the planet atmospheric limb. The width of the signal (14.3+/-1.2km/s) can be explained by the rotation of the tidally locked planet. Its blueshift (-5.2+/-0.5km/s) could trace strong winds from the dayside to the nightside, or the anisotropic expansion of the planetary thermosphere.
- ID:
- ivo://CDS.VizieR/J/AJ/123/637
- Title:
- Ultra-steep-spectrum radio sources
- Short Name:
- J/AJ/123/637
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present optical and/or near-IR images of 128 ultra-steep-spectrum radio sources. Roughly half of the objects are identified in the optical images (R<~24), while in the near-IR images, more than 94% are detected at K<~22. The mean K magnitude is 19.26 within a 2" diameter aperture. The distribution of R-K colors indicates that at least one-third of the objects observed have very red colors (R-K>5). The major axes of the identifications in the K band are preferentially oriented along the radio axes, with half of them having compact morphologies. The 22 sources with spectroscopic redshifts and K-band magnitudes follow the K-z relation found from previous radio samples, but with a larger scatter.
- ID:
- ivo://CDS.VizieR/J/A+A/436/457
- Title:
- Ultra-steep spectrum radio sources
- Short Name:
- J/A+A/436/457
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of radio (VLA) and optical (ESO/La Silla) imaging of a sample of 52 radio sources having an ultra-steep radio spectrum with {alpha} mostly steeper than -1.1 at decimetre wavelengths (median {alpha}=-1.22). Radio-optical overlays are presented to an astrometric accuracy of ~1". For 41 of the sources, radio spectral indices are newly determined using unpublished observations made with the 100-m Effelsberg radio telescope. For 14 of the sources identified with relatively brighter optical counterparts, spectroscopic observations were also carried out at La Silla and their redshifts are found to lie in the range 0.4 to 2.6.
- ID:
- ivo://CDS.VizieR/VII/63
- Title:
- Ultraviolet Excess Galaxies
- Short Name:
- VII/63
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The catalog contains a list of 412 faint galaxies selected for their apparent ultraviolet excess. The galaxies were selected from a 3-color (UBV) plate taken with the Palomar 48-inch Schmidt telescope. The 14-inch-square plates cover an area of 30 square degrees centered on Kapteyn Selected Area 28. The catalog includes running numbers, coordinates, color codes, magnitude codes, morphologies, diameters, and notes. The catalogued galaxies were selected by eye from the Palomar Schmidt 3-color (UBV) plate PS24771, centered on Kapteyn Selexted Area 28 and taken by Usher under conditions of good seeing and transparency.
- ID:
- ivo://CDS.VizieR/J/AJ/137/3761
- Title:
- Ultraviolet quasi-stellar objects
- Short Name:
- J/AJ/137/3761
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a sample of spectroscopically confirmed quasi-stellar objects (QSOs) with FUV-NUV color (as measured by Galaxy Evolution Explorer (GALEX) photometry, FUV band: 1344-1786{AA}, NUV band: 1771-2831{AA}) bluer than canonical QSO templates and than the majority of known QSOs. We analyze their FUV to NIR colors, luminosities, and optical spectra. The sample includes a group of 150 objects at low redshift (z<0.5), and a group of 21 objects with redshift 1.7<z<2.6.
- ID:
- ivo://CDS.VizieR/J/ApJS/247/47
- Title:
- Ultraviolet survey of M31 with UVIT on AstroSat
- Short Name:
- J/ApJS/247/47
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- An ultraviolet survey of M31 has been carried out during 2017-19 with the UltraViolet Imaging Telescope (UVIT) instrument on board the AstroSat Observatory. Here we analyze far- and near-ultraviolet (FUV and NUV) observations from the M31 UVIT survey, which covers a sky area of ~3{deg}x1{deg} with spatial resolution of ~1". The observations included six filter bands in the wavelength range of 120-280nm. The limiting magnitude (AB) in the FUV band (CaF2 filter), which has the largest number of detected sources, is ~23. The primary product of this work is the M31 UVIT point-source catalog containing positions and photometry. In total ~75000 sources were detected at FUV or NUV wavelengths.
