Search

Start Over Capability Type Simple Cone Search
16481. UV and optical imagery of LH 52 and LH 53
ID:
ivo://CDS.VizieR/J/ApJ/446/622
Title:
UV and optical imagery of LH 52 and LH 53
Short Name:
J/ApJ/446/622
Date:
21 Oct 2021
Publisher:
CDS
Description:
A 40' field including the stellar associations LH 52 and LH 53 and the supernova remnant N49 in the Large Magellanic Cloud was observed by the Ultraviolet Imaging Telescope (UIT) during the Astro-1 Space Shuttle mission in 1990 December. The image in the 162 nm bandpass is discussed together with ground-based BV data on subfields containing LH 52 and LH 53. Point-spread function photometry in the 162nm, B, and V bands is presented in the form of color-magnitude diagrams and two-color diagrams, which are compared with stellar models. The far-ultraviolet extinction curve of the dust in LH 52 is unusually steep for the LMC. The most probable age of both associations is ~10 Myr, which constrains the scenario for the evolution of the supergiant Halpha shell LMC 4 by stochastic self-propagated star formation. The initial mass function (IMF) slope for LH 52 is Gamma~-1, in agreement with previous work, and the slope for LH 53, which is less densely populated, is Gamma~-2. A similar relationship between surface density of stars and IMF slope is reported for a UIT field near 30 Dor. The ultraviolet morphology of N49, which is contained in LH 53, is dominated by two bright features that straddle an X-ray bright spot, consistent with an encounter between the blast wave and a cloud. The estimated age of ~10Myr for LH 53 implies an initial mass of ~20M_{sun}_ for the N49 progenitor star.
16482. UV and X-Ray radio-quiet QSOs
ID:
ivo://CDS.VizieR/J/ApJ/696/924
Title:
UV and X-Ray radio-quiet QSOs
Short Name:
J/ApJ/696/924
Date:
21 Oct 2021
Publisher:
CDS
Description:
We examine the ultraviolet and X-ray properties of 256 radio-quiet Sloan Digital Sky Survey quasars (QSOs) observed in X-rays with Chandra and/or XMM-Newton in order to study the relationship between QSOs with broad CIV absorption lines (BALs; width>2000km/s) and those with CIV mini-BALs (here defined to have widths of 1000-2000km/s). Our sample includes 42 BAL and 48 mini-BAL QSOs. The relative X-ray brightness and hard spectral slopes of the mini-BAL population are, on average, intermediate between those of BAL and non-BAL QSOs, as might be expected if narrower and broader absorption line outflows are physically related. However, a significant population of mini-BALs has outflow velocities higher than would be expected for BAL QSOs of the same relative X-ray brightness. Consistently strong X-ray absorption is apparently not required to accelerate at least some mini-BALs to high outflow velocities.
16483. UVBI magnitudes and redshifts in HDF-South
ID:
ivo://CDS.VizieR/J/AJ/126/1208
Title:
UVBI magnitudes and redshifts in HDF-South
Short Name:
J/AJ/126/1208
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present a catalog of 97 (*) spectroscopic redshifts of z<1 galaxies in the Hubble Deep Field South (HDF-S) and its flanking fields (FFs). In the HDF-S proper we observed approximately half the galaxies brighter than I_814_(AB)=24 and obtained redshifts for 76% of them. Targets in our HDF-S sample were preselected to be at z<1 based on photometric redshifts, while in the FFs a simple magnitude cut was used. The photometric redshift preselection in the HDF-S resulted in a spectroscopic success rate that is significantly higher than in the FFs, where no preselection was applied. The rms precision of our redshift measurements, determined from repeat observations, is {delta}z=0.0003. We present the photometry and redshifts for the 97 objects for which we secured spectroscopic redshifts and describe the basic properties of this sample. The photometry was derived from the HST observations; the spectroscopy was obtained at the VLT using the FORS2 spectrograph on the Kueyen (UT2) and Yepun (UT4) 8.2m telescopes. (*) Actually, 103 redshifts in table1.
16484. UVB/NIR spectroscopy GRB hosts
ID:
ivo://CDS.VizieR/J/A+A/653/A83
Title:
UVB/NIR spectroscopy GRB hosts
Short Name:
J/A+A/653/A83
Date:
22 Feb 2022
Publisher:
CDS
Description:
We present the updated census and statistics of Lyman-alpha emitting long gamma-ray bursts host galaxies (LAE-LGRBs). We investigate the properties of a sub-sample of four LAE-LGRBs (GRBs: 011211, 021004, 060926, 070110). The combined observations of their afterglow and host galaxy allow us to test the shell model commonly used to fit Lyman-alpha emission line spectra.
16485. UV-brightest stars of M33 and its nucleus
ID:
ivo://CDS.VizieR/J/ApJ/469/629
Title:
UV-brightest stars of M33 and its nucleus
Short Name:
J/ApJ/469/629
Date:
21 Oct 2021
Publisher:
CDS
Description:
We investigate the UV-brightest sources in the nearby galaxy M33. Our catalog of 356 sources is constructed from far-ultraviolet (FUV; 1500A) and near-ultraviolet (NUV; 2400A) images obtained with the Ultraviolet Imaging Telescope (UIT) matched with ground-based UBV data. We find that our survey is limited by the FUV flux and is complete to F_1500=2.5x10^-15ergs/cm^2^/s/A, other than in the most crowded regions; this corresponds roughly to Mbol=-9.2 to -10.0 (or masses of 40-60M_{sun}_), for Teff=50,000{deg} to 10,000{deg}. We use Hubble Space Telescope (HST) WFPC2 images of several M33 fields to conclude that at least one-half of our sample is uncontaminated by unresolved neighbors, at least at the 0.1" (0.4pc) level, a resolution similar to that achieved in the LMC from the ground. Spectral types have been obtained for 131 of our objects. We discuss the spatial distribution of the UIT sources, finding that they provide an excellent tracer of the spiral arm pattern and confirm that star formation continues in the nuclear region to the present day. Our survey has found a large number of O and early B-type supergiants, including stars as early as O6, but the optical spectroscopic sample is dominated by later type B supergiants, as these are the visually brighter. Among the brightest stars (both at 1500A and at V) are the "superluminous" Wolf-Rayet stars first discovered by Conti & Massey in the largest H II regions of M33; these objects are now known to be small groups of stars in modest analog to R136 in 30 Dor. In general, our survey has failed to detect the known W-R stars, as they are too faint, but we did find several new late-type WN stars and composite systems, which are brighter. Two stars of high absolute visual magnitude (M_v~-9.0) are found to be B I + WN binaries, similar to HDE 269546 in the LMC; one of these is multiple at HST resolution. Most interesting, perhaps, is our finding six Ofpe/WN9 "slash" stars, five of them newly discovered. These stars show properties intermediate between those of Of and WN stars and are believed to be a quiescent form of luminous blue variables (LBVs). Our spectroscopy found five additional stars that are spectroscopically similar to the known LBVs of M33. One of these stars has recently been shown to be spectroscopically variable, and we suggest that all of these stars deserve continued scrutiny. The nucleus of M33 is the visually brightest object in our survey, and its UV colors are indicative of a hotter component than its optical photometry or spectral type would suggest. We discuss the possibility that the pointlike nucleus may contain a few interesting hot stars that dominate the light in the UV, and we make the comparison to the cluster of He I emission-line stars found near the center of the Milky Way. We comment on which color-magnitude and color-color plots make the best diagnostic tools for studying the hot, massive star population of a galaxy like M33.
16486. UV-bright quasars
ID:
ivo://CDS.VizieR/J/ApJS/185/20
Title:
UV-bright quasars
Short Name:
J/ApJS/185/20
Date:
21 Oct 2021
Publisher:
CDS
Description:
Absorption along quasar sightlines remains among the most sensitive direct measures of HeII reionization in much of the intergalactic medium (IGM). Until recently, fewer than a half-dozen unobscured quasar sightlines suitable for the HeII Gunn-Peterson test were known; although these handful demonstrated great promise, the small sample size limited confidence in cosmological inferences. We have recently added nine more such clean HeII quasars, exploiting Sloan Digital Sky Survey (SDSS) quasar samples, broadband ultraviolet (UV) imaging from Galaxy Evolution Explorer (GALEX), and high-yield UV spectroscopic confirmations from Hubble Space Telescope (HST). Here we markedly expand this approach by cross-correlating SDSS DR7 and GALEX GR4+5 to catalog 428 SDSS and 165 other quasars with z>2.78 having likely (~70%) GALEX detections, suggesting they are bright into the far-UV. Reconnaissance HST Cycle 16 Supplemental prism data for 29 of these new quasar-GALEX matches spectroscopically confirm 17 as indeed far-UV bright. At least 10 of these confirmations have clean sightlines all the way down to HeII Ly{alpha}, substantially expanding the number of known clean HeII quasars, and reaffirming the order of magnitude enhanced efficiency of our selection technique. Combined confirmations from this and our past programs yield more than 20 HeII quasars, quintupling the sample. These provide substantial progress toward a sample of HeII quasar sightlines large enough, and spanning a sufficient redshift range, to enable statistical IGM studies that may avoid individual object peculiarity and sightline variance. Our expanded catalog of hundreds of high-likelihood far-UV-bright QSOs additionally will be useful for understanding the extreme-UV properties of the quasars themselves.
16487. UV-bright quasars
ID:
ivo://CDS.VizieR/J/ApJ/690/1181
Title:
UV-bright quasars
Short Name:
J/ApJ/690/1181
Date:
21 Oct 2021
Publisher:
CDS
Description:
Investigations of HeII Ly{alpha} (304{AA} rest-frame) absorption toward a half-dozen quasars at z~3-4 have demonstrated the great potential of helium studies of the intergalactic medium, but the current critically small sample size of clean sightlines for the HeII Gunn-Peterson test limits confidence in cosmological inferences, and a larger sample is required. Although the unobscured quasar sightlines to high redshift are extremely rare, the Sloan Digital Sky Survey (SDSS) DR6 provides thousands of z>2.8 quasars. We have cross-correlated these SDSS quasars with the Galaxy Evolution Explorer (GALEX) GR2/GR3 to establish a catalog of 200 higher-confidence (~70% secure) cases of quasars at z=2.8-5.1 potentially having surviving far-UV (rest-frame) flux. We also catalog another 112 likely far-UV-bright quasars from GALEX cross-correlation with other (non-SDSS) quasar compilations. Reconnaissance UV prism observations with the Hubble Space Telescope (HST) of 24 of our SDSS/GALEX candidates confirm 12 as detected in the far-UV, with at least nine having flux extending to very near the HeII break; with refinements our success rate is even higher. Our SDSS/GALEX selection approach is thereby confirmed to be an order of magnitude more efficient than previous HeII quasar searches, more than doubles the number of spectroscopically confirmed clean sightlines to high redshift, and provides a resource list of hundreds of high-confidence sightlines for upcoming HeII and other far-UV studies from the HST. Our reconnaissance HST prism spectra suggest some far-UV diversity, confirming the need to obtain a large sample of independent quasar sightlines across a broad redshift range to assess such issues as the epoch(s) of helium reionization, while averaging over individual-object pathology and/or cosmic variance.
16488. UV-Bright Quasar Survey (UVQS) DR1 Catalog
ID:
ivo://nasa.heasarc/uvqs
Title:
UV-Bright Quasar Survey (UVQS) DR1 Catalog
Short Name:
UVQS
Date:
08 Nov 2024
Publisher:
NASA/GSFC HEASARC
Description:
This table contains data from the first data release (DR1) from the UV-bright Quasar Survey (UVQS) for new z ~ 1 active galactic nuclei (AGN) across the sky. Using simple GALEX UV and WISE near-IR color selection criteria, the authors generated a list of 1,450 primary candidates with FUV &lt; 18.5 mag, that is contained in the HEASARC table (entries with source_sample = &#39;P&#39;). They obtained discovery spectra, primarily on 3m-class telescopes, for 1,040 of these candidates and confirmed 86% as AGN, with redshifts generally at z &gt; 0.5. Including a small set of observed secondary candidates, the authors report the discovery of 217 AGN with GALEX FUV magnitudes &lt; 18 mag that previously had no reported spectroscopic redshifts. These are excellent potential targets for UV spectroscopy before the end of the Hubble Space Telescope mission. The main data products of UVQS are publicly available through the Mikulski Archive for Space Telescopes (MAST). The authors have performed an all-sky survey for z ~ 1, FUV-bright quasars selected from GALEX and WISE photometry. In several of the observing runs, conditions were unexpectedly favorable and we exhausted the primary candidates at certain right ascension ranges. To fill the remaining observing time, they generated a secondary candidate list. This secondary set of 2,010 candidates is also contained in this HEASARC table (entries with source_sample = &#39;S&#39;). The authors proceeded to obtain discovery-quality long-slit spectra (i.e., low-dispersion, large-wavelength coverage, modest signal-to-noise ratio (S/N) of their UV-bright Quasar Survey (UVQS) candidates in one calendar year. The principal facilities were: (i) the dual Kast spectrometer on the 3m Shane telescope at the Lick Observatory; (ii) the Boller &amp; Chivens (BCS) spectrometer on the Irenee du Pont 100-inch telescope at the Las Campanas Observatory; and (iii) the Calar Alto Faint Object Spectrograph on the CAHA 2.2-meter telescope at the Calar Alto Observatory (CAHA). They acquired an additional ~20 spectra on larger aperture telescopes (Keck/ESI, MMT/MBC, Magellan/MagE) during twilight or under poor observing conditions. Typical exposure times were limited to &lt; ~200s, with adjustments for fainter sources or sub-optimal observing conditions. Table 3 in the reference paper provides a list of the details of the observations of these candidates. From the total candidates list of 3,460 objects, the authors measured high-quality redshifts (redshift quality flag values of 3 or greater) for 1,121 sources. They assumed that every source with a recessional velocity v&lt;sub&gt;r&lt;/sub&gt; = z * c &lt; 500 km s&lt;sup&gt;-1&lt;/sup&gt; was &quot;Galactic&quot;, which they associate with the Galaxy and members of the Local Group. This included sources where the eigenspectra fits were poor yet a low v&lt;sub&gt;r&lt;/sub&gt; was indisputable (e.g., stars). Many of these were assigned z = 0 exactly. The remainder of the UVQS sources were assumed to be extragalactic AGN, and the derived redshift information for these sources (which was given in Table 4 of the reference paper) has been incorporated into this HEASARC representation of UVQS. Finally, there were 93 sources with good-quality spectra for which we cannot the authors could not recover a secure redshift. The majority of these have been previously cataloged as blazars (or BL Lac objects). Table 6 in the reference paper lists the sample of these unknown or insecure redshift objects. This table was created by the HEASARC in April 2017 based upon the &lt;a href="https://cdsarc.cds.unistra.fr/ftp/cats/J/AJ/152/25"&gt;CDS Catalog J/AJ/152/25&lt;/a&gt; files table1.dat, table2.dat, and table4.dat. This is a service provided by NASA HEASARC .
16489. UV-bright sources behind M31 halo
ID:
ivo://CDS.VizieR/J/MNRAS/399/728
Title:
UV-bright sources behind M31 halo
Short Name:
J/MNRAS/399/728
Date:
21 Oct 2021
Publisher:
CDS
Description:
We have performed a wide-area ultraviolet (UV) imaging survey using the GALaxy Evolution eXplorer to search for bright, point-like UV sources behind M31's extended halo. Our survey consisted of 46 pointings covering an effective area of ~50deg^2^, in both the far-UV and near-UV channels. We combined these data with optical R-band observations acquired with the WIYN Mosaic-1 imager on the Kitt Peak National Observatory 0.9-m WIYN telescope. An analysis of the brightness and colours of sources matched between our photometric catalogues yielded ~100 UV-bright quasar candidates. We have obtained discovery spectra for 76 of these targets with the Kast spectrometer on the Lick 3-m telescope and confirmed 30 active galactic nuclei and quasars, 29 galaxies at z>0.02 including several early-type systems, 16 Galactic stars (hot main-sequence stars) and one featureless source previously identified as a BL Lac object. Future UV spectroscopy of the brightest targets with the Cosmic Origins Spectrograph on the Hubble Space Telescope will enable a systematic search for diffuse gas in the extended halo of M31.
16490. UV Bright Star Spectrophotometric Catalog
ID:
ivo://CDS.VizieR/III/39A
Title:
UV Bright Star Spectrophotometric Catalog
Short Name:
III/39A
Date:
21 Oct 2021
Publisher:
CDS
Description:
This catalogue contains observations carried out by the S2/68 Ultraviolet Sky Survey Telescope (UVSST) aboard the ESRO Satellite TD-1, which measured the absolute ultraviolet flux distribution between 2740A (274nm) and 1350A (135nm). The data presented in this catalogue were obtained during the first observation period, which lasted from 19 March 1972 to 31 October 1972, and contains the brightest objects, for which the signal is good enough to give valuable spectrophotometric information. The Faint Star Catalogue, which contains the photometric data of the stars up to the limit of detectability of the instrument, is known as the "Catalogue of Ultraviolet Fluxes", by Thompson et al. (catalog <II/59>) 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).

Limit your search

more »

more »

more »

more »

more »

more »