- 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.
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14942. 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.
14943. 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.
- 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.
- 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).
- ID:
- ivo://CDS.VizieR/II/86
- Title:
- UV Bright-Star Spectrophotometric Supplement
- Short Name:
- II/86
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This catalogue is a supplement of the Ultraviolet Bright Star Spectrophotometric Catalogue (=III/39A). It contains observations carried out by the S2/68 Ultraviolet Sky Survey Telescope (UVSST) aboard the ESRO satellite TD-1. The data presented in this supplement were obtained during the second and third observation periods, which lasted from 19 February 1973 to 30 September 1973 and from 16 February to 6 May 1974. The S2/68 experiment has been described by Boksenberg et al. (=1973MNRAS.163..291B) Owing to the optical scanning mode, most of the stars observed during the first observational period, the spectra of which are included in the "Ultraviolet Bright-Star Spectrophotometric Catalogue", were seen again by the telescope. This supplement, however, has been limited to the spectra of stars that were not observed during the first period. The data reduction and selection criteria are identical to those underlying the main Catalogue and hence the data presented in the Supplement are directly comparable with those in the main Catalogue. The Supplement contains data for 435 stars. For a statistical summary of the observed stars, see the tables I and II in the published version of the Supplement. The spectrum scanning itself was achieved by the movement of a star image across the wide entrance slot of the spectrophotometer, which caused the corresponding spectrum image to pass over the three exit slits in the direction of dispersion. The motion of the primary image during each detector integration interval (0.148 s) was equivalent to 19.4 A, depending on the channel. The wavelength range covered was 1350 - 2550 A. The passband of the photometer channel, defined by a glass transmission filter and the photocathode tube response, was centered at 2740 A and had a full width at half height of 310 A.
14947. uvby-beta Catalogue
- ID:
- ivo://CDS.VizieR/II/215
- Title:
- uvby-beta Catalogue
- Short Name:
- II/215
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This catalogue is an updated version of the one published in 1990 (Hauck and Mermilliod, 1990) and contains data for more than 63,300 stars in the Galaxy and Magellanic Clouds. In a first table, we present the catalogue itself, giving for each star identifications, coordinates (B1950), visual magnitude, and the mean value of the photoelectric data concerning the star and the data sources. In the second table, we give for each star, the individual measurements. These measurements from which these values were computed were collected from observations published until the middle of 1996. The catalogue includes 533 references.
- ID:
- ivo://CDS.VizieR/J/A+A/549/A78
- Title:
- uvby{beta} photometric catalog toward Anticenter
- Short Name:
- J/A+A/549/A78
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A uvbyH{beta} Stromgren photometric survey covering 16sq.deg in the anticenter direction was carried out using the Wide Field Camera (WFC) at the Isaac Newton Telescope (INT), with a typical seeing of 1-1.5". Data from three different observing runs (2009A, 2010B, 2011A) were used for the catalog. The calibration to the standard system was undertaken using open clusters. A main catalog of 35974 stars with all Stromgren indexes, and a more extended one with 96980 stars with partial data. The central 8sq.deg have a limiting magnitude of V=17mag while the outer region reaches V=15.5mag. Two catalogs are available, the first one with the final mean values and a second one with all the individual measurements for each star.
- ID:
- ivo://CDS.VizieR/J/A+A/514/A59
- Title:
- uvby{beta} photometry in Carina. II
- Short Name:
- J/A+A/514/A59
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In recent years a significant development has become evident in the study of the stellar structure of the Galactic disk. This is especially true for the 3rd Galactic quadrant, where the stellar population was extensively investigated beyond 10kpc, revealing details about the warped geometry of the thin and thick disks and outer arm. The 4th Galactic quadrant offers even better opportunity to follow the distribution of the young stellar populace to a large distance, since the line of sight is parallel to the largest single segment of a spiral arm seen from our position in the Galaxy: the Carina spiral feature. This paper further contributes to the study of the structure of the Galactic disk in the direction of Carina field utilizing homogeneous photometric distances of a sample of about 600 bright early-type stars seen in this direction up to 6kpc. The derived stellar distances are based on uvby{beta} photometry. All O and B type stars with uvby{beta} data presently available are included in the study.
- ID:
- ivo://CDS.VizieR/J/A+AS/112/95
- Title:
- uvby-beta photometry in Cen-Cru-Mus-Cha
- Short Name:
- J/A+AS/112/95
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Stroemgren uvby{beta} photometry has been collected for a total of 1017 stars earlier than G0 lying in an area of the sky containing the Southern Coalsack, the Musca, and the Chamaeleon dark clouds. The targets were selected from the SAO star catalog, and the results give V, b-y, m_1_, c_1_, and {beta} on the standard systems, with overall rms errors for one observation of one star of 0.008mag , 0.004mag , 0.006mag , 0.009mag , and 0.011mag , respectively.
