- ID:
- ivo://CDS.VizieR/J/MNRAS/300/303
- Title:
- UV-selected galaxy redshift survey
- Short Name:
- J/MNRAS/300/303
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The table contains the first results of a spectroscopic survey of galaxies constructed from a flux-limited sample of stars, galaxies and QSOs imaged at 2000{AA} with the FOCA balloon-borne imaging camera (see Milliard et al., 1992A&A...257...24M) The galaxies were selected in the rest frame ultraviolet (UV), in Selected Area 57. Accurate positions for the UV sources have been obtained by matching with optical counterparts using APM scans of the Palomar Sky Survey limited at B=20.5. The results presented here are derived from optical spectroscopy conducted with the WIYN telescope and the WHT for 142 faint sources. The redshift distribution for this UV- selected sample extends over 0<z<0.5, and a high fraction of the sources show intense nebular emission lines and UV-optical colours bluer than normal Hubble sequence galaxies. Updated results for these galaxies were published later (see Sullivan et al. 2000, Cat. <J/MNRAS/312/442>)
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Search Results
- ID:
- ivo://CDS.VizieR/J/MNRAS/312/442
- Title:
- UV-selected galaxy redshift survey. II.
- Short Name:
- J/MNRAS/312/442
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present further spectroscopic observations for a sample of galaxies selected in the vacuum ultraviolet (UV) at 2000{AA} from the FOCA balloon-borne imaging camera of Milliard et al. (1992A&A...257...24M). This work represents an extension of the initial study by Treyer et al. (Cat. <J/MNRAS/300/303>). Our enlarged catalogue contains 433 sources (~3 times as many as in our earlier study) across two FOCA fields. 273 of these are galaxies, nearly all with redshifts z~0-0.4. Nebular emission-line measurements are available for 216 galaxies, allowing us to address issues of excitation, reddening and metallicity. The UV and H{alpha} luminosity functions strengthen our earlier assertions that the local volume-averaged star formation rate is higher than indicated from earlier surveys. Moreover, internally within our sample, we do not find a steep rise in the UV luminosity density with redshift over 0<z<0.4. Our data are more consistent with a modest evolutionary trend, as suggested by recent redshift survey results. Investigating the emission-line properties, we find no evidence for a significant number of AGN in our sample; most UV-selected sources to z~0.4 are intense star-forming galaxies.
- ID:
- ivo://CDS.VizieR/J/AJ/139/1338
- Title:
- UV-selected stars in Tau and Upper Sco
- Short Name:
- J/AJ/139/1338
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have carried out a Galaxy Evolution Explorer (GALEX) Cycle 1 guest investigator program covering 56deg^2^ near the Taurus T association and 12deg^2^ along the northern edge of the Upper Scorpius OB association. We combined photometry in the GALEX far-ultraviolet and near-ultraviolet bands with data from the Two Micron All Sky Survey to identify candidate young (<~100Myr old) stars as those with an ultraviolet excess relative to older main-sequence stars. Follow-up spectroscopy of a partial sample of these candidates suggests five new members of Taurus, with 8-20 expected from additional observations, and five new members of Upper Scorpius, with three to six expected from additional observations.
- ID:
- ivo://CDS.VizieR/J/ApJ/770/137
- Title:
- UV star clusters in 4 elliptical galaxies
- Short Name:
- J/ApJ/770/137
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Small amounts of star formation in elliptical galaxies are suggested by several results: surprisingly young ages from optical line indices, cooling X-ray gas, and mid-infrared dust emission. Such star formation has previously been difficult to directly detect, but using ultraviolet Hubble Space Telescope Wide Field Camera 3 imaging, we have identified individual young stars and star clusters in four nearby ellipticals. Ongoing star formation is detected in all galaxies, including three ellipticals that have previously exhibited potential signposts of star-forming conditions (NGC 4636, NGC 4697, and NGC 4374), as well as the typical "red and dead" NGC 3379. The current star formation in our closest targets, where we are most complete, is between 2.0 and 9.8x10^-5^M_{sun}_/yr. The star formation history was roughly constant from 0.5 to 1.5 Gyr (at (3-5)x10^-4^M_{sun}_/yr), but decreased by a factor of several in the past 0.3Gyr. Most star clusters have a mass between 10^2^ and 10^4^M_{sun}_. The specific star formation rates of ~10^-16^/yr (at the present day) or ~10^-14^/yr (when averaging over the past Gyr) imply that a fraction 10^-8^ of the stellar mass is younger than 100Myr and 10^-5^ is younger than 1Gyr, quantifying the level of frosting of recent star formation over the otherwise passive stellar population. There is no obvious correlation between either the presence or spatial distribution of postulated star formation indicators and the star formation we detect.
- ID:
- ivo://CDS.VizieR/J/ApJ/703/614
- Title:
- UV star-forming regions in M31
- Short Name:
- J/ApJ/703/614
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a comprehensive study of star-forming (SF) regions in the nearest large spiral galaxy M31. We use Galaxy Evolution Explorer (GALEX) far-UV (1344-1786{AA}, FUV) and near-UV (1771-2831{AA}, NUV) imaging to detect young massive stars and trace the recent star formation across the galaxy. The FUV and NUV flux measurements of the SF regions, combined with ground-based data for estimating the reddening by interstellar dust from the massive stars they contain, are used to derive their ages and masses. The GALEX imaging, combining deep sensitivity and coverage of the entire galaxy, provides a complete picture of the recent star formation in M31 and its variation with environment throughout the galaxy. The FUV and NUV measurements are sensitive to detect stellar populations younger than a few hundred Myr. We detected 894 SF regions, with size >=1600pc^2^ above an average FUV flux limit of ~26ABmag/arcsecond^2^, over the whole 26kpc (radius) galaxy disk. We derive the star formation history of M31 within this time span. The star formation rate (SFR) from the youngest UV sources (age <=10Myr) is comparable to that derived from H{alpha}, as expected.
- ID:
- ivo://CDS.VizieR/J/A+A/602/A97
- Title:
- UV structure of 11 galaxies with Swift-UVOT
- Short Name:
- J/A+A/602/A97
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- GALEX detected a significant fraction of early-type galaxies, in particular S0s, showing Far-UV bright structures, sometimes involving an entire galaxy out to its outskirts. These features suggest the presence of either recent, ongoing and/or prolonged star formation episodes, shedding new light on the evolution of these systems. We aim at understanding the evolutionary path[s] of these early-type galaxies and the mechanisms at the origin of their UV-bright structures. We investigate with a multi{lambda} approach the link between the inner and the outer galaxy regions of a set of eleven early-type galaxies selected because of their nearly passive stage of evolution in the nuclear region. This paper, second of a series, focuses on the information coming from the comparison between UV features detected by Swift-UVOT, tracing recent star formation, and the galaxy optical structure mapping older stellar populations. We performed a surface photometric study of these early-type galaxies, observed with Swift-UVOT UV filters, W2 2030{AA} {lambda_0}, M2 2231{AA} {lambda_0}, W1 2634{AA} {lambda_0}, and UBV bands. BVRI photometry from other sources in the literature is also used. Our integrated magnitude measurements have been analyzed and compared with corresponding values in the literature. We characterize the overall galaxy structure best fitting the UV and optical luminosity profiles using a single Sersic law. NGC 1366, NGC 1426, NGC 3818, NGC 3962 and NGC 7192 show featureless luminosity profiles. Excluding NGC~1366 which has a clear edge-on disk (n~1-2), and NGC 3818, the remaining three have Sersic's indices n~3-4 in optical and a lower index in the UV. Bright ring/arm-like structures are revealed by UV images and luminosity profiles of NGC 1415, NGC 1533, NGC 1543, NGC 2685, NGC 2974 and IC 2006. The ring/arm-like structures are different from galaxy to galaxy. Sersic indices of UV profiles for those galaxies are in the range n=1.5-3 both in S0s and in galaxies classified as "bona fide" ellipticals, such as NGC 2974 and IC 2006. We notice that in our sample optical Sersic indices are usually larger than in the UV ones. (M2-V) color profiles are bluer in ring/arm-like structures with respect to the galaxy body. The lower values of Sersic's indices in the UV bands with respect to optical ones, suggesting the presence of a disk, point out that the role of the dissipation cannot be neglected in recent evolutionary phases of these early-type galaxies.
- ID:
- ivo://CDS.VizieR/J/ApJS/199/22
- Title:
- UV to far-IR photometry of galaxies
- Short Name:
- J/ApJS/199/22
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In this paper, we present a sample of cluster galaxies devoted to study the environmental influence on the star formation activity. This sample of galaxies inhabits in clusters showing a rich variety in their characteristics and have been observed by the SDSS-DR6 down to M_B_~-18, and by the Galaxy Evolution Explorer AIS throughout sky regions corresponding to several megaparsecs. We assign the broadband and emission-line fluxes from ultraviolet to far-infrared to each galaxy performing an accurate spectral energy distribution for spectral fitting analysis. The clusters follow the general X-ray luminosity versus velocity dispersion trend of L_X_{propto}{sigma}^4.4^_c_.
- ID:
- ivo://CDS.VizieR/J/ApJS/143/377
- Title:
- UV-to-FIR magnitudes for 83 starburst galaxies
- Short Name:
- J/ApJS/143/377
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a database of UV-to-FIR data of 83 nearby starburst galaxies. The galaxies are selected based upon the availability of IUE data. We have recalibrated the IUE UV spectra for these galaxies by incorporating the most recent improvements. For 45 of these galaxies we use observations by Storchi-Bergmann et al. (1995ApJS...98..103S) and McQuade et al. (1995ApJS...97..331M) for the spectra in the optical range. The NIR data are from new observations obtained at the NASA/IRTF and the Mount Laguna Observatory, combined with the published results from observations at the Kitt Peak National Observatory. In addition, published calibrated ISO data are included to provide mid-IR flux densities for some of the galaxies. The optical-to-IR data are matched as closely as possible to the IUE large aperture. In conjunction with IRAS and ISO FIR flux densities, all these data form a set of observed spectral energy distributions (SEDs) of the nuclear regions of nearby starburst galaxies. The SEDs should be useful in studying star formation and dust/gas attenuation in galaxies. We also present the magnitudes in the standard BVRI and various HST/WFPC2 bandpasses synthesized from the UV and optical wavelength ranges of these SEDs. For some of the galaxies, the HST/WFPC2 magnitudes synthesized from the SEDs are checked with those directly measured from WFPC2 images to test the photometric errors of the optical data and their effective matching of apertures with the UV data. The implications of the new SEDs on the star formation rates and dust/gas attenuation are briefly discussed.
- ID:
- ivo://CDS.VizieR/J/AJ/111/1128
- Title:
- UV-UBV photometry in NGC 595
- Short Name:
- J/AJ/111/1128
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- As part of a larger effort to study the resolved and composite properties of the giant H II regions in Messier 33, we have analyzed multiband HST/WFPC-2 images of NGC 595 in terms of the ionizing cluster's resolved stellar population. Photometric reductions of the PC images yield 100 stars in the UV image, 272 stars on the U image, 345 stars on the B image, and 561 stars on the V image. A total of 267 stars are common to the U, B, and V images while 86 stars are detected on all 4 images. Although some clustering is evident, the degree of central concentration is less than that seen in 30 Doradus. The resulting U-B vs B-V diagram of the resolved stars is used to determine the reddening of each star. The average reddening derived from this diagram is E(B-V)=0.36+/-0.28mag. The dereddened color-M_V diagram is best fit by a model cluster having an age of 4.5+/-1.0Myr, and hence initial masses no greater than 51M_{sun}_. A total of 13 supergiant stars and 10 candidate WR stars [Drissen et al. (1993AJ....105.1400D), and references therein] are identified with M_V=-5 to -8mag. The remainder are main-sequence O-type (98) and early B-type (>145) stars with M_V=-1 to -6mag. The ratio of WR to O stars is WR/O=0.11+/-0.01, roughly the same as found in the core of 30 Doradus. The resulting luminosity function has a slope of alpha=-0.71. The derived IMF has a slope of Gamma=-1.32+/-0.02 before subtracting a background component, and Gamma=-1.00+/-0.05 after subtracting a background based on photometry of the surrounding WF images. Integration of the derived IMF down to a lower mass limit of 4M_{sun}_ yields a total mass of 7350M_{sun}_, while integration down to 0.1_{Msun}_ yields a total mass of 18000M_{sun}_. The total estimated ionizing luminosity is 5.0x10^50photon/s, roughly half that which is inferred from the Halpha luminosity in this region. This shortfall of ionizing photons can be reconciled by allowing for a spread in the stellar ages, and/or increasing the modeled EUV luminosity of the stars at the inferred cluster age.
- ID:
- ivo://CDS.VizieR/J/ApJS/238/25
- Title:
- UV variability with GALEX gPhoton archive. I.
- Short Name:
- J/ApJS/238/25
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In order to develop and test a methodology to search for UV variability over the entire Galaxy Evolution Explorer (GALEX) database down to the shortest timescales, we analyzed time-domain photometry of ~5000 light curves of ~300 bright (mFUV, mNUV<=14) and blue (mFUV-mNUV<0) GALEX sources. Using the gPhoton database tool, we discovered and characterized instrumentally induced variabilities in time-resolved GALEX photometry that may severely impact automated searches for short-period variations. The most notable artifact is a quasi-sinusoidal variation mimicking light curves typical of pulsators, seen occasionally in either one or both detectors, with amplitudes of up to 0.3mag and periods corresponding to the periodicity of the spiral dithering pattern used during the observation (P~120s). Therefore, the artifact may arise from small-scale response variations. Other artifacts include visit-long "sagging" or "hump" in flux, occurring when the dithering pattern is not a spiral, or a one-time change in flux level during the exposure. These instrumentally caused variations were not reported before, and are not due to known (and flagged) artifacts such as hotspots, which can be easily eliminated. To characterize the frequency and causality of such artifacts, we apply Fourier transform analysis to both light curves and dithering patterns, and examine whether artificial brightness variations correlate with visit or instrumental parameters. Artifacts do not correlate with source position on the detector. We suggest methods to identify artifact variations and to correct them when possible.
