- 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>)
Number of results to display per page
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/A+A/545/A141
- Title:
- UV selected sources in the GOODS-S field
- Short Name:
- J/A+A/545/A141
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Dust attenuation in galaxies is poorly known, especially at high redshift. And yet the amount of dust attenuation is a key parameter to deduce accurate star formation rates from ultraviolet (UV) rest-frame measurements. The wavelength dependence of the dust attenuation is also of fundamental importance to interpret the observed spectral energy distributions (SEDs) and to derive photometric redshifts or physical properties of galaxies. We want to study dust attenuation at UV wavelengths at high redshift, where the UV is redshifted to the observed visible light wavelength range. In particular, we search for a UV bump and related implications for dust attenuation determinations.
- 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/784/127
- Title:
- UV spectra of classical T Tauri stars
- Short Name:
- J/ApJ/784/127
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The far-ultraviolet (FUV; 912-1700 {AA}) radiation field from accreting central stars in classical T Tauri systems influences the disk chemistry during the period of giant planet formation. The FUV field may also play a critical role in determining the evolution of the inner disk (r<10 AU), from a gas- and dust-rich primordial disk to a transitional system where the optically thick warm dust distribution has been depleted. Previous efforts to measure the true stellar+accretion-generated FUV luminosity (both hot gas emission lines and continua) have been complicated by a combination of low-sensitivity and/or low-spectral resolution and did not include the contribution from the bright Ly{alpha} emission line. In this work, we present a high-resolution spectroscopic study of the FUV radiation fields of 16 T Tauri stars whose dust disks display a range of evolutionary states. We include reconstructed Ly{alpha} line profiles and remove atomic and molecular disk emission (from H_2_ and CO fluorescence) to provide robust measurements of both the FUV continuum and hot gas lines (e.g., Ly{alpha}, N V, C IV, He II) for an appreciable sample of T Tauri stars for the first time. We find that the flux of the typical classical T Tauri star FUV radiation field at 1 AU from the central star is ~10^7^ times the average interstellar radiation field. The Ly{alpha} emission line contributes an average of 88% of the total FUV flux, with the FUV continuum accounting for an average of 8%. Both the FUV continuum and Ly{alpha} flux are strongly correlated with C IV flux, suggesting that accretion processes dominate the production of both of these components. On average, only ~0.5% of the total FUV flux is emitted between the Lyman limit (912 {AA}) and the H_2_(0-0) absorption band at 1110 {AA}. The total and component-level high-resolution radiation fields are made publicly available in machine-readable format.
14996. UV spectra of old novae
- ID:
- ivo://CDS.VizieR/J/A+A/560/A49
- Title:
- UV spectra of old novae
- Short Name:
- J/A+A/560/A49
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present an overview of the UV spectral properties of old novae as a class. The data and results of this paper, together with data from the outburst phases, will be utilized in a follow-up study to determine statistical properties and to investigate correlations among the physical parameters of the quiescent and eruptive phases.
- ID:
- ivo://CDS.VizieR/J/ApJ/754/69
- Title:
- UV spectroscopy of solar-mass stars
- Short Name:
- J/ApJ/754/69
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We compare high-resolution ultraviolet spectra of the Sun and thirteen solar-mass main-sequence stars with different rotational periods that serve as proxies for their different ages and magnetic field structures. In this, the second paper in the series, we study the dependence of ultraviolet emission-line centroid velocities on stellar rotation period, as rotation rates decrease from that of the Pleiades star HII314 (P_rot_=1.47days) to {alpha} Cen A (P_rot_=28days). Our stellar sample of F9 V to G5 V stars consists of six stars observed with the Cosmic Origins Spectrograph on the Hubble Space Telescope (HST) and eight stars observed with the Space Telescope Imaging Spectrograph on HST. We find a systematic trend of increasing redshift with more rapid rotation (decreasing rotation period) that is similar to the increase in line redshift between quiet and plage regions on the Sun. The fastest-rotating solar-mass star in our study, HII314, shows significantly enhanced redshifts at all temperatures above logT=4.6, including the corona, which is very different from the redshift pattern observed in the more slowly rotating stars. This difference in the redshift pattern suggests that a qualitative change in the magnetic-heating process occurs near P_rot_=2days. We propose that HII314 is an example of a solar-mass star with a magnetic heating rate too large for the physical processes responsible for the redshift pattern to operate in the same way as for the more slowly rotating stars. HII314 may therefore lie above the high activity end of the set of solar-like phenomena that is often called the "solar-stellar connection."
- 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/731/28
- Title:
- UV star-forming association in spiral galaxies
- Short Name:
- J/ApJ/731/28
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We investigate recent star formation in the extended ultraviolet (XUV) disks of five nearby galaxies (NGC 0628, NGC 2090, NGC 2841, NGC 3621, and NGC 5055) using a long wavelength baseline comprised of ultraviolet and mid-infrared imaging from the Galaxy Evolution Explorer and the Spitzer Infrared Array Camera. We identify 229 unresolved stellar complexes across targeted portions of their XUV disks and utilize spectral energy distribution fitting to measure their stellar ages and masses through comparison with Starburst99 population synthesis models of instantaneous burst populations. We find that the median age of outer-disk associations in our sample is ~100Myr with a large dispersion that spans the entire range of our models (1Myr to 1Gyr). This relatively evolved state for most associations addresses the observed dearth of H{alpha} emission in some outer disks, as H{alpha} can only be observed in star-forming regions younger than ~10Myr. The large age dispersion is robust against variations in extinction (in the range E(B-V)=0-0.3mag) and variations in the upper end of the stellar initial mass function (IMF). In particular, we demonstrate that the age dispersion is insensitive to steepening of the IMF, up to extreme slopes.
- 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.
