- ID:
- ivo://CDS.VizieR/J/PASJ/70/S10
- Title:
- GOLDRUSH I. UV magnitudes
- Short Name:
- J/PASJ/70/S10
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We study the UV luminosity functions (LFs) at z~4, 5, 6, and 7 based on the deep large-area optical images taken by the Hyper Suprime-Cam (HSC) Subaru Strategic Program (SSP). On the 100 deg^2^ sky of the HSC SSP data available to date, we take enormous samples consisting of a total of 579565 dropout candidates at z~4-7 by the standard color selection technique, 358 out of which are spectroscopically confirmed by our follow-up spectroscopy and other studies. We obtain UV LFs at z~4-7 that span a very wide UV luminosity range of ~0.002-100L^*^_UV_(-26<M_UV_<-14mag) by combining LFs from our program and the ultra-deep Hubble Space Telescope legacy surveys. We derive three parameters of the best-fit Schechter function, {Phi}^*^, M_UV_, and {alpha}, of the UV LFs in the magnitude range where the active galactic nucleus (AGN) contribution is negligible, and find that and {Phi}^*^ decrease from z~4 to 7 with no significant evolution of M_UV_. Because our HSC SSP data bridge the LFs of galaxies and AGNs with great statistical accuracy, we carefully investigate the bright end of the galaxy UV LFs that are estimated by the subtraction of the AGN contribution either aided by spectroscopy or the best-fit AGN UV LFs. We find that the bright end of the galaxy UV LFs cannot be explained by the Schechter function fits at >2{sigma} significance, and require either double power-law functions or modified Schechter functions that consider a magnification bias due to gravitational lensing.
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Search Results
- ID:
- ivo://CDS.VizieR/J/ApJS/207/24
- Title:
- GOODS-S CANDELS multiwavelength catalog
- Short Name:
- J/ApJS/207/24
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a UV to mid-infrared multi-wavelength catalog in the CANDELS/GOODS-S field, combining the newly obtained CANDELS HST/WFC3 F105W, F125W, and F160W data with existing public data. The catalog is based on source detection in the WFC3 F160W band. The F160W mosaic includes the data from CANDELS deep and wide observations as well as previous ERS and HUDF09 programs. The mosaic reaches a 5{sigma} limiting depth (within an aperture of radius 0.17") of 27.4, 28.2, and 29.7 AB for CANDELS wide, deep, and HUDF regions, respectively. The catalog contains 34930 sources with the representative 50% completeness reaching 25.9, 26.6, and 28.1 AB in the F160W band for the three regions. In addition to WFC3 bands, the catalog also includes data from UV (U band from both CTIO/MOSAIC and VLT/VIMOS), optical (HST/ACS F435W, F606W, F775W, F814W, and F850LP), and infrared (HST/WFC3 F098M, VLT/ISAAC Ks, VLT/HAWK-I Ks, and Spitzer/IRAC 3.6, 4.5, 5.8, 8.0{mu}m) observations. The catalog is validated via stellar colors, comparison with other published catalogs, zero-point offsets determined from the best-fit templates of the spectral energy distribution of spectroscopically observed objects, and the accuracy of photometric redshifts. The catalog is able to detect unreddened star-forming (passive) galaxies with stellar mass of 10^10^M_{sun}_ at a 50% completeness level to z~3.4 (2.8), 4.6 (3.2), and 7.0 (4.2) in the three regions. As an example of application, the catalog is used to select both star-forming and passive galaxies at z~2-4 via the Balmer break. It is also used to study the color-magnitude diagram of galaxies at 0<z<4.
- ID:
- ivo://CDS.VizieR/J/ApJ/792/L4
- Title:
- GV galaxies UV-optical radial color profiles
- Short Name:
- J/ApJ/792/L4
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In this Letter, we analyze the radial ultraviolet-optical color distributions in a sample of low redshift green valley galaxies, with the Galaxy Evolution Explorer (GALEX)+Sloan Digital Sky Survey (SDSS) images, to investigate how the residual recent star formation is distributed in these galaxies. We find that the dust-corrected u-r colors of early-type galaxies (ETGs) are flat out to R_90_, while the colors monotonously turn blue when r>0.5 R_50_ for late-type galaxies (LTGs). More than half of the ETGs are blue-cored and have remarkable positive NUV-r color gradients, suggesting that their star formations are centrally concentrated. The rest have flat color distributions out to R_90_. The centrally concentrated star formation activity in a large portion of ETGs is confirmed by the SDSS spectroscopy, showing that ~50% of the ETGs have EW(H{alpha})>6.0 {AA}. Of the LTGs, 95% show uniform radial color profiles, which can be interpreted as a red bulge plus an extended blue disk. The links between the two kinds of ETGs, e.g., those objects having remarkable "blue-cores" and those having flat color gradients, are less known and require future investigations. It is suggested that the LTGs follow a general model by which quenching first occurs in the core regions, and then finally extend to the rest of the galaxy. Our results can be re-examined and have important implications for the IFU surveys, such as MaNGA and SAMI.
- ID:
- ivo://CDS.VizieR/J/A+A/644/A38
- Title:
- Halpha images of stellar bars in galaxies
- Short Name:
- J/A+A/644/A38
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Stellar bars are known to gradually funnel gas to the central parts of disk galaxies. It remains a matter of debate why the distribution of ionized gas along bars and in the circumnuclear regions varies among galaxies. Our goal is to investigate the spatial distribution of star formation (SF) within bars of nearby low-inclination disk galaxies (i<65deg) from the S4G survey. We aim to link the loci of SF to global properties of the hosts (morphological type, stellar mass, gas fraction, and bar-induced gravitational torques), providing constraints for the conditions that regulate SF in bars. We use archival GALEX far- and near-UV imaging for 772 barred galaxies, and for a control sample of 423 non-barred galaxies. We also assemble a compilation of continuum-subtracted H{alpha} images for 433 barred galaxies, 70 of which we produced from ancillary photometry and MUSE and CALIFA integral field unit data cubes. We employ two complementary approaches: i) the analysis of bar (2D) and disk (1D) stacks built from co-added UV images (oriented and scaled with respect to the stellar bars and the extent of disks) of hundreds of galaxies that are binned based on their Hubble stage (T) and bar family; and ii) the visual classification of the morphology of ionized regions (traced from H{alpha} and UV data) in individual galaxies into three main SF classes: A) only circumnuclear SF; B) SF at the bar ends, but not along the bar; and C) SF along the bar. Barred galaxies with active and passive inner rings are likewise classified. Massive, gas-poor, lenticular galaxies typically belong to SF class A; this is probably related to bar-induced quenching of SF in the disk. The distribution of SF class B peaks for early- and intermediate-type spirals; this most likely results from the interplay of gas flow, shocks, and enhanced shear in massive centrally concentrated galaxies with large bar amplitudes (the latter is supported by the lack of a dip in the radial distribution of SF in non-barred galaxies). Late-type gas-rich galaxies with high gravitational torques are mainly assigned to SF class C; we argue that this is a consequence of low shear among the faintest galaxies. In bar stacks of spiral galaxies the UV emission traces the stellar bars and dominates on their leading side, as witnessed in simulations. Among early-type spirals the central UV emission is ~0.5mag brighter in strongly barred galaxies, relative to their weakly barred counterparts; this is probably related to the efficiency of strong bars sweeping the disk gas and triggering central starbursts. On the contrary, in later types the UV emission is stronger at all radii in strongly barred galaxies than in weakly barred and non-barred ones. We also show that the distributions of SF in inner-ringed galaxies are broadly the same in barred and non-barred galaxies, including a UV and H{alpha) deficit in the middle part of the bar; this hints at the effect of resonance rings trapping gas that is no longer funneled inwards. Distinct distributions of SF within bars are reported in galaxies of different morphological types. Star-forming bars are most common among late-type gas-rich galaxies. Bars are important agents in the regulation of SF in disks.
- ID:
- ivo://CDS.VizieR/J/ApJ/647/128
- Title:
- H{alpha} observations of UV-selected galaxies
- Short Name:
- J/ApJ/647/128
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Using Halpha spectra of 114 rest-frame UV-selected galaxies at z~2, we compare inferred star formation rates (SFRs) with those determined from the UV continuum luminosity. After correcting for extinction using standard techniques based on the UV continuum slope, we find excellent agreement between the indicators, with <SFR_Ha_>=31M_{sun}_/yr and <SFR_UV_>=29M_{sun}_/yr. The agreement between the indicators suggests that the UV luminosity is attenuated by a typical factor of ~4.5 (ranging from no attenuation to a factor of 100 for the most obscured object in the sample), in good agreement with estimates of obscuration from X-ray, radio, and mid-IR data.
- ID:
- ivo://CDS.VizieR/J/AJ/155/122
- Title:
- HAZMAT. III. Low-mass stars GALEX photometry
- Short Name:
- J/AJ/155/122
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Low-mass stars are currently the most promising targets for detecting and characterizing habitable planets in the solar neighborhood. However, the ultraviolet (UV) radiation emitted by such stars can erode and modify planetary atmospheres over time, drastically affecting their habitability. Thus, knowledge of the UV evolution of low-mass stars is critical for interpreting the evolutionary history of any orbiting planets. Shkolnik & Barman (2014, J/AJ/148/64) used photometry from the Galaxy Evolution Explorer (GALEX) to show how UV emission evolves for early-type M stars (>0.35 M_{sun}_). In this paper, we extend their work to include both a larger sample of low-mass stars with known ages as well as M stars with lower masses. We find clear evidence that mid- and late-type M stars (0.08-0.35 M_{sun}_) do not follow the same UV evolutionary trend as early-Ms. Lower-mass M stars retain high levels of UV activity up to field ages, with only a factor of 4 decrease on average in GALEX NUV and FUV flux density between young (<50 Myr) and old (~5 Gyr) stars, compared to a factor of 11 and 31 for early-Ms in NUV and FUV, respectively. We also find that the FUV/NUV flux density ratio, which can affect the photochemistry of important planetary biosignatures, is mass- and age-dependent for early-Ms, but remains relatively constant for the mid- and late-type Ms in our sample.
- ID:
- ivo://CDS.VizieR/J/AJ/154/67
- Title:
- HAZMAT. II. Low-mass stars with GALEX UV observations
- Short Name:
- J/AJ/154/67
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The ultraviolet (UV) light from a host star influences a planet's atmospheric photochemistry and will affect interpretations of exoplanetary spectra from future missions like the James Webb Space Telescope. These effects will be particularly critical in the study of planetary atmospheres around M dwarfs, including Earth-sized planets in the habitable zone. Given the higher activity levels of M dwarfs compared to Sun-like stars, time-resolved UV data are needed for more accurate input conditions for exoplanet atmospheric modeling. The Galaxy Evolution Explorer (GALEX) provides multi-epoch photometric observations in two UV bands: near-ultraviolet (NUV; 1771-2831{AA}) and far-ultraviolet (FUV; 1344-1786{AA}). Within 30pc of Earth, there are 357 and 303 M dwarfs in the NUV and FUV bands, respectively, with multiple GALEX observations. Simultaneous NUV and FUV detections exist for 145 stars in both GALEX bands. Our analyses of these data show that low-mass stars are typically more variable in the FUV than the NUV. Median variability increases with later spectral types in the NUV with no clear trend in the FUV. We find evidence that flares increase the FUV flux density far more than the NUV flux density, leading to variable FUV to NUV flux density ratios in the GALEX bandpasses.The ratio of FUV to NUV flux is important for interpreting the presence of atmospheric molecules in planetary atmospheres such as oxygen and methane as a high FUV to NUV ratio may cause false-positive biosignature detections. This ratio of flux density in the GALEX bands spans three orders of magnitude in our sample, from 0.008 to 4.6, and is 1 to 2 orders of magnitude higher than for G dwarfs like the Sun. These results characterize the UV behavior for the largest set of low-mass stars to date.
- ID:
- ivo://CDS.VizieR/J/ApJ/872/17
- Title:
- HAZMAT. V. UV and X-ray evolution of K stars
- Short Name:
- J/ApJ/872/17
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Knowing the high-energy radiation environment of a star over a planet's formation and evolutionary period is critical in determining if that planet is potentially habitable and if any biosignatures could be detected, as UV radiation can severely change or destroy a planet's atmosphere. Current efforts for finding a potentially habitable planet are focused on M stars, yet K stars may offer more habitable conditions due to decreased stellar activity and more distant and wider habitable zones (HZs). While M star activity evolution has been observed photometrically and spectroscopically, there has been no dedicated investigation of K star UV evolution. We present the first comprehensive study of the near-UV, far-UV, and X-ray evolution of K stars. We used members of young moving groups and clusters ranging in age from 10 to 625Myr combined with field stars and their archived GALEX UV and ROSAT X-ray data to determine how the UV and X-ray radiation evolve. We find that the UV and X-ray flux incident on an HZ planet is 5-50 times lower than that of HZ planets around early-M stars and 50-1000 times lower than those around late-M stars, due to both an intrinsic decrease in K dwarf stellar activity occurring earlier than for M dwarfs and the more distant location of the K dwarf HZ.
- ID:
- ivo://CDS.VizieR/J/AJ/119/486
- Title:
- HDF-S: STIS imaging
- Short Name:
- J/AJ/119/486
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the imaging observations made with the Space Telescope Imaging Spectrograph (STIS) of the Hubble Deep Field South. The field was imaged in four bandpasses: a clear CCD bandpass for 156ks, a long-pass filter for 22-25ks/pix typical exposure, a near-UV bandpass for 23ks, and a far-UV bandpass for 52ks. The clear, visible image is the deepest observation ever made in the UV-optical wavelength region, reaching a 10{sigma}AB magnitude of 29.4 for an object of area 0.2arcsec^2^. The field contains QSO J2233-606, the target of the STIS spectroscopy, and extends 50"x50" for the visible images, and 25"x25" for the ultraviolet images. We present the images, catalog of objects, and galaxy counts obtained in the field.
- ID:
- ivo://CDS.VizieR/J/MNRAS/458/84
- Title:
- Host galaxies of Superluminous Supernovae
- Short Name:
- J/MNRAS/458/84
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present Hubble Space Telescope (HST) Wide Field Camera 3 UV and near-IR (nIR) imaging of 21 Superluminous Supernovae (SLSNe) host galaxies, providing a sensitive probe of star formation and stellar mass within the hosts. Comparing the photometric and morphological properties of these host galaxies with those of core-collapse supernovae (CCSNe) and long-duration gamma-ray bursts (LGRBs), we find SLSN hosts are fainter and more compact at both UV and nIR wavelengths, in some cases we barely recover hosts with absolute magnitude around M_V_~=-14. With the addition of ground based optical observations and archival results, we produce spectral energy distribution fits to these hosts, and show that SLSN hosts possess lower stellar mass and star formation rates. This is most pronounced for the hydrogen deficient Type-I SLSN hosts, although Type-II H-rich SLSN host galaxies remain distinct from the bulk of CCSNe, spanning a remarkably broad range of absolute magnitudes, with ~30 per cent of SLSNe-II arising from galaxies fainter than M_nIR_~-14. The detection of our faintest SLSN hosts increases the confidence that SLSNe-I hosts are distinct from those of LGRBs in star formation rate and stellar mass, and suggests that apparent similarities in metallicity may be due to the limited fraction of hosts for which emission line metallicity measurements are feasible. The broad range of luminosities of SLSN-II hosts is difficult to describe by metallicity cuts, and does not match the expectations of any reasonable UV-weighted luminosity function, suggesting additional environmental constraints are likely necessary to yield hydrogen rich SLSNe.
