- ID:
- ivo://CDS.VizieR/J/ApJ/671/1227
- Title:
- Ly{alpha} galaxies at z~4.5
- Short Name:
- J/ApJ/671/1227
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a catalog of 59 z~4.5 Ly{alpha}-emitting galaxies spectroscopically confirmed in a campaign of Keck DEIMOS follow-up observations to candidates selected in the Large Area Ly{alpha} (LALA) narrowband imaging survey. We targeted 97 candidates for spectroscopic follow-up; by accounting for the variety of conditions under which we performed spectroscopy, we estimate a selection reliability of ~76%. Together with our previous sample of Keck LRIS confirmations, the 59 sources confirmed herein bring the total catalog to 73 spectroscopically confirmed z~4.5 Ly{alpha}-emitting galaxies in the ~0.7deg^2^ covered by the LALA imaging.
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Search Results
- ID:
- ivo://CDS.VizieR/J/ApJ/886/19
- Title:
- Ly{alpha} obs. of low-mass stars Ross 825 & 1044
- Short Name:
- J/ApJ/886/19
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The discovery of habitable zone (HZ) planets around low-mass stars has highlighted the need for a comprehensive understanding of the radiation environments in which such planets reside. Of particular importance is knowledge of the far-ultraviolet (FUV) radiation, as low-mass stars are typically much more active than solar-type stars and the proximity of their HZs can be one-tenth the distance. The vast majority of the flux emitted by low-mass stars at FUV wavelengths occurs in the Ly{alpha} line at 1216 {AA}. However, measuring a low-mass star's Ly{alpha} emission directly is almost always impossible because of the contaminating effects of interstellar hydrogen and geocoronal airglow. We observed Ross825 (K3) and Ross1044 (M0), two stars with exceptional radial velocities, with the Space Telescope Imaging Spectrograph on board the Hubble Space Telescope. Their radial velocities resulted in significant line shifts, allowing for a more complete view of their Ly{alpha} line profiles. We provide an updated relation between effective temperature and Ly{alpha} flux using Gaia DR2 astrometry as well as updated, model-independent relationships between Ly{alpha} flux and UV flux measurements from the Galaxy Evolution Explorer (GALEX) for low-mass stars. These new relations, in combination with GALEX's considerable spatial coverage, provide substantial predictive power for the Ly{alpha} environments for thousands of nearby, low-mass stars.
- ID:
- ivo://CDS.VizieR/J/ApJ/844/171
- Title:
- Ly{alpha} profile in 43 Green Pea galaxies
- Short Name:
- J/ApJ/844/171
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We studied Lyman-{alpha} (Ly{alpha}) escape in a statistical sample of 43 Green Peas with HST/COS Ly{alpha} spectra. Green Peas are nearby star-forming galaxies with strong [OIII]{lambda}5007 emission lines. Our sample is four times larger than the previous sample and covers a much more complete range of Green Pea properties. We found that about two-thirds of Green Peas are strong Ly{alpha} line emitters with rest-frame Ly{alpha} equivalent width >20{AA}. The Ly{alpha} profiles of Green Peas are diverse. The Ly{alpha} escape fraction, defined as the ratio of observed Ly{alpha} flux to intrinsic Ly{alpha} flux, shows anti-correlations with a few Ly{alpha} kinematic features-both the blue peak and red peak velocities, the peak separations, and the FWHM of the red portion of the Ly{alpha} profile. Using properties measured from Sloan Digital Sky Survey optical spectra, we found many correlations-the Ly{alpha} escape fraction generally increases at lower dust reddening, lower metallicity, lower stellar mass, and higher [OIII]/[OII] ratio. We fit their Ly{alpha} profiles with the HI shell radiative transfer model and found that the Ly{alpha} escape fraction is anti-correlated with the best-fit N_HI_. Finally, we fit an empirical linear relation to predict f_esc_^Ly{alpha}^ from the dust extinction and Ly{alpha} red peak velocity. The standard deviation of this relation is about 0.3dex. This relation can be used to isolate the effect of intergalactic medium (IGM) scatterings from Ly{alpha} escape and to probe the IGM optical depth along the line of sight of each z>7 Ly{alpha} emission-line galaxy in the James Webb Space Telescope era.
- ID:
- ivo://CDS.VizieR/J/A+A/498/13
- Title:
- Lyman-{alpha} emitters from redshifts z~2-3
- Short Name:
- J/A+A/498/13
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Narrow-band surveys to detect Ly{alpha} emitters are powerful tools for identifying high, and very high, redshift galaxies. Although samples are increasing at redshifts z=3-6, the nature of these galaxies is still poorly known. The number of galaxies detected at redshifts below z~3 are also small. We study the properties of z=2.25 Ly{alpha} emitters and compare them with those of z>3 Ly{alpha} emitters We present narrow-band imaging made with the MPG/ESO 2.2m telescope and the WFI (Wide Field Imager) detector. Using this data, we have searched for emission-line objects. We find 170 candidate typical Ly{alpha} emitters and 17 candidates that we regard as high UV-transmission Ly{alpha} emitters. We have derived the magnitudes of these objects in 8 photometric bands from u* to K_s_, and studied whether they have X-ray and/or radio counterparts.
- ID:
- ivo://CDS.VizieR/J/ApJ/765/47
- Title:
- Lyman-break galaxies and LAEs at z~3
- Short Name:
- J/ApJ/765/47
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We investigate the contribution of star-forming galaxies to the ionizing background at z~3, building on previous work based on narrowband (NB3640) imaging in the SSA22a field. We use new Keck/LRIS spectra of Lyman break galaxies (LBGs) and narrowband-selected Ly{alpha} emitters (LAEs) to measure redshifts for 16 LBGs and 87 LAEs at z>3.055, such that our NB3640 imaging probes the Lyman-continuum (LyC) region. When we include the existing set of spectroscopically confirmed LBGs, our total sample with z>3.055 consists of 41 LBGs and 91 LAEs, of which 9 LBGs and 20 LAEs are detected in our NB3640 image. With our combined imaging and spectroscopic data sets, we critically investigate the origin of NB3640 emission for detected LBGs and LAEs. We remove from our samples three LBGs and three LAEs with spectroscopic evidence of contamination of their NB3640 flux by foreground galaxies and statistically model the effects of additional, unidentified foreground contaminants. The resulting contamination and LyC-detection rates, respectively, are 62%+/-13% and 8%+/-3% for our LBG sample, and 47%+/-10% and 12%+/-2% for our LAE sample. The corresponding ratios of non-ionizing UV to LyC flux density, corrected for intergalactic medium (IGM) attenuation, are 18.0^+34.8^_-7.4_ for LBGs and 3.7^+2.5^_-1.1_ for LAEs. We use these ratios to estimate the total contribution of star-forming galaxies to the ionizing background and the hydrogen photoionization rate in the IGM, finding values larger than, but consistent with, those measured in the Ly{alpha} forest. Finally, the measured UV to LyC flux-density ratios imply model-dependent LyC escape fractions of f^LyC^_esc_~5%-7% for our LBG sample and f^LyC^_esc_~10%-30% for our fainter LAE sample.
- ID:
- ivo://CDS.VizieR/J/MNRAS/380/986
- Title:
- Lyman-break galaxies from GALEX
- Short Name:
- J/MNRAS/380/986
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Ultraviolet (UV) galaxies have been selected from the Galaxy Evolution Explorer deep imaging survey. The presence of a far-UV (FUV) drop-out in their spectral energy distributions (SEDs) proved to be a very complete (83.3 per cent) but not very efficient (21.4 per cent) tool for identifying Lyman break galaxies (LBGs) at z~1. In this paper, we explore the physical properties of these galaxies and how they contribute to the total star formation rate (SFR).
- ID:
- ivo://CDS.VizieR/J/ApJ/736/18
- Title:
- Lyman-continuum emission at z~3 in SSA22 field
- Short Name:
- J/ApJ/736/18
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of an ultradeep, narrowband imaging survey for Lyman-continuum (LyC) emission at z~3 in the SSA22a field. We employ a custom narrowband filter centered at {lambda}=3640{AA} (NB3640), which probes the LyC region for galaxies at z>=3.06. We also analyze new and archival NB4980 imaging tuned to the wavelength of the Ly{alpha} emission line at z=3.09, and archival broadband B, V, and R images of the non-ionizing UV continuum. Our NB3640 images contain 26 z>=3.06 Lyman break galaxies (LBGs) as well as a set of 130 Ly{alpha} emitters (LAEs), identified by their excess NB4980 flux relative to the BV continuum. Six LBGs and 28 LAEs are detected in the NB3640 image. LBGs appear to span a range of NB3640-R colors, while LAEs appear bimodal in their NB3640-R properties. We estimate average UV-to-LyC flux density ratios.
- ID:
- ivo://CDS.VizieR/J/ApJ/724/1389
- Title:
- Mapping the diffuse UV sky with GALEX
- Short Name:
- J/ApJ/724/1389
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a map of the diffuse ultraviolet cosmic background in two wavelength bands (FUV: 1530{AA} and NUV: 2310{AA}) over almost 75% of the sky using archival data from the Galaxy Evolution Explorer (GALEX) mission. Most of the diffuse flux is due to dust-scattered starlight and follows a cosecant law with slopes of 545 photons/cm^2^/s/sr/{AA} and 433 photons/cm^2^/s/sr/{AA} in the FUV and NUV bands, respectively. There is a strong correlation with the 100um Infrared Astronomy Satellite (IRAS) flux with an average UV/IR ratio of 300 photons/cm^2^/s/sr/{AA}/(MJy/sr) in the FUV band and that of 220 photons/cm^2^/s/sr/{AA}/(MJy/sr) in the NUV band but with significant variations over the sky. In addition to the large-scale distribution of the diffuse light, we note a number of individual features including bright spots around the hot stars Spica and Achernar.
- ID:
- ivo://CDS.VizieR/J/ApJS/173/673
- Title:
- M dwarf UV flares in GALEX
- Short Name:
- J/ApJS/173/673
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the preliminary results from implementing a new software tool that enables inspection of time-tagged photon data for the astronomical sources contained within individual GALEX ultraviolet (UV) images of the sky. We have inspected the photon data contained within 1802 GALEX images to reveal rapid, short-term (<~500s) UV source variability in the form of stellar "flares." The mean associated change in near-UV (NUV) magnitude due to this flaring activity is 2.7+/-0.3mag. A list of 49 new UV variable star candidates is presented (associated with 52 separate flare events), together with their associated Sloan Digital Sky Survey (SDSS) photometric magnitudes. From these data we can associate the main source of these UV flare events with magnetic activity on M dwarf stars. Photometric parallaxes have been determined for 32 of these sources, placing them at distances ranging from approximately 25 to 1000pc. The average UV flare energy for these flare events is 2.5x10^30^ergs, which is of a similar energy to that of U-band, X-ray, and EUV flares observed on many local M dwarf stars. We have found that stars of classes M0 to M5 flare with energies spanning a far larger range and with an energy approximately 5 times greater than those of later (M6 to M8) spectral type.
- ID:
- ivo://CDS.VizieR/J/A+A/641/A118
- Title:
- Mean rest-UV spectra of Ly{alpha} emitters at z>3
- Short Name:
- J/A+A/641/A118
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We investigate the ultraviolet (UV) spectral properties of faint Lyman{alpha} emitters (LAEs) in the redshift range 2.9<=z<=4.6 and provide material to prepare future observations of the faint Universe. We use data from the MUSE Hubble Ultra Deep Survey to construct mean rest-frame spectra of continuum-faint (median M_UV_ of -18 and down to M_UV_ of -16), low stellar mass (median value of 10^8.4^ and down to 10^7^ solar masses) LAEs at redshift z>3. We compute various averaged spectra of LAEs sub-sampled on the basis of their observational (e.g., Ly{alpha} strength, UV magnitude and spectral slope) and physical (e.g., stellar mass and star-formation rate) properties. We search for UV spectral features other than Ly{alpha}, such as higher-ionization nebular emission lines and absorption features. We successfully observe the OIII]{lambda}1666 and [CIII]{lambda}1907+CIII]{lambda}1909 collisionally excited emission lines and the HeII{lambda}1640 recombination feature, as well as the resonant CIV{lambda}1548,1551 doublet either in emission or P-Cygni. We compare the observed spectral properties of the different mean spectra and find the emission lines to vary with the observational and physical properties of the LAEs. In particular, the mean spectra of LAEs with larger Ly{alpha} equivalent widths, fainter UV magnitudes, bluer UV spectral slopes and lower stellar masses show the strongest nebular emission. The line ratios of these lines are similar to those measured in the spectra of local metal-poor galaxies, while their equivalent widths are weaker compared to the handful of extreme values detected in individual spectra of z>2 galaxies. This suggests that weak UV features are likely ubiquitous in high z, low-mass and faint LAEs. We publicly release the stacked spectra as they can serve as empirical templates for the design of future observations, such as those with the James Webb Space Telescope and the Extremely Large Telescope.
