- 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.
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Search Results
- ID:
- ivo://CDS.VizieR/J/ApJ/810/107
- Title:
- Lyman break galaxies and LAEs HST photometry
- Short Name:
- J/ApJ/810/107
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present U_336_V_606_J_125_H_160_ follow-up Hubble Space Telescope (HST) observations of 16 z~3 candidate Lyman continuum (LyC) emitters in the HS1549+1919 field. With these data, we obtain high spatial-resolution photometric redshifts of all sub-arcsecond components of the LyC candidates in order to eliminate foreground contamination and identify robust candidates for leaking LyC emission. Of the 16 candidates, we find one object with a robust LyC detection that is not due to foreground contamination. This object (MD5) resolves into two components; we refer to the LyC-emitting component as MD5b. MD5b has an observed 1500 {AA} to 900 {AA} flux-density ratio of (F_UV_/F_LyC_)_obs_=4.0+/-2.0, compatible with predictions from stellar population synthesis models. Assuming minimal IGM absorption, this ratio corresponds to a relative (absolute) escape fraction of f_esc,rel_^MD5b^=75%-100% (f_esc,abs_^MD5b^=14%-19%). The stellar population fit to MD5b indicates an age of <~50 Myr, which is in the youngest 10% of the HST sample and the youngest third of typical z~3 Lyman break galaxies, and may be a contributing factor to its LyC detection. We obtain a revised, contamination-free estimate for the comoving specific ionizing emissivity at z=2.85, indicating (with large uncertainties) that star-forming galaxies provide roughly the same contribution as QSOs to the ionizing background at this redshift. Our results show that foreground contamination prevents ground-based LyC studies from obtaining a full understanding of LyC emission from z~3 star-forming galaxies. Future progress in direct LyC searches is contingent upon the elimination of foreground contaminants through high spatial-resolution observations, and upon acquisition of sufficiently deep LyC imaging to probe ionizing radiation in high-redshift galaxies.
- ID:
- ivo://CDS.VizieR/J/ApJ/592/728
- Title:
- Lyman break galaxies at redshift z~3
- Short Name:
- J/ApJ/592/728
- Date:
- 04 Dec 2021
- Publisher:
- CDS
- Description:
- We present the basic data for a large ground-based spectroscopic survey for z~3 Lyman break galaxies (LBGs), photometrically selected using rest-UV colors from very deep images in 17 high Galactic latitude fields. The total survey covers an area of 0.38deg^2^ and includes 2347 photometrically selected candidate LBGs to an apparent {R}_AB_ magnitude limit of 25.5. Approximately half of these objects have been observed spectroscopically using the Keck telescopes, yielding 940 redshifts with <z>=2.96+/-0.29. We discuss the images, photometry, target selection, and spectroscopic program in some detail and present catalogs of the photometric and spectroscopic data, made available in electronic form. We discuss the general utility of conducting nearly volume-limited redshift surveys in prescribed redshift intervals using judicious application of photometric preselection.
- ID:
- ivo://CDS.VizieR/J/ApJ/697/1410
- Title:
- Lyman break galaxies at z~1.8-2.8
- Short Name:
- J/ApJ/697/1410
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A photometric sample of ~8000 V<25.3 candidate Lyman break galaxies (LBGs) has been selected by combining Subaru/Suprime-Cam BVRCi'z' optical data with deep GALEX/NUV imaging of the Subaru Deep Field. Follow-up spectroscopy confirmed 24 LBGs at 1.5<~z<~2.7. Among the optical spectra, 12 have Ly{alpha} emission with rest-frame equivalent widths of ~5-60{AA}. The success rate for identifying LBGs as NUV-dropouts at 1.5<z<2.7 is 86%. The rest-frame UV (1700{AA}) luminosity function (LF) is constructed from the photometric sample with corrections for stellar contamination and z<1.5 interlopers (lower limits). The LF is 1.7+/-0.1 (1.4+/-0.1 with a hard upper limit on stellar contamination) times higher than those of z~2 BXs and z~3 LBGs.
- ID:
- ivo://CDS.VizieR/J/ApJ/736/48
- Title:
- 48 Lyman break galaxies at z~3 in HUDF
- Short Name:
- J/ApJ/736/48
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present evidence for spatially extended low surface brightness emission around Lyman break galaxies (LBGs) in the V-band image of the Hubble Ultra Deep Field, corresponding to the z~3 rest-frame far-UV (FUV) light, which is a sensitive measure of star formation rates (SFRs). We find that the covering fraction of molecular gas at z~3 is not adequate to explain the emission in the outskirts of LBGs, while the covering fraction of neutral atomic-dominated hydrogen gas at high redshift is sufficient. We develop a theoretical framework to connect this emission around LBGs to the expected emission from neutral HI gas, i.e., damped Ly{alpha} systems (DLAs), using the Kennicutt-Schmidt (KS) relation. Working under the hypothesis that the observed FUV emission in the outskirts of LBGs is from in situ star formation in atomic-dominated hydrogen gas, the results suggest that the SFR efficiency in such gas at z~3 is between factors of 10 and 50 lower than predictions based on the local KS relation. The total SFR density in atomic-dominated gas at z~3 is constrained to be ~10% of that observed from the inner regions of LBGs. In addition, the metals produced by in situ star formation in the outskirts of LBGs yield metallicities comparable to those of DLAs, which is a possible solution to the "Missing Metals" problem for DLAs. Finally, the atomic-dominated gas in the outskirts of galaxies at both high and low redshifts has similar reduced SFR efficiencies and is consistent with the same power law.
- 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/MNRAS/431/2080
- Title:
- Lyman break galaxies (LBG) at z~1
- Short Name:
- J/MNRAS/431/2080
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- After carefully cross-identifying previously discovered - and selected by the Galaxy Evolution Explorer (GALEX) - Lyman break galaxy (LBG) candidates one-to-one with their optical counterparts in the field of the Chandra Deep Field South (CDF-S), we re-estimate their photometric redshifts using multiwavelength data from ultraviolet and optical to near-infrared. Considering their re-estimated photometric redshifts and spectral energy distributions, we refine a new updated sample of 383 LBGs at 0.7<~z<~1.4, with two confirmed active galactic nuclei being excluded. There are 260 and 111 LBGs classified as starburst and irregular types, respectively. The ages of the LBGs span from several Myr to 1.5Gyr with a median of ~50Myr. Their dust-corrected star formation rates (SFRs) and stellar masses (M*) are 4-220M_{sun}_/yr and from 2.3x10^8^ to 4x10^11^M_{sun}_, with median values of ~25M_{sun}_/yr and ~10^10^M_{sun}_. The rest-frame far-ultraviolet luminosity function of the LBGs is presented with the best-fitting Schechter parameters of {alpha}=-1.61+/-0.40, M*=-20.40+/-0.22 and {phi}*=(0.89+/-0.30)x10^-3^/Mpc^3^/dex. LBGs of irregular types are mainly distributed along the main sequence of star-forming galaxies, while most LBGs of starburst types are located in the starburst region. Together with previous studies, we suggest that the star formation mode for LBGs at z>3 is mainly starburst, and that it evolves to be more significant to the quenching mode after z~3. A downsizing effect is clearly found, and we discuss the physical implications and comparisons with previous studies in detail. LBGs with larger SFRs are, on average, more compact. In the rest-frame colour (U-B)-M* diagram, LBGs are distributed in the `blue' cloud. We suggest that LBGs might evolve along the blue cloud from later to earlier types. The Hubble Space Telescope images in F606W (V band) and F850LP (z band) are taken from the Galaxy Evolution from Morphology and SEDs (GEMS) survey and the Great Observatories Origins Deep Survey South (GOODS-S) for morphological studies of LBGs. sextractor and galfit are applied in order to obtain their morphological parameters. We establish an image gallery of 277 LBGs, commonly detected in both bands, by visually classifying individual LBGs into the following types: chain, spiral, tadpole, bulge and clump. We define a morphological sample of 142 LBGs with reliable results of Sersic indices and sizes in both bands. We find that LBGs at z~1 are dominated by disc-like galaxies, with median sizes of 2.34 and 2.68kpc in F606W and F850LP, respectively. The correlations between the photometric and morphological properties of LBGs are investigated. Strong correlations between their half-light radii and M* (i.e. size-stellar mass relations) are found in both bands. We discuss the physical connections between the correlations and the downsizing effect.
- ID:
- ivo://CDS.VizieR/J/ApJ/703/2033
- Title:
- Lyman-break galaxies (LBG) in the HUDF
- Short Name:
- J/ApJ/703/2033
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a sample of 407 z~3 Lyman break galaxies (LBGs) to a limiting isophotal u-band magnitude of 27.6mag in the Hubble Ultra Deep Field. The LBGs are selected using a combination of photometric redshifts and the u-band drop-out technique enabled by the introduction of an extremely deep u-band image obtained with the Keck I telescope and the blue channel of the Low Resolution Imaging Spectrometer. The Keck u-band image, totaling 9hr of integration time, has a 1{sigma} depth of 30.7mag/arcsec^2^, making it one of the most sensitive u-band images ever obtained. The u-band image also substantially improves the accuracy of photometric redshift measurements of ~50% of the z~3 LBGs, significantly reducing the traditional degeneracy of colors between z~3 and z~0.2 galaxies.
- 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/MNRAS/465/316
- Title:
- Lyman continuum LAEs and LBGs in SSA22 field
- Short Name:
- J/MNRAS/465/316
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the largest to date sample of hydrogen Lyman continuum (LyC) emitting galaxy candidates at any redshift, with 18 Lyman {alpha} emitters (LAEs) and seven Lyman break galaxies (LBGs), obtained from the SSA22 field with Subaru/Suprime-Cam. The sample is based on the 159 LAEs and 136 LBGs observed in the field, all with spectroscopically confirmed redshifts, and these LyC candidates are selected as galaxies with counterparts in a narrow-band filter image which traces LyC at z>=3.06. Many LyC candidates show a spatial offset between the rest-frame non-ionizing ultraviolet (UV) detection and the LyC-emitting substructure or between the Ly{alpha} emission and LyC. The possibility of foreground contamination complicates the analysis of the nature of LyC emitters, although statistically it is highly unlikely that all candidates in our sample are contaminated by foreground sources. Many viable LyC LAE candidates have flux density ratios inconsistent with standard models, while also having too blue UV slopes to be foreground contaminants. Stacking reveals no significant LyC detection, suggesting that there is a dearth of objects with marginal LyC signal strength, perhaps due to a bimodality in the LyC emission. The foreground contamination corrected 3{sigma} upper limits of the observed average flux density ratios are fLyC/fUV < 0.08 from stacking LAEs and f_LyC_/f_UV_<0.02 from stacking LBGs. There is a sign of a positive correlation between LyC and Ly{alpha}, suggesting that both types of photons escape via a similar mechanism. The LyC detection rate among protocluster LBGs is seemingly lower compared to the field.
