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 greater than or equal to 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 f sub( LyC)/f sub( UV) < 0.08 from stacking LAEs and f sub( LyC)/f sub( 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.
Abstract
We conducted a deep spectroscopic survey, named SSA22-HIT, in the SSA22 field with the DEep Imaging MultiObject Spectrograph (DEIMOS) on the Keck telescope, designed to tomographically map ...high-
z
H
i
gas through analysis of Ly
α
absorption in background galaxies’ spectra. In total, 198 galaxies were spectroscopically confirmed at 2.5 <
z
< 6 with a few low-
z
exceptions in the 26 × 15 arcmin
2
area, of which 148 were newly determined in this study. Our redshift measurements were merged with previously confirmed redshifts available in the 34 × 27 arcmin
2
area of the SSA22 field. This compiled catalog containing 730 galaxies of various types at
z
> 2 is useful for various applications, and it is made publicly available. Our SSA22-HIT survey has increased by approximately twice the number of spectroscopic redshifts of sources at
z
> 3.2 in the observed field. From a comparison with publicly available redshift catalogs, we show that our compiled redshift catalog in the SSA22 field is comparable to those among major extragalactic survey fields in terms of a combination of wide area and high surface number density of objects at
z
> 2. About 40% of the spectroscopically confirmed objects in SSA22-HIT show reasonable quality of spectra in the wavelengths shorter than Ly
α
when a sufficient amount of smoothing is adopted. Our data set enables us to make the H
i
tomographic map at
z
≳ 3, which we present in a parallel study.
Abstract
We report on the results of deep and wide-field (1.1 deg2) narrow-band observations with Subaru/Hyper Suprime-Cam (HSC) of a field around a hyperluminous QSO (HLQSO), HS$\, 1549+$1919, ...residing in a protocluster at z = 2.84, to map the large-scale structure of Lyα emitters (LAEs). One HSC pointing enables us to detect 3490 LAEs and 76 extended Lyα blobs (LABs), probing diverse environments from voids to protoclusters. The HLQSO is found to be near the center of the protocluster, which corresponds to the intersection of $\sim \,$100 comoving Mpc-scale structures of LAEs. LABs are basically distributed along the large-scale structure, with larger ones particularly clustering around the HLQSO, confirming a previously noted tendency of LABs to prefer denser environments. Moreover, the shapes of LABs near the HLQSO appear to be aligned with the large-scale structure. Finally, a deep Lyα image reveals a diffuse Lyα nebula along a filamentary structure with no luminous UV/sub-mm counterpart. We suggest that the diffuse nebula is due to a cold filament with high clumping factor illuminated by the QSO, with the required high clumpiness provided by unresolved residing halos of mass $\le 10^{9-10}\, M_\odot$.
We present the results of deep near-infrared imaging observations of the
$z=3.1$
proto-cluster region in the SSA 22a field taken by MOIRCS mounted on the Subaru Telescope. We observed a 21.7 arcmin
...$^2$
field to depths of
$J=$
24.5,
$H=$
24.3, and
$K=$
23.9 (5
$\sigma$
). We examined the distribution of the
$K$
-selected galaxies at
$z \sim 3$
by using a simple color cut for distant red galaxies (DRGs) as well as a photometric-redshift selection technique. The marginal density excess of DRGs and the photo-
$z$
selected objects were found around the two most luminous Ly
$\alpha$
blobs (LABs). We investigated the correlation between the
$K$
-selected objects and the LABs, and found that several galaxies with stellar mass,
$M_* = 10^{9}$
–
$10^{11} M_\odot$
, exist in the vicinity of LABs, especially around the two most luminous ones. We also found that 7 of the 8LABs in the field have plausible
$K_{\rm s}$
-band counterparts, and the sum of the stellar mass possibly associated with LABs correlates with their luminosity and surface brightness, which implies that the origin of Ly
$\alpha$
emission may be closely correlated with their previous star-formation phenomena.
We conduct a deep narrowband imaging survey of 13 Lyα blobs (LABs) located in the SSA22 proto-cluster at z ∼ 3.1 in the C iv and He ii emission lines in an effort to constrain the physical process ...powering the Lyα emission in LABs. Our observations probe down to unprecedented surface brightness (SB) limits of (2.1–3.4) × 10{sup −18} erg s{sup −1} cm{sup −2} arcsec{sup −2} per 1 arcsec{sup 2} aperture (5σ) for the He ii λ1640 and C iv λ1549 lines, respectively. We do not detect extended He ii and C iv emission in any of the LABs, placing strong upper limits on the He ii/Lyα and C iv/Lyα line ratios, of 0.11 and 0.16, for the brightest two LABs in the field. We conduct detailed photoionization modeling of the expected line ratios and find that, although our data constitute the deepest ever observations of these lines, they are still not deep enough to rule out a scenario where the Lyα emission is powered by the ionizing radiation from an obscured active galactic nucleus. Our models can accommodate He ii/Lyα and C iv/Lyα ratios as low as ≃0.05 and ≃0.07, respectively, implying that one needs to reach SB as low as (1–1.5) × 10{sup −18} erg s{sup −1} cm{sup −2} arcsec{sup −2} (at 5σ) in order to rule out a photoionization scenario. These depths will be achievable with the new generation of image-slicing integral field units such as the Multi Unit Spectroscopic Explorer (MUSE) on VLT and the Keck Cosmic Web Imager (KCWI). We also model the expected He ii/Lyα and C iv/Lyα in a different scenario, where Lyα emission is powered by shocks generated in a large-scale superwind, but find that our observational constraints can only be met for shock velocities v{sub s} ≳ 250 km s{sup −1}, which appear to be in conflict with recent observations of quiescent kinematics in LABs.
We present a Herschel/Spectral and Photometric Imaging Receiver (SPIRE) survey of three protoclusters at z = 2–3 (2QZCluster, HS1700, SSA22). Based on the SPIRE colours (S
350/S
250 and S
500/S
350) ...of 250 μm sources, we selected high-redshift dusty star-forming galaxies potentially associated with the protoclusters. In the 2QZCluster field, we found a 4σ overdensity of six SPIRE sources around 4.5 arcmin (∼2.2 Mpc) from a density peak of H α emitters at z = 2.2. In the HS1700 field, we found a 5σ overdensity of eight SPIRE sources around 2.1 arcmin (∼1.0 Mpc) from a density peak of Lyman-break galaxies at z = 2.3. We did not find any significant overdensities in SSA22 field, but we found three 500 μm sources are concentrated 3 arcmin (∼1.4 Mpc) east to the Ly α emitters overdensity. If all the SPIRE sources in these three overdensities are associated with protoclusters, the inferred star formation rate densities are 103–104 times higher than the average value at the same redshifts. This suggests that dusty star formation activity could be very strongly enhanced in z ∼ 2–3 protoclusters. Further observations are needed to confirm the redshifts of the SPIRE sources and to investigate what processes enhance the dusty star formation activity in z ∼ 2–3 protoclusters.
ABSTRACT
In the SSA22 field which exhibits a large-scale proto-cluster at z = 3.1, we carried out a spectroscopic survey for Lyman Break Galaxies (LBGs) with the VLT/VIMOS and identified 78 confident ...LBGs at z = 2.5–4. We stacked their spectra in the observer’s frame by using a sophisticated method. Analysing the composite spectrum, we have revealed that the large-scale proto-cluster at z = 3.1 has a strong H i absorption dip of rest-frame equivalent width of −1.7 Å. Another strong absorption dip found at z = 3.28 is associated with a modestly high-density LBG peak, similar to that at z = 3.1. We have also detected an H i transparency peak at z = 2.98 in the composite spectrum, coincident with a void in the LBG distribution. In this paper, we also investigated the relation between LBGs, H i gas, and active galactic nuclei (AGNs) at z = 3–4 in the SSA22 field. Two AGNs at z = 3.353 and 3.801 are, respectively, associated with the LBG concentration of an overdensity factor δLBG ≃ 2 in the present statistics. Another structure at z = 3.453 is remarkable: 20 comoving Mpc-scale dense H i gas which is not associated with any apparent LBG overdensity but involving a pair of AGNs. Such structure may be a new type of the AGN–matter correlation. If the inhomogeneous structures over a comoving Gpc scale found in this paper are confirmed with sufficient statistics in the future, the SSA22 field will become a key region to test the standard cold dark matter structure formation scenario.
We present both the observations and the data reduction procedures of the Subaru COSMOS 20 project, an optical imaging survey of the HST COSMOS field, carried out by using Suprime-Cam on the Subaru ...Telescope with the following 20 optical filters: six broad-band (B, g′, V, r′, i′, and z′), two narrow-band (NB711 and NB816), and 12 intermediate-band filters (IA427, IA464, IA484, IA505, IA527, IA574, IA624, IA679, IA709, IA738, IA767, and IA827). Part of this project is described in Taniguchi et al. (2007, ApJS, 172, 9) and Capak et al. (2007, ApJS, 172, 99) for the six broad-band and one narrow-band (NB816) filter data. In this paper, we present details of the observations and data reduction for the remaining 13 filters (the 12 IA filters and NB711). In particular, we describe the accuracy of both the photometry and astrometry in all the filter bands. We also present the optical properties of the Suprime-Cam IA filter system in appendices.
ABSTRACT We have observed the dust continuum of 10 z = 3.1 Lyman break galaxies with the Atacama Large Millimeter/submillimeter Array at ∼450 mas resolution in Band 7. We detect and resolve the 870 m ...emission in one of the targets with a flux density of S870 = 192 57 Jy, and measure a stacked 3 signal of S870 = 67 23 Jy for the remaining nine. The total infrared luminosities are L8-1000 = (8.4 2.3) × 1010 L for the detection and L8-1000 = (2.9 0.9) × 1010 L for the stack. With Hubble Space Telescope Advanced Camera for Surveys I-band imaging we map the rest-frame UV emission on the same scale as the dust, effectively resolving the "infrared excess" (IRX = LFIR/LUV) in a normal galaxy at z = 3. Integrated over the galaxy we measure IRX = 0.56 0.15, and the galaxy-averaged UV slope is β = −1.25 0.03. This puts the galaxy a factor of ∼10 below the IRX-β relation for local starburst nuclei of Meurer et al. However, IRX varies by more than a factor of 3 across the galaxy, and we conclude that the complex relative morphology of the dust relative to UV emission is largely responsible for the scatter in the IRX-β relation at high-z. A naive application of a Meurer-like dust correction based on the UV slope would dramatically overestimate the total star formation rate, and our results support growing evidence that when integrated over the galaxy, the typical conditions in high-z star-forming galaxies are not analogous to those in the local starburst nuclei used to establish the Meurer relation.
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