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.
We present spatial correlations of galaxies and IGM neutral hydrogen H i in the COSMOS/UltraVISTA 1.62 deg2 field. Our data consist of 13,415 photo-z galaxies at z ∼ 2-3 with and the Ly forest ...absorption lines in the background quasar spectra selected from SDSS data with no signature of damped Ly system contamination. We estimate a galaxy overdensity δgal in an impact parameter of 2.5 (proper) Mpc, and calculate the Ly forest fluctuations whose negative values correspond to the strong Ly forest absorption lines. We identify weak evidence of an anti-correlation between δgal and with a Spearman's rank correlation coefficient of −0.39 suggesting that the galaxy overdensities and the Ly forest absorption lines positively correlate in space at the ∼90% confidence level. This positive correlation indicates that high-z galaxies exist around an excess of H i gas in the Ly forest. We find four cosmic volumes, dubbed Aobs, Bobs, Cobs, and Dobs, that have extremely large (small) values of δgal 0.8 (−1) and , three of which, Bobs-Dobs, significantly depart from the δgal- correlation, and weaken the correlation signal. We perform cosmological hydrodynamical simulations and compare with our observational results. Our simulations reproduce the δgal- correlation, agreeing with the observational results. Moreover, our simulations have model counterparts of Aobs-Dobs, and suggest that the observations pinpoint, by chance, a galaxy overdensity like a proto-cluster, gas filaments lying on the quasar sightline, a large void, and orthogonal low-density filaments. Our simulations indicate that the significant departures of Bobs-Dobs are produced by the filamentary large-scale structures and the observation sightline effects.
Dermal collagen is the most abundant component of human skin and has a network structure that regulates the mechanical properties of the skin. Therefore, non-invasive characterization of the collagen ...network would be beneficial for the evaluation of skin conditions. The microscopic substructures of the network, which are individual bundles and fibers, have been optically investigated. However, the macroscopic structure of the collagen network has not been assessed. To evaluate the dermal collagen network, we developed two new indicators, volume filling factor (VFF) and collagen fiber texture (CFT), to analyze three-dimensional echo intensity maps of high-frequency ultrasonic microscopy. By identifying the difference in the elastic modulus components of the dermal layer of facial skin, the density and texture of the collagen network were characterized using VFF and CFT, respectively. These new indicators revealed that the density decreased and the texture became fine with facial age. This study demonstrates that ultrasonic microscopy is useful for investigating skin conditions, paving the way for diagnostic applications in dermatology and aesthetic medicine.
•Ultrasonic microscopy applied to unexplored collagen network in human cheek skin.•Developed indicators enabled quantification of collagen network density and texture.•Collagen network of facial skin deteriorates in density and texture with age.•Ultrasonic microscopy can assess skin conditions for dermatology diagnoses.
Abstract
In preparation for the tomography study of the intergalactic medium (IGM) by Subaru Prime Focus Spectrograph (PFS) survey and other large future telescopes such as TMT/ELT/GMT, we present ...the results of our pilot study on Ly
α
forest and IGM tomography statistics using the
GADGET3-Osaka
cosmological smoothed particle hydrodynamical simulation. Our simulation includes models for star formation and supernova feedback, which enables more realistic cross-correlation studies between galaxies, neutral hydrogen (H
i
), and metals in circumgalactic and intergalactic medium. We create a light-cone data set at
z
= 2–3 from our simulations and generate mock Ly
α
forest data. As a first step, in this paper, we focus on the distribution of H
i
and galaxies, and present statistical results on 1D flux probability distribution function, 1D power spectrum, flux contrast versus impact parameter, and H
i
–galaxy cross-correlations. Our results show overall agreement with current observational data, with some interesting discrepancies on small scales that are due to either feedback effects or varying observational conditions. Our simulation shows stronger H
i
absorption with decreasing transverse distance from galaxies. We find that massive galaxies with
M
⋆
≥ 10
10
M
⊙
contribute strongly to the flux contrast signal, and that lower-mass galaxies with
M
⋆
∼ 10
8
–10
10
M
⊙
tend to dilute the flux contrast signal from massive galaxies. On large scales, the average flux contrast smoothly connects to the IGM level, supporting the concordance Λ cold dark matter model. We also find an increase in the H
i
absorption toward the center of a protocluster.
Abstract
We present Lyα and UV-nebular emission line properties of bright Lyα emitters (LAEs) at z = 6–7 with a luminosity of log LLyα/erg s−1 = 43–44 identified in the 21 deg2 area of the SILVERRUSH ...early sample developed with the Subaru Hyper Suprime-Cam survey data. Our optical spectroscopy newly confirms 21 bright LAEs with clear Lyα emission, and contributes to making a spectroscopic sample of 96 LAEs at z = 6–7 in SILVERRUSH. From the spectroscopic sample, we select seven remarkable LAEs as bright as Himiko and CR7 objects, and perform deep Keck/MOSFIRE and Subaru/nuMOIRCS near-infrared spectroscopy reaching the 3 σ flux limit of ∼2 × 10−18 erg s−1 for the UV-nebular emission lines of He ii λ1640, C iv λλ1548,1550, and O iiiλλ1661,1666. Except for one tentative detection of C iv, we find no strong UV-nebular lines down to the flux limit, placing the upper limits of the rest-frame equivalent widths (EW0) of ∼2–4 Å for C iv, He ii, and O iii
lines. We also investigate the VLT/X-SHOOTER spectrum of CR7 whose 6 σ detection of He ii is claimed by Sobral et al. Although two individuals and the ESO archive service carefully reanalyzed the X-SHOOTER data that are used in the study of Sobral et al., no He ii signal of CR7 is detected, supportive of weak UV-nebular lines of the bright LAEs even for CR7. The spectral properties of these bright LAEs are thus clearly different from those of faint dropouts at z ∼ 7 that have strong UV-nebular lines shown in the various studies. Comparing these bright LAEs and the faint dropouts, we find anti-correlations between the UV-nebular line EW0 and the UV-continuum luminosity, which are similar to those found at z ∼ 2–3.
Abstract
We present element abundance ratios and ionizing radiation of local young low-mass (∼10
6
M
⊙
) extremely metal-poor galaxies (EMPGs) with a 2% solar oxygen abundance (O/H)
⊙
and a high ...specific star formation rate (sSFR ∼ 300 Gyr
−1
) and other (extremely) metal-poor galaxies, which are compiled from Extremely Metal-Poor Representatives Explored by the Subaru Survey (EMPRESS) and the literature. Weak emission lines such as Fe
iii
λ
4658 and He
ii
λ
4686 are detected in very deep optical spectra of the EMPGs taken with 8 m class telescopes, including Keck and Subaru, enabling us to derive element abundance ratios with photoionization models. We find that neon-to-oxygen and argon-to-oxygen ratios are comparable to those of known local dwarf galaxies and that the nitrogen-to-oxygen abundance ratios (N/O) are lower than 20% (N/O)
⊙
, consistent with the low oxygen abundance. However, the iron-to-oxygen abundance ratios (Fe/O) of the EMPGs are generally high; the EMPGs with the 2%-solar oxygen abundance show high Fe/O ratios of ∼90%–140% (Fe/O)
⊙
, which are unlikely to be explained by suggested scenarios of Type Ia supernova iron productions, iron’s dust depletion, and metal-poor gas inflow onto previously metal-riched galaxies with solar abundances. Moreover, the EMPGs with the 2%-solar oxygen abundance have very high He
ii
λ
4686/H
β
ratios of ∼1/40, which are not reproduced by existing models of high-mass X-ray binaries with progenitor stellar masses <120
M
⊙
. Comparing stellar-nucleosynthesis and photoionization models with a comprehensive sample of EMPGs identified by this and previous EMPG studies, we propose that both the high Fe/O ratios and the high He
ii
λ
4686/H
β
ratios are explained by the past existence of supermassive (>300
M
⊙
) stars, which may evolve into intermediate-mass black holes (≳100
M
⊙
).
Abstract
We present Ly
α
and ultraviolet (UV)-continuum luminosity functions (LFs) of galaxies and active galactic nuclei (AGNs) at
z
= 2.0–3.5 determined by the untargeted optical spectroscopic ...survey of the Hobby–Eberly Telescope Dark Energy Experiment (HETDEX). We combine deep Subaru imaging with HETDEX spectra resulting in 11.4 deg
2
of fiber spectra sky coverage, obtaining 18,320 galaxies spectroscopically identified with Ly
α
emission, 2126 of which host type 1 AGNs showing broad (FWHM > 1000 km s
−1
) Ly
α
emission lines. We derive the Ly
α
(UV) LF over 2 orders of magnitude covering bright galaxies and AGNs in
log
L
Ly
α
/
erg
s
−
1
=
43.3
–
45.5
(−27 <
M
UV
< −20) by the 1/
V
max
estimator. Our results reveal that the bright-end hump of the Ly
α
LF is composed of type 1 AGNs. In conjunction with previous spectroscopic results at the faint end, we measure a slope of the best-fit Schechter function to be
α
Sch
=
−
1.70
−
0.14
+
0.13
, which indicates that
α
Sch
steepens from
z
= 2–3 toward high redshift. Our UV LF agrees well with previous AGN UV LFs and extends to faint-AGN and bright-galaxy regimes. The number fraction of Ly
α
-emitting objects (
X
LAE
) increases from
M
UV
*
∼
−
21
to bright magnitude due to the contribution of type 1 AGNs, while previous studies claim that
X
Ly
α
decreases from faint magnitudes to
M
UV
*
, suggesting a valley in the
X
Ly
α
–magnitude relation at
M
UV
*
. Comparing our UV LF of type 1 AGNs at
z
= 2–3 with those at
z
= 0, we find that the number density of faint (
M
UV
> −21) type 1 AGNs increases from
z
∼ 2 to 0, as opposed to the evolution of bright (
M
UV
< −21) type 1 AGNs, suggesting AGN downsizing in the rest-frame UV luminosity.
We present spatial correlations of galaxies and IGM neutral hydrogen H i in the COSMOS/UltraVISTA 1.62 deg{sup 2} field. Our data consist of 13,415 photo-z galaxies at z ∼ 2–3 with K{sub s}<23.4 and ...the Lyα forest absorption lines in the background quasar spectra selected from SDSS data with no signature of damped Lyα system contamination. We estimate a galaxy overdensity δ {sub gal} in an impact parameter of 2.5 (proper) Mpc, and calculate the Lyα forest fluctuations δ{sub 〈F〉} whose negative values correspond to the strong Lyα forest absorption lines. We identify weak evidence of an anti-correlation between δ {sub gal} and δ{sub 〈F〉} with a Spearman’s rank correlation coefficient of −0.39 suggesting that the galaxy overdensities and the Lyα forest absorption lines positively correlate in space at the ∼90% confidence level. This positive correlation indicates that high-z galaxies exist around an excess of H i gas in the Lyα forest. We find four cosmic volumes, dubbed A {sub obs}, B {sub obs}, C {sub obs}, and D {sub obs}, that have extremely large (small) values of δ {sub gal} ≃ 0.8 (−1) and δ{sub 〈F〉}≃0.1(−0.4), three of which, B {sub obs}–D {sub obs}, significantly depart from the δ {sub gal}–δ{sub 〈F〉} correlation, and weaken the correlation signal. We perform cosmological hydrodynamical simulations and compare with our observational results. Our simulations reproduce the δ {sub gal}–δ{sub 〈F〉} correlation, agreeing with the observational results. Moreover, our simulations have model counterparts of A {sub obs}–D {sub obs}, and suggest that the observations pinpoint, by chance, a galaxy overdensity like a proto-cluster, gas filaments lying on the quasar sightline, a large void, and orthogonal low-density filaments. Our simulations indicate that the significant departures of B {sub obs}–D {sub obs} are produced by the filamentary large-scale structures and the observation sightline effects.
Abstract
We present cosmological (30−400 Mpc) distributions of neutral hydrogen (H
i
) in the intergalactic medium (IGM) traced by Ly
α
emitters (LAEs) and QSOs at
z
= 2.1–2.5, selected with the ...data of the ongoing Hobby–Eberly Telescope Dark Energy Experiment (HETDEX) and the eBOSS survey. Motivated by a previous study of Mukae et al., we investigate spatial correlations of LAEs and QSOs with H
i
tomography maps reconstructed from H
i
Ly
α
forest absorption in the spectra of background galaxies and QSOs obtained by the CLAMATO survey and this study, respectively. In the cosmological volume far from QSOs, we find that LAEs reside in regions of strong H
i
absorption, i.e., H
i
rich, which is consistent with results of previous galaxy−background QSO pair studies. Moreover, there is an anisotropy in the H
i
distribution plot of transverse and line-of-sight distances; on average the H
i
absorption peak is blueshifted by ∼200 km s
−1
from the LAE Ly
α
redshift, reproducing the known average velocity offset between the Ly
α
emission redshift and the galaxy systemic redshift. We have identified a ∼40 Mpc scale volume of H
i
underdensity that is a candidate for a giant H
ii
bubble, where six QSOs and an LAE overdensity exist at
. The coincidence of the QSO and LAE overdensities with the H
i
underdensity indicates that the ionizing photon radiation of the QSOs has created a highly ionized volume of multiple proximity zones in a matter overdensity. Our results suggest an evolutionary picture where H
i
gas in an overdensity of galaxies becomes highly photoionized when QSOs emerge in the galaxies.
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