We present a systematic study for ionization state of inter-stellar medium in galaxies at z = 0– with ∼140 000 Sloan Digital Sky Survey (SDSS) galaxies and 108 intermediate- to high-redshift galaxies ...from the literature, using an ionization parameter sensitive line ratio of O iiiλ5007/O iiλ3727 and photoionization models. We confirm that z ∼ 2–3 galaxies show an O iii/O ii ratio significantly higher than a typical star-forming galaxy of SDSS by a factor of ≳ 10, and the photoionization models reveal that these high-z galaxies have an ionization parameter of log (q
ion/cm s−1) ∼ 7.6–9.0, a factor of ∼4–10 higher than local galaxies. For galaxies at any redshift, we identify a correlation between the O iii/O ii ratio and galaxy global properties of star formation rate (SFR), stellar mass (M
*), and metallicity (Z). We extend the fundamental metallicity relation (FMR) and develop the fundamental ionization relation (FIR), a four-dimensional relation of ionization parameter, SFR, M
*, and Z. The intermediate- and high-z galaxies up to z ≃ 3 follow the FIR defined with the local galaxies, in contrast with the FMR whose possible evolution from z ∼ 2 to 3 is reported. We find that the FMR evolution of z ∼ 2–3 appears, if one omits ionization parameter differences, and that the FMR evolution does not exist for an average metallicity solution of z ∼ 3 galaxies with a high-ionization parameter. Interestingly, all of two local Lyman-continuum emitting galaxies (LyC leakers) have a high O iii/O ii ratio, indicating a positive correlation between O iii/O ii and ionizing photon escape fraction (f
esc), which is successfully explained by our photoionization models. Because O iii/O ii ratios of z ∼ 2–3 galaxies, especially Lyα emitters (LAEs), are comparable to, or higher than, those of the local LyC leakers, these high-z galaxies are candidates of Lyman-continuum emitting objects. A strong Lyα emission can coexist with a large f
esc of ≲ 0.8, and the increasing fraction of LAEs towards high-z reconciles the picture of cosmic reionization whose major ionizing sources are faint galaxies having intrinsically bright Lyα emission.
We present UV luminosity functions of dropout galaxies at with the complete Hubble Frontier Fields data. We obtain a catalog of ∼450 dropout-galaxy candidates (350, 66, and 40 at , 8, and 9, ...respectively), with UV absolute magnitudes that reach mag, ∼2 mag deeper than the Hubble Ultra Deep Field detection limits. We carefully evaluate number densities of the dropout galaxies by Monte Carlo simulations, including all lensing effects such as magnification, distortion, and multiplication of images as well as detection completeness and contamination effects in a self-consistent manner. We find that UV luminosity functions at have steep faint-end slopes, , and likely steeper slopes, at . We also find that the evolution of UV luminosity densities shows a non-accelerated decline beyond in the case of , but an accelerated one in the case of . We examine whether our results are consistent with the Thomson scattering optical depth from the Planck satellite and the ionized hydrogen fraction QH ii at based on the standard analytic reionization model. We find that reionization scenarios exist that consistently explain all of the observational measurements with the allowed parameters of and for , where is the escape fraction, Mtrunc is the faint limit of the UV luminosity function, and is the conversion factor of the UV luminosity to the ionizing photon emission rate. The length of the reionization period is estimated to be (for ), consistent with the recent estimate from Planck.
We construct z ∼ 6-7, 8, and 9 faint Lyman break galaxy samples (334, 61, and 37 galaxies, respectively) with accurate size measurements with the software glafic from the complete Hubble Frontier ...Fields (HFF) cluster and parallel fields data. These are the largest samples hitherto and reach down to the faint ends of recently obtained deep luminosity functions. At faint magnitudes, however, these samples are highly incomplete for galaxies with large sizes, implying that derivation of the luminosity function sensitively depends on the intrinsic size-luminosity relation. We thus conduct simultaneous maximum-likelihood estimation of luminosity function and size-luminosity relation parameters from the observed distribution of galaxies on the size-luminosity plane with the help of a completeness map as a function of size and luminosity. At z ∼ 6-7, we find that the intrinsic size-luminosity relation expressed as re ∝ Lβ has a notably steeper slope of than those at lower redshifts, which in turn implies that the luminosity function has a relatively shallow faint-end slope of . This steep β can be reproduced by a simple analytical model in which smaller galaxies have lower specific angular momenta. The β and values for the z ∼ 8 and 9 samples are consistent with those for z ∼ 6-7 but with larger errors. For all three samples, there is a large, positive covariance between β and , implying that the simultaneous determination of these two parameters is important. We also provide new strong lens mass models of Abell S1063 and Abell 370, as well as updated mass models of Abell 2744 and MACS J0416.1−2403.
Abstract
We conduct a comprehensive study on dropout galaxy candidates at
z
∼ 9–16 using the first 90 arcmin
2
James Webb Space Telescope (JWST) Near Infrared Camera images taken by the early release ...observations (ERO) and early release science programs. With the JWST simulation images, we find that a number of foreground interlopers are selected with a weak photo-
z
determination (Δ
χ
2
> 4). We thus carefully apply a secure photo
-z
selection criterion (Δ
χ
2
> 9) and conventional color criteria with confirmations of the ERO Near Infrared Spectrograph spectroscopic redshifts, and obtain a total of 23 dropout galaxies at
z
∼ 9–16, including two candidates at
z
phot
=
16.25
−
0.46
+
0.24
and
16.41
−
0.55
+
0.66
. We perform thorough comparisons of dropout galaxies found in our work with recent JWST studies, and conclude that our galaxy sample is reliable enough for statistical analyses. We derive the UV luminosity functions at
z
∼ 9–16, and confirm that our UV luminosity functions at
z
∼ 9 and 12 agree with those determined by other Hubble Space Telescope and JWST studies. The cosmic star formation rate (SFR) density decreases from
z
∼ 9 to 12, and perhaps to 16, but the densities at
z
∼ 12–16 are higher than the constant star formation efficiency model. Interestingly, there are six bright galaxy candidates at
z
∼ 10–16 with
M
UV
< −19.5 mag and
M
*
∼ 10
8−9
M
⊙
. Because a majority (∼80%) of these galaxies show no signatures of active galactic nuclei in their morphologies, the high cosmic SFR densities and the existence of these UV-luminous galaxies are explained by the lack of suppression of star formation by the UV background radiation at the pre-reionization epoch and/or an efficient UV radiation production by a top-heavy initial mass function with Population III–like star formation.
ABSTRACT We conduct precise strong lensing mass modeling of four Hubble Frontier Field (HFF) clusters, Abell 2744, MACS J0416.1−2403, MACS J0717.5+3745, and MACS J1149.6+2223, for which HFF imaging ...observations are completed. We construct a refined sample of more than 100 multiple images for each cluster by taking advantage of the full-depth HFF images, and conduct mass modeling using the glafic software, which assumes simply parametrized mass distributions. Our mass modeling also exploits a magnification constraint from the lensed SN Ia HFF14Tom for Abell 2744 and positional constraints from the multiple images S1-S4 of the lensed supernova SN Refsdal for MACS J1149.6+2223. We find that our best-fitting mass models reproduce the observed image positions with rms errors of ∼0 4, which are smaller than rms errors in previous mass modeling that adopted similar numbers of multiple images. Our model predicts a new image of SN Refsdal with a relative time delay and magnification that are fully consistent with a recent detection of reappearance. We then construct catalogs of z ∼ 6-9 dropout galaxies behind the four clusters and estimate magnification factors for these dropout galaxies with our best-fitting mass models. The dropout sample from the four cluster fields contains ∼120 galaxies at z 6, about 20 of which are predicted to be magnified by a factor of more than 10. Some of the high-redshift galaxies detected in the HFF have lensing-corrected magnitudes of MUV ∼ −15 to −14. Our analysis demonstrates that the HFF data indeed offer an ideal opportunity to study faint high-redshift galaxies. All lensing maps produced from our mass modeling will be made available on the Space Telescope Science Institute website (https://archive.stsci.edu/prepds/frontier/lensmodels/).
We present the first statistical sample of faint type 1 AGNs at z > 4 identified by JWST/NIRSpec deep spectroscopy. Among the 185 galaxies at z _spec = 3.8–8.9 confirmed with NIRSpec, our systematic ...search for broad-line emission reveals 10 type 1 AGNs at z = 4.015–6.936 whose broad component is only seen in the permitted H α line and not in the forbidden O iii λ 5007 line that is detected with greater significance than H α . The broad H α line widths of FWHM ≃ 1000–6000 km s ^−1 suggest that the AGNs have low-mass black holes with M _BH ∼ 10 ^6 –10 ^8 M _⊙ , remarkably lower than those of low-luminosity quasars previously identified at z > 4 with ground-based telescopes. JWST and Hubble Space Telescope high-resolution images reveal that the majority of them show extended morphologies indicating significant contribution to the total lights from their host galaxies, except for three compact objects two of which show red spectral energy distributions, probably in a transition phase from faint AGNs to low luminosity quasars. Careful AGN-host decomposition analyses show that their host’s stellar masses are systematically lower than the local relation between the black hole mass and the stellar mass, implying a fast black hole growth consistent with predictions from theoretical simulations. A high fraction of the broad-line AGNs (∼5%), higher than z ∼ 0, indicates that the number density of such faint AGNs is higher than an extrapolation of the quasar luminosity function, implying a large population of AGNs in the early universe. Such faint AGNs contribute to cosmic reionization, while the total contribution is not large, up to ∼50% at z ∼ 6, because of their faint nature.
Abstract
We present the evolution of the mass–metallicity (MZ) relation at
z
= 4–10 derived with 135 galaxies identified in JWST/NIRSpec data taken from the three major public spectroscopy programs ...of ERO, GLASS, and CEERS. Because there are many discrepancies between the flux measurements reported by the early ERO studies, we first establish our NIRSpec data reduction procedure for reliable emission-line flux measurements and errors, successfully explaining Balmer decrements with no statistical tensions thorough comparisons with the early ERO studies. Applying the reduction procedure to the 135 galaxies, we obtain emission-line fluxes for physical property measurements. We confirm that 10 out of the 135 galaxies with O
iii
λ
4363 lines have electron temperatures of ≃(1.1–2.3) × 10
4
K, similar to lower-
z
star-forming galaxies, which can be explained by heating by young massive stars. We derive the metallicities of the 10 galaxies by a direct method and the rest of the galaxies with strong lines using the metallicity calibrations of Nakajima et al. applicable for these low-mass metal-poor galaxies, anchoring the metallicities with the direct-method measurements. We thus obtain the MZ relation and star formation rate (SFR)–MZ relation over
z
= 4–10. We find that there is a small evolution of the MZ relation from
z
∼ 2–3 to
z
= 4–10, while interestingly the SFR–MZ relation shows no evolution up to
z
∼ 8 but a significant decrease at
z
> 8 beyond the errors This SFR–MZ relation decrease at
z
> 8 may suggest a break of the metallicity equilibrium state via star formation, inflow, and outflow, while further statistical and local-baseline studies are needed for a conclusion.
Abstract
The stellar initial mass function (IMF) is expressed by
ϕ
(
m
) ∝
m
−
α
with the slope
α
, and known as a poorly constrained but very important function in studies of star and galaxy ...formation. There are no sensible observational constraints on the IMF slopes beyond the Milky Way and nearby galaxies. Here we combine two sets of observational results, (1) cosmic densities of core-collapse supernova (CCSN) explosion rates and (2) cosmic far-UV radiation (and infrared reradiation) densities, which are sensitive to massive (≃8–50
M
⊙
) and moderately massive (≃2.5–7
M
⊙
) stars, respectively, and constrain the IMF slope at
m
> 1
M
⊙
with a freedom of redshift evolution. Although no redshift evolution is identified beyond the uncertainties, we find that the cosmic-average IMF slope at
z
= 0 is
α
= 1.8–3.2 at the 95% confidence level that is comparable with the Salpeter IMF,
α
= 2.35, which marks the first constraint on the cosmic-average IMF. We show a forecast for the Nancy Grace Roman Space Telescope supernova survey that will provide significantly strong constraints on the IMF slope with
δ
α
≃ 0.5 over
z
= 0–2. Moreover, as for an independent IMF probe instead of (1), we suggest to use diffuse supernovae neutrino background (DSNB), relic neutrinos from CCSNe. We expect that the Hyper-Kamiokande neutrino observations over 20 yr will improve the constraints on the IMF slope and the redshift evolution significantly better than those obtained today, if the systematic uncertainties of DSNB production physics are reduced in the future numerical simulations.
ABSTRACT We present statistics of 133 faint 1.2 mm continuum sources detected in about 120 deep Atacama Large Millimeter/submillimeter Array (ALMA) pointing data that include all the archival deep ...data available by 2015 June. We derive number counts of 1.2 mm continuum sources down to 0.02 mJy partly with the assistance of gravitational lensing, and find that the total integrated 1.2 mm flux of the securely identified sources is Jy deg−2 which corresponds to of the extragalactic background light (EBL) measured by Cosmic Background Explorer observations. These results suggest that the major 1.2 mm EBL contributors are sources with 0.02 mJy, and that very faint 1.2 mm sources with 0.02 mJy contribute negligibly to the EBL with the possible flattening and/or truncation of number counts in this very faint flux regime. To understand the physical origin of our faint ALMA sources, we measure the galaxy bias bg by the counts-in-cells technique, and place a stringent upper limit of bg < 3.5 that is not similar to bg values of massive distant red galaxies and submillimeter galaxies but comparable to those of UV-bright, star-forming BzK galaxies (sBzKs) and Lyman break galaxies (LBGs). Moreover, in the optical and near-infrared (NIR) deep fields, we identify optical-NIR counterparts for 59% of our faint ALMA sources, the majority of which have luminosities, colors, and the IRX-β relation the same as sBzKs and LBGs. We thus conclude that about a half of our faint ALMA sources are dust-poor, high-z galaxies as known as sBzKs and LBGs in optical studies, and that these faint ALMA sources are not miniature (U)LIRGs simply scaled down with the infrared brightness.
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