We examine the rest-frame ultraviolet (UV) properties of 10 C iiλ158 m-detected galaxies at z ∼ 5.5 in COSMOS using new Hubble Space Telescope/Wide Field Camera 3 near-infrared imaging. Together with ...pre-existing 158 m continuum and C ii line measurements by the Atacama Large Millimeter/submillimeter Array, we study their dust attenuation properties on the IRX-β diagram, which connects the total dust emission ( ) to the line-of-sight dust column (∝ β). We find systematically bluer UV continuum spectral slopes (β) compared to previous low-resolution ground-based measurements, which relieves some of the tension between models of dust attenuation and observations at high redshifts. While most of the galaxies are consistent with local starburst or Small Magellanic Cloud-like dust properties, we find galaxies with low IRX values and a large range in β that cannot be explained by models of a uniform dust distribution well mixed with stars. A stacking analysis of Keck/DEIMOS optical spectra indicates that these galaxies are metal-poor with young stellar populations that could significantly alter their spatial dust distribution.
We use >9400 quiescent and star-forming galaxies at z 2 in COSMOS/UltraVISTA to study the average size evolution of these systems, with focus on the rare ultra-massive population at . The large 2 ...square degree survey area delivers a sample of ∼400 such ultra-massive systems. Accurate sizes are derived using a calibration based on high-resolution images from the Hubble Space Telescope. We find that at these very high masses, the size evolution of star-forming and quiescent galaxies is almost indistinguishable in terms of normalization and power-law slope. We use this result to investigate possible pathways of quenching massive m > M* galaxies at z < 2. We consistently model the size evolution of quiescent galaxies from the star-forming population by assuming different simple models for the suppression of star formation. These models include an instantaneous and delayed quenching without altering the structure of galaxies and a central starburst followed by compaction. We find that instantaneous quenching reproduces the observed mass-size relation of massive galaxies at z > 1 well. Our starburst+compaction model followed by individual growth of the galaxies by minor mergers is preferred over other models without structural change for galaxies at z > 0.5. None of our models is able to meet the observations at m > M* and z < 1 without significant contribution of post-quenching growth of individual galaxies via mergers. We conclude that quenching is a fast process in galaxies with m ≥ 1011 M , and that major mergers likely play a major role in the final steps of their evolution.
ABSTRACT We measure a relation between the depth of four prominent rest-UV absorption complexes and metallicity for local galaxies and verify it up to . We then apply this relation to a sample of 224 ...galaxies at ( ) in the Cosmic Evolution Survey (COSMOS), for which unique UV spectra from the Deep Imaging Multi-object Spectrograph (DEIMOS) and accurate stellar masses from the Spitzer Large Area Survey with Hyper-Suprime-Cam (SPLASH) are available. The average galaxy population at and is characterized by 0.3-0.4 dex (in units of ) lower metallicities than at z ∼ 2, but comparable to . We find galaxies with weak or no Ly emission to have metallicities comparable to z ∼ 2 galaxies and therefore may represent an evolved subpopulation of galaxies. We find a correlation between metallicity and dust in good agreement with local galaxies and an inverse trend between metallicity and star-formation rate consistent with observations at z ∼ 2. The relation between stellar mass and metallicity (MZ relation) is similar to , but there are indications of it being slightly shallower, in particular for the young, Ly -emitting galaxies. We show that, within a "bathtub" approach, a shallower MZ relation is expected in the case of a fast (exponential) build-up of stellar mass with an e-folding time of 100-200 Myr. Because of this fast evolution, the process of dust production and metal enrichment as a function of mass could be more stochastic in the first billion years of galaxy formation compared to later times.
ABSTRACT
Identifying non-contaminated sample of high-redshift galaxies with escaping Lyman continuum (LyC) flux is important for understanding the sources and evolution of cosmic reionization. We ...present CLAUDS (CFHT Large Area u-band deep survey) u-band photometry of the COSMOS field to probe LyC radiation from spectroscopically confirmed galaxies at $z$ ≥ 3.5 and outside the standard Lyman-break galaxy colour-selection expectations. Complementary to the CLAUDS data, we use Subaru multifilter photometry, Hubble Space Telescope (HST) multifilter imaging, and the spectroscopic surveys D10K, VUDS, and 3D-HST. We present a sample of Lyman continuum galaxy (LCG) candidates in the redshift range 3.5 ≲ $z$ ≲ 5.1. Here, we introduce 5 LCG candidates, where two are flagged quality 1 and three quality 2. The estimated $f_{\rm esc}^{\rm abs}$ for quality 1 candidates are in the range $\sim 5 - 73{{\ \rm per\ cent}}$ and $\sim 30 - 93{{\ \rm per\ cent}}$. These estimates are based on our derived parameters from individual galaxies as inputs to a range of BPASS models as well as mean intergalactic medium (IGM) and maximal intergalactic and circumgalactic media (IGM+CGM) transmission. We conclude that our search for LCGs is most likely biased to lines of sight with low H i densities or free from Lyman limit systems. Our two best LCG candidates have EW (Lyα) ≤ 50 Å and we find no correlation or anticorrelation between EW (Lyα), $f_{\rm esc}^{\rm abs}$, and Robs, the ratio of ionizing to non-ionizing observed flux in the measured passbands. Stacking candidates without solid LyC detections (S/N < 3) results in an estimated $f_{\rm esc}^{\rm abs}$ from galaxies not greater than $1{{\ \rm per\ cent}}$.
The ALPINE-ALMA [CII] survey Khusanova, Y.; Bethermin, M.; Le Fèvre, O. ...
Astronomy and astrophysics (Berlin),
05/2021, Letnik:
649
Journal Article
Recenzirano
Odprti dostop
Star formation rate (SFR) measurements at
z
> 4 have relied mostly on the rest-frame far-ultraviolet (FUV) observations. The corrections for dust attenuation based on the IRX-
β
relation are highly ...uncertain and are still debated in the literature. Hence, rest-frame far-infrared (FIR) observations are necessary to constrain the dust-obscured component of the SFR. In this paper, we exploit the rest-frame FIR continuum observations collected by the ALMA Large Program to INvestigate CII at Early times (ALPINE) to directly constrain the obscured SFR in galaxies at 4.4 <
z
< 5.9. We used stacks of continuum images to measure average infrared luminosities taking both detected and undetected sources into account. Based on these measurements, we measured the position of the main sequence of star-forming galaxies and the specific SFR (sSFR) at
z
∼ 4.5 and
z
∼ 5.5. We find that the main sequence and sSFR do not significantly evolve between
z
∼ 4.5 and
z
∼ 5.5, as opposed to lower redshifts. We developed a method to derive the obscured SFR density (SFRD) using the stellar masses or FUV-magnitudes as a proxy of FIR fluxes measured on the stacks and combining them with the galaxy stellar mass functions and FUV luminosity functions from the literature. We obtain consistent results independent of the chosen proxy. We find that the obscured fraction of SFRD is decreasing with increasing redshift, but even at
z
∼ 5.5 it constitutes around 61% of the total SFRD.
ABSTRACT
We present 10 main-sequence ALPINE galaxies (log (M/M⊙) = 9.2−11.1 and ${\rm SFR}=23-190\, {\rm M_{\odot }\, yr^{-1}}$) at z ∼ 4.5 with optical O ii measurements from Keck/MOSFIRE ...spectroscopy and Subaru/MOIRCS narrow-band imaging. This is the largest such multiwavelength sample at these redshifts, combining various measurements in the ultraviolet, optical, and far-infrared including C ii158 $\mu$m line emission and dust continuum from ALMA and H α emission from Spitzer photometry. For the first time, this unique sample allows us to analyse the relation between O ii and total star-formation rate (SFR) and the interstellar medium (ISM) properties via O ii/C ii and O ii/H α luminosity ratios at z ∼ 4.5. The O ii−SFR relation at z ∼ 4.5 cannot be described using standard local descriptions, but is consistent with a metal-dependent relation assuming metallicities around $50{{\ \rm per\ cent}}$ solar. To explain the measured dust-corrected luminosity ratios of $\log (L_{\rm OII}/L_{\rm CII}) \sim 0.98^{+0.21}_{-0.22}$ and $\log (L_{\rm OII}/L_{\rm H\alpha }) \sim -0.22^{+0.13}_{-0.15}$ for our sample, ionization parameters log (U) < −2 and electron densities $\log (\rm n_e / {\rm cm^{-3}}) \sim 2.5-3$ are required. The former is consistent with galaxies at z ∼ 2−3, however lower than at z > 6. The latter may be slightly higher than expected given the galaxies’ specific SFR. The analysis of this pilot sample suggests that typical log (M/M⊙) > 9 galaxies at z ∼ 4.5 to have broadly similar ISM properties as their descendants at z ∼ 2 and suggest a strong evolution of ISM properties since the epoch of reionization at z > 6.
Abstract
We present the C II 158
μ
m line luminosity functions (LFs) at
z
∼ 4–6 using the ALMA observations of 118 sources, which are selected to have UV luminosity
M
1500Å
< −20.2 and optical ...spectroscopic redshifts in COSMOS and ECDF-S. Of the 118 targets, 75 have significant C II detections and 43 are upper limits. This is by far the largest sample of C II detections, which allows us to set constraints on the volume density of C II emitters at
z
∼ 4–6. But because this is a UV-selected sample, we are missing C II-bright but UV-faint sources, making our constraints strict lower limits. Our derived LFs are statistically consistent with the
z
∼ 0 C II LF at 10
8.25
–10
9.75
L
⊙
. We compare our results with the upper limits of the C II LF derived from serendipitous sources in the ALPINE maps. We also infer the C II LFs based on published far-IR and CO LFs at
z
∼ 4–6. Combining our robust lower limits with these additional estimates, we set further constraints on the true number density of C II emitters at
z
∼ 4–6. These additional LF estimates are largely above our LF at
L
CII
> 10
9
L
⊙
, suggesting that UV-faint but C II-bright sources likely make significant contributions to the C II emitter volume density. When we include all the LF estimates, we find that available model predictions underestimate the number densities of C II emitters at
z
∼ 4–6. Finally, we set a constraint on the molecular gas mass density at
z
∼ 4–6, with
ρ
mol
∼ (2–7) × 10
7
M
⊙
Mpc
−3
. This is broadly consistent with previous studies.
Abstract
We present the average C
ii
158
μ
m emission line sizes of UV-bright star-forming galaxies at
z
∼ 7. Our results are derived from a stacking analysis of C
ii
158
μ
m emission lines and ...dust continua observed by the Atacama Large Millimeter/submillimeter Array (ALMA), taking advantage of the large program Reionization Era Bright Emission Line Survey. We find that the average C
ii
emission at
z
∼ 7 has an effective radius
r
e
of 2.2 ± 0.2 kpc. It is ≳2× larger than the dust continuum and the rest-frame UV emission, in agreement with recently reported measurements for
z
≲ 6 galaxies. Additionally, we compared the average C
ii
size with 4 <
z
< 6 galaxies observed by the ALMA Large Program to INvestigate C
ii
at Early times (ALPINE). By analyzing C
ii
sizes of 4 <
z
< 6 galaxies in two redshift bins, we find an average C
ii
size of
r
e
= 2.2 ± 0.2 kpc and
r
e
= 2.5 ± 0.2 kpc for
z
∼ 5.5 and
z
∼ 4.5 galaxies, respectively. These measurements show that star-forming galaxies, on average, show no evolution in the size of the C
ii
158
μ
m emitting regions at redshift between
z
∼ 7 and
z
∼ 4. This finding suggests that the star-forming galaxies could be morphologically dominated by gas over a wide redshift range.
We measure the stellar mass function (SMF) and stellar mass density of galaxies in the COSMOS field up to
z
~ 6. We select them in the near-IR bands of the COSMOS2015 catalogue, which includes ...ultra-deep photometry from UltraVISTA-DR2, SPLASH, and Subaru/Hyper Suprime-Cam. At
z
> 2.5 we use new precise photometric redshifts with error
σ
z
= 0.03(1 +
z
) and an outlier fraction of 12%, estimated by means of the unique spectroscopic sample of COSMOS (~100 000 spectroscopic measurements in total, more than one thousand having robust
z
spec
> 2.5). The increased exposure time in the DR2, along with our panchromatic detection strategy, allow us to improve the completeness at high
z
with respect to previous UltraVISTA catalogues (e.g. our sample is >75% complete at 10
10
ℳ
⊙
and
z
= 5). We also identify passive galaxies through a robust colour–colour selection, extending their SMF estimate up to
z
= 4. Our work provides a comprehensive view of galaxy-stellar-mass assembly between
z
= 0.1 and 6, for the first time using consistent estimates across the entire redshift range. We fit these measurements with a Schechter function, correcting for Eddington bias. We compare the SMF fit with the halo mass function predicted from ΛCDM simulations, finding that at
z
> 3 both functions decline with a similar slope in thehigh-mass end. This feature could be explained assuming that mechanisms quenching star formation in massive haloes become less effective at high redshifts; however further work needs to be done to confirm this scenario. Concerning the SMF low-mass end, it shows a progressive steepening as it moves towards higher redshifts, with
α
decreasing from -1.47
+0.02
-0.02
at
z
≃ 0.1 to -2.11
+0.30
-0.13
at
z
≃ 5. This slope depends on the characterisation of the observational uncertainties, which is crucial to properly remove the Eddington bias. We show that there is currently no consensus on the method to quantify such errors: different error models result in different best-fit Schechter parameters.
We present the ancillary data and basic physical measurements for the galaxies in the ALMA Large Program to Investigate C+ at Early Times (ALPINE) survey-the first large multiwavelength survey that ...aims at characterizing the gas and dust properties of 118 main-sequence galaxies at redshifts 4.4 < z < 5.9 via the measurement of emission at (64% at >3.5 ) and the surrounding far-infrared continuum in conjunction with a wealth of optical and near-infrared data. We outline in detail the spectroscopic data and selection of the galaxies as well as the ground- and space-based imaging products. In addition, we provide several basic measurements including stellar masses, star formation rates (SFR), rest-frame ultra-violet (UV) luminosities, UV continuum slopes (β), and absorption line redshifts, as well as H emission derived from Spitzer colors. We find that the ALPINE sample is representative of the 4 < z < 6 galaxy population selected by photometric methods and only slightly biased toward bluer colors (Δβ ∼ 0.2). Using as tracer of the systemic redshift (confirmed for one galaxy at z = 4.5 out of 118 for which we obtained optical λ3727 emission), we confirm redshifted Ly emission and blueshifted absorption lines similar to findings at lower redshifts. By stacking the rest-frame UV spectra in the rest frame, we find that the absorption lines in galaxies with high specific SFR are more blueshifted, which could be indicative of stronger winds and outflows.
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