We present the first stellar velocity dispersion measurement of a massive quenching galaxy at z = 4. The galaxy is first identified as a massive z ≥ 4 galaxy with suppressed star formation from ...photometric redshifts based on deep multiband data. A follow-up spectroscopic observation with MOSFIRE on Keck revealed strong multiple absorption features, which are identified as Balmer lines, giving a secure redshift of z = 4.01. This is the most distant quiescent galaxy known to date. Thanks to the high S/N of the spectrum, we are able to estimate the stellar velocity dispersion, , making a significant leap from the previous highest redshift measurement at z = 2.8. Interestingly, we find that the velocity dispersion is consistent with that of massive galaxies today, implying no significant evolution in velocity dispersion over the last 12 Gyr. Based on a stringent upper limit on its physical size from deep optical images (reff < 1.3 kpc), we find that its dynamical mass is consistent with the stellar mass inferred from photometry. Furthermore, the galaxy is located on the mass fundamental plane extrapolated from lower redshift galaxies. The observed no strong evolution in suggests that the mass in the core of massive galaxies does not evolve significantly, while most of the mass growth occurs in the outskirts of the galaxies, which also increases the size. This picture is consistent with a two-phase formation scenario in which mass and size growth is due to accretion in the outskirts of galaxies via mergers. Our results imply that the first phase may be completed as early as z ∼ 4.
Abstract
We present the results of a systematic search for candidate quiescent galaxies in the distant universe in 11 JWST fields with publicly available observations collected during the first 3 ...months of operations and covering an effective sky area of ∼145 arcmin
2
. We homogeneously reduce the new JWST data and combine them with existing observations from the Hubble Space Telescope. We select a robust sample of ∼80 candidate quiescent and quenching galaxies at 3 <
z
< 5 using two methods: (1) based on their rest-frame
UVJ
colors, and (2) a novel quantitative approach based on Gaussian mixture modeling of the near-UV −
U
,
U
−
V
, and
V
−
J
rest-frame color space, which is more sensitive to recently quenched objects. We measure comoving number densities of massive (
M
⋆
≥ 10
10.6
M
⊙
) quiescent galaxies consistent with previous estimates relying on ground-based observations, after homogenizing the results in the literature with our mass and redshift intervals. However, we find significant field-to-field variations of the number densities up to a factor of 2–3, highlighting the effect of cosmic variance and suggesting the presence of overdensities of red quiescent galaxies at
z
> 3, as could be expected for highly clustered massive systems. Importantly, JWST enables the robust identification of quenching/quiescent galaxy candidates at lower masses and higher redshifts than before, challenging standard formation scenarios. All data products, including the literature compilation, are made publicly available.
Abstract
We report a massive quiescent galaxy at
z
spec
=
3.0922
−
0.004
+
0.008
spectroscopically confirmed at a protocluster in the SSA22 field by detecting the Balmer and Ca
ii
absorption features ...with the multi-object spectrometer for infrared exploration on the Keck I telescope. This is the most distant quiescent galaxy confirmed in a protocluster to date. We fit the optical to mid-infrared photometry and spectrum simultaneously with spectral energy distribution (SED) models of parametric and nonparametric star formation histories (SFHs). Both models fit the observed SED well and confirm that this object is a massive quiescent galaxy with a stellar mass of
log
(
M
⋆
/
M
⊙
)
=
11.26
−
0.04
+
0.03
and
11.54
−
0.00
+
0.03
, and a star formation rate of SFR/
M
⊙
yr
−1
< 0.3 and
=
0.01
−
0.01
+
0.03
for parametric and nonparametric models, respectively. The SFH from the former modeling is described as an instantaneous starburst whereas that of the latter modeling is longer-lived, but both models agree with a sudden quenching of the star formation at ∼0.6 Gyr ago. This massive quiescent galaxy is confirmed in an extremely dense group of galaxies predicted as a progenitor of a brightest cluster galaxy formed via multiple mergers in cosmological numerical simulations. We discover three new plausible O
iii
λ
5007 emitters at 3.0791 ≤
z
spec
≤ 3.0833 serendipitously detected around the target. Two of them just between the target and its nearest massive galaxy are possible evidence of their interactions. They suggest the future great size and stellar mass evolution of this massive quiescent galaxy via mergers.
FOREVER22: galaxy formation in protocluster regions Yajima, Hidenobu; Abe, Makito; Khochfar, Sadegh ...
Monthly Notices of the Royal Astronomical Society,
01/2022, Letnik:
509, Številka:
3
Journal Article
Recenzirano
Odprti dostop
ABSTRACT
We present results from a new cosmological hydrodynamics simulation campaign of protocluster (PC) regions, FOREVER22: FORmation and EVolution of galaxies in Extremely overdense Regions ...motivated by SSA22. The simulations cover a wide range of cosmological scales using three different zoom set-ups in a parent volume of $(714.2~\rm cMpc)^{3}$: PCR (Proto-Cluster Region; V = (28.6 cMpc)3, SPH particle mass, mSPH = 4.1 × 106 M⊙, and final redshift, zend = 2.0), BCG (Brightest proto-Cluster Galaxy; V ∼ (10 cMpc)3, mSPH = 5.0 × 105 M⊙ and zend = 4.0), and First (V ∼ (3 cMpc)3, mSPH = 7.9 × 103 M⊙ and zend = 9.5) runs, that allow us to focus on different aspects of galaxy formation. In the PCR runs, we follow 10 PCs, each harbouring 1–4 SMBHs with ${\rm M_{\rm BH}}\ge 10^{9}~{\rm M_{\odot }}$. One of the PC cores shows a spatially close arrangement of seven starburst galaxies with ${\rm SFR} \gtrsim 100~{\rm {\rm M_{\odot }}~{\rm yr^{-1}}}$ each, that are dust-obscured and would appear as submillimetre galaxies with flux ≳1 mJy at $1.1~ \rm mm$ in observations. The BCG runs show that the total SFRs of haloes hosting BCGs are affected by AGN feedback, but exceed $1000~{\rm {\rm M_{\odot }}~{\rm yr^{-1}}}$ at z ≲ 6. The First runs resolve mini-haloes hosting population (Pop) III stars and we show that, in PC regions, the dominant stellar population changes from Pop III to Pop II at z ≳ 20, and the first galaxies with ${\rm SFR} \gtrsim 18~{\rm {\rm M_{\odot }}~{\rm yr^{-1}}}$ form at z ∼ 10. These can be prime targets for future observations with the James Webb Space Telescope. Our simulations successfully reproduce the global star formation activities in observed PCs and suggest that PCs can kickstart cosmic reionization.
We present results from a deep 2′ × 3′ (comoving scale of 3.7 Mpc × 5.5 Mpc at z = 3) survey at 1.1 mm, taken with the Atacama Large Millimeter/submillimeter Array (ALMA) in the SSA22 field. We ...observe the core region of a z = 3.09 protocluster, achieving a typical rms sensitivity of 60 Jy beam−1 at a spatial resolution of 0 7. We detect 18 robust ALMA sources at a signal-to-noise ratio (S/N) > 5. Comparison between the ALMA map and a 1.1 mm map, taken with the AzTEC camera on the Atacama Submillimeter Telescope Experiment (ASTE), indicates that three submillimeter sources discovered by the AzTEC/ASTE survey are resolved into eight individual submillimeter galaxies (SMGs) by ALMA. At least 10 of our 18 ALMA SMGs have spectroscopic redshifts of z 3.09, placing them in the protocluster. This shows that a number of dusty starburst galaxies are forming simultaneously in the core of the protocluster. The nine brightest ALMA SMGs with S/N > 10 have a median intrinsic angular size of ( physical kpc at z = 3.09), which is consistent with previous size measurements of SMGs in other fields. As expected, the source counts show a possible excess compared to the counts in the general fields at S1.1mm ≥ 1.0 mJy, due to the protocluster. Our contiguous mm mapping highlights the importance of large-scale structures on the formation of dusty starburst galaxies.
We perform a stacking analysis of Planck, AKARI, Infrared Astronomical Satellite, Wide-field Infrared Survey Explorer, and Herschel images of the largest number of (candidate) protoclusters at z ∼ ...3.8 selected from the Hyper Suprime-Cam Subaru Strategic Program. Stacking the images of the 179 candidate protoclusters, the combined infrared (IR) emission of the protocluster galaxies in the observed 12-850 m wavelength range is successfully detected with >5 significance (at Planck). This is the first time that the average IR spectral energy distribution (SED) of a protocluster has been constrained at z ∼ 4. The observed IR SEDs of the protoclusters exhibit significant excess emission in the mid-IR compared to that expected from typical star-forming galaxies (SFGs). They are reproduced well using SED models of intense starburst galaxies with warm/hot dust heated by young stars, or by a population of active galactic nucleus (AGN)/SFG composites. For the pure star-forming model, a total IR (from 8-1000 m) luminosity of 19.3 − 4.2 + 0.6 × 10 13 L and a star formation rate of 16.3 − 7.8 + 1.0 × 10 3 M yr−1 are found, whereas for the AGN/SFG composite model, 5.1 − 2.5 + 2.5 × 10 13 L and 2.1 − 1.7 + 6.3 × 10 3 M yr−1 are found. Uncertainty remains in the total SFRs; however, the IR luminosities of the most massive protoclusters are likely to continue increasing up to z ∼ 4. Meanwhile, no significant IR flux excess is observed around optically selected QSOs at similar redshifts, which confirms previous results. Our results suggest that the z ∼ 4 protoclusters trace dense, intensely star-forming environments that may also host obscured AGNs missed by the selection in the optical.
Abstract
Protoclusters of galaxies have been found in the last quarter-century. However, most of them have been found through the overdensity of star-forming galaxies, and there have been no known ...structures identified by more than two spectroscopically confirmed quiescent galaxies at
z
> 2.5. In this letter, we report the discovery of an overdense structure of massive quiescent galaxies with the spectroscopic redshift
z
= 2.77 in the COSMOS field, QO-1000. We first photometrically identify this structure as a 4.2
σ
overdensity with 14 quiescent galaxies in 7 × 4 pMpc
2
from the COSMOS2020 catalog. We then securely confirm the spectroscopic redshifts of four quiescent galaxies by detecting multiple Balmer absorption lines with Keck/MOSFIRE. All the spectroscopically confirmed members are massive (
log
(
M
⋆
/
M
⊙
)
>
11.0
) and located in a narrow redshift range (2.76 <
z
< 2.79). Moreover, three of them are in the 1 × 1 pMpc
2
in the transverse direction at the same redshift (
z
= 2.760–2.763). Such a concentration of four spectroscopically confirmed quiescent galaxies implies that QO-1000 is >68 times denser than the general field. In addition, we confirm that they form a red sequence in the
J
−
K
s
color. This structure’s halo mass is estimated as
log
(
M
halo
/
M
⊙
)
>
13.2
from its stellar mass. Similar structures found in the IllustrisTNG simulation are expected to evolve into massive galaxy clusters with
log
(
M
halo
/
M
⊙
)
≥
14.8
at
z
= 0. These results suggest that QO-1000 is a more mature protocluster than the other known protoclusters. It is likely in a transition phase between star-forming protoclusters and quenched galaxy clusters.
Abstract We report on the spectroscopic confirmation of a massive quiescent galaxy at z spec = 4.53 in the COSMOS field. The object was first identified as a galaxy with suppressed star formation at ...z phot ∼ 4.65 from the COSMOS2020 catalog. The follow-up spectroscopy with Keck/MOSFIRE in the K band reveals faint O ii emission and the Balmer break, indicative of evolved stellar populations. We fit the spectral energy distribution using photometry and a spectrum to infer physical properties. The obtained stellar mass is high ( M * ∼ 10 10.8 M ⊙ ) and the current star formation rate is more than 1 dex below that of main-sequence galaxies at z = 4.5. Its star formation history suggests that this galaxy experienced rapid quenching from z ∼ 5. The galaxy is among the youngest quiescent galaxies confirmed so far at z spec > 3 with z form ∼ 5.2 (200 Myr ago), which is the epoch when 50% of the total stellar mass was formed. A unique aspect of the galaxy is that it is in an extremely dense region; there are four massive star-forming galaxies at 4.4 < z phot < 4.7 located within 150 physical kpc from the galaxy. Interestingly, three of them have virial radii that strongly overlap with that of the central quiescent galaxy (∼70 kpc), suggesting that the overdensity region is likely the highest-redshift candidate of a dense group with a spectroscopically confirmed quiescent galaxy at the center. The group provides us with a unique opportunity to gain insights into the role of the group environment in quenching at z ∼ 5, which corresponds to the formation epoch of massive elliptical galaxies in the local Universe.
Abstract We report on discovery of a concentration of massive quiescent galaxies located at z = 4. The concentration is first identified using high-quality photometric redshifts based on deep, ...multiband data in Subaru/XMM-Newton Deep Field. Follow-up near-infrared spectroscopic observations with MOSFIRE on Keck confirm a massive (∼10 11 M ⊙ ) quiescent galaxy at z = 3.99. Our spectral energy distribution analyses reveal that the galaxy experienced an episode of starburst about 500 Myr prior to the observed epoch, followed by rapid quenching. Since its spectrum is sufficiently good to measure the stellar velocity dispersion, we infer its dynamical mass and find that it is consistent with its stellar mass. The galaxy is surrounded by four massive (>10 10 M ⊙ ) quiescent galaxies on a ∼1 physical Mpc scale, all of which are consistent with being located at the same redshift based on high-accuracy spectrophotometric redshifts. This is likely a (proto)cluster dominated by quiescent galaxies, the first of the kind reported at such a high redshift as z = 4. Interestingly, it is in a large-scale structure revealed by spectroscopic redshifts from VANDELS. Furthermore, it also exhibits a red sequence, adding further support to the physical concentration of the galaxies. We find no such concentration in the Illustris-TNG300 simulation; it may be that the cluster is such a rare system that the simulation box is not sufficiently large to reproduce it. The total halo mass of the quiescent galaxies is ∼10 13 M ⊙ , suggesting that they form a group-sized halo once they collapse together. We discuss the implications of our findings for the quenching physics and conclude with future prospects.
We report the rest-frame ultraviolet luminosity function of g-dropout galaxies in 177 protocluster candidates (PC UVLF) at z ∼ 4 selected in the Hyper Suprime-Cam Subaru Strategic Program. Comparing ...it with the UVLF of field galaxies at the same redshift, we find that the PC UVLF shows a significant excess toward the bright end. This excess cannot be explained by the contribution of only active galactic nuclei, and we also find that this excess is more significant in higher density regions. Assuming that all protocluster members are located on the star formation main sequence, the PC UVLF can be converted into a stellar mass function. Consequently, our protocluster members are inferred to have a 2.8 times more massive characteristic stellar mass than that of the field Lyman break galaxies at the same redshift. This study, for the first time, clearly shows that the enhancement in star formation or stellar mass in overdense regions can generally be seen as early as at z ∼ 4. We also estimate the star formation rate density (SFRD) in protocluster regions as 6%-20% of the cosmic SFRD, based on the measured PC UVLF after correction for the selection incompleteness in our protocluster sample. This high value suggests that protoclusters make a nonnegligible contribution to the cosmic SFRD at z ∼ 4, as previously suggested by simulations. Our results suggest that protoclusters are essential components for galaxy evolution at z ∼ 4.
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