5 research outputs found
The HST Cosmos Project: Contribution from the Subaru Telescope
The Cosmic Evolution Survey (COSMOS) is a Hubble Space Telescope (HST)
treasury project.The COSMOS aims to perform a 2 square degree imaging survey of
an equatorial field in (F814W) band, using the Advanced Camera for Surveys
(ACS). Such a wide field survey, combined with ground-based photometric and
spectroscopic data, is essential to understand the interplay between large
scale structure, evolution and formation of galaxies and dark matter. In 2004,
we have obtained high-quality, broad band images of the COSMOS field ( and ) using Suprime-Cam on the Subaru
Telescope, and we have started our new optical multi-band program, COSMOS-21 in
2005. Here, we present a brief summary of the current status of the COSMOS
project together with contributions from the Subaru Telescope. Our future
Subaru program, COSMOS-21, is also discussed briefly.Comment: 4 pages, 3 figures, to appear in the Proceedings of the 6th East
Asian Meeting on Astronomy, JKAS, 39, in pres
COSMOS2020: Identification of High-z Protocluster Candidates in COSMOS
We conduct a systematic search for protocluster candidates at in
the COSMOS field using the recently released COSMOS2020 source catalog. We
select galaxies using a number of selection criteria to obtain a sample of
galaxies that have a high probability of being inside a given redshift bin. We
then apply overdensity analysis to the bins using two density estimators, a
Weighted Adaptive Kernel Estimator and a Weighted Voronoi Tessellation
Estimator. We have found 15 significant () candidate galaxy
overdensities across the redshift range . The majority of the
galaxies appear to be on the galaxy main sequence at their respective epochs.
We use multiple stellar-mass-to-halo-mass conversion methods to obtain a range
of dark matter halo mass estimates for the overdensities in the range of
, at the respective redshifts of the
overdensities. The number and the masses of the halos associated with our
protocluster candidates are consistent with what is expected from the area of a
COSMOS-like survey in a standard CDM cosmology. Through comparison
with simulation, we expect that all the overdensities at will evolve
into a Virgo-/Coma-like clusters at present (i.e., with masses ). Compared to other overdensities identified at
via narrow-band selection techniques, the overdensities presented
appear to have higher stellar masses and star-formation rates.
We compare the evolution in the total star-formation rate and stellar mass
content of the protocluster candidates across the redshift range
and find agreement with the total average star-formation rate from simulations.Comment: 52 pages, 32 figues, 18 tables, main text is 30 pages, appendix is 22
pages, to be published in Ap
Two Massive, Compact, and Dust-obscured Candidate z ≃ 8 Galaxies Discovered by JWST
We present a search for extremely red, dust-obscured, z > 7 galaxies with JWST/NIRCam+MIRI imaging over the first 20 arcmin(2) of publicly available Cycle 1 data from the COSMOS-Web, CEERS, and PRIMER surveys. Based on their red color in F277W-F444W (similar to 2.5 mag) and detection in MIRI/F770W (similar to 25 mag), we identify two galaxies, COS-z8M1 and CEERS-z7M1, that have best-fit photometric redshifts of z = 8.4(-0.4)(+0.3) and 7.6(-0.1)(+0.1), respectively. We perform spectral energy distribution fitting with a variety of codes (including BAGPIPES, PROSPECTOR, BEAGLE, and CIGALE) and find a >95% probability that these indeed lie at z > 7. Both sources are compact (R-eff less than or similar to 200 pc) and highly obscured (A(V) similar to 1.5-2.5) and, at our best-fit redshift estimates, likely have strong [O III]+H beta emission contributing to their 4.4 mu m photometry. We estimate stellar masses of similar to 10(10) M-circle dot for both sources; by virtue of detection in MIRI at 7.7 mu m, these measurements are robust to the inclusion of bright emission lines, for example, from an active galactic nucleus. We identify a marginal (2.9 sigma) Atacama Large Millimeter/submillimeter Array detection at 2 mm within 0 ''.5 of COS-z8M1, which, if real, would suggest a remarkably high IR luminosity of similar to 10(12) L-circle dot. These two galaxies, if confirmed at z similar to 8, would be extreme in their stellar and dust masses and may be representative of a substantial population of highly dust-obscured galaxies at cosmic dawn.Peer reviewe