COSMOS-Web: An Overview of the JWST Cosmic Origins Survey

Deep observations with the James Webb Space Telescope (JWST) have revealed an emerging population of red pointlike sources that could provide a link between the postulated supermassive black hole seeds and observed quasars. In this work, we present a JWST/NIRSpec spectrum from the JWST Cycle 1 UNCOVER Treasury survey of a massive accreting black hole at z = 8.50 displaying a clear broad-line component as inferred from the Hβ line with FWHM = 3439 ± 413 km s−1, typical of the broad-line region of an active galactic nucleus (AGN). The AGN nature of this object is further supported by high ionization, as inferred from emission lines, and a point-source morphology. We compute a black hole mass of log10(MBH/M⊙)=8.17±0.42 and a bolometric luminosity of L bol ∼ 6.6 × 1045 erg s−1. These values imply that our object is accreting at ∼40% of the Eddington limit. Detailed modeling of the spectral energy distribution in the optical and near-infrared, together with constraints from ALMA, indicate an upper limit on the stellar mass of log10(M*/M⊙)<8.7 , which would lead to an unprecedented ratio of black hole to host mass of at least ∼30%. This is orders of magnitude higher compared to the local QSOs but consistent with recent AGN studies at high redshift with JWST. This finding suggests that a nonnegligible fraction of supermassive black holes either started out from massive seeds and/or grew at a super-Eddington rate at high redshift. Given the predicted number densities of high-z faint AGN, future NIRSpec observations of larger samples will allow us to further investigate galaxy–black hole coevolution in the early Universe.

pdf/uncover-a-nirspec-identification-of-a-broad-line-agn-at-z-8-2225h1xn6e.pdf

UNCOVER: A NIRSpec Identification of a Broad-line AGN at z = 8.50

We present the survey design, implementation, and outlook for COSMOS-Web, a 255 hour treasury program conducted by the James Webb Space Telescope in its first cycle of observations. COSMOS-Web is a contiguous 0.54 deg$^2$ NIRCam imaging survey in four filters (F115W, F150W, F277W, and F444W) that will reach 5$\sigma$ point source depths ranging $\sim$27.5-28.2 magnitudes. In parallel, we will obtain 0.19 deg$^2$ of MIRI imaging in one filter (F770W) reaching 5$\sigma$ point source depths of $\sim$25.3-26.0 magnitudes. COSMOS-Web will build on the rich heritage of multiwavelength observations and data products available in the COSMOS field. The design of COSMOS-Web is motivated by three primary science goals: (1) to discover thousands of galaxies in the Epoch of Reionization ($6<z<11$) and map reionization's spatial distribution, environments, and drivers on scales sufficiently large to mitigate cosmic variance, (2) to identify hundreds of rare quiescent galaxies at $z>4$ and place constraints on the formation of the Universe's most massive galaxies ($M_\star>10^{10}$\,M$_\odot$), and (3) directly measure the evolution of the stellar mass to halo mass relation using weak gravitational lensing out to $z\sim2.5$ and measure its variance with galaxies' star formation histories and morphologies. In addition, we anticipate COSMOS-Web's legacy value to reach far beyond these scientific goals, touching many other areas of astrophysics, such as the identification of the first direct collapse black hole candidates, ultracool sub-dwarf stars in the Galactic halo, and possibly the identification of $z>10$ pair-instability supernovae. In this paper we provide an overview of the survey's key measurements, specifications, goals, and prospects for new discovery.


 Observations with the James Webb Space Telescope (JWST) have uncovered numerous faint active galactic nuclei (AGN) at z ∼ 5 and beyond. These objects are key to our understanding of the formation of supermassive black holes (SMBHs), their coevolution with host galaxies, as well as the role of AGN in cosmic reionization. Using photometric colors and size measurements, we perform a search for compact red objects in an array of blank deep JWST/NIRCam fields totaling ∼640 arcmin2. Our careful selection yields 260 reddened AGN candidates at 4 < z
 phot < 9, dominated by a point-source-like central component (〈r
 eff〉 < 130 pc) and displaying a dichotomy in their rest-frame colors (blue UV and red optical slopes). Quasar model fitting reveals our objects to be moderately dust-extincted (A
 V ∼ 1.6), which is reflected in their inferred bolometric luminosities of L
 bol = 1044–47 erg s−1 and fainter UV magnitudes M
 UV ≃ −17 to −22. Thanks to the large areas explored, we extend the existing dusty AGN luminosity functions to both fainter and brighter magnitudes, estimating their number densities to be ×100 higher than for UV-selected quasars of similar magnitudes. At the same time, they constitute only a small fraction of all UV-selected galaxies at similar redshifts, but this percentage rises to ∼10% for M
 UV ∼ − 22 at z ∼ 7. Finally, assuming a conservative case of accretion at the Eddington rate, we place a lower limit on the SMBH mass function at z ∼ 5, finding it to be consistent with both theory and previous JWST observations.

A Census of Photometrically Selected Little Red Dots at 4 < z < 9 in JWST Blank Fields

Abstract We present a search for extremely red, dust-obscured, z &gt; 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 (∼2.5 mag) and detection in MIRI/F770W (∼25 mag), we identify two galaxies, COS-z8M1 and CEERS-z7M1, that have best-fit photometric redshifts of <?CDATA $z={8.4}_{-0.4}^{+0.3}$?> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mi>z</mml:mi> <mml:mo>=</mml:mo> <mml:msubsup> <mml:mrow> <mml:mn>8.4</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>0.4</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>0.3</mml:mn> </mml:mrow> </mml:msubsup> </mml:math> and <?CDATA ${7.6}_{-0.1}^{+0.1}$?> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msubsup> <mml:mrow> <mml:mn>7.6</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>0.1</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>0.1</mml:mn> </mml:mrow> </mml:msubsup> </mml:math> , respectively. We perform spectral energy distribution fitting with a variety of codes (including bagpipes , prospector , beagle , and cigale ) and find a &gt;95% probability that these indeed lie at z &gt; 7. Both sources are compact ( R eff ≲ 200 pc) and highly obscured ( A V ∼ 1.5–2.5) and, at our best-fit redshift estimates, likely have strong [O iii ]+H β emission contributing to their 4.4 μ m photometry. We estimate stellar masses of ∼10 10 M ⊙ for both sources; by virtue of detection in MIRI at 7.7 μ 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 σ ) 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 ∼10 12 L ⊙ . These two galaxies, if confirmed at z ∼ 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. 

Two Massive, Compact, and Dust-obscured Candidate z ≃ 8 Galaxies Discovered by JWST

Using NOEMA and ALMA 3mm line scans, we measure spectroscopic redshifts of six new dusty galaxies at 3.5<z<4.2 by solidly detecting [CI](1-0) and CO transitions. The sample was selected from the COSMOS and GOODS-North super-deblended catalogs with FIR photometric redshifts z>6, based on template IR spectrum energy distribution (SED) from known submillimeter galaxies at z=4--6. Dust SED analyses explain the photo-z overestimate from seemingly cold dust temperatures (Td) and steep Rayleigh-Jeans (RJ) slopes, providing additional examples of cold dusty galaxies impacted by the Cosmic Microwave Background (CMB). We therefore study the general properties of the enlarged sample of 10 ``cold"dusty galaxies over 3.5<z<6. We conclude that these galaxies are deceivingly cold at the surface but actually warm in their starbursting cores. Several lines of evidence support this scenario: (1) The high infrared surface density and cold Td from optically thin models appear to violate the Stefan-Boltzmann law; (2) the gas masses derived from optically thin dust masses are inconsistent with estimates from dynamics and CI luminosities; (3) the implied high star formation efficiencies would conflict with cold Td; (4) high FIR optical depth is implied even using the lower, optically-thick dust masses. This work confirms the existence of a substantial population of deceivingly cold, compact dusty starburst galaxies at z>~4, together with the severe impact of the CMB on their RJ observables, paving the way for the diagnostics of optically thick dust in the early universe. Conventional gas mass estimates based on RJ dust continuum luminosities implicitly assume an optically thin case, overestimating gas masses by a factor of 2--3 on average in compact dusty star-forming galaxies.

/pdf/diagnosing-deceivingly-cold-dusty-galaxies-at-3-5-z-6-a-1l7vmo63.pdf

Diagnosing deceivingly cold dusty galaxies at 3.5<z<6: a substantial population of compact starbursts with high infrared optical depths

We report the discovery of a compact group of galaxies, CGG-z5, at z~5.2 in the EGS field covered by the JWST/CEERS survey. CGG-z5 was selected as the highest overdensity of galaxies at z>2 in recent JWST public surveys and it consists of six candidate members lying within a projected area of $1.5''\times3''$ (10$\times$20~kpc$^2$). All group members are HST/F435W and HST/F606W dropouts while securely detected in the JWST/NIRCam bands, yielding a narrow range of robust photometric redshifts $5.0<z<5.3$. The most massive galaxy in the group has a stellar mass log$(M_{*}/M_{\odot})\approx9.8$, while the rest are low-mass satellites (log$(M_{*}/M_{\odot})\approx8.4-9.2$). While several group members were already detected in the HST and IRAC bands, the low stellar masses and the compactness of the structure required the sensitivity and resolution of JWST for its identification. To assess the nature and evolutionary path of CGG-z5, we searched for similar compact structures in the \textsc{Eagle} simulations and followed their evolution with time. We find that all the identified structures merge into a single galaxy by z=3 and form a massive galaxy (log$(M_{*}/M_{\odot})>11$) at z~1. This implies that CGG-z5 could be a"proto-massive galaxy"captured during a short-lived phase of massive galaxy formation.

pdf/massive-galaxy-formation-caught-in-action-at-z-5-with-jwst-dwc4rpuh.pdf

Massive galaxy formation caught in action at z~5 with JWST

Using the novel James Webb Space Telescope (JWST)/NIRCam observations in the A2744 field, we present a first spatially resolved overview of a Hubble Space Telescope (HST)-dark galaxy, spectroscopically confirmed at z = 2.58 with magnification μ ≈ 1.9. While being largely invisible at ∼1 μm with NIRCam, except for sparse clumpy substructures, the object is well detected and resolved in the long-wavelength bands with a spiral shape clearly visible in F277W. By combining ancillary Atacama Large Millimeter/submillimeter Array (ALMA) and Herschel data, we infer that this object is an edge-on dusty spiral with an intrinsic stellar mass log (M */M ⊙) ∼ 11.3 and a dust-obscured star formation rate ∼300 M ⊙ yr−1. A massive quiescent galaxy (log (M */M ⊙) ∼ 10.8) with tidal features lies 2.″0 away (r ∼ 9 kpc), at a consistent redshift as inferred by JWST photometry, indicating a potential major merger. The dusty spiral lies on the main sequence of star formation, and shows high dust attenuation in the optical (3 < A V < 4.5). In the far-infrared, its integrated dust spectral energy distribution is optically thick up to λ 0 ∼ 500 μm, further supporting the extremely dusty nature. Spatially resolved analysis of the HST-dark galaxy reveals a largely uniform A V ∼ 4 area spanning ∼57 kpc2, which spatially matches to the ALMA 1 mm continuum emission. Accounting for the surface brightness dimming and the depths of current JWST surveys, unlensed analogs of the HST-dark galaxy at z > 4 would be only detectable in F356W and F444W in an UNCOVER-like survey, and become totally JWST-dark at z ∼ 6. This suggests that detecting highly attenuated galaxies in the Epoch of Reionization might be a challenging task for JWST.

JWST Insight into a Lensed HST-dark Galaxy and Its Quiescent Companion at z = 2.58

We report a galaxy group candidate HPC1001 at z ≈ 3 . 7 in the COSMOS ﬁeld. This structure was selected as a high galaxy overdensity at z > 3 in the COSMOS2020 catalog. It contains ten candidate members, of which eight are assembled in a 10 (cid:48)(cid:48) × 10 (cid:48)(cid:48) area with the highest sky density among known protoclusters and groups at z > 3. Four out of ten sources were also detected at 1.2 mm with Atacama Large Millimeter Array continuum observations. Photometric redshifts, measured by four independent methods, fall within a narrow range of 3 . 5 < z < 3 . 9 and with a weighted average of z = 3 . 65 ± 0 . 07. The integrated far-IR-to-radio spectral energy distribution yields a total UV and IR star formation rate SFR ≈ 900 M (cid:12) yr − 1 . We also estimated a halo mass of ∼ 10 13 M (cid:12) for the structure, which at this redshift is consistent with potential cold gas inﬂow. Remarkably, the most massive member has a speciﬁc star formation rate and dust to stellar mass ratio of M dust / M ∗ that are both signiﬁcantly lower than that of star-forming galaxies at this redshift, suggesting that HPC1001 could be a z ≈ 3 . 7 galaxy group in maturing phase. If conﬁrmed, this would be the earliest structure in maturing phase to date, and an ideal laboratory to study the formation of the earliest quiescent galaxies as well as cold gas accretion in dense environments. , cor : UV-corrected SFR from the COSMOS catalogs. a COSMOS2020 Farmer catalog ID. b We adopted z = 3 . 7 from the weighted average of the group. c This source is not in the COSMOS2020 catalog, and we list parameters from the COSMOS2015 catalog instead. d We did not account for HPC1001.h due to its inconsistency between SFR UV , cor and SFR IR .

https://export.arxiv.org/pdf/2209.05895v1.pdf

A galaxy group candidate at z ~ 3.7 in the COSMOS field

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Diagnosing deceivingly cold dusty galaxies at 3.5<z<6: a substantial population of compact starbursts with high infrared optical depths

Massive galaxy formation caught in action at z~5 with JWST

JWST Insight into a Lensed HST-dark Galaxy and Its Quiescent Companion at z = 2.58

A galaxy group candidate at z ~ 3.7 in the COSMOS field