The James Webb Space Telescope is revealing a new population of dust-reddened broad-line active galactic nuclei (AGN) at redshifts
The James Webb Space Telescope (JWST) is revolutionizing our knowledge of
- PAR ID:
- 10562342
- Author(s) / Creator(s):
- ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; more »
- Publisher / Repository:
- DOI PREFIX: 10.3847
- Date Published:
- Journal Name:
- The Astrophysical Journal
- Volume:
- 978
- Issue:
- 1
- ISSN:
- 0004-637X
- Format(s):
- Medium: X Size: Article No. 92
- Size(s):
- Article No. 92
- Sponsoring Org:
- National Science Foundation
More Like this
-
Abstract z ≳ 5. Here we present deep NIRSpec/Prism spectroscopy from the Cycle 1 Treasury program Ultradeep NIRSpec and NIRCam ObserVations before the Epoch of Reionization (UNCOVER) of 15 AGN candidates selected to be compact, with red continua in the rest-frame optical but with blue slopes in the UV. From NIRCam photometry alone, they could have been dominated by dusty star formation or an AGN. Here we show that the majority of the compact red sources in UNCOVER are dust-reddened AGN: 60% show definitive evidence for broad-line Hα with a FWHM > 2000 km s−1, 20% of the current data are inconclusive, and 20% are brown dwarf stars. We propose an updated photometric criterion to select redz > 5 AGN that excludes brown dwarfs and is expected to yield >80% AGN. Remarkably, among allz phot> 5 galaxies with F277W – F444W > 1 in UNCOVER at least 33% are AGN regardless of compactness, climbing to at least 80% AGN for sources with F277W – F444W > 1.6. The confirmed AGN have black hole masses of 107–109M ⊙. While their UV luminosities (−16 >M UV> −20 AB mag) are low compared to UV-selected AGN at these epochs, consistent with percent-level scattered AGN light or low levels of unobscured star formation, the inferred bolometric luminosities are typical of 107–109M ⊙black holes radiating at ∼10%–40% the Eddington limit. The number densities are surprisingly high at ∼10−5Mpc−3mag−1, 100 times more common than the faintest UV-selected quasars, while accounting for ∼1% of the UV-selected galaxies. While their UV faintness suggests they may not contribute strongly to reionization, their ubiquity poses challenges to models of black hole growth. -
Abstract We present a search for extremely red, dust-obscured,
z > 7 galaxies with JWST/NIRCam+MIRI imaging over the first 20 arcmin2of 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 and , respectively. We perform spectral energy distribution fitting with a variety of codes (includingbagpipes ,prospector ,beagle , andcigale ) and find a >95% probability that these indeed lie atz > 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 [Oiii ]+Hβ emission contributing to their 4.4μ m photometry. We estimate stellar masses of ∼1010M ⊙for both sources; by virtue of detection in MIRI at 7.7μ m, these measurements are robust to the inclusion of bright emission lines, for example, from an active galactic nucleus. We identify a marginal (2.9σ ) 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 ∼1012L ⊙. These two galaxies, if confirmed atz ∼ 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. -
Abstract 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 ofL bol= 1044–47erg s−1and fainter UV magnitudesM 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% forM UV∼ − 22 atz ∼ 7. Finally, assuming a conservative case of accretion at the Eddington rate, we place a lower limit on the SMBH mass function atz ∼ 5, finding it to be consistent with both theory and previous JWST observations. -
Abstract We report the discovery of two companion sources to a strongly lensed galaxy SPT0418-47 (“ring”) at redshift 4.225, targeted by the JWST Early Release Science program. We confirm that these sources are at a similar redshift to the ring based on H
α detected in the NIRSpec spectrum and [Cii ]λ 158μ m line from the Atacama Large Millimeter/submillimeter Array (ALMA). Using multiple spectral lines detected in JWST/NIRSpec, the rest-frame optical to infrared images from NIRCam and MIRI and far-infrared dust continuum detected by ALMA, we argue that the newly discovered sources are actually lensed images of the same companion galaxy SPT0418-SE, hereafter referred to “SE,” located within 5 kpc in the source plane of the ring. The star formation rate derived using [Cii ] and the dust continuum puts a lower limit of 17M ☉yr−1, while the SFRHα is estimated to be >2 times lower, thereby confirming that SE is a dust-obscured star-forming galaxy. Analysis using optical strong line diagnostics suggests that SE has near-solar elemental abundance, while the ring appears to have supersolar metallicity O/H and N/O. We attempt to reconcile the high metallicity in this system by invoking early onset of star formation with continuous high star-forming efficiency or by suggesting that optical strong line diagnostics need revision at high redshift. We suggest that SPT0418-47 resides in a massive dark-matter halo with yet-to-be-discovered neighbors. This work highlights the importance of joint analysis of JWST and ALMA data for a deep and complete picture of the early universe. -
Direct-collapse black holes (DCBHs) of mass ∼104 − 105
M ⊙that form in HI-cooling halos in the early Universe are promising progenitors of the ≳109M ⊙supermassive black holes that fuel observedz ≳ 7 quasars. Efficient accretion of the surrounding gas onto such DCBH seeds may render them sufficiently bright for detection with the JWST up toz ≈ 20. Additionally, the very steep and red spectral slope predicted across the ≈1 − 5 μm wavelength range of the JWST/NIRSpec instrument during their initial growth phase should make them photometrically identifiable up to very high redshifts. In this work, we present a search for such DCBH candidates across the 34 arcmin2in the first two spokes of the JWST cycle-1 PEARLS survey of the north ecliptic pole time-domain field covering eight NIRCam filters down to a maximum depth of ∼29 AB mag. We identify two objects with spectral energy distributions consistent with theoretical DCBH models. However, we also note that even with data in eight NIRCam filters, objects of this type remain degenerate with dusty galaxies and obscured active galactic nuclei over a wide range of redshifts. Follow-up spectroscopy would be required to pin down the nature of these objects. Based on our sample of DCBH candidates and assumptions on the typical duration of the DCBH steep-slope state, we set a conservative upper limit of ≲5 × 10−4comoving Mpc−3(cMpc−3) on the comoving density of host halos capable of hosting DCBHs with spectral energy distributions similar to the theoretical models atz ≈ 6 − 14.