
 JWST is discovering star forming ‘candidate’ galaxies with photometric redshifts z > 9 and little attenuation. We model presumptive massive black holes (MBHs) in such galaxies and find that their unobscured emission is fainter than the galaxy starlight in JWST filters, and difficult to be detected via color-color selection, and X-ray and radio observations. Only MBHs overmassive relative to expected galaxy scaling relations, accreting at high Eddington rates, would be detectable. Their discovery would point to the presence of heavy MBH seeds, but care is needed to exclude the existence of lighter seeds as only overmassive MBHs are detectable in this type of galaxies. Conversely, if no overmassive MBHs are hosted in these galaxies, either there are no heavy seeds or they are rare. The most massive/highest redshift candidate galaxies can attain stellar masses in excess of 5 × 1010 M⊙ by z ∼ 6 if they grow along the SFR-mass sequence, and can nurse a MBH growing from ∼105 M⊙ up to >3 × 107 M⊙ by z ∼ 6, to become hosts of some z > 6 quasars. Candidate galaxies of log (Mgal/ M⊙) ∼ 8 can not grow their putative seeds fast, unless seeds are ≳ 106 M⊙. The number density of the JWST candidate galaxies far outnumbers that of the highest-z quasar hosts and this allows for about only 1 bright z ∼ 6 − 7 quasar every 1000 of these galaxies.

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What if young z > 9 JWST galaxies hosted massive black holes?

The JWST discovery of a number of super-early (redshift z > 10) blue galaxies requires these systems to be essentially dust free in spite of their large stellar masses. A possible explanation is that dust is evacuated by radiatively driven outflows. We test this hypothesis by deriving the Eddington ratio λ E = L bol/L E , where L bol is the bolometric luminosity produced by star formation and possible black hole accretion, for 134 galaxies at 6.5 < z < 16. We find a strong anticorrelation between λ E and dust UV optical depth, τ1500∝λE−0.63; also, λ E increases with redshift. We confirm that galaxies exceeding a specific star formation rate sSFR > 13 Gyr−1 develop powerful outflows clearing the galaxy from its dust. This result is supported by ALMA dust continuum nondetections in three super-early systems.

https://iopscience.iop.org/article/10.3847/2041-8213/acb5f2/pdf

Dusty-wind-clear JWST Super-early Galaxies

During the first 500 million years of cosmic history, the first stars and galaxies formed and seeded the cosmos with heavy elements. These early galaxies illuminated the transition from the cosmic"dark ages"to the reionization of the intergalactic medium. This transitional period has been largely inaccessible to direct observation until the recent commissioning of JWST, which has extended our observational reach into that epoch. Excitingly, the first JWST science observations uncovered a surprisingly high abundance of early star-forming galaxies. However, the distances (redshifts) of these galaxies were, by necessity, estimated from multi-band photometry. Photometric redshifts, while generally robust, can suffer from uncertainties and/or degeneracies. Spectroscopic measurements of the precise redshifts are required to validate these sources and to reliably quantify their space densities, stellar masses, and star formation rates, which provide powerful constraints on galaxy formation models and cosmology. Here we present the results of JWST follow-up spectroscopy of a small sample of galaxies suspected to be amongst the most distant yet observed. We confirm redshifts z>10 for two galaxies, including one of the first bright JWST-discovered candidates with z = 11.4, and show that another galaxy with suggested z ~ 16 instead has z = 4.9, with strong emission lines that mimic the expected colors of more distant objects. These results reinforce the evidence for the rapid production of luminous galaxies in the very young Universe, while also highlighting the necessity of spectroscopic verification for remarkable candidates.

Spectroscopic verification of very luminous galaxy candidates in the early universe

The James Webb Space Telescope, planned to extend the scientific discoveries of the Hubble Space Telescope, will be a powerful observational tool for the investigation of the first stars and galaxies. With a 6.5‐m hexagonal mirror cooled to ∼40 K, and an instrument package covering 0.6 to 28 μm with imaging, spectroscopy with R up to ∼3000, and coronography, it will be capable of observing predicted primeval objects down to flux levels of a few nJy (10 σ) at 2 μm. Operated like the Hubble telescope from the Space Telescope Science Institute in Baltimore, it will be available for general observers by proposals, to be solicited a year before launch. It has a required lifetime of 5 years and fuel for 10.

The James Webb Space Telescope Mission

Black holes with masses in excess of several billion solar masses have been found at redshifts 6-7.5, when the universe was less than 1 Gyr old. The existence of such supermassive black holes already in place at such early epochs has been challenging for theoretical models and distinguishing between different scenarios has prompted the search for their progenitors at earlier epochs. Here we present an extensive analysis of the JWST-NIRSpec spectrum (from the JADES survey) of GN-z11, an exceptionally luminous galaxy at z=10.6, revealing the detection of the high ionization [NeIV]$\lambda$2423 transition and semi-forbidden nebular lines tracing gas densities higher than $\rm 10^{10}~cm^{-3}$, typical of the Broad Line Region of Active Galactic Nuclei (AGN). These spectral features indicate that, in addition to star formation, GN-z11 also hosts an accreting black hole. We do not exclude a contribution from extreme stellar populations, however Wolf Rayet stars alone cannot account for many of the spectral properties. The spectrum also reveals a deep and blueshifted CIV$\lambda$1549 absorption trough, tracing an outflow with a velocity of $\sim 800-1000$ km/s, higher than typically observed in starburst galaxies, hence likely driven by the AGN. Assuming local virial scaling relations, we derive a black hole mass of $\rm \log{(M_{BH}/M_{\odot})}=6.2\pm 0.3$, accreting at about 5 times the Eddington rate. While super-Eddington accretion is probably episodic, if it has been occurring for the previous $\sim 100$ Myr, then the black hole could have potentially originated even from a stellar mass seed at z$\sim$12-15. We finally discuss that our finding naturally explains the high luminosity of GN-z11 and can also provide an explanation for its exceptionally high nitrogen abundance.

A small and vigorous black hole in the early Universe

We report a candidate of a low-luminosity active galactic nucleus (AGN) at z = 5 that was selected from the first near-infrared images of the JWST CEERS project. This source, named CEERS-AGN-z5-1 at absolute 1450 Å magnitude M 1450 = −19.5 ± 0.3, was found via a visual selection of compact sources from a catalog of Lyman break galaxies at z > 4, taking advantage of the superb spatial resolution of the JWST/NIRCam images. The 20 photometric data available from CFHT, Hubble Space Telescope, Spitzer, and JWST suggest that the continuum shape of this source is reminiscent of that for an unobscured AGN, and there is a clear color excess in the filters where the redshifted Hβ+[O iii] and Hα are covered. The estimated line luminosity is L Hβ+[O III] = 1043.0 erg s−1 and L Hα = 1042.9 erg s−1 with the corresponding rest-frame equivalent width EWHβ+[O III] = 1100 Å and EWHα = 1600 Å, respectively. Our spectral energy distribution fitting analysis favors the scenario that this object is either a strong broad-line emitter or even a super-Eddington accreting black hole (BH), although a possibility of an extremely young galaxy with moderate dust attenuation is not completely ruled out. The bolometric luminosity, L bol = 2.5 ± 0.3 × 1044 erg s−1, is consistent with those of z < 0.35 broad-line AGNs with M BH ∼ 106 M ⊙ accreting at the Eddington limit. This new AGN population in the first 1.1 billion years of the universe may close the gap between the observed BH mass range at high redshift and that of BH seeds. Spectroscopic confirmation is awaited to secure the redshift and its AGN nature.

A Candidate for the Least-massive Black Hole in the First 1.1 Billion Years of the Universe

Abstract The passive sampling hypothesis is one of the most important hypotheses used to explain the mechanism of species–area relationships (SAR) formation. This hypothesis has not yet been experimentally validated due to the confusion between passive sampling (a larger area may support more colonists when fully sampled) and sampling effects (more sampling effort will result in increased species richness when sampling is partial). In this study, we created an open microcosm system with homogeneous habitat, consistent total resources, and biodiversity background using Chinese paocai soup, a fermented vegetable, as a substrate. We made efforts to entirely exclude the influence of sampling effects and to exclusively obtain microorganisms from dispersal using microcosm and high‐throughput sequencing techniques. However, in this study, passive sampling based on dispersal failed to shape SAR, and community differences were predominantly caused by species replacement, with only minor contributions from richness differences. Ecological processes including extinction and competitive exclusion, as well as underlying factors like temporal scales and the small island effects, are very likely to have been involved in the studied system. To elucidate the mechanism of SAR development, future studies should design experiments to validate the involvement of dispersal independently.

Passive sampling hypothesis did not shape microbial species–area relationships in open microcosm systems

We report on the discovery of two low-luminosity, broad-line active galactic nuclei (AGN) at z > 5 identiﬁed using JWST NIRSpec spectroscopy from the Cosmic Evolution Early Release Science (CEERS) Survey. We detect broad H α emission in the spectra of both sources, with FWHM of 2038 ± 286 and 1807 ± 207 km s − 1 , resulting in virial black hole (BH) masses that are 1-2 dex below that of existing samples of luminous quasars at z > 5. The ﬁrst source, CEERS 1670 at z = 5 . 242, is 2–3 dex fainter than known quasars at similar redshifts and was previously identiﬁed as a candidate low-luminosity AGN based on its morphology and rest-frame optical spectral energy distribution (SED). We measure a BH mass of M BH = 1 . 3 ± 0 . 4 × 10 7 M ⊙ , conﬁrming that this AGN is powered by the least-massive BH known in the universe at the end of cosmic reionization. The second source, CEERS 3210 at z = 5 . 624, is inferred to be a heavily obscured, broad-line AGN caught in a transition phase between a dust-obscured starburst and an unobscured quasar. We estimate its BH mass to be in the range of M BH ≃ 0 . 9 − 4 . 7 × 10 7 M ⊙ , depending on the level of dust obscuration assumed. We perform SED ﬁtting to derive host stellar masses, M ⋆ , allowing us to place constraints on the BH-galaxy mass relationship in the lowest mass range yet probed in the early universe. The M BH / M ⋆ ratio for CEERS 1670, in particular, is consistent with or higher than the empirical relationship seen in massive galaxies at z = 0. We examine the narrow emission-line ratios of both sources and ﬁnd that their location on the BPT and OHNO diagrams is consistent with model predictions for moderately low-metallicity AGN with Z / Z ⊙ ≃ 0 . 2 − 0 . 4. The spectroscopic identiﬁcation of low-luminosity, broad-line AGN at z > 5 with M BH ≃ 10 7 M ⊙ demonstrates the capability of JWST to push BH masses closer to the range predicted for the BH seed population and provides a unique opportunity to study the early stages of BH-galaxy assembly.

Zhengrong Li

Papers

A Candidate for the Least-massive Black Hole in the First 1.1 Billion Years of the Universe

Passive sampling hypothesis did not shape microbial species–area relationships in open microcosm systems

Hidden Little Monsters: Spectroscopic Identification of Low-Mass, Broad-Line AGN at $z>5$ with CEERS