We report the discovery of an accreting supermassive black hole at
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Abstract z = 8.679. This galaxy, denoted here as CEERS_1019, was previously discovered as a Lyα -break galaxy by Hubble with a Lyα redshift from Keck. As part of the Cosmic Evolution Early Release Science (CEERS) survey, we have observed this source with JWST/NIRSpec, MIRI, NIRCam, and NIRCam/WFSS and uncovered a plethora of emission lines. The Hβ line is best fit by a narrow plus a broad component, where the latter is measured at 2.5σ with an FWHM ∼1200 km s−1. We conclude this originates in the broadline region of an active galactic nucleus (AGN). This is supported by the presence of weak high-ionization lines (N V, N IV], and C III]), as well as a spatial point-source component. The implied mass of the black hole (BH) is log (M BH/M ⊙) = 6.95 ± 0.37, and we estimate that it is accreting at 1.2 ± 0.5 times the Eddington limit. The 1–8μ m photometric spectral energy distribution shows a continuum dominated by starlight and constrains the host galaxy to be massive (log M/M⊙∼9.5) and highly star-forming (star formation rate, or SFR ∼ 30 M⊙yr−1; log sSFR ∼ − 7.9 yr−1). The line ratios show that the gas is metal-poor (Z /Z ⊙∼ 0.1), dense (n e ∼ 103cm−3), and highly ionized (logU ∼ − 2.1). We use this present highest-redshift AGN discovery to place constraints on BH seeding models and find that a combination of either super-Eddington accretion from stellar seeds or Eddington accretion from very massive BH seeds is required to form this object. -
ABSTRACT We present initial results from the Cosmic Ultraviolet Baryon Survey (CUBS). CUBS is designed to map diffuse baryonic structures at redshift z ≲ 1 using absorption-line spectroscopy of 15 UV-bright QSOs with matching deep galaxy survey data. CUBS QSOs are selected based on their NUV brightness to avoid biases against the presence of intervening Lyman limit systems (LLSs) at zabs < 1. We report five new LLSs of $\log \, N({\mathrm{ H} \,{\small I}})/{{\rm cm^{-2}}}\gtrsim 17.2$ over a total redshift survey path-length of $\Delta \, z_{\mathrm{ LL}}=9.3$, and a number density of $n(z)=0.43_{-0.18}^{+0.26}$. Considering all absorbers with $\log \, N({{\mathrm{ H} \,{\small I}}})/{{\rm cm^{-2}}}\gt 16.5$ leads to $n(z)=1.08_{-0.25}^{+0.31}$ at zabs < 1. All LLSs exhibit a multicomponent structure and associated metal transitions from multiple ionization states such as C ii, C iii, Mg ii, Si ii, Si iii, and O vi absorption. Differential chemical enrichment levels as well as ionization states are directly observed across individual components in three LLSs. We present deep galaxy survey data obtained using the VLT-MUSE integral field spectrograph and the Magellan Telescopes, reaching sensitivities necessary for detecting galaxies fainter than $0.1\, L_*$ at d ≲ 300 physical kpc (pkpc) in all five fields. A diverse range of galaxy properties is seen around these LLSs, from a low-mass dwarf galaxy pair, a co-rotating gaseous halo/disc, a star-forming galaxy, a massive quiescent galaxy, to a galaxy group. The closest galaxies have projected distances ranging from d = 15 to 72 pkpc and intrinsic luminosities from ${\approx} 0.01\, L_*$ to ${\approx} 3\, L_*$. Our study shows that LLSs originate in a variety of galaxy environments and trace gaseous structures with a broad range of metallicities.more » « less
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Abstract We present rest-frame optical emission-line flux ratio measurements for five
z > 5 galaxies observed by the James Webb Space Telescope Near-Infared Spectrograph (NIRSpec) in the SMACS 0723 Early Release Observations. We add several quality-control and post-processing steps to the NIRSpec pipeline reduction products in order to ensure reliablerelative flux calibration of emission lines that are closely separated in wavelength, despite the uncertainabsolute spectrophotometry of the current version of the reductions. Compared toz ∼ 3 galaxies in the literature, thez > 5 galaxies have similar [Oiii ]λ 5008/Hβ ratios, similar [Oiii ]λ 4364/Hγ ratios, and higher (∼0.5 dex) [NeIII ]λ 3870/[OII ]λ 3728 ratios. We compare the observations to MAPPINGS V photoionization models and find that the measured [NeIII ]λ 3870/[OII ]λ 3728, [Oiii ]λ 4364/Hγ , and [Oiii ]λ 5008/Hβ emission-line ratios are consistent with an interstellar medium (ISM) that has very high ionization ( , units of cm s−1), low metallicity (Z /Z ⊙≲ 0.2), and very high pressure ( , units of cm−3). The combination of [Oiii ]λ 4364/Hγ and [Oiii ]λ (4960 + 5008)/Hβ line ratios indicate very high electron temperatures of , further implying metallicities ofZ /Z ⊙≲ 0.2 with the application of low-redshift calibrations for “T e -based” metallicities. These observations represent a tantalizing new view of the physical conditions of the ISM in galaxies at cosmic dawn.