When spectral modeling meets convolutional networks: a method for discovering reionization-era lensed quasars in multiband imaging data

Instrumentatio

ALMA 200 pc imaging of a z ~ 7 quasar reveals a compact, disk-like host galaxy

Galaxie

Chemical abundance of z ~ 6 quasar broad-line regions in the XQR-30 sample

Galaxie

Suppression of black-hole growth by strong outflows at redshifts 5.8-6.6

Bright quasars, powered by accretion onto billion-solar-mass black holes, already existed at the epoch of reionization, when the Universe was 0.5-1 billion years old(1). How these black holes formed in such a short time isthe subject of debate, particularly asthey lie above the correlation between black-hole mass and galaxy dynamical mass(2,3) in the local Universe. What slowed down black-hole growth, leading towards the symbioticgrowth observed in the local Universe, and when this process started, has hitherto not been known, although black-hole feedback is a likely driver(4). Here we report optical and near-infrared observations of a sample of quasars at redshifts 5.8 less than or similar to z less than or similar to 6.6. About half ofthe quasar spectra reveal broad, blueshifted absorption line troughs, tracing black-hole-driven winds with extreme outflowvelocities, up to 17% of the speed of light. The fraction of quasars with such outflow winds at z greater than or similar to 5.8 approximate to 2.4 is times higher than at z approximate to 2-4. We infer that outflows at z greater than or similar to 5.8 inject large amounts of energy into the interstellar medium and suppress nuclear gas accretion, slowing down black-hole growth. The outflow phase may then mark the beginning of substantial black-hole feedback. The red optical colours of outflow quasars at z greater than or similar to 5.8 indeed suggest that these systems are dusty and may be caught during an initial quenching phase of obscured accretion(5).Galaxie

Constraining IGM enrichment and metallicity with the C IV forest correlation function

The production and distribution of metals in the diffuse intergalactic medium (IGM) have implications for galaxy formation models and the baryon (re)cycling process. The relative abundance of metals in high versus low-ionization states has also been argued to be sensitive to the Universe's reionization history. However, measurements of the background metallicity of the IGM at z~4 are sparse and in poor agreement with one another, and reduced sensitivity in the near-IR renders detecting individual metal absorbers nearly impossible. We present a new clustering-based technique that enables the detection of these weak IGM absorbers by statistically averaging over all spectral pixels, here applied to the C IV forest. We simulate the z=4.5 IGM with different models of inhomogeneous metal distributions and investigate its two-point correlation function (2PCF) using mock skewers of the C IV forest. The 2PCF demonstrates a clear peak at the doublet separation of the C IV line. The peak amplitude scales quadratically with metallicity, while enrichment morphology affects both the shape and amplitude of the 2PCF. The effect of enrichment topology can also be framed in terms of the metal mass- and volume-filling factors, and we show their trends as a function of the enrichment topology. For models consistent with the distribution of metals at z~3, we find that we can constrain [C/H] to within 0.2 dex, log$\,M_{\rm{min}}$ to within 0.4 dex, and $R$ to within 15%. We show that strong absorbers arising from the circumgalactic medium of galaxies can be easily identified and masked, allowing one to recover the underlying IGM signal. The auto-correlation of the metal-line forest presents a new and compelling avenue to simultaneously constrain IGM metallicity and enrichment topology with high precision at z>4, thereby pushing such measurements into the Epoch of Reionization.Comment: 19 pages, 17 figures, 1 appendix. Submitted to MNRA

Constraining IGM enrichment and metallicity with the C IV forest correlation function

Interstellar matter and star formatio

ALMA 200 pc Imaging of a z ∼7 Quasar Reveals a Compact, Disk-like Host Galaxy

We present 0.″035 resolution (∼200 pc) imaging of the 158 μm [C ii] line and the underlying dust continuum of the z = 6.9 quasar J234833.34-305410.0. The 18 hour Atacama Large Millimeter/submillimeter Array observations reveal extremely compact emission (diameter ∼1 kpc) that is consistent with a simple, almost face-on, rotation-supported disk with a significant velocity dispersion of ∼160 km s-1. The gas mass in just the central 200 pc is ∼4 × 109 M ⊙, about a factor of two higher than that of the central supermassive black hole. Consequently we do not resolve the black hole's sphere of influence, and find no kinematic signature of the central supermassive black hole. Kinematic modeling of the [C ii] line shows that the dynamical mass at large radii is consistent with the gas mass, leaving little room for a significant mass contribution by stars and/or dark matter. The Toomre-Q parameter is less than unity throughout the disk, and thus is conducive to star formation, consistent with the high-infrared luminosity of the system. The dust in the central region is optically thick, at a temperature >132 K. Using standard scaling relations of dust heating by star formation, this implies an unprecedented high star formation rate density of >104 M ⊙ yr-1 kpc-2. Such a high number can still be explained with the Eddington limit for star formation under certain assumptions, but could also imply that the central supermassive black hole contributes to the heating of the dust in the central 200 pc. © 2022. The Author(s). Published by the American Astronomical Society.Open access journalThis item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]

The X-shooter/ALMA sample of quasars in the epoch of reionization. II. Black hole masses, Eddington ratios, and the formation of the first quasars

High Energy AstrophysicsGalaxie