Detecting and Characterizing Young Quasars. I. Systemic Redshifts and Proximity Zone Measurements

Abstract

In a multiwavelength survey of 13 quasars at 5.8z6.5, which were preselected to be potentially young, we find five objects with extremely small proximity zone sizes that may imply UV-luminous quasar lifetimes of 100,000 yr. Proximity zones are regions of enhanced transmitted flux in the vicinity of quasars that are sensitive to the quasars' lifetimes because the intergalactic gas has a finite response time to their radiation. We combine submillimeter observations from the Atacama Large Millimetre Array and the NOrthern Extended Millimeter Array, as well as deep optical and near-infrared spectra from the medium-resolution spectrograph on the Very Large Telescope and on the Keck telescopes, in order to identify and characterize these new young quasars, which provide valuable clues about the accretion behavior of supermassive black holes in the early universe and pose challenges on current black hole formation models to explain the rapid formation of billion-solar-mass black holes. We measure the quasars' systemic redshifts, black hole masses, Eddington ratios, emission-line luminosities, and star formation rates of their host galaxies. Combined with previous results, we estimate the fraction of young objects within the high-redshift quasar population at large to be 5%f young 10%. One of the young objects, PSO J158-14, shows a very bright dust continuum flux (F cont =3.46±0.02 mJy), indicating a highly starbursting host galaxy with a star formation rate of approximately 1420 M e yr −1 .

The first measurement of the quasar lifetime distribution

“…Moreover, an analysis of the composite H proximity zone profile of 15 quasars at 𝑧 6 points to an average on-time of 𝑡 on 0.50 +0.58 −0.25 Myr (Morey et al prep). This is consistent with finding newly turned on quasars with 𝑡 on ∼ 0.01-0.1 Myr approximately ∼ 1-10 % of the time (Eilers et al 2020).…”

“…at 𝑧 6 where the mostly opaque H Ly𝛼 forest far away from quasars (Fan et al 2006;Eilers et al 2018;Bosman et al 2018;Yang et al 2020b) provides a better contrast, and analysis of the quasar H proximity zones at 𝑧 6 has revealed several very young 𝑡 on 0.01-1 Myr quasars (Eilers et al 2017(Eilers et al , 2020. Moreover, an analysis of the composite H proximity zone profile of 15 quasars at 𝑧 6 points to an average on-time of 𝑡 on 0.50 +0.58 −0.25 Myr (Morey et al prep).…”

Cosmological Simulations of Quasar Fueling to Subparsec Scales Using Lagrangian Hyper-refinement

“…The four FIRE-2 massive halos simulated in Anglés-Alcázar et al (2017c) all show a similar phase of extreme nuclear densities, reaching Σ gas > 10 10.5 M e kpc −2 and Σ å > 10 12 M e kpc −2 on ∼10 pc scales, suggesting that all massive halos undergo at least one phase conducive to a luminous QSO (e.g., Soltan 1982;Yu & Tremaine 2002;Shankar et al 2009). Constraints on QSO lifetimes from black hole demographics (e.g., Yu & Tremaine 2002), clustering (e.g., Martini & Weinberg 2001;White et al 2012), radiation proximity effects (e.g., Trainor & Steidel 2013;Eilers et al 2017Eilers et al , 2020Schmidt et al 2017), gas fueling arguments (Martini et al 2003), and others vary from ∼0.1-100 Myr (Martini 2004), though there is indication that AGN flicker on shorter timescales (Schawinski et al 2015;Sartori et al 2018). In the full-QSO phase, we measure an inflow rate of ∼6 M e yr −1 at <0.1 pc almost in steady state during the full ∼4 Myr duration of the simulation, with no sign of decline.…”

SMBH seeds from dissipative dark matter

“…However, even in these models, an Eddington-limit accretion has to be sustained for most of the lifetime of the seeds, which implies a very high duty-cycle of SMBHs in the early Universe. Thus, such a scenario is hard to reconcile with some of the massive quasars at z 6 with low measured Eddington ratios [26,27] as well as the short quasar lifetimes (∼ 10 4−5 yr) found in observations of quasar proximity zones at z ∼ 6 [28][29][30][31][32].…”