The SCUBA-2 web survey: I. Observations of CO(3–2) in hyper-luminous QSO fields

Abstract

A primary goal of the SCUBA-2 Web survey is to perform tomography of the early inter-galactic medium by studying systems containing some of the brightest quasistellar objects (QSOs; 2.5 < z < 3.0) and nearby submillimetre galaxies. As a first step, this paper aims to characterize the galaxies that host the QSOs. To achieve this, a sample of 13 hyper-luminous (L AGN > 10 14 L ) QSOs with previous submillimetre continuum detections were followed up with CO(3-2) observations using the NOEMA interferometer. All but two of the QSOs are detected in CO(3-2); for one non-detection, our observations show a tentative 2σ line at the expected position and redshift, and for the other non-detection we find only continuum flux density an order of magnitude brighter than the other sources. In three of the fields, a companion potentially suitable for tomography is detected in CO line emission within 25 arcsec of the QSO. We derive gas masses, dynamical masses and far-infrared luminosities, and show that the QSOs in our sample have similar properties as compared to less luminous QSOs and SMGs in the literature, despite the fact that their black-hole masses (which are proportional to L AGN ) are 1-2 orders of magnitude larger. We discuss two interpretations of these observations: this is due to selection effects, such as preferential face-on viewing angles and picking out objects in the tail ends of the scatter in host-galaxy mass and blackhole mass relationships; or the black hole masses have been overestimated because the accretion rates are super-Eddington.

APEX at the QSO MUSEUM: molecular gas reservoirs associated with $z\sim$3 quasars and their link to the extended Ly$α$ emission

“…From these works, we know that at these redshifts, the low CO transitions (i.e., 𝐽 ≤ 3) are expected to be faint, and that the redshifted CO lines lie at challenging frequencies for current and past instruments. Past CO observations of 𝑧 ∼ 2 − 3 quasars found molecular gas masses in the range of ∼ 10 9 − 10 11 𝑀 , similar to those found for quasars at higher redshift (e.g., Barvainis et al 2002;Weiß et al 2003;Beelen et al 2004;Walter et al 2011;Schumacher et al 2012;Hill et al 2019;Bischetti et al 2021). These molecular reservoirs are characterized by densities of ∼ 10 3.0 −10 4.4 cm −3 and kinetic temperatures of ∼30 -90 K (Weiß et al 2003;Weiss et al 2007a;Schumacher et al 2012), and, when resolved, have an effective radius of ∼ 0.5 -2.5 kpc (e.g., Riechers et al 2009;Schumacher et al 2012;Stacey et al 2021).…”

“…We note that the range mentioned includes masses of the order of 10 12 M , which are implausible given the expected dark-matter halo mass for these quasars (𝑀 DM∼ 10 12.5 M , e.g., White et al 2012). These values are also much higher than the values found in the literature for other high-𝑧 quasars (∼10 9 -10 11 M , e.g., Weiß et al 2003;Walter et al 2011;Anh et al 2013;Hill et al 2019). These high masses are caused by models with densities of n H 2 ∼10 3 -10 3.8 cm −3 .…”

“…For quasars with IDs 7, 8, 13, 43 and 50, we found molecular gas masses < 1.5×10 11 M . Most of these molecular gas masses are higher than the typical range (∼10 9 -10 11 M ) found in the literature for other high-𝑧 quasars (e.g., Weiß et al 2003;Walter et al 2011;Anh et al 2013;Hill et al 2019). We list all these values in the fourth column of Table 4.…”

“…The grey area is the uncertainty on this expectation, for 1×MS. The histogram show the M H2 distribution for our sample considering the average values of the mass ranges (red), and for a sample of 𝑧 ∼2.5 -3 quasars (blue) extracted from the literature(Barvainis et al 2002;Weiß et al 2003;Beelen et al 2004;Walter et al 2011;Schumacher et al 2012;Hill et al 2019;Bischetti et al 2021), whose M H2 have been estimated with different molecular gas tracers and have a typical uncertainty of ∼ 0.1 dex.…”

Quantifying the thermal Sunyaev–Zel’dovich effect and excess millimetre emission in quasar environments

“…We compare our derived L CO values with expectations for quasars at low redshift (z 0.4, Evans et al 2006;Xia et al 2012) and high redshift (z 1, Walter et al 2003;Solomon & Vanden Bout 2005;Riechers et al 2006;Carilli et al 2007;Maiolino et al 2007;Coppin et al 2008;Wang et al 2010;Simpson et al 2012), submillimeter galaxies (Greve et al 2005;Frayer et al 2008;Daddi et al 2009;Ivison et al 2011;Bothwell et al 2013), and dusty star-forming galaxies (Greve et al 2014). All of these line luminosities have been corrected to represent L CO (1-0) (see Hill et al 2019 for more detail on the quasar and submm literature values). We correct our L CO values that are derived from higher energy transitions using the Carilli & Walter (2013) line ratios.…”