Abstract
We present 3 mm observations of the quasar J0015+1842 at z = 2.63 with the NOrthern Extended Millimeter Array (NOEMA). Our data reveal molecular gas, traced with a Gaussian CO(3–2) line, with a remarkably high velocity dispersion (FWHM = 1010 ± 120 km s−1) that corresponds to a total molecular mass MH2 ≈ (3.4 − 17) × 1010 M⊙, depending on the adopted CO-to-H2 conversion factor αCO = (0.8 − 4.0) M⊙ (km s−1 pc2)−1. Assuming the 3 mm continuum emission is thermal, we derive a dust mass of about Mdust ∼ 5 × 108 M⊙. J0015+1842 is located in the molecular gas-rich region in the IR versus CO line luminosity diagram, in between the main locus of main-sequence and sub-millimetre galaxies and that of most other active galactic nuclei targeted so far for CO measurements. While the high velocity dispersion of the CO line suggests a merging system, J0015+1842 is observed to be a regular, only very moderately dust-reddened (AV ∼ 0.3 − 0.4) type I quasar from its UV-optical spectrum, from which we infer a mass of the super-massive black hole of about MBH ≈ 6 × 108 M⊙. We suggest that J0015+1842 is observed at a galaxy evolutionary stage where a massive merger has brought significant amounts of gas towards an actively accreting super-massive black hole (quasar). While the host still contains a large amount of dust and molecular gas with a high velocity dispersion, the quasar has already cleared the way towards the observer, likely through powerful outflows, as has recently been revealed by optical observations of the same object. High angular resolution observations of this and similar systems are expected to help us better determine the respective importance of evolution and orientation in the appearance of quasars and their host galaxies. These observations have the potential to investigate early feedback and star-formation processes in galaxies in their quasar phases.
Highlights
There is accumulating evidence for a strong link between the evolution of massive galaxies and the super-massive black hole (SMBH) that they generally host in their centre (e.g., Heckman et al 2004)
While the high velocity dispersion of the CO line suggests a merging system, J0015+1842 is observed to be a regular, only very moderately dust-reddened (AV ∼ 0.3−0.4) type I quasar from its UV-optical spectrum, from which we infer a mass of the super-massive black hole of about MBH ≈ 6 × 108 M
We suggest that J0015+1842 is observed at a galaxy evolutionary stage where a massive merger has brought significant amounts of gas towards an actively accreting super-massive black hole
Summary
There is accumulating evidence for a strong link between the evolution of massive galaxies and the super-massive black hole (SMBH) that they generally host in their centre (e.g., Heckman et al 2004). The energy that is released could be sufficient to significantly clear dust and gas from the entire galaxy through powerful winds Such a feedback mechanism could be responsible for quenching star formation in the host (e.g., Zubovas & King 2012; Pontzen et al 2017; Terrazas et al 2020), the observed large-scale outflows may not necessarily arise from propagation of energy from the accretion disc to the interstellar medium (Fabian 2012; Veilleux et al 2017), that is, be powered by activity from the active galactic nucleus (AGN), but might result from the intense starformation activity or tidal ejection during the merging phase (e.g., Puglisi et al 2021). We discuss these exceptional characteristics for an otherwise apparently regular quasar and suggest that the orientation of this system allows us to observe early AGN feedback during or after a merger phase
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