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Abstract Dual active galactic nuclei (AGNs), which are the manifestation of two actively accreting supermassive black holes (SMBHs) hosted by a pair of merging galaxies, are a unique laboratory for studying the physics of SMBH feeding and feedback during an indispensable stage of galaxy evolution. In this work, we present NOEMA CO(2–1) observations of seven kiloparsec-scale dual-AGN candidates drawn from a recent Chandra survey of low redshift, optically classified AGN pairs. These systems are selected because they show unexpectedly low 2–10 keV X-ray luminosities for their small physical separations signifying an intermediate-to-late stage of merger. Circumnuclear molecular gas traced by the CO(2–1) emission is significantly detected in six of the seven pairs and 10 of the 14 nuclei, with an estimated mass ranging between (0.2–21) × 109M⊙. The primary nuclei, i.e., the ones with the higher stellar velocity dispersion, tend to have a higher molecular gas mass than the secondary. Most CO-detected nuclei show a compact morphology, with a velocity field consistent with a kiloparsec-scale rotating structure. The inferred hydrogen column densities range between 5 × 1021–2 × 1023cm−2, but mostly at a few times 1022cm−2, in broad agreement with those derived from X-ray spectral analysis. Together with the relatively weak mid-infrared emission, the moderate column density argues against the prevalence of heavily obscured, intrinsically luminous AGNs in these seven systems, but favors a feedback scenario in which AGN activity triggered by a recent pericentric passage of the galaxy pair can expel circumnuclear gas and suppress further SMBH accretion.
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Black hole feeding and feedback in a compact galaxy
ABSTRACT We perform high-resolution hydrodynamical simulations using the framework of MACER to investigate supermassive black hole (SMBH) feeding and feedback in a massive compact galaxy, which has a small effective radius but a large stellar mass, with a simulation duration of 10 Gyr. We compare the results with a reference galaxy with a similar stellar mass but a less concentrated stellar density distribution, as typically found in local elliptical galaxies. We find that about 10 per cent of the time, the compact galaxy develops multiphase gas within a few kpc, but the accretion flow through the inner boundary below the Bondi radius is always a single phase. The inflow rate in the compact galaxy is several times larger than in the reference galaxy, mainly due to the higher gas density caused by the more compact stellar distribution. Such a higher inflow rate results in stronger SMBH feeding and feedback and a larger fountain-like inflow-outflow structure. Compared to the reference galaxy, the star formation rate in the compact galaxy is roughly two orders of magnitude higher but is still low enough to be considered quiescent. Over the whole evolution period, the black hole mass grows by ∼50 per cent in the compact galaxy, much larger than the value of ∼ 3 per cent in the reference galaxy.
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- Award ID(s):
- 2107735
- PAR ID:
- 10508579
- Publisher / Repository:
- Oxford University Press
- Date Published:
- Journal Name:
- Monthly Notices of the Royal Astronomical Society
- Volume:
- 523
- Issue:
- 2
- ISSN:
- 0035-8711
- Format(s):
- Medium: X Size: p. 1641-1647
- Size(s):
- p. 1641-1647
- Sponsoring Org:
- National Science Foundation
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