Does absorption against AGN reveal supermassive black hole accretion?

Tom Rose, B. R. McNamara, F. Combes, A. C. Edge, A. C. Fabian, M. Gaspari, H. Russell, P. Salomé, G. Tremblay, G. Ferland

Research output: Contribution to journalArticlepeer-review

3 Scopus citations


Galaxies often contain large reservoirs of molecular gas that shape their evolution. This can be through cooling of the gas - which leads to star formation, or accretion on to the central supermassive black hole - which fuels active galactic nucleus (AGN) activity and produces powerful feedback. Molecular gas has been detected in early-type galaxies on scales of just a few tens to hundreds of solar masses by searching for absorption against their compact radio cores. Using this technique, ALMA has found absorption in several brightest cluster galaxies, some of which show molecular gas moving towards their galaxy's core at hundreds of km s-1. In this paper, we constrain the location of this absorbing gas by comparing each galaxy's molecular emission and absorption. In four galaxies, the absorption properties are consistent with chance alignments between the continuum and a fraction of the molecular clouds visible in emission. In four others, the properties of the absorption are inconsistent with this scenario. In these systems, the absorption is likely produced by a separate population of molecular clouds in close proximity to the galaxy core and with high inward velocities and velocity dispersions. We thus deduce the existence of two types of absorber, caused by chance alignments between the radio core and: (i) a fraction of the molecular clouds visible in emission, and (ii) molecular clouds close to the AGN, in the process of accretion. We also present the first ALMA observations of molecular emission in S555, Abell 2390, RXC J1350.3+0940, and RXC J1603.6+1553 - with the latter three having Mmol > 1010 Mθ.

Original languageEnglish
Pages (from-to)878-892
Number of pages15
JournalMonthly Notices of the Royal Astronomical Society
Issue number1
StatePublished - Jan 1 2023

Bibliographical note

Funding Information:
TR thanks the Waterloo Centre for Astrophysics and generous funding to BRM from the Canadian Space Agency and the National Science and Engineering Research Council of Canada. ACE ac- knowledges support from Science and Technology Facilities Council (STFC) grant ST/P00541/1. MG acknowledges partial support by HST GO-15890.020/023-A and the BlackHoleWeather program. HRR acknowledges support from an STFC Ernest Rutherford Fel- lowship and an Anne McLaren Fellowship. PS acknowledges support by the Agence Nationale De La Recherche (ANR) grant LYRICS (ANR-16-CE31-0011). This paper makes use of the following ALMA data: 2017.1.00629.S, 2021.1.00766.S, 2016.1.01214.S, 2012.1.00988.S, 2018.1.01471.S, 2011.0.00735.S, and 2015.1.01572.S. ALMA is a partnership of ESO (representing its member states), NSF (USA) and NINS (Japan), together with NRC (Canada), MOST and ASIAA (Taiwan), and KASI (Republic of Korea), in cooperation with the Republic of Chile. The Joint ALMA Observatory is operated by ESO, A UI/NRA O, and NA OJ. In addition, publications from NA authors must include the standard NRAO acknowledgement: The National Radio Astronomy Observatory is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc. This research made use of ASTROPY (The Astropy Collaboration 2013, 2018 ), MATPLOTLIB (Hunter 2007 ), NUMPY (van der Walt, Colbert & Varoquaux 2011 ; Harris et al. 2020 ), PYTHON (Van Rossum & Drake 2009 ), SCIPY (Jones, Oliphant & Peterson 2011 ; Virtanen et al. 2020 ), and APLPY (Robitaille & Bressert 2012 ). We thank their developers for maintaining them and making them freely available.

Publisher Copyright:
© 2022 The Author(s).


  • ISM: molecules
  • galaxies: ISM
  • quasars: absorption lines

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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