Abstract
We present new ALMA observations of CO, CN, CS, HCN, and HCO+ absorption seen against the bright and compact radio continuum sources of eight galaxies. Combined with archival observations, they reveal two distinct populations of molecular clouds, which we identify by combining CO emission and absorption profiles to unambiguously reveal each cloud’s direction of motion and likely location. In galaxy discs, we see clouds with low velocity dispersions, low line-of-sight velocities, and a lack of any systemic inflow or outflow. In galactic cores, we find high velocity dispersion clouds inflowing at up to 550 km s−1. This provides observational evidence in favour of cold accretion on to galactic centres, which likely contributes to the fuelling of active galactic nuclei. We also see a wide range in the CO(2-1)/CO(1-0) ratios of the absorption lines. This is likely the combined effect of hierarchical substructure within the molecular clouds and continuum sources which vary in size with frequency.
| Original language | English |
|---|---|
| Pages (from-to) | 771-794 |
| Number of pages | 24 |
| Journal | Monthly Notices of the Royal Astronomical Society |
| Volume | 533 |
| Issue number | 1 |
| DOIs | |
| State | Published - Sep 1 2024 |
Bibliographical note
Publisher Copyright:© 2024 The Author(s).
Funding
We are very grateful to the anonymous reviewer for their time and helpful comments, which helped us to improve the clarity of the paper. We thank Tom Oosterloo for providing the H I spectrum of NGC 6868 and Seiji Kameno for helpful discussions when analysing the ALMA data of NGC 1052. We also thank Jeff Mangum for helpful discussions on column densities. 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 acknowledges support from Science and Technology Facilities Council (STFC) grant ST/T000244/1. HRR acknowledges support from an STFC Ernest Rutherford Fellowship and an Anne McLaren Fellowship. PS acknowledges support by the Agence Nationale de la Recherche (ANR) grant LYRICS (ANR-16-CE31-0011). This paper uses the following ALMA data: 2017.1.00629.S, 2021.1.00766.S, 2018.1.01471, 2018.1.00581, 2013.1.00229, 2012.1.00988, 2011.0.00735, 2015.1.00591, 2015.1.01290, 2013.1.01225, 2016.1.00375, 2017.1.00301, and 2017.1.01638. 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, AUI/NRAO, and NAOJ. The National Radio Astronomy Observatory is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc. Some of this work is based on observations carried out with the IRAM Interferometer NOEMA under project W22CK. IRAM is supported by INSU/CNRS (France), MPG (Germany), and IGN (Spain). This research used 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. We are very grateful to the anonymous reviewer for their time and helpful comments, which helped us to improve the clarity of the paper. We thank Tom Oosterloo for providing the H\u2009 i spectrum of NGC 6868 and Seiji Kameno for helpful discussions when analysing the ALMA data of NGC 1052. We also thank Jeff Mangum for helpful discussions on column densities. 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 acknowledges support from Science and Technology Facilities Council (STFC) grant ST/T000244/1. HRR acknowledges support from an STFC Ernest Rutherford Fellowship and an Anne McLaren Fellowship. PS acknowledges support by the Agence Nationale de la Recherche (ANR) grant LYRICS (ANR-16-CE31-0011).
| Funders | Funder number |
|---|---|
| Waterloo Centre for Astrophysics | |
| U.S. Department of Energy Chinese Academy of Sciences Guangzhou Municipal Science and Technology Project Oak Ridge National Laboratory Extreme Science and Engineering Discovery Environment National Science Foundation National Energy Research Scientific Computing Center National Natural Science Foundation of China | |
| National Astronomical Observatory of Japan (NAOJ) | |
| INSU | |
| Ministry of Science and Technology, Taiwan | |
| ASIAA (Taiwan) | |
| Oak Ridge Associated Universities | |
| Canadian Space Agency | |
| Natural Sciences and Engineering Research Council of Canada | |
| National Institutes of Natural Sciences, National Institute for Physiological Sciences | |
| National Radio Astronomy Observatory | |
| National Research Council Canada (NRCC) | |
| UK Industrial Decarbonization Research and Innovation Centre | |
| Korea Astronomy and Space Science Institute | |
| CNRS Centre National de la Recherche Scientifique | 2020 |
| Agence Nationale de la Recherche | 2017.1.00629, 2015.1.00591, 2017.1.01638, 2013.1.00229, 2012.1.00988, ANR-16-CE31-0011, 2021.1.00766, 2013.1.01225, 2015.1.01290, 2018.1.00581, 2016.1.00375, 2017.1.00301, 2018.1.01471, 2011.0.00735 |
| Science and Technology Facilities Council | ST/T000244/1 |
Keywords
- galaxies: active
- galaxies: clusters: general
- radio continuum: galaxies
- radio lines: ISM
ASJC Scopus subject areas
- Astronomy and Astrophysics
- Space and Planetary Science