Circumnuclear Medium around the Central AGN in a Cool-core Cluster, Abell 1644-South

Junhyun Baek, Aeree Chung, Alastair Edge, Tom Rose, Jae Woo Kim, Taehyun Jung

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We present the circumnuclear multiphase gas properties of the brightest cluster galaxy (BCG) in the center of Abell 1644-South (A1644-S). A1644-S is the main cluster in a merging system, which is well known for X-ray hot gas sloshing in its core. The sharply peaked X-ray profile of A1644-S implies the presence of a strongly cooling gas core. In this study, we analyze ALMA 12CO (1-0) data, JVLA H i data, and KaVA 22 GHz data for the central region of A1644-S to probe the potential origin of the cool gas and its role in (re)powering the central active galactic nucleus (AGN). We find CO clumps distributed in an arc shape along the X-ray gas sloshing, which is suggestive of a connection between the cold gas and the hot intracluster medium (ICM). H i and CN are detected in absorption against the AGN continuum emission. The absorption dip is observed at the systemic velocity of the BCG with an extended, redshifted tail. Based on the spatial and spectral configurations of the H i, CN, and CO gases, it is inferred that cool gas spirals into the core of the BCG, which is then fed to the central AGN. Indeed, our KaVA observation reveals a parsec-scale bipolar jet, implying that this AGN could have been (re)powered quite recently. Combining this, we suggest that some cold gas in A1644-S could have been formed from the cooling of the ICM, triggering the activity of the central AGN in the early development of a cool-core cluster.

Original languageEnglish
Article number64
JournalAstrophysical Journal
Issue number1
Publication statusPublished - 2022 Jun 1

Bibliographical note

Funding Information:
We thank the anonymous referee for his/her constructive comments and suggestions that helped to improve the paper. This work is based in part on observations made with the KaVA, which is operated by the Korea Astronomy and Space Science Institute and the National Astronomical Observatory of Japan. This study makes use of the following ALMA data: ADS/JAO.ALMA#2017.1.00629.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, 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. Support for this work was provided by the National Research Foundation of Korea (NRF), grant Nos. 2018R1D1A1B07048314 and 2022R1A2C1002982. J.B. acknowledges support by the Graduate School of YONSEI University Research Scholarship Grants in 2019. T.R. thanks the Waterloo Centre for Astrophysics and generous funding to Brian McNamara from the Canadian Space Agency and the National Science and Engineering Research Council of Canada. J.W.K. acknowledges support from the NRF (grant No. 2019R1C1C1002796) funded by the Korean government (MSIT).

Publisher Copyright:
© 2022. The Author(s). Published by the American Astronomical Society.

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science


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