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17th of January 2024
ATNF Colloquium
ALMA CO surveys of the Fornax cluster and the Eridanus supergroup
Kana Morokuma (University of Tokyo)
Abstract: The evolution of galaxies is affected by their surrounding environment. The star formation (SF) in galaxies in galaxy clusters is known to be less active compared to those in the normal field. In order to understand the SF quenching processes in cluster galaxies, we conducted CO(J=1-0) mapping survey of 64 Fornax cluster galaxies and 103 Eridanus supergroup galaxies using the Morita array of ALMA in cycles 5 and 7, respectively. The Fornax cluster is the 2nd nearest galaxy cluster from the Milky Way at a distance of 20 Mpc. The Eridanus supergroup is located near the Fornax cluster and is an ensemble of galaxy groups that are expected to be a single cluster in the future. For the Fornax cluster, the achieved beam size and sensitivity are 15′′ × 8′′ and ~12 mJy/beam1 at the velocity resolution of ∼10 km/s, respectively. CO emission is detected from 23 out of the 64 galaxies. We find the low SF activity in the cluster galaxies is attributed to the low molecular gas contents of galaxies. The SF efficiency from molecular gas, a ratio of SF rate over molecular gas mass, in the Fornax galaxies is comparable to that of field galaxies. Combined with archival HI data, we also find that the atomic-gas reservoirs are more heavily reduced than the molecular-gas reservoirs in the Fornax galaxies with low SF activity. In this colloquium, I will present the preliminary results for the Eridanus supergroup galaxies.

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