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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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