CO(J=1-0) Mapping Survey of 64 Galaxies in the Fornax Cluster with the ALMA Morita Array

We conduct a 12C16O(J = 1−0) (hereafter CO) mapping survey of 64 galaxies in the Fornax cluster using the Atacama Large Millimeter/submillimeter Array Morita array in cycle 5. CO emission is detected from 23 out of the 64 galaxies. Our sample includes dwarf, spiral, and elliptical galaxies with stellar masses of Mstar ∼ 106.3−11.6 Me. The achieved beam size and sensitivity are 15″ × 8″ and ∼12 mJy beam−1 at the velocity resolution of ∼10 km s−1, respectively. We study the cold gas (molecular and atomic gas) properties of 38 subsamples with Mstar > 109 Me combined with literature H I data. We find that (1) the low star formation (SF) activity in the Fornax galaxies is caused by the decrease in the cold gas mass fraction with respect to stellar mass (hereafter, gas fraction) rather than the decrease of the SF efficiency from the cold gas; (2) the atomic gas fraction is more heavily reduced than the molecular gas fraction of such galaxies with low SF activity. A comparison between the cold gas properties of the Fornax galaxies and their environmental properties suggests that the atomic gas is stripped tidally and by the ram pressure, which leads to the molecular gas depletion with an aid of the strangulation and consequently SF quenching. Preprocesses in the group environment would also play a role in reducing cold gas reservoirs in some Fornax galaxies.Ministry of Education, Culture, Sports, Science and Technology, Japan (MEXT) Japan Society for the Promotion of ScienceGrants-in-Aid for Scientific Research (KAKENHI) 16H02158 JP17K14259 18H03717 19K03937 19J40004 19H01931 19H05076 20H05861 21H01128 21H04496Sumitomo Foundation 180923Collaboration Funding of the Institute of Statistical Mathematics "New Development of the Studies on Galaxy Evolution with a Method of Data Science"Ministry of Science and Innovation, Spain (MICINN) Spanish Government BG20/00224 MCIN/AEI PID2020-114414GB-100 PID2020-113689GB-I00Junta de Andalucia P20_00334FEDER/Junta de Andalucia-Consejeria de Transformacion Economica, Industria, Conocimiento y Universidades A-FQM-510-UGR20European Research Council (ERC) 679627 882793Australian Research Council CE170100013Korea Astronomy and Space Science Institute - Korean government (MSIT) 2022-1- 840-05National Aeronautics & Space Administration (NASA