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arXiv · 2308.06750

CO-CHANGES I: IRAM 30m CO Observations of Molecular Gas in the Sombrero Galaxy

Yan Jiang·Jiang-Tao Li·Yu Gao·Joel N. Bregman·Li Ji·Xuejian Jiang·Qinghua Tan·Jianfa Wang·Q. Daniel Wang·Yang Yang
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Abstract

Molecular gas plays a critical role in explaining the quiescence of star formation (SF) in massive isolated spiral galaxies, which could be a result of either the low molecular gas content and/or the low SF efficiency. We present IRAM 30m observations of the CO lines in the Sombrero galaxy (NGC~4594), the most massive spiral at $d\lesssim30\rm~Mpc$. We detect at least one of the three CO lines covered by our observations in all 13 observed positions located at the galactic nucleus and along a $\sim25\rm~kpc$-diameter dusty ring. The total extrapolated molecular gas mass of the galaxy is $M_{\rm H_2}\approx4\times10^{8}\rm~M_\odot$. The measured maximum CO gas rotation velocity of $\approx379\rm~km~s^{-1}$ suggests that NGC~4594 locates in a dark matter halo with a mass $M_{\rm200}\gtrsim10^{13}\rm~M_\odot$. Comparing to other galaxy samples, NGC~4594 is extremely gas poor and SF inactive, but the SF efficiency is apparently not inconsistent with that predicted by the Kennicutt-Schmidt law, so there is no evidence of enhanced SF quenching in this extremely massive spiral with a huge bulge. We also calculate the predicted gas supply rate from various sources to replenish the cold gas consumed in SF, and find that the galaxy must experienced a starburst stage at high redshift, then the leftover or recycled gas provides SF fuels to maintain the gradual growth of the galactic disk at a gentle rate.

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Yan Jiang, Jiang-Tao Li, Yu Gao, Joel N. Bregman, Li Ji, Xuejian Jiang, Qinghua Tan, Jianfa Wang, Q. Daniel Wang, Yang Yang. 2023-08-15. CO-CHANGES I: IRAM 30m CO Observations of Molecular Gas in the Sombrero Galaxy. https://doi.org/10.1093/mnras%2Fstad2473

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