The Weak Carbon Monoxide Emission in an Extremely Metal-poor Galaxy, Sextans A

May 2015 • 2015ApJ...804L..11S

Authors • Shi, Yong • Wang, Junzhi • Zhang, Zhi-Yu • Gao, Yu • Armus, Lee • Helou, George • Gu, Qiusheng • Stierwalt, Sabrina

Abstract • Carbon monoxide (CO) is one of the primary coolants of gas and an easily accessible tracer of molecular gas in spiral galaxies, but it is unclear if CO plays a similar role in metal-poor dwarfs. We carried out a deep observation with IRAM 30 m to search for CO emission by targeting the brightest far-IR peak in a nearby extremely metal-poor galaxy, Sextans A, with 7% solar metallicity. A marginal signal of CO J = 1 - 0 emission is seen, which is already faint enough to place a strong constraint on the conversion factor ({{α }_CO}) from the CO luminosity to the molecular gas mass that is derived from the spatially resolved dust-mass map. The {{α }_CO} is at least seven hundred times the Milky Way value. This indicates that CO emission is exceedingly weak in Sextans A, challenging its role as a coolant in extremely metal-poor galaxies.

Based on observations carried out with the IRAM 30 m Telescope. IRAM is supported by INSU/CNRS (France), MPG (Germany), and IGN (Spain).

Links

• PREPRINT http://arxiv.org/abs/1504.01453
• NED https://ned.ipac.caltech.edu/uri/NED::InRefcode/2015ApJ...804L..11S
• ELECTR https://doi.org/10.1088%2F2041-8205%2F804%2F1%2FL11
• SIMBAD http://simbad.u-strasbg.fr/simbo.pl?bibcode=2015ApJ...804L..11S
• PDF https://iopscience.iop.org/article/10.1088/2041-8205/804/1/L11/pdf
• PDF https://stacks.iop.org/2041-8205/804/L11/pdf
• DATA https://archive.stsci.edu/mastbibref.php?bibcode=2015ApJ...804L..11S
• DATA https://irsa.ipac.caltech.edu/bibdata/2015/S/2015ApJ...804L..11S.html