THE WEAK CARBON MONOXIDE EMISSION IN AN EXTREMELY METAL-POOR GALAXY, SEXTANS A

Yong Shi*, Junzhi Wang, Yu Gao, Lee Armus, George Helou, Qiusheng Gu, Sabrina Stierwalt, Zhiyu Zhang

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

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 (alpha(CO)) from the CO luminosity to the molecular gas mass that is derived from the spatially resolved dust-mass map. The alpha(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.

Original languageEnglish
Article number11
Number of pages4
JournalAstrophysical Journal Letters
Volume804
Issue number1
DOIs
Publication statusPublished - 1 May 2015

Keywords

  • galaxies: dwarf
  • galaxies: ISM
  • submillimeter: ISM
  • CO-TO-H-2 CONVERSION FACTOR
  • STAR-FORMATION
  • LOW-METALLICITY
  • MOLECULAR GAS
  • DUST
  • MASS
  • CLOUDS
  • CO

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