CO-to-H_2 Conversion Factor of Molecular Clouds using X-Ray Shadows

Abstract

A new method to determine the CO-to-H${}_2$ conversion factor $X_{\mathrm{CO}}$ using absorption of diffuse X-ray emission by local molecular clouds was developed. It was applied to the Ophiucus (G353+17) and Corona Australis (G359-18) clouds using CO-line and soft X-ray archival data. We obtained a value $X_{\mathrm{CO}}=1.85\pm 0.45\times 10^{20}{\mathrm{H}}_2\mathrm{c}{\mathrm{m}}^{-2}/(\mathrm{K}\mathrm{km}{\mathrm{s}}^{-1})$ as the average of least-$ch{i}^2$ fitting results for R4 (0.7 keV) and R5 (0.8 keV) bands. Full resolution pdf available at http://www.ioa.s.u-tokyo.ac.jp/~sofue/htdocs/2016Xco/

6 pages,6 figures, 1 table, PASJ in press

References in corpus (3)

• Hipparcos distances of Ophiuchus and Lupus cloud complexes
• Local ISM 3D distribution and soft X-ray background: Inferences on nearby hot gas and the North Polar Spur
• ISMabs: a comprehensive X-ray absorption model for the interstellar medium

Cited by in corpus (3)

• CO-to-H${}_2$ Conversion and Spectral Column Density in Molecular Clouds: The Vriability of $X_{\mathrm{CO}}$ Factor
• Polarimetric and photometric investigation of a dark globule LDN 1225: distance, extinction law, and magnetic fields
• Giant Elephant Trunks from Giant Molecular Clouds