2024/04/22 by Amanda M Lee, Jin Koda, Lee, Amanda M +7 · 2 citations
Physics and Astronomy · #Astronomy and Astrophysical Research #Astrophysics and Star Formation Studies #Astrophysics of Galaxies (astro-ph.GA) #FOS: Physical sciences #Stellar, planetary, and galactic studies
paper · pdf · doi:10.48550/arxiv.2404.14503
openalex publication_date 2024/04/22 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
We analyze the CO-to-H2 conversion factor (α_\rmCO) in the nearby barred spiral galaxy M83. We present new HI observations from the JVLA and single-dish GBT in the disk of the galaxy, and combine them with maps of CO(1-0) integrated intensity and dust surface density from the literature. α_\rmCO and the gas-to-dust ratio (δ_\rmGDR) are simultaneously derived in annuli of 2 kpc width from R = 1-7 kpc. We find that α_\rmCO and δ_\rmGDR both increase radially, by a factor of ∼ 2-3 from the center to the outskirts of the disk. The luminosity-weighted averages over the disk are α_\rmCO = 3.14 (2.06, 4.96) M\odot pc-2[K⋅ km s-1]-1 and δ_\rmGDR = 137 (111, 182) at the 68% (1σ) confidence level. These are consistent with the α_\rmCO and δ_\rmGDR values measured in the Milky Way. In addition to possible variations of α_\rmCO due to the radial metallicity gradient, we test the possibility of variations in α_\rmCO due to changes in the underlying cloud populations, as a function of galactic radius. Using a truncated power-law molecular cloud CO luminosity function and an empirical power-law relation for cloud-mass and luminosity, we show that the changes in the underlying cloud population may account for a factor of ∼ 1.5-2.0 radial change in α_\rmCO.