부산대학교 도서관

We present Atacama Large Millimeter/sub-millimeter Array (ALMA) observations towards 27 low-redshift (0.02 < z < 0.2) star-forming galaxies taken from the Valparaíso ALMA/APEX Line Emission Survey. We perform stacking analyses of the 12CO(1–0), 13CO(1–0), and C18O(1–0) emission lines to explore the L ′ [12CO(1–0)]/ L ′ [13CO(1–0)] [hereafter L ′ (12CO)/ L ′ (13CO)] and L ′ [13CO(1–0)]/ L ′ [C18O(1–0)] [hereafter L ′ (13CO)/ L ′ (C18O)] line luminosity ratio dependence as a function of different global galaxy parameters related to the star formation activity. The sample has far-IR luminosities of |$10^{10.1\!-\!11.9}\,$|  L⊙ and stellar masses of 109.8–10.9 M⊙ corresponding to typical star-forming and starburst galaxies at these redshifts. On average, we find an L ′ (12CO)/ L ′ (13CO) line luminosity ratio value of 16.1 ± 2.5. Galaxies with pieces of evidence of possible merging activity tend to show higher L ′ (12CO)/ L ′ (13CO) ratios by a factor of 2, while variations of this order are also found in galaxy samples with higher star formation rates (SFRs) or star formation efficiencies (SFEs). We also find an average L ′ (13CO)/ L ′ (C18O) line luminosity ratio of 2.5 ± 0.6, which is in good agreement with those previously reported for starburst galaxies. We find that galaxy samples with high L IR, SFR, and SFE show low L ′ (13CO)/ L ′ (C18O) line luminosity ratios with high L ′ (12CO)/ L ′ (13CO) line luminosity ratios, suggesting that these trends are produced by selective enrichment of massive stars in young starbursts. [ABSTRACT FROM AUTHOR]