标题： $^{13}CO(J = 1 -- 0)$亮星暴合并中的抑郁 显示英文标题

标题： $^{13}CO(J = 1 -- 0)$ Depression in Luminous Starburst Mergers

摘要： It is known that the class of luminous starburst galaxies tends to have higher $R =^{12}CO(J=1--0)/^{13}CO(J=1--0)$ integrated line intensity ratios ($R>20$) than normal spiral galaxies ($R \sim 10$). Since most previous studies investigated only $R$, it remains uncertain whether the luminous starburst galaxies are overabundant in $^{12}$CO or underabundant in $^{13}$CO. Here we propose a new observational test to examine this problem. 我们的新测试是将远红外光度 [$L$(FIR)] 与$^{12}$CO 和$^{13}CO [L(^{12}CO)$和$L(^{13}CO)$分别进行比较。 结果显示，$L(^{12}CO)$与 L(FIR) 之间存在非常紧密的相关性，正如许多先前研究中发现的那样。 然而，我们发现高 R 星系的$^{13}$CO 光度平均比其余具有普通$R$值星系的预期值低三倍。 因此，我们得出结论，观测到的明亮星爆星系的高$R$值是由于它们较低的$^{13}$CO谱线强度。 显示英文摘要

摘要： It is known that the class of luminous starburst galaxies tends to have higher $R =^{12}CO(J=1--0)/^{13}CO(J=1--0)$ integrated line intensity ratios ($R>20$) than normal spiral galaxies ($R \sim 10$). Since most previous studies investigated only $R$, it remains uncertain whether the luminous starburst galaxies are overabundant in $^{12}$CO or underabundant in $^{13}$CO. Here we propose a new observational test to examine this problem. Our new test is to compare far-infrared luminosities [$L$(FIR)] with those of $^{12}$CO and $^{13}CO [L(^{12}CO)$ and $L(^{13}CO)$, respectively]. It is shown that there is a very tight correlation between $L(^{12}CO)$ and L(FIR), as found in many previous studies. However, we find that the $^{13}$CO luminosities of the high-R galaxies are lower by a factor of three on the average than those expected from the correlation for the remaining galaxies with ordinary $R$ values. Therefore, we conclude that the observed high $R$ values for the luminous starburst galaxies are attributed to their lower $^{13}$CO line intensities.