论文标题
附近星系的多行成像（即将到来）。 X.分子气和局部SFR质量关系的物理条件
CO Multi-line Imaging of Nearby Galaxies (COMING). X. Physical conditions of molecular gas and the local SFR-Mass relation
论文作者
论文摘要
We investigate the molecular gas properties of galaxies across the main sequence of star-forming (SF) galaxies in the local Universe using $^{12}$CO($J=1-0$) (hereafter $^{12}$CO) and $^{13}$CO($J=1-0$) ($^{13}$CO) mapping data of 147 nearby galaxies obtained in the COMING project, a Nobeyama无线电天文台的遗产项目。为了提高这两条线的信噪比，我们堆叠所有像素，其中$^{12} $ CO排放将在对齐从$^{12} $ co的第一张矩映射中预期的线中心。结果，在80个星系中成功检测到$^{13} $ CO排放，其信噪比大于三。 $^{12} $ co至$^{13} $ co行（$ r_ {1213} $）的集成强度比的错误加权平均值为$ 10.9 $，标准偏差为$ 7.0 $。我们发现（1）$ r_ {1213} $与特定的星形形态率（SSFR）正相关，相关系数为$ 0.46 $，（2）IRAS 60〜 $ M $ M至100〜 $ M（$ F_ {60}/f_ {60}/f_ {100} $的$ $ $ m至100〜 $ m $ $ m $ m $ m $ m $ m $ m $ $ $ m的通量比，$堆叠的光谱（$σ_{{\ rm ^{12} co}，i} $）与SSFR相关，用于星系中的银河系，$ r_ {1213} $ semalurome。我们的结果支持$ r_ {1213} $变化的方案，主要是由温度和湍流等分子气体特性的变化引起的。 SF主序列中Co-to-H $ _2 $转换因子的随之而来的变化不足以完全消除SSFR和$ M _ {\ rm mol}/M _ {\ rm mol}/m _ {\ rm star} $（$ _ _ _ _ {\ rm mol} $ {\ rm mol} $）或Star-Formation（s s flow）（在以前ssfr-sfe（ssfr- $μ_ {\ rm mol} $）相关性。
We investigate the molecular gas properties of galaxies across the main sequence of star-forming (SF) galaxies in the local Universe using $^{12}$CO($J=1-0$) (hereafter $^{12}$CO) and $^{13}$CO($J=1-0$) ($^{13}$CO) mapping data of 147 nearby galaxies obtained in the COMING project, a legacy project of the Nobeyama Radio Observatory. In order to improve signal-to-noise ratios of both lines, we stack all the pixels where $^{12}$CO emission is detected after aligning the line center expected from the first-moment map of $^{12}$CO. As a result, $^{13}$CO emission is successfully detected in 80 galaxies with a signal-to-noise ratio larger than three. The error-weighted mean of integrated-intensity ratio of $^{12}$CO to $^{13}$CO lines ($R_{1213}$) of the 80 galaxies is $10.9$ with a standard deviation of $7.0$. We find that (1) $R_{1213}$ positively correlates to specific star-formation rate (sSFR) with a correlation coefficient of $0.46$, and (2) both flux ratio of IRAS 60~$μ$m to 100~$μ$m ($f_{60}/f_{100}$) and inclination-corrected linewidth of $^{12}$CO stacked spectra ($σ_{{\rm ^{12}CO},i}$) also correlate with sSFR for galaxies with the $R_{1213}$ measurement. Our results support the scenario where $R_{1213}$ variation is mainly caused by the changes in molecular-gas properties such as temperature and turbulence. The consequent variation of CO-to-H$_2$ conversion factor across the SF main sequence is not large enough to completely extinguish the known correlations between sSFR and $M_{\rm mol}/M_{\rm star}$ ($μ_{\rm mol}$) or star-formation efficiency (SFE) reported in previous studies, while this variation would strengthen (weaken) the sSFR-SFE (sSFR-$μ_{\rm mol}$) correlation.
