论文标题
以银河系的直接测量碳和硫同位素比率
Direct measurements of carbon and sulfur isotope ratios in the Milky Way
论文作者
论文摘要
使用IRAM 30米的望远镜，我们进行了观察到$ j $ = 2-1的CS，C $^{33} $ S，C $^{34} $ S，C $^{36} $ s，$^{13} $ CS，$ CS，$ CS，$^{13} $ c $ c $ c $^$ c $^33} $} $}以及$ j $ = 3-2的c $^{33} $ s的过渡，c $^{34} $ s，c $^{36} $ s和$^{13} $ cs，向110 hmsfrs的大量样本。我们测量了$^{12} $ c/$^{13} $ c，$^{32} $ s/$^{34} $ s，$^{32} $ s/$ s/$^{33} $ s，$^{32} $ s/$ s/$ s/$ s/$^{36} $ s，$ s，$ s，$ s，$^$^$ s/s/^$ s/s/s/s/s/^$ s/s/^$ s/s/^$ s/s/ $^{34} $ s/$^{36} $ s，$^{33} $ s/$^{36} $ s丰度比率具有CS的罕见同位素，从而避免了显着的饱和效果。通过从视差数据获得的准确距离，我们确认先前确定的$^{12} $ c/$ c/$^{13} $ c和$^{32} $ s/$ s/$^{34} $ s梯度是GalactCentric距离的函数（RGC）。在CMZ中，$^{12} $ c/$^{13} $ c比率高于线性拟合与磁盘值所建议的作为RGC的函数。而$^{32} $ s/$^{34} $ s比率在银河中心附近和内磁盘中相似，但对于$^{12} $ c/$ c/$^{13} $ c，在将中心值与附近RGC的RGC进行比较时，情况并非如此。众所周知，没有$^{34} $ s/$^{33} $ s梯度，但平均比率为4.35〜 $ \ pm $ 〜0.44，源自$ j $ = 2-1的c $^{34} $ s and c $ s and c $ s and c $^{33} $远低于以前报道的值以下的值。太阳能与本地星际$^{32} $ s/$^{34} $ s和$^{34} $ s/$ s/$^{33} $ s比率之间的比较表明，太阳系可能是通过GAS形成的，并以特别高的$^{34} $ s的含量形成。我们首次报告$^{32} $ s/$^{33} $ s，$^{34} $ s/$ s/$^{36} $ s，$^{33} $ s/$ s/$ s/$^{36} $ s，以及$^{36} $ s，以及$^{32} {32} {\ rm s} $ s的$ san} $ s的{最新GCE模型的预测$^{12} $ c/$^{13} $ c比率与我们的结果非常吻合。而$^{32} $ s/$^{34} $ s和$^{32} $ s/$^{36} $ s比值在较大的RGC时显示出更大的差异，$^{32} $ s/$ s/$^{33} $ s比率显示了整个12 kpc的内部12 kpc的偏移。
With the IRAM 30 meter telescope, we performed observations of the $J$ = 2-1 transitions of CS, C$^{33}$S, C$^{34}$S, C$^{36}$S, $^{13}$CS, $^{13}$C$^{33}$S, and $^{13}$C$^{34}$S as well as the $J$ = 3-2 transitions of C$^{33}$S, C$^{34}$S, C$^{36}$S, and $^{13}$CS toward a large sample of 110 HMSFRs. We measured the $^{12}$C/$^{13}$C, $^{32}$S/$^{34}$S, $^{32}$S/$^{33}$S, $^{32}$S/$^{36}$S, $^{34}$S/$^{33}$S, $^{34}$S/$^{36}$S, and $^{33}$S/$^{36}$S abundance ratios with rare isotopologs of CS, thus avoiding significant saturation effects. With accurate distances obtained from parallax data, we confirm previously identified $^{12}$C/$^{13}$C and $^{32}$S/$^{34}$S gradients as a function of galactocentric distance (RGC). In the CMZ, $^{12}$C/$^{13}$C ratios are higher than suggested by a linear fit to the disk values as a function of RGC. While $^{32}$S/$^{34}$S ratios near the Galactic center and in the inner disk are similar, this is not the case for $^{12}$C/$^{13}$C, when comparing central values with those near RGC of 5 kpc. As was already known, there is no $^{34}$S/$^{33}$S gradient but the average ratio of 4.35~$\pm$~0.44 derived from the $J$ = 2-1 transition lines of C$^{34}$S and C$^{33}$S is well below previously reported values. A comparison between solar and local interstellar $^{32}$S/$^{34}$S and $^{34}$S/$^{33}$S ratios suggests that the Solar System may have been formed from gas with a particularly high $^{34}$S abundance. For the first time, we report positive gradients of $^{32}$S/$^{33}$S, $^{34}$S/$^{36}$S, $^{33}$S/$^{36}$S, and $^{32}{\rm S}/^{36}{\rm S}$ in our Galaxy. The predicted $^{12}$C/$^{13}$C ratios from the latest GCE models are in good agreement with our results. While $^{32}$S/$^{34}$S and $^{32}$S/$^{36}$S ratios show larger differences at larger RGC, $^{32}$S/$^{33}$S ratios show an offset across the entire inner 12 kpc of the Milky Way.
