膨胀的CO谱线气泡揭示银河系中心“砖块”G0.253+0.016中埋藏的暗超新星遗迹
Dark supernova remnant buried in the Galactic-Centre "Brick" G0.253+0.016 revealed by an expanding CO-line bubble
AI总结：
本文利用CO谱线数据研究银河系中心“砖块”G0.253+0.016，发现其内部存在一个膨胀的分子气泡，并将其解释为埋藏在其中的暗超新星遗迹，表明该区域约0.1 Myr前曾发生大质量恒星形成和超新星爆发。
摘要：
我们通过分析野边山45米望远镜获得的档案数据，对银河系中心（GC）的“砖块”（G0.253+0.016）进行了12CO和13CO谱线研究。我们在经度-速度图中展示了运动学和分子气体分布，并提出“砖块”位于中央分子区（CMZ）的GC Arm I沿线，由此得到的日心距离为8 kpc，银心距为0.2 kpc。“砖块”的长轴和短轴直径分别为$D_x\times D_y=8.4 {\rm pc} \times 4.1 {\rm pc}$，位置角分别为$40°$和$130°$，其标度半径为$r_{\rm brick}=\sqrt{D_x D_y}=2.96$ pc。由12CO谱线积分强度推得的分子质量为$M_{\rm bri,xco}\sim 5.1\times 10^4 M_\odot$，采用的转换因子为$X_{\rm CO}=1.0\times 10^{20}$ H$_2$ cm$^{-2}$ [K km/s]$^{-1}$。另一方面，对于测得的速度弥散$\sigma_v=10.0$ km/s，计算得到的动力学（维里）质量为$M_{\rm bri,vir}\sim 6.8 \times 10^4M_\odot$，由此得到新的转换因子$X_{\rm CO} =1.3\times 10^{20}$ H$_2$ cm$^{-2}$ [K km/s]$^{-1}$。“砖块”中心存在一个空腔，周围被一个半径为$r_{\rm bub}=1.85$ pc、质量约为$1.7\times 10^4M_\odot$的球形分子气泡包围，该气泡以$v_{\rm exp}\simeq 10$ km/s的速度膨胀，动能约为$E_0\sim 1.7\times 10^{49}$ erg。如果将气泡近似为绝热球形激波，则其年龄估计为$t\sim 2/5 r_{\rm bub}/v_{\rm exp}\sim 7.2\times 10^4$年。在MeerKAT的档案数据中，既未发现非热射电结构，也未发现指示HII区的热射电辐射。我们认为该分子气泡是一个埋藏在“砖块”中的暗超新星遗迹，因此“砖块”在过去（约0.1 Myr前）经历过伴随超新星爆发的大质量恒星形成。
英文摘要：
We performed a 12CO and 13CO-line study of the "Brick" (G0.253+0.016) in the Galactic Centre (GC) by analyzing archival data obtained with the Nobeyama 45-m telescope. We present kinematics and molecular gas distributions in the longitude-velocity diagram, and suggest that the Brick is located along the GC Arm I in the central molecular zone (CMZ), which yields a distance from the Sun of 8 kpc and galacto-centric distance of 0.2 kpc. The major and minor-axis diameters of the Brick are $D_x\times D_y=8.4 {\rm pc} \times 4.1 {\rm epc}$ at position angle of $40°$ and $130°$, respectively, and the scale radius is $r_{\rm brick}=\sqrt{D_x D_y}=2.96$ pc. The molecular mass inferred from the 12CO-line integrated intensity is $M_{\rm bri,xco}\sim 5.1\times 10^4 M_\odot$ for a conversion factor $X_{\rm CO}=1.0\times 10^{20}$ H$_2$ cm$^{-2}$ [K km/s]$^{-1}$. On the other hand, the dynamical (Virial) mass for the measured velocity dispersion of $σ_v=10.0 $ km/s is calculated to be $M_{\rm bri,vir}\sim 6.8 \times 10^4M_\odot$, which yields a new conversion factor of $X_{\rm CO} =1.3\times 10^{20}$ H$_2$ cm$^{-2}$ [K km/s]${-1}$. The Brick's center has a cavity surrounded by a spherical molecular bubble of radius $r_{\rm bub}=1.85$ pc and mass $\sim 1.7\times 10^4M_\odot$ expanding at $v_{\rm exp}\simeq 10 $ km/s with kinetic energy of $E_0\sim 1.7\times 10^{49}$ erg. If the bubble is approximated by an adiabatic spherical shock wave, the age is estimated to be $t\sim 2/5 r_{\rm bub}/v_{\rm exp}\sim 7.2\times 10^4$ y. Neither non-thermal radio structures nor thermal radio emission indicative of HII region are found in the archival data from the MeerKAT. We suggest that the molecular bubble will be a dark supernova remnant buried in the Brick, which, therefore, has experienced in the past ($\sim 0.1$ Myr ago) massive-star formation with a supernova explosion.
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