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arXiv:2404.11892v1 Announce Type: new
Abstract: We performed a $^{12}$CO- and $^{13}$CO($J=1-0$)-line study of the "Brick" (G0.253+0.016) in the Galactic Centre (GC) by analyzing the archival data obtained with the Nobeyama 45-m telescope. We present kinematics and molecular gas distributions in the longitude-velocity diagrams, and suggest that the Brick is located along the GC Arm I in the central molecular zone (CMZ) in front of the GC, which yields a distance of 8 kpc and GC radius 0.2 kpc. The major and minor-axis diameters of the Brick are $D_x\times D_y=8.4 \ {\rm pc} \times 4.1 \ {\rm pc}$, and the scale radius is $r_{\rm bri}=\sqrt{D_x D_y}=2.96$ pc. The molecular mass inferred from the CO-line integrated intensity is $M_{\rm brixco} \sim 5.1\times 10^4 M_\odot$ for a conversion factor $X_{\rm gc}=1.0\times 10^{20}$ H$_2$ cm$^{-2}$ [K km s$^{-1}$]$^{-1}$, while the Virial mass for the velocity dispersion of $\sigma_v=10.0 $ km s $^{-1}$ is calculated to be $M_{\rm brivir}\sim 6.8 \times 10^4 \ M_\odot$, which yields a new conversion factor of $X_{\rm bri} =1.3\times 10^{20}$ H$_2$ cm$^{-2}$ [K km s$^{-1}$]$^{-1}$. No thermal radio emission indicative of HII region and star formation is found in radio-continuum archive. The Brick's center has a cavity surrounded by a spherical molecular bubble of radius $r_{\rm bub}=1.85$ pc and mass $\sim 1.7\times 10^4 M_\odot$ expanding at $v_{\rm exp}=10$ km s$^{-1}$ with kinetic energy of $E_0\sim 1.7\times 10^{49}$ erg. If the bubble is approximated by an adiabatic spherical shock wave, its age is $t\sim 2/5 r_{\rm bub}/v_{\rm exp}\sim 7.2\times 10^4$ y. We suggest that the bubble will be a dark supernova remnant buried in the dense molecular cloud. The Brick, therefore, experienced massive-star formation followed by a supernova explosion more than $\sim 10^5$ y ago.