We have developed a method to make a spectral-line-based survey of hot cores, which represent an important stage of high-mass star formation, and applied the method to the data of the FUGIN (FOREST Unbiased Galactic plane Imaging survey with the Nobeyama 45-m telescope) survey. First, we select hot core candidates by searching the FUGIN data for the weak hot core tracer lines (HNCO and CH$_3$CN) by stacking, and then we conduct follow-up pointed observations on these candidates in C$^{34}$S, SO, OCS, HC$_3$N, HNCO, CH$_3$CN, and CH$_3$OH $J=2-1$ and $J=8-7$ lines to confirm and characterize them. We applied this method to the $l = 10^\circ-20^\circ$ portion of the FUGIN data and identified 22 "Hot Cores" (compact sources with more than two significant detection of the hot core tracer lines, i.e., SO, OCS, HC$_3$N, HNCO, CH$_3$CN, or CH$_3$OH $J=8-7$ lines) and 14 "Dense Clumps" (sources with more than two significant detection of C$^{34}$S, CH$_3$OH $J=2-1$, or the hot core tracer lines). The identified Hot Cores are found associated with signposts of high-mass star formation such as ATLASGAL clumps, WISE HII regions, and Class II methanol masers. For those associated with ATLASGAL clumps, their bolometric luminosity to clump mass ratios are consistent with the star formation stages centered at the hot core phase. The catalog of FUGIN Hot Cores provides a useful starting point for further statistical studies and detailed observations of high-mass star forming regions.
FOREST Unbiased Galactic Plane Imaging Survey with the Nobeyama 45-m Telescope (FUGIN) IV: Galactic Shock Wave and Molecular Bow Shock in the 4-kpc Arm of the Galaxy
FOREST Unbiased Galactic plane Imaging survey with the Nobeyama 45 m telescope (FUGIN). VI. Dense gas and mini-starbursts in the W43 giant molecular cloud complex
作为FUGIN项目的一部分,我们在盾板臂($l\sim {30^\circ}$)的切线方向上对W 43巨分子云复合体进行了新的大尺度$^{12}$ CO、$^{13}$ CO和C $^{18}$ O $J=$ 1- 0观测。由$^{12}$ CO示踪的低密度气体分布在150 pc $\times$ 100 pc($l \times b$)以上,并具有大的速度弥散(20-30 km s $^{-1}$)。然而,C $^{18}$ O追踪到的致密气体位于W 43 GMC复合体中的W 43 Main、G30.5和W 43 South(G29.96-0.02)高质量恒星形成区,这些区域具有星团结构。我们发现至少有两个云的速度差$\sim$ 1 - 0 -20公里秒$^{-1}$,这两个很可能是物理上与这些高质量的恒星形成区的高$^{13}$ CO $J=$ 3-2,$J =$ 1-0的强度比和形态对应的红外尘埃排放的结果的基础上。这些云在W 43 Main、G30.5和W 43 South的速度分离太大,以至于每个云都无法被引力束缚。与W51和M17 GMC相比,W 43 GMC的致密气体具有高的局部柱密度,而整个GMC的“当前SFE”($\sim 4\%$)较低。我们认为,超音速云-云碰撞假说可以解释W 43 GMC复合体中局部小爆发和致密气体形成的起源。
Constraints on the Hot Circumgalactic Medium around Nearby L* Galaxies from SRG/eROSITA All Sky Survey
School of Astronomy and Space Science, Nanjing University(南京大学天文与空间科学学院);Key Laboratory of Modern Astronomy and Astrophysics, Nanjing University(南京大学现代天文与天体物理重点实验室);Institute of Science and Technology for Deep Space Exploration, Suzhou Campus, Nanjing University(南京大学苏州校区深空探测研究院)
The hot circumgalactic medium of the Milky Way: evidence for super-virial, virial, and sub-virial temperature, non-solar chemical composition, and non-thermal line broadening