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SHAO Astrophysics Colloquia

 

Title: An early transition to magnetic supercriticality in star formation

Speaker: Tao-Chung Ching (庆道冲,字法天, NAOC)

Time: Thursday, 3:00pm, Dec. 30th

Location: Lecture Hall, 3rd floor

Abstract: Magnetic fields play an important role in the evolution of interstellar medium and star  formation. As the only direct tracer of interstellar field strength, credible Zeeman measurements remain sparse due to rather limited number of spectral lines with discernible Zeeman effect, particularly for cold, molecular gas. Here we report the detection of a magnetic  field of +3.8 ± 0.3 μG through the HI narrow self-absorption (HINSA) toward the prestellar core L1544. A combined analysis of the Zeeman measurements of quasar HI absorption, HI emission, OH emission, and HINSA reveals a coherent magnetic field from the atomic cold neutral medium (CNM) to the molecular envelope of the L1544. We find that the molecular envelope traced by HINSA is already magnetically supercritical, with a field strength comparable to that in the surrounding diffuse, magnetically subcritical CNM despite a large  increase in density. The reduction of the magnetic flux relative to the mass, necessary for star  formation, thus seems to happen during the transition from the diffuse CNM to the molecular gas traced by HINSA , earlier than envisioned in the classical picture where magnetically supercritical cores capable of collapsing into stars form out of magnetically subcritical envelopes.(Nature Accepted)

 
 
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  天体物理研究室是上海天文台从事基础天体物理研究的主要机构,包括12个科研团组。研究室的研究方向涉及黑洞和高能天体物理、星系形成与演化、宇宙大尺度 结构、星团和银河系结构、恒星形成、以及行星天体物理等领域,在黑洞吸积与喷流理论、黑洞和星系的共同演化、银河系结构与动力学、计算天体物理等方向具有一定的国际影响力。研究室现有固定研究人员固定研究人员50名,博士后20名,研究生80名。固定研究人员中包括国家杰出青年基金获得者、优秀青年基金获得者、国家高层次引进人才,科学院高层次引进人才。
  研究室与国内外的天文研究机构有着密切的合作关系,与中国科技大学联合成立了“中国科学院星系和宇宙学重点实验室”,与厦门大学成立了天体物理联合中心,与北京大学成立了中国科学院上海天文台联合天体物理研究中心。研究室还参与了多项国际、国内天文项目和观测计划,如LAMOST、HXMT、SDSS-IV、TMT、LSST、FAST等。
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