The Role of the Magnetic Field in the Circumnuclear Disk of the Galactic Center - Implications From 850 micron Polarization Data

Colloquium

Astronomy Colloquium (2019 Spring Semester)

* Date: May 16
* Speaker: Dr. Pei-Ying Hsieh (ASIAA)
* Title: The Role of the Magnetic Field in the Circumnuclear Disk of the Galactic Center – Implications From 850 micron Polarization Data
* Abstract

Utilizing James Clark Maxwell Telescope (JCMT) 850 micron SCUPOL dust polarization data, we investigate the configuration of the magnetic (B-) field in the circumnuclear disk (CND) of the Galactic Center (GC). Overall on a large scale, the B-field shows a clear predominantly toroidal morphology. Compared to earlier 100 micron and 350 micron observations, the SCUPOL data show a largely improved polarization coverage at a higher resolution. In general, the observed
B-field morphology is well described by a self-similar axisymmetric disk model where the radial infall velocity is one quarter of the rotational velocity. A detailed comparison with higher-resolution interferometric maps from the Submillimeter Array (SMA) further reveals that the B-field aligns with the neutral gas streamers where they are connecting to the CND. Moreover, the innermost observed B-field structure also appears to trace and align with the ionized mini-spirals located inside the CND. This suggests that there might be one underlying B-field structure that is connecting the CND with its streamers and the inner mini-spirals. An estimate of beta plasma parameter ~1 – based on the global B-field morphology that constrains the azimuthal-to-vertical field strength ratio to be around 40 combined with a measurement of the azimuthal velocity — indicates that the B-field appears dynamically significant towards the CND and also onwards to the inner mini-spirals.

Date	Speaker	Title	Remarks
March 7	No Colloquium	OT to the Seminar Course
March 14	Dr. Ena Choi (Columbia Unv.)	Making Massive Elliptical Galaxies
March 21	KASI ALMA TEAM	ALMA Cycle-7 proposal Townhall meeting
March 28	Prof. Changbom Park (KIAS)	Cosmology with Large-scale Structures in the Universe
April 4	Prof. Masateru Ishiguro (SNU)	Hirayama Family and Exploration of Asteroids
April 11	No colloquium	Korean Astronomical Society Spring Meeting
April 18	Prof. Sunghoon Jung (SNU)	Seeing Dark Matter with Gravitational Waves
April 25	Dr. Z. Lucas Uhm (KASI)	Physics of Relativistic Jets in Gamma-ray Bursts in the New Era of Multi-messenger Astrophysics
May 2	Prof. Jeong-Eun Lee (Kyung Hee Univ.)	Chemistry in Star and Planet Formation	Speech in Korean
May 9	Dr. Masa Imanishi (NAOJ)	ALMA reveals a rotating dense molecular torus in NGC 1068
May 16	Dr. Pei-Ying Hsieh (ASIAA)	The Role of the Magnetic Field in the Circumnuclear Disk of the Galactic Center – Implications From 850 micron Polarization Data
May 23	Prof. Sascha Trippe (SNU)	At the End of Space and Time: Imaging the Black Hole in M 87	Special colloquium on the recent result of the Event Horizon Telescope (EHT)
May 30	Naeun Shin (SNU)	대학원생이 바라본 해외교육지원단 3기 원정대 활동
June 6	No colloquium	Memorial Day
June 13	Dr. Shinsuke Takasao (NAGOYA Univ.)	Investigating the accretion process onto young stars using 3D MHD simulations

2019 Spring semester detail