Speaker: Xing Lu
Institute: Shanghai Astronomical Observatory
Host: Min Du
Time: 14:30-16:30, Thursday, June, 2
Location: Physics Building 552 (online)
Current protostellar evolution models often consider protostars as well as protostellar disks as isolated objects, but interactions between protostars and disks should be frequent especially toward protoclusters, which should not be ignored. It is essential to constrain properties of such star-disk interactions from observations, so as to better inform the models. Such interactions, or better known as 'flybys', have been suggested for protoplanetary disks surrounding low-mass protostars. For the first time, we extend this paradigm to massive star forming regions, and find that flybys are also impacting the evolution of a massive disk around an early O-type protostar. Using high sensitivity, ultra-high resolution ALMA longbaseline observations, we spatially resolve a massive disk down to 300 AU, and detect spiral patterns in it. Through a thorough quantitative analysis that combines both analytical and numerical approaches, we find compelling evidence that the most likely scenario to create the spirals is through a close flyby of a gas condensation that is detected next to the disk. The detection of the Keplerian disk itself, combined with the flyby event caught in action, suggests that early O-type protostars may form in a similar way to low-mass stars, subject to not only disk-mediated accretion, but also flyby-impact disk evolution.
Xing Lu is an associated researcher at Shanghai Astronomical Observatory. His research focusses on observations of star formation in massive molecular clouds in the Galaxy, by using interferometers such as ALMA, SMA, and JVLA. He obtained a PhD degree in astrophysics in 2016 at Nanjing University and was awarded the excellent thesis prize of Jiangsu Province. He also visited Harvard-Smithsonian Center for Astrophysics as an SMA predoctoral fellow in 2012-2015. In 2016-2021, he worked in the ALMA Project of National Astronomical Observatory of Japan as an ALMA project research fellow, and participated in on-site observations, science goal projections, and proposal reviews of ALMA. He has published nine first-authored papers in ApJ, ApJL, and ApJS, and has obtained Grade-A ALMA projects (the highest priority, usually top 5% of all projects) four times. These projects include the longest baseline (16 km), high frequency (0.5 THz), and polarization modes, all of which are high-risk/high-reward tasks for ALMA. His research achievements have been highlighted by the ALMA observatory, NAOJ, Nature, NSF, among other media.