Polarized Dust Emission in the Massive Protocluster W3 IRS5
Vivien Huei-Ru Chen1*, Qizhou Zhang2, Chat Hull2
1Astronomy, National Tsing Hua University, Hsinchu, Taiwan
2Center for Astrophysics, Harvard-Smithsonian, Cambridge, MA, USA
* presenting author:Vivien Huei-Ru Chen, email:hchen@phys.nthu.edu.tw
Using the Submillimeter Array (SMA), we have observed both the polarized dust emission at 882 μm and the molecular emissions in a nearby (1.83 kpc) massive protocluster object, W3 IRS5, with angular resolution of ~2.7". W3 IRS 5 is in the course of developing a luminous proto-cluster with at least four hyper-compact (HC) HII regions and makes a much younger analogue to the Trapezium system. Our polarization maps show a pinched morphology while the CO emission suggests two pairs of bipolar outflows. In addition to strong emission in all sulfur-bearing species, two high-density tracers, H¹³CN (4-3) and H¹³CO+ (4-3), show greatly different velocity dispersions that are perhaps caused by the decoupling of neutral flows from magnetic fields due to ambipolar diffusion. We are developing radiative transfer models to interpret the observed polarized continuum emission with an hourglass geometry of magnetic field.

Keywords: star formation, magnetic field