Submillimeter Array Observations of Molecular Outflows in Massive Star Forming Regions

Keping Qiu

Harvard-Smithsonian Center for Astrophysics

Qizhou Zhang and the SMA team

It has been years since we know that molecular outflows commonly exist in high-mass star forming regions (Shepherd & Churchwell 1996; Zhang et al. 2001; Beuther et al. 2002).They provide a statistical, maybe most compelling, argument in favor of accretion based scenario for massive star formation.

However, more detailed knowledge of massive molecular outflows are limited by poor statistics of high angular resolution studies, in particular for those in ≥105 L☉ star foming regions.

Is there any systematic difference in morphology and kinematics from low-mass outflows?How do they correlate with the central driving source? How are they driven?

With the SMA, we are undertaking a systematic, high angular resolution study of molecular outflows in star forming regions of 104 to 106 L☉.

G240.31+0.07 (5×104 L☉);

NGC7538–IRS1 (105 L☉);

HH 80/81 (2×104 L☉).

A 5×104 L☉ star forming region associated with an UC HII region.Single-dish bipolar outflow ― Shepherd & Churchwell (1996); Hunter (1997); Kumar et al. (2003).

G240.31+0.07

CSO 10.4m CO J=2-1

0.1pc

G240.31+0.07

-10 km/s < V < -3 km/s6 km/s < V < 12 km/s

G240.31+0.07

G240.31+0.07

SMA + CSO

Mout ~ 91 M☉ !tdyn ~ 2.4×104 yr

~ 3.8×10-3 M☉/yr

NGC 7538 – IRS1A bipolar, expanding UC HII region, with ~105 L☉. Single-dish bipolar outflow ― Davis et al. (1998)

Davis et al. (1998)

NGC 7538 – IRS1

De Buizer & Minier 2005Gaume et al. (1995)

NGC 7538 – IRS1

Kraus et al. (2005)

HH 80/81

SMA 1.3 mm

Qiu et al. (2008)Marti et al. (1993)

HH 80/81

Remarks:

We do see collimated jet-like and wide-angle parabolic outflows,although still few, in high-mass star-forming regions; according to thestandard paradigm of low-mass star formation, they all point to diskmediated accretion.

Morphologically these outflows seem to have a common driving mechanism as low-mass outflows, but about two orders of magnitude higher mass outflow rate, and the intense UV radiation, may be challenges.

With the ALMA … (Shepherd 2008)Combining observations from the 12m array, 7m compact array, and thetotal power dishes, making high-fidelity images.