AzTEC/ASTE Wide-Field Imaging of Southern Star Forming Regions at Lambda = 1.1 mm
Institute of Astronomy and Astrophysics, Academia Sinica
National Tsing Hua University, Hsinchu, Taiwan
I report the results of the wide-field sensitive lambda = 1.1 mm imaging observations for southern star forming regions, Chamaeleon and Lupus molecular clouds, using 144-element bolometer array AzTEC on ASTE.
With the unbiased mapping, we intended to perform wide-field survey of cores and complete survey of T Tauri stars in Chamaeleon and Lupus regions. This is the first millimeter-wave continuum wide-field mapping for these regions. Thanks to the high sensitivity of AzTEC, we have obtained ~8 deg^2 map for Cha with 12 mJy rms and ~5 deg^2 for Lup with 4 to 30 mJy rms. The detection limit is about 0.1 solar masses, and we identified about 200 sources in the two regions, including at least 6 Class 0/I candidates and ~25 T Tauri/Herbig Ae stars. Most of the starless sources detected with AzTEC are located at the densest, high Av part in the clouds, and the distribution coincides with the peaks of Spitzer 160 micron images. On the other hand, some sources have large flux in 1.1 mm but have no clear counterparts in 70 micron images. These sources would be good candidates of the starless cores just in the earliest phase of the protostar evolution.
We have constructed the core mass function (CMF) for each region, and the shape of CMF has a similarity with those of other regions such as Ophiuchus and Perseus. This resemblance indicates there is a universal mechanism in the core formation process. Some simulation studies indicate that the interstellar turbulence have an important role in cloud fragmentation, and the shape of CMF is determined by the Mach number. Considering the fact that the Mach numbers measured with C18O(1-0) line are stand at almost the same value (~3) among Cha, Oph, and Per, the resemblance of CMFs supports the turbulence-dominated cloud fragmentation model. In addition, the CMF in Cha I region well coincides with the stellar initial mass function (IMF) in this field. This consistency indicates that the CMF have a direct relationship with the IMF.
The AzTEC dataset affords us promising targets for the further researches with future instruments, such as ALMA and Herschel, on the issues of formation of cores, initial condition of star formation, and evolution process of protostars. In my presentation, I will also show the results of ASTE molecular line follow-up observations and discuss about the future prospects for the science with ALMA.