Stars are born in dense cores of molecular clouds. The core mass function(CMF), which is the mass distribution of dense cores, is important for understanding the stellar initial mass function(IMF). We obtained 350 μm dust continuum data using the SHARC-II camera at the Caltech Submillimeter Observatory(CSO) telescope. A 350 μm map covering 0.25 deg2 of the Ophiuchus molecular cloud was created by mosaicing 56 separate scans. The CSO telescope had an angular resolution of 9′′, corresponding to 1.2×103AU at the distance of the Ophiuchus molecular cloud(131 pc). The data was reduced using the Comprehensive Reduction Utility for SHARC-II(CRUSH). The flux density map was analyzed using the Gauss Clumps algorithm, within which 75 cores has been identified. We used the Spitzer c2 d catalogs to separate the cores into 63 starless cores and 12 protostellar cores. By locating Jeans instabilities, 55 prestellar cores(a subcategory of starless cores) were also identified. The excitation temperatures, which were derived from FCRAO12 CO data, help to improve the accuracy of the masses of the cores. We adopted a Monte Carlo approach to analyze the CMF with two types of functional forms; power law and log-normal. The whole and prestellar CMF are both well fitted by a log-normal distribution, with μ =-1.18±0.10, σ = 0.58±0.05 and μ = 1.40±0.10, σ = 0.50±0.05 respectively. This finding suggests that turbulence influences the evolution of the Ophiuchus molecular cloud.
We report the discovery of 64 luminous infrared galaxies, based on new observations of 20 square degrees from the LAMOST Complete Spectroscopic Survey of Pointing Area at the Southern Galactic Cap and the WISE 22 μm catalog from the AllW ISE Data Release. Half of them are classified as late-type spirals and the others are classified as peculiar/compact galaxies. The peculiar/compact galaxies tend to exhibit higher luminosities and lower stellar masses. We also separate AGNs from HII galaxies in a simple way by examining LAMOST spectra. Those cases show that host AGNs are easily distinguished from others in the mid-infrared color-color diagrams.
Man I LamHong WuMing YangYi-Nan ZhuJian-Rong ShiHao-Tong ZhangA-Li LuoShi-Yin ShenYong ZhangYong-Hui HouGuang-Wei LiYong-Heng Zhao
We present large scale observations of C18O(1–0) towards four massive star forming regions: MON R2,S156,DR17/L906 and M17/M18. The transitions of H2CO(110–111),C18O(1–0) and the 6 cm continuum are compared in these four regions. Our analysis of the observations and the results of the Non–LTE model shows that the brightness temperature of the formaldehyde absorption line is strongest in a background continuum temperature range of about 3 – 8 K. The excitation of the H2 CO absorption line is affected by strong background continuum emission. From a comparison of H2 CO and C18 O maps,we found that the extent of H2 CO absorption is broader than that of C18 O emission in the four regions. Except for the DR17 region,the maximum in H2 CO absorption is located at the same position as the C18 O peak. A good correlation between intensities and widths of H2 CO absorption and C18 O emission lines indicates that the H2 CO absorption line can trace the dense,warm regions of a molecular cloud. We find that N(H2CO) is well correlated with N(C18O) in the four regions and that the average ratio of column densities is N(H2CO)/N(C18O) ～ 0.03.
