Astronomy and Astrophysics – Astronomy
Scientific paper
Apr 2007
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2007acasn..48..139l&link_type=abstract
Acta Astronomica Sinica, vol. 48, no. 2, p. 139-152
Astronomy and Astrophysics
Astronomy
Stars: Formation, Ism:Lines And Bands, Ism: Abundances
Scientific paper
The data of (J=1-0) lines of 12CO, 13CO and C18O were taken simultaneously by using 13.7m millimeter telescope of Qinghai station of Purple Mountain Observatory at Delingha. The mapped 11 isolated star-forming molecular cores were selected from Spitzer's c2d Legacy program. The maps for one source cover the same range, at the boundary the intensity of 13CO (J=1-0) equals its half peak value. The optical depth, excitation temperature and column density are calculated. The volume density, local thermodynamic equilibrium (LTE)-mass (M LTE) and Virial-mass (M VIR) are derived for each core. The ratio of MVIR to M LTE is 0.84±0.38 for 13CO (J=1-0) and 0.76±0.32 for C18O (J=1-0). In the most of the cores, the intensities of 13CO (J=1-0) lines are equal to or even lower than that of C18O (J=1-0) lines because of the self-absorption of 13CO (J=1-0) lines. The asymmetrical spectra of L723, L778, L1152, L1082A and L1165 show that the cores are collapsing and are in the very early stage of star formation. We estimate the density profiles for most of the cores except CB224 and CB230 for unavailable C18O (J=1-0) data. The density profile is about r -1.3 with the index of 1.3, which is smaller than 2 for the theoretical value. The correlation between the luminosity values and the masses of the cores shows that these cores are at a similar stage of star formation. The ratio of LIR/MLTE is 0.04 for 13CO (J=1-0), and 0.12 for C18O (J=1-0), while it is typically 4 for massive star forming region. This is probably because that 13CO (J=1-0) and C18O (J=1-0) are not ideal dense molecular tracers, and the cores defined by them are larger than the real star forming regions.
Li Baowen
Ma J.-H.
Pei Chang-xing
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