A multi-wavelength analysis of the large Galactic infrared bubble N 24 is has been presented in this paper in order to investigate the molecular and star formation environment around expanding H ii regions. Using archival data from Herschel and ATLASGAL, the distribution and physical properties of the dust over the entire bubble are studied. Twenty three dense clumps are identified using the Clumpfind2d algorithm with sizes and masses in the range 0.65-1.73 pc and 600-16300 M , respectively. To analyse the molecular environment in N 24, observations of NH 3 (1,1) and (2,2) were carried out using the Nanshan 26-m radio telescope. Analysis of the kinetic temperature and gravitational stability of these clumps suggests gravitational collapse in several of them. The mass-size distributions of the clumps and the presence of massive young protostars indicate that the shell of N 24 is a region of ongoing massive star formation. The compatibility of the dynamical and fragmentation time-scales and the overabundance of YSOs and clumps on the rim suggest that the "collect and collapse" mechanism is in play at the boundary of the bubble, but the existence of the IRDC at the edge of bubble indicates that "radiation-driven implosion" mechanism may also have played a role there.
We performed a detailed study of the highmass clump interacting with bubble N10 based on the spectral lines 12 CO(3 − 2), HCO + (4 − 3), N 2 H + (4 − 3) and CH 3 OH(7(0, 7) − 6(0, 6)) and continuum emission data at 450 µm and 850 µm released on CADC and Spitzer data. Blue-shifted optically thick line 12 CO(3− 2) seems to indicate that the outer envelope of the highmass clump is still falling toward the center. Detection of CH 3 OH(7(0, 7) − 6(0, 6)) suggests that a hot core has formed around YSO N10-7. And position-velocity diagram of N 2 H + (4−3) indicates the cold dense core of the clump has not been destroyed by the star formation activities. The mass of N10-7 is about 27.44 M ⊙ . The ratio HCO + (4 − 3)/N 2 H + (4 − 3) in the outer part of the clump is larger than that in the inner part of it. The reason may be that the CO abundance relative to N 2 H + (4 − 3) increased in the outer part of the highmass clump, more N 2 H + (4 − 3) were converted into HCO + (4 − 3).
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