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Xu J.-L.,CAS National Astronomical Observatories | Wang J.-J.,Joint Center for Astrophysics
Research in Astronomy and Astrophysics | Year: 2010

The mapping observations of CO J 2-1, CO J 3-2, 13CO J 2-1 and 13CO J 3-2 lines in the direction of IRAS 22506+5944 have been made. The results show that the cores in the J 2-1 transition lines have a similar morphology to those in the J 3-2 transition lines. Bipolar molecular outflows are verified. The prior IRAS 22506+5944 observations indicated that two IRAS sources and three H2O masers were located close to the peak position of the core. One of the IRAS sources may be the driving source of the outflows. In addition, the H2O masers may occur in relatively warm environments. The parameters of the dense core and outflow, obtained by the LTE method, indicate that IRAS 22506+5944 is a high-mass star formation region. © 2010 National Astronomical Observatories of Chinese Academy of Sciences and IOP Publishing Ltd. Source


Yu N.-P.,CAS National Astronomical Observatories | Wang J.-J.,Joint Center for Astrophysics
Research in Astronomy and Astrophysics | Year: 2013

We present the results of a high-resolution study with the Submillimeter Array (SMA) toward the massive star-forming complex G20.08-0.14N. With the SMA data, we have detected and analyzed the transitions in the 12CO (3-2) and 12CO (2-1) molecular lines as well as CH3CN. The millimeter observations reveal highly collimated bipolar molecular outflows, traced by high-velocity 12CO (2-1) and 12CO (3-2) emissions. Using a rotation temperature diagram, we derive that the rotational temperature and the column density of CH3CN are 244 K and 1.2 × 1015 cm-2, respectively. We also suggest that the minor outflow is probably driven by the hypercompact (HC) HII region A that is inside. We find the molecular gas (traced by C17O, SO, CH3OH and SO2) surrounding G20.08-0.14N appears to be undergoing bulk rotation. The HCHII region A that is inside is most probably the main source of accretion and heating for G20.08-0.14N. © 2013 National Astronomical Observatories of Chinese Academy of Sciences and IOP Publishing Ltd. Source


Liu X.-L.,CAS National Astronomical Observatories | Liu X.-L.,University of Chinese Academy of Sciences | Wang J.-J.,CAS National Astronomical Observatories | Wang J.-J.,Joint Center for Astrophysics | And 2 more authors.
Monthly Notices of the Royal Astronomical Society | Year: 2014

The physical, chemical and kinetic characteristics of 12 northern infrared dark clouds (IRDCs) are systematic studied using the 13CO (1-0) and C18O (1-0) lines, observed with the Purple MountainObservatory 13.7mradio telescope, the 1.1mmBolocam Galactic Plane Survey data and Galactic Legacy Infrared Mid-Plane Survey Extraordinaire Spitzer Infrared Array Camera 8 μm data. The molecular lines emission and 1.1 mm continuum emission almost coincide in morphology for each IRDC and both are associated well with the IRDCs. 10 IRDCs present the filamentary structure and substructures. Totally, 41 IRDC cores are identified, and a statistic research for them shows that the northern IRDC cores have a typical excitation temperature of 8-10 K, an integrated intensity ratio of 13CO to C18O of 3-6 and the column density (1-6) × 1022 cm-2. About 57.5 per cent of the IRDC cores are gravitationally bound, which are more compact, warmer and denser. In addition, we study the mass distribution functions of the whole IRDC cores as well as the gravitationally bound cores, finding that they almost have the same power-law indices. This indicates that the evolution of the IRDC cores almost has no effect on the mass spectrum of the molecular cores and thus can be used to study the stellar initial mass function. Moreover, three IRDC cores G24.00-3, G31.38-1 and G34.43-4 are detected to have large-scaled infall motions. Two different outflows are further found for the IRDC core G34.43-4 and one of them is in high collimation. © 2014 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society. Source


Xu J.-L.,CAS National Astronomical Observatories | Xu J.-L.,University of Chinese Academy of Sciences | Xu J.-L.,Joint Center for Astrophysics | Wang J.-J.,CAS National Astronomical Observatories | Wang J.-J.,Joint Center for Astrophysics
Astronomy and Astrophysics | Year: 2012

Aims.We investigate the environment in the vicinity of the supernova remnant (SNR) G59.5+0.1 and identify all the young stellar objects (YSOs) around the SNR, to derive the physical properties, obtain insight into the star-formation history, and determine whether SNR G59.5+0.1 can trigger star formation in this region. Methods. We perform the submillimeter/millimeter observations in CO lines toward the southeast of SNR G59.5+0.1 with the KOSMA 3 m Telescope. High values of the integrated CO line-intensity ratio R ICO(3-2)/ICO(2-1) is identified as one good signature of the SNR-MC (molecular cloud) interacting system. To investigate the impact of SNR G59.5+0.1 on the process of star formation, we use GLIMPSE I catalog to select YSOs (including Class I and Class II sources). Results.The CO emission forming an arc-like shape and mid-infrared 8.28 μ m emission are coincident with SNR G59.5+0.1, which has a totalmass of 1.1×104 M· and fully covers the open cluster NGC 6823. Three molecular clumps are identified in the COmolecular arc, each clump tracing the broad-line wing emission, indicating that there are three outflows in motion. The integrated CO line intensity ratio (R ICO(3-2)/ICO(2-1) ) for the whole molecular arc is between 0.48 and 1.57. The maximum value is 1.57, which ismuch higher than previous measurements of individual Galactic MCs. The CO molecular arc has a line-intensity ratio gradient. The SNR G59.5+0.1 is in adiabatic expansion phase. The age of the SNR is 8.6 × 10 4 yr. Based on the GLIMPSE I catalog, we select 625 YSOs candidates (including 176 Class I sources and 449 Class II sources). The timescales for Class 0, Class I and Class II sources are =10 4 yr, ∼ 10 5 yr, and ∼ 10 6 yr, respectively. The number of YSOs are significantly enhanced in the interacting regions, indicating the presence of some recently formed stars. © 2012 ESO. Source


Liu X.-L.,CAS National Astronomical Observatories | Liu X.-L.,University of Chinese Academy of Sciences | Wang J.-J.,CAS National Astronomical Observatories | Wang J.-J.,Joint Center for Astrophysics | And 2 more authors.
Monthly Notices of the Royal Astronomical Society | Year: 2013

We studied 14 southern infrared dark clouds (IRDCs) using data taken from the Millimetre Astronomy Legacy Team 90 GHz (MALT90) survey and the GLIMPSE and MIPSGAL midinfrared surveys of the inner Galaxy. The physical and chemical characteristics of the 14 IRDCs were investigated using N2H+(1-0), HNC(1-0), HCO+(1-0) and HCN(1-0) molecular lines. We found that the 14 IRDCs are in different evolutionary stages, from 'starless' to sources with an ultra-compact H II region. Three IRDCs were detected to have star-forming activity. The integrated intensity ratios IHCO+/HCN, IN2H+/HCN and IHNC/HCN are all ~1.5, which is different from previous measurements, suggesting that the integrated intensity ratios may be affected by the cloud environments. The integrated intensities of HNC, HCO+ and HCN show a tight correlation for the 14 IRDCs, implying a close link to the chemical evolution of these three species in the IRDCs. The derived excitation temperature for each IRDC is less than 25 K. We estimated the abundances of the four molecules to be from 10-11 to 10-9, and the average abundance ratios are NHNC/NHCN = 1.47 ± 0.50, NHNC/NHCO+ = 1.74 ± 0.22 and NHCN/NHCO+ = 1.21 ± 0.41. © 2013 The Authors. Published by Oxford University Press on behalf of the Royal Astronomical Society. Source

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