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تسجيل مستخدم جديدThe Carina Nebula and Gum 31 molecular complex: I. Molecular gas distribution, column densities and dust temperatures
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We report high resolution observations of the $^{12}$CO$(1rightarrow0)$ and $^{13}$CO$(1rightarrow0)$ molecular lines in the Carina Nebula and the Gum 31 region obtained with the 22-m Mopra telescope as part of the The Mopra Southern Galactic Plane CO Survey. We cover 8 deg$^2$ from $l = 285^{circ}$ to 290$^{circ}$, and from $b = -1.5^{circ}$ to +0.5$^{circ}$. The molecular gas column density distributions from both tracers have a similar range of values. By fitting a grey-body function to the observed infrared spectral energy distribution from Herschel maps, we derive gas column densities and dust temperatures. The gas column density has values in the range from $6.3times 10^{20}$ to $1.4times 10^{23}$ cm$^{-2}$, while the dust temperature has values in the range from 17 to 43 K. The gas column density derived from the dust emission is approximately described by a log-normal function for a limited range of column densities. A high-column density tail is clearly evident for the gas column density distribution, which appears to be a common feature in regions with active star formation. There are regional variations in the fraction of the mass recovered by the CO emission lines with respect to the total mass traced by the dust emission. These variations may be related to changes in the radiation field strength, variation of the atomic to molecular gas fraction across the observed region, differences in the CO molecule abundance with respect to H$_{2}$, and evolutionary stage differences of the molecular clouds that compose the Carina Nebula-Gum 31 complex.
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Herein, we present results from observations of the 12CO (J=1-0), 13CO (J=1-0), and 12CO (J=2-1) emission lines toward the Carina nebula complex (CNC) obtained with the Mopra and NANTEN2 telescopes. We focused on massive-star-forming regions associat
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We present the results of analyses of the 12CO (J=1-0), 13CO (J=1-0), and 12CO (J=2-1) emission data toward Gum 31. Three molecular clouds separated in velocity were detected at -25, -20, and -10 km/s . The velocity structure of the molecular clouds
in Gum 31 cannot be interpreted as expanding motion. Two of them, the -25 km/s cloud and the -20 km/s cloud, are likely associated with Gum 31, because their 12CO (J=2-1)/12CO (J=1-0) intensity ratios are high. We found that these two clouds show the observational signatures of cloud-cloud collisions (CCCs): a complementary spatial distribution and a V-shaped structure (bridge features) in the position-velocity diagram. In addition, their morphology and velocity structures are very similar to the numerical simulations conducted by the previous studies. We propose a scenario that the -25 km/s cloud and the -20 km/s cloud were collided and triggered the formation of the massive star system HD 92206 in Gum 31. This scenario can explain the offset of the stars from the center and the morphology of Gum 31 simultaneously. The timescale of the collision was estimated to be ~1 Myr by using the ratio between the path length of the collision and the assumed velocity separation. This is consistent with that of the CCCs in Carina Nebula Complex in our previous study.
We present dust column densities and dust temperatures for $sim3000$ young high-mass molecular clumps from the Millimetre Astronomy Legacy Team 90 GHz (MALT90) survey, derived from adjusting single temperature dust emission models to the far-infrared
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Gas and dust properties in the Chamaeleon molecular cloud complex have been investigated with emission lines from atomic hydrogen (HI) and 12CO molecule, dust optical depth at 353 GHz ($tau_{353}$), and $J$-band infrared extinction ($A_{J}$). We have
found a scatter correlation between the HI integrated intensity ($W_{rm HI}$) and $tau_{353}$ in the Chamaeleon region. The scattering has been examined in terms of possible large optical depth in HI emission ($tau_{rm HI}$) using a total column density ($N_{rm H}$) model based on $tau_{353}$. A nonlinear relation of $tau_{353}$ with the $sim$1.2 power of $A_{J}$ has been found in opaque regions ($A_{J}$ $gtrsim$ 0.3 mag), which may indicate dust evolution effect. If we apply this nonlinear relation to the $N_{rm H}$ model (i.e., $N_{rm H} propto tau_{353}^{1/1.2}$) allowing arbitrary $tau_{rm HI}$, the model curve reproduces well the $W_{rm HI}$-$tau_{353}$ scatter correlation, suggesting optically thick HI ($tau_{rm HI} sim$1.3) extended around the molecular clouds. Based on the correlations between the CO integrated intensity and the $N_{rm H}$ model, we have then derived the CO-to-H$_{2}$ conversion factor ($X_{rm CO}$) on $sim$1.5$^{circ}$ scales (corresponding to $sim$4 persec) and found spatial variations of $X_{rm CO}$ $sim$(0.5-3)$times$10$^{20}$ cm$^{-2}$ K$^{-1}$ km$^{-1}$ s across the cloud complex, possibly depending on the radiation field inside or surrounding the molecular clouds. These gas properties found in the Chamaeleon region are discussed through a comparison with other local molecular cloud complexes.
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