Using CO line ratios to trace compressed areas in bubble N131

Abstract

N131 is a typical infrared dust bubble showing an expanding ringlike shell. We study what kinds of CO line ratios can be used to trace the interaction in the expanding bubble. We carry out new $\mathrm{CO}(3-2)$ observations towards bubble N131 using the JCMT 15-m telescope, and derive line ratios by combining with our previous $\mathrm{CO}(2-1)$ and $\mathrm{CO}(1-0)$ data from the IRAM 30-m telescope observations. To trace the interaction between the molecular gas and the ionized gas in the HII region, we use RADEX to model the dependence of CO line ratios on kinetic temperature and H${}_2$ volume density, and examine the abnormal line ratios based on other simulations. We present $\mathrm{CO}(3-2)$, $\mathrm{CO}(2-1)$, and $\mathrm{CO}(1-0)$ integrated intensity maps convolved to the same angular resolution (22.5$"$). The three different CO transition maps show apparently similar morphology. The line ratios of $W_{\mathrm{CO}(3-2)}$/$W_{\mathrm{CO}(2-1)}$ mostly range from 0.2 to 1.2 with a median of $0.54\pm 0.12$, while the line ratios of $W_{\mathrm{CO}(2-1)}$/$W_{\mathrm{CO}(1-0)}$ range from 0.5 to 1.6 with a median of $0.84\pm 0.15$. The high CO line ratios $W_{\mathrm{CO}(3-2)}$/$W_{\mathrm{CO}(2-1)}\gtrsim 0.8$ and $W_{\mathrm{CO}(2-1)}$/$W_{\mathrm{CO}(1-0)}\gtrsim 1.2$ are beyond the threshold predicted by numerical simulations based on the assumed density-temperature structure for the inner rims of ringlike shell, where are the compressed areas in bubble N131. These high CO integrated intensity ratios, such as $W_{\mathrm{CO}(3-2)}$/$W_{\mathrm{CO}(2-1)}\gtrsim 0.8$ and $W_{\mathrm{CO}(2-1)}$/$W_{\mathrm{CO}(1-0)}\gtrsim 1.2$, can be used as a tracer of gas compressed regions with a relatively high temperature and density. This further suggests that the non-Gaussian part of the line-ratio distribution can be used to trace the interaction between the molecular gas and the hot gas in the bubble.

6 pages, 9 figures, Accepted for publication in A&A

References in corpus (30)

• The Milky Way in Molecular Clouds: A New Complete CO Survey
• A computer program for fast non-LTE analysis of interstellar line spectra
• An atomic and molecular database for analysis of submillimetre line observations
• Far Infrared and Submillimeter Emission from Galactic and Extragalactic Photo-Dissociation Regions
• CO excitation of normal star forming galaxies out to z=1.5 as regulated by the properties of their interstellar medium
• HARP/ACSIS: A submillimetre spectral imaging system on the James Clerk Maxwell Telescope
• The Milky Way Project First Data Release: A Bubblier Galactic Disk
• IR Dust Bubbles: Probing the Detailed Structure and Young Massive Stellar Populations of Galactic HII Regions
• Cavity of Molecular Gas Associated with Supernova Remnant 3C 397
• Molecular Rings and the Thickness of Star-Forming Clouds
• How long does it take to form a molecular cloud?
• Revealing the physical properties of molecular gas in Orion with a large scale survey in J=2-1 lines of 12CO, 13CO and C18O
• CO(1-0) line imaging of massive star-forming disc galaxies at z=1.5-2.2
• The Density and Temperature of Molecular Clouds in M33
• Carbon in the N159/N160 Complex of the Large Magellanic Cloud
• Unusual CO Line Ratios and kinematics in the N83/N84 Region of the Small Magellanic Cloud
• Cold molecular gas in massive disk galaxies at z=1.5
• Expanding molecular bubble surrounding Tycho's supernova remnant (SN 1572) observed with IRAM 30 m telescope: evidence for a single-degenerate progenitor
• CO line ratios in molecular clouds: the impact of environment
• Massive molecular outflows associated with UCHII/HII regions
• The Milky Way Project Second Data Release: Bubbles and Bow Shocks
• The AMANOGAWA-2SB Galactic Plane Survey I: Data on the Galactic Equator
• The Gas Properties of the W3 GMC: A HARP study
• N131: A dust bubble born from the disruption of a gas filament
• Molecular gas toward supernova remnant Cassiopeia A
• Molecular clumps and star formation associated with the infrared dust bubble N131
• A statistical study of gaseous environment of Spitzer interstellar bubbles
• The environment of supernova remnant VRO 42.05.01 as probed with IRAM 30m molecular line observations
• High Excitation Molecular Gas in the Galactic Center Loops; 12CO(J =2-1 and J =3-2) Observations
• 12CO and 13CO J=3-2 observations toward N11 in the Large Magellanic Cloud

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