1 / 12

Takashi Hosokawa ( NAOJ )

Dynamical Triggering of Molecular Cloud Formation around Expanding HII Region and PDR. Takashi Hosokawa ( NAOJ ). Shu-ichiro Inutsuka (Kyoto). Hosokawa & Inutsuka, astro-ph/0605648. also see, Hosokawa & Inutsuka, 2005, ApJ, 623, 917 2006, ApJ, 646, 240

stuart
Download Presentation

Takashi Hosokawa ( NAOJ )

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Dynamical Triggering of Molecular Cloud Formation around Expanding HII Region and PDR Takashi Hosokawa ( NAOJ ) Shu-ichiro Inutsuka (Kyoto) Hosokawa & Inutsuka, astro-ph/0605648 also see, Hosokawa & Inutsuka, 2005, ApJ, 623, 917 2006, ApJ, 646, 240 2006, ApJ, 648L,131 Hosokawa, 2006, A&A, in press 2006.11.2 EANAM06 @ Daejeon, Korea

  2. CO Radiative Feedback for Molecular Cloud • Ionizing photons ( ) • Dissociating photons • ( ) Negative Feedback destroy molecular cloud and suppress star formation ( H2 → HI →HII ) NGC3603 by HST (e.g., Whitworth 1979 ) V.S Positive Feedback shock front sweeps up H2 gas to trigger star formation ( compression of H2 ) (e.g., Elmegreen & Lada 1977) Sh104 ; Deharveng et al. (2003)

  3. Radiative Feedback for diffuse ISM W5 Negative Feedback Photoionization of the neutral medium : promising process to supply the diffuse warm ionized medium. ( HI →HII ) (e.g., Miller & Cox 1993 ) Wisconsin H-alpha Mapper (WHAM) ; Haffner et al. (2003) V.S Positive Feedback Shock front sweeps up the ambient neutral medium. Reformation of molecules is triggered in the compressed layer. CO HII ( HI →H2 ) (e.g., Koyama & Inutsuka 2000 ) 33pc Karr & Martin (2003)

  4. Motivation THIS TALK Hosokawa & Inutsuka, 2005, ApJ, 623, 917 2006, ApJ, 646, 246 etc. HI HI H2 (2) Expanding HII regions trigger the star formation and/or destroy the molecular cloud (3) HII region expands in the diffuse neutral medium (1) HII regions expand in the molecular clouds In phases ( 3 ) , what is the role of HII regions expanding in the neutral medium? 1.photoionization (HI→HII)2. reformation of molecules (HI→H2) Which is more efficient? Does the molecular formation occur?

  5. Basic Equations 1D Radiation-Hydrodynamics Calculation hydrodynamics : 2nd-order Godunov method continuity： momentum eq. ： 17 processes energy eq. ： equation of state ： Radiative transfer ： UV photon ( ) FUV photon ( ) freq. Dependent chemistry： H+/H, O+/O, H/H2, C+/CO (Nelson & Langer 1998) (Photoinization) (photodissociation)

  6. Situation Shell Shock front Cold Neutral Medium ( n~10/cc, T~100K ) Ionization front • Study the physical/chemical structure of the shell • Does molecular gas form from ambient neutral medium?

  7. Dynamical Evolution Central star：41Msun , ambient medium：CNM (n=10/cc) ( equilibrium state with typical FUV field ) Snapshots Temperature Density 5Myr 3Myr t=1Myr 7Myr 9Myr Initial T Dense and cold shell is formed around the HII region density : n~1000/cc, temperature: T~30 K

  8. Accumulation of Molecules nH2/nH nCO/nHZC M-S life time Shock front Ionization Front H2 are formed in the shell, but CO are hardly formed : Dark H2 Intermediate gas phase between neutral medium and molecular clouds

  9. Hunt of Predicted Gas Phase Hunt the cold (T~a few ×10 K) HI HI 21cm line emission HI Self-Absorption (HISA)： absorption of colder HI against the emission by the warmer HI (Tb ~100 K) Canadian Galactic Plane Survey CGPS ; Taylor et al. (2003) • galactic plane survey @ radio, IR • angular resolution : about 1‘ • distribution of HI, HII, CO, dust Channel Map Blue image:21cm emission, Red contour:CO

  10. CGPS data in W5 HII region 21cm continuum (HII gas) Tb=5K (bright) → 12.5K (dark) Image : 60μm dust emission Contour : 12CO(1-0) @ vLSR=-39.8 km/s • Ionized gas is surrounded with the dust shell. • Distribution of CO molecules show poor correlation with • the dust shell.

  11. CGPS data in W5 HII region HI 21cm emission @ vLSR=-39.8 km/s : Tb=45K (bright) → 110K (dark) contour : 60μm dust emission • Shell-like HISA feature is found around W5 HII region. • HISA feature overlaps with the dust shell.

  12. Summary We have studied the role of the HII region expanding in the diffuse neutral medium. • Numerical Calculation (in CNM) • Cold (T~30K) and dense (n~1000/cc) shell is formed around HII region. • H2 is formed in the shell, but CO is hardly formed. • intermediate gas phase between the diffuse neutral medium and • molecular clouds • Analysis with CGPS data ( in W5 HII region ) • Shell-like HISA feature is found around ionized gas. • The dust shell shows goodcorrelation with the shell-like HISA. • Distribution of CO molecules showpoor correlation with both • dust shell and HISA.

More Related