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Infall Motions of the 6.7 GHz M ethanol M as ers in the High-Mass SFR Cepheus A

Great Barriers in HMSF @ Townsville Sep, 13-17th, 2010. Yama. Uni. Infall Motions of the 6.7 GHz M ethanol M as ers in the High-Mass SFR Cepheus A. Koichiro Sugiyama (Yamaguchi University)

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Infall Motions of the 6.7 GHz M ethanol M as ers in the High-Mass SFR Cepheus A

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  1. Great Barriers in HMSF @ Townsville Sep, 13-17th, 2010 Yama. Uni. Infall Motionsofthe 6.7 GHz Methanol Masersin the High-Mass SFR Cepheus A • Koichiro Sugiyama (Yamaguchi University) • Kenta Fujisawa, Kiyoaki Wajima (Yamaguchi U.), Mareki Honma, Satoko Sawada-Satoh (NAOJ), Yasuhiro Murata, Nanako Mochizuki, Akihiro Doi (ISAS/JAXA)

  2. Introduction maser CH3CN 22 GHz 8 GHz • How form high-mass stars ?? • Merging among multi low-mass stars • Accretion from the gas disk around YSO • accre. rate 10-3M◎ yr-1 • Molecular line obs. • perpendicular to jets or outflows • radial velocity gradient Cep A Possibility of association with the rotating disk Patel et al. (2005) Directly measure rotating and infall motions ! • Methanol maser at 6.7 GHz in Cep A • Arched structure • Perpendicular to the radio jet • PA difference : ~70 deg • CH3CN disk coincidence • size & velocity range 22 GHz jet Sugiyama et al. (2008)

  3. Cep A methanol maser with infall ?? R : 955 mas i : 73 deg PA : 110 deg Vsys : -3.91 ±0.07 Vrot : 0.46 ±0.12 Vinf : 0.43 ±0.03 • Rotation and expansion model（Uscanga+ 2008, Torstensson+ 2008, Bartkiewicz+ 2009） better fit than rotation only : rotation + infall !! Verify rotation + infall by measuring internal proper motions !

  4. Japanese VLBI Network (JVN) • 13 antennas • 3-band frequencies • 6.7, 8.4, 22.2 GHz • Baseline : 50-2500 km • e-VLBI possible • at 6.7 GHz • antenna : 6 stations • max. resolution : ~4 mas • For Cep A obs. • vel. resolution : 0.176 km s-1 • synthesized beam : ~ 9×4 mas2 (~ 6×3 AU @ 0.7 kpc) • 2006/9/9, 2007/7/28, 2008/10/25 JVN-HP http://www.astro.sci.yamaguchi-u.ac.jp/~kenta/jvnhp/index.html

  5. Internal proper motions of methanol masers • Identification • within vel. resolution • moving > 3s • Rotation ?? • Move along the ellipse • Some random motion… • At least perpendicular to the jet direction 42 spots (all epochs : 24) • vx : ‐7.8 ~ 7.0 km s-1 • vy : ‐6.0 ~ 6.3 km s-1

  6. Rotation & expansion model face-on • Simple model • concentrically • move on the disk plane x vrot q vexp y Vexp = ‐2.5 ± 1.1 km s-1 ( negative exp. => infall ) Vrot = 1.0 ± 1.0 km s-1 i y Vsys= ‐4.8 ± 0.8 km s-1

  7. Summary and Remarks • 6.7 GHz methanol maser in Cep A • Coincidence with the molecular rotating disks • Infall proper motions with the JVN => Fit to 3-D motions => rotation & infall !! But… • Some problems • Central mass ~ 2 M◎ : not high mass (> 8 M◎) … • Radiative pressure > infall momentum rate (nH2=106 cm-3) … • accurate luminosity at methanol infall position • high-resolution molecular line obs.

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