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H 3 + : A new probe of the Galactic center

H 3 + : A new probe of the Galactic center. Takeshi Oka. Department of Astronomy and Astrophysics and Department of Chemistry, The Enrico Fermi Institute, The University of Chicago. Hot and diffuse clouds near the Galactic center probed by metastable H 3 +

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H 3 + : A new probe of the Galactic center

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  1. H3+: A new probe of the Galactic center Takeshi Oka Department of Astronomy and Astrophysics and Department of Chemistry, The Enrico Fermi Institute, The University of Chicago Hot and diffuse clouds near the Galactic center probed by metastable H3+ T. Oka, T. R. Geballe, M. Goto, T. Usuda, B. J. McCall, ApJ 632, 882 (2005) ACS symposium “Molecules in Space”, Atlanta, March 30, 2006

  2. 4  1014 cm-2 6  1014cm-2 Nature 384, 334 (1996)

  3. H3+ toward the Galactic center R(1, 1)u R(1, 0) Geballe, McCall, Hinkle, Oka, ApJ 510, 251 (1999)

  4. The ubiquitous H3+ Dense clouds McCall, Geballe, Hinkle Oka, ApJ 522,338(1999) N(H3+) ~ 3.6 ×1012 cm-2 AV N(H3+) ~ 4.4 ×1013 cm-2 AV Diffuse clouds McCall, Hinkle, Geballe, Moriarty-Schieven, Evans, Kawaguchi, Takano, Smith, Oka, ApJ 567, 391 (2002)  Per

  5. X(H3+)diffuse ~ 10 X(H3+)dense H3+is a powerful probe for diffuse clouds N(H2) n 100 1 L 1 10 AV 10 1 N(H3+) 1 1 ζ 1 10 V 1 1000 (H3+)total 1 100 X(H3+) 1 10 Dense S 1 100 Diffuse

  6. Sightlines toward the Galactic center AV = 25 ~ 40 Cotera, Simpson, Erickson, Colgan, Burton, Allen, ApJS 192, 123 (2000) Toward Sgr A* AV ~ 30 [AV]DISM ~ 20 , [AV]MC ~ 10 Whittet, Boogert, Gerakines,Schutte, Tielens, de Graauw, Prusti, van Dishoeck, Wesselius, Wright, ApJ 490, 729 (1997) N(H3+)DISM: N(H3+)MC ~ 20 : 1 Mezger, Duschl, Zylka (1996) Georgelin, Georgelin (1976)

  7. The Central Molecular Zone(CMZ) R ~ 200 pc M ~ 5 ×107 M⊙ Dominantly molecular n(H2) > 104 cm-3 Volume filling factor 0.1 10 % of total ISM Hot gas High velocity dispersion Low dust temperature H3+ OH, H2CO, CO, CS, NH3, HCN Morris, Serabyn, ARA&A (1996) Genzel, Hollenbach, Townes (1994) CMZ Mezger, Duschl, Zylka, A&A Rev. (1996)

  8. Extraordinary radio emission The Quituplet Nagata et al. (1990) Okuda et al. (1990) Yusef-Zadeh, Morris, AJ (1987) LaRosa, Kassim, Lazio, Hyman, AJ 119, 207 (2000)

  9. H3+in the(3, 3) metastable level The Subaru Telescope Goto, McCall, Geballe, Usuda, Kobayashi, Terada, Oka PASJ, 54, 951 (2002) J 361 K 32.9 K V = 2← 0 K

  10. Sightline toward the Galactic center The Central Molecular Zone

  11. The ideal energy levels ofH3+ H3+ + H2→ (H5+)* → H3+ + H2 Δk = ± 3 forbidden transitions (J, K) Oka,Shimizu2, Watson, ApJ (1971) J Ncrit ~ 200 cm-3 (3, 3) metastable level 361 K (2, 2) unstable level 27.2 days (1, 0) (1, 1) ground level K Pan, Oka, ApJ 305, 518 (1986) Oka, Epp, ApJ 613, 349 (2004) 0 ±1 ±2 ±3 k

  12. Enter the Gemini South Observatory (1, 1) ground level CMZ and spiral arms (3, 3) metastable level All CMZ High temperature (2, 2) unstable level Neither Low density CO Mostly spiral arms

  13. The Expanding Molecular Ring Kaifu, Kato, Iguchi, Nature (1972) Scoville, ApJ (1972) Whiteoak, Gardner, MNRAS (1979)

  14. Dimension of the -100 km/s cloud 7.3 ×10-8 cm3/s 1.6 ×10-4 1 ζL = 2 ke N(H3+) (nC/nH)SV RX / f 1.6 ×1015 cm-2 3 - 10 Sodroski et al ApJ 452, 262 (1995) ζL = (1.1 – 3.7) ×105 cm/s ζ (s-1) L (pc) 3×10-17 (1.2 – 4.0) k 3×10-16 120 – 400 3×10-15 12 – 40

  15. Other stars in the quintuplet cluster

  16. Other stars within 30 pc Nagata, Hyland, Straw, Sato, Kawara, ApJ 1993 Oka, Geballe, Goto, Usuda, McCall, ApJ (2005)

  17. A comparison A

  18. Main Results so far • Vast amount of diffuse gas • High temperature: T ~ 250 K • Low Density: n ~ 100 cm-3 • H3+ total column density: 4.3  1015 cm-2 • ¾ in CMZ, ¼ in intervening spiral arms • ½ of H3+ in CMZ in the Expanding Mol. Ring • Pathlength ~ 100 pc • Ionization rate ~ 10-15 s-1 Volume filling factor of dense clouds 0.01

  19. The Galactic center The Central Molecular Zone (CMZ) The treasure house of H3+ Discovery of metastable H3+ Revelation ofwarm and diffuse gas H3+ CO, CS Radio scattering X-ray Cold 30 K >104 cm-3 Warm 250 K ~102 cm-3 Hot 104 K ~102 cm-3 Ultrahot 107-8 K ~0.3 cm-3 0.1 0.5 - 1 ~ 0.5 «1 0.01 Volume filling factor f

  20. Extragalactic H3+ Z = 0.05821 Geballe, Goto, Usuda, Oka, McCall ApJ in press

  21. Controversies No hot gas in the Expanding Molecular Ring T. Oka F. Le Petit Diffuse gas cannot be that hot J. Black Infrared pumping (2, 0) Linnott & Rawlings Dynamically evolving cloud A&A 448, 425 (2006) F. Yusef-Zadeh 4 categories of gases ApJ 637, L101 (2006) (3, 3) (3, 0) (1, 0)

  22. Dahmen, Hüttemeister, Wilson, Mauersberger, A&A, 331, 959 (1998)

  23. 望遠鏡と分光器 UKIRT 3.8 m CGS4 8 km s-1 Mauna Kea すばる　 8 m IRCS 15 km s-1 Mauna Kea Gemini South 8 m Phoenix 5 km s-1 Cerro Pachon

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