H 3 A new probe of the Galactic

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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+ T. Oka, T. R. Geballe, M. Goto, T. Usuda, B. J. Mc. Call, Ap. J 632, 882 (2005) ACS symposium “Molecules in Space”, Atlanta, March 30, 2006

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

H 3 + toward the Galactic center R(1, 1)u R(1, 0) Geballe, Mc. Call, Hinkle, Oka, Ap. J 510, 251 (1999)

The ubiquitous H 3+ Dense clouds Mc. Call, Geballe, Hinkle Oka, Ap. J 522, 338(1999) N(H 3+) ~ 3. 6 × 1012 cm-2 AV N(H 3+) ~ 4. 4 × 1013 cm-2 AV Diffuse clouds Per Mc. Call, Hinkle, Geballe, Moriarty-Schieven, Evans, Kawaguchi, Takano, Smith, Oka, Ap. J 567, 391 (2002)

X(H 3+)diffuse ~ 10 X(H 3+)dense H 3+ is a powerful probe for diffuse clouds N(H ) 2 n L AV N(H 3+) X(H 3+) ζ V (H 3+)total 100 1 1 1 1 10 10 100 Dense S Diffuse 1 100

Sightlines toward the Galactic center AV = 25 ~ 40 Cotera, Simpson, Erickson, Colgan, Burton, Allen, Ap. JS 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, Ap. J 490, 729 (1997) Mezger, Duschl, Zylka (1996) Georgelin, Georgelin (1976) N(H 3+)DISM: N(H 3+)MC ~ 20 : 1

The Central Molecular Zone (CMZ) R ~ 200 pc M ~ 5 × 107 M⊙ Dominantly molecular n(H 2) > 104 cm-3 Volume filling factor 0. 1 10 % of total ISM Hot gas High velocity dispersion Low dust temperature OH, H 2 CO, CS, NH 3, HCN H 3+ Morris, Serabyn, ARA&A (1996) Genzel, Hollenbach, Townes (1994) CMZ Mezger, Duschl, Zylka, A&A Rev. (1996)

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

H 3+ in the (3, 3) metastable level The Subaru Telescope Goto, Mc. Call, Geballe, Usuda, Kobayashi, Terada, Oka PASJ, 54, 951 (2002) J 361 K 32. 9 K V = 2← 0 K

Sightline toward the Galactic center The Central Molecular Zone

The ideal energy levels of H 3+ + H 2 → (H 5+)* → H 3+ + H 2 Δk = ± 3 forbidden transitions (J, K) Oka, Shimizu 2, Watson, Ap. J (1971) J Ncrit ~ 200 cm-3 (3, 3) metastable level 361 K 27. 2 days (1, 0) (2, 2) unstable level (1, 1) ground level K 0 ± 1 ± 2 ± 3 Pan, Oka, Ap. J 305, 518 (1986) k Oka, Epp, Ap. J 613, 349 (2004)

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

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

Dimension of the -100 km/s cloud 7. 3 × 10 -8 cm 3/s 1. 6 × 10 -4 1 ζL = 2 ke N(H 3+) (n. C/n. H)SV RX / f 1. 6 × 1015 cm-2 3 - 10 Sodroski et al Ap. J 452, 262 (1995) ζL = (1. 1 – 3. 7) × 105 cm/s ζ (s-1) 3× 10 -17 3× 10 -16 3× 10 -15 L (pc) (1. 2 – 4. 0) k 120 – 400 12 – 40

Other stars in the quintuplet cluster

Other stars within 30 pc Nagata, Hyland, Straw, Sato, Kawara, Ap. J 1993 Oka, Geballe, Goto, Usuda, Mc. Call, Ap. J (2005)

A comparison A

Main Results so far • • Vast amount of diffuse gas High temperature: T ~ 250 K Low Density: n ~ 100 cm-3 H 3+ total column density: 4. 3 1015 cm-2 ¾ in CMZ, ¼ in intervening spiral arms ½ of H 3+ in CMZ in the Expanding Mol. Ring Pathlength ~ 100 pc Ionization rate ~ 10 -15 s-1 Volume filling factor of dense clouds 0. 01

The Galactic center The Central Molecular Zone (CMZ) The treasure house of H 3+ Discovery of metastable H 3+ Revelation of warm and diffuse gas CO, CS H 3+ Radio scattering X-ray Cold Warm Hot Ultrahot 30 K 250 K 104 K 107 -8 K >104 cm-3 ~102 cm-3 ~0. 3 cm-3 0. 1 0. 01 0. 5 - 1 ~ 0. 5 Volume filling factor f « 1

Extragalactic H 3+ Z = 0. 05821 Geballe, Goto, Usuda, Oka, Mc. Call Ap. J in press

Controversies T. Oka No hot gas in the Expanding Molecular Ring F. Le Petit J. Black Diffuse gas cannot be that hot Infrared pumping Linnott & Rawlings (2, 0) Dynamically evolving cloud A&A 448, 425 (2006) F. Yusef-Zadeh 4 categories of gases Ap. J 637, L 101 (2006) (3, 0) (1, 0) (3, 3)

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

望遠鏡と分光器 UKIRT 3. 8 m すばる　 8 m Gemini South 8 m CGS 4 8 km s-1 Mauna Kea IRCS 15 km s-1 Mauna Kea Phoenix 5 km s-1 Cerro Pachon

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