1. H 3 +, the new probe for ionization rate  Takeshi Oka Department of Astronomy and Astrophysics and Department of Chemistry The Enrico Fermi Institute, University of Chicago Cosmic Ray Interactions: Bridging High and Low Energy Astrophysics Leiden, March 14, 2011 Tom Geballe Gemini Observatory Nick Indriolo, Ben McCall University of Illinois, Urbana-Champaign the cosmic ray 7

2. Astronomers’ Periodic Table Ben McCall H He CN O Ne SiS Ar Mg Fe 6

3. Hydrogenic Probes H2+H2+ HH HH2H2 H+H+ H3+H3+ HH2H2 + H3+H3+ Ewen & Purcell 1951 Muller & Oort 1951 Carruthers 1970 Spitzer et al. 1973 Geballe & Oka 1996 ~ 10 -7  10 -8 5

4. H 3 + the most direct probe for soft cosmic ray 4

5. Simple chemistry: production H 2 → H 2 + + e  = 10 -18 ~ 10 -14 s -1 dn(H 3 + )/dt = dn(H 2 + )/dt =  n(H 2 ) H2+H2+ HH2H2 H+H+ H3+H3+ H 2 + + H 2 → H + H 3 + R = k L n(H 2 ) 10 -9 cm 3 s -1 10 4 - 10 2 cm -3 1.7 eV P. Langevin 1905  r -4 OH, HD 3

6. H 3 + the most direct probe for soft cosmic ray Simple chemistry: destruction Dense Clouds (~10 4 cm -3 ) C  CO H 3 + + CO → H 2 + HCO +  dn(H 3 + )/dt = k L n(H 3 + )n(CO) Diffuse Clouds (~10 2 cm -3 ) C  C + + e  H 3 + + e  → 3H, H 2 + H  dn(H 3 + )/dt = k e n(H 3 + )n(e  ) n ( H 3 + ) = = 10 -9 cm 3 s -1  r -4 10 -7 cm 3 s -1  r -1 Steady state =  n(H 2 ) (n H /n C )f(H 2 )/2 N(H 3 + )/L f(H 2 ) = 2n(H 2 )/n H 2

7. H 3 + the most direct probe for soft cosmic ray  L  N(H 3 + )  L = 2 k e N(H 3 + ) (n C /n H ) SV R C/H / f(H 2 )  L = 2 k e N(H 3 + ) (n C /n H ) / f(H 2 )  L = 2 k L N(H 3 + ) (n C /n H )  1.5 Dense clouds Diffuse clouds Galactic center  L = (0.6 – 2.3)  10 2 cm s -1 N(H 3 + ) obs = (1.1 – 5.2)  10 14 cm -2 N(H 3 + ) obs = (0.21 – 2.4)  10 14 cm -2 N(H 3 + ) obs = (1.8 – 6.1)  10 15 cm -2  L = (0.4 – 4.4)  10 4 cm s -1  L > (1.2 – 4.2)  10 5 cm s -1 Goto, Usuda, Nagata, Geballe, McCall, Indriolo, Suto, Henning, Morong, Oka, 2008, ApJ, 688, 306 Indriolo, Geballe, Oka, McCall, 2007, ApJ, 671,1736 1  = 3  10 -17 s -1 L = (0.6 – 2.3) pc  = 1.5  10 -15 s -1 L > (24 – 84) pc  = 4.5  10 -16 s -1 L = (3 – 29) pc R C/H 3 – 6.7 McCall, Geballe, Hinkle, Oka, 1999, ApJ, 522, 338 Rolleston et al. 2000, A&A, 363, 557 Esteban et al. 2005, ApJ, 618, L95 R X 3 – 10, > 3 Sodroski, et al. 1995, ApJ 452, 262 Arima, Sofue, Tsujimoto, 1996, PASJ 48, 275

8. Telescopes and spectrometers Telescope D Spectrom. λ/Δλ UKIRT 3.8 m CGS4 40,000 Mauna Kea 1982 Subaru 8.2 m IRCS 20,000 Mauna Kea 2000 Gemini South 8 m Phoenix 60,000 Cerro Pachon 2003 VLT 8.2 m CRIRES 100,000 Cerro Paranal 2006 Gemini North 8 m GENIRS 18,000 Mauna Kea 2011 Subaru UKIRT Gemini South VLT Gemini North

9. Remarkable similarity between velocity profiles of H 3 + toward Iota and H 2 O +, CH + toward Sgr B2 Herschel observations of ortho- and para- oxidaniumyl (H 2 O + ) in spiral arm clouds toward Sgr B 2 (M) ⋆ P. Schilke,1,2 C. Comito,2 H. S. P. M¨uller,1 E. A. Bergin,3 E. Herbst,14 D. C. Lis,4 D. A. Neufeld,20 T. G. Phillips,4 T. A. Bell,4 G.A. Blake5 E. Caux,6,7 C. Ceccarelli,8 J. Cernicharo,9 N. R. Crockett,3 F. Daniel,9,10 M.-L. Dubernet,11,12 M. Emprechtinger,4 P. Encrenaz,10 M. Gerin,10 T. F. Giesen,1 J. R. Goicoechea,9 P. F. Goldsmith,13 H. Gupta,13 C. Joblin,6,7 D. Johnstone,15 W. D. Langer13 W. B. Latter16 S. D. Lord,16 S. Maret,8 P. G. Martin,17 G. J. Melnick,18 K. M. Menten,2 P. Morris,16 J. A. Murphy,19 V. Ossenkopf,12,21 J. C. Pearson,13 M. P´erault,10 R. Plume,22 S.-L. Qin,13 S. Schlemmer,1 J. Stutzki,1 N. Trappe,19 F. F. S. van der Tak,21 C. Vastel,6,7 S. Wang,3 H. W. Yorke,13 S. Yu,13 N. Erickson,25 F.W. Maiwald,13 J. Kooi,4 A. Karpov,4 J. Zmuidzinas,4 A. Boogert,4 R. Schieder,1 and P. Zaal21 A&A June 22 2010 Geballe & Oka, 2010, ApJ, 709, L70 H 3 + R(1,1) l H 2 O + 1 11 ← 0 00 H 2 O + 1 10 ← 1 01 17 pc 3 kpcScutum Sgittarius E. Falgarone et al. 2010 0