Takeshi OkaDepartment of Astronomy and Astrophysics

And Department of Chemistry

The Enrico Fermi Institute, University of Chicago

University of Illinois, Nov. 15, 2005

H3+ in the Galactic Center;

Unifying Astronomy and Chemistry

Thomas R. Geballe Gemini Observatory Miwa Goto Max-Planck-Institut für Astronomie Tomonori Usuda Subaru Telescope Benjamin J. McCall University of Illinois, Urbana-Champaign

ApJ 632, 882 (2005)

A P C B

Johannes Kepler Galileo Galilei

Isaac Newton 1666

A P C BSpectroscopy

X-ray Crystallography,……

Joseph von Fraunhofer 1787 – 1826

Approximavit Sidera

"The most remarkable discovery in all of astronomy is that the stars are made of atomsof the same kind as those on the earth." Feynman Lectures on Physics I, 3-6 (1963)

Astronomy 　　　　　 Chemistry

Nucleosynthesis

Ion chemistry H ３＋

Stars, Galaxies, Universe Atoms, Molecules, Matter

H → He → C, N, O, Ne, Mg, Si, S,…..Fe…

Stars ← Molecular Clouds

1975 H–C≡C–C≡C–C≡N H–C≡C–C≡C–C≡C–C≡N H–C≡C–C≡C–C≡C–C≡C–C≡N

C60

H3+

H 2

H 2+

C H 3+

C H 5+

C H 4

C H2 3+

C H2 2

C H3+

C H3 3+

C Hm n

C H+

C H 2+

N H2

+

H C O+

O H+

H O2+

H O3

+H O2

O H

C H C N H2 5

+

C H C N H3

+

C H N H3 2

+

H C N2

+

H C N

C H N H3 2

C H N H2

C H C N3

C H C N2 5

C H

C H C O3

+

C H O H3 2

+

C H C O2

C H O H3

H C OC H O H

C H O C H

2

2 5

3 3

C H2 5

+C H2 4

H C O2 3

+C O3

C H2

H C N3 3

+H C N3

H C N5

H C N7

H C N9

H C N11

C H3

C 4

+

C H4+

C H4 2+

C H4 3+

C H4

C H3 2

cosm ic ray

H 2N 2

C OO

H 2

H 2

e

e

e

ee

e

e

N

N H 3

H C N

C H C N3

e

C O

H O2

C H O H , e3

C

H 2

H 2

H 2

e

e

C H 3

+e

e eH C N

C+

e

C+

H 2

e eC

+

H 2H 2

e

C O

C

H

+

e

e

The first spectrum of protonated ion

Unidentified Interstellar Microwave Line

D. Buhl & L. E. Snyder, Nature 228, 267 (1970)

Carrier of the Interstellar 89.190 GHz Line W. Klemperer, Nature 227, 862 (1970)

X-gen

HCO+

Salient features of H3+

Protonated H2 (P.A.=4.4 eV), simplest polyatomic molecule

Equilateral triangle, Infrared active 4μ band

Production H2 → H2+ + e H2

+ + H2 → H3+ + H rate = ζn(H2)

Destruction Dense cloud H3+ + CO → H2 + HCO+

Diffuse cloud H3+ + e → H + H + H

Simple chemistry

10-9

10-8

10-7

10-6

10-5

10-4

10-3

10-2

10-1

100

101

102

103

104

105

106

n(X

)

10-1

100

101

102

103

104

105

106

n(H)

Dense Clouds Diffuse Clouds

H2

HCO

C+H3

+

n(H3+) constant N(H3

+) → L cloud dimension

ζ

n(H3+) ∽ ζ N(H3

+) → ζL ioniozation rate

Ubiquity Dense cloud N(H3+) = 3.6 × 1012 cm-2 AV

Diffuse cloud N(H3+) = 4.4 × 1013 cm-2 AV

The most abundant molecular ion in the Universe

Initiator of interstellar chemistry H3+ + O → OH+ + H2 OH+ → H2O+ → H3O+ → H2O

2005 Hot and Diffuse Clouds near GC Probed by Metastable H3+

Oka, Geballe, Goto, Usuda, McCall, Astro-ph/0507464

1998 – 2002 Ubiquity, Dense and Diffuse Clouds McCall, Geballe, Hinkle, Oka

Historical sketch of H3+ observation

+

1951

1970

1996

1980 Oka, PRL. 45, 531Laboratory Spectrum

1996Geballe, Oka, Nature 384, 334

Interstellar H3+, Discovery

H

H2

H3+

1989 - 95

2002 Metastable H3+, Discovery

Goto, McCall, Geballe, Usuda, Kobayashi, Terada, Oka PASJ, 54, 951

1975

6

5

4

3

2

1

0

H3+

Col

umn

Den

sity

(10

14cm

-2)

50403020100

E(B-V) (mag)

AFGL2136

W33A

MonR2 IRS 3

AFGL961E

AFGL490

AFGL2591

8

6

4

2

0

H3+

Col

umn

Den

sity

(10

14cm

-2)

6543210

E(B-V) (mag)

OphP Cygni

HD 183143

WR 118

Cyg OB2 12

WR 104

Cyg OB2 5

WR 121

HD 168607

HD 194279

GC IRS 3

2 Ori

HD 20041

Dense clouds

McCall, Geballe, HinkleOka, ApJ 522,338(1999)

Diffuse clouds

McCall, Hinkle, Geballe, Moriarty-Schieven, Evans,Kawaguchi, Takano, Smith, Oka, ApJ 567, 391 (2002)

Per

Surprise!! H3+ more abundant in diffuse clouds!!

N(H3+) ~ 3.6 ×1012 cm-2 AV

N(H3+) ~ 4.4 ×1013 cm-2 AV

Central Molecular Zone, the treasure house of H3+

M ~ 5 ×107 M⊙

Dominantly molecularDense clouds, n(H2) > 104 cm-4

Volume filling factor 0.1Hot gas T ~ 300 KHigh velocity dispersionLow dust temperature T ~ 20-30 K

Mezger, Duschl, Zylka, A&A Rev. (1996)

Morris, Serabyn, ARA&A (1996)

CMZ

Telescopes and spectrometers

UKIRT 3.8 m CGS4 8 km s-1 Mauna Kea

Subaru 　 8 m IRCS 15 km s-1 Mauna Kea

Gemini South 8 m Phoenix 5 km s-1 Cerro Pachon

Sightlines toward the CMZ

Extraordinary radio emission

• Radio Arc– Arched filaments– Nonthermal filaments

• Sgr A*Yusef-Zadeh, Morris, AJ (1987)

The central 30 pc of the CMZ

Yusef-Zadeh, Morris, AJ (1987)Nagata et al. (1990)Okuda et al. (1990)

The Quituplet

J

K32.9 K

361 K

(J, K)

The ideal energy levels of H3+

+ortho I = 3/2para I = 1/2

(3, 3) metastable level

(1, 1) ground level

Δk = ± 3 forbidden transitions

27.2 days (2, 2) unstable level

Watson, JMS (1971)

(1, 0)

Oka & Epp, ApJ 613, 349 (2004) 0 ±1 ±2 ±3 k

Ncrit ~ 200 cm-3

H3+ + H2 → (H5

+)* → H3+ + H2

Discovery of metastable H3+

Goto, McCall, Geballe, Usuda,Kobayashi, Terada, OkaPASJ, 54, 951 (2002)

(3, 3) metastable

Subaru telescope

(1, 1) ground levelCMZ and spiral arms

(3, 3) metastable level All CMZ

(2, 2) unstable level Neither

CO Mostly spiral arms

High temperature

Low density

The Expanding Molecular RingKaifu, Kato, Iguchi, Nature (1972)Scoville, ApJ (1972)

Whiteoak, Gardner, MNRAS (1979)

Dimension or the hot and diffuse clouds

ζ L = 2keN(H3+)(nC/nH)SVRX/f

= 3.7× 104 RX/f cm s-1

RX = (nC/nH)GC/(nC/nH)SV ~ 3 – 10, f ~ 1

COBE DIRBE Sodroski et al. ApJ 452, 262 (1995) Arimoto, Sofue, Tsujimoto, PASJ 48, 275 (1996)

ζ L = (1 – 4) × 105 cm s-1

If L = 20 pc, ζ = (2 – 6) × 10-15 s-1

Extremely high ionization rate

Liszt, A&A 398, 621 (2003)

Nagata, Hyland, Straw, Sato, Kawara, ApJ 406, 501 (1993)

Interstellar Space

Dense (molecular) clouds

Diffuse clouds New class of clouds?Galactic Center

Expanding molecular ring

Galactic nucleus New class of clouds?Extragalactic Object

Obscured AGN Magellanic cloudsCircumstellar Space

Planetary nebulae protoplanetary nebulaePlanet

Planets Proto-planet Exo-planet

Treasure hunting

Interstellar H3+

Cosmic Ray 　 0.6 primary particles cm-2s-1

　　　 H2 → H2+ + e- [H2] ~ 3 × 10-17

s-1

H2 H2 e

-H -H

H2+ + H2 → H + H3

+ kL [H2] [H2+]

H3+ + O → OH+ + H2 kL [H3

+] [O]

OH+ → H2O+ → H3O+ → H2O

kL~ 10-9 cm3 s-1

p

p

C.R.

Discovery of the infrared spectrum of H3+

T. Oka, Phys. Rev. Lett. 45, 531 (1980)

0

Ortho

ParaPara

H3+ emission from Jupiter

Maillard, Drossart, Watson, Kim, CaldwellApJ 262, L37 (1990)

Connerney, Satoh Phil. Trans. R. Soc. Lond. 358, 2359 (2000)