H3+

H3+, a new astrophysical probe:

Revelation of warm and diffuse gas near the Galactic center

Takeshi OkaDepartment of Astronomy and Astrophysics and

Department of Chemistry, The Enrico Fermi InstituteThe University of Chicago

Thomas R. Geballe Gemini Observatory

Miwa Goto Max Planck Institute for Astronomy

Tomonori Usuda Subaru Telescope

Benjamin J. McCall University of Illinois, Urbana-Champaign

Tetsuya Nagata Kyoto UniversityTomoharu Oka University of TokyoFarhad Yusef-Zadeh Northwestern UniversityHarvey Liszt National Radio Astronomy Observatory

June 27, 2007 CSO

Thumbnail sketch of H3+

+

1951

1970

1996

H

H2

H3+

Simplest polyatomic molecule

CO

Simple chemistry H2 → H2+ + e H2

+ + H2 → H + H3+

c.r.

p

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

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

p

Powerful informant of:

Cosmic ray ionization rate ζ Temperature T density n

Radial length of clouds L

X(H3+)diffuse ~ 10X(H3

+)dense

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

+

ζL = 2 ke N(H3+) (nC/nH)

2005 Hot and Diffuse Clouds near GC Probed by Metastable H3

+

Oka, Geballe, Goto, Usuda, McCall, ApJ 632, 882

Progress of H3+ observation

1980 Oka, PRL. 45, 531Laboratory Spectrum

1996 Geballe, Oka, Nature 384, 334Interstellar H3+, Discovery

1989 - 95

2002 Metastable H3+, Discovery Goto, McCall, Geballe, Usuda,

Kobayashi, Terada, Oka PASJ, 54, 951

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

ζdiffuse ~ !0 ζdense

1975

Inferred face-on view of the Central Molecular Zone

Sawada, Hasegawa, Handa, Cohen, MNRAS 349, 1167 (2004)Oka, Hasegawa, Sato, Tsuboi, Miyazaki, ApJS 118, 455 (1998)

130 pc

100 km s-1

Quintuplet

GCS3-2

130 pc

100 km s-1

Telescope and spectrometer

UKIRT 3.8 m CGS4 8 km s-1 Mauna Kea 1982 Subaru 　 8.2 m IRCS 15 km s-1 Mauna Kea 2000Gemini South 8 m Phoenix 5 km s-1 Cerro Pachon 2003VLT 8.2 m CRIRES ≤3 km s-1 Cerro Paranal 2006

Breaking

Symmetry

Interstellar NH3 Oka, Shimizu, Shimizu, Watson, ApJ 165, L15 (1971)

Interstellar H3+ Pan, Oka, ApJ 305, 518 (1986)

Oka, Epp, ApJ 613, 349 (2004)

Metastable

27.2 days

20.4 days

μ

Critical Density 200 cm-3

Ortho I = 3/2

Para I = 1/2J

KCollision H3

+ + H2 → (H5+)* → H3

+ + H2

16 hrs8 hrs

The ideal rotational levels of H3+

(3,3)

(2,2)Unstable

(1,1)Ground

361 K

Central Molecular Zone is the Treasure House

of H3+

R(1, 1)u R(1, 0)

Geballe Phil. Trans. RSL A358, 2503 (2000)

N(H3+) = 3.8 × 1014 cm-2

L = 21 pc

N(H3+) = 4.4 × 1015 cm-2

CO J = 1

(2,2) unstable

(3,3) metastable

(1,1) ground

Spectroscopy

Oka, Geballe, Goto, Usuda, McCall, ApJ 632, 882 (2005)

130 pc

100 km s-1

T = 250 K

n ≤ 100 cm-3

Dimension of the discovered gas

ζL = 2 ke N(H3+) (nC/nH)SV RX

7.3 ×10-8 cm3/s 1.6 ×10-4

3.1 ×1015 cm-2 3 - 10

Sodroski et al ApJ 452, 262 (1995)

ζL = (2.5 – 8.4) ×105 cm/s

ζ (s-1) L (pc)

10-16 (0.8 - 2.1) k 10-15 80 - 210

COBE DIRBE

130 pc

100 km s-1

Oka, Geballe, Goto, Usuda, McCall, ApJ 632, 882 (2005)

(2,2) densitometer

(3,3) thermometer

(1,1) ground level

(2,2) densitometer

(3,3) thermometer

(1,1) ground level

8 stars within 30 pc from GC

T = 220 - 400 Kn ≤ 100 cm-3

All show high T and low n

All stars: high N(H3+) and hence high ζL

N(H3+) = (2.3 - 4.5) × 1015 cm-2

R(2, 2)l

R(1, 1)l

Q(1, 0)Q(1, 1)R(3, 3)l

R(1, 0)+R(1, 1)u

R(2, 2)l

R(1, 1)l

Q(1, 0)Q(1, 1)R(3, 3)l

R(1, 0)+R(1, 1)u

L ≥ 60 – 120 pc for RX = 3 and ζ = 10-15 s-1

Lazio & Cordes, ApJ 505, 715 (1998)

0.8 107 K

0.1 106 K 10 cm-3

0.1 102 K 104 cm-3

Enter a new category of gas in the CMZ

Warm and diffuse gas250 K 102 cm-3

??

that is incompatible with two other gases

Chandra 20 pc × 20 pc (0.5 – 8) keV Muno et al. ApJ 589, 225 (2003)

Warwick, Sakano Decourchelle (2006) Revnivtsev et al. (2006)

X-ray: Chandra comes to rescue?

X-ray sources diffuse gas or point source?Mostly diffuse Mostly discrete

Koyama, Maeda, Sonobe, Takeshima, et al. 1996

Muno, Baganoff, Bautz, Brandt, et al. 2003

Wang, Gotthelf, Lang, 2002

Koyama, Makishima, Tanaka, Tsunemi, 1986

Revnivtsev, Sazonov, Gilfanov, et al. 2006

Warwick, Sakano, Decourchelle, 2006

Muno, Baganoff, Bautz, Brandt, et al. 2004

Koyama, Awaki, Kunieda, Takano, et al., 1989

Tanaka, 2002

Ebisawa, et al., 2005

Koyama et al. 2007Suzaku Dec. 6, 2006

Lazio & Cordes, ApJ 505, 715 (1998)

0.8 107 K

0.1 106 K 10 cm-3

0.1 102 K 104 cm-3

Enter a new category of gas in the CMZ

Warm and diffuse gas250 K 102 cm-3

0.01

?

Summary

Spectroscopy of H3+ has revealed a new category of gas in the

Central Molecular Zone with high temperature (~ 250 K) and low density ( ≤ 100 cm-3) with a large volume filling factor (f ~ 1).CO Oka, Hasegawa, Hayashi, Handa, Sakamoto, ApJ 493, 730 (1998)

Dahmen, Hüttemeister, Wilson, Mauersberger, A&A 331, 959 (1998) H2 Rodriguez-Fernandez, Martin-Pintad, Fuente, et al. A&A 365, 174 (2001)

CH Magnani, Zelenik, Dame, Engebreth, ApJ 636, 267 (2006)

The finding drastically change the previous picture of the gas in the Central Molecular Zone.

We are in the process of observing a wider region of the Central Molecular Zone. We need bright YSO’s!