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H 3 +. H 3 + , a new astrophysical probe: Revelation of warm and diffuse gas near the Galactic center. Takeshi Oka Department of Astronomy and Astrophysics and Department of Chemistry, The Enrico Fermi Institute The University of Chicago. Thomas R. Geballe Gemini Observatory

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slide2

H3+, a new astrophysical probe:

Revelation of warm and diffuse gas

near the Galactic center

Takeshi Oka

Department of Astronomy and Astrophysics and

Department of Chemistry, The Enrico Fermi Institute

The University of Chicago

Thomas R. GeballeGemini Observatory

Miwa GotoMax Planck Institute for Astronomy

Tomonori UsudaSubaru Telescope

Benjamin J. McCallUniversity of Illinois, Urbana-Champaign

Tetsuya Nagata Kyoto University

Tomoharu Oka University of Tokyo

Farhad Yusef-Zadeh Northwestern University

Harvey Liszt National Radio Astronomy Observatory

June 27, 2007 CSO

slide3

Thumbnail sketch of H3+

p

p

Simplest polyatomic molecule

c.r.

H

1951

Simple chemistry

H2→ H2+ + e H2+ + H2 → H + H3+

H2

CO

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

1970

X(H3+)diffuse ~ 10X(H3+)dense

Powerful informant of:

Cosmic ray ionization rate ζ

Temperature T density n

Radial length of clouds L

H3+

1996

+

ζL = 2 keN(H3+) (nC/nH)

slide4

Progress of H3+observation

1989 - 95

1996

Interstellar H3+, Discovery

Geballe, Oka, Nature 384, 334

ζdiffuse~!0 ζdense

1998 – 2002 Ubiquity, Dense and Diffuse Clouds

McCall, Geballe, Hinkle, Oka

1975

1980

Laboratory Spectrum

Oka, PRL. 45, 531

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

Kobayashi, Terada, OkaPASJ, 54, 951

  • Hot and Diffuse Clouds near GC Probed by Metastable H3+
  • Oka, Geballe, Goto, Usuda, McCall, ApJ 632, 882
slide5

GCS3-2

Inferred face-on view of the Central Molecular Zone

Quintuplet

130 pc

130 pc

100 km s-1

100 km s-1

Sawada, Hasegawa, Handa, Cohen, MNRAS 349, 1167 (2004)

Oka, Hasegawa, Sato, Tsuboi, Miyazaki, ApJS 118, 455 (1998)

telescope and spectrometer
Telescope and spectrometer

UKIRT 3.8 m CGS4 8 km s-1 Mauna Kea 1982

Subaru8.2 m IRCS 15 km s-1 Mauna Kea 2000

Gemini South 8 m Phoenix 5 km s-1 Cerro Pachon 2003

VLT 8.2 m CRIRES ≤3 km s-1 Cerro Paranal 2006

breaking symmetry

The ideal rotational levels of H3+

Breaking Symmetry

OrthoI = 3/2

J

ParaI = 1/2

Metastable

8 hrs

(3,3)

16 hrs

μ

(2,2)

361 K

20.4 days

Unstable

Critical Density

200 cm-3

27.2 days

Ground

(1,1)

K

Collision H3+ + H2→ (H5+)* → H3+ + H2

Interstellar NH3Oka, Shimizu, Shimizu, Watson, ApJ 165, L15 (1971)

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

Oka, Epp, ApJ 613, 349 (2004)

central molecular zone is the treasure house of h 3
Central Molecular Zone is the Treasure Houseof H3+

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

N(H3+) = 4.4 × 1015 cm-2

N(H3+) = 3.8 × 1014 cm-2

L = 21 pc

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

slide9

Spectroscopy

(1,1) ground

(3,3) metastable

T = 250 K

(2,2) unstable

130 pc

n≤ 100 cm-3

100 km s-1

CO J = 1

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

slide10

L (pc)

ζ (s-1)

10-16 (0.8 - 2.1) k

10-1580 - 210

Dimension of the discovered gas

7.3 ×10-8 cm3/s

1.6 ×10-4

ζL = 2 keN(H3+) (nC/nH)SV RX

3.1 ×1015 cm-2

3 - 10

COBE DIRBE

Sodroski et al ApJ 452, 262 (1995)

ζL = (2.5 – 8.4) ×105 cm/s

130 pc

100 km s-1

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

slide11

8 stars within 30 pc from GC

All show high T and low n

(2,2) densitometer

(1,1) ground level

(3,3) thermometer

T = 220 - 400 K

n ≤ 100 cm-3

(2,2) densitometer

(1,1) ground level

(3,3) thermometer

slide12

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

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

N(H3+) = (2.3 - 4.5) × 1015 cm-2

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

slide13

Enter a new category of gas in the CMZ

?

0.8 107 K

?

0.1 106 K 10 cm-3

250 K102 cm-3

Warm and diffuse gas

0.1 102 K 104 cm-3

Lazio & Cordes, ApJ 505, 715 (1998)

that is incompatible with two other gases

slide14

X-ray: Chandra comes to rescue?

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

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

slide15

X-ray sources diffuse gas or point source?

Suzaku Dec. 6, 2006

Mostly diffuse

Mostly discrete

Koyama, Makishima, Tanaka, Tsunemi, 1986

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

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

Tanaka, 2002

Wang, Gotthelf, Lang, 2002

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

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

Ebisawa, et al., 2005

Warwick, Sakano, Decourchelle, 2006

Revnivtsev, Sazonov, Gilfanov, et al. 2006

Koyama et al. 2007

slide16

Enter a new category of gas in the CMZ

0.8 107 K

?

0.1 106 K 10 cm-3

250 K102 cm-3

Warm and diffuse gas

0.1 102 K 104 cm-3

0.01

Lazio & Cordes, ApJ 505, 715 (1998)

slide17

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)

H2Rodriguez-Fernandez, Martin-Pintad, Fuente, et al. A&A365, 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!