Revelation of a vast amount of warm (~ 250 K) and diffuse (≤ 100 cm-3) gas and high ionization rate (ζ > 10-15 s-1)

in the Central Molecular Zone by the Infrared Spectrum of

H3+

Takeshi Oka

Department of Astronomy and Astrophysics and Department of Chemistry

The Enrico Fermi Institute, University of Chicago

Star formation under extreme conditions: the Galactic center

at the Besançon Observatory, December 7, 2010

Tom Geballe Gemini ObservatoryMiwa Goto Max-Planck Institut für Astronomie

2005 Revelation of warm and diffuse gass near GC Oka, Geballe, Goto, Usuda, McCall, ApJ 632, 882

1999 High H3+ abundance in the Galactic center

H3+, the new astrophysical probe

+

1951

19701973

1996

1980 Oka, Phys. Rev. Lett. 45, 531Laboratory Spectrum

1996Geballe, Oka, Nature 384, 334

Interstellar H3+, Discovery, Dense Clouds

H

H2

H3+

1989 - 95

2002 Metastable H3+, Discovery, Galactic center

Goto, McCall, Geballe, Oka, et al. PASJ 54, 951

1975 HC5N, HC7N, HC9N

2008 Ubiquity Central 30 pc of the Galactic center Goto, Geballe, Oka, et al. ApJ 688, 306

T.G.

2010 Exploring wider regions of the Galactic center Geballe, Oka, ApJ, 709, L70

92

10~

a

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

Subaru UKIRTGemini South

VLT

Gemini North

Quintuplet Cluster

1° × 1° 140 pc × 140 pc

Super-massive clusters

GCS 3-2

High abundance of H3+ in the CMZ

CMZ

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

T. R. Geballe, Phil. Trans. Roy. Soc. Lond. A358, 2503 (2000)

3 × 1014 cm-2

10-5

10%

400 pc

(J, K) = (3, 3) metastable H3+, the fingerprint of GC

Metastable

27.2 days

20.4 days

Ortho I = 3/2

Para I = 1/2J

K

16 hrs8 hrs (3,3)

(2,2)

(1,1)

Pan and Oka, 1987, ApJ, 305, 518

(1,0)

Goto, McCall, Geballe, Usuda, Kobayashi, Terada, Oka, 2002, PASJ 54, 951

361 K

CO J = 1

(2,2) unstable

(3,3) metastable

(1,1) ground

T ~ 250 K

n ≤ 100 cm-3

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

Spontaneous breakdown of symmetry

Ubiquity of H3+

Sgr A* to 30 pc East

30 pc

1° × 1° 140 pc × 140 pc

Super-massive clusters

Search for bright and hot stars in the CMZGLIMPSE Point Source Catalogue of the Spitzer Space Telescope, L to M Ramírez et al. 2008, ApJS, 175, 147

2MASS photometry at J, H, and K bandM sSkrutskie et al. 2006, AJ, 131, 1163

~ 2,000,000 stars

L < 7.5

~ 3,000 stars

(J – K)/(K – L) < 2.5K - L > 1.5J - K > 5

~ 300 stars

Low res. CO first overtone, 2.2 – 2.4μm

Candidate stars

Selected stars

High res. H3+ and CO spectroscopy

brightness

youth

hotness

location

- 1.2º < ℓ - ℓº < 1.2º - 0.1º < b - bº < 1.0º

The CO testOld (late-type) cool stars are uselessBright, young, hot stars are scarce

New bright and hot dust embedded stars suitable for H3

+ spectroscopy

Geballe and Oka, ApJ, 709, L70-73 (2010)

Two sightlines with remarkable H3+ spectrum

α

ι

Geballe and Oka, ApJ, 709, L70-73 (2010)

0 – 30 pc EastQuintuplet, α, ι

Simple chemistry of H3+ → ·L

Destruction H3+ + e → H + H + H

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

+

Production H2 → H2+ + e H2

+ + H2 →H + H3+

L = 2 ke N(H3+) (nC/nH)SV RX / f

7.3 ×10-8 cm3/s 1.6 ×10-4 1

(1.8-6.1) ×1015 cm-2 3

( L)min = (1.3 – 4.3) ×105 cm/s

L

10-16 s-1 (0.4 – 1.4) kpc 10-15 s-1 40 - 140 pc

Goto, Usuda, Nagata, Geballe, Indriolo, McCall, Suto, Henning, Morong, and Oka, ApJ, 668, 306 (2008)

dn(H3+)/dt = n(H2)

= ken(H3+)n(e)

Lazio & Cordes, ApJ, 505, 715 (1998)

80% 107-8 K

10% 104-6 K ne 10 cm-3

10% 50 K 104 cm-3

New category of gas in the CMZ

f:

Previous concept drastically changedT ~ 250 Kn ~ 100 cm-3

L ~ 60 pc f ~30%

~ 1.5 × 1015 s-1

Schultheis et al. ApJ 495, 157 (2009)

2%

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

Remarkable similarity between velocity profilesof H3

+ toward Iota and H2O+, CH+ toward Sgr B2 Herschel observations of ortho- and para-oxidaniumyl (H2O+) in spiral arm clouds toward Sgr B2(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. Zaal21A&A June 22 2010

Geballe & Oka, 2010, ApJ, 709, L70

H3+ R(1,1)l

H2O+ 111← 000

H2O+ 110← 101

17 pc

3 kpc ScutumSgittarius

E. Falgarone et al. 2010

NH3 Metastable rotational levels

0 1 2 30

1

2

3

J

K

NH3

ΔK = 0

0 1 2 30

1

2

3

J

K

NH3

NH3 Metastable rotational levels

Δk = 3

Metastable rotational levels

0

1

2

3

JNH3

μ

T. Oka, F. O. Shimizu, T. Shimizu, J. K. G. Watson, ApJ 165, L15 (1971)

50 years

Δk = 3 2

00 years

H3+ is simpler

0

1

2

3

J

Δk = 3

H3+

Non-polar

No inversion