Warm and diffuse gas and high ionization rate
in the Galactic center revealed
by observation of
H3
+
Takeshi Oka
Department of Astronomy and Astrophysics
and Department of Chemistry
The Enrico Fermi Institute, University of Chicago
Tom Geballe Gemini Observatory
Ben McCall University of Illinois at U-C
Miwa Goto
Max-Planck Institut für Astronomie
NRAO April 21, 2011
CmHn
C60
C4H3+
10458.634 MHz, 25 hrs
46 m Algonquin Telescope
C4H
TMC 1
C4H2+
H2
H2
C4
+
HC11N
+
C3H2
e
e
C2H2
e
+
e
e
CO
C
H3+
+ 2
+
C2H5
CH3
OH
+
HCN H C N
3 3
+
e
HC3N
e
+
C2H
C
CH4
e
+
CH5
CH3OH, e
e
e
H3O
HC5N
+
C
CH3OH2
CH3CO
+
+
H2
H2O
e
H2
C2H5CNH
CH3CN
HCN
CH3+
CO
CH3CNH
NH3
CH3NH2
N
H2
+
CH2
CH
H2O
HC7N
C3H
H2CO
C2H5OH
CH3OCH3
1973
HC9N
C3H
+
+
C2H4
CH2CO
e
C
H2
H2C3O
CH3OH
e
C
C3H3
C3O
Herbst and Klemperer
Watson
+
C4H
H–C≡C–C≡C–C≡C–C≡C–C≡N
H–C≡C–C≡C–C≡C–C≡N
H–C≡C–C≡C–C≡N
1975
14525.850 MHz, 18 hrs
43 m Green Bank Telescope
H
e
H2CN
H2
+
+
H2O
H2
CH
C
+
OH
O
+
+ CO HCO
H2
+
H2
N2
+
N2H
+
+e
+ e
+ e
e
e
C2H5CN
CH3CN
CH2NH
CH3NH2
HCN
H3+, the new astrophysical probe
1975 HC5N, HC7N, HC9N
T.G.
1980
Laboratory Spectrum
H
1951
Oka, Phys. Rev. Lett. 45, 531
H2
1989 - 95
1996
1970
1973
Interstellar H3+, Discovery, Dense Clouds
Geballe, Oka, Nature 384, 334
1999
2002
High H3+ abundance in the Galactic center
Metastable
H3+,
Discovery, Galactic center
Goto, McCall, Geballe, Oka, et al. PASJ 54, 951
2005
H3 +
1996
Revelation of warm and diffuse gass near GC
+
Oka, Geballe, Goto, Usuda, McCall, ApJ 632, 882
2008
Ubiquity Central 30 pc of the Galactic center
Goto, Geballe, Oka, et al. ApJ 688, 306
2010
Exploring wider regions of the Galactic center
Geballe, Oka, ApJ, 709, L70

9
~
10
 
a
2
Telescopes and spectrometers
Telescope
UKIRT
Subaru
Gemini South
VLT
Gemini North
D
3.8 m
8.2 m
8m
8.2 m
8m
Spectrom.
CGS4
IRCS
Phoenix
CRIRES
GENIRS
Gemini North
Subaru
UKIRT
λ/Δλ
40,000 Mauna Kea
1982
20,000 Mauna Kea
2000
60,000 Cerro Pachon 2003
100,000 Cerro Paranal 2006
18,000 Mauna Kea
2011
Gemini South
VLT
Abundant H3
+ in
the Central Molecular Zone
R(1, 1)u R(1, 0)
3 × 1014 cm-2
10-5
10%
T. R. Geballe, Phil. Trans. Roy. Soc. Lond. 200, A358, 2503
CMZ
400 pc
Quintuplet
Cluster
Super-massive clusters
GCS 3-2
1° × 1° 140 pc × 140 pc
(J, K) = (3, 3) metastable H3+, the fingerprint of GC
Goto, McCall, Geballe, Usuda, Kobayashi, Terada, Oka, 2002, PASJ, 54, 951
Spontaneous breakdown of symmetry
(1,1) ground
Para I = 1/2
Ortho I = 3/2
J
(3,3) metastable
8 hrs
20.4 days
(1,0)
16 hrs
(2,2)
(3,3) Metastable
T ~ 250 K
(2,2) unstable
n ≤ 100 cm-3
361 K
27.2 days
CO J = 1
(1,1)
K
Pan and Oka, 1987, ApJ, 305, 518
Oka and Epp, 2004, ApJ, 613, 349
Oka, Geballe, Goto, Usuda, McCall, 2005, ApJ, 632, 882
Simple chemistry of H3+: N(H3+) → ·L

Production H2 → H2+ + e
H2+ + H2 → H + H3+ dn(H3+)/dt = n(H2)
H3+ + e → H + H + H
Destruction
= ken(H3+)n(e)
6
10
H2
5
10
7.3 ×10-8 cm3/s
1.6 ×10-4
4
<1
10
3
10
 L = 2 ke N(H3 (nC/nH)SV RX / f(H2)
2
10
+)
CO
1
10
H
0
10
cm-2
-1
>3
n(X)
3.1
×1015
10
-2
10
-3
 L > 2.2

10
×105
cm/s
+
H3
-4
10
+
C
-5
10
-6
10
L
-7
10
-8
10
10-16 s-1
10-15 s-1
> 700 pc
> 70 pc
Diffuse Clouds
Dense Clouds
-9
10
6
10
5
10
4
10
3
2
10
10
n(H)
1
10
0
10
-1
10
Ubiquity of H3+
Sgr A* to 30 pc East
Goto, et al. 2008, ApJ, 688, 306
30 pc
GCS 4
1.00
NHS 21
0.95
NHS 25
0.90
NHS 42
0.85
FMM 361
0.80
0.75
Super-massive clusters
1° × 1° 140 pc × 140 pc
Search for bright dust-embedded stars for H3+ spectra
GLIMPSE 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 band̲s
Skrutskie et al. 2006, AJ, 131, 1163
- 1.2º < ℓ - ℓº < 1.2º
~ 2,000,000 stars
brightness
L < 7.5
- 0.1º < b - bº < 0.1º
~ 3,000 stars
J - K > 5 K - L > 1.5 (J – K)/(K – L) < 2.5
~ 300 stars
smoothness
Low res. CO first overtone, 2.2 – 2.4μm
Candidate stars
location
High res. H3+ and CO spectroscopy
youth ?
Selected stars
The CO test
Most old (late-type) cool stars are useless
Bright dust-embedded stars with smooth spectrum are scarce
New bright dust-embedded stars
suitable for H3+ spectroscopy
Two sightlines with remarkable H3+ spectrum
0 – 30 pc East
Quintuplet, α, ι
GCS 4
1.00
NHS 21
0.95
α 140 pc West
NHS 25
0.90
NHS 42
0.85
FMM 361
0.80
ι 68 pc East
0.75
0.70
-200
Geballe and Oka, 2010, ApJ, 709, L70-73
-150
-100
-50
0
50
100
ι 68 pc East
H3+ and CO
α 140 pc West
Geballe and Oka, 2010, ApJ, 709, L70-73
Herschel Observatory
H 2+
H 3+
H2
H-
(H2-)
Remarkable similarity between velocity profiles
of H3+ toward Iota and H2O+, 13CH+ toward Sgr B2
H3+
f(H2) = 1 ?
H2O+ 110← 101
H2O+ f(H2) = 0.1
H2O+ 111← 000
17 pc
H3+ R(1,1)l
Schilke et al. 2011, A&A, 521, L11
Geballe & Oka, 2010, ApJ, 709, L70
E. Falgarone et al. 2011
450 μm dust emission in the CMZ (Pierce-Price
et al. 2000). Crosses show the stars toward
which H3+ has been observed (Goto et al 2008,,
Geballe and Oka 2010).
New category of gas in the CMZ
Previous concept drastically changed
T ~ 250 K
n < 100 cm-3
L ~ 60 pc f ~30%
 ~ 1.5 × 1015 s-1
Schultheis et al. 2009, ApJ, 495, 157
?
80 % 107-8 K
10 % 104-6 K ne 10 cm-3
1%
10 % 50 K
104 cm-3
Lazio & Cordes, 1998
ApJ, 505, 715
X-ray: Chandra comes to rescue
Chandra 20 pc × 20 pc (0.5 – 8) keV Muno et al. 2003, ApJ, 589, 225
Warwick, Sakano Decourchelle (2006) Revnivtsev et al. (2006)
Scrutiny at the core
Lo and Claussen, 1983, Nature, 306, 647
HCN
Yusef-Zadeh, Wardle, Roy, 2007, ApJ, 665, L123
The ISAAC L-band image of the Galactic
center showing most of the named sources
(from Viehmann et al. 2005)
Treasure hunting
Galactic Disk
Dense (molecular) clouds
Diffuse clouds
Galactic Center (the Central Molecular Zone)
New category of gas
Circum nuclear disk
Extragalactic Object
Ultraluminous IR galaxies
Magellanic clouds
Circumstellar Space
Planetary nebulae
Planets
Solar planets
Protoplanetary nebulae
IRAS 19312+190, CRL 618
HD 141569A
Proto-planet
Exo-planet
1. Spectroscopy and astronomy
ΔνΔt ~ 1/2π
ν
A
P
t
C
B
High Resolution Spectroscopy
1814
Joseph von Fraunhofer
1787 – 1826
Hα
Na
Fe
Hβ
Fe,Ca
Ca
David Brewster, William Herschel, John Herschel, William Draper, Anders Ångstrom, Armand Fizeau,
William Huggins, Gustav Kirchhoff, Pierre Janssen, Norman Lockyer, Henry Draper, Herman Vogel,
Arthur Schuster, Albert Michelson, Henri Deslandres, William Pickering, Annie Cannon, George Hale,
Alfred Fowler, Ejnar Hertzsprung, Walter Adams, Henry Norris Russel, Edwin Hubble,
Gerhard Herzberg, Charlie Townes