Transcript 07Columbus.ppt

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Spectroscopy of H3 and CO
toward the Galactic center
Takeshi Oka, Christopher P. Morong, Department of Astronomy
And Astrophysics and Department of Chemistry University of Chicago
Thomas R. Geballe, Gemini Observatory, Hilo, Hawaii
Miwa Goto, Max Planck Institute for Astronomy, Heidelberg, Germany
Tomonori Usuda, Kumiko S. Usuda, Subaru Telescope, Hilo Hawaii
Nicholas Indriolo, Benjamin J. McCall, Department of Chemistry and
Department of Astronomy, University of Illinois at Urbana-Champaign
June 19, 2007 Columbus Meeting
Inferred face-on view of the Central Molecular Zone
The Expanding Molecular Ring
130 pc
200 pc
100 km s-1
EMR
145 km s-1
Scoville, ApJ 175, L127 (1972)
Sawada, Hasegawa, Handa, Cohen, MNRAS 349, 1167 (2004)
Oka, Hasegawa, Sato, Tsuboi, Miyazaki, ApJS 118, 455 (1998)
Telescope and spectrometer
UKIRT
3.8 m
Subaru
8.2 m
Gemini South 8 m
VLT
8.2 m
CGS4
40,000
IRCS
20,000
Phoenix 60,000
CRIRES 100,000
Mauna Kea
Mauna Kea
Cerro Pachon
Cerro Paranal
1982
2000
2003
2006
The ideal rotational levels of H3+
Ortho I = 3/2
Breaking Symmetry
μ
J
Para I = 1/2
8 hrs
20.4
days
Unstable
16 hrs
(2,2)
(3,3)
361 K
27.2 days
(1,1)
Metastable
Ground
Critical Density
200 cm-3
K
Collision
H3+ + H2 → (H5+)* → H3+ + H2
Interstellar NH3
Oka, Shimizu, Shimizu, Watson, ApJ 165, L15 (1971)
Interstellar H3+
Pan, Oka, ApJ 305, 518 (1986)
Oka, Epp, ApJ 613, 349 (2004)
Spectroscopy
(1,1) ground
(3,3) metastable
130 pc
(2,2) unstable
100 km s-1
CO J = 1
Oka, Geballe, Goto, Usuda, McCall, ApJ 632, 882 (2005)
Dimension of the discovered gas
7.3 ×10-8 cm3/s
1.6 ×10-4
1
ζL = 2 ke N(H3+) (nC/nH)SV RX / f
3.1 ×1015 cm-2
3 - 10
COBE DIRBE
Sodroski et al ApJ 452, 262 (1995)
ζL = (2.5 – 8.4) ×105 cm/s
120 pc
100 km s-1
ζ (s-1)
L (pc)
10-16
10-15
(0.8 - 2.1) k
80 - 210
Oka, Geballe, Goto, Usuda, McCall, ApJ 632, 882 (2005)
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
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
Enter a new category of gas in the CMZ
?
?
0.8
107 K
0.1
106 K 10 cm-3
0.1
102 K 104 cm-3
0.01
250 K 102 cm-3
Warm and diffuse gas
Lazio & Cordes, ApJ 505, 715 (1998)
that is incompatible with two other gases
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)
The hyper-strong radio scattering
caused by folded magnetic field
rather than hot electrons?
Folded fields as the source of extreme radiowave scattering in the Galactic center
Goldreich and Sridhar, ApJ 640, L159 (2006)
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).
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!
ζ = 10-17s-1
ζ = 10-17s-1
Harvey Liszt Phil. Trans. R. Soc. A 364, 3049 (2006)