Warm and diffuse gas in the cmz revealed by infrared h 3 spectrum
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Warm and diffuse gas in the CMZ revealed by infrared H 3 + spectrum. Takeshi Oka (Chicago), Tom Geballe (Gemini), Miwa Goto (MPIA) Tomonori Usuda (Subaru), Nick Indriolo, Ben McCall (UIUC). with thanks to: Tetsuya Nagata (Kyoto), Tomoharu Oka (Keio)

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Warm and diffuse gas in the cmz revealed by infrared h 3 spectrum

Warm and diffuse gas in the CMZrevealed by infrared H3+ spectrum

Takeshi Oka (Chicago), Tom Geballe (Gemini),Miwa Goto (MPIA)

Tomonori Usuda (Subaru), Nick Indriolo, Ben McCall (UIUC)

with thanks to: Tetsuya Nagata (Kyoto), Tomoharu Oka (Keio)

Farhad Yusef-Zadeh (Northwestern), Kazuo Makishima (Tokyo)

Galactic center workshop 2009, Shanghai, October 19-23, 2009


H3+, the new probe of the CMZ

1975

H

1980

Laboratory Spectrum (IR)

Oka, PRL. 45, 531

T.G.

1951

1996

Interstellar H3+, Discovery, Dense Clouds

Geballe, Oka, Nature 384, 334

H2

1970

1973

  • Surprise - H3+ in GC and diffuse clouds

  • Geballe et al., ApJ, 510, 251, McCall et al. Sci, 279,1910

1998 – 2002 (H3+/H2)diffuse ~ 10 (H3+/H2)dense

McCall et al. ApJ, 522, 338 & 567, 391

H3+

2002 Surprise - discovery of (3,3) metastable line in GC

Gotoet al. PASJ, 54, 951

1996

+

  • 2003ζdiffuse ~ 10ζdenseMcCallet al. Nature 422, 500

  • (2009 - can be explained by increasing low-energy c-r’s

  • Indriolo et al. ApJ, 694, 257)

The three stable

forms of hydrogenand

their discovery dates

in the ISM

  • Revelation of warm and diffuse gas in GC

  • Oka et al. ApJ 632, 882

2008 Probe central 30 pc sightlinesGoto et al. ApJ 688, 306

2009 Sightlines 140 pc W – 100 pc E Geballe, Oka


What do we learn from h 3
What do we learn from H3+ ?

fundamental

IR vib-rot

transitions

3.5-4.0μm

ζL

ζ~ 10-17 s-1 for dense clouds in Gal. Disk

ζ~ 10-16 s-1 for diffuse clouds in GD

ζ ~ 10-15 s-1 for gas in the CMZ

ζ ~ 10-14 s-1 for gas in the CND (?)

H2 ioniz. rate, ζ

J

Path length, L

CO → M

H3+ → L

(if we know ζ,

or ζ if we know L )

361 K

above gnd

27 days

K

rotational levels in v=0

ortho

Temperature, T, density, n

para


Sightline to Quintuplet

source GCS 3-2

(pencil-beam through foreground and CMZ)

narrow components

plus “trough”

CMZ

T ~ 250 K

n≤ 100 cm-3

Spiral

arms

no CO trough

This sightline has little or no CMZ CO.


Eight stars from the center to 30 pc east
Eight stars from the center to 30 pc East

All show absorption trough in (3,3) level

so H3+ ubiquitous

warm and diffuse gas everywhere

High values of ζL for trough (CMZ)

high ionization rate

long path length and volume filling factor

ζL = 2keN(H3+)(nC/nH)SVRX /f

(ζL)min = (1.3 – 4.3) ×105 cm/s

For ζ ~ 3 ×10-16 s-1, L~ 150 – 500 pc clearly absurd

ζ ~ 3× 10-15 s-1L~ 15 – 50 pc

note: these assume solar interstellar C; for constant ζ, L increases as C increases

But even these sightlines sample only a small fraction of the CMZ.


New sightlines

by data-mining GLIMPSE and

2MASS for bright IR sources with

smooth continua (i.e., not RGs)

in or behind the CMZ.

(also hope to use Mauerhan’s stars)

100 pc

140 pc

CO

H3+

GCS 3-2

α

Sgr C

two high vel. mol clouds,

3 kpc arm,

low vel diffuse cl.- no CO

Is it in the CMZ?

ι

Sgr B

~12 vel. components;

largest N(H3+) ever;

is any of it CMZ gas?


The new environment is incompatible with

the previous concept of gas in the CMZ

Previous New

X-ray gas 80 % « 80 %

(Chandra)

Ionized gas 10 % 10 %

Molecular gas 10 % few %

AV~ 30

Diffuse gas 0% > 10%


Conclusion
CONCLUSION

Not only is the average density

of the CMZ ~ 100 cm-3 (Martin-Pintado – this meeting),

but also a significant (and perhaps dominant) fraction of the

CMZ’s volume actually is filled with warm gas

at about that density!

Spitzer+VLA



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