AT20G compact HII region Survey: Spitzer character of the sources in the MIR

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AT20G compact HII region Survey Spitzer
character of the sources in the MIR
Martin Cohen, University of California/Berkeley
Hyper Compact HII regions Workshop 8 September
2010
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Outline

• What is the relationship betweenMIR/radio?
• Radio - ionized gas MIR - PAHs in PDRs
• Matched-resolution (MOST) 843MHz (MSX) 8.3?m
  Galactic Plane images Cohen Green ratio
  F?(8.3?m)/S?(843MHz)
• Thermal radio emission median 255
• AT20G sources have at least three classes of MIR
  counterpart

Cohen Green 2001, MNRAS, 325, 531 Cohen et al.
2007, MNRAS, 374, 979
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Extragalactic MIR countperparts
8?m absent or faint 24 ?m well detected
and planetary nebulae
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GLIMPSE Benjamin et al. 2003 PASP, 115, 953
45"
1983
1996
2004
19"
1.7"
b1.1
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Resolution sensitivity changes MSX?Spitzer
IRAC for HII regions
MSX 8.3?m
IRAC 8.0?m
19GHz 15 beam
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How are MIR and radio related?
Radio (black) ionized gas IR (white) hydrocarbon
molecules in the PDR
Mid-IR MSX 8.3?m
Far-IR emission from dust heated by the star
Radio MOST 843MHz
Radio
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MIR morphology of HII regions 4.5 5.8 8.0?m 234
Compact
Ultra-compact
Cometary
Compact
HII
Compact
Compact
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Samples of the AT20G UCHII regions
Almost no MIR UC regions are found. Mostly
small groups or pairs of compact and diffuse HII.
IRAC false colours separate UC white (dust)
emission from compact and diffuse yellow (PAHs)
MIR/Radio 42

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An IRAC color-color plane
Emphasizes PNe HII regions
dH
H
F?(8.3?m)/S?(843MHz) Diffuse HIImedian 25 PNe
median 5 UC HII median 42 HII compact
median 140 (very small set)
P
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Radio-MIR comparisons of groups (1)
1235-6302
1555-5243
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Radio-MIR comparisons of groups (2)
1547-5448
H2?
1609-5154
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Hyper Ultra compact MIR countperparts
G301 H
G323 H
G309 H
G330 H
G307 U
G332 U
G302 U
G328 U
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Optical extinction along lines of sight

• Use deep silicate absorptions at 10,18 ?m