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Warm, Dense Gas Near the Massive Protostar AFGL 2136
IRS 1 as Revealed by Absorption from the ν1, ν2, and ν3 Bands of
Water
Nick Indriolo1, David Neufeld1, Andreas Seifahrt2,
& Matt Richter3
1 – Johns Hopkins University2 – University of Chicago
3 – University of California, Davis
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AFGL 2136 IRS 1
Murakawa et al. 2008 A&A, 490, 673de Wit et al. 2011 A&A, 526, L5
0.5" (1000 AU)
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Observations• CRIRES at VLT– high spectral resolution (3 km/s)– high signal-to-noise ratio (~500)
• Targeted v=1-0, R(0) line of HF– Indriolo et al. 2013, ApJ, 764, 188
• 2.47—2.52 μm (gaps between detectors)
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Observations
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Select Spectra
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• 35 absorption features• 47 transitions probing
44 unique rotational levels
• FWHM=13.6±2.5 km/s
• vLSR=24.6±1.1 km/s
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J=5
J=17
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J=17
J=6
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Rotation Diagram
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Model with Radiative Transfer
N(H2O) = (1.02±0.02)×1019 cm-2
n(H2) > 5×109 cm-3
T = 506±25 K
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Previous Water Observations
• ISO observations of ν2 band–N(H2O) = 1.5×1018 cm-2
– T = 500±200 K
Boonman & van Dishoeck 2003, A&A, 403, 1003
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Previous CO Observations• Targeted v=1-0 bands of
12CO and 13CO near 4.7 μm using FTS on CFHT
• Also detected absorption lines from v=2-1 hot band of 12CO
• Found both a warm and cold component– N(12CO) = (1.8±0.5)×1019
cm-2
– n(H2) > 1010 cm-3
– T = 580±60 K
Mitchell et al. 1990, ApJ, 365, 554
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Comparison of ResultsT
(K)n(H2)(cm-3)
N(H2O)(cm-2) OPR Reference
506±25
>5×109
1.02×101
9 3 this work
500±200
... 1.5×1018 ... Boonman & van Dishoeck 2003 A&A, 403, 1003
N(CO)(cm-2)
580±60
>1010 1.8×1019 N/A Mitchell et al. 1990 ApJ, 363, 554• n > 5×109 cm-3 and T=500 K indicative of gas in inner envelope or disk
• Density can be a bit lower with radiative pumping• Estimated path length of 1.3—13 AU• Either way, gas is very close to protostar
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Summary• First study of water absorption in
protostars in the NIR• Results are consistent with warm,
dense gas close to the central protostar• Follow-up program has detected water
absorption toward AFGL 4176• Important new probe of physical
conditions in star-forming environments
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Future Work• CRIRES observations of H2O & CO in
AFGL 2136 are in queue and astrophysical lines will be more optimally shifted from atmospheric lines
• Proposed TEXES observations of pure rotational H2O transitions at 10-13 μm
• EXES on SOFIA covers ν2 band of H2O near 6 μm