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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

• 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