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Title: SPECTRALLY RESOLVED PURE ROTATIONAL LINES OF WATER IN PROTOPLANETARY DISKS

We present ground-based high-resolution N-band spectra ({Delta}v = 15 km s{sup -1}) of pure rotational lines of water vapor in two protoplanetary disks surrounding the pre-main-sequence stars AS 205N and RNO 90, selected based on detections of rotational water lines by the Spitzer InfraRed Spectrograph. Using VISIR on the Very Large Telescope, we spectrally resolve individual lines and show that they have widths of 30-60 km s{sup -1}, consistent with an origin in Keplerian disks at radii of {approx}1 AU. The water lines have similar widths to those of the CO at 4.67 {mu}m, indicating that the mid-infrared water lines trace similar radii. The rotational temperatures of the water are 540 and 600 K in the two disks, respectively. However, the line ratios show evidence of non-LTE excitation, with low-excitation line fluxes being overpredicted by two-dimensional disk LTE models. Due to the limited number of observed lines and the non-LTE line ratios, an accurate measure of the water ortho/para (O/P) ratio is not available, but a best estimate for AS 205N is O/P =4.5 {+-} 1.0, apparently ruling out a low-temperature origin of the water. The spectra demonstrate that high-resolution spectroscopy of rotational water lines is feasible from the ground,more » and further that ground-based high-resolution spectroscopy is likely to significantly improve our understanding of the inner disk chemistry revealed by recent Spitzer observations.« less
Authors:
; ;  [1] ;  [2]
  1. California Institute of Technology, Division of Geological and Planetary Sciences, MS 150-21, Pasadena, CA 91125 (United States)
  2. European Southern Observatory, Karl-Schwarzschild-Strasse 2, 85748 Garching bei Muenchen (Germany)
Publication Date:
OSTI Identifier:
21452741
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal Letters; Journal Volume: 722; Journal Issue: 2; Other Information: DOI: 10.1088/2041-8205/722/2/L173
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; CARBON MONOXIDE; MAIN SEQUENCE STARS; PROTOPLANETS; SPECTROSCOPY; TELESCOPES; WATER VAPOR CARBON COMPOUNDS; CARBON OXIDES; CHALCOGENIDES; FLUIDS; GASES; OXIDES; OXYGEN COMPOUNDS; STARS; VAPORS