Candidate Water Vapor Lines to Locate the H{sub 2}O Snowline Through High-dispersion Spectroscopic Observations. II. The Case of a Herbig Ae Star

Journal Article · Fri Feb 10 04:00:00 EST 2017 · Astrophysical Journal

DOI:https://doi.org/10.3847/1538-4357/836/1/118· OSTI ID:22869355

Notsu, Shota; Ishimoto, Daiki ^[1]; Nomura, Hideko ^[2]; Walsh, Catherine ^[3]; Honda, Mitsuhiko ^[4]; Hirota, Tomoya ^[5]

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1. Department of Astronomy, Graduate School of Science, Kyoto University, Kitashirakawa-Oiwake-cho, Sakyo-ku, Kyoto 606-8502 (Japan)
2. Department of Earth and Planetary Science, Tokyo Institute of Technology, 2-12-1 Ookayama, Meguro-ku, Tokyo 152-8551 (Japan)
3. Leiden Observatory, Leiden University, P.O. Box 9513, 2300 RA Leiden (Netherlands)
4. Department of Physics, School of Medicine, Kurume University, 67 Asahi-machi, Kurume, Fukuoka 830-0011 (Japan)
5. National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka, Tokyo 181-8588 (Japan)

Observationally measuring the location of the H{sub 2}O snowline is crucial for understanding planetesimal and planet formation processes, and the origin of water on Earth. In disks around Herbig Ae stars (T {sub *} ∼ 10,000 K, M {sub *} ≳ 2.5M {sub ⊙}), the position of the H{sub 2}O snowline is farther from the central star compared with that around cooler and less massive T Tauri stars. Thus, the H{sub 2}O emission line fluxes from the region within the H{sub 2}O snowline are expected to be stronger. In this paper, we calculate the chemical composition of a Herbig Ae disk using chemical kinetics. Next, we calculate the H{sub 2}O emission line profiles and investigate the properties of candidate water lines across a wide range of wavelengths (from mid-infrared to submillimeter) that can locate the position of the H{sub 2}O snowline. Those lines identified have small Einstein A coefficients (∼10{sup −6}--10{sup −3} s{sup −1}) and relatively high upper-state energies (∼1000 K). The total fluxes tend to increase with decreasing wavelengths. We investigate the possibility of future observations (e.g., ALMA, SPICA/SMI-HRS) locating the position of the H{sub 2}O snowline. Since the fluxes of those identified lines from Herbig Ae disks are stronger than those from T Tauri disks, the possibility of a successful detection is expected to increase for a Herbig Ae disk.

• OSTI ID: 22869355
• Journal Information: Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 1 Vol. 836; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
COMPARATIVE EVALUATIONS
DETECTION
DISPERSIONS
EMISSION
MOLECULES
PLANETS
PROTOPLANETS
STAR EVOLUTION
T TAURI STARS
WATER VAPOR