Candidate Water Vapor Lines to Locate the H2O Snowline through High-dispersion Spectroscopic Observations. II. The Case of a Herbig Ae Star
Abstract
Observationally measuring the location of the {{{H}}}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 * ∼ 10,000 K, M * ≳ 2.5M ⊙), the position of the {{{H}}}2{{O}} snowline is farther from the central star compared with that around cooler and less massive T Tauri stars. Thus, the {{{H}}}2{{O}} emission line fluxes from the region within the {{{H}}}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}}}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}}}2{{O}} snowline. Those lines identified have small Einstein A coefficients (∼ {10}-6{--}{10}-3 s-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}}}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.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- February 2017
- DOI:
- 10.3847/1538-4357/836/1/118
- arXiv:
- arXiv:1701.04381
- Bibcode:
- 2017ApJ...836..118N
- Keywords:
-
- astrochemistry;
- infrared: planetary systems;
- ISM: molecules;
- protoplanetary disks;
- stars: formation;
- submillimeter: planetary systems;
- Astrophysics - Earth and Planetary Astrophysics;
- Astrophysics - Solar and Stellar Astrophysics
- E-Print:
- 39 pages, 14 figures, and 2 tables are contained in this paper. It was received by The Astrophysical Journal (ApJ) on October 27th, 2016, and was accepted on January 13th, 2017. arXiv admin note: text overlap with arXiv:1606.05828