Extending Accretion Diagnostics to the Mid-Infrared Wavelengths
Abstract
The accretion of matter from circumstellar disks onto young stars sets the final stellar mass and contributes to the evolution and dispersal of protoplanetary disks. The rate at which a star is accreting from the circumstellar disk can be estimated using a variety of gas lines spanning from the UV to the near-IR (e.g., Alcala’ et al. 2013). Thanks to the Spitzer Space Telescope, which has revealed a forest of gas lines in the mid-IR in young stars, it is nowadays possible to extend this analysis of the accretion indicators to longer wavelengths, where extinction is lower. To this aim, we have re-reduced and analyzed a sample of ~60 objects in different evolutionary stages observed with the High-resolution module of the InfraRed Spectrograph. We find that the Hydrogen line transitions in the mid-IR (HI at 12.37 and 11.31μm) are bright and common in the Spitzer spectra. Based on the line intensities, ratios and correlation with known accretion indicators at shorter wavelength, we introduce these lines as accretion indicators. We analyze the possibility of using these lines to estimate the accretion from embedded objects, where the other lines fail due to the high-extinction produced by the envelope. We also investigate the presence of these gas lines in old objects, surrounded by a debris disk. This preliminary work paves the way to follow-up ground based observations that can spectrally resolve the lines and to more sensitive observations toward old objects with JWST.
- Publication:
-
American Astronomical Society Meeting Abstracts #223
- Pub Date:
- January 2014
- Bibcode:
- 2014AAS...22335031R