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T. Dupuy (Univ. of Texas), B. Reipurth (IfA, Univ. of Hawaii), J. Bally (CASA, Univ. of Colorado)
We investigate the use of narrow-band images of star-forming regions as a way to identify T Tauri stars from photometry. This method would be particularly useful in studying distant star-forming regions where spectroscopic surveys are more difficult to conduct. In principle, H\alpha emission can be detected using one narrow-band filter on the H\alpha line and another off the line to measure the nearby continuum. We have a large data archive of images of star-forming regions centered on the H\alpha line and on the [S II] 6717/6731 lines, and have studied the feasibility of using the latter as a continuum filter. We conclude that such a filter of any bandpass width, no matter how narrow, would permit the identification of many, but not all, classical T Tauri stars (H\alpha equivalent widths down to 10 Å). This is due to the appearance within the H\alpha filter of a titanium oxide band for late-type stars. In order to unambiguously detect all stars with H\alpha emission, even for very late types, the continuum filter must be narrower and located nearer the H\alpha line. Two filters abutting each other (e.g. a 20 Åbandpass filter at \lambda6583 Åor even a 40 Åbandpass filter at \lambda6603 Å) would allow the identification of all T Tauri stars that do not suffer extreme reddening.
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Bulletin of the American Astronomical Society, 35#5
© 2003. The American Astronomical Soceity.