M. Krejny et al. 2009 ApJ 705 717 doi:10.1088/0004-637X/705/1/717
M. Krejny1,6, T. G. Matthews1, G. Novak1, J. Cho2, H. Li3, H. Shinnaga4 and J. E. Vaillancourt5
Show affiliationsWe present the first 350 μm polarization measurement for the disk of the T Tauri star (TTS) DG Tau. The data were obtained using the SHARP polarimeter at the Caltech Submillimeter Observatory. We measured normalized Stokes parameters q= –0.0086 ± 0.0060 and u = –0.0012 ± 0.0061, which gives a 2σ upper limit for the percent polarization of 1.7%. We obtain information about the polarization spectrum by comparing our 350 μm measurement with an 850 μm polarization detection previously published for this source. Comparing the two measurements in Stokes space (not in percent polarization) shows that the two data points are not consistent, i.e., either the degree of polarization or the angle of polarization (or both) must change significantly as one moves from 850 μm to 350 μm. This conclusion concerning the polarization spectrum disagrees with the predictions of a recent model for TTS disk polarization. We show that this discrepancy can be explained by optical depth effects. Specifically, we demonstrate that if one were to add more mass to the model disk, one would expect to obtain a model polarization spectrum in which the polarization degree falls sharply with increasing frequency, consistent with the observations at the two wavelengths. We suggest that multiwavelength polarimetry of TTS disk emission may provide a promising method for probing the opacity of TTS disks.
polarization; planetary systems: protoplanetary disks; stars: individual (DG Tau); submillimeter
Issue 1 (2009 November 1)
Received 2009 April 27, accepted for publication 2009 September 21
Published 2009 October 14
M. Krejny et al. 2009 ApJ 705 717
D T Riley et al 2008 Bioinspir. Biomim. 3 026003
Peter Laursen and Jesper Sommer-Larsen 2007 ApJ 657 L69
S. Pirandola et al 2008 EPL 84 20013
F. X. Timmes et al. 2000 ApJS 129 377
Matthew D. Covington et al. 2010 ApJ 710 279
Jean-Philippe Bernard et al. 2008 The Astronomical Journal 136 919
Bahram Mobasher et al. 2009 ApJ 690 1074
G. R. Cook et al. 2009 ApJ 704 1021
F. X. Timmes 1999 ApJS 124 241