Space-based Coronagraphic Imaging Polarimetry of the TW Hydrae Disk: Shedding New Light on Self-shadowing Effects
Name:
Poteet_2018_ApJ_860_115.pdf
Size:
2.836Mb
Format:
PDF
Description:
Final Published version
Author
Poteet, Charles A.Chen, Christine H.
Hines, Dean C.

Perrin, Marshall

Debes, John H.

Pueyo, Laurent
Schneider, Glenn

Mazoyer, Johan
Kolokolova, Ludmilla
Affiliation
Univ Arizona, Steward ObservIssue Date
2018-06-20Keywords
circumstellar matterpolarization
protoplanetary disks
stars: individual (TW Hya)
stars: pre-main sequence
Metadata
Show full item recordPublisher
IOP PUBLISHING LTDCitation
Charles A. Poteet et al 2018 ApJ 860 115Journal
ASTROPHYSICAL JOURNALRights
© 2018. The American Astronomical Society. All rights reserved.Collection Information
This item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at repository@u.library.arizona.edu.Abstract
We present Hubble Space Telescope Near-Infrared Camera and Multi-Object Spectrometer coronagraphic imaging polarimetry of the TW Hydrae protoplanetary disk. These observations simultaneously measure the total and polarized intensity, allowing direct measurement of the polarization fraction across the disk. In accord with the self-shadowing hypothesis recently proposed by Debes et al., we find that the total and polarized intensity of the disk exhibits strong azimuthal asymmetries at projected distances consistent with the previously reported bright and dark ring-shaped structures (similar to 45-99 au). The sinusoidal-like variations possess a maximum brightness at position angles near similar to 268 degrees-300 degrees and are up to similar to 28% stronger in total intensity. Furthermore, significant radial and azimuthal variations are also detected in the polarization fraction of the disk. In particular, we find that regions of lower polarization fraction are associated with annuli of increased surface brightness, suggesting that the relative proportion of multiple-to-single scattering is greater along the ring and gap structures. Moreover, we find strong (similar to 20%) azimuthal variation in the polarization fraction along the shadowed region of the disk. Further investigation reveals that the azimuthal variation is not the result of disk flaring effects, but is instead from a decrease in the relative contribution of multiple-to-single scattering within the shadowed region. Employing a two-layer scattering surface, we hypothesize that the diminished contribution in multiple scattering may result from shadowing by an inclined inner disk, which prevents direct stellar light from reaching the optically thick underlying surface component.ISSN
1538-4357Version
Final published versionSponsors
NASA from the Space Telescope Science Institute [HST-AR-12630]; Association of Universities for Research in Astronomy, Incorporated, under NASA [NAS 5-26555]Additional Links
http://stacks.iop.org/0004-637X/860/i=2/a=115?key=crossref.e15f98d2a34644dbbb4fca9470f0a407ae974a485f413a2113503eed53cd6c53
10.3847/1538-4357/aac2e4