TY - JOUR
T1 - Polarimetry with the gemini planet imager
T2 - Methods, performance at first light, and the circumstellar ring around HR 4796A
AU - Perrin, Marshall D.
AU - Duchene, Gaspard
AU - Millar-Blanchaer, Max
AU - Fitzgerald, Michael P.
AU - Graham, James R.
AU - Wiktorowicz, Sloane J.
AU - Kalas, Paul G.
AU - Macintosh, Bruce
AU - Bauman, Brian
AU - Cardwell, Andrew
AU - Chilcote, Jeffrey
AU - De Rosa, Robert J.
AU - Dillon, Daren
AU - Doyon, René
AU - Dunn, Jennifer
AU - Erikson, Darren
AU - Gavel, Donald
AU - Goodsell, Stephen
AU - Hartung, Markus
AU - Hibon, Pascale
AU - Ingraham, Patrick
AU - Kerley, Daniel
AU - Konapacky, Quinn
AU - Larkin, James E.
AU - Maire, Jérôme
AU - Marchis, Franck
AU - Marois, Christian
AU - Mittal, Tushar
AU - Morzinski, Katie M.
AU - Oppenheimer, B. R.
AU - Palmer, David W.
AU - Patience, Jennifer
AU - Poyneer, Lisa
AU - Pueyo, Laurent
AU - Rantakyrö, Fredrik T.
AU - Sadakuni, Naru
AU - Saddlemyer, Leslie
AU - Savransky, Dmitry
AU - Soummer, Rémi
AU - Sivaramakrishnan, Anand
AU - Song, Inseok
AU - Thomas, Sandrine
AU - Wallace, J. Kent
AU - Wang, Jason J.
AU - Wolff, Schuyler G.
N1 - Publisher Copyright:
© 2015. TheAmerican Astronomical Society. All rights reserved.
PY - 2015/2/1
Y1 - 2015/2/1
N2 - We present the first results from the polarimetry mode of the Gemini Planet Imager (GPI), which uses anew integral field polarimetry architecture to provide high contrast linear polarimetry with minimal systematic biases between the orthogonal polarizations. We describe the design, data reduction methods, and performance of polarimetry with GPI. Point-spread function (PSF) subtraction via differential polarimetry suppresses unpolarized starlight by a factor of over 100, and provides sensitivity to circumstellar dust reaching the photon noise limit for these observations. in the case of the circumstellar disk around HR 4796A,GPI's advanced adaptive optics system reveals the disk clearly even prior to PSF subtraction. In polarized light, the disk is seen all the way in to its semi-minor axis for the first time. The disk exhibits surprisingly strong asymmetry in polarized intensity, with the west side ≳9 times brighter than the east side despite the fact that the east side is slightly brighter in total intensity. Based on a synthesis of the total and polarized intensities, we now believe that the west side is closer to us, contrary to most prior interpretations. Forward scattering by relatively large silicate dust particles leads to the strong polarized intensity on thewest side, and the ring must be slightly optically thick in order to explain the lower brightness in total intensity there. These findings suggest that the ring is geometrically narrow and dynamically cold, perhaps shepherded by larger bodies in the same manner as Saturn's Fring.
AB - We present the first results from the polarimetry mode of the Gemini Planet Imager (GPI), which uses anew integral field polarimetry architecture to provide high contrast linear polarimetry with minimal systematic biases between the orthogonal polarizations. We describe the design, data reduction methods, and performance of polarimetry with GPI. Point-spread function (PSF) subtraction via differential polarimetry suppresses unpolarized starlight by a factor of over 100, and provides sensitivity to circumstellar dust reaching the photon noise limit for these observations. in the case of the circumstellar disk around HR 4796A,GPI's advanced adaptive optics system reveals the disk clearly even prior to PSF subtraction. In polarized light, the disk is seen all the way in to its semi-minor axis for the first time. The disk exhibits surprisingly strong asymmetry in polarized intensity, with the west side ≳9 times brighter than the east side despite the fact that the east side is slightly brighter in total intensity. Based on a synthesis of the total and polarized intensities, we now believe that the west side is closer to us, contrary to most prior interpretations. Forward scattering by relatively large silicate dust particles leads to the strong polarized intensity on thewest side, and the ring must be slightly optically thick in order to explain the lower brightness in total intensity there. These findings suggest that the ring is geometrically narrow and dynamically cold, perhaps shepherded by larger bodies in the same manner as Saturn's Fring.
KW - Circumstellar matter
KW - Instrumentation: adaptive optics
KW - Instrumentation: high angular resolution
KW - Instrumentation: polarimeters
KW - Polarization
KW - Stars: individual (HR 4796A)
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U2 - 10.1088/0004-637X/799/2/182
DO - 10.1088/0004-637X/799/2/182
M3 - Article
AN - SCOPUS:84922318946
SN - 0004-637X
VL - 799
JO - Astrophysical Journal
JF - Astrophysical Journal
IS - 2
M1 - 182
ER -