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Issue A&A
Volume 492, Number 3, December IV 2008
Page(s) 731 - 734
Section Interstellar and circumstellar matter
DOI http://dx.doi.org/10.1051/0004-6361:200810723



A&A 492, 731-734 (2008)
DOI: 10.1051/0004-6361:200810723

Research Note

Near-infrared multiwavelength imaging polarimetry of the low-mass proto-stellar object HL Tauri

K. Murakawa1, S. Oya2, T.-S. Pyo2, and M. Ishii2

1  Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn, Germany
    e-mail: murakawa@mpifr-bonn.mpg.de
2  Subaru Telescope, National Astronomical Observatory of Japan, 650 North A'ohoku place, Hilo, HI 96720, USA

Received 31 July 2008 / Accepted 15 October 2008

Abstract
We present the ${\it JHK}$-band high-resolution polarimetric images of the low-mass proto-stellar object HL Tau using the adaptive optics-equipped CIAO instrument on the Subaru telescope. Our polarization images show a butterfly-shaped polarization disk with an ${\sim}0\farcs9\times3\farcs0$ extension. In the nebula, where polarization vectors are centro-symmetrically aligned, the polarization is as high as $P_J \sim30\%$, $P_H\sim42\%$, and $P_K \sim55\%$. On the other hand, low polarizations of P<3% in the J, H, and K bands and a low color excess ratio of EJ-H/EH-K=1.1 compared to the standard cloud value of 1.75 are detected towards the central star. We estimated the upper limit of the grain sizes $a_{\rm max}$ to be 0.4 $\mu$m in the nebula and $\ga$0.7 $\mu$m in the line of sight towards the central star. Our high-resolution polarimetric data, which spatially resolves the polarization disk, provides us with important information about grain growth in the region close to the central star.


Key words: polarization -- ISM: dust, extinction



© ESO 2008

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