EDP Sciences
Free Access
Volume 403, Number 1, May III 2003
Page(s) 323 - 328
Section The Sun
DOI https://doi.org/10.1051/0004-6361:20030362

A&A 403, 323-328 (2003)
DOI: 10.1051/0004-6361:20030362

Large grains in the disk of CQ Tau

L. Testi1, A. Natta1, D. S. Shepherd2 and D. J. Wilner3

1  Osservatorio Astrofisico di Arcetri, INAF, Largo E. Fermi 5, 50125 Firenze, Italy
2  National Radio Astronomy Observatory, PO Box O, Socorro, NM 87801, USA
3  Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA

(Received 3 January 2003 / Accepted 4 March 2003)

We present 7 mm observations of the dusty disk surrounding the 10 Myr old $1.5~ M_\odot$ pre-main-sequence star CQ Tauri obtained at the Very Large Array with 0.8 arcsec resolution and 0.1 mJy rms sensitivity. These observations resolve the 7 mm emission in approximately the north-south direction, confirming previous results obtained with lower resolution. We use a two-layer flared disk model to interpret the observed fluxes from 7 mm to 1.3 mm together with the resolved 7 mm structure. We find that the disk radius is constrained to the range 100 to 300 AU, depending on the steepness of the disk surface density distribution. The power law index of the dust opacity coefficient, $\beta$, is constrained to be 0.5 to 0.7. Since the models indicate that the disk is optically thin at millimeter wavelengths for radii greater than 8 AU, the contribution of an optically thick region to the emission is less than 10%. This implies that high optical depth or complex disk geometry cannot be the cause of the observed shallow millimeter spectral index. Instead, the new analysis supports the earlier suggestion that dust particles in the disk have grown to sizes as large as a few centimeters. The dust in the CQ Tauri system appears to be evolved much like that in the TW Hydra system, a well-studied pre-main-sequence star of similar age and lower mass. The survival of gas-rich disks with incomplete grain evolution at such old ages deserves further investigations.

Key words: stars: planetary systems: protoplanetary disks -- stars: planetary systems: formation -- stars: formation -- stars: individual: CQ Tauri

Offprint request: L. Testi, lt@arcetri.astro.it

© ESO 2003