Gas Flow Across Gaps in Protoplanetary Disks.pdf

a r X i v : a s t r o - p h / 0 5 1 2 2 9 2 v 1 1 2 D e c 2 0 0 5 1 December 2005 Gas Flow Across Gaps in Protoplanetary Disks1 Steve H. Lubow Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218, USA lubow@stsci.edu and Gennaro D’Angelo School of Physics, University of Exeter, Stocker Road, Exeter EX4 4QL, United Kingdom gennaro@astro.ex.ac.uk ABSTRACT We analyze the gas accretion flow through a planet-produced gap in a protoplanetary disk. We adopt the alpha disk model and ignore effects of planetary migration. We develop a semi-analytic, one-dimensional model that accounts for the effects of the planet as a mass sink and also carry out two-dimensional hydrodynamical simulations of a planet embedded in a disk. The predictions of the mass flow rate through the gap based on the semi-analytic model generally agree with the hydrodynamical simulations at the 25% level. Through these models, we are able to explore steady state disk structures and over large spatial ranges. The presence of an accreting ～ 1MJ planet significantly lowers the density of the disk within a region of several times the planet’s orbital radius. The mass flow rate across the gap (and onto the central star) is typically 10% to 25% of the mass accretion rate outside the orbit of the planet, for planet-to-star mass ratios that range from 5× 10?5 to 1× 10?3. Subject headings: accretion, accretion discs — hydrodynamics — planets and satellites: general 1. Introduction The presence of a ～ 1MJ planet influences the structure of a circumstellar disk. The most obvious effect is the opening of a tidally produced gap (Lin Papaloizou 1993). Recent stud- ies of young stars such as CoKu Tau/4 (D’Alessio et al. 2005), TW Hya (Calvet et al. 2002), KH 15D (Herbst et al. 2002), HR 4796A (Schneider 1999), and HD 141569A (Clampin et al. 2003) suggest the presence of inner holes in circumstellar disks. One possible mechanism for producing such a hole is the tidal barrier created by a pl