VLA imaging of the disk surrounding the nearby young star TW Hydrae

The TW Hydrae system is perhaps the closest analog to the early solar nebul a. We have used the Very Large Array to image TW Hya at wavelengths of 7 mm and 3.6 cm with resolutions of 0." 1 (similar to 5 AU) and 1." 10 (similar to 50 AU), respectively. The 7 mm emission is extended and appears dominat ed by a dusty disk of radius greater than 50 AU surrounding the star. The 3 .6 cm emission is unresolved and likely arises from an ionized wind or gyro synchrotron activity. The dust spectrum and spatially resolved 7 mm images of the TW Hya disk are fitted by a simple model with temperature and surfac e density described by radial power laws, T(r) proportional to r(-0.5) and Sigma(r) proportional to r(-1). These properties are consistent with an irr adiated gaseous accretion disk of mass similar to 0.03 M-circle dot with an accretion rate similar to 10(-8) M-circle dot yr(-1) and viscosity paramet er alpha = 0.01. The estimates of mass and mass accretion rates are uncerta in since the gas-to-dust ratio in the TW Hya disk may have evolved from the standard interstellar value.