PI: Joan Najita, NOAO, email@example.com
Address: 950 N. Cherry Ave., Tucson, AZ 85719, USA
CoI: James Muzerolle, Steward Observatory
CoI: Stephen Strom, NOAO
Title: Residual Disk Gas and Terrestrial Planet Formation
Abstract: The persistence of small amounts of gas (~ 1 M_\rm Earth) in the terrestrial planet region of disks is expected to have a significant impact on the likelihood of forming habitable Earth-like planets, i.e., Earth-mass planets at ~ 1 AU distances with low eccentricities. Despite its importance in determining the outcome of terrestrial planet formation, the presence and longevity of such residual disk gas is largely unexplored. We therefore propose to quantify the residual gas content in planet-forming disks using stellar accretion rates, the most sensitive available probe of residual gas. We will focus on determining the demographics of sources in the 10^-10-10^-9\Msunperyr range (equivalently gas column densities of 1-10\gpersqcm at 1 AU) at ages < 10 Myr. Systems with residual gas at the upper end of this range (\lesssim 10\gpersqcm) have gas column densities low enough that they may be experiencing the onset of terrestrial planet formation. Objects with residual gas below this range (\ll 1\gpersqcm; i.e., the upper limits in our survey) have so little gas at this young age that they will never form terrestrial planets on circular orbits. Objects with intermediate amounts of residual gas may be in the process of circularizing the orbits of terrestrial planets. The statistics that we will obtain on the range of gas masses present at AU distances and ages < 10 Myr will provide a unique constraint on the likelihood of producing Earth-like planets.
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