The Signature of the Ice Line and Modest Type I Migration in the Observed Exoplanet MassSemimajor Axis Distribution
Abstract
Existing exoplanet radial velocity surveys are complete in the planetary masssemimajor axis (M_{p} a) plane over the range 0.1 AU <a< 2.0 AU where M_{p} gsim 100 M _{⊕}. We marginalize over mass in this complete domain of parameter space, and demonstrate that the observed a distribution is inconsistent with models of planet formation that use the full Type I migration rate derived from a linear theory and that do not include the effect of the ice line on the disk surface density profile. However, the efficiency of Type I migration can be suppressed by both nonlinear feedback and the barriers introduced by local maxima in the disk pressure distribution, and we confirm that the synthesized M_{p} a distribution is compatible with the observed data if we account for both retention of protoplanetary embryos near the ice line and an orderofmagnitude reduction in the efficiency of Type I migration. The validity of these assumptions can be checked because they also predict a population of shortperiod rocky planets with a range of masses comparable to that of the Earth as well as a "desert" in the M_{p} a distribution centered around M_{p} ~ 30  50 M _{⊕} and a < 1 AU. We show that the expected "desert" in the M_{p} a plane will be discernible by a radial velocity survey with 1 m s^{1} precision and n ~ 700 radial velocity observations of program stars.
 Publication:

The Astrophysical Journal
 Pub Date:
 February 2009
 DOI:
 10.1088/0004637X/691/2/1322
 arXiv:
 arXiv:0809.1651
 Bibcode:
 2009ApJ...691.1322S
 Keywords:

 planetary systems;
 planetary systems: formation;
 planetary systems: protoplanetary disks;
 Astrophysics
 EPrint:
 15 pages, 6 figures, and 1 table in preprint format