We present a database of well determined orbital parameters of exoplanets. This database comprises spectroscopic orbital elements measured for 427 planets orbiting 363 stars from radial velocity and transit measurements as reported in the literature.
We have also compiled fundamental transit parameters, stellar parameters, and the method used for the planets discovery. This Exoplanet Orbit Database includes all planets with robust, well measured orbital parameters reported in peer-reviewed articles. The database is available in a searchable, filterable, and sortable form on the Web at http://exoplanets.org through the Exoplanets Data Explorer Table, and the data can be plotted and explored through the Exoplanets Data Explorer Plotter. We use the Data Explorer to generate publication-ready plots giving three examples of the signatures of exoplanet migration and dynamical evolution: We illustrate the character of the apparent correlation between mass and period in exoplanet orbits, the selection different biases between radial velocity and transit surveys, and that the multiplanet systems show a distinct semi-major axis distribution from apparently singleton systems.
We construct merger trees from the largest database of dark matter haloes to date provided by the Millennium simulation to quantify the merger rates of haloes over a broad range of descendant halo mass (1e12 < M0 < 1e15 Msun), progenitor mass ratio (
1e-3 < xi < 1), and redshift (0 < z < 6). We find the mean merger rate per halo, B/n, to have very simple dependence on M0, xi, and z, and propose a universal fitting form for B/n that is accurate to 10-20%. Overall, B/n depends very weakly on the halo mass (proportional to M0^0.08) and scales as a power law in the progenitor mass ratio (proportional to xi^-2) for minor mergers (xi < 0.1) with a mild upturn for major mergers. As a function of time, we find the merger rate per Gyr to evolve as (1+z)^n with n=2-2.3, while the rate per unit redshift is nearly independent of z. Several tests are performed to assess how our merger rates are affected by, e.g. the time interval between Millennium outputs, binary vs multiple progenitor mergers, and mass conservation and diffuse accretion during mergers. In particular, we find halo fragmentations to be a general issue in merger tree construction from N-body simulations and compare two methods for handling these events. We compare our results with predictions of two analytical models for halo mergers based on the Extended Press-Schechter (EPS) model and the coagulation theory. We find the EPS model to overpredict the major merger rates and underpredict the minor merger rates by up to a factor of a few.
