Exoplanet population inference and the abundance of earth analogs from noisy, incomplete catalogs

Daniel Foreman-Mackey, David W. Hogg, Timothy D. Morton

    Research output: Contribution to journalArticle

    Abstract

    No true extrasolar Earth analog is known. Hundreds of planets have been found around Sun-like stars that are either Earth-sized but on shorter periods, or else on year-long orbits but somewhat larger. Under strong assumptions, exoplanet catalogs have been used to make an extrapolated estimate of the rate at which Sun-like stars host Earth analogs. These studies are complicated by the fact that every catalog is censored by non-trivial selection effects and detection efficiencies, and every property (period, radius, etc.) is measured noisily. Here we present a general hierarchical probabilistic framework for making justified inferences about the population of exoplanets, taking into account survey completeness and, for the first time, observational uncertainties. We are able to make fewer assumptions about the distribution than previous studies; we only require that the occurrence rate density be a smooth function of period and radius (employing a Gaussian process). By applying our method to synthetic catalogs, we demonstrate that it produces more accurate estimates of the whole population than standard procedures based on weighting by inverse detection efficiency. We apply the method to an existing catalog of small planet candidates around G dwarf stars. We confirm a previous result that the radius distribution changes slope near Earth's radius. We find that the rate density of Earth analogs is about 0.02 (per star per natural logarithmic bin in period and radius) with large uncertainty. This number is much smaller than previous estimates made with the same data but stronger assumptions.

    Original languageEnglish (US)
    Article number64
    JournalAstrophysical Journal
    Volume795
    Issue number1
    DOIs
    StatePublished - Nov 1 2014

    Fingerprint

    Earth analogs
    extrasolar planets
    inference
    catalogs
    radii
    stars
    planets
    sun
    planet
    estimates
    G stars
    dwarf stars
    completeness
    occurrences
    slopes
    orbits
    rate

    Keywords

    • catalogs
    • methods: data analysis
    • methods: statistical
    • planetary systems
    • stars: statistics Online-only material: color figures, supplemental data

    ASJC Scopus subject areas

    • Space and Planetary Science
    • Astronomy and Astrophysics

    Cite this

    Exoplanet population inference and the abundance of earth analogs from noisy, incomplete catalogs. / Foreman-Mackey, Daniel; Hogg, David W.; Morton, Timothy D.

    In: Astrophysical Journal, Vol. 795, No. 1, 64, 01.11.2014.

    Research output: Contribution to journalArticle

    Foreman-Mackey, Daniel ; Hogg, David W. ; Morton, Timothy D. / Exoplanet population inference and the abundance of earth analogs from noisy, incomplete catalogs. In: Astrophysical Journal. 2014 ; Vol. 795, No. 1.
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