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          Institute: MPI für Astronomie     Collection: Publikationen_mpia     Display Documents



ID: 730422.0, MPI für Astronomie / Publikationen_mpia
Estimating distances from parallaxes
Authors:Bailer-Jones, C. A. L.
Date of Publication (YYYY-MM-DD):2015
Title of Journal:Publications of the Astronomical Society of the Pacific
Volume:127
Issue / Number:956
Start Page:994
End Page:1009
Audience:Not Specified
Abstract / Description:Astrometric surveys such as Gaia and LSST will measure parallaxes for hundreds of millions of stars. Yet they will not measure a single distance. Rather, a distance must be estimated from a parallax. In this didactic article, I show that doing this is not trivial once the fractional parallax error is larger than about 20%, which will be the case for about 80% of stars in the Gaia catalog. Estimating distances is an inference problem in which the use of prior assumptions is unavoidable. I investigate the properties and performance of various priors and examine their implications. A supposed uninformative uniform prior in distance is shown to give very poor distance estimates (large bias and variance). Any prior with a sharp cut-off at some distance has similar problems. The choice of prior depends on the information one has available—and is willing to use—concerning, e.g., the survey and the Galaxy. I demonstrate that a simple prior which decreases asymptotically to zero at infinite distance has good performance, accommodates nonpositive parallaxes, and does not require a bias correction.
External Publication Status:published
Document Type:Article
Communicated by:N. N.
Affiliations:MPI für Astronomie
Identifiers:ISSN:0004-6280 %R 10.1086/683116
URL:http://cdsads.u-strasbg.fr/abs/2015PASP..127..994B
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