MEASURING THE UNDETECTABLE: PROPER MOTIONS AND PARALLAXES OF VERY FAINT SOURCES
Open accessAbstract
The near future of astrophysics involves many large solid-angle, multi-epoch, multiband imaging surveys. These surveys will, at their faint limits, have data on a large number of sources that are too faint to be detected at any individual epoch. Here, we show that it is possible to measure in multi-epoch data not only the fluxes and positions, but also the parallaxes and proper motions of sources that are too faint to be detected at any individual epoch. The method involves fitting a model of a moving point source simultaneously to all imaging, taking account of the noise and point-spread function (PSF) in each image. By this method it is possible to measure the proper motion of a point source with an uncertainty close to the minimum possible uncertainty given the information in the data, which is limited by the PSF, the distribution of observation times (epochs), and the total signal-to-noise in the combined data. We demonstrate our technique on multi-epoch Sloan Digital Sky Survey (SDSS) imaging of the SDSS Southern Stripe (SDSSSS). We show that with our new technique we can use proper motions to distinguish very red brown dwarfs from very high-redshift quasars in these SDSS data, for objects that are inaccessible to traditional techniques, and with better fidelity than by multiband imaging alone. We rediscover all 10 known brown dwarfs in our sample and present nine new candidate brown dwarfs, identified on the basis of significant proper motion.
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The quality of exposures in large campaigns remains essential to downstream tasks such as astrometric and photometric measurements and target selection.
“Despite the increase in scope and complexity of future imaging surveys, the quality of exposures in large campaigns will remain essential to downstream tasks, such as astrometric (e.g., Lang et al. 2009), and photometric (e.g., Stubbs & Tonry 2006) measurements, and target selection to facilitate follow-up studies (e.g., Myers et al. 2023).”
From A Semi-Supervised Learning Method for the Identification of Bad Exposures in Large Imaging Surveys (2026) · cites this paper as Lang et al. 2009
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A Semi-Supervised Learning Method for the Identification of Bad Exposures in Large Imaging Surveys
Luo, Y., Myers, A. D., Drlica-Wagner, A., Dematties, D., Borchani, S., Valdes, F., Dey, A., Schlegel, D., Zhou, R., & DESI Legacy Imaging Surveys Team (2026) · The Open Journal of Astrophysics · doi:10.33232/001c.158430 · Cited by 1 · see citing works
- Authors
- Lang, D., Hogg, D. W., Jester, S., & Rix, H.-W.
- Affiliations
- University of Toronto (CA)
- Max Planck Institute for Astronomy (DE)
- Corresponding author
- Hogg, David W.
- Venue
- The Astronomical Journal
- Publisher
- American Astronomical Society
- Published
- 2009-04-07
- Volume
- 137
- Issue
- 5
- Pages
- 4400-4411
- ISSN
- 0004-6256 (ISSN-L)
- 1538-3881
- OpenAlex
- W2042673349
- Cited by
- 9
- References
- 1
- Citations by year
- 2024: 1 · 2023: 2 · 2019: 1 · 2013: 1 · 2012: 1
- FWCI
- 0.67
- Type
- journal article
- Language
- en
- Open access
- bronze
- doi.org
- Locations
- The Astronomical Journal (publishedVersion)
- arXiv (Cornell University) (submittedVersion)
- Max Planck Institute for Plasma Physics (submittedVersion)
- arXiv (Cornell University)
- Funders
- National Science Foundation (0428465)
- U.S. Department of Energy
- National Aeronautics and Space Administration (NAG511669)
- Alfred P. Sloan Foundation
- Alexander von Humboldt-Stiftung
- Princeton University
- Ohio State University
- California Institute of Technology
- University of Washington
- Johns Hopkins University
- University of Pittsburgh
- Case Western Reserve University
- Drexel University
- Universität Basel
- University of Portsmouth
- New Mexico State University
- Chinese Academy of Sciences
- Max-Planck-Gesellschaft
- Science and Technology Facilities Council
- U.S. Naval Observatory
- Fermilab
- Los Alamos National Laboratory
- Topics
- Physical Sciences › Physics and Astronomy › Astronomy and Astrophysics › Stellar, planetary, and galactic studies
- Physical Sciences › Physics and Astronomy › Instrumentation › Astronomy and Astrophysical Research
- Physical Sciences › Physics and Astronomy › Astronomy and Astrophysics › Galaxies: Formation, Evolution, Phenomena
- Keywords
- proper motions, parallax, multi-epoch imaging, point spread function, brown dwarfs, high-redshift quasars, red quasars, astrometry, photometry
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