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Joint Survey Processing. II. Stellar Proper Motions in the COSMOS Field from Hubble Space Telescope ACS and Subaru Telescope HSC Observations

Fajardo-Acosta, Sergio B. and Faisst, Andreas and Grillmair, Carl J. and Chary, Ranga-Ram and Paladini, Roberta and Rusholme, Ben and Stickley, Nathaniel (2022) Joint Survey Processing. II. Stellar Proper Motions in the COSMOS Field from Hubble Space Telescope ACS and Subaru Telescope HSC Observations. Astrophysical Journal, 930 (1). Art. No. 71. ISSN 0004-637X. doi:10.3847/1538-4357/ac5a4f.

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We analyze stellar proper motions in the COSMOS field to assess the presence of bulk motions. At bright magnitudes (G-band 18.5–20.76 AB), we use the proper motions of 1010 stars in the Gaia DR2 catalog. At the faint end, we compute proper motions of 11,519 pointlike objects at i-band magnitudes 19–25 AB using Hubble ACS and Subaru HSC data, which span two epochs about 11 yr apart. In order to measure these proper motions with unprecedented accuracy at faint magnitudes, we developed a foundational set of astrometric tools that will be required for joint survey processing of data from the next generation of optical/infrared surveys. The astrometric grids of Hubble ACS and Subaru HSC mosaics were corrected at the catalog level using proper motion–propagated and parallax-corrected Gaia DR2 sources. These astrometric corrections were verified using compact extragalactic sources. Upon comparison of our measured proper motions with Gaia DR2, we estimate the uncertainties in our measurements to be ∼2–3 mas yr⁻¹ axis⁻¹, down to 25.5 AB mag. We correct proper motions for the mean motion of the Sun, and we find that late-type main-sequence stars predominantly in the thin disk in the COSMOS field have space velocities mainly toward the Galactic center. We detect candidate high-velocity (≥220 km s⁻¹) stars, six of them at ∼0.4–6 kpc, from the Gaia sample, and five of them at ∼20 kpc, from the faint star HSC and ACS sample. The sources from the faint star sample may be candidate halo members of the Sangarius stream.

Item Type:Article
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URLURL TypeDescription Paper ItemLSST website
Fajardo-Acosta, Sergio B.0000-0001-9309-0102
Faisst, Andreas0000-0002-9382-9832
Grillmair, Carl J.0000-0003-4072-169X
Chary, Ranga-Ram0000-0001-7583-0621
Paladini, Roberta0000-0002-5158-243X
Rusholme, Ben0000-0001-7648-4142
Stickley, Nathaniel0000-0003-0987-5738
Additional Information:© 2022. The Author(s). Published by the American Astronomical Society. Original content from this work may be used under the terms of the Creative Commons Attribution 4.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI. Received 2021 November 20; revised 2022 February 28; accepted 2022 March 1; published 2022 May 4. We thank Dr. Davy Kirkpatrick for very insightful discussions and the anonymous referee for very helpful suggestions. The Hyper Suprime-Cam (HSC) collaboration includes the astronomical communities of Japan and Taiwan and Princeton University. The HSC instrumentation and software were developed by the National Astronomical Observatory of Japan (NAOJ), the Kavli Institute for the Physics and Mathematics of the Universe (Kavli IPMU), the University of Tokyo, the High Energy Accelerator Research Organization (KEK), the Academia Sinica Institute for Astronomy and Astrophysics in Taiwan (ASIAA), and Princeton University. Funding was contributed by the FIRST program from the Japanese Cabinet Office, the Ministry of Education, Culture, Sports, Science and Technology (MEXT), the Japan Society for the Promotion of Science (JSPS), the Japan Science and Technology Agency (JST), the Toray Science Foundation, NAOJ, Kavli IPMU, KEK, ASIAA, and Princeton University. This paper makes use of software developed for the Large Synoptic Survey Telescope. We thank the LSST Project for making their code available as free software at Based in part on data collected at the Subaru Telescope and retrieved from the HSC data archive system, which is operated by the Subaru Telescope and the Astronomy Data Center at the National Astronomical Observatory of Japan. This work has made use of data from the European Space Agency (ESA) mission Gaia (, processed by the Gaia Data Processing and Analysis Consortium (DPAC; Funding for the DPAC has been provided by national institutions, in particular the institutions participating in the Gaia Multilateral Agreement. This research used resources of the National Energy Research Scientific Computing Center, a DOE Office of Science User Facility supported by the Office of Science of the US Department of Energy under contract No. DE-AC02-05CH11231. This research is partially funded by the Joint Survey Processing effort at IPAC/Caltech through NASA grant NNN12AA01C. Facilities: HST(ACS) - Hubble Space Telescope satellite, Subaru(HSC) - , Gaia - . Software: SExtractor (Bertin & Arnouts 1996).
Group:Infrared Processing and Analysis Center (IPAC)
Funding AgencyGrant Number
Hyper Suprime-Cam (HSC) collaborationUNSPECIFIED
Gaia Multilateral AgreementUNSPECIFIED
Department of Energy (DOE)DE-AC02-05CH11231
Subject Keywords:Galaxy structure; Galaxy stellar halos; Proper motions; Astrometry; Catalogs; Stellar streams
Issue or Number:1
Classification Code:Unified Astronomy Thesaurus concepts: Galaxy structure (622); Galaxy stellar halos (598); Proper motions (1295); Astrometry (80); Catalogs (205); Stellar streams (2166)
Record Number:CaltechAUTHORS:20220512-561157000
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Official Citation:Sergio B. Fajardo-Acosta et al 2022 ApJ 930 71
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:114704
Deposited By: George Porter
Deposited On:13 May 2022 17:23
Last Modified:13 May 2022 17:23

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