RELICS: A Candidate z ∼ 10 Galaxy Strongly Lensed into a Spatially Resolved Arc

Brett Salmon, Dan Coe, Larry Bradley, Marusa Bradač, Victoria Strait, Rachel Paterno-Mahler, Kuang Han Huang, Pascal A. Oesch, Adi Zitrin, Ana Acebron, Nathália Cibirka, Shotaro Kikuchihara, Masamune Oguri, Gabriel B. Brammer, Keren Sharon, Michele Trenti, Roberto J. Avila, Sara Ogaz, Felipe Andrade-Santos, Daniela CarrascoCatherine Cerny, William Dawson, Brenda L. Frye, Austin Hoag, Christine Jones, Ramesh Mainali, Masami Ouchi, Steven A. Rodney, Daniel Stark, Keiichi Umetsu

Research output: Contribution to journalArticlepeer-review

57 Scopus citations


The most distant galaxies known are at z ∼ 10-11, observed 400-500 Myr after the Big Bang. The few z ∼ 10-11 candidates discovered to date have been exceptionally small, barely resolved, if at all, by the Hubble Space Telescope. Here we present the discovery of SPT0615-JD1, a fortuitous z ∼ 10 (z phot = ) galaxy candidate stretched into an arc over ∼2.″5 by the effects of strong gravitational lensing. Discovered in the Reionization Lensing Cluster Survey (RELICS) Hubble Treasury program and companion S-RELICS Spitzer program, this candidate has a lensed H-band magnitude of 24.6 ± 0.1 AB mag. With a magnification of μ ∼ 4-7 estimated from our lens models, the delensed intrinsic magnitude is 26.7 ± 0.1 AB mag, and the half-light radius is r e < 0.8 kpc, both consistent with other z > 9 candidates. The inferred stellar mass () and star formation rate () indicate that this candidate is a typical star-forming galaxy on the z > 6 SFR-M relation. We note that three independent lens models predict two counter images, at least one of which should be of a similar magnitude to the arc, but these counter images are not yet detected. Counter images would not be expected if the arc were at lower redshift. The relatively large physical size could be due to a merger or accretion event, while the unprecedented lensed size of this z ∼ 10 candidate offers the potential for ALMA and the James Webb Space Telescope to study the geometric and kinematic properties of a galaxy observed 500 Myr after the Big Bang.

Original languageEnglish
Article numberL22
JournalAstrophysical Journal Letters
Issue number1
StatePublished - 1 Sep 2018

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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