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Title: MEASURING THE STELLAR MASSES OF z ∼ 7 GALAXIES WITH THE SPITZER ULTRAFAINT SURVEY PROGRAM (SURFS UP)

We present Spitzer/IRAC observations of nine z'-band dropouts highly magnified (2 ≲ μ ≲ 12) by the Bullet Cluster. We combine archival imaging with our Exploratory program (SURFS UP), which results in a total integration time of ∼30 hr per Infrared Array Camera (IRAC) band. We detect (≳ 3σ) in both IRAC bands the brightest of these high-redshift galaxies, with [3.6] = 23.80 ± 0.28 mag, [4.5] = 23.78 ± 0.25 mag, and (H – [3.6]) = 1.17 ± 0.32 mag. The remaining eight galaxies are undetected to [3.6] ∼ 26.4 mag and [4.5] ∼ 26.0 mag with stellar masses of ∼5 × 10{sup 7} M {sub ☉}. The detected galaxy has an estimated magnification of μ = 12 ± 4, which implies this galaxy has an ultraviolet luminosity of L{sub 1500}∼0.3 L{sub z=7}{sup ∗}—the lowest-luminosity individual source detected in IRAC at z ≳ 7. By modeling the broadband photometry, we estimate the galaxy has an intrinsic star formation rate (SFR) of SFR ∼ 1.3 M {sub ☉} yr{sup –1} and stellar mass of M ∼ 2.0 × 10{sup 9} M {sub ☉}, which gives a specific star formation rate of sSFR ∼ 0.7 Gyr{sup –1}. If this galaxy had sustained this SFR since z ∼more » 20, it could have formed the observed stellar mass (to within a factor of ∼2). We also discuss alternate star formation histories and argue that the exponentially increasing model is unlikely. Finally, based on the intrinsic SFR, we estimate that this galaxy has a likely [C II] flux of (f {sub [C} {sub II]}) = 1.6 mJy.« less
Authors:
; ;  [1] ;  [2] ;  [3] ; ; ; ; ;  [4] ; ;  [5] ;  [6] ; ;  [7] ; ;  [8] ;  [9]
  1. Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States)
  2. Department of Astronomy, University of Florida, 211 Bryant Space Science Center, Gainesville, FL 32611 (United States)
  3. Aix Marseille Université, CNRS, LAM (Laboratoire d'Astrophysique de Marseille) UMR 7326, F-13388 Marseille (France)
  4. University of California, One Shields Avenue, Davis, CA 95616 (United States)
  5. Kavli Institute for Particle Astrophysics and Cosmology, Stanford University, 452 Lomita Mall, Stanford, CA 94305-4085 (United States)
  6. Department of Astronomy and Astrophysics, University of Chicago, 5640 South Ellis Avenue, Chicago, IL 60637 (United States)
  7. Argelander Institute for Astronomy, University of Bonn, Auf dem Hügel 71, D-53121 Bonn (Germany)
  8. Steward Observatory, University of Arizona, 933 N. Cherry Avenue, Tucson, AZ 85721 (United States)
  9. Department of Physics, University of California, Santa Barbara, CA 93106 (United States)
Publication Date:
OSTI Identifier:
22365887
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal Letters; Journal Volume: 786; Journal Issue: 1; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; CAMERAS; COMPUTERIZED SIMULATION; GALACTIC EVOLUTION; GALAXIES; LUMINOSITY; MASS; PHOTOMETRY; RED SHIFT; STARS; ULTRAVIOLET RADIATION