MEASURING THE STELLAR MASSES OF z ∼ 7 GALAXIES WITH THE SPITZER ULTRAFAINT SURVEY PROGRAM (SURFS UP)
- Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States)
- Department of Astronomy, University of Florida, 211 Bryant Space Science Center, Gainesville, FL 32611 (United States)
- Aix Marseille Université, CNRS, LAM (Laboratoire d'Astrophysique de Marseille) UMR 7326, F-13388 Marseille (France)
- University of California, One Shields Avenue, Davis, CA 95616 (United States)
- Kavli Institute for Particle Astrophysics and Cosmology, Stanford University, 452 Lomita Mall, Stanford, CA 94305-4085 (United States)
- Department of Astronomy and Astrophysics, University of Chicago, 5640 South Ellis Avenue, Chicago, IL 60637 (United States)
- Argelander Institute for Astronomy, University of Bonn, Auf dem Hügel 71, D-53121 Bonn (Germany)
- Steward Observatory, University of Arizona, 933 N. Cherry Avenue, Tucson, AZ 85721 (United States)
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 ∼ 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.
- OSTI ID:
- 22365887
- Journal Information:
- Astrophysical Journal Letters, Vol. 786, Issue 1; Other Information: Country of input: International Atomic Energy Agency (IAEA); ISSN 2041-8205
- Country of Publication:
- United States
- Language:
- English
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