z  7 galaxies with red Spitzer/IRAC [3.6]–[4.5] colors in the full CANDELS data set : the brightest-known galaxies AT z ∼ 7–9 and a probable spectroscopic confirmation at z = 7.48.

Authors

G. W. Roberts-Borsani, Leiden University
R. J. Bouwens, Leiden University
P. A. Oesch, Yale University
I. Labbe, Leiden University
R. Smit, Leiden University
G. D. Illingworth, University of California, Santa Cruz
P. G. van Dokkum, Yale University
B. Holden, University of California, Santa Cruz
V. Gonzalez, University of California, Riverside
M. Stefanon, Leiden University
Benne W. Holwerda, University of Louisville
S. M. Wilkins, University of Sussex

Document Type

Article

Publication Date

6-2016

Department

Physics and Astronomy

Abstract

We identify four unusually bright (H160,AB < 25.5) galaxies from Hubble Space Telescope (HST) and Spitzer CANDELS data with probable redshifts z ∼ 7–9. These identifications include the brightest-known galaxies to date at z  7.5. As Y-band observations are not available over the full CANDELS program to perform a standard Lyman-break selection of z > 7 galaxies, we employ an alternate strategy using deep Spitzer/IRAC data. We identify z ∼ 7.1–9.1 galaxies by selecting z  6 galaxies from the HST CANDELS data that show quite red IRAC [3.6]−[4.5] colors, indicating strong [O III]+Hβ lines in the 4.5 μm band. This selection strategy was validated using a modest sample for which we have deep Y-band coverage, and subsequently used to select the brightest z 7 sources. Applying the IRAC criteria to all HST-selected optical dropout galaxies over the full ∼900 arcmin2 of the CANDELS survey revealed four unusually bright z ∼ 7.1, 7.6, 7.9, and 8.6 candidates. The median [3.6]−[4.5] color of our selected z ∼ 7.1–9.1 sample is consistent with rest-frame [O III]+Hβ EWs of ∼1500 Å in the [4.5] band. Keck/MOSFIRE spectroscopy has been independently reported for two of our selected sources, showing Lyα at redshifts of 7.7302 ± 0.0006 and - + 8.683 0.004 0.001, respectively. We present similar Keck/MOSFIRE spectroscopy for a third selected galaxy with a probable 4.7σ Lyα line at zspec = 7.4770 ± 0.0008. All three have H160-band magnitudes of ∼25 mag and are ∼0.5 mag more luminous (M1600 ∼ −22.0) than any previously discovered z ∼ 8 galaxy, with important implications for the UV luminosity function (LF). Our three brightest and highest redshift z > 7 galaxies all lie within the CANDELS-EGS field, providing a dramatic illustration of the potential impact of field-to-field variance

Comments

© 2016. The American Astronomical Society. All rights reserved.

https://doi.org/10.3847/0004-637X/823/2/143

Original Publication Information

Roberts-Borsani, G. W., et al. "z  Galaxies with Red Spitzer/IRAC [3.6]–[4.5] Colors in the Full CANDELS Data Set: The Brightest-Known Galaxies at z ~ 7-9 and a Probable Spectroscopic Confirmation at z = 7.48." 2016. The Astrophysical Journal 823(2): 17 pp.

ThinkIR Citation

Roberts-Borsani, G. W.; Bouwens, R. J.; Oesch, P. A.; Labbe, I.; Smit, R.; Illingworth, G. D.; van Dokkum, P. G.; Holden, B.; Gonzalez, V.; Stefanon, M.; Holwerda, Benne W.; and Wilkins, S. M., "z  7 galaxies with red Spitzer/IRAC [3.6]–[4.5] colors in the full CANDELS data set : the brightest-known galaxies AT z ∼ 7–9 and a probable spectroscopic confirmation at z = 7.48." (2016). Faculty Scholarship. 165.
https://ir.library.louisville.edu/faculty/165

DOI

10.3847/0004-637X/823/2/143