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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

Roberts-Borsani, G. W. and Bouwens, R. J. and Oesch, P. A. and Labbe, I. and Smit, R. and Illingworth, G. D. and van Dokkum, P. G. and Holden, B. and Gonzalez, V. and Stefanon, M. and Holwerda, B. and Wilkins, S. (2016) 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. Astrophysical Journal, 823 (2). Art. No. 143. ISSN 0004-637X. http://resolver.caltech.edu/CaltechAUTHORS:20170628-142851441

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Abstract

We identify four unusually bright (H ${}_{160,{AB}}$ < 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 gsim 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 gsim 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 z spec = 7.4770 ± 0.0008. All three have H160-band magnitudes of ~25 mag and are ~0.5 mag more luminous (M 1600 ~ −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


Item Type:Article
Related URLs:
URLURL TypeDescription
http://dx.doi.org/10.3847/0004-637X/823/2/143DOIArticle
Additional Information: © 2016. The American Astronomical Society.
Group:SPLASH, COSMOS
Record Number:CaltechAUTHORS:20170628-142851441
Persistent URL:http://resolver.caltech.edu/CaltechAUTHORS:20170628-142851441
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:78669
Collection:CaltechAUTHORS
Deposited By: Joy Painter
Deposited On:28 Jun 2017 21:43
Last Modified:28 Jun 2017 21:43

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