SPITZER ULTRA FAINT SURVEY PROGRAM (SURFS UP). II. IRAC-DETECTED LYMAN-BREAK GALAXIES AT 6 ≲ z ≲ 10 BEHIND STRONG-LENSING CLUSTERS

Abstract

We study the stellar population properties of the IRAC-detected 6  z  10 galaxy candidates from the Spitzer UltRa Faint SUrvey Program. Using the Lyman Break selection technique, we find a total of 17 galaxy candidates at 6  z  10 from Hubble Space Telescope images (including the full-depth images from the Hubble Frontier Fields program for MACS 1149 and MACS 0717) that have detections at signal-to-noise ratios  3 in at least one of the IRAC 3.6 and 4.5 μm channels. According to the best mass models available for the surveyed galaxy clusters, these IRAC-detected galaxy candidates are magnified by factors of ∼1.2-5.5. Due to the magnification of the foreground galaxy clusters, the rest-frame UV absolute magnitudes M 1600 are between −21.2 and −18.9 mag, while their intrinsic stellar masses are between 2×10 8 M e and 2.9×10 9 M e . We identify two Lyα emitters in our sample from the Keck DEIMOS spectra, one at z Lyα =6.76 (in RXJ 1347) and one at z Lyα =6.32 (in MACS 0454). We find that 4 out of 17 z  6 galaxy candidates are favored by z  1 solutions when IRAC fluxes are included in photometric redshift fitting. We also show that IRAC [3.6]-[4.5] color, when combined with photometric redshift, can be used to identify galaxies which likely have strong nebular emission lines or obscured active galactic nucleus contributions within certain redshift windows.

ALMA [C ii] 158 μm Detection of a Redshift 7 Lensed Galaxy behind RX J1347.1−1145*

“…This is in contrast to our nominal SED-fitting results from Huang et al (2016) using 0.2 Z e templates from Bruzual & Charlot (2003) and assuming Calzetti et al (2000) dust attenuation curve, which imply a dust-obscured SFR SED ≈14 M e yr −1 , significantly higher than the FIR upper limit. Re-fitting the SED assuming a constant star formation history and a steeper SMC dust attenuation curve (Pei 1992), motivated by recent ALMA results (e.g., Capak et al 2015), leads to a smaller dust-obscured SFR SED =5.3 M e yr −1 , closer to but still higher than the limit derived from the non-detection of FIR continuum.…”

“…We have detected [C II] emission in RX J1347:1216 with Lyα emission first reported by Huang et al (2016) and Schmidt et al (2016). The [C II] line is detected at 5σ (peak line flux S line =1.25±0.25 mJy using 30 -km s 1 resolution; Figure 1).…”

“…The nominal UV slope β UV measured from the observed (i.e., not fitted) F125W to F160W magnitudes (see Huang et al 2016 6.5 7 and young age of 13 Myr (with a maximally old stellar population not contributing >10% of the stellar mass). We list the SEDfitting results using the SMC curve in Table 1 and show the bestfit template in Figure 4.…”

“…We have spectroscopically confirmed its redshift using Keck DEIMOS data (Huang et al 2016) and HST grism data from GLASS (Treu et al 2015;Schmidt et al 2016). In Huang et al (2016), we also measured its integrated stellar properties using deep Spitzer SURFSUP data (Spitzer UltRa Faint SUrvey Program; Bradač et al 2014). Our magnification model shows that the massive foreground galaxy cluster RX J1347.1−1145 magnifies RX J1347:1216 by a factor fof 5.0±0.3.…”

The Frontier Fields: Survey Design and Initial Results

“…These stellar masses are similar to those expected for the progenitors of the Large and Small Magellanic Clouds (Boylan- Kolchin et al 2015). Independently, the deep Spitzer IRAC imaging from the SURFS-UP Spitzer imaging program combined with the Frontier Fields HST/Spitzer IRAC observations have detected 17 Lyman break galaxies at 6<z<10 in MACSJ0717.5+3745 and MACSJ1149.5+2223, probing intrinsic stellar masses down to  M 2 10 8 (Bradac̆et al 2014;Huang et al 2016).…”