ALMA [C II] 158 Μm Detection of a Redshift 7 Lensed Galaxy Behind RX J1347.1−1145

The Astrophysical Journal Letters, 836:L2 (5pp), 2017 February 10 doi:10.3847/2041-8213/836/1/L2 © 2017. The American Astronomical Society. All rights reserved. * ALMA [C II] 158 μm Detection of a Redshift 7 Lensed Galaxy behind RX J1347.1−1145 Maruša Bradač1, Diego Garcia-Appadoo2,3, Kuang-Han Huang1, Livia Vallini4,5,6, Emily Quinn Finney1, Austin Hoag1, Brian C. Lemaux1, Kasper Borello Schmidt7, Tommaso Treu8,18, Chris Carilli9,10, Mark Dijkstra11, Andrea Ferrara12,13, Adriano Fontana14, Tucker Jones1, Russell Ryan15, Jeff Wagg16, and Anthony H. Gonzalez17 1 Department of Physics, University of California, Davis, CA 95616, USA; [email protected] 2 Joint ALMA Observatory, Alonso de Córdova 3107, Vitacura, Santiago, Chile 3 European Southern Observatory, Alonso de Córdova 3107, Vitacura, Santiago, Chile 4 Nordita, KTH Royal Institute of Technology and Stockholm University, Roslagstullsbacken 23, SE-106 91 Stockholm, Sweden 5 Dipartimento di Fisica e Astronomia, viale Berti Pichat 6, I-40127 Bologna, Italy 6 INAF, Osservatorio Astronomico di Bologna, via Ranzani 1, I-40127 Bologna, Italy 7 Leibniz-Institut für Astrophysik Potsdam (AIP), An der Sternwarte 16, D-14482 Potsdam, Germany 8 Department of Physics and Astronomy, UCLA, Los Angeles, CA, 90095-1547, USA 9 National Radio Astronomy Observatory, P. O. Box 0, Socorro, NM 87801, USA 10 Cavendish Laboratory, 19 J. J. Thomson Avenue, Cambridge CB3 0HE, UK 11 Institute of Theoretical Astrophysics, University of Oslo, Postboks 1029 Blindern, NO-0315 Oslo, Norway 12 Scuola Normale Superiore, Piazza dei Cavalieri 7, I-56126 Pisa, Italy 13 Kavli IPMU (WPI), Todai Institutes for Advanced Study, The University of Tokyo, Japan 14 INAF—Osservatorio Astronomico di Roma, Via Frascati 33-00040, Monte Porzio Catone, I-00040 Rome, Italy 15 Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218, USA 16 Square Kilometre Array Organisation, Lower Withington, Cheshire, UK 17 Department of Astronomy, University of Florida, 211 Bryant Space Science Center, Gainesville, FL 32611, USA Received 2016 October 6; revised 2017 January 8; accepted 2017 January 10; published 2017 February 3 Abstract We present the results of ALMA spectroscopic follow-up of a z=6.766 Lyα emitting galaxy behind the cluster RX J1347.1−1145. We report the detection of [C II] 158 μm line fully consistent with the Lyα redshift and with the peak of the optical emission. Given the magnification of μ=5.0±0.3, the intrinsic (corrected for lensing) [ ] L +0.2 7 ∼ z∼ luminosity of the C II line is [C II] =´1.4-0.3 10 L, roughly 5 times fainter than other detections of 7 L z∼ galaxies. The result indicates that low [C II] in 7 galaxies compared to the local counterparts might be caused / ( +140 -1) α by their low metallicities and or feedback. The small velocity offset Dv = 20-40 km s between the Ly and [C II] line is unusual, and may be indicative of ionizing photons escaping. Key words: dark ages, reionization, first stars – galaxies: clusters: individual (RX J1347.1−1145) – galaxies: high-redshift – gravitational lensing: strong 1. Introduction connection of [C II] to star formation rate (SFR; e.g., De Looze et al. 2014), although for z∼7 such a relation has not been The epoch of reionization, during which the universe became [ ] transparent to UV radiation, is still poorly understood. Faint studied in detail yet due to limited sample size. C II is also a galaxies are likely responsible for this transformation; however very useful tracer of the kinematics of distant galaxies. fi ( However, even with ALMA, detections at z∼7 remain sparse this connection is far from con rmed e.g., Madau & Haardt ( 2015; Robertson et al. 2015). Despite great progress in finding see Maiolino et al. 2015; Knudsen et al. 2017; Pentericci et al. Hubble Space Telescope (HST 2016 for current detections of [C II] and Inoue et al. 2016 for an candidates with ; e.g., Bouwens [ ] μ ) et al. 2015) beyond z7, galaxies remain enshrouded in O III 88 m detection . In particular, despite deep observa- α ( ) mystery, at least from a spectroscopic point of view. Spectro- tions, the extremely bright Ly Emitter LAE Himiko was not [ ] ( scopic confirmations remain extremely difficult, as the most detected in C II Ouchi et al. 2013; Ota et al. 2014; Schaerer ) prominent spectral feature in the optical/near-IR wavelengths, et al. 2015 . the Lyα line, can be erased by neutral gas both in and From the theoretical side, the issue of non-detections has ( ) ( ) surrounding galaxies. been studied, e.g., by Vallini et al. 2015 , Olsen et al. 2015 , ( ) ( ) An alternative way of measuring redshifts for early galaxies and Narayanan & Krumholz 2016 . Both Vallini et al. 2015 ( ) z is to use sensitive radio/far-infrared (FIR) telescopes to and Olsen et al. 2015 conclude that in high- galaxies the [ ] observe the [C II] 158 μm line. It is among the strongest lines C II emission arises predominately from photodissociation z∼ fi [ ] in star-forming galaxies at radio through FIR wavelengths (e.g., regions. Furthermore, at 7 the de cit in C II -emission at a Carilli & Walter 2013) and it is therefore being actively given SFR has been ascribed to either negative stellar feedback pursued as a new way to measure redshifts at z6. disrupting molecular clouds near the star-forming regions and/ Furthermore, for lower-redshift galaxies there exists a or low gas metallicities. Narayanan & Krumholz (2016) point out that the cloud surface density is also a key parameter, with * These observations are based on the following ALMA data: ADS/JAO. the [C II] luminosity decreasing with decreasing size of the ALMA#2015.1.00091.S. They are also associated with programs Spitzer [C II] emitting region in high surface density clouds. Other # HST # 90009, 60034, 00083, 50610, 03550, 40593, and GO10492, factors that influence total [C II] emission include (i) the GO11591, GO12104, and GO13459. Furthermore based on multi-year KECK programs. relative abundances of the various gas phases composing the 18 Packard Fellow. interstellar medium ISM (ionized, neutral, and molecular), (ii) 1 The Astrophysical Journal Letters, 836:L2 (5pp), 2017 February 10 Bradač et al. the hardness of the radiation field, and (iii) the temperature and density of the emitting gas. In this Letter, we report on ALMA observations of * RX J1347:1216, a normal (L<L ) star-forming galaxy with α +0.0030 fi Ly emission at zLya = 6.7659-0.0005. It was rst reported by Bradley et al. (2014) and Smit et al. (2014) as a photometrically selected z∼7 galaxy from the HST and Spitzer CLASH data (Cluster Lensing And Supernova survey with Hubble; Postman et al. 2012). 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. Taking into account magnification, the ’ +0.07 galaxy s intrinsic rest-frame UV luminosity is 0.18-0.05L* ( z∼ assuming characteristic magnitude at 7ofMUV* = ) -20.87 0.26 from Bouwens et al. 2015 , making [ ] HST fi Figure 1. C II emission overlaid on the color composite RGB image RX J1347:1216 the rst galaxy detected with ALMA at (optical-F110W-F160W). The contours are spaced linearly between 1 and 5σ z∼7 having a luminosity characteristic of the majority of (solid lines); negative contours (−1,−2σ) are given as dashed lines. A 1″×1″ galaxies at z∼7. zoom-in is shown in the inset, and the beam is given in the bottom left. Throughout the Letter, we assume a ΛCDM concordance cosmology with Ωm=0.27, ΩΛ=0.73, and Hubble constant −1 −1 H0=73 km s Mpc . Coordinates are given for the epoch J2000.0, and magnitudes are in the AB system. 2. Observations and Data Reduction We observed RX J1347:1216 with ALMA on 2016 July 21 in Band 6 with 38 12 m antennae on a configuration of 15–700 m baselines. The precipitable water vapor stayed stable at ∼0.8 mm during the observations. The total time on-source was 74 minutes, with the phases centered at the HST position of the source. Out of the four spectral windows, SPW0 was set to Frequency Division Mode and its center tuned to the [C II] 158 μm rest-frame frequency of 1900.54 GHz and a sky-frequency of 244.85 GHz, in the Upper Side Band, yielding a velocity resolution of 9.5 km s-1 after a spectral averaging factor of 16 was applied to reduce the data rate. The other three spectral windows were used for continuum in Time Figure 2. Extracted spectrum (flux S as a function of frequency ν) of the [C II] Division Mode (31.25 MHz spectral resolution) at lower emission. The red line denotes the best-fit Gaussian (with parameter listed in frequencies. We used J1337−1257 for bandpass and absolute Table 1) and the gray dashed line and region correspond to the Lyα redshift flux scale calibrators and J1354−1041 for a phase calibrator. and uncertainty. The data reduction followed the standard procedures in the Common Astronomy Software Applications package. The data Due to gravitational lensing, we are able to measure [C II] cube was cleaned using Briggs weighting and ROBUST=0.5. luminosity in RX J1347:1216 that is intrinsically ∼5 times The FWHM beam size of the final image is 0 58×0 41 at a fainter than other such measurements at z∼7 to date (and position angle of 288°.

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