Volume 619, November 2018
|Number of page(s)||16|
|Published online||19 November 2018|
CANDELSz7: a large spectroscopic survey of CANDELS galaxies in the reionization epoch
INAF, Osservatorio Astronomico di Roma, via Frascati 33, 00078 Monteporzio Catone, Italy
2 INAF, Osservatorio Astronomico di Bologna, via Gobetti 93/3, 40129 Bologna, Italy
3 Observatoire de Genève, Université de Genève, 51 Ch. des Maillettes, 1290 Versoix, Switzerland
4 Department of Physics, University of California, 1 Shields Ave, Davis, CA 95616, USA
5 School of Physics & Astronomy,The University of Nottingham, University Park, Nottingham NG7 2RD, UK
6 INAF-Osservatorio Astronomico di Trieste, via Tiepolo 11, 34143 Trieste, Italy
7 NOAO, 959 N. Cherry Ave, Tucson, AZ 85719, USA
8 Department of Astronomy, The University of Texas at Austin, Austin, TX 78712, USA
9 Núcleo de Astronomía, Facultad de Ingeniería y Ciencias, Universidad Diego Portales, Av. Ejército 441, Santiago, Chile
10 Space Telescope Science Institute, 3700 San Martin Drive, Baltimore MD 21218, USA
11 Kavli Institute for Cosmology, University of Cambridge, Madingley Road, Cambridge CB3 0HA, UK
12 School of Earth & Space Exploration, Arizona State University, Tempe, AZ 85287, USA
Accepted: 3 August 2018
We present the results of CANDELSz7, a European Southern Observatory (ESO) Large Program aimed at spectroscopically confirming a homogeneous sample of z ≃ 6 and z ≃ 7 star forming galaxies. The candidates were selected in the GOODS-South, UDS, and COSMOS fields using the official CANDELS catalogs based on H160-band detections. Standard color criteria, which were tailored depending on the ancillary multi-wavelength data available for each field, were applied to select more than 160 candidate galaxies at z ≃ 6 and z ≃ 7. Deep, medium-resolution FORS2 spectroscopic observations were then conducted with integration times ranging from 12 to 20 h to reach a Lyα flux limit of approximately 1 − 3 × 10−18 erg s−1 cm−2 at 3σ. We could determine a spectroscopic redshift for about 40% of the galaxies, mainly through the detection of a single emission line that we interpret as Lyα emission, or for some of the brightest objects (H160 ≤ 25.5) from the presence of faint continuum and a sharp drop that we interpret as a Lyα break. In this paper we present the redshifts and main properties of 65 newly confirmed high-redshift galaxies. Adding previous proprietary and archival data we assemble a sample of ≃260 galaxies that we use to explore the evolution of the Lyα fraction in Lyman break galaxies and the change in the shape of the emission line between z ∼ 6 and z ∼ 7. We also discuss the accuracy of the CANDELS photometric redshifts in this redshift range.
Key words: galaxies: high-redshift / galaxies: distances and redshifts / dark ages / reionization / first stars
© ESO 2018
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