HST Grism Confirmation of 16 Structures at 1.4 < z < 2.8 from the Clusters Around Radio-Loud AGN (CARLA) Survey

Creators: Noirot, Gaël; Stern, Daniel; Mei, Simona; Wylezalek, Dominika; Cooke, Elizabeth A.; de Breuck, Carlos; Galametz, Audrey; Hatch, Nina A.; Vernet, Joël; Brodwin, Mark; Eisenhardt, Peter; Gonzalez, Anthony H.; Jarvis, Matt; Rettura, Alessandro; Seymour, Nick; Stanford, S. A.

Abstract

We report spectroscopic results from our 40-orbit Hubble Space Telescope slitless grism spectroscopy program observing the 20 densest Clusters Around Radio-Loud AGN (CARLA) candidate galaxy clusters at 1.4 < z < 2.8. These candidate rich structures, among the richest and most distant known, were identified on the basis of [3.6]–[4.5] color from a 408 hr multi-cycle Spitzer program targeting 420 distant radio-loud AGN. We report the spectroscopic confirmation of 16 distant structures at 1.4 < z < 2.8 associated with the targeted powerful high-redshift radio-loud AGN. We also report the serendipitous discovery and spectroscopic confirmation of seven additional structures at 0.87 < z < 2.12 not associated with the targeted radio-loud AGN. We find that 10^(10)–10^(11)M ⊙ member galaxies of our confirmed CARLA structures form significantly fewer stars than their field counterparts at all redshifts within 1.4 ≤ z ≤ 2. We also observe higher star-forming activity in the structure cores up to z = 2, finding similar trends as cluster surveys at slightly lower redshifts (1.0 < z < 1.5). By design, our efficient strategy of obtaining just two grism orbits per field only obtains spectroscopic confirmation of emission line galaxies. Deeper spectroscopy will be required to study the population of evolved, massive galaxies in these (forming) clusters. Lacking multi-band coverage of the fields, we adopt a very conservative approach of calling all confirmations "structures," although we note that a number of features are consistent with some of them being bona fide galaxy clusters. Together this survey represents a unique and large homogenous sample of spectroscopically confirmed structures at high redshifts, potentially more than doubling the census of confirmed, massive clusters at z > 1.4.

Additional Information

© 2018 The American Astronomical Society. Received 2017 June 2; revised 2018 January 26; accepted 2018 February 11; published 2018 May 21. We thank the referee for useful comments and suggestions that improved the paper. We thank Nicole Nesvadba for kindly sharing data concerning the field around TXS 2353−003. This work is based on observations made with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy Inc., under NASA contract NAS 5-26555. These observations are associated with program #GO-13740. Support for program #GO-13740 was provided by NASA through a grant from the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy Inc., under NASA contract NAS 5-26555. This work is also based in part on observations made with the Spitzer Space Telescope, which is operated by the Jet Propulsion Laboratory, California Institute of Technology, under a contract with NASA. This work is also based in part on observations made with the 200-inch Hale Telescope, Palomar Observatory, operated by the California Institute of Technology. The work of P.E. and D.S. was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with NASA. S.M. acknowledges financial support from the Institut Universitaire de France (IUF), of which she is senior member. D.W. acknowledges support by Akbari-Mack Postdoctoral Fellowship. E.A.C. acknowledges support from the ERC Advanced Investigator program DUSTYGAL 321334. N.A.H. acknowledges support from STFC through an Ernest Rutherford Fellowship. Facilities: HST (WFC3; STScI) - , Spitzer (IRAC; JPL/Caltech) - , Palomar (DBSP; Caltech). -

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