(HSTHST) grism confirmation of two z ∼ 2 structures from the clusters around radio-loud AGN (CARLA) survey
- Université Paris-Diderot Paris VII, Université de Paris Sorbonne Cité (PSC), F-75205 Paris Cedex 13 (France)
- European Southern Observatory, Karl-Schwarzschildstrasse 2, D-85748 Garching (Germany)
- Johns Hopkins University, Zanvyl Krieger School of Arts and Sciences, 3400 N. Charles Street, Baltimore, MD 21218 (United States)
- Max-Planck-Institut für extraterrestrische Physik, Giessenbachstrasse 1, D-85748 Garching (Germany)
- Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA 91109 (United States)
- Department of Physics, University of Missouri, 5110 Rockhill Road, Kansas City, MO 64110 (United States)
- School of Physics and Astronomy, University of Nottingham, University Park, Nottingham NG7 2RD (United Kingdom)
- Department of Astronomy, University of Florida, Gainesville, FL 32611-2055 (United States)
- Infrared Processing and Analysis Center, California Institute of Technology, KS 314-6, Pasadena, CA 91125 (United States)
Using Hubble Space Telescope slitless grism data, we report the spectroscopic confirmation of two distant structures at z∼2 associated with powerful high-redshift radio-loud active galactic nuclei (AGNs). These rich structures, likely (forming) clusters, are among the most distant structures currently known, and were identified on the basis of Spitzer/IRAC [3.6]–[4.5] color. We spectroscopically confirm nine members in the field of MRC 2036−254, comprising eight star-forming galaxies and the targeted radio galaxy. The median redshift is z = 2.000. We spectroscopically confirm 10 members in the field of B3 0756+406, comprising 8 star-forming galaxies and 2 AGNs, including the targeted radio-loud quasar. The median redshift is z = 1.986. All confirmed members are within 500 kpc (1 arcmin) of the targeted AGNs. We derive median (mean) star-formation rates of ∼35 M{sub ⊙} yr{sup −1} (∼50 M{sub ⊙} yr{sup −1}) for the confirmed star-forming members of both structures based on their [O iii]λ5007 luminosities, and estimate average galaxy stellar masses ≲1×10{sup 11} M{sub ⊙} based on mid-infrared fluxes and spectral energy distribution modeling. Most of our confirmed members are located above the star-forming main sequence toward starburst galaxies, consistent with clusters at these early epochs being the sites of significant levels of star formation. The structure around MRC 2036−254 shows an overdensity of IRAC-selected candidate galaxy cluster members consistent with being quiescent galaxies, while the structure around B3 0756+406 shows field values, albeit with many lower limits to colors that could allow an overdensity of faint red quiescent galaxies. The structure around MRC 2036−254 shows a red sequence of passive galaxy candidates.
- OSTI ID:
- 22868584
- Journal Information:
- Astrophysical Journal, Vol. 830, Issue 2; Other Information: Country of input: International Atomic Energy Agency (IAEA); ISSN 0004-637X
- Country of Publication:
- United States
- Language:
- English
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