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instrumentation: adaptive optics
galaxies: active
galaxies: high-
redshift
quasars: emission lines
quasars: individual: 3C 294
Astrophysics - Astrophysics of Galaxies
Abstract:
Context. High redshift radio galaxies are among the most massive galaxies at their redshift, are often found at the center of protoclusters of galaxies, and are expected to evolve into the present day massive central cluster galaxies. Thus they are a useful tool to explore structure formation in the young Universe.
Aims: <ASTROBJ>3C 294</ASTROBJ> is a powerful FR II type radio galaxy at z = 1.786. Past studies have identified a clumpy structure, possibly indicative of a merging system, as well as tentative evidence that <ASTROBJ>3C 294</ASTROBJ> hosts a dual active galactic nucleus (AGN). Due to its proximity to a bright star, it has been subject to various adaptive optics imaging studies.
Methods: In order to distinguish between the various scenarios for <ASTROBJ>3C 294,</ASTROBJ> we performed deep, high-resolution adaptive optics near-infrared imaging and optical spectroscopy of <ASTROBJ>3C 294</ASTROBJ> with the Large Binocular Telescope.
Results: We resolve the <ASTROBJ>3C 294</ASTROBJ> system into three distinct components separated by a few tenths of an arcsecond on our images. One is compact, the other two are extended, and all appear to be non-stellar. The nature of each component is unclear. The two extended components could be a galaxy with an internal absorption feature, a galaxy merger, or two galaxies at different redshifts. We can now uniquely associate the radio source of <ASTROBJ>3C 294</ASTROBJ> with one of the extended components. Based on our spectroscopy, we determined a redshift of z = 1.784 ± 0.001, which is similar to the one previously cited. In addition we found a previously unreported emission line at λ6749.4 Å in our spectra. It is not clear that it originates from <ASTROBJ>3C 294</ASTROBJ>. It could be the Ne [IV] doublet λ2424/2426 Å at z = 1.783, or belong to the compact component at a redshift of z ̃ 4.56. We thus cannot unambiguously determine whether <ASTROBJ>3C 294</ASTROBJ> hosts a dual AGN or a projected pair of AGNs. The reduced AO J,H, and Ks-images and optical spectra shown in Fig. 3 and 4 are only available at the CDS via anonymous ftp to <A href="http://cdsarc.u-strasbg.fr/">http://cdsarc.u-strasbg.fr</A> (ftp://130.79.128.5) or via <A href="http://cdsarc.u-strasbg.fr/viz- bin/qcat?J/A+A/628/A28">http://cdsarc.u-strasbg.fr/viz- bin/qcat?J/A+A/628/A28</A>The LBT is an international collaboration among institutions in the United States, Italy, and Germany. LBT Corporation partners are: The University of Arizona on behalf of the Arizona Board of Regents; Istituto Nazionale di Astrofisica, Italy; LBT Beteiligungsgesellschaft, Germany, representing the Max-Planck Society, The Leibniz Institute for Astrophysics Potsdam, and Heidelberg University; The Ohio State University, and The Research Corporation, on behalf of The University of Notre Dame, University of Minnesota, and University of Virginia.
