Low-power Radio Galaxies in the Distant Universe: A search for FRI at 1<z<2 in the COSMOS field

Abstract

We present a search for FRI radio galaxies between 1 < z < 2 in the COSMOS field. In absence of spectroscopic redshift measurements, the selection method is based on multiple steps which make use of both radio and optical constraints. The basic assumptions are that 1) the break in radio power between low-power FRIs and the more powerful FRIIs does not change with redshift, and 2) that the photometric properties of the host galaxies of low power radio galaxies in the distant universe are similar to those of FRIIs in the same redshift bin, as is the case for nearby radio galaxies. We describe the results of our search, which yields 37 low-power radio galaxy candidates that are possibly FRIs. We show that a large fraction of these low-luminosity radio galaxies display a compact radio morphology, that does not correspond to the FRI morphological classification. Furthermore, our objects are apparently associated with galaxies that show clear signs of interactions, at odds with the typical behavior observed in low-z FRI hosts. The compact radio morphology might imply that we are observing intrinsically small and possibly young objects, that will eventually evolve into the giant FRIs we observe in the local universe. One of the objects appears as point-like in HST images. This might belong to a population of FRI-QSOs, which however would represent a tiny minority of the overall population of high-z FRIs. As for the local FRIs, a large fraction of our objects are likely to be associated with groups or clusters, making them "beacons" for high redshift clusters of galaxies. Our search for candidate high-z FRIs we present in this paper constitutes a pilot study for objects to be observed with future high-resolution and high-sensitivity instruments (shortened)

44 pages, 11 figures, version accepted for publication in ApJ

References in corpus (13)

• The Cosmic Evolution Survey (COSMOS) -- Overview
• The First Release COSMOS Optical and Near-IR Data and Catalog
• The COSMOS Survey: Hubble Space Telescope / Advanced Camera for Surveys (HST/ACS) Observations and Data Processing
• The Spitzer Legacy Survey of the HST-ACS 2 sq. deg. COSMOS Field: survey strategy and first analysis
• The Cosmic Evolution Survey (COSMOS): Subaru Observations of the HST COSMOS Field
• The VLA-COSMOS Survey: II. Source Catalog of the Large Project
• The Relation Between Quasar and Merging Galaxy Luminosity Functions and the Merger-Induced Star Formation Rate of the Universe
• Photometric Redshifts of Galaxies in COSMOS
• New Insights on the QSO Radio-Loud/Radio-Quiet Dichotomy: SDSS Spectra in the Context of the 4D Eigenvector1 Parameter Space
• Radio galaxies in the 2SLAQ Luminous Red Galaxy Survey: I. The evolution of low-power radio galaxies to z~0.7
• The prevalence of FRI radio quasars
• A sample of mJy radio sources at 1.4 GHz in the Lynx and Hercules fields - II. Cosmic evolution of the space density of FRI radio sources
• Bulges and disks in the Host Galaxies of low redshift 3CR Sources: a near-IR view of their radial brightness profile

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