Ultra Steep Spectrum (USS) radio sources have been successfully used to select powerful radio sources at high redshifts (z > 2). Typically restricted to large-sky surveys and relatively bright radio flux densities, it has gradually become possible to extend the USS search to sub-mJy levels, thanks to the recent appearance of sensitive low-frequency radio facilities. Here we present a first detailed analysis of the nature of the faintest USS sources. By using GMRT and VLA radio observations of the Lockman Hole (LH) at 610MHz and 1.4GHz, a sample of 58 micro-Jansky USS sources is assembled. Deep infrared data at 3.6 and 4.5μm from the Spitzer Extragalactic Representative Volume Survey (SERVS) is used to reliably identify counterparts for 48 (83%) of these sources, showing an average magnitude of [3.6]=19.7 mag(AB). Spectroscopic redshifts for 14 USS sources, together with photometric redshift estimates, improved by the use of the deep SERVS data, for a further 19 objects, show redshifts ranging from z =0.1 to z=2.8, peaking at z∼0.6 and tailing off at high redshifts. © Springer-Verlag Berlin Heidelberg 2012.
CITATION STYLE
Bizzocchi, L., Afonso, J., Ibar, E., Grossi, M., Simpson, C., Chapman, S., … Zeimann, G. (2012). Ultra steep spectrum radio sources in the Lockman Hole: SERVS identifications and redshift distribution at the faintest radio fluxes. In Astrophysics and Space Science Proceedings (pp. 97–100). Kluwer Academic Publishers. https://doi.org/10.1007/978-3-642-22795-0_10
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