The radio source population at high frequency: follow-up of the 15-GHz 9C survey
We have carried out extensive radio and optical follow‐up of 176 sources from the 15‐GHz 9th Cambridge survey. Optical identifications have been found for 155 of the radio sources; optical images are given with radio maps overlaid. The continuum radio spectrum of each source spanning the frequency range 1.4–43 GHz is also given. Two flux‐limited samples are defined, one containing 124 sources complete to 25 mJy and one of 70 sources complete to 60 mJy. Between one‐fifth and one‐quarter of sources from these flux‐limited samples display convex radio spectra, rising between 1.4 and 4.8 GHz. These rising‐spectrum sources make up a much larger fraction of the radio source population at this high selection frequency than in lower frequency surveys. We find that by using non‐simultaneous survey flux density measurements at 1.4 and 15 GHz to remove steep‐spectrum objects, the efficiency of selecting objects with spectra rising between 1.4 and 4.8 GHz (as seen in simultaneous measurements) can be raised to 49 per cent without compromising the completeness of the rising‐spectrum sample.
Additional Information© 2004 RAS. Accepted 2004 July 8. Received 2004 July 6. Published: 21 October 2004. RCB is supported by a PPARC studentship. GC acknowledges support from PPARC observational rolling grants PPA/G/O/2003/00123 and PPA/G/O/2001/00575. The National Geographic Society–Palomar Observatory Sky Atlas (POSS‐I) was made by the California Institute of Technology with grants from the National Geographic Society. The Second Palomar Observatory Sky Survey (POSS‐II) was made by the California Institute of Technology with funds from the National Science Foundation, the National Aeronautics and Space Administration, the National Geographic Society, the Sloan Foundation, the Samuel Oschin Foundation and the Eastman Kodak Corporation. The Digitized Sky Survey was produced at the Space Telescope Science Institute under US Government grant NAG W‐2166. The images of these surveys are based on photographic data obtained using the Oschin Schmidt Telescope on Palomar Mountain and the UK Schmidt Telescope. The plates were processed into the present compressed digital form with the permission of these institutions.
Published - 354-2-485.pdf
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