The faint source population at 15.7 GHz - I. The radio properties

Abstract

We have studied a sample of 296 faint (> 0.5 mJy) radio sources selected from an area of the Tenth Cambridge (10C) survey at 15.7 GHz in the Lockman Hole. By matching this catalogue to several lower frequency surveys (e.g. including a deep GMRT survey at 610 MHz, a WSRT survey at 1.4 GHz, NVSS, FIRST and WENSS) we have investigated the radio spectral properties of the sources in this sample; all but 30 of the 10C sources are matched to one or more of these surveys. We have found a significant increase in the proportion of flat spectrum sources at flux densities below approximately 1 mJy - the median spectral index between 15.7 GHz and 610 MHz changes from 0.75 for flux densities greater than 1.5 mJy to 0.08 for flux densities less than 0.8 mJy. This suggests that a population of faint, flat spectrum sources is emerging at flux densities below 1 mJy. The spectral index distribution of this sample of sources selected at 15.7 GHz is compared to those of two samples selected at 1.4 GHz from FIRST and NVSS. We find that there is a significant flat spectrum population present in the 10C sample which is missing from the samples selected at 1.4 GHz. The 10C sample is compared to a sample of sources selected from the SKADS Simulated Sky by Wilman et al. and we find that this simulation fails to reproduce the observed spectral index distribution and significantly underpredicts the number of sources in the faintest flux density bin. It is likely that the observed faint, flat spectrum sources are a result of the cores of FRI sources becoming dominant at high frequencies. These results highlight the importance of studying this faint, high frequency population.

arXiv commentAccepted by MNRAS

References in corpus (23)

• SWIRE: The SIRTF Wide-area InfraRed Extragalactic Survey
• A semi-empirical simulation of the extragalactic radio continuum sky for next generation radio telescopes
• Predictions for high-frequency radio surveys of extragalactic sources
• The Arcminute Microkelvin Imager
• The Deep SWIRE Field I. 20cm Continuum Radio Observations: A Crowded Sky
• The properties of extragalactic radio sources selected at 20 GHz
• High--frequency predictions for number counts and spectral properties of extragalactic radio sources. New evidences of a break at mm wavelengths in spectra of bright blazar sources
• 9C: A Survey of Radio Sources at 15 GHz with the Ryle Telescope
• A catalogue of micro-Jy radio sources in northern legacy fields
• The Australia Telescope 20GHz (AT20G) Survey: analysis of the extragalactic source sample
• The ATESP 5 GHz radio survey I. Source counts and spectral index properties of the faint radio population
• An infrared-radio simulation of the extragalactic sky: from the Square Kilometer Array to Herschel
• 10C Survey of Radio Sources at 15.7 GHz: I - Observing, mapping and source extraction
• 10C Survey of Radio Sources at 15.7 GHz: II - First Results
• The Planck-ATCA Co-eval Observations (PACO) project: the bright sample
• A 610-MHz survey of the Lockman Hole with the Giant Metrewave Radio Telescope - I. Observations, data reduction and source catalogue for the central 5 square degrees
• The Deep SWIRE Field II. 90cm Continuum Observations and 20cm-90cm Spectra
• 9C continued: a radio-source survey at 15 GHz
• Origin of the Counter-Rotating Gas in NGC 1596
• The Combined NVSS-FIRST Galaxies (CoNFIG) Sample - I. Sample Definition, Classification and Evolution
• The Planck-ATCA Coeval Observations (PACO) project: the faint sample
• Follow-up observations at 16 and 33 GHz of extragalactic sources from WMAP 3-year data: II - Flux-density variability
• Further GMRT observations of the Lockman Hole at 610 MHz

Cited by in corpus (29)

• A Quick Look at the $3$GHz Radio Sky I. Source Statistics from the Very Large Array Sky Survey
• LOFAR/H-ATLAS: A deep low-frequency survey of the Herschel-ATLAS North Galactic Pole field
• The Lockman Hole project: LOFAR observations and spectral index properties of low-frequency radio sources
• Search and modelling of remnant radio galaxies in the LOFAR Lockman Hole field
• The Lockman Hole Project: new constraints on the sub-mJy source counts from a wide-area 1.4 GHz mosaic
• A Broadband Polarization Catalog of Extragalactic Radio Sources
• Extremely deep 150 MHz source counts from the LoTSS Deep Fields
• First Detection of Thermal Radio Emission from Solar-Type Stars with the Karl G. Jansky Very Large Array
• A deep / wide 1-2 GHz snapshot survey of SDSS Stripe 82 using the Karl G. Jansky Very Large Array in a compact hybrid configuration
• Determining the core radio luminosity function of radio AGNs via copula
• A Wide-area GMRT 610~MHz survey of ELAIS N1 field
• The ATLAS 5.5 GHz Survey of the Extended Chandra Deep Field South: The Second Data Release
• The faint source population at 15.7 GHz - III. A high-frequency study of HERGs and LERGs
• The prevalence of core emission in faint radio galaxies in the SKA Simulated Skies
• Observational evidence that positive and negative AGN feedback depends on galaxy mass and jet power
• Deep 20-GHz survey of the Chandra Deep Field South and SDSS Stripe 82: source catalogue and spectral properties
• 10C continued: a deeper radio survey at 15.7 GHz
• Far beyond stacking: Fully bayesian constraints on sub-microJy radio source populations over the XMM-LSS-VIDEO field
• The faint radio source population at 15.7 GHz - II. Multi-wavelength properties
• The ATLAS 9.0 GHz Survey of the Extended Chandra Deep Field South: The Faint 9.0 GHz Radio Population
• GMRT 610-MHz observations of the faint radio source population - and what these tell us about the higher-radio-frequency sky
• The faint radio source population at 15.7 GHz -- IV. The dominance of core emission in faint radio galaxies
• A 15.5 GHz detection of the galaxy cluster minihalo in RXJ1720.1+2638
• The Lockman Hole with LOFAR - Searching for GPS and CSS sources at low frequencies
• AMI-LA Observations of the SuperCLASS Super-cluster
• The ATESP 5 GHz radio survey IV. 19, 38, and 94 GHz observations and radio spectral energy distributions
• Milli-arcsecond properties of 10C sources in the Lockman Hole
• AMI-CL J0300+2613: a Galactic anomalous-microwave-emission ring masquerading as a galaxy cluster
• ATCA detections of massive molecular gas reservoirs in dusty, high-z radio galaxies