The 6C** sample of steep-spectrum radio sources - II. Redshift distribution and the space density of high-redshift radio galaxies

Cruz, María; Jarvis, Matt J.; Rawlings, Steve; Blundell, Katherine M.

doi:10.1111/j.1365-2966.2007.11390.x

Cited by 25 publications

(32 citation statements)

References 45 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…In the subsequent decades, the redshift cutoff problem for the steep-spectrum radio sources has always been controversial (e.g. Jarvis et al 2001;Cruz et al 2007). This situation was significantly improved when Rigby et al (2011) found a clear (at > 3σ significance) decline in the number density in steep-spectrum radio sources.…”

Section: The Redshift Cutoffmentioning

confidence: 99%

A Mixture Evolution Scenario of the AGN Radio Luminosity Function. II. Do Low- and High-power Radio-loud AGNs Evolve Differently?

Yuan

Wang

Zhou

et al. 2017

ApJ

View full text Add to dashboard Cite

Following previous work, we further confirm that the cosmic evolution of steep-spectrum radio-loud AGNs (active galactic nuclei) can be reproduced by a simple combination of density evolution (DE) and luminosity evolution (LE). This mixture evolution scenario can naturally explain the luminositydependent evolution of radio-loud AGNs. Our models successfully fitted a large amount of data on radio luminosity functions (RLFs) of steep-spectrum sources and multi-frequency source counts. The modeling indicates that the DE slowly increase as (1 + z) 0.3∼1.3 out to z ∼ 0.8, and then rapidly decreases as (1 + z) −6.8∼−5.7 , while the LE rapidly increase as (1 + z) 4.8 out to a higher redshift (at least z > 3.5). We find a high-redshift decline (i.e. redshift cutoff) in the number density of steepspectrum radio sources, but we cannot conclude whether such decline is sharp or shallow. We believe that whether a redshift cutoff occurs or not depends mainly on DE, while its steepness is decided by LE, which, however, cannot be well constrained due to the lack of high-redshift samples. Most intriguingly, according to our mixture evolution scenario, there appears to be no need for different evolution for the low-and high-power radio-loud AGNs. Both types of sources experience the same combined evolution of DE and LE.

show abstract

Section: The Redshift Cutoffmentioning

confidence: 99%

A Mixture Evolution Scenario of the AGN Radio Luminosity Function. II. Do Low- and High-power Radio-loud AGNs Evolve Differently?

Yuan

Wang

Zhou

et al. 2017

ApJ

View full text Add to dashboard Cite

show abstract

“…Larger USS samples are needed to detect more distant objects as they are more rare. However, steep-spectrum selection also misses a significant fraction of HzRGs (e.g., Jarvis et al 2009) and not all USS sources are associated with HzRGs (e.g., Jarvis et al 2001;Cruz et al 2007;van Weeren et al 2009). Therefore a combination of deep radio and optical/NIR survey data will be a more powerful way of identifying HzRGs by searching for optically/NIR faint counterparts to the radio sources (e.g., Brookes et al 2006;Ker et al 2012).…”

Section: Ultra-steep Spectrum Sourcesmentioning

confidence: 99%

Lofar Low-Band Antenna Observations of the 3c 295 and Boötes Fields: Source Counts and Ultra-Steep Spectrum Sources

Weeren

Williams

Tasse

et al. 2014

ApJ

View full text Add to dashboard Cite

We present Low Frequency Array (LOFAR) Low Band observations of the Boötes and 3C 295 fields. Our images made at 34, 46, and 62 MHz reach noise levels of 12, 8, and 5 mJy beam −1 , making them the deepest images ever obtained in this frequency range. In total, we detect between 300 and 400 sources in each of these images, covering an area of 17-52 deg 2 . From the observations, we derive Euclidean-normalized differential source counts. The 62 MHz source counts agree with previous GMRT 153 MHz and Very Large Array 74 MHz differential source counts, scaling with a spectral index of −0.7. We find that a spectral index scaling of −0.5 is required to match up the LOFAR 34 MHz source counts. This result is also in agreement with source counts from the 38 MHz 8C survey, indicating that the average spectral index of radio sources flattens toward lower frequencies. We also find evidence for spectral flattening using the individual flux measurements of sources between 34 and 1400 MHz and by calculating the spectral index averaged over the source population. To select ultra-steep spectrum (α < −1.1) radio sources that could be associated with massive high-redshift radio galaxies, we compute spectral indices between 62 MHz, 153 MHz, and 1.4 GHz for sources in the Boötes field. We cross-correlate these radio sources with optical and infrared catalogs and fit the spectral energy distribution to obtain photometric redshifts. We find that most of these ultra-steep spectrum sources are located in the 0.7 z 2.5 range.

show abstract

“…The method developed in Cruz et al (2007) uses a model of the distribution of radio galaxies as a function of redshift together with the linear K – z relation to generate a Monte Carlo simulation of radio sources which populate a synthetic K – z diagram. The advantage of this method over simply applying a linear fit to the K – z relation is that it incorporates information about the scatter in this relation and is thus able to provide a measure of the uncertainty in the output redshift estimates.…”

Section: Estimating Redshiftsmentioning

confidence: 99%

The evolution of radio sources in the UKIDSS-DXS-XMM-LSS field

McAlpine

Jarvis

2011

Monthly Notices of the Royal Astronomical Society

Self Cite

View full text Add to dashboard Cite

The definitive version can be found at: http://onlinelibrary.wiley.com/ Copyright Royal Astronomical SocietyWe investigate the cosmic evolution of low-luminosity (L-1.4 GHz < 1025 W Hz-1 sr-1) radio sources in the XMM Large Scale Structure Survey (XMM-LSS) field. We match low-frequency-selected (610-MHz) radio sources in the XMM-LSS field with near-infrared K-band observations over the same field from the UKIRT Infrared Deep Sky Survey. We use both the mean V/V-max statistic and the radio luminosity function of these matched sources to quantify the evolution of the comoving space density of the low-luminosity radio sources in our sample. Our results indicate that the low-luminosity sources evolve differently from their high-luminosity counterparts out to a redshift of z similar to 0.8. The derived luminosity function is consistent with an increase in the comoving space density of low-luminosity sources by a factor of similar to 1.5 at z = 0.8. We show that the use of the K-z diagram for the radio source population, although coarser than a full photometric redshift analysis, produces consistent results with previous studies using approximately > 10 band photometry. This offers a promising method for conducting similar analyses over the whole sky with future near- and mid-infrared surveys

show abstract

The 6C** sample of steep-spectrum radio sources - II. Redshift distribution and the space density of high-redshift radio galaxies

Cited by 25 publications

References 45 publications

A Mixture Evolution Scenario of the AGN Radio Luminosity Function. II. Do Low- and High-power Radio-loud AGNs Evolve Differently?

A Mixture Evolution Scenario of the AGN Radio Luminosity Function. II. Do Low- and High-power Radio-loud AGNs Evolve Differently?

Lofar Low-Band Antenna Observations of the 3c 295 and Boötes Fields: Source Counts and Ultra-Steep Spectrum Sources

The evolution of radio sources in the UKIDSS-DXS-XMM-LSS field

Contact Info

Product

Resources

About