Extragalactic Peaked-Spectrum Radio Sources at Low-Frequencies are Young Radio Galaxies

Abstract

We present a sample of 373 peaked-spectrum (PS) sources with spectral peaks around 150MHz, selected using a subset of two LOFAR all-sky surveys, the LOFAR Two Meter Sky Survey and the LOFAR LBA Sky Survey. These surveys are the most sensitive low-frequency widefield surveys to date, allowing us to select low-luminosity PS sources. Our sample increases the number of known PS sources in our survey area by a factor 50. The 5GHz luminosity distribution of our PS sample shows we sample the lowest luminosity PS sources to-date by nearly an order of magnitude. Since high-frequency PS sources and compact steep-spectrum sources are hypothesised to be the precursors to large radio galaxies, we investigate whether this is also the case for our sample of low-frequency PS sources. Using optical line emission criteria, we find that our PS sources are predominately high-excitation radio galaxies instead of low-excitation radio galaxies, corresponding to a quickly evolving population. We compute the radio source counts of our PS sample, and find they are scaled down by a factor of $\sim$40 compared to a general sample of radio-loud active galactic nuclei (AGN). This implies that the lifetimes of PS sources are 40 times shorter than large scale radio galaxies, if their luminosity functions are identical. To investigate this, we compute the first radio luminosity function for a homogeneously-selected PS sample. We find that for 144MHz luminosities $\gtrsim 10^{25}$W Hz${}^{-1}$, the PS luminosity function has the same shape as an unresolved radio-loud AGN population but shifted down by a factor of $\sim$10. We interpret this as strong evidence that these high-luminosity PS sources evolve into large-scale radio-loud AGN. For local, low-luminosity PS sources, there is a surplus of PS sources, which we hypothesise to be the addition of frustrated PS sources that do not evolve into large-scale AGN.

21 pages, accepted in Astronomy & Astrophysics

References in corpus (23)

• Array Programming with NumPy
• The Host Galaxies and Classification of Active Galactic Nuclei
• The Co-Evolution of Galaxies and Supermassive Black Holes: Insights from Surveys of the Contemporary Universe
• The LOFAR Two-metre Sky Survey -- V. Second data release
• Hot and cold gas accretion and feedback in radio-loud active galaxies
• The Very Large Array Low-frequency Sky Survey Redux (VLSSr)
• Compact steep-spectrum and peaked-spectrum radio sources
• The Dynamic Evolution of Young Extragalactic Radio Sources
• The Rapid ASKAP Continuum Survey Paper II: First Stokes I Source Catalogue Data Release
• Extragalactic Peaked-Spectrum Radio Sources at Low Frequencies
• Luminosity function, sizes and FR dichotomy of radio-loud AGN
• The properties of extragalactic radio sources selected at 20 GHz
• Relativistic jet feedback II: Relationship to gigahertz peak spectrum and compact steep spectrum radio galaxies
• The LOFAR LBA Sky Survey I. survey description and preliminary data release
• All-purpose, all-sky photometric redshifts for the Legacy Imaging Surveys Data Release 8
• GPS radio sources: new optical observations and an updated master list
• LOFAR-Boötes: Properties of high- and low-excitation radio galaxies at $0.5<z<2.0$
• Integrated Radio Continuum Spectra of Galaxies
• Cosmic evolution of low-excitation radio galaxies in the LOFAR Two-meter Sky Survey Deep Fields
• Extremely deep 150 MHz source counts from the LoTSS Deep Fields
• Interplanetary Scintillation studies with the Murchison Wide-field Array II: Properties of sub-arcsecond compact sources at low radio frequencies
• The LOFAR Two-metre Sky Survey Deep fields: A new analysis of low-frequency radio luminosity as a star-formation tracer in the Lockman Hole region
• Optical Properties of Peaked Spectrum Radio Sources

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