Spectral ageing in the era of big data: integrated vs resolved models

Abstract

Continuous injection models of spectral ageing have long been used to determine the age of radio galaxies from their integrated spectrum; however, many questions about their reliability remain unanswered. With various large area surveys imminent (e.g. LOFAR, MeerKAT, MWA) and planning for the next generation of radio interferometer well underway (e.g. ngVLA, SKA), investigations of radio galaxy physics are set to shift away from studies of individual sources to the population as a whole. Determining if and how integrated models of spectral ageing can be applied in the era of big data is therefore crucial. In this paper, I compare classical integrated models of spectral ageing to recent well resolved studies that use modern analysis techniques on small spatial scales to determine their robustness and validity as a source selection method. I find that integrated models are unable to recover key parameters and, even when known a priori, provide a poor, frequency dependent description of a source's spectrum. I show a disparity of up to a factor of 6 in age between the integrated and resolved methods but suggest, even with these inconsistencies, such models still provide a potential method of candidate selection in the search for remnant radio galaxies and in providing a cleaner selection of high redshift radio galaxies in $z-\alpha$ selected samples.

8 pages, 1 figure, 3 tables. Accepted for publication in MNRAS

References in corpus (4)

• The LOFAR Two-metre Sky Survey - I. Survey Description and Preliminary Data Release
• The VLA Low-frequency Sky Survey
• The Lockman Hole project: LOFAR observations and spectral index properties of low-frequency radio sources
• LOFAR reveals the giant: a low-frequency radio continuum study of the outflow in the nearby FR I radio galaxy 3C 31

Cited by in corpus (16)

• Search and modelling of remnant radio galaxies in the LOFAR Lockman Hole field
• RAiSE III: 3C radio AGN energetics and composition
• Remnant radio-loud AGN in the Herschel-ATLAS field
• Constraining the AGN duty cycle in the cool-core cluster MS 0735.6+7421 with LOFAR data
• Investigating the spectral age problem with powerful radio galaxies
• Remnant Radio Galaxies Discovered in a Multi-frequency Survey
• The Dynamics and Energetics of Remnant and Restarting RLAGN
• LOFAR MSSS: The Scaling Relation between AGN Cavity Power and Radio Luminosity at Low Radio Frequencies
• Studying the late evolution of a radio-loud AGN in a galaxy group with LOFAR
• High-resolution international LOFAR observations of 4C~43.15 -- Spectral ages and injection indices in a high-z radio galaxy
• Search for hybrid morphology radio galaxies from FIRST survey at 1400 MHz
• RAiSERed: radio continuum redshifts for lobed AGNs
• Seeing the forest and the trees: a radio investigation of the ULIRG Mrk 273
• The structure of the giant radio fossil in the Ophiuchus galaxy cluster
• Relighting the fire in Hickson Compact Group (HCG) 15: magnetised fossil plasma revealed by the SKA Pathfinders & Precursors
• Characteristics of remnant radio galaxies detected in the deep radio continuum observations from the SKA pathfinders