Browsing by Author "Whittam, Imogen H"

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    Radio galaxies in simba: a mightee comparison
    (University of the Western Cape, 2024) Whittam, Imogen H; Thomas, Nicole L; Hale, Catherine L
    We present a qualitative comparison between the host and black hole properties of radio galaxies in the MeerKAT International GHz Tiered Extragalactic Exploration (MIGHTEE) survey with the radio galaxy population in the SIMBA suite of cosmological hydrodynamical simulations. The MIGHTEE data include a ∼1 deg2 pointing of the COSMOS field observed at 1.28 GHz with the MeerKAT radio telescope and cross-matched with multiwavelength counterparts to provide classifications of high- and low-excitation radio galaxies (HERGs and LERGs) along with their corresponding host properties. We compare the properties of the MIGHTEE HERGs and LERGs with that predicted by the SIMBA simulations where HERGs and LERGs are defined as radio galaxies dominated by cold or hot mode accretion, respectively. We consider stellar masses M∗, star formation rates SFR, AGN bolometric luminosity Lbol , and Eddington fraction fEdd , as a function of 1.4 GHz radio luminosity and redshift. In both MIGHTEE and SIMBA, the properties of HERGs and LERGs are similar across all properties apart from SFRs due to differences in host cold gas content in SIMBA. We predict a population of HERGs with low fEdd in SIMBA that are confirmed in the MIGHTEE observations and tied to the faint population at low z. The predictions from SIMBA with the MIGHTEE observations describe a regime where our understanding of the radio galaxy dichotomy breaks down, challenging our understanding of the role of AGN accretion and feedback in the faint population of radio galaxies
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    Spectral age distribution for radio-loud active galaxies in the XMM-LSS field
    (Monthly Notices of the Royal Astronomical Society, 2023) Jarvis, Matt J; Whittam, Imogen H; Pinjarkar, Siddhant; Hardcastle, Martin J
    Jets of energetic particles, as seen in FR type-I and FR type-II sources, ejected from the centre of radio-loud AGN affect the sources surrounding the intracluster medium/intergalactic medium. Placing constraints on the age of such sources is important in order to measure the jet powers and determine the effects on feedback. To evaluate the age of these sources using spectral age models, we require high-resolution multiwavelength data. The new sensitive and high-resolution MIGHTEE survey of the XMM-LSS field, along with data from the Low Frequency Array (LOFAR) and the Giant Metrewave Radio Telescope (GMRT) provide data taken at different frequencies with similar resolution, which enables us to determine the spectral age distribution for radio-loud AGN in the survey field. In this study, we present a sample of 28 radio galaxies with their best-fitting spectral age distribution analysed using the Jaffe–Perola (JP) model on a pixel-by-pixel basis.