Identifying the first generation of radio powerful AGN in the Universe with the SKA

Abstract

One of the most challenging and exciting subjects in modern astrophysics is that of galaxy formation at the epoch of reionisation. The SKA, with its revolutionary capabilities in terms of frequency range, resolution and sensitivity, will allow to explore the first Gyr of structure formation in the Universe, in particular, with the detection and study of the earliest manifestations of the AGN phenomenon. The tens of QSOs that are currently known out to the highest redshifts (z ∼ 7), many of them exhibiting powerful radio emission, imply that super-massive black holes can be grown on a very short timescale and support the existence of very high redshift (z > 7) radio loud sources -sources that have so far escaped detection. Not only would such detections be paramount to the understanding of the earliest stages of galaxy evolution, they are necessary for the direct study of neutral hydrogen in the Epoch of Reionisation, through observations of the HI 21cm forest against such background sources. In order to understand how SKA and SKA1 observations can be optimised to reveal these earliest AGN, we have examined the effect of a hot CMB on the emission of powerful and young radio galaxies. By looking at the SKA1 capabilities, in particular in terms of wavelength coverage and resolution, we determine how the effects of "CMB-muting" of a radio loud source can be observationally minimised and how to identify the best highest-redshift radio candidates. Considering different predictions for the space density of radio loud AGN at such redshifts, we identify the survey characteristics necessary to optimize the detection and identification of the very first generation of radio loud AGN in the Universe.Advancing Astrophysics with the Square Kilometre Array

Revealing the Physics and Evolution of Galaxies and Galaxy Clusters with SKA Continuum Surveys

“…For more details see Smolcic et al;Afonso et al;McAlpine et al;Makhathini et al (2015, this Volume).…”

From Nearby Low Luminosity AGN to High Redshift Radio Galaxies: Science Interests with Square Kilometre Array

“…In fact, the modelling of the X-ray background emission predicts a population of obscured AGN (Gilli et al 2007), that has not so far been detected. We can also detect the first generation radio-loud AGN at redshifts > 7 (Afonso et al 2015). These will place stringent constraints on the relationship between black hole masses, spins, accretion rates, and production of powerful jets, as the supermassive black holes would have formed around then, in the hierarchical galaxy evolution model (e.g., Li et al 2007).…”

Studies of Relativistic Jets in Active Galactic Nuclei with SKA

“…The compact radio cores of quasars with black hole masses of 10 7 M should be visible even at z > 10. Due to the dense environments in the first galaxies, Falcke et al (2004) predict that the black hole jet can potentially not break out from the galaxy, therefore leading to the formation of GHz-Peaked-Spectrum (GPS) sources (see also Taylor et al 2015;Afonso et al 2015). Early-Universe GPS sources are expected to be detected at low frequencies (100 -600 MHz) at sensitivities of 100 µJy and better.…”