Speaker
Description
We present a multi-wavelength study of $\sim150$ Brightest Cluster Galaxies (BCGs) spanning $0.3 < z < 0.8$, tracing the evolution of AGN feedback, star formation, and environmental dependence across $\sim3.4$~Gyr. Clusters are selected via the Sunyaev-Zel'dovich (SZ) effect, enabling robust mass estimates and a redshift-independent selection function. We combine radio data from ASKAP (RACS) with DES optical imaging, WISE mid-infrared photometry, and SALT spectroscopy to derive stellar masses, star-formation rates, and Eddington-scaled accretion rates via SED fitting. About 90\% of the radio AGNs are low-excitation (LERGs) with $\lambda_{\mathrm{Edd}}\sim10^{-3}–10^{-2}$, consistent with radiatively inefficient, jet-mode feedback that maintains thermal balance in the intracluster medium. Only a small fraction show optical emission lines, indicating rare episodes of cold gas accretion or transitional high-excitation (HERG-like) phases. Radio-quiet BCGs, matched in mass and redshift, exhibit quiescent spectra, $\lambda_{\mathrm{Edd}}<10^{-4}$, and negligible star formation, consistent with fully dormant black holes. Radio-loud systems preferentially inhabit more massive clusters ($M_{500} \gtrsim 10^{14.6}\,M_\odot$), where hot-gas accretion sustains long-lived AGN activity. These results reveal a continuous sequence from quiescent to jet-dominated accretion, linking SMBH growth and feedback to both host and cluster-scale environments.
| Stream | Science or Engineering |
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