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Multi-Messenger observations and theory of astrophysical objects is fast becoming a critical research area in the astrophysics scientific community. In particular, point-like objects like that of BL Lac, flat spectrum radio quasars (FSRQ), and blazar candidates of uncertain type (BCU) are of distinct interest among those who look at the synchrotron, Compton, neutrino, and cosmic ray emissions sourced from compact objects. Notably, there is also much interest in the correlation between multi-frequency observations of blazars and neutrino surveys on source demographics. In this review we look at such multi-frequency and multi-physics correlations of the radio, X-ray, and $\gamma$-ray fluxes of different classes of blazars from a collection of survey catalogues. This multi-physics survey of blazars shows that there are characteristic cross-correlations in the spectra of blazars when considering their multi-frequency and multi-messenger emission. Accompanying this will be a review of cosmic ray and neutrino emissions from blazars and their characteristics., Comment: 13 pages, 4 figures (reviewed, Frontiers: Astronomy & Space Sciences, The Dynamic Universe: Realizing the Potential of Time Domain and Multimessenger Astrophysics)

In this letter, we report the discovery of the highest redshift, heavily obscured, radio-loud AGN candidate selected using JWST NIRCam/MIRI, mid-IR, sub-mm, and radio imaging in the COSMOS-Web field. Using multi-frequency radio observations and mid-IR photometry, we identify a powerful, radio-loud (RL), growing supermassive black hole (SMBH) with significant spectral steepening of the radio SED ($f_{1.28 \mathrm{GHz}} \sim 2$ mJy, $q_{24\mu m} = -1.1$, $\alpha_{1.28-3\mathrm{GHz}}=-1.2$, $\Delta \alpha = -0.4$). In conjunction with ALMA, deep ground-based observations, ancillary space-based data, and the unprecedented resolution and sensitivity of JWST, we find no evidence of AGN contribution to the UV/optical/NIR data and thus infer heavy amounts of obscuration (N$_{\mathrm{H}} > 10^{23}$ cm$^{-2}$). Using the wealth of deep UV to sub-mm photometric data, we report a singular solution photo-z of $z_\mathrm{phot}$ = 7.7$^{+0.4}_{-0.3}$ and estimate an extremely massive host-galaxy ($\log M_{\star} = 11.4 -12\,\mathrm{M}_{\odot}$) hosting a powerful, growing SMBH (L$_{\mathrm{Bol}} = 4-12 \times 10^{46}$ erg s$^{-1}$). This source represents the furthest known obscured RL AGN candidate, and its level of obscuration aligns with the most representative but observationally scarce population of AGN at these epochs., Comment: Accepted to ApJL