Radio and Submm Studies of Active Galactic Nuclei

Abstract

The radio dichotomy in the observed quasar population (only 10%-15% of all quasars are radio-loud) in the Universe is still an unsolved problem in extragalactic astronomy. Using the spectroscopic quasar catalog from the Sloan Digital Sky Survey, we show in this study, that the radio-loud fraction (RLF) of quasars increases with the full-width-half-maxima (FWHM) of the Hβ and MgII emission lines. We then construct a sample of high broad line (HBL; FWHM greater than 15, 000 km s−1) quasars and study their properties in a comprehensive manner. Our study show that the bolometric and optical continuum luminosity of the radio loud (RL) quasars are higher while there is no significant difference in other fundamental properties between the RL and radio-quiet (RQ) populations in our sample. By comparing them with the non-HBL Hβ broad emission line quasars, we find that the HBL sources have the lowest Eddington ratios in addition to having a very high RLF. This is consistent with the theories of jet formation, in which jets are launched from low Eddington ratio systems. We then investigate the host galaxy properties of our HBL quasars by modeling their spectral energy distribution using the X-CIGALE module. Our preliminary studies show that among the host galaxy properties, stellar mass, the luminosity absorbed by the dust, star-formation rate, and stellar population age are higher for our radio loud quasars while e-folding time is higher for our radio quiet quasars. We note that our sample size is small to robustly predict the physical implications of this result. To probe the energetic outflows from quasars we model the thermal Sunyaev-Zeldovich (SZ) effect from quasar feedback. We use the cosmological simulation SIMBA which includes different prescriptions for quasar feedback. From these theoretical simulations, we perform mock observations of the Atacama Large Millimeter Array to characterize the feasibility of direct detection of the quasar SZ signal. Our results show that for all the systems we get an enhancement of the SZ signal, when there is radiative feedback, while the signal gets suppressed when the jet mode of feedback is introduced in the simulations.