Speaker
Description
The origin and impact of radio emission in radio-quiet quasars has remained ambiguous for decades, largely due to limitations of all-sky, low-resolution surveys. Leveraging new, sensitive sub-kpc–to–kpc scale radio imaging from the Quasar Feedback Survey (QFeedS), we are now resolving the structures that drive feedback at the heart of massive galaxies. Using e-MERLIN, we mapped radio emission on 10s–100s pc scales for 42 luminous (L[O III] > 10^42 erg s⁻¹; LAGN > 10^45 erg s⁻¹), mostly radio-quiet quasars at z < 0.2, detecting 37/42 and revealing a diverse range of compact radio morphologies, including weak unresolved cores, hotspots, sub-kpc jets, and irregular diffuse structures frequently missed by VLA-only imaging. Combining morphology and brightness-temperature diagnostics, 76% of these quasars host radio-AGN, significantly higher than the ∼57% identified at kpc-scales alone. Complementary new sub-arcsecond VLA imaging (1.4 and 6 GHz) of 29 lower-radio-power quasars (L1.4GHz = 10^22.6–10^23.45 W Hz⁻¹) further reveals widespread AGN-driven synchrotron activity: ∼31% show resolved structures on 0.1–10 kpc scales, ∼90% exhibit steep spectra (α ≲ −1), and ≥40% display AGN signatures inconsistent with star formation alone. Together, these ∼71 quasars span nearly five orders of magnitude in radio power. We establish that: i)compact jets and shocks are common well inside the “radio-quiet’’ regime; ii)these targets map abroad continuum of radio properties in optically-selected quasars; and iii)connect low-luminosity FR0-like AGN with the more extended radio populations, and show the diversity of radio output among radiatively-efficient quasars across several orders of magnitude in 𝐿1.4 GHz.
I will show how these new high-resolution observations, tracing feedback from ∼10 pc to ∼10 kpc scales, are transforming our understanding of quasar-driven galaxy evolution, and why sensitive, multi-scale radio imaging is essential for uncovering the true prevalence and impact of AGN feedback in the low-power radio regime.
| Stream | Science or Engineering |
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