The nuclear activity and central structure of the elliptical galaxy NGC
  5322
  We have analysed a new high-resolution e-MERLIN 1.5 GHz radio continuum map
together with $HST$ and SDSS imaging of NGC 5322, an elliptical galaxy hosting
radio jets, aiming to understand the galaxy's central structure and its
connection to the nuclear activity. We decomposed the composite $HST$ + SDSS
surface brightness profile of the galaxy into an inner stellar disc, a
spheroid, and an outer stellar halo. Past works showed that this embedded disc
counter-rotates rapidly with respect to the spheroid. The $HST$ images reveal
an edge-on nuclear dust disc across the centre, aligned along the major-axis of
the galaxy and nearly perpendicular to the radio jets. After careful masking of
this dust disc, we find a central stellar mass deficit $M_{\rm def}$ in the
spheroid, scoured by SMBH binaries with final mass $M_{\rm BH}$ such that
$M_{\rm def}/M_{\rm BH} \sim 1.3 - 3.4$. We propose a three-phase formation
scenario for NGC 5322 where a few ($2-7$) "dry" major mergers involving SMBHs
built the spheroid with a depleted core. The cannibalism of a gas-rich
satellite subsequently creates the faint counter-rotating disc and funnels
gaseous material directly onto the AGN, powering the radio core with a
brightness temperature of $T_{\rm B,core} \sim 4.5 \times 10^{7}$ K and the
low-power radio jets ($P_{\rm jets}\sim 7.04 \times 10^{20}$ W Hz$^{-1}$) which
extend $\sim 1.6$ kpc. The outer halo can later grow via minor mergers and the
accretion of tidal debris. The low-luminosity AGN/jet-driven feedback may have
quenched the late-time nuclear star formation promptly, which could otherwise
have replenished the depleted core.
