The MBHBM⋆ Project – II. Molecular gas kinematics in the lenticular galaxy NGC 3593 reveal a supermassive black hole

As part of the Measuring Black Holes in Below Milky Way-mass (M$^\star$) galaxies (MBHBM$^\star$) Project, we present a dynamical measurement supermassive black hole (SMBH) mass nearby lenticular galaxy NGC 3593, using cold molecular gas $^{12}$CO(2-1) emission observed at an angular resolution $\approx0''.3$ ($\approx10$ pc) with Atacama Large Millimeter/submillimeter Array (ALMA). Our ALMA observations reveal circumnuclear disc (CND) elongated along major axis and rotating around SMBH. Using modelling, kinematics allow us to infer SMBH $M_{\rm BH}=2.40_{-1.05}^{+1.87}\times10^6$ M$_\odot$ (only statistical uncertainties $3\sigma$ level). We also detect massive core (CMC) CMC}=(5.4\pm1.2)\times10^6$ effective (half-mass) radius $r_{\rm CMC,e}=11.2\pm2.8$ pc, co-spatial nuclear star cluster (NSC) NSC}=(1.67\pm0.48)\times10^7$ NSC,e}=5.0\pm1.0$~pc (or $0''.15\pm0''.03$). The profiles CMC NSC are well described by S\'{e}rsic functions indices $1-1.4$. BH}$ NSC}$ estimates for 3593 agree recently compiled BH}$-$M_{\rm scaling relation. Although uncertainty is twice inferred BH}$, rapid central rise rotation velocities CND (as decreases) clearly suggests Indeed, our models show that even if upper end its allowed range, evidence does not vanish, but remains lower limit BH}>3\times10^5$ M$_\odot$.