The isotropic center of NGC 5419 -- A core in formation?

Abstract

With its cored surface brightness profile, the elliptical galaxy NGC 5419 appears as a typical high-mass early-type galaxy (ETG). However, the galaxy hosts two distinct nuclei in its center. We use high-signal MUSE (Multi-Unit Spectroscopic Explorer) spectral observations and novel triaxial dynamical orbit models to reveal a surprisingly isotropic central orbit distribution in NGC 5419. Recent collisionless simulations of merging massive ETGs suggest a two-phase core formation model, in which the low-density stellar core forms rapidly by supermassive black holes (SMBHs) sinking into the center due to dynamical friction. Only afterwards the SMBHs form a hard binary and the black hole scouring process slowly changes the central orbit distribution from isotropic to tangential. The observed cored density profile, the double nucleus and the isotropic center of NGC 5419 together thus point to an intermediate evolutionary state where the first phase of the core formation has taken place, yet the scouring process is only beginning. This implies that the double nucleus is a SMBH binary. Our triaxial dynamical models indicate a total mass of the two SMBHs in the center of NGC 5419 of MBH = (1.0 +/- 0.08) 10^10 Msol. Moreover, we find that NGC 5419's complex kinematically distinct core (KDC) can be explained by a coherent flip of the orbital rotation direction of stars on tube orbits at ~3kpc distance from the galaxy center together with projection effects. This is also in agreement with merger simulations hosting SMBHs in the same mass regime.

Accepted for publication by ApJ

References in corpus (17)

• Triaxial orbit based galaxy models with an application to the (apparent) decoupled core galaxy NGC 4365
• Dark Matter Substructure in Numerical Simulations: A Tale of Discreteness Noise, Runaway Instabilities, and Artificial Disruption
• The SAURON project - VIII. OASIS/CFHT integral-field spectroscopy of elliptical and lenticular galaxy centres
• Recoiling Supermassive Black Holes: a search in the Nearby Universe
• Formation of the largest galactic cores through binary scouring and gravitational wave recoil
• A novel approach to optimize the regularization and evaluation of dynamical models using a model selection framework
• SMART: A new implementation of Schwarzschild's Orbit Superposition technique for triaxial galaxies and its application to an N-body merger simulation
• Radial Kinematics of Isolated Elliptical Galaxies
• The two phases of core formation -- orbital evolution in the centres of ellipticals with supermassive black hole binaries
• Non-parametric Triaxial Deprojection of Elliptical Galaxies
• The supermassive black hole and double nucleus of the core elliptical NGC5419
• Dynamical modelling of the twisted galaxy PGC 046832
• The nuclear activity and central structure of the elliptical galaxy NGC 5322
• A simple data-driven method to optimise the penalty strengths of penalised models and its application to non-parametric smoothing
• Accuracy and precision of triaxial orbit models I: SMBH mass, stellar mass and dark-matter halo
• Detailed shapes of the line-of-sight velocity distributions in massive early-type galaxies from non-parametric spectral models
• Accuracy and precision of triaxial orbit models II: Viewing angles, shape and orbital structure

Cited by in corpus (3)

• The supermassive black hole merger driven evolution of high-redshift red nuggets into present-day cored early-type galaxies
• Triaxial Schwarzschild Models of NGC 708: a 10-billion solar mass black hole in a low dispersion galaxy with a Kroupa IMF
• Identifying supermassive black hole recoil in elliptical galaxies