Modelling the Canes Venatici I dwarf spheroidal galaxy

¹ Departamento de Astronomía, Universidad de Concepción, Casilla 160-C, 3340 Concepción, Chile
e-mail: mfellhauer@astro-udec.cl
² Observatories of the Carnegie Institution of Washington, 813 Santa Barbara St., Pasadena, CA 91101, USA

Received: 2 April 2019
Accepted: 18 November 2019

Abstract

The aim of this work is to find a progenitor for Canes Venatici I (CVn I), under the assumption that it is a dark matter free object that is undergoing tidal disruption. With a simple point mass integrator, we searched for an orbit for this galaxy using its current position, position angle, and radial velocity in the sky as constraints. The orbit that gives the best results has the pair of proper motions μ_α = −0.099 mas yr⁻¹ and μ_δ = −0.147 mas yr⁻¹, that is, an apogalactic distance of 242.79 kpc and a perigalactic distance of 20.01 kpc. Using a dark matter free progenitor that undergoes tidal disruption, the best-fitting model matches the final mass, surface brightness, effective radius, and velocity dispersion of CVn I simultaneously. This model has an initial Plummer mass of 2.47 × 10⁷ M_⊙ and a Plummer radius of 653 pc, producing a remnant after 10 Gyr with a final mass of 2.45 × 10⁵ M_⊙, a central surface brightness of 26.9 mag arcsec⁻², an effective radius of 545.7 pc, and a velocity dispersion with the value 7.58 km s⁻¹. Furthermore, it is matching the position angle and ellipticity of the projected object in the sky.