Structure and kinematics of tidally limited satellite galaxies in LCDM

Abstract

We use 𝑁-body simulations to model the tidal evolution of dark matter-dominated dwarf spheroidal galaxies embedded in cuspy Navarro-Frenk-White subhalos. Tides gradually peel off stars and dark matter from a subhalo, trimming it down according to their initial binding energy. This process strips preferentially particles with long orbital times, and comes to an end when the remaining bound particles have crossing times shorter than a fraction of the orbital time at pericentre. The properties of the final stellar remnant thus depend on the energy distribution of stars in the progenitor subhalo, which in turn depends on the initial density profile and radial segregation of the initial stellar component. The stellar component may actually be completely dispersed if its energy distribution does not extend all the way to the subhalo potential minimum, although a bound dark remnant may remain. These results imply that "tidally-limited" galaxies, defined as systems whose stellar components have undergone substantial tidal mass loss, neither converge to a unique structure nor follow a single tidal track, as claimed in earlier work. On the other hand, tidally limited dwarfs do have characteristic sizes and velocity dispersions that trace directly the characteristic radius (𝑟 mx ) and circular velocity (𝑉 mx ) of the subhalo remnant. This result places strong upper limits on the size of satellites whose unusually low velocity dispersions are often ascribed to tidal effects. In particular, the large size of kinematically-cold "feeble giant" satellites like Crater 2 or Antlia 2 cannot be explained as due to tidal effects alone in the Lambda Cold Dark Matter scenario.

Astrophysical Tests of Dark Matter Self-Interactions

“…In recent years, there has been a growing focus on the mechanism of disruption of subhalos in collisionless CDM N -body simulations (see, e.g., [683,684,685,466,686]). It has been pointed out that much finer force resolution may be needed to faithfully follow the tidal stripping of subhalos inside a more massive host halo than what was estimated previously, and has been used in much of the existing literature.…”

A detailed star formation history for the extremely diffuse Andromeda XIX dwarf galaxy

“…Such transformations from normal dwarf to UDG are debated. While recent focused 𝑁−body simulations by Errani et al (2021) and Borukhovetskaya et al (2021) have shown that tides alone cannot reproduce the extended radii of these galaxies if they are embedded in cusped halos, others find tidal shocking and stripping can explain both their ex-tremely low masses and extended radii (e.g. Jiang et al 2019;Liao et al 2019;Macciò et al 2021;Moreno et al 2022).…”