Local Group Dwarf Spheroidals: Correlated Deviations from the Baryonic Tully-Fisher Relation

TL;DR

This study investigates how dwarf spheroidal galaxies in the Local Group deviate from the Baryonic Tully-Fisher Relation, revealing correlations with physical properties and implications for dark matter and modified gravity theories.

Contribution

It uncovers non-random deviations from the BTFR in dwarf spheroidals and links these deviations to physical characteristics and tidal effects, proposing a test to differentiate between b1CDM and MOND.

Findings

Deviations from the BTFR correlate with luminosity, size, metallicity, and ellipticity.

Fainter and more tidally susceptible dwarfs deviate more from the BTFR.

The correlations suggest tidal effects influence the deviations, challenging stochastic process explanations.

Abstract

Local Group dwarf spheroidal satellite galaxies are the faintest extragalactic stellar systems known. We examine recent data for these objects in the plane of the Baryonic Tully-Fisher Relation (BTFR). While some dwarf spheroidals adhere to the BTFR, others deviate substantially. We examine the residuals from the BTFR and find that they are not random. The residuals correlate with luminosity, size, metallicity, ellipticity, and susceptibility of the dwarfs to tidal disruption in the sense that fainter, more elliptical, and tidally more susceptible dwarfs deviate farther from the BTFR. These correlations disfavor stochastic processes and suggest a role for tidal effects. We identify a test to distinguish between the {\Lambda}CDM and MOND based on the orbits of the dwarf satellites of the Milky Way and how stars are lost from them.