Luminosity-Diameter Relations for Globular Clusters and Dwarf Spheroidal Galaxies

TL;DR

This paper investigates the luminosity-diameter relationships of globular clusters and dwarf spheroidal galaxies, revealing distinct distributions and a separation line, with dwarf spheroidals generally being fainter than globular clusters.

Contribution

It introduces the concept of the Shapley line to distinguish between globular clusters and dwarf spheroidals in luminosity-diameter space.

Findings

Globular clusters and dwarf spheroidals have different flattening distributions.

They occupy adjacent but separable regions in the M_v versus log R_h plane.

Dwarf spheroidals are typically fainter than globular clusters.

Abstract

It is shown that globular clusters and the dwarf spheroidal companions of the Galaxy have a different distribution of flattening values, and appear to occupy adjacent regions of the M_v versus log R_h plane that can be separated by what will be referred to as the Shapley line. Surprisingly, typical dwarf spheroidal companions to the Milky Way System are fainter than the average Galactic globular cluster.