The fundamental manifold (FM), an extension of the fundamental plane formalism, incorporates all spheroid-dominated stellar systems from dwarf ellipticals up to the intracluster stellar populations of galaxy clusters by accounting for the continuous variation of the mass-to-light ratio within the effective radius re with scale. Here we find that Local Group dwarf spheroidal and dwarf elliptical galaxies, which probe the FM relationship roughly one decade lower in re than previous work, lie on the extrapolation of the FM. When combined with the earlier data, these Local Group dwarfs demonstrate the validity of the empirical manifold over nearly 4 orders of magnitude in re. The continuity of the galaxy locus on the manifold and, more specifically, the overlap on the FM of dwarf ellipticals like M32 and dwarf spheroidals like Leo II, imply that dwarf spheroidals belong to the same family of spheroids as their more massive counterparts. The only significant outliers are Ursa Minor and Draco. We explore whether the deviation of these two galaxies from the manifold reflects a breakdown in the coherence of the empirical relationship at low luminosities or rather the individual dynamical peculiarities of these two objects. We discuss some implications of our results for how the lowest mass galaxies form.
- Galaxies: elliptical and lenticular, cD
- Galaxies: formation
- Galaxies: fundamental parameters
- Galaxies: structure
ASJC Scopus subject areas
- Astronomy and Astrophysics
- Space and Planetary Science