madbadgalaxyman
25-09-2013, 06:27 PM
Here is an up-to-date (complete as of year 2012) list of all of the so-far discovered satellite galaxies of our own Galaxy and M31(= the Andromeda Galaxy)
It is a table from the Astronomy & Astrophysics Preprint arxiv:1305.0560
The paper can be cited as the above, or as B.Yniguez et al., MNRAS submitted, 2013
148425
M31 satellite galaxies are on the left side. Milky Way satellite galaxies are on the right side. For both the Milky Way Galaxy and M31, the following information is given in columns:
- name of the satellite galaxy
- distance of the satellite galaxy from the main galaxy, in units of kiloparsecs
- visual luminosity of the satellite galaxy, in multiples of one solar luminosity
- the year that the satellite galaxy was discovered (unfortunately, this was cut off from the jpg, for the Milky Way satellites, but it is in the original table)
This is a beautiful table for comparing the luminosities of these various galaxies. It seems very plausible that there are a good number of undiscovered Milky Way satellite galaxies that are hiding near the plane of the apparent band of the Milky Way, as the tiny satellites are of extremely low surface brightness.
Important note added in edit:
This table does not include any detected & discovered satellite galaxies which have less than 10,000 solar luminosities (in the V band). Apparently, there are also supposed to exist what have come to be called "ultra-faint dwarfs", which are galaxies with individual luminosities that fall in the range 100 to 10,000 solar luminosities, but how can you call such a low luminosity object a galaxy?
It is thought, though, that the ultra-faint dwarf galaxies do contain dark matter, which is not the case for globular star clusters; the difference between tiny dwarf spheroidal galaxies and globular clusters is in the velocities of the stars and in the required amount of gravitational binding.
If these ultra-faint dwarf galaxies really do exist, then they correspond essentially to the "dark galaxies" in theoretical cosmological simulations, which contain a lot of dark matter but only a smattering of stars. There were a couple of papers claiming actual detection of these tiny objects, but I remain to be convinced that they are real.
It is a table from the Astronomy & Astrophysics Preprint arxiv:1305.0560
The paper can be cited as the above, or as B.Yniguez et al., MNRAS submitted, 2013
148425
M31 satellite galaxies are on the left side. Milky Way satellite galaxies are on the right side. For both the Milky Way Galaxy and M31, the following information is given in columns:
- name of the satellite galaxy
- distance of the satellite galaxy from the main galaxy, in units of kiloparsecs
- visual luminosity of the satellite galaxy, in multiples of one solar luminosity
- the year that the satellite galaxy was discovered (unfortunately, this was cut off from the jpg, for the Milky Way satellites, but it is in the original table)
This is a beautiful table for comparing the luminosities of these various galaxies. It seems very plausible that there are a good number of undiscovered Milky Way satellite galaxies that are hiding near the plane of the apparent band of the Milky Way, as the tiny satellites are of extremely low surface brightness.
Important note added in edit:
This table does not include any detected & discovered satellite galaxies which have less than 10,000 solar luminosities (in the V band). Apparently, there are also supposed to exist what have come to be called "ultra-faint dwarfs", which are galaxies with individual luminosities that fall in the range 100 to 10,000 solar luminosities, but how can you call such a low luminosity object a galaxy?
It is thought, though, that the ultra-faint dwarf galaxies do contain dark matter, which is not the case for globular star clusters; the difference between tiny dwarf spheroidal galaxies and globular clusters is in the velocities of the stars and in the required amount of gravitational binding.
If these ultra-faint dwarf galaxies really do exist, then they correspond essentially to the "dark galaxies" in theoretical cosmological simulations, which contain a lot of dark matter but only a smattering of stars. There were a couple of papers claiming actual detection of these tiny objects, but I remain to be convinced that they are real.