List of satellites of M31 & the Milky Way Galaxy

[madbadgalaxyman (Robert)]

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



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.

[mental4astro (Alexander)]

This is a great resource, Robert, Thanks for the list.

In another thread I mentioned these satellite galaxies of the MW, and how several of them are visible at this time of year. I'll add a link to this thread in the other for reference to them. If I get to go bush this coming new Moon, I'll have a ping for them.

Mental.

[mithrandir (Andrew)]

Robert, I've regenerated the screenshot.

[Blue Skies (Jacquie)]

Thanks for that, Andrew. I was wondering why there was two sections but I can see the different dates now.

[madbadgalaxyman (Robert)]

Originally Posted by mental4astro

In another thread I mentioned these satellite galaxies of the MW, and how several of them are visible at this time of year. I'll add a link to this thread in the other for reference to them. If I get to go bush this coming new Moon, I'll have a ping for them.
Mental.

G'day Alex.
In general, for the low luminosity satellites of the MW and the Andromeda Galaxy, the surface brightness of a specific galaxy will be progressively ever lower, with progressively decreased total luminosity of a galaxy.

Those galaxies in this table that were found after year 2000 were tough to detect even in long CCD exposures; so I guess that this probably rules them out for visual detection!

I have viewed NGC 185 and NGC 147 ; easy enough visually, but I have never tried to see Leo I and Leo II with my own eyes. It seems plausible that visual observers could see Leo I and Leo II.

The likes of the Ursa Minor and Draco and Carina galaxies should be extremely elusive, visually, as they display little contrast with the field even in photos, and they are a lot less luminous than N185 and N147

Leo I looks obvious on the Sloan Digital Sky Survey image (which was a short exposure) and on modest amateur exposures, so this object could be fair game for visual observers. On the other hand, Leo II still looks faint, even on the Digitized Sky Survey image.

Just for fun, I might eventually attach images of some of these extremely faint dwarf satellite galaxies!

Best regards, Robert

N185 and N147 are a long way north. I was able to see them well from Darwin at latitude about 12 degrees south.
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Thanks Mithrandir for fixing up the table of satellite galaxies!

"in secret chambers withered men compounded strong elixirs, or in high cold towers asked questions of the stars"
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