Schultz hunting local and nonlocal dwarves in Sagittarius:
>I hoped to get at least an "obscured" glimpse of the other dwarf galaxy in
Sagittarius: SagDEG, the Sagittarius Dwarf Elliptical Galaxy. SagDEG, is
purportedly a knot within M54....Maybe SagDEG was in once of the areas of
concentration in my sketch.
For any innocent person stumbling onto this, there are two dwarf galaxies in
our area of space called Sagittarius Dwarfs. The closer one is SagDEG,
mentioned above. Why a real smart guy like Bill Schultz was trying to find a
galaxy inside a globular will remain a mystery. More on that just below...*
The other one, much farther away, the one Bill has made a name for himself
by observing, is called the Sagittarius Dwarf Irregular Galaxy. I'm not
putting you on.
Just this last week I was checking out these characters on paper, getting
intrigued about observing as much of the Local Group as possible. Far as I
know, only Tom Polakis has gone after our own group systematically. I'd love
to be wrong here, there's a dearth of observing guideposts for these
toughies.
Brian Skiff keeps an updated list here:
ftp://ftp.lowell.edu/pub/bas/deepsky/local.group
As you can see, he calls SagDEG "Sgr I" to save confusion.
* 1) Bill, you've got the in-and-out part backwards. M54 is inside Sgr I,
either a massive globular or the remnant of the galaxy's core. The dwarf
galaxy itself is being assimilated into the Milky Way and is spread around
enough sky to be impossible to pick up in an amateur scope. I don't believe
anyone has ever even seen the thing; its existence has been figured out
statistically. When we're looking at M54 we're peeking at the bright inside
part of Sgr I, about 90 kly away. According to SEDS, Arp 2, Terzan 7 and 8
are also inside Sgr I.
2) Far as the distant thing (SagDIG) goes, I'd googled and looked over
amastro and you my friend are in august company. Only Steve Coe has seen
this thing visually, far as I can find. As Skiff mentions below, it's too
far away to be in the gravitational field of the Local Group, being some 3.8
million lightyears from here. There are lots of references in the literature
to SagDIG being in the local group, but Skiff is a numbers man and keeps up.
You saw - "Just a faint oval (3:2/E:W) smudge."
Here are Coe's notes from this past 10 September, pretty similar. Same PA.
http://groups.yahoo.com/group/amastro/message/10810
>ESO 594-4 is the Sagittarius Dwarf Galaxy Sunglow Ranch 13" f/5.6
150X--just barely seen, 220X is a little better still very faint, small,
elongated 1.5X1 in PA 90, not brighter in the middle and tough to hold
steady.
Here's the Great Skiff explaining the name-fu just a couple of weeks ago:
>Just to keep things clear, I was referring previously to the "Sagittarius
Dwarf" whose center is conveniently defined as the globular cluster M54,
and which is thought to be merging with the Milky Way.
The thing Steve Coe observed is usually called 'SagDIG' in the
literature, but is perhaps best called by the ESO catalogue name,
ESO 594-G04. It's position is 19 30 00 -17 40.8 (J2000). Since it also
is listed in SIMBAD with the alias "Kowal's Object", it was probably found
prior to 1977 by Charlie Kowal on his Palomar Schmidt plates, but since
he was looking for out solar-system objects, he didn't obther to publish
it formally. It's also possible it was discovered independently by
Harold Corwin during his Southern Galaxy Survey. The SIMBAD bibliography
shows another later (1978) report by Longmore et al.
This is not a Local Group galaxy, by the way.
Just as a guess, the folks who proclaimed the currently-famous
"Sagittarius Dwarf" were unaware that a different nearby system already
had a similar name in the same constellation. Of course, everyone ignored
NGC 6822, the dwarf galaxy in Sagittarius discovered (visually, mind you)
before everyone involved was born.
\Brian
(Of course 6822 is Barnard's Galaxy. I often regret that E.E. Barnard was
around before we were born. He worked locally, and was supposed to have been
a wonderful teacher who loved public nights up there at the Lick.)
Cheers,
Jamie
-- Jamie Dillon <*> speech pathologist jamie_dillon@No-Spam " ... " - Harpo Marx