Leo A - a nearby dwarf among distant giants - WIP

[wimvb]

We've had a few clear nights recently, and after I'd finished my main target, I pointed my scope at the dwarf irregular galaxy Leo A (Leo III). This rather isolated dwarf galaxy was discovered by Fritz Zwicky in 1942. It is located approximately 2.6 Mly distant (the same as M31, the Andromeda galaxy) and has a size of only about 6 000 ly. The galaxy consists mostly of dark matter, approximately 80%. Its stellar mass is 3.3x10⁶ solar masses, while its H1 content is double as much.

Before I collected data on this galaxy, I checked Aladin to see what was in the neighbourhood and came up with quite a lot. I decided to shift the fov so that a few interesting distant galaxy groups would fit in the same frame. These are indicated in the annotated luminance image. The most distant galaxy (group) has a red shift of 0.47, which puts it at a mind blowing 6.5 Billion light years distant. The brightest galaxy in this group, labeled "3651_0.4686", is roughly the same size as the Milky Way. There are several quasars in the image which have a red shift larger than 2.

Technical details:

telescope 190MN with ASI294MM camera

79 x 3 minutes exposures; total integration time 4 hours, luminance only so far.

Processed in PixInsight with just a touch of sharpening with BXT. Still a bit noisy, and I didn't do anything about the reflection from a bright star outside the view (just above Leo A). I will fix that once I've collected colour data.

Note that most of the fainter "gnats" aren't stars, they're galaxies or quasars.

Annotated version

• Blue: PGC galaxies
• Purple: distant galaxies (G) and quasi stellar objects (Q), with their red shift
• Dark yellow: galaxies, with their red shift
• Light yellow: galaxies in groups

My search in Vizier didn't pick up on all galaxies in this image. There are several more with red shifts of about 0.18 - 0.2, putting them roughly at distances around 2.5 Billion light years

[gorann]

Very cool Wim! Are there any other images of Leo A? I could not find any after a short search on Astrobin.

There is a small area of bands just north of Leo A. Is that an artifact of something real (would be an odd artifact - banding are usually not that local).

Cheers, Göran

[wimvb]

1 hour ago, gorann said:

Very cool Wim! Are there any other images of Leo A? I could not find any after a short search on Astrobin.

There is a small area of bands just north of Leo A. Is that an artifact of something real (would be an odd artifact - banding are usually not that local).

Cheers, Göran

Thanks, Göran. Those lines are reflections from a star outside the field of view. Unfortunately they are quite common on my images this season. There's probably a shiny surface somewhere in my camera/filterwheel that causes them. Normally I can tone them down during processing, but since this a "quick & dirty", I haven't bothered this time.

There aren't many images of Leo A (Leo III) other than Hubble and Subaru Telescope images, that I know of. So, this is something of a first, at least on SGL.

Edited December 25, 2022 by wimvb

[symmetal]

Thanks Wim. Most interesting. Looks like more non-stellar objects than stars. 🙂

Alan 

[Paul M]

Very nice. The main subject looks like a cheap Magellanic Cloud rip-off 🤣

There is a clustering of "purple" coded objects in its outer reaches. At first I thought it was due to how the labels had been arranged but the objects are indeed in close (apparent!) proximity to Leo A, like globular clusters might be arranged. There are other clustering of purple things in the image so it's clearly just a chance alignment. Interesting all the same!

 

[geeklee]

Very interesting Wim and good write up as always.  Great use of the limited Luminance so far.

[wimvb]

4 hours ago, symmetal said:

Thanks Wim. Most interesting. Looks like more non-stellar objects than stars. 🙂

Alan 

Thank you, Alan. I think so too.

[wimvb]

3 hours ago, Paul M said:

Very nice. The main subject looks like a cheap Magellanic Cloud rip-off 🤣

Thank you, Paul. Why should the southerners be the only ones with irregular dwarfs to photograph? 😉

3 hours ago, Paul M said:

There is a clustering of "purple" coded objects in its outer reaches. At first I thought it was due to how the labels had been arranged but the objects are indeed in close (apparent!) proximity to Leo A, like globular clusters might be arranged. There are other clustering of purple things in the image so it's clearly just a chance alignment. Interesting all the same!

I didn't even consider ordinary globular clusters in or near this galaxy. Will have a look later.

[wimvb]

1 hour ago, geeklee said:

Very interesting Wim and good write up as always.  Great use of the limited Luminance so far.

Thank you, Lee. Glad you like it.

Edited December 25, 2022 by wimvb

[wimvb]

21 hours ago, Paul M said:

Very nice. The main subject looks like a cheap Magellanic Cloud rip-off 🤣

There is a clustering of "purple" coded objects in its outer reaches. At first I thought it was due to how the labels had been arranged but the objects are indeed in close (apparent!) proximity to Leo A, like globular clusters might be arranged. There are other clustering of purple things in the image so it's clearly just a chance alignment. Interesting all the same!

 

I searched Simbad and Vizier for objects in or near Leo A.

I didn't find any globular clusters, which is a bit odd, because other dwarf galaxies (ngc 185, ngc 147 for example) do have them. Maybe Leo A is so much younger than other dwarfs? This is likely, because galaxies such as ngc 147 / 185 are yellow/red in appearance, which is an indication of older stellar populations. The colour images I have seen of Leo A show more blue stars.

I think that the abundance of QSOs near the line of sight of Leo A is a result of cataloguing objects in the many observations and studies of Leo A. It's similar to what Messier did; if you want to exclude objects from a study, you need to identify them. Many of the QSOs have large red shifts, so they are not in or near the galaxy itself.

I only found a handful of H-alpha (HII) regions in or near Leo A, but I will definitely image it with an H-alpha filter when I get the chance. If there are young stars, there is also very likely some new star formation going on, so there could very well be Ha regions which no one has images yet.