M89's outer shell, globulars and last "meal"
Posted 28 January 2013 - 04:38 PM
I'd ignored most elliptical galaxies as boring. But since it was an M object decided I had to add it to my digital library. I'd not paid it any attention until I went to process this image. At first I thought my flats were bad as there was a faint halo around the galaxy, mostly to the south as well as a large smudge to the southwest. I was debating whether I could salvage the mess when I found that these were real. It has a large but very faint halo few seem to have picked up except on a very deep images such as one by David Malin. Turns out I didn't pick up but part of it. The large elongated smudge is thought to be the remains of M89's last meal that it is still digesting. Malin's image is at: http://messier.seds....e/m089_aat.html . It needs far more time than I gave it to pull out these features as more than a hint. Doesn't help that my L filter had loosened in the filter wheel and rotated slightly so the dust mots didn't line up perfectly limiting how far I could stretch the image.
The annotated image shows the globular clusters NED listed that were visible in my image. They are noted by *CL. I found that just by looking at them I couldn't tell a faint star from a distant galaxy from a globular cluster. A plate solve however made it easy to separate one from the other. I noted the galaxies (even though there's no distance known) with a G?. Stars were left unlabeled. One NED lists as a globular is rather orange which bothers me. Seems an odd color for a globular cluster. Looking at it in the Sloan image it looked perfectly star-like. It is on the southeast side of M89 with an anonymous galaxy (not in NED) beyond it.
One of the smaller smudges in the halo turns out to be VCC 1613 which NED shows as a dE2 galaxy (dwarf elliptical). The other smudge to the north wasn't listed in NED but I do see it in the second image at: http://cseligman.com...tlas/ngc45a.htm . Note the orange "globular" looks like an ordinary star in this image. I really question NED's identification of it as a globular.
14" LX200R @ f/10, L=4x10' RGB=2x10', STL-11000XM, Paramount ME
Posted 28 January 2013 - 10:24 PM
Posted 28 January 2013 - 10:39 PM
Posted 29 January 2013 - 12:27 AM
Yeah, your image really matches Malin's image. It's amazing how often I am ready to "process out" what seems to me like an artifact - only to find some deep image of it somewhere in my research that matches shows it too.
Won't a really old globular tend toward the reddish hue a bit? (although the cseligman image does seem a bit on the orange side). Secondly, does your image show two points of light in that area where the orange globular is?
Posted 29 January 2013 - 01:48 AM
I don't see the double object in my image. I made a mistake in annotating it when I used the NED symbol of *CL. I should have just use a C. That asterisk gets in the way. I've got another M object further down the line that also has globulars. I started annotating it (long way to go) and did the same. Think I'll go back and get rid of that asterisk at least.
I've attached the SDSS image of the object a 0.4" per pixel. Looks like a star there too. Don't know why so many stars are green in their image.
Posted 29 January 2013 - 07:40 PM
I did M87 years ago. Needs reprocessing as I've learned a lot over the last 4 years since it was done. NED lists some 2400 globulars plus another 250 or so of possible globulars. They rarely give a magnitude. I have no idea how many show in my image. But with 2400 to look through for those I do have is a bit more of a chore than I wanted to undertake back then so I didn't try to label them. Not sure if I can do it without undo time required even now since I can't filter by magnitude.
Posted 29 January 2013 - 11:31 PM
I don't see the double object in my image. I made a mistake in annotating it when I used the NED symbol of *CL. ...
Aha. I missed that by only looking at the annotated image - sorry. Still, do you think the color disqualifies it as a cluster and it is simply a foreground star?
Posted 30 January 2013 - 04:24 PM
Obviously they had a reason for classifying it as a globular. So I'd like to know more. Though in other galaxies (M87 for instance) SDSS has some 250 or so (I didn't count them, just an eyeball estimate looking at the data in NED) that he lists both as a star and a globular. To me that says they can't always tell.
Posted 30 January 2013 - 06:02 PM
Posted 30 January 2013 - 11:37 PM
I did M87 years ago.
thanks for the link. fantastic images and write-up!! (as usual)