Object Identification in Abell 2151

[hgg]

Hello everybody,

Recently I took a picture of the Hercules Galaxy Cluster (Abell 2151).

Full Frame:
http://www.astrovox.gr/forum/album_pic.php?pic_id=18032

Telescope: Celestron CGE & C9.25" f/6.3 @ 1480mm
CCD : SBIG ST-2000XCM @ -10 Celsius.
Exposure: 17 x 900 sec with AO-8 @ 10Hz.
Image Scale : 1 arcsec / pixel


When you compare the above photo with the one from the STScI Digitized Sky Survey you can clearly see the proper
motion of a couple of stars (which is quite interesting by itself) but in the STScI frame, galaxy PGC57073 has a peculiar
structure that its completely missing in my photo. Could this be some kind of artifact in the STScI frame?
Have you ever seen anything similar?

Below is an animated GIF of the cropped region. The red arrow points to the structure in question.


PGC57073

Animation in Full Resolution:
http://s5.postimg.org/wk2q8dg2v/Abell_2 ... ed_750.gif

Thank you.
George.

[BMAONE23]

Interesting find. I can see motion of at least 7 separate objects in the full size image. Not sure about the queried object though

[Ann]

The galaxy you pointed to is sometimes called NGC 6054, although I believe it is nameless. At least it has no name in my software, Guide.

But the galaxy is certainly interesting, and it has been described, too. In The Color Atlas of Galaxies, James D Wray wrote:

NGC 6054 is the galaxy (...) with the extraordinary blue bar. There are practically no bars similar to this...

However, there is no sign of the strange structure seen in the STScI Digitized Sky Survey image in James D Wray's picture.

But the galaxy is unusual, and the blue bar is striking. You can see it quite clearly in this picture by Adam Block.

In Adam Block's image, you can see some clumpiness in the outer structure of the galaxy in question, but there is nothing in Block's image that resembles the long, curved, sharply defined shape that is visible in the STScI Digitized Sky Survey image.

Tony Hallas has also photographed the Hercules cluster and the galaxy sometimes (but erroneously) called NGC 6054. In Hallas' image, there is nothing that resembles the strange feature in the Sky Survey image.

My completely amateur opinion is that the feature seen in the Sky Survey image is an artifact. Either that, or it is an actual photo of a transient phenomenon, such as a (very elongated) asteroid passing by.

Ann

[hgg]

The red triangle I used in the photo is a bad indicator because it has equal sides...
It was supposed to point upwards.

The galaxy you pointed to is sometimes called NGC 6054

Please check again, because my software and STScI identify that galaxy as PGC57073.
NGC6054 is the galaxy on the left of PGC57073.


PGC57073

George.

[geckzilla]

Yeah, looks like some kind of artifact. Not too familiar with all the possible artifacts but it could just be a cosmic ray.

[hgg]

Probably its an artifact of some kind because its not in the blue filter frame of STScI.

[Ann]

hgg wrote:
Please check again, because my software and STScI identify that galaxy as PGC57073.

Your software is better than mine, because my software doesn't recognize it. But I recognize the shape and position of the galaxy. Thanks for telling me that the designation of the galaxy is PGC 57073.

Ann

[hgg]

Hello Ann, you are welcome. I still cannot think what kind of artifact this can be.
I don't think that its a cosmic ray because these are usually straight lines with very strong impression on the CCD.
On the other hand,asteroids are usually like little dots or straight lines if they are moving fast and are close enough.
How you ever seen an example of an asteroid like that captured in an astrophoto?

[geckzilla]

I've seen accidental asteroids in Hubble data. The movement is very pronounced in them with both Hubble and the asteroid moving rapidly.
http://hubblesite.org/newscenter/archiv ... large_web/
Wouldn't really expect an asteroid trail to be so curved in DSS imagery, though... but sometimes things aren't how you expect them to be.

[hgg]

Amazing photo
Never seen anything like that. It looks like that the focal point is just around the corner!
Anyway, this is still a line though, not a structure.