Globular Cluster AM-4 associated with the Sgr Dwarf Spheroidal galaxy.

[Dennis]

And I thought that locating the terrible Terzan’s were difficult…:)

Here is my candidate for the Globular Cluster AM-4, a loose and faint cluster discovered by Madore & Arp in 1982. According to an article by Giovanni Carraro 2009, The Astronomical Journal 137 3809 (http://iopscience.iop.org/1538-3881/137/4/3809/fulltext/aj_137_4_3809.html), AM-4 is a candidate for being a young globular associated with the Sgr Dwarf Spheroidal galaxy.

I became attracted to this challenging target from the details provided at the astronomy-mall (http://www.astronomy-mall.com/Adventures.In.Deep.Space/obscure2.htm)website.

Last night (18th May 2013) I grabbed 20 x 5 min exposures with the Mewlon 180 F12 operating at F9.6 with the Tak x0.8 Reducer/Flattener and an SBIG ST2000XM CCD camera. These images were then calibrated, aligned and stacked in CCDStack then finished in CS6.

The LRGB image is made up of 3 x 10 minutes each LRGB data from the previous evening (17th May 2013) after my first attempt to record AM-4 and is provided for reference only as AM-4 is barely hinted at in the original Luminance data. The FOV is approx. 22x17 arc min at 0.83 arcsec/pixel.

Here is a link to the reference image (http://iopscience.iop.org/1538-3881/137/4/3809/fulltext/aj297013f1_hr.jpg)that I used, taken at the Las Campanas Observatory, using the 1.0 m Swope telescope equipped with the Site 3 2048 × 3150 CCD camera. The field of view is about 14.′8 × 22.′8 with a scale 0.435 arcsec pixel.

Although I did not manage to resolve the globular unambiguously, I think that the “cluster of grains” that I did manage to record is a good candidate for AM-4. It would probably require a dark sky site and more aperture to improve on these results. The 1st Quarter Moon was some 60 degrees away during the imaging session.

The attached animation shows some respectable correlation despite the BG noise...:);)

AM-4 details from SKyTools 3 Professional:

Globular Cluster
R.A.: 13h56m21.0s Dec.: -27°09'42" (2000) in Hydra
Magnitude: 15.90
Size: unknown

[allan gould]

Dennis, actually I can see the correlation better in the small image on your post rather than the larger one opened up.
Allan

[RickS]

Excellent sleuthing and imaging, Dennis!

[multiweb]

Wow! This is extreme detective work. I'm in awe how you find these things in the first place let alone managing to get signal. Top work. :thumbsup:

[SkyViking]

What a fascinating image you got there Dennis, well done :) It appears this one makes UKS-1 look like OmCen lol :D I read is has something like 1000 solar masses, that is one tiny globular!

Great effort as usual, thanks for sharing.

[Dennis]

Thank you Allan, Rick, Marc & Rolf, I appreciate your comments.:)

I combined the 3 x 10 min Lum data from the 17th May with the 20 x 5 min Lum data from 18th May and this has added some density to the clump of grains where AM-4 is shown in the image from Las Campanas Observatory. A new animation is attached.

I am now more confident now that the data from Brisbane is “real” and not just a collection of coincidentally matching, background noise!:)

Cheers

Dennis

[A23649]

That is some very cool imaging. That looks as real as it gets to me.

Cheers,
Nathan

[John Hothersall]

What a devilish object to get which you did, this really needs an ST10. I would have tried no filter as its so tricky at 16th mag. Impressive for a 7" scope at long FL with any Moon presence. Well Done Dennis.

John.

[Ross G]

Amazing capture Dennis.

Ross.

[Dennis]

Thanks Nathan, John and Ross, I appreciate your comments.:)

@John – thanks for your thoughts and analysis, they are very helpful. :thumbsup:

Cheers

Dennis