Gloubular Cluster Ejected from M87

[Jimi Lowrey]

The CFA at Harvard has found a globular cluster (HVGC1) that has been ejected from M 87at hypervelocity speeds. There are many known runaway stars but this is the first found runaway star cluster.

Link to announcement,
http://www.cfa.harvard.edu/news/2014-09

I had hope that that the globular cluster would be visible in most telescopes but it looks like it will be a real challenge object. I looked at the SDSS photometry and it looks like HVGC 1 has a V MAG 20.5 approximately.

hvgc 1 2.jpg

I am going to "Give it a Go" the next good night here and will report back what I see or don't see.

[Ivan Maly]

Interesting object. Certainly give it a go, Jimi - I routinely see down to a supposed Vmag 18.5 with my 12-16" scopes if the SDSS photometry is to be believed. It may be a V-band photometry, but the magnitudes that come out are evidently not visual magnitudes by the original definition.

EDIT: Oops. I've encountered some magnitudes that seemed too faint, but what I am saying here is wrong - see the discussion below.

[Jimi Lowrey]

Ivan 20.5 is the visual Mag I converted the G band Mag and the R band Mag to give the approximate visual mag.

[Steve Gottlieb]

Interesting object. Certainly give it a go, Jimi - I routinely see down to a supposed Vmag 18.5 with my 12-16" scopes if the SDSS photometry is to be believed. It may be a V-band photometry, but the magnitudes that come out are evidently not visual magnitudes by the original definition.

Ivan, your note on magnitudes caught my attention. I've generally found the SDSS magnitudes to be reasonably accurate, when deriving B and V (compared to RC3), using their conversion formulas. Can you give a 2 or 3 examples of galaxies with SDSS Vmag of 18-18.5 that you've logged with your scopes?

[Ivan Maly]

No, Steve, I can't! I was not talking about galaxies, but that is not the issue. On re-checking my records, the faintest magnitude is Vm 17.5 (according to NOMAD1 - not SDSS!) of a starlike HII region/OB association, the southernmost in the group of three on the S end of NGC 3079 (NOMAD1 1456-0210761).

EDIT: Correction - northernmost.

[Steve Gottlieb]

Thanks for clarifying, Ivan. Coincidentally, there is a small, dim galaxy (SDSS J100200.72+554247.0 ) just east of the northern end of NGC 3079, which was very faint (to me) in Jimi's 48-inch. This one has a computed V mag of 18.6.

[Marko]

I would think that the sort of glob that could be 'thrown' would have to be the type with a big black hole at the center lest it be ripped apart as it was flung.

Im not going to try in my 18" as mag 20 it 'out of band' for my setup and my eyes. Curious to play with a new query-toy I have done to query my observations easily I scanned around and noted that on Mt Lason (8000 ft so good transparency) my dimmest galaxy was Hickson 99D where MegaStar says mag 17.2 but not sure if that is V or what and could only see it for brief periods of time as seeing cleared. Also noted that night myself and Greg Laflame could see Hickson 99E at mag 17.7 but only using Greg's 22", I could not see that in my 18 try as I may. My experience in the past is that 8000 feet adds a noticeable advantage due to you are above much of the muck so I doubt I could have seen these down at much lower altitudes. It was also an amazing night of course to get these.

On that galaxy east of Ngc3079 I note that on MegaStar RealSky dss that MAC 1002+5542 is just barely a dim smudge. That is a dim one and may not be very concentrated. I have felt that it would be nice if galaxies were additionally rated with a 'concentration' much like globulars but for some reason that does not seem to be the case. Seems obvious to me. It would be a number that perhaps indicated the percentage of the magnitude felt to be within the center 15% of the galaxy detected size. Why rate globs, clusters this way but NOT galaxies? Maybe it is just too hard to get data like that for these very tiny objects.

[Steve Gottlieb]

Curious to play with a new query-toy I have done to query my observations easily I scanned around and noted that on Mt Lason (8000 ft so good transparency) my dimmest galaxy was Hickson 99D where MegaStar says mag 17.2 but not sure if that is V or what and could only see it for brief periods of time as seeing cleared. Also noted that night myself and Greg Laflame could see Hickson 99E at mag 17.7 but only using Greg's 22", I could not see that in my 18 try as I may.

Marko, the Megastar magnitudes are from Hickson's 1989 paper "A photometric catalog of compact groups of galaxies" and are B total. Subtract 1.0 from these, and you'll come pretty close to V. By the way, I also found HCG 99E pretty tough, but doable, in my 24".

[Marko]

When you say 'subtract 1' are you saying mag 16 becomes mag 15 since B only a little bit of energy that the approximate magnitude for galaxies (mix of stars) is 1 mag brighter when considering the broader energy of the V filter?