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Back to obscure satellite galaxies, Holmberg VIII

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#1 Rick J

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Posted 30 January 2013 - 04:33 PM

Holmberg VIII/UGC 8303 is a companion to the far more famous NGC 5033 to the north out of my field of view. It is located in Canes Venatici. Distance measurements for it range from 54 million light-years by redshift to 66 by a Tully-Fisher measurement. But as it is considered a satellite galaxy of NGC 5033 the distance to that galaxy must be considered. That covers an even wider range with APOD and a couple other sources settling on 38 to 40 million light-years. NGC 5033 is considered to have two satellites much like we have the two Magellanic Clouds. They are Holmberg VIII and UGC 08314 also in my image to the upper left of Holmberg VIII. NGC 5033 is also considered to have been affected by NGC 5005 which I've not yet imaged. Which, if any caused the strong warp seen in NGC 5033 I wasn't able to determine.

Holmberg VIII is classed by NED as IAB(s)m while UGC 08314 is listed as Im:. UGC 08314 has a redshift distance of 54 million light-years, same as Holmberg VIII. Since it is closely tied to NGC 5033 out of the image which many sources say is 40 million light-years away that is more likely the correct value. It has an odd vertical structure in the middle and then a large very faint western half. The eastern side has more bright areas and a small dim one to the northeast. A very unsymmetrical galaxy indeed.

A bright blue blob inside of Holmberg is identified by NED as SDSS J131318.46+361210.6. While listed as a separate galaxy it looks to me to be just a star cloud in Holmberg VIII. I've listed it in the annotated image. It does show a very slightly smaller redshift but I don't see that as sufficient to call it a separate galaxy.

It seems every field I image has some discrepancy when I dig into my research. This one is especially surprising. To the west of Holmberg VIII is the galaxy group SHK 248 with 9 members at a distance of 3.15 billion light-years. The problem is a possible member on the western side. NED shows two designations for it. SDSS J131210.13+361112.1 is at the right position showing a distance of 2.32 billion light-years. Too close to be a member. It's magnitude is in close agreement to my measurement, 18.6. NED also lists 4" of arc to the northwest at a position where nothing is seen, even on the Sloan survey image, 2MASX J13121012+3611117 a galaxy at magnitude 19.4 at a redshift distance of 3.15 billion light-years, correct for the group. It's position is listed with an error circle of 1", insufficient to overlap the only galaxy in the area. I tend to believe the Sloan data placing it too close to be part of the group.

14" LX200R @ f/10, L=4x10' RGB=2x10', STL-11000XM, Paramount ME

Full image


NGC 5033 it is orbiting (east at the top rather than my normal north up)


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#2 J.P.M



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Posted 31 January 2013 - 08:49 AM

Thanks, specially the write up.

#3 Bill W.

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Posted 31 January 2013 - 08:47 PM

Looks good Rick! Pretty interesting... :)


#4 hytham


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Posted 01 February 2013 - 03:09 AM


I absolutely love what you do. Thank you for taking the time to show all of us there is so much more than the same old thing.


#5 RStar



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Posted 01 February 2013 - 08:21 AM

Thanks Rick! I too enjoy seeing the faint and obscure.


#6 Rick J

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Posted 02 February 2013 - 01:24 AM

Thanks guys. As you know I prefer the less imaged and rarely retake something. I have a bunch of rarely seen and oddball stuff in the process loop. Just posted a strange flat galaxy and now am working on something that simply defies description yet is bright and large enough in angular size most here could image it, no one ever has that I could find.

So as they say on TV -- Stay tuned. I'm processing as fast as I can between doing what it takes to survive up here in the wilderness. Last night I thought I'd lost cooling regulation in my camera when set for -35C it started cooling colder than that setting off an alarm. Nope, just that the temperature outside was -36C and dropping. I need a heater in the camera, not a cooler.


#7 Jim Thommes

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Posted 02 February 2013 - 01:55 PM

Nice work. I like Holmberg VIII, but I think UGC 08314 is one of the weirder galaxies you've imaged - structure wise.

Wow, -36C degrees! Well, you have an observatory. The coldest I have been out in is -9C degrees. But then I am in a tent or sitting next to my scope with the laptop. Glad I'm not imaging in MN.

#8 Rick J

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Posted 02 February 2013 - 05:52 PM

They are both irregular dwarfs that can take about any crazy shape. Too small to take any regular shape against the tidal forces of their host galaxy.

Minnesota conditions are why I run remote -- all of 75 feet away. But that keeps me inside where it is nice and warm in winter and no skeeters in summer sucking my blood. I tried running from the observatory in the spring before the skeeters but then a midge fly hatch hit. They live only hours as an adult then die. Attracted to the screen and warmth of the computer they died and fell into the keyboard. Hundreds of dead midge flies killed my keyboard in one night. Fortunately it was an old laptop and I could get a replacement for $27 including shipping but did shut me down for a few days until it arrived.

Now I only go out to the observatory a few times a year, usually to put on the cloth filter I use to take flats. Then forget to take it off and wonder where the stars went come nightfall. Then out again to remove it. Door is only 5.5' high so you have to remember to duck. Forget and I can see stars on a cloudy night. Another reason I rarely go out there.


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