HCG059

It's not often an amateur gets to announce a new galaxy. But it appears I have discovered a previously unrecognized dwarf irregular galaxy probably on the edge of the Virgo Cluster some 60 million light-years distant. Considering how well studied this cluster is I never expected there'd be an undiscovered galaxy in the cluster. I'm posting this out of my normal order as some may still have a chance to get better data on it. My latitude makes that impossible for me. Here's the story of its discovery.

Since much of May had horrid skies I broke with tradition and decided to look at the images to see if they needed more data before they got too far west. Unfortunately, thanks to really bad weather here this field had already moved too far west and into trees before I looked at it. In looking at it I found an apparent reflection. The corrector of my SCT creates these all too often. I'd have marked it to redo in a slightly different position to get rid of the reflection but it was too late for that. So I marked the file to note the reflection needed to be removed.

But there was something "wrong" with the reflection that nagged at me. I went back a few days ago for a second look. Reflections are smoother and usually have streaks through them. This one was mottled with no streaks. Thus I decided it might be real after all. I checked the position against every catalog in VizieR but came up nearly empty. Sloan reported two essentially point sources in this area but no extended object. I had previously checked the GALEX images for this area and came up empty. But looking at the Sloan image it showed what at first appeared could be stronger noise against otherwise normal level background noise. The two objects it noted didn't match a bright speck in the image but all fell between them. But it didn't appear to be noise. I decided it was real but not in any catalog I could access. A check of the POSS plates showed something very faint in the POSS II blue plate. I decided it had to be real. Time to call in my pros. Unfortunately, most were getting ready or had already left for the AAS conference running June 12 through the 16th. Those I could reach dismissed it as a reflection even though it was in Sloan and very faintly in the POSS II blue plate. I'm sure they were too occupied with the conference to give me any time. What to do?

When this happens I fall back on Sakib Rasool who some of you know. He has lots of contacts. One is Igor Karachentsev a Russian astrophysicist who studies this area. Here is his reply when Sakib relayed my information to him: "yes, this object is unknown as a possible dwarf galaxy, only known as SDSS source. It is also not detected as HI-source in the ALFALFA HI survey in Arecibo. Due to its texture, it may be a peripheric dIr member of the Virgo cluster." Later he wrote: "sure, it is a real irregular dwarf galaxy of bluish color and low surface brightness, however, unseen in GALEX. Such kind objects may be gas-rich, as well as gas-poor." I should mention not being seen by ALFALFA HI means it is radio quiet, somewhat rare for a dwarf galaxy.

Until it is studied we won't know much more than this. I do measure its size as about 10,000 light-years if a member of the Virgo Cluster at about 60 million light-years. It may be a member of a Leo group about half as far away making it about 5,000 light-years across.

Igor had hoped to put the 6 meter scope on it but as usual, it was down for repairs so it didn't happen. If he tried again I never heard about it. He's about 78 years old so might have retired. An American astronomer was going to try and point Keck at it but a rare blizzard shut it down. I haven't heard from him since either.

It's coordinates are 11h 48m 09.1s +12d 48' 49".

Now for the regular part of the post about what I thought I was doing when I found the unknown galaxy.

HCG 59 is a group of 5 galaxies in about 2 degrees south of Denebola in Leo. 4 of the galaxies are about 200 million light-years distant but one is a bit over a billion light-years distant so obviously not a true member. Quite a few other galaxies are in the field that are at the 200 million light-year distance indicating the group is far larger than the subgroup that is HCG 59. Hickson groups have a very specific definition that is meant to rule out galaxy clusters. But ignores if they are actually related. Thus this group includes one that obviously isn't and excludes one that seems to be worthy of including that is the right distance but is too low of surface brightness to qualify. For more on the specifics see Hickson's paper at: http://articles.adsabs.harvard.edu/full/1982ApJ...255..382H/0000382.000.html

HCG 59C is the largest of the 4 truly related galaxies though being somewhat edge on appears smaller than 59A. It is only a bit over 50,000 light-years across. Less than half the size of 59E thanks to the latter's much greater distance. 59A appears to be a rather red and dead, or at least near dead spiral. By redshift, the closest member of the group is 59D which is a really neat irregular galaxy full of star clouds. Its redshift puts it at 180 million light-years distant. Enough difference from 59C's 220 million light-year distance they may not be related at all, just a line of sight group. An HST image of this galaxy is at: https://upload.wikimedia.org/wikipedia/commons/6/6b/Hickson_Compact_Group_59.jpg

Four asteroids are in the image. They are moving very slowly as they are at the point in their orbits where they are changing from between retrograde and prograde motion. In fact, two are prograde (p) and two are retrograde (r). I've caught asteroids near this point before but not with some on either side. Because they are moving so slowly all but one looks at first glance (maybe second as well) to be just a very distant, near starlike galaxy. To be sure I checked each against the Sloan images to verify nothing was there when Sloan took the field. Besides the positions matched those given by the Minor Planet Center's Minor Planet Checker. The night was poor (most are of late), I doubt I'd have picked these up if they were moving normal speed across the sky given the poor conditions.

The previously unknown galaxy is circled in dark green in the annotated image, to the upper right of HCG 59. I've stretched the heck out of this one to bring out the probably dwarf. That makes for some nasty stuff around bright stars that under a normal stretch wouldn't be seen. I further stretched the galaxy itself in the enhanced cropped image. Some of what you see is likely noise. I need a much longer exposure time than I gave it not knowing of its existence.

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

Pretty pictures are nice but finding something previously unknown is MUCH nicer.

Related Designations for HCG059

HCG061

The HCG 61 galaxy group is one of Hickson's most photogenic being composed of four bright, NGC galaxies arranged in a rectangle. This has given it its common name of "The Box". It is composed of NGC 4169, NGC 4173, NGC 4174 and NGC 4175. All but NGC 4173 are located about 200 million light-years from us. NGC 4173 is located only about 65 million light-years away by redshift though there's a good agreement that its non-redshift distance is only 30 million light-years. The group is located in northwestern Coma Berenices.

I measure NGC 4169 with a diameter of 135,000 light-years making it the largest of the group. NGC 4174 is the smallest at only 53,000 light-years while I measure NGC 4175 at 110,000 light-years. While appearing much larger, NGC 4173 is also much closer. I measure it, including the long arm to the southeast as being 84,000 or 39,000 light-years in size. If the closer distance is right it is the smallest of the four. At the time of Hickson's catalog distances to most of his galaxies was unknown. He was working on appearance, well aware that this isn't going to always equate to distance. Hence his name for them of Compact Groups. He didn't mean they really were compact, only that they appeared that way from our vantage point. Also, if you look around the annotated image you will find a few other galaxies also with a redshift of about 200 million light-years that are likely true members of the group but don't meet Hickson's requirements so aren't included in the group. What I do find odd is that when I ask NED for HCG 61 it says it has 3 galaxies, not four but then when asked individually about the four gives them the HCG letters A through D I show in the annotated image. I've found this count difference many times in NED. I suppose I should ask them about it but so far haven't done so.

This image had something go wrong. I still have no idea what but the left side of the image is way out of focus. If this were due to camera tilt (which has happened to me) the stars would elongate but these turned into donuts with a bit of distortion due to being at the edge of the field. All subs showed the same error. It was taken the same night as NGC 2742 and NGC 3686. It was taken between these two yet neither show this problem. I've not looked at all taken since but none I have looked at show this issue. I'm stumped as to what could cause it. Since that put the Abell 1495 galaxy cluster well out of focus I have this one on the reshoot list.

Just off the southwest end of NGC 4174 is ASK 574454.0 which NED lists as a candidate dwarf but if its redshift distance of 1.08 billion light-years is correct I measure it as being the same size as NGC 4174 which is a normal sized S0 galaxy. I suspect it got the possible dwarf label before its distance was known. But why that hangs on I find interesting, inertia?

There's a pair of interacting galaxies near the bottom center of the image, KISSBx 37. I couldn't find them listed separately. NED normally labels distance data as p for photographic, Spec as proven spectroscopic measurements. If likely spectroscopic but not proven it leaves that blank. For this one, however, they use the label ? which I've never seen before. I don't know what they mean by it but included it in the annotation. I can't prove these two are interacting but they sure appear to be interacting.

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

Related Designations for HCG061

HCG064

HCG 64 is a 4 galaxy group in Virgo about 5 degrees north of the ecliptic. This explains the 9 asteroids that poked their noses into the image. The three close galaxies are interacting. They are at a half billion light-years. The fourth member to the north, like the asteroids, has no connection to the other three. At the time Hickson defined is compact groups distances were mostly unknown. Like Arp's Atlas of Peculiar Galaxies with duos and trios did the same. In both cases sometimes the apparent closeness is just due to a similar line of sight. The three main galaxies in this group are obviously related. The fourth met his criteria so was included. He likely doubted it really belonged. One clue is that under the accuracy of magnitudes is on a scale of 1 to 4 but this one is listed as 5 for which there's no explanation.

I measure the plume that runs below HCG 64A at 192 thousand light-years. That's not counting the part to the southeast until it turns to the northeast. Including the galaxy and its plumes to the northwest and southeast gives the stars spread along a path 344,900 light-years long. I've never seen anything like this before. But the lower plume may not come from HCG 64. The "star" at the southeast end is a small galaxy, 2MASX J13254599-0352198. Unfortunately, there's no redshift data for it. Could it be part of HCG64 but too faint to make Hickson's requirements? If so all that's left of it is the plume and its core. I found absolutely nothing on this. Seems all too often I start with a simple interesting field and end up with unanswered questions.

Transparency was very poor for this image. Several other asteroids I'd normally have easily recorded didn't get through the gunk and less than average seeing. In looking through the asteroids in the image I found one that surprised me. I'd taken this image while an NEO was passing by. In fact, it was discovered only a day or two before the image was taken on April 8. It is 2018 GC5 at magnitude 20.4. Most asteroids in the image were moving about 30s of arc per hour. But the NEO was moving at ten times the speed of typical asteroids. Even with the lousy conditions, I could have picked it up if I'd known it was there, by tracking the asteroid rather than the stars. No distant galaxies were picked up as I normally do. Not necessarily because of conditions though I'm sure that had a bit to do with it. But the catalogs carrying these distant galaxies don't cover this part of the sky. Being in Virgo I found this surprising. Even with the poor transparency, I was able to easily pick out every galaxy NED had redshift values. None as dim as magnitude 20 let alone 23 that I often find. Still, on a better night how much more of the plume around HCG 064 would I pick up?


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

Related Designations for HCG064

HCG067

Hickson scoured the POSS plates and cataloged small compact groups of galaxies. One I found very interesting is #67 in the list. Interesting because Hickson and others got it wrong it appears! Probably because most work from the POSS plates which overexposed the core galaxy of the group hiding its true nature.

The group consists of two major galaxies, NGC 5306/VV135 and MCG -01-35-013. MCG -01-35-013 is a nice edge on, somewhat distorted, spiral. The southern arm is rather odd. The dust lane ends and suddenly the arm gets very narrow and blue. The transition is very sudden and unusual. The galaxy has not been studied that I could find.

NGC 5306 is where things go wrong. By all catalogs, NGC 5306 is the center "galaxy" with two others, north and south of it, not considered part of NGC 5306. The Vorontsov-Velyaminov Interacting Galaxies catalog, however, does include the galaxies to the northeast and southwest as they reside in a common halo. But all catalogs miss the fact that the core galaxy is actually two galaxies. NED doesn't show them separately nor does any catalog I could find. On the POSS 2 plates, they merge into one due to overexposure. Apparently, no one looked further. The VV catalog lists the pair as VV 135a as I've shown in the annotated image. The other two being c and b of course. NED classes NGC 5306/VV 135a as either S0 pec or E1. The NGC project says S0P? The redshift value like their classification is apparently a mash-up of that for both galaxies.

This field was recommended to me by Sakib Rasool so I contacted him to ask if he wanted me to image it because he suspected that NGC 5306/VV135 was a double galaxy. Nope, it came as a surprise to him as well--he's not easy to surprise. He was interested the spiral MCG -01-35-013 as it appeared warped or distorted on the POSS plates. After my email, he did some digging and contacted the astronomer John Hibbard, who studies interacting galaxies. Dr. Hibbard then did some digging and came up with one paper on it I'd not found. http://aas.aanda.org/index.php?option=com_article&access=doi&doi=10.1051/aas:1999513&Itemid=129

The paper labels it a double core galaxy; n1 and n2 which I labeled on the annotated image. But it goes on to indicate the authors feel these are two superimposed galaxies not as close as their angular separation indicates. I would agree with this as while the overall halo is oriented toward VV135b and VV135c, n2 is oriented almost at right angles to this. Oddly it is the brighter of the two, however. This would need some explanation it would seem. This is one group that needs a lot more study and some catalog asterisks or corrections.

VV 135b is classed as S0 pec. I don't know what causes them to tack on the peculiar label. VV 135c is classed Scd. It sure has some odd structure to it. Unfortunately, the structure is beyond my abilities to determine what it is. It certainly looks disturbed but somehow avoided the pec label.

A few other galaxies are scattered across the image that are members of the same group as HCG 67. Others are about twice as distant. The field is little studied with most galaxies being anonymous.

While the image is my usual size in pixel count it was taken at 0.5" per pixel rather than my normal 1" per pixel so covers only one-fourth the area of my normal images. As such, most of the remaining members of the group containing HCG 67 lie beyond the field of view. If I'd used my normal field it would have made a 4 times bigger image and too big for the Internet. Though now I wish I'd have taken the full field and reduced it to my normal scale of 1" per pixel, I'd have picked up almost a dozen other members of the group. I can't find any catalog entry for the entire group, just pieces of it. It is rather widely scattered. I was hoping to bring out a jet that one source says is coming from the nucleus of NGC 5306 but I don't see it. How they find such a jet yet miss it is a double galaxy I can't understand. I'm wondering if the "Jet" is really N2 sticking out of the overexposed blob they both make on the POSS 2 plates. Since it is already at a greater image scale than my normal cropped images I've not done one this time, just a cropped version for those who complain my images are too big.

Dr. Hibbard's email goes on to say about Hickson 67: "It appears to be the central concentration of a larger group with at least 15-17 members. About 10-15% of HCGs are thought to be such creates, and thus not true compact groups in the way Hickson meant.

"These double nucleated ellipticals are interested - they are sometimes considered examples of galactic "cannibalization". About 25% of cD galaxies have multiple nuclei (although I am not sure if NGC5306 is a full-blown cD; that requires it to have an extended luminous envelope). See e.g. http://ned.ipac.caltech.edu/level5/March02/Sarazin/Sarazin2_10.html.

"Well, back to work. Thanks for the diversion and beautiful image!"

For a bit there I thought I might have found something previously unknown. Nope, just something hidden deep in the literature. Still, finding something this obscure is quite exciting.

14" LX200R @ f/10, L=8x10'x1 RGB=2x10x2', STL-11000XM, Paramount ME

Related Designations for HCG067

HCG068

Hickson 68 is a galaxy group far larger than apparently Hickson realized. He made the catalog from visual inspection of the Palomar Observatory Survey Plates of the 1950's creating a catalog known as the Hickson Compact Group catalog. Well HCG 68 is not compact. He apparently was only considering the core region. The group is really far larger than my image. It is organized with elliptical galaxies in the center and spiral galaxies mostly on the edges many of which are beyond my FOV. The large spiral NGC 5390 is an example as is UGC 8841 in the lower left corner of my image. The group is located about 115 million light-years away in the constellation of Canes Venatici.

The center is home to the overlapping galaxies NGC 5353 and NGC 5354 which inhabit a common halo. NGC 5353 is an S0 galaxy rather than elliptical that harbors a rather active AGN indicating this might not be a serene old group like it first appears. NGC 5354 to its north is Classes SA0 with strong spectral lines and is a LINER galaxy. Yet more indication this is an active group still in its formative stage. Then there's NGC 5350 a rather classic looking barred spiral. NED classes it SB(r)b while the NGC project says SBb-c. It is a starburst galaxy with intense star formation going on in its core that is hidden from our view by warm dust. Yet another indication of activity.

Other NGC members of the group include NGC 5355, an E3 galaxy by NED and S0? by the NGC Project. NGC 5358 is classed SO/a by both. The other large member of the group in my image is UGC 08841 which is a very nice two armed barred spiral classed by NED as SBb.

NGC 5353 and NGC 5354 appear to share a common halo. It has a very weird sharp cut off at its southern end and appears slightly brighter right before it comes to that sudden end. This is often seen when a dark nebula abuts a bright nebula forming a shock front. I scoured the literature but found nothing addressing this odd feature. Closest I came was an article talking about how this is a still collapsing system with lots of activity to come over the next billion years. http://iopscience.iop.org/1538-3881/135/4/1488/pdf/aj_135_4_1488.pdf

This image is a complete reprocess from the very beginning of data taken back in 2008. When I processed it I included both color and luminance frames taken though clouds which cast a strong gradient across the image, While it was removed much of the halo, including the sharply defined southern end were gone. I through out all these frames and ended up with a much better image that now shows the halo's sudden southern end. Since the color data is weak I am a bit leery of it in faint regions like this halo. If it is right (a very big IF) then the plume has an odd red color as it comes to a halt. This is very weird if true. Is it really gas and dust ejected from the two massive S0 galaxies rather than stars? When galaxies of this size interact most dust and gas is ejected. Is that the source of the southern plume? I'm likely far off base here but what the heck, wild speculation is fun. If anyone finds anything to cut though my wild guesses please let me know and I'll pass it on.

This image was taken with my old, halo prone filters. The bright K5 star really made a mess with my old filters. I left a lot of it in as I found no way to take it out without harming the faint halo around the core galaxies. But compared to the Sloan image of this area I did a much better job with it than they did. I need to reshoot this with more time with the new filters that don't have the halo issue.

The image was taken over 4 nights (one night, while used in the first image was rejected for this one). Many other frames from the other three nights were rejected as well. The result was I am down to my normal 40 minutes of L and 20 for each color. Not what is needed for such a faint feature as the plume, unfortunately. Nor was the night very good. My limiting magnitude is about 21.8 compared to my normal 22.5. That would indicate poor transparency even for the three nights I got usable data. Yet another reason to reshoot it. For now, this reprocess is a great improvement over the original so I'll go with it.

I retook this along with NGC 5371 omitted from this framing. See it for a better image. Unfortunately, it missed the plume.

14" LX200R @ f/10, L=4x10' RGB=2x10'x3, STL-11000XM, Paramount ME

Related Designations for HCG068

HCG069

HGC 69 is a group of 4 galaxies in western Bootes about 400 million light-years distant. Hickson groups, of which there are 100, must meet 4 requirements.

1. There must be 4 galaxies or more with a similar brightness that are brighter than 26.0 surface brightness per square second of arc.

2. The group must be isolated, not a small section of a larger group or cluster.

3. The group has to be so compact their relative sizes are similar to the distance between galaxies themselves.

Oddly, HCG 69 appears to break rule 2. There are a lot of galaxies, larger and smaller in angular size, in the image that are all (including HCG 69) part of a much larger group of galaxies. Note however Hickson doesn't say they all have to be at a similar distance. At the time of his listing, distances weren't all that well known. In fact, the first compact group known, Stephan's Quintet (HGC 92), has one member that's much closer than the others. All Hickson required was they visually appear likely to be at the same distance. In the case of HCG 69, they really are.

They are PGC 49499, 49502, 49505 and 59507. Hickson assumed many of his groups would show gravitational interaction when studied in detail. It's quite obvious from just my image that HCG 69A, PGC 49502, is highly distorted. It and HCG 69C, PGC 49505, are passive nucleus galaxies. A definition of them I found reads: "Passive nuclei (PAS) are typically red, contain exclusively old stars, with no star formation activity: their spectra show both H± and [NII] in absorption. Thus the cores are red and dead though some I've found have jets so not totally dead. No jet is seen in these, however. Also, the entire galaxy need not be dead. HCG 69A has a blue star plume to the southwest indicating it is still forming new stars in that part while much of the rest is rather red. Thanks to this plume it is a huge galaxy which I measure at 194,000 light-years across. Note too that it has a very faint plume going north and a bit easy that goes past PGC 49499. This may indicate the path of yet a 5th galaxy it ate over hundreds of millions of years ago.

Many of the other galaxies associated with the same group as HGC 69 are also rather red and dead with a few exceptions such as ASK 538092.0 to the north of HGC 69 which is quite blue and very actively forming stars throughout as is LEDA 1723672 to the west.

There are 6 IC galaxies in the image 4343, 4344, 4345, 4346, 4348 and 4349. Redshift puts IC 4348 70 or so million light-years further away so it may not be related. The rest, however, are certainly members of the group that contains HCG 69. All 6 were discovered by Stephane Javelle on June 15, 1895.

There's an interesting pair of possibly interacting galaxies to the east-southeast of HCG 69. I found a redshift for only the southern galaxy. So are they interacting or is one well in front of the other so no interaction is possible? Wish I knew.

A quasar to the southeast is listed as having Damped Lyman Alpha emission. For what this means, see: https://en.wikipedia.org/wiki/Damped_Lyman-alpha_system

The stars are a bit flat on the bottom due to tube currents. Normally I let the scope cool to avoid these for an hour before imaging but this night was threatening rain so I didn't open the roof when suddenly the skies cleared with just enough time for one object. That left no time for cooling. I hoped the drizzle had helped cool the scope to ambient but this image showed that didn't happen.

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

Related Designations for HCG069

HCG070

HCG 70 is a group of 7 galaxies in southeastern Canes Venatici. 3 of the galaxies are about 380 million light-years distant and 4 are about 850 million light-years distant so are really members of two groups. Hickson ignored distances when making up his list of compact groups. It was purely based on the visual impression much like Arp's galaxies were classified by visual impression rather than what was really going on. In both cases there just wasn't enough information at the time to take it any further. As for HCG 70, the two groups are made up of many more galaxies scattered around my image. Just that they were too faint or far from the center to be included in Hickson's group. There seems to be yet another group at about 700 million light-years in the field as well though I found no designation for any of these groups.

Only three of the galaxies in the Hickson group carries an IC number with none being in the NGC. The IC galaxies are IC 4369, 70 and 71. All three were discovered by Stephane Javelle on July 3, 1896. Oddly the most obvious member, UGC 8990 was not seen nor the other three in the group. Apparently, UGC 8990 isn't as visually obvious as my image makes it out to be. Though Seligman notes that it was seen as a 14th magnitude star. At least Javelle mentions such a star near to IC 4370 without mentioning the direction or distance. The galaxy's core reads 14th magnitude on my image with nothing else qualifying it seems he saw the galaxy but didn't recognize it. Many stars found their way into the NGC and IC, in this case, a galaxy may have been omitted because it was thought to be a star. I wonder how many others like this were missed.

Some of the field galaxies that caught my eye are ASK 539170.0 at 780 million light-years to the southeast. Is it a rapidly moving member of the group at 850 million light-years, a slow one in the 700 million light-years group or neither? It has an odd red region on its west side I thought was noise but it shows in the SLOAN image as well along with the dark band further to the west. Those are real features not noise or due to bad processing as I first suspected.

Another that caught my eye is PGC 050150 which is listed as a compact galaxy though to my eye it is a rather normal spiral. Further west is ASK 539107 a rather kidney shaped galaxy due to its disk being mostly east of the core and arms.

But strangest of all is ASK 539102.0 to the far southwestern corner. It has two huge sprays to either side of its core. It almost appears as two objects the core and the arc. It is part of the group in the Hickson group at the larger distance.

Quite a few rather bright galaxies have no redshift values at NED so aren't noted in the annotated image. CQ denotes a candidate quasar. NED lists it first as just a star which usually means it isn't all that certain it qualifies as a quasar. In this case, there is a spectroscopic redshift that seems to pretty much say it is a quasar. There may be some reason to question its value they don't mention. If the redshift is correct it would likely seem to be a quasar as what else is that bright at over 11 billion light-years?

This night was awful due to clouds. My system caught that one of the luminance images was unusable and took a fifth to make up for that bad one. When I went to process it I found yet another bad one I couldn't include without hurting the image the system failed to retake. Both were similar and I still don't know why it never retook it. If it was because it had moved beyond my 2 hour limit from the meridian it would have rescheduled it but that didn't happen either. So this image is, even more, data starved than normal which is sad as there are several faint features to these galaxies that would have benefited from even more time than I tried to take. Conditions for the color data continued down hill. I tried to make a pseudo luminance using the color data but that just drug the image down further. So it is yet another for the reshoot list for next year.

14" LX200R @ f/10, L=3x10' RGB=2x10' (not even equal to one 10 minute color frame on a good night), STL-11000XM, Paramount ME

Related Designations for HCG070

HCG075

HCG 75 is a tight group of 8 galaxies in northwestern Serpens Caput about 550 to 590 million light years distant. One has no distance estimate. Are they really at the same distance or is this just an illusion due to our perspective? I found no non-redshift distance estimates to help here. It is rather likely they are at about the same distance and the difference in redshift values is due to their relative motion around a common center of gravity. Assuming they are about the same distance the group is a bit over 400,000 light-years across. Close enough that I'd expect to see some rather noticeable interaction. While A and B overlap I don't really see any interaction and the others show none other than H is an irregular blue galaxy but this may just be its nature. With no distance estimate of any type, G may be a distant background galaxy of which many are in the image.

While A is the brightest of the galaxies in the group and likely the most massive, B has the largest diameter, which I measure at about 160,000 light-years. I measure A at about 95,000 light-years in size though this is a guess since it is partly lost either behind or in the glare of galaxy B. So I measured the southeastern half and doubled that for a size. Being a tightly packed ball of stars it likely has more mass than the larger disk of galaxy A.

Galaxies G and H are listed at NED as being dwarf candidates. If G is a true member of the group it is a small spherical galaxy about 16,000 light-years across so would be a dwarf. H, however, is much larger, being almost 50,000 light-years across. Far too large to be considered a dwarf. Maybe it got this possible classification before its distance was known. But then it would have had to be considered much closer than the others in the group or else others would have to be dwarf galaxies as well and none are listed that way.

Three other galaxies to the north, northwest and southwest of the group have similar redshifts so are likely members of this group. There are 5 other galaxies near A to the west that may be dwarf members or distant background galaxies. Without redshift data, I can't tell which they are. All these, but for H are red and dead galaxies. In fact, most of the galaxies in this field are red and dead galaxies.

While this field was shot through clouds of varying thickness I think the colors are not far wrong. EXcalibrator said red had to be toned down to get the spectral colors of the stars right, this adjustment wasn't severe. I believe colors to be close to correct. Clouds did limit color in very faint stars and galaxies. Green was hit the worst but most easily compensated for. All bright stars had strong green halos which Hasta La Vista green easily eliminated. Imaging through clouds has been a near constant problem this spring. I'm getting used to it.

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

Related Designations for HCG075

HCG076

Seeing turned poor this night. I searched for something I thought could sort of survive the bad seeing and chose the Hickson 76 group as it consisted of mostly featureless galaxies. Not checking further I put it on the schedule and went to bed. Seeing got worse and it turns out this field was far more interesting than I expected. Now too late to redo it this year I went ahead and processed this low resolution mess. I'll try again next year.

What I didn't realize is that HCG 76 forms the core of the ABELL 2085 galaxy cluster at a bit under a half billion light-years. This cluster virtually fills my field. HCG 76 itself consists of 7 of the brighter members in the core of the ABELL cluster. Three are NGC objects. There is some controversy over 2 of these. It's too long to go into here so I'll just let you look it up at this link: http://www.ngcicproject.org/NGC/NGC_59xx/NGC_5941.htm . The link may be temporary. It is to the NGC Project which shut down upon the death of the fellow administering it. A temporary version is online as I write this. If it changes once the site has been fully restored it shouldn't be hard to find the entry.

In short, I followed the above site for designating the three NGC galaxies in the HCG group even though that puts NGC 5941 east of NGC 5942 so out of RA order. Seligman follows the same system but makes no mention of its problems.

The other NGC galaxy in the frame is the biggest and brightest. It is NGC 5940 and the lone bright, face on spiral. It has a rather odd arm structure on the east side that creates the appearance of a dark vertical stripe or dust lane. I think it more to do with the odd arm structure than obscuring dust. I measure its size at about 130,000 light-years.

All 4 of the NGC galaxies were discovered by Lewis Swift on April 19, 1887. Unfortunately, his positions tended to be rather vague leading to the identity confusion.

The field contains the usual mix of objects that are labeled in the annotated image. To the upper left is an object that is listed as both a galaxy and a quasar. It has a fuzzy image on the SLOAN image with a size greater than that for a point source quasar. Apparently, it is a quasar that doesn't outshine its host galaxy allowing a bit of the galaxy to be seen. It helps that it is about half the distance of most other quasars.

Seeing was very poor. I probably should have reduced it to 1.5" per pixel from my normal 1" per pixel but that made the annotated version hard to read so left it at a very fuzzy 1" per pixel.

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

Related Designations for HCG076

HCG079

This was the most compact group of galaxies known when Seyfert discovered it in 1951. The group consists of only 5 rather than 6 galaxies like the name implies. 4 of them are about 200 million light-years away. The fifth, the small spiral to the east side under others, is well over 4 times as distant so not a member of the group. Three of the group appear to be interacting, the easternmost so distorted it was thought to be two galaxies giving rise to the 6 galaxy count. The extra galaxy is just a large plume, however. The group was first recorded by Édouard Stephan as one galaxy which went into the NGC as NGC 6027. The individual galaxies carry their own letter designation but that varies from catalog to catalog with some using lower case letters and others upper case. All have PGC numbers but again I find some disagreement as to which is which. A quick calculation shows the interacting galaxies occupying an area of space only slightly larger than our galaxy. I do find the southern blue galaxy odd. I suspect it isn't interacting nearly as strongly with the others, if at all.

This is one of my early 2007 images when I did no research on my images though I see I tried to do some for this one and got lost in the various naming conventions I ran into. I don't have time to fight it right now. I'll just add that the galaxy on the far left of my image is PGC 56636. It is at about the same redshift as 4 closer members of HCG 79 so likely part of their local group.

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

Related Designations for HCG079