Observing Hickson and Abell clusters at Lake Sonoma September 18 20, 24

by Jane Houston Jones

I was inspired by Ray Cash to tackle this project. Ray's Hickson page, up for many years now, is a wonderful source of information and inspiration. Plus Ray lent me his own copy of Paul Hickson's 1994 Atlas of Compact Groups of Galaxies a few months ago. I put some of Paul Hickson's object descriptions in with my observing report. So the interesting bits are from Dr. Paul , not me. :-) To me, observing these objects is just a small part of their appeal. Knowing something about why Paul Hickson chose them for study and what is going on within these galaxy groups adds to their attraction as an amateur astronomer observing project. As you can see from Ray's website, they make interesting imaging targets as well! The Astronomical League's project booklet is also helpful.

Hickson Compact Galaxy Groups

Hickson 2 in Pisces, RA: 0h 31m 30.0s Dec: +08 25' 52". A trio of galaxies plus a fainter member H2d, mag 16.1 which has a much higher redshift that the other three. (Paul Hickson). H2a, b, c seen. Line of three mag 12 stars point right to the cluster. In fact H2b, Markarian 553 or PGC 1914 is 3 degrees S of the line of Orion belt appearing group of stars. H2a=PGC1921 mag 13.9 - elongated. H2b=Markarian 552 mag 14.5 just glimpsed, H2c= PGC1927 mag 15 oval. Did not see H2d, PGC1934 mag 16.1.

Hickson 5 in Pisces RA: 00h 38m 34.1s Dec: +07 03' 49". This is a striking group consisting of a compact triplet formed by the overlapping pair of galaxies NGC190N/S and a nearby companion, plus a small low-redshift galaxy. Galaxy "a" has well developed, but distorted, spiral arms. A luminous envelope encompasses all 4 galaxies. The triplet has a relatively low velocity dispersion and mass-to-light ratio. (Paul Hickson) I saw one object which is a combo of H5a= NGC190 , mag 14.5 and H5b=NGC190a, mag 15.5. Couldn't "bust" them apart. Too bad I couldn't see components C and D in the 16th mag range. The foursome forms a nice linear group. These Hicksons would make a neat imaging project, since they are interesting to study, pretty to look at and difficult to see.

Hickson 7 in Cetus RA: 00h 39m 23.9s Dec: +00 52' 41". 4 bright spiral galaxies all of which show some degree of distortion or asymmetry with may be attributed to gravitational interaction. (Paul Hickson) 4 galaxies, 3 seen one imagined. :-) Skytools 2 has these galaxies misidentified, but my observing notes show H7a=NGC192 to be elongated and the brightest at mag 13. H7b=NGC196 and is also oval. NGC201 is H7c mag 12.6. I suspect I saw NGC 197 or H7d at mag 14.7 in-between a and b. Nice and easy starhop from Delta Pisces and a line of stars which point right to H7.

Hickson 8 in Andromeda, RA: 00h 49m 36.8s Dec: +23 34' 51". 4 components, 1 seen. Clump of galaxies suspected but I couldn't confirm it. This is a quartet of galaxies, with one elliptical. The brightest one H8a, PGC2886 is peanut shaped ellipse (not my observation, but from Paul Hickson's book) and he thinks it might be due to dust or that the galaxy is a relic due to a recent merger between two galaxies. H8a was the only one I saw. The other three, H8b is PGC 2888 mag 16.2, H8c is PGC 2890 mag 16.1 and H8d is PGC 2892 mag 16.2. This was a mag 15 and under observing night.

Hickson 20 in Aries, RA: 02h 44m 15.0s Dec: +26 06' 11". A small group of 6 compact early type galaxies. Despite its small size, the group has a higher than average velocity dispersion. As a result, the orbital time-scale (crossing time) is very short, about one one-hundredth of the age of the universe. (Paul Hickson) wow! 2 "clumps" seen :-). Each clump is a grouping of three galaxies. H20a=PGC 10364 is 16.7 and lies right along a trio of stars. Stars easy to see, and then a clump of H20a, b, and c. All mag 16. Then right next to this clump is another clump of three more mag 17 and 18 galaxies, D, E and F. I think I saw a clump but not sure now I know the magnitude.

Hickson 78 in Draco RA 15h 48m 28.0s Dec: +68 12' 28". This quartet contains only 2 galaxies - a and b - having accordant redshifts. The brightest of the two is an infrared source. 4 components, 3 seen, a, b, and c ( PGC 56079, 56067 and 56095) all mag 15. Mag 16.8 PGC 56086 not. Seen with the aid of Skytool2 eyepiece charts customized for my telescope and eyepiece, otherwise forget it.

Hickson 80 in Draco, RA: 15h 59m 12.3s Dec: +65 13' 33". This is a small quartet of late-type galaxies. The brightest is a radio and infrared source. Galaxy C has an unusual shape. B has faint spiral arms and A has a warped disk. (Paul Hickson) 4 components , 1 seen. H80A=PGC56588 is mag 14.8 with the warped disk. It also has two same mag stars imbedded, which made it hard for me to see what was going on in the galaxy.

Hickson 81 in Hercules RA: 16h, 18m 13.0s Dec: +12 47' 39" 4 components, I tried, no luck

Hickson 82 in Hercules RA 16h 28m 22.0s Dec: +32 49'25", 4 components, 3 seen. H82a=NGC 6162 mag 14.oval. H82b=NGC6162 also oval mag 14.6. H82c is NGC 6161 mag 14.8 oval. Nice group, sorry I didn't see the 4th mag 16 PGC 58231. C is a radio and infrared source (Paul Hickson)

Hickson 83 in Hercules RA 16h 35m 40s Dec: +06 16'12", 5 components, no see um. Paul Hickson says this distant group resembles a small cluster of galaxies, however the 5 brightest galaxies satisfy the selection criteria of a compact group. The system has a high velocity dispersion and relatively large intergalaxy separation. Many small faint galaxies appear in the image. Imagers please??

Hickson 85 in Draco RA: 18h 50m 22.3s Dec: +73 21' 00" 4 components, 1 seen - H85a=PGC 62476 mag 15.oval glow. Paul Hickson says this is a radio source.

Hickson 87 in Capricornus, 4 components and 3 seen, and showed to others. This one was near Neptune Saturday night, yes in the bikini bottom constellation of Capricornus. A nice trio of mag 6 and 7 stars point right to the galaxy cluster. I actually showed this to the nearby observers Saturday night, and I looked at it all three nights. H87a =PGC65415 mag 15.2 long spiral edge-on. Two stars of mag 14/15 range bisect the cluster. H87b=PGC65409 is mag 15.5 oval. H87c is PGC65412 is mag 16 and not seen is faint and small h87d, PGC849368 at mag 17.7.

Hickson 89 in Aquarius, RA:21h 20m10.8s Dec: -03 54' 33". A loose quartet of spiral galaxies. H89a=PGC 66570 mag 14.1 slightly elongated. 2 mag 14 stars and a mag 11 star make a line with H89a in-between. H89b=PGC 66580 mag14.9 seen thanks to a mag 12 star plotted on the Skytools2 chart..

Hickson 100 in Pegasus, RA: 00h 01m 20.7s Dec: +13 07' 57", 5 components, 2 seen, Skytools2 has the galaxies misidentified.. The brightest H100a is a radio and infrared source. H100A=NGC7803 mag 13.7 is the brightest.oval. H100b also seen is Markarian 934 at mag 15.3. Some stars on the Skytools2 charts made it easy to find the galaxies.

Abell Galaxy clusters

AGC 2162 in Corona Borealis RA 16h 12m 30.0s Dec: +29 32'00" Sspotted two galaxies, NHC 6085 mag 14.4 and NGC 6086 mag 13.9.

AGC 2256 in Ursa Minor RA: 17h 03m 42.0s Dec: +78 43' 00" spotted a clump of galaxies, need more time on these. Saw NGC 6331 mag15.4 and unidentifiable clumps for another night.

AGC 426 in Perseus RA 03h 18m 36.0s Dec +41 30' 00". Seeing softened as Perseus rose high enought to study, but I did spot the Perseus A radio source, NGC 1275 at mag 12.7 and nearby mag 13 NGC 1272. That was enough for now. but not enough of Abell 426.

Other archived Hickson reports if this interests you:

• May 23, 25, 26, 2003: http://www.observers.org/reports/2003.05.23.4.html
• May 31 2002: http://www.observers.org/reports/2002.06.01.5.html
• May 2002: http://www.observers.org/reports/2002.05.31.3.html

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