Hickson Compact Galaxy Groups (32 Photos)
There are 100 groups of galaxies in the Hickson catalog. Each Hickson cluster contains 4 to 8 galaxies whose magnitudes range from 11.5 to 18.4. The galaxies are often identified by the letters “a”, “b”, “c”, “d”, “e”, “f”, and “g.” Here is a helpful resource about the Hicksons written by Reiner Vogel. Here is a link to Paul Hickson’s original article about the collection in the Astrophysical Journal.
The Astronomical League publishes a very helpful book for this program called Galaxy Groups and Clusters (see here). Using this book and the plate solving and annotation scripts in Pixinsight, I attempted to locate all the components of the 30 required clusters and annotate them with their lower case identifiers and catalog numbers.
If you “mouse over” one of the Hickson photos, a zoomed in view of the cluster should appear to the right. You can move the mouse around to view closeups of different areas of the photo. If you click on the main photo, you can see an enlarged image of the entire field of view. NB: For some reason the addition of the mouse over zoom creates some spacing problems I was unable to solve. Sorry.
I realize that in some cases the photos are dim, fuzzy, or grainy, especially when zoomed in. A number of things contribute to this. First, as astro photos go, these are very short exposures. Longer exposures yield more detail. Atmospheric distortion and moonlight also contribute, as does the magnitude of the objects; in many cases they are very dim. Indeed, in a couple of cases, the magnitudes of individual cluster components exceeds the limiting magnitude of the scopes used for this program.
The magnitude problem evidences itself in another way, as can be seen in Hickson 72. This cluster has six components; the “f” galaxy is magnitude 17.9. No matter much I enlarged and tweaked the photo, I could not resolve either the “e” or “f” galaxies. Some form of this problem occurred 10 times in the Hickson photos. I note the missing components in the commentary about the photo. In all cases I went ahead with the annotation if I saw even a hint of light. My rule of thumb became, if there is nothing there, don’t annotate it!
To keep the annotation clutter to a minimum, I abbreviated the catalog names. I believe this is the same convention used in Galaxy Groups and Clusters: N stands for NGC, U for UGC, P for PGC, I for IC, and M for MGC.
While these are not “pretty” astro photos, I hope that they do some justice to the Hickson clusters. The information line below each photo contains the Hickson designation, the scope used, the date and time (UTC) of the photo. For the exposure lengths, please refer to the Notes section.
Click on the photo to see a larger image. “Mouse over” it to get a closeup view.
1. Hickson 41 — C 3 / 2020-06-08 / 22:45 The large, bright star to the right of the P 28784 annotation is SAO 43117. [SAO 43117 / UGC 4364 / Star Unit Ratio = 875,000]
2. Hickson 44 — C 3 / 2020-06-08 / 22:48 The bright star to the right of the component b annotation is SAO 81279. [SA) 81279 / NGC 3193 / Star Unit Ratio = 468,085]
3. Hickson 45 — C 3 / 2020-06-09 / 23:08 There is a chain of stars off the cluster at about 8 o’clock. The brightest of them is SAO 27612. [SAO 27612 / UGC 5564 / Star Unit Ratio = 1,162,791]
4. Hickson 46 — C 3 / 2020-06-13 / 21:41 All four of the annotated galaxies are at least mag 16.1, very near the limiting magnitude of this scope.
5. Hickson 51 — C 3 / 2020-06-09 / 22:51 I was unable to identify the f component — P 3490. At about 4 o’clock from the cluster, there is a trapezoid shaped set of four stars. The brightest of the four, at the lower left of the asterism, is SAO 81784. [SAO 81784 / NGC 3653 / Star Unit Ratio = 1,000,000]
6. Hickson 53 — C 3 / 2020-06-08 / 22:36 The bulk of the cluster forms a chain. Follow the chain down and left, and you can see IC 700. Straight above component a, about halfway to the top, there is a nice little “flatty” — PGC 1642956.
7. Hickson 58 — C 3 / 2020-06-09 / 23:03 Components a, b, and c form something of a straight line. If you follow it to the left, you will see a more or less edge on galaxy that “stands perpendicular” to the line. That is NGC 3833.
8. Hickson 61 (“enlarge” and “zoom” features not working.) — W / 2020-06-08 / 07:45 These are often referred to as the “box galaxies” because they form a near perfect rectangle.
9. Hickson 72 — SC 2 / 2020-06-06 / 01:39 I was unable to identify two components: e (U 9532) and f (P 52849).
10. Hickson 79 — C 3 / 2020-06-05 / 21:19 I was unable to identify two components: d (M+4-38-7) and e (M+4-38-9).
11. Hickson 83 — SC 2 / 2020-06-08 07:45 I was unable to identify the e component — P 58561.
12. Hickson 65 — SC 2 / 2020-06-15 / 03:45 If you follow the line of the annotation for the b component to the left, near the edge of the frame you can see PGC 159133 at mag 16.0.
13. Hickson 76 — SC 2 / 2020-06-15 / 03:55 Just above the “4” in the annotation for the c component, there is a very small “faint fuzzy.” That is magnitude 16.5 galaxy PGC 1320598. My photo of this cluster matched quite nicely with the stars on the DSS Chart on p. 48 of the GGC book. However, the placement of the some annotations on the DSS Chart did not match up with the annotations on my plate solved image. (I ran it several times and on two solvers.) My plate solved photo agrees with the placement of components “a”, “e”, “f”, and “g”. However, “b”, “c” (which is actually missing on the DSS Chart) and “d” are different. Below is a copy of my plate solved photo of the cluster. I think that the line at the top of the p. 48 of the GGC book lists the components in an incorrect order, and I think the correct identifier is “M+1-40-2” not “M+1-40-3”. This may explain the confusion. I used my placements in the photo I posted.:
14. Hickson 77 — SC 2 / 2020-06-15 / 04:10 I was unable to identify the d component — P 56125. To the upper right of the cluster is PGC 56094. I managed to keep the color in this one and it paid off!
15. Hickson 88 — SC 2 / 2020-06-15 / 03:50 The large, bright bluish-looking star in the upper right quadrant of the frame is 5 Aqr shining at mag 5.6 [5 Agr / NGC 6978 / Star Unit Ratio = 446,154]
16. Hickson 62 — C 3 / 2020-06-18 / 21:48 If you follow the line of the annotation for component c to the right, you run into NGC 4703. If you go back to the cluster and run a line down and right to about 4 o’clock, you can see two additional galaxies in close proximity, NGC 4716 and NGC 471.
17. Hickson 73 — C 3 / 2020-06-19 / 00:23 Near the top of p. 47 of the GGC book, I believe there is a typo. Component b should be listed as “IC 4526” not “IC 4826.”
18. Hickson 82 — C 3 / 2020-06-18 / 21:55 The bright star just to the right of the cluster is SAO 65320. [SAO 65320 / NGC 6162 / Star Unit Ratio = 964,912]
19. Hickson 43 — C 3 / 2020-06-19 / 22:08 The brightish star above the a component is HD 88392. [HD 88392 / PGC 29666 / Star Unit Ratio = 938,776]
20. Hickson 49 — C 3 / 2020-06-19 / 22:18 This photo presented a problem unlike any other in this program. Hickson 49 is made up of four components: a being C314-1; b being PGC 32895; c being PGC 32893; and d being PGC 32890. I was unable to identify the catalog associated with component a. More frustrating, the cluster is so dense that I could not determine which of the galaxies are which. I know that cluster I am pointing to here contains: PGC 32895, PGC 32890, PGC 32899, and PGC 32893. I include a screen shot from the solved photo below to illustrate the problem (mouse over to enlarge).
.
21. Hickson 52 — C 3 / 2020-06-19 / 22:26 If you look closely at the lower left side of the photo, you can make out NGC 3697, at about 8 o’clock.
22. Hickson 55 — C 3 / 2020-06-19 / 22:31 I was unable to identify the e component — M+12-11-28E. NGC 3735, a lovely “flatty,” dominates the lower right quadrant of the frame.
23. Hickson 56 — C 3 / 2020-06-19 / 22:48 I was unable to identify the d component — P 35615. Note the two larger galaxies above the cluster. The one on the right is NGC 3718 and the one on the left is NGC 3729.
24. Hickson 54 — C 3 / 2020-06-20 / 22:18 I was unable to identify three components in this photo — b (P 35380), c (P 35384), and d (P 35385). Just above the “a” designator there is a nice elliptical; it is NGC 3697.
25. Hickson 60 — C 3 / 2020-06-20 / 23:35 The a component is mag 15.0. The remaining galaxies are at least mag16.0, near the limiting magnitude of this scope.
26. Hickson 66 — C 3 / 2020-06-21 / 00:15 The large star below the component b annotation is CQ UMa. [CQ UMa / PGC 48222 / Star Unit Ratio = 3,367,003]
27. Hickson 68 — C 3 / 2020-06-21 / 00:23 The largest galaxy by far in the frame is the one just above the “d” in the d component. That is NGC 5371 and is not a component of Hickson 68.
28. Hickson 35 — C 3 / 2020-06-20 /T22:09 I was unable to identify the f component — P 24600. This galaxy is mag 18.1 and is likely beyond the limiting magnitude of this scope.
29. Hickson 64 — C 3 / 2020-06-20 / 23:41 I was unable to identify the d component — P 46971. It is mag 17.2 which is beyond the limiting magnitude of this scope.
30. Hickson 57 — C 3 / 2020-06-20 / 22:23 This cluster is sometimes referred to as Copeland’s Septet. Oddly, Hickson 57 has eight components, not seven. Copeland did not include the h component in his collection.
31. Hickson 59 — C 3 / 2020-06-20 / 22:31 I was unable to identify two components — c (M+2-30-41) and d (IC 737). On p. 43 of the GGC book, the DSS image of this cluster is missing some components, and the c component is repeated. The annotations on the DSS image did not match those with the plate solves I did. I used my plate solve information to annotate this cluster.
32. Hickson 47 — C 3 / 2020-06-20 / 22:14 At the top of the frame in the center, there is a nice edge on spiral galaxy in a vertical position. That is PGC 30630.
End of Page