Observation of galaxy cluster Abell 4038

Observation of galaxy cluster Abell 4038
By Steve Gottlieb

Last month I took a look at the galaxy cluster Abell 4038 in Sculptor and was surprised to find 11 galaxies within a 30' field. Although this cluster is not well known, it's a cinch to find, with the central core about 15' west of naked-eye Delta Sculptoris (V = 4.5).

Four of the members (IC 5350, IC 5353, IC 5354, IC 5358) were discovered by Lewis Swift in 1896 observing with a 16" refractor from Echo Mountain above Los Angeles while Herbert Howe found IC 5349 a couple of years later from Chamberlin Observatory in Colorado with a 20" refractor. There are several faint galaxies (listed in the PGC) which I didn't pick up including PGC 72393, 72451, 72464, 72473 and 72476 which should be visible in a larger scope or better southern horizon.

The following observations were made with a 17.5" f/4.4 at 220x and 280x from the Sierra foothills above Plymouth, California with a naked-eye limit of 6.5. The listed positions are from the GSC and the data from RC3 when available.

Steve Gottlieb
NGC/IC Project

Components of Abell 4038
Name RA Dec Data Description
IC 5349 = E471-011 = M-05-56-005 23 46 23.0 -28 00 15 V = 14.2; Size 0.9x0.2; SB = 12.3; PA = 20d very faint, small, elongated 2:1 SSW-NNE, weak concentration. Required averted to initially view but with concentration can almost hold continuously. Located at the W end of Abell 4038 (first of 11 viewed).
IC 5350 = E471-014 = M-05-56-009 23 47 14.7 -27 57 28 V = 13.4; Size 0.7x0.6; SB = 12.5 faint, very small, round, increases to a very small brighter core and stellar nucleus. Forms the vertex of an isosceles triangle with a mag 10 star 5' N and a mag 11 star 4.5' ESE. Located about 10' N of the central core trio IC 5353, IC 5354 and IC 5358.
IC 5353 = E471-017 = M-05-56-010 23 47 28.6 -28 06 33 V = 13.0; Size 1.4x1.0; SB = 13.3; PA = 140d very faint, fairly small, irregular shape, halo grows in size with averted vision, weak concentration to a brighter core. Located in the core with IC 5354 1.6' S and IC 5358 3.9' SE. A mag 11 star lies 4' NE and a mag 15 star is 1.0' NNE.
IC 5354 = E471-016 = M-05-56-011 23 47 28.6 -28 08 09 V = 14.0; Size 0.8x0.4; SB = 12.6; PA = 66d extremely faint, very small, round. A faint companion at the NE edge was not seen. Located just 1.6' S of IC 5353 and 3.5' W of IC 5358.
PGC 72437 23 47 43.2 -28 08 38 very faint, very small, nearly stellar nucleus. Forms a close double system with IC 5358 just 20" between centers! At moments both cores were clearly resolved.
PGC 72436 23 47 43.4 -28 10 22 extremely faint, round, 15" diameter. Glimpsed for moments 2.0' S of IC 5358 in the core of Abell 4038. Verified on a GSC finder chart and then reobserved.
IC 5358 = E471-019 = M-05-56-013 23 47 44.2 -28 08 22 V = 12.6; Size 2.5x1.0; SB = 13.6; PA = 122d initially seen as a single irregular-shaped galaxy but after careful viewing this double system was resolved into two nearly tangent objects oriented WSW-ENE (the brighter, larger object to the NE is IC 5358). At moments both objects can be seen to have nearly stellar nuclei. Located 16' W of Delta Sculptoris (V = 4.5).
M-05-56-015 = PGC 72450 23 47 56.1 -28 19 16 V = 14.4; Size 0.7x0.5; SB = 13.1 extremely faint, very small, round. Requires averted to glimpse. This difficult member is situated about 12' S of the central group.
PGC 72466 23 48 20.7 -28 13 54 very faint, round, 15" diameter, can hold continuously with averted vision. Located 2.7' SSE of a mag 11.5-12 star and 10' SE of Delta Sculptoris on the SE side of the cluster.
PGC 72469 23 48 21.1 -28 06 58 extremely faint, round, 25" diameter, low surface brighness. Picked up 2.5' SSW of brighter PGC 72471. Located 7.6' W of Delta Sculptoris (doesn't interfere with viewing).
PGC 72471 23 48 23.3 -28 04 29 very faint, round, 20" diameter. This faint member was picked up 8' NW of Delta Sculptoris and 1.2' SSW of a mag 13.5 star and then verified on the GSC finder chart. Nearby PGC 72469 lies 2.5' S.

Name	RA	Dec	Data	Description
IC 5349 = E471-011 = M-05-56-005	23 46 23.0	-28 00 15	V = 14.2; Size 0.9x0.2; SB = 12.3; PA = 20d	very faint, small, elongated 2:1 SSW-NNE, weak concentration. Required averted to initially view but with concentration can almost hold continuously. Located at the W end of Abell 4038 (first of 11 viewed).
IC 5350 = E471-014 = M-05-56-009	23 47 14.7	-27 57 28	V = 13.4; Size 0.7x0.6; SB = 12.5	faint, very small, round, increases to a very small brighter core and stellar nucleus. Forms the vertex of an isosceles triangle with a mag 10 star 5' N and a mag 11 star 4.5' ESE. Located about 10' N of the central core trio IC 5353, IC 5354 and IC 5358.
IC 5353 = E471-017 = M-05-56-010	23 47 28.6	-28 06 33	V = 13.0; Size 1.4x1.0; SB = 13.3; PA = 140d	very faint, fairly small, irregular shape, halo grows in size with averted vision, weak concentration to a brighter core. Located in the core with IC 5354 1.6' S and IC 5358 3.9' SE. A mag 11 star lies 4' NE and a mag 15 star is 1.0' NNE.
IC 5354 = E471-016 = M-05-56-011	23 47 28.6	-28 08 09	V = 14.0; Size 0.8x0.4; SB = 12.6; PA = 66d	extremely faint, very small, round. A faint companion at the NE edge was not seen. Located just 1.6' S of IC 5353 and 3.5' W of IC 5358.
PGC 72437	23 47 43.2	-28 08 38		very faint, very small, nearly stellar nucleus. Forms a close double system with IC 5358 just 20" between centers! At moments both cores were clearly resolved.
PGC 72436	23 47 43.4	-28 10 22		extremely faint, round, 15" diameter. Glimpsed for moments 2.0' S of IC 5358 in the core of Abell 4038. Verified on a GSC finder chart and then reobserved.
IC 5358 = E471-019 = M-05-56-013	23 47 44.2	-28 08 22	V = 12.6; Size 2.5x1.0; SB = 13.6; PA = 122d	initially seen as a single irregular-shaped galaxy but after careful viewing this double system was resolved into two nearly tangent objects oriented WSW-ENE (the brighter, larger object to the NE is IC 5358). At moments both objects can be seen to have nearly stellar nuclei. Located 16' W of Delta Sculptoris (V = 4.5).
M-05-56-015 = PGC 72450	23 47 56.1	-28 19 16	V = 14.4; Size 0.7x0.5; SB = 13.1	extremely faint, very small, round. Requires averted to glimpse. This difficult member is situated about 12' S of the central group.
PGC 72466	23 48 20.7	-28 13 54		very faint, round, 15" diameter, can hold continuously with averted vision. Located 2.7' SSE of a mag 11.5-12 star and 10' SE of Delta Sculptoris on the SE side of the cluster.
PGC 72469	23 48 21.1	-28 06 58		extremely faint, round, 25" diameter, low surface brighness. Picked up 2.5' SSW of brighter PGC 72471. Located 7.6' W of Delta Sculptoris (doesn't interfere with viewing).
PGC 72471	23 48 23.3	-28 04 29		very faint, round, 20" diameter. This faint member was picked up 8' NW of Delta Sculptoris and 1.2' SSW of a mag 13.5 star and then verified on the GSC finder chart. Nearby PGC 72469 lies 2.5' S.