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View Full Version : Object of the Week June 17, 2012 – Arp 171 and the NGC 5718 galaxy group


Howard B
June 18th, 2012, 04:16 PM
Arp 171 and the NGC 5718 galaxy group

Galaxy Group
Virgo
J2000
RA 14 40 43
DEC +3 27 57

MAG 13.9 (N5718) 14.3 (IC1042)

Arp 171 is only a small part of the NGC 5718 galaxy group, which I didn’t realize before observing it on the night of May 18, 2012. I went expecting to see two relatively bright galaxies close to each other, but in the eyepiece I saw two similar pairs equally close – which was Arp 171?
244245

Turns out it’s the pair on the left – NGC 5718 and IC 1042, but the real fun was slowly realizing there where even more galaxies in the field of view. I ended up seeing ten using 408x with my 28 inch f/4 Newtonian under a 21.48 SQM sky, but there are a few more in the neighborhood for the patient observer to find.

"GIVE IT A GO AND LET US KNOW"

GOOD LUCK AND GREAT VIEWING!
Steve Gottlieb
June 20th, 2012, 01:08 AM
Howard, your excellent pick for Object of the Week and sketch inspired me to take a look at this group last night with my new 24" at my local site (mag 21.40-21.45 SQM skies) just north of Santa Rosa. The group has the designation MKW 8 and WBL 518. The MKW groups are from this paper -- http://articles.adsabs.harvard.edu/full/1975ApJ...199..545M

I ended up logging 21 galaxies in a 1 degree circle centered on NGC 5718, though there were many more faint ones I didn't have the patience to chase after. I checked NED and all 21 are members of the group (z = .028). I noticed Megastar does not correctly identify IC 1043 -- it's the galaxy listed as a MAC just east of IC 1041. There's not much structure in any of these galaxies but here are my notes ---

CGCG 047-128 = PGC 52372
14 39 18.0 +03 22 06
V = 14.1; Size 0.9'x0.7'; PA = 157d
faint, small, round, even surface brightness, 15" diameter. Located 5.6' E of a mag 11 star on the southwest side of the MKW 8 group.

CGCG 047-129 = MCG +01-37-043 = PGC 52384
14 39 37.8 +03 08 48
V = 13.8; Size 0.9'x0.6'; PA = 21d
fairly faint to moderately bright, small (outer halo not noticed), oval 4:3 NW-SE, 20"x15", broad concentration with a brighter nucleus that increases to the center. Nearly collinear with a mag 11 star 2.6' SSW and mag 9.6 HD 128922.

2MASX J14393976+0343153 = PGC 3124863
14 39 39.8 +03 43 15
V = 15.4; Size 0.4'x0.25'; PA = 15d
faint, extremely small, round, 10" diameter, no details. Located 3.5' SE of a mag 10.0 star on the northwest side of the NGC 5718 group (MKW 8).

CGCG 047-130 = PGC 52382
14 39 41.2 +03 55 27
V = 14.4; Size 0.9'x0.4'; PA = 61d
faint to fairly faint, small, irregularly round, 20"x15". Located on the north side of the NGC 5718 group (MKW 8).

2MASX J14401689+0339321 = PGC 1256360
14 40 16.9 +03 39 32
V = 15.1; Size 0.4'x0.25'; PA = 130d
faint, extremely small, round, 10" diameter. A mag 15.2 star is just 14" W of center. This member of the NGC 5718 group (MKW 8) is located 13' NNW of NGC 5718.

CGCG 047-131 = WBL 518-001 = PGC 52423
14 40 26.0 +03 35 56
V = 15.0; Size 0.5'x0.25'; PA = 35d
faint, very small, round, 12"-15" diameter, occasional faint stellar nucleus. Situated 9' NNW of NGC 5718/IC 1042 = Arp 171 in the core of the MKW 8 group.

IC 1039 = CGCG 047-133 = WBL 518-002 = PGC 52428
14 40 29.4 +03 25 58
V = 14.7; Size 0.6'x0.3'; PA = 43d
faint, very small, slightly elongated SW-NE, 15" diameter. Located 3.7' SW of NGC 5718 in the core of the galaxy group MKW 8.

IC 1041 = MCG +01-37-045 = CGCG 047-134 = WBL 518-004 = PGC 52434
14 40 37.9 +03 22 37
V = 13.9; Size 0.8'x0.6'; PA = 165d
fairly faint, fairly small, elongated 4:3 NNW-SSE, well concentrated with a small bright core. Forms a close pair with IC 1043 1.4' E. Located 5.5' S of NGC 5718/IC 1042 in the MKW 8 cluster.

IC 1042 = Arp 171 = UGC 9457 = MCG +01-37-046 = WBL 518-003 = PGC 52433
14 40 39.0 +03 28 10
V = 13.3; Size 1.1'x1.1'; Surf Br = 13.3
fairly faint, fairly small, round, 24" diameter, weak concentration. Fainter member of a double system (Arp 171) with NGC 5718 at the WSW edge (haloes virtually in contact.

NGC 5718 = Arp 171 = UGC 9459 = CGCG 047-137 = MCG +01-37-047 = WBL 518-005 = PGC 52441
14 40 42.9 +03 27 55
V = 12.9; Size 1.5'x1.1'; Surf Br = 13.3; PA = 85d
moderately bright, fairly small, oval 3:2 or 4:3 E-W, ~35"x25", large bright core, brighter along the major axis. Forms a double system with IC 1042 (Arp 171), 1.0' WNW. A mag 10.7 star is 1.2' NE and detracts a bit. Brightest member in the poor group MKW 8 and over 20 members tracked down within 30' of NGC 5718.

IC 1043 = PGC 2800989
14 40 43.4 +03 22 26
V = 14.8; Size 0.6'x0.3'; PA = 22d
faint, very small, slightly elongated SSW-NNE, 15"x10", faint stellar nucleus with direct vision. Located 1.4' E of IC 1041 in the core of the NGC 5718 group (MKW 8). This galaxy is not identified as IC 1043 in Megastar or HyperLeda and is not listed in the original PGC.

CGCG 047-136 = WBL 518-006 = PGC 52442
14 40 43.5 +03 15 15
V = 14.7; Size 0.7'x0.5'; PA = 29d
faint, small, round, 15" diameter, weak concentration to center.

CGCG 047-138 = WBL 518-007 = PGC 52448
14 40 46.1 +03 05 56
V = 15.0; Size 0.5'x0.35'; PA = 167d
faint, very small, round, 15" diameter, occasional stellar nucleus. A mag 14.4 star is 35" SW and a triangle of mag 14/15 stars is close north. UGC 9463 lies 4' NE.

CGCG 047-140 = WBL 518-008 = PGC 52452
14 40 52.7 +03 25 06
V = 14.6; Size 0.5'x0.3'; PA = 50d
faint, very small, round, 15" diameter, faint stellar nucleus. This member of the NGC 5718 group (MKW 8) is located just 3.7' SE of NGC 5718.

CGCG 047-141 = WBL 518-009 = PGC 52451
14 40 56.6 +03 31 41
V = 15.3; Size 0.6'x0.3'; PA = 167d
very faint, very small, 0.4'x0.2', elongated 2:1 N-S, low surface brightness. Located 5' NE of NGC 5718 in the core of the MKW 8 group. Situated less than 1' NW of wide 34" pair of mag 10.8/12.1 stars (HJ 1257).

UGC 9463 = CGCG 047-139 = WBL 518-010 = PGC 52453
14 40 59.3 +03 08 13
V = 14.2; Size 1.0'x0.3'; PA = 43d
faint to fairly faint, fairly small, oval 2:1 SW-NE, 20"x10", broad concentration. Two mag 15.5-16 stars aligned NW-SE are on opposite sides of the NE end of the galaxy. CGCG 047-138 lies 4' SW.

2MASX J14410613+0339399 = PGC 1256400
14 41 06.1 +03 39 40
V = 16.0; Size 0.4'x0.3'; PA = 123d
extremely faint and small, round, 12" diameter. Only glimpsed with averted but confirmed. Located 13' NE of NGC 5718 and 1.8' SE of a mag 10.4 star in the MKW 8 group.

CGCG 047-143 = WBL 518-011 = PGC 52475
14 41 32.1 +03 35 57
V = 14.8; Size 0.5'x0.3'; PA = 60d
faint to fairly faint, very small, round, 15" diameter, gradually increases to a very small brighter nucleus. Located 15' NE of NGC 5718 in the MKW 8 group.

CGCG 047-145 = WBL 520-001 = PGC 52502
14 41 58.7 +03 23 24
V = 14.4; Size 0.5'x0.4'; PA = 145d
faint, very small, round, 18" diameter, weak concentration. Located 10' ESE of mag 8.4 HD 129229 in the NGC 5718 group (MKW 8).

CGCG 047-146 = PGC 52508
14 42 06.3 +03 19 51
V = 15.4; Size 0.5'x0.5'
extremely faint, very small, irregularly round, ~15" diameter. Located 22' SE of NGC 5718 in the MKW 8 group.

CGCG 047-147 = WBL 520-003 = PGC 52525
14 42 25.7 +03 13 55
V = 14.0; Size 0.9'x0.35'; PA = 110d
fairly faint, fairly small, elongated 2:1 WNW-ESE, 25"x12", broad concentration.