Object of the Week, April 20 2014 – The remarkable NGC 3158 cluster

[Steve Gottlieb]

NGC 3158
Brightest member of a small cluster of early-type galaxies with more the 30 members.

Leo Minor
RA 10h 13.8m
DEC +38° 46

Magnitude 11.9V

This remarkable cluster (WBL 258) consists of over a dozen galaxies surrounding NGC 3158, all packed into a 15' field. The largest and brightest member, NGC 3158, was discovered by William Herschel on 17 March 1787 and should be visible in a 6-inch scope. The SDSS image reveals a giant elliptical snacking on numerous small neighbors captured in its halo. With my 18-inch scope, I logged it as "fairly bright, moderately large, irregularly round, well concentrated with a very bright core and relatively large, fainter halo, ~0.8'x0.7'." NGC 3163, the second brightest member (also visible in a 6") was also found by Herschel and logged in my 18-inch as "fairly faint, small, round, 25" diameter, very small bright core."

The surrounding field is swarming with small, faint galaxies including NGC's 3150, 3151, 3152, 3159, 3160 and 3161. All of these are visible in a 10 to 14-inch scope using moderate to high power (several were discovered by Guillaume Bigourdan in 1886 with an 11" refractor and others with Lord Rosse's 72" Leviathan). Finally, there are several more challenging MCG and LEDA galaxies in the 16th magnitude range which were all noted in my 18-inch.

When you check out the NGC 3158 cluster, see if you can detect the Shakhbazian 49 group of compact galaxies -- just 20' NE of the NGC 3158 cluster. Megastar plots a single anonymous galaxy -- MAC 1015+3855 = LEDA 3753093. I'm guessing this tiny galaxy is rough V = 16.5 and a slightly fainter companion is 20" NNW. Both were barely visible in my 18-inch scope. I'm curious to hear who has snagged these?

A full resolution image is available here (https://www.facebook.com/AdventuresInDeepSpace/photos/a.576005402465267.1073741825.186343804764764/655403387858801/?type=1&theater)
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“GIVE IT A GO AND LET US KNOW”
GOOD LUCK AND GREAT VIEWING!

[Howard B]

Hi Steve, I almost have an observation of the NGC 3158 galaxy group - right after I'd located it clouds moved in and closed down the night. Your post is a good reminder to go back and get a good look!

Howard

[RussB]

Looks like a good one. Its now on my to do list

Russ

[RolandosCY]

Had a double go on this wonderful group! My first attempt was just after I noticed Steve's initial posting. I read it on the small screen of an old smartphone while waiting for my 18" to cool at Lysos (normally our best site), so I really did not know what to expect of this group. In a so and so night I saw NGC 3158 and three other distinct galaxies to the west, but with the sky backround being more blue than black I did not press the matter too much.

Then on Friday evening we found ourselves at one of our mountain sites at around 4,000f altitude. The contrast seemed better there, and I spent a considerable amount of time on the group. NGC 3158 is distinct, bright and easy, roundish with a very bright core, readily visible even at low powers. The "trio" to the west was again readily visible, as a "smudge" at low powers but readily resolvable at medium powers. To my eyes they all seemed roundish with 3159 and 3163 about equal in brightness, and 3161 fainter. Knowing that there were many other members lurking around I pushed the magnification to around 275X and started examining the area more closely. To my surprise, I detected a fourth glow very near the "trio", much fainter than the other three, nearer to 3159. It was more of an averted vision object, occasionally visible with direct vision, and of an ill-defined shape. It turned out to be MCG +7-21-19, quite faint at magnitude 15.1. Further to the W I detected another two faint glows, namely 3150 and 3151, the latter appearing more elliptical than round with an even brightness. Returning to 3158, with the increased magnification I detected two tiny galaxies right to the east of the anchor galaxy (one I had detected it the previous night as well, but I mistook it for a faint star). They were MCG +7-21-25 and MCG +7-21-27. Finally, to the north of 3158 I detected a longish ellipse of rather low surface brightness, it turned out to be 3160. I managed to miss 3152 though which should had been also detectable with my set-up.

Regarding Shakhbazian 49, I did prepare Megastar charts specifically for that. It was a breeze locating the 10th magnitude anchor star, but even at very high powers I can not be certain I detected the two galaxies. At times I could detect an undefined glow just above the sky background brightness that was moving with my tapping of the telescope, at the correct position. Yet, examining afterwards the attached photo, I could see that there were faint stars beyond the limit of megastar near the galaxies. The galaxies do appear brighter than the stars in the photo, but could I be detecting the combined glow of the faint galaxies AND faint field stars? I will need another go just for that!

Here is my drawing of the NGC 3158 region...

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[KidOrion]

Great sketch, Rolandos!

[Marko]

Remarkable indeed. I too love this very rich group and it makes for a nice 'transparency meter' too!
The last time I 'went deep' on this was 3/28/2009 and as it happens, Steve was present at the gathering.

I'll have to try the Shakhbazian 49 group sometime too, a far more challenging undertaking I bet.

The night started cloudy then cleared and by time of this group of 13 observations we had a 21.6x SQM night.
These all were from my 18" StarMaster f/3.7
Pay no attention to my 'seeing' value as it was not entered and my transparency is 1-5 scale.

LMi NGC 3150 DblG Location: RA '10 13 26.3' Dec '+38 39 27' mag 15.5
Date: 03/28/09 Time: 23:58 Site: WSprDSR
Scope: 18SmF3.7 Eyepiece: 5mmNag Power: 338.0x
NELM: 0.0 SQM: 21.64 Seeing: 0 Transparency: 4
'Ngc3158_group: Next to and similar bright and size to 3151'

LMi NGC 3151 Glxy Location: RA '10 13 29.1' Dec '+38 37 11' mag 14.8
Date: 03/28/09 Time: 00:00 Site: WSprDSR
Scope: 18SmF3.7 Eyepiece: 5mmNag Power: 338.0x
NELM: 0.0 SQM: 21.64 Seeing: 0 Transparency: 4
'Ngc3158_group: Next to and similar bright and size to 3150'

LMi NGC 3152 MltG Location: RA '10 13 34.1' Dec '+38 50 35' mag 15.2
Date: 03/28/09 Time: 23:04 Site: WSprDSR
Scope: 18SmF3.7 Eyepiece: 5mmNag Power: 338.0x
NELM: 0.0 SQM: 21.64 Seeing: 0 Transparency: 4
'Ngc3158_group: Small, near 3160'

LMi MAC 1013+3844 Glxy Location: RA '10 13 39.5' Dec '+38 44 43' mag 15.0
Date: 03/28/09 Time: 00:00 Site: WSprDSR
Scope: 18SmF3.7 Eyepiece: 5mmNag Power: 338.0x
NELM: 0.0 SQM: 21.64 Seeing: 0 Transparency: 4
'Ngc3158_group: More obvious of 2 MACs to W of 3158'

LMi MAC 1013+3845B Glxy Location: RA '10 13 42.5' Dec '+38 45 09' mag 15.5
Date: 03/28/09 Time: 00:10 Site: WSprDSR
Scope: 18SmF3.7 Eyepiece: 5mmNag Power: 338.0x
NELM: 0.0 SQM: 21.64 Seeing: 0 Transparency: 4
'Ngc3158_group: Less obvious of 2 MACs to W of 3158'

LMi MCG +7-21-19 Glxy Location: RA '10 13 47.8' Dec '+38 40 33' mag 15.1
Date: 03/28/09 Time: 23:55 Site: WSprDSR
Scope: 18SmF3.7 Eyepiece: 5mmNag Power: 338.0x
NELM: 0.0 SQM: 21.64 Seeing: 0 Transparency: 4
'Ngc3158_group: Dimmest of these 4'

LMi NGC 3158 Glxy Location: RA '10 13 50.5' Dec '+38 45 53' mag 11.9
Date: 03/28/09 Time: 00:36 Site: WSprDSR
Scope: 18SmF3.7 Eyepiece: 5mmNag Power: 338.0x
NELM: 0.0 SQM: 21.64 Seeing: 0 Transparency: 4
'Ngc3158_group: 1' size but the most obvious of this group and in 'center''

LMi NGC 3159 Glxy Location: RA '10 13 52.8' Dec '+38 39 15' mag 13.6
Date: 03/28/09 Time: 23:54 Site: WSprDSR
Scope: 18SmF3.7 Eyepiece: 5mmNag Power: 338.0x
NELM: 0.0 SQM: 21.64 Seeing: 0 Transparency: 4
'Ngc3158_group: Similar mag to 3160'

LMi NGC 3160 Glxy Location: RA '10 13 55.1' Dec '+38 50 34' mag 15.2
Date: 03/28/09 Time: 23:56 Site: WSprDSR
Scope: 18SmF3.7 Eyepiece: 5mmNag Power: 338.0x
NELM: 0.0 SQM: 21.64 Seeing: 0 Transparency: 4
'Ngc3158_group: 1' len 2EL 160dPA'

LMi NGC 3161 Glxy Location: RA '10 13 59.2' Dec '+38 39 25' mag 14.5
Date: 03/28/09 Time: 00:00 Site: WSprDSR
Scope: 18SmF3.7 Eyepiece: 5mmNag Power: 338.0x
NELM: 0.0 SQM: 21.64 Seeing: 0 Transparency: 4
'Ngc3158_group: Between 3159/3163'

LMi MCG +7-21-25 Glxy Location: RA '10 14 02.0' Dec '+38 45 17' mag 16.3
Date: 03/28/09 Time: 23:56 Site: WSprDSR
Scope: 18SmF3.7 Eyepiece: 5mmNag Power: 338.0x
NELM: 0.0 SQM: 21.64 Seeing: 0 Transparency: 4
'Ngc3158_group: this and MCG +7-21-27 go E from 3158 then 2 stars continue line'

LMi NGC 3163 Glxy Location: RA '10 14 07.1' Dec '+38 39 08' mag 13.3
Date: 03/28/09 Time: 00:05 Site: WSprDSR
Scope: 18SmF3.7 Eyepiece: 5mmNag Power: 338.0x
NELM: 0.0 SQM: 21.64 Seeing: 0 Transparency: 4
'Ngc3158_group: Similar mag to 3161'

LMi MCG +7-21-27 Glxy Location: RA '10 14 07.7' Dec '+38 45 42' mag 16.4
Date: 03/28/09 Time: 23:56 Site: WSprDSR
Scope: 18SmF3.7 Eyepiece: 5mmNag Power: 338.0x
NELM: 0.0 SQM: 21.64 Seeing: 0 Transparency: 4
'Ngc3158_group: MCG +7-21-25 then this one go E from 3158 then 2 stars continue line'

[Jimi Lowrey]

I tried SHK 49 last night and found it pretty tough under less than ideal conditions here in West Texas. I have viewed this faint group before and am familial with the field. SHK 49 is near a nice double star so its easy to ID the field, at 375X I could not see any of the galaxies so I bumped up the power to 488X still nothing I then tried 697X and had little luck at that power also, I then tried 488X with a ZAO II 10MM this helped the view with the higher light transmission eyepiece. I could see a small elongated glow a small percentage of the time with AV only with this eyepiece. I looked for a long while and the small unresolved glow would come and go with the seeing more go! than come.

[mdstuart]

I had another go at this one the other night. I struggled to see any galaxies in my old 10 inch other than NGC 3158. With my 16 inch I did much better.

NGC 3158 was very bight and obvious. I managed to pick up the edge on NGC 3160 and the small NGC 3151 with averted vision.

I was also able to see the trio NGC 3163 / 3161 / 3159 which looked lovely.

So six!

With darker skies I am sure I could have pulled a load more out of the view but it was great anyway.

Regards

Mark

[Steve Gottlieb]

Since this thread has been revived, here are four non-NGC members of the group viewed with my 18" about 6 years ago.

PGC 2131950
10 13 33.8 +38 37 05
V = 15.7; Size 0.5'x0.25'; PA = 0d
Extremely faint and small, round, 5" diameter. A very faint star is at the NE edge. With averted vision the halo occasionally increases to 15" diameter. Forms a close pair with brighter NGC 3151 0.9' W.


PGC 2135428
10 13 39.5 +38 44 43
Size 0.4'x0.25'; PA = 28d
Extremely faint and small, round, 5" diameter. Located just 2.4' SW of NGC 3158 and 30" N of a mag 14 star. A fainter companion, PGC 2135625, is 44" NE.

PGC 2135625
10 13 42.5 +38 45 09
V = 15.7; Size 0.3'x0.2'; PA = 105d
Situated just 1.7' SW of NGC 3158 and 1' NE of a mag 13.5 star. PGC 2135428 is just 44" SW.


MCG +07-21-019 = PGC 29818
10 13 47.9 +38 40 32
V = 15.0; Size 0.5'x0.4'; Surf Br = 12.2; PA = 85d
Extremely faint, very small, elongated 3:2 E-W, ~20"x14". Located 1.6' NW of NGC 3159 and faintest of 4 with NGC 3161 and NGC 3163 (the three NGC galaxies form a nice 2.8' string). This quartet is just 6' S of NGC 3158.