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Object of the Week December 20, 2020 - A Desert Full of Galaxies – LGG 27
Object of the Week December 20, 2020 - A Desert Full of Galaxies – LGG 27
Constellation: Cetus
NGC 584, IC 1712, PGC 5663, MCG-1-4-60
Type: Lenticular Galaxy (S0)
RA: 01h 32.3m
DEC: -6° 46'
Mag: 10.36
Size: 3.8’ x 2.5’
NGC 586, PCG 5679, MCG-1-5-1
Type: Spiral Galaxy (Sa)
RA: 01h 32.6m
DEC: -6° 47'
Mag: 14.08
Size: 1.6’ x 0.8’
NGC 596, PGC 5766, MCG-1-5-1
Type: Elliptical Galaxy (E)
RA: 01h 33.9m
DEC: -6° 56'
Mag: 10.89
Size: 3.2’ x 2.0’
NGC 600, PGC 5777, MCG-1-5-7
Type: Spiral Galaxy (SBcd)
RA: 01h 34.1m
DEC: -7° 12'
Mag: 12.37
Size: 2.6 x 2.6’
NGC 615, PGC 5897, MCG-1-5-8
Type: Spiral Galaxy (SB)
RA: 01h 36.1m
DEC: -7° 14'
Mag: 11.49
Size: 3.2’ x 2.0’
NGC 636, PGC 6110, MCG-1-5-13
Type: Elliptical Galaxy (E)
RA: 01h 40.1m
DEC: -7° 24'
Mag: 11.38
Size: 2.7’ x 2.3’
MGC-1-4-44, PGC 5341, UGCA 17
Type: Spiral Galaxy (Sc)
RA: 01h 33.9m
DEC: -6° 56'
Mag: 13.89
Size: 2.9’ x 0.5’
MGC-1-5-14, PGC 6190
Type: Spiral Galaxy (Scd)
RA: 01h 41.5m
DEC: -5° 25'
Mag: 15.00
Size: 2.0’ x 0.5’
Cetus, the Whale, is the fourth largest constellation, occupying well over 1,200 square degrees of mostly empty, blank sky. It contains no open clusters or diffuse nebulae, and despite its large size boasts just one Messier object, the Seyfert galaxy M77. However, it does contain a fine planetary nebula NGC 246 and a host of galaxies. As the late Sky and Telescope columnist Walter Scott Houston put it, “[Cetus] is a vast stellar desert,” but also “a rich area for galaxy hunters.” This week we explore 5° by 5° section of that “desert”, a group of galaxies collectively catalogued as LGG 27. The eight galaxies in LGG 27 include NGCs 584, 586, 596, 600, 615, and 636 along with MCG-1-4-44 and MCG-1-5-14.
The Lyon Groups of Galaxies (LGG) is a whole sky catalog of nearby groups of galaxies taken from the Lyon-Meudon Extragalactic Database. From the 78,000 objects in the database, a sample of 6,392 galaxies was extracted, complete up to the limiting apparent magnitude B0 = 14.0. Furthermore, in order to consider solely the galaxies of the local universe, all the selected galaxies have a known recession velocity smaller the 5,500 km s-1. Two methods were used in group construction: Huchra-Geller-derived percolation method and a Tully-derived hierarchical method. Each method resulted in one catalog. These were then compared and synthesized to obtain a single catalog containing the most reliable group. The LGG was published in 1992 by A.M. Garcia of the Observatoire de Lyon in Laval, France. The catalog includes 485 groups and 3,933 member galaxies.
Let’s take a tour of the six NGC galaxies in the group, all discovered by William Herschel.
Attachment 4147
click on chart to enlarge
The dominant galaxy of LGG 27 is NGC 584. Nicknamed the Little Spindle by Stephen James O’Meara, NGC 584 looks like a smaller a dimmer version of NGC 3115 in Sextens. NGC 584 is a quite small, yet surprisingly bright galaxy with a total luminosity of 17 billion suns. It is a good example of how a tiny galaxy with a moderately faint magnitude (10.4) is quite easy to see. Since its discovery in 1785 by William Herschel there has continuing uncertainty on the classification of the galaxy. More recent data strongly indicates it is a lenticular (S0) galaxy – an intermediate system between the ellipticals and the spirals. In fact de Vaucouleurs’ Atlas of Galaxies uses NGC 584 as an example of a S0 galaxy. This data also shows NGC 584 rotates relatively rapidly and has a tilted disk within its bright bulge, which we see inclined 35° from edge-on.
About 4.3’ southeast of NGC 584 we find a companion galaxy NGC 586. This non-interacting galaxy has a very bright nucleus surrounded by an elongated shell of faint light. It’s listed magnitude is 13.2.
Continue to move about 25’ southeast we next cross paths with NGC 596, an elliptical system that shines at magnitude 10.9. The galaxy shows an outer envelope and is a merger remnant. The surface brightness profile is smooth and featureless. The galaxy hosts a supermassive black hole. NGC 596 will be difficult due the glare of a nearby star.
Proceeding nearly south we come across NGC 600, a barred spiral galaxy with a listed magnitude of 12.6.
Continue nearly due east and we find the nearly edge-on spiral galaxy NGC 615 shining at magnitude 11.6.
We get to our final NGC galaxy of the group by continuing further east and just a tad bit south where we come across NGC 636 at magnitude 11.4. But don’t call it quits yet, the two MGC galaxies in this group will be the most challenging, but I’m sure well worth the hunt.
Now it is your turn in LGG 27. Give it a go and let us know!
