Galaxy of the Month Archive 2014

In this series of articles we draw your attention to galaxies particularly worthly of an observer's time.

• December 2014 - Galaxy of the Month

  LGG 117 Group in Taurus

  The constellation of Taurus is not traditionally where you look for galaxies but it does in fact contain quite a number of NGC galaxies. Most are quite faint but there are a number within range of medium to large telescopes (here I class this as in the 30-50cm class range) under typical UK skies (i.e. poor).

  Our target this month is the small group of galaxies associated with NGC 1589. Known as LGG 117 from Garcia 1993 this small group consists of the NGC galaxies 1586,1587,1588 and 1589 along with a number of other UGC galaxies in the field. The total number of galaxies in the group is probably about 7. The finder chart shows some of these galaxies.

  

  This image of the LGG 117 region was provided by the Sloan Sky Survey.

  The brightest galaxies in this group are the interacting pair NGC 1587 and NGC 1588. First discovered by William Herschel in 1783 this pair will be a challenge. The brighter galaxy NGC 1587 is a peculiar elliptical and may be visible in 22cm however its companion NGC 1588 will be more of a challenge and will probably require at least 30-40 cm to separate out. The type of NGC 1588 may be questionable but is probably a peculiar elliptical as well. The deep images shown here from the Sloan Sky survey show that NGC 1587 appears to have shells and 1588 is clearly distorted. The distance to the pair has some variation but is about 40 Mpc or so. NGC 1587 itself is bright in X-rays.

  

  This image of NGC 1587 and NGC 1588 was provided by the Sloan Sky Survey.

  In the same medium power field is the edge on spiral galaxy NGC 1589. This was also discovered by William Herschel on the same night in December of 1783. NGC 1589 has had at least one supernova, the one in 2001 being discovered by Tom Boles and named as 2001eb. The distance to NGC 1589 is about 48 Mpc. The nucleus of NGC 1589 is classed as boxy and it will be unfortunately quite a challenge to see although Luginbuhl and Skiff report seeing it and 1587 with 15cm from a high dark site.

  It would appear that both NGC 1589 and 1587 may belong to a class of AGN known as low luminosity AGN’s or LLAGN. Interestingly it is NGC 1589 and 1587 which are classified as a pair in the UZC catalogue.

  Owen Brazell - Galaxy Section Director

• November 2014 - Galaxy of the Month

  NGC 507 Group in Pisces

  The NGC 507 group is the single richest group of galaxies in Pisces containing 9 NGC galaxies brighter than 15th magnitude. There are also a number of galaxies listed in the IC here as well. The accompanying chart also shows the profusion of fainter background galaxies that are probably not part of the group. The group is part of the Perseus-Pisces super cluster confusingly it is also known as the Pisces cluster along with the NGC 383 cluster. The main cluster galaxies were discovered by William Herschel in 1784.

  

  This image of the NGC 507 region was provided by the Sloan Sky Survey.

  The largest and brightest galaxy in the group, NGC 507 was discovered to have faint concentric shells by Halton Arp when looking at plates taken by the 200". He subsequently added it as Arp 299 in his catalogue of peculiar galaxies. These shells are now thought to be the product of ancient mergers. NGC 507 is also an AGN and seems to have radio lobes associated with it.

  NGC 508 is not part of Arp 229 despite some sources suggesting it is. The description by Arp is quite clear what Arp 229 is. Although they are quite close in angular terms it is not clear that NGC 508 is actually physically associated with NGC 507.

  

  This image of the NGC 499 region was provided by the Sloan Sky Survey.

  The group does show a number of small sub-structures in its central core which suggests that it may still be in the process of accreting other smaller groups of galaxies and has not yet reached its final state. NGC 499 appears to be at the centre of a second peak in the X-Ray halo and may be the central galaxy of another group merging with the NGC 507 group. Unfortunately it is not possible to say which way NGC 499 is moving.

  The main part of the group is in the form of a chain but there are a number of galaxies off the side of this chain as well. The group would appear to be at a distance of 63 Mpc and forms part of the main filamentary ridge of the Perseus-Pisces super cluster that also contains the Abell clusters 262, 347 and 426.

  

  This image of region around NGC 515 and NGC 517 was provided by the Sloan Sky Survey.

  Visually this is a stunning group. The brightest members should be visible in a 22cm telescope but it is with larger telescopes that the true beauty and number of galaxies in the field is really shown. The whole group will fit in the medium power field using a hyperwide (100 degree AFOV) eyepiece.

  Surprisingly there are no decent scale amateur images of this bright group so the images accompanying this piece are all from the Sloan digital sky survey. Perhaps a challenge for our members who have CCD imagers.

  Owen Brazell - Galaxy Section Director

• October 2014 - Galaxy of the Month

  NGC 6951 in Cepheus

  

  This image was provided by Martin Winter and Warren Keller. Please click on it for a high resolution version.

  In 1877 Jerome Coggia discovered a nebula in Cepheus that was given the name NGC 6952. Later Lewis Swift independently found a nebula nearby in 1885. Denning later showed that these were one and the same object but Coggia had a positional error of 20’. The designation NGC 6952 was later dropped and Dreyer issued a correction in the IC2.

  The galaxy is classified as SAB(rs)bc, a barred spiral galaxy. Its bright core also suggests it is a Seyfert galaxy (a mild active galactic nucleus or AGN). It would appear to be a type two Seyfert galaxy. NGC 6951 lies about 65 million light years away and has been home to two recent supernova in 1999el and 2000E. The galaxies location also means that it is involved with a lot of galactic cirrus as this deep image shows. An even deeper image can be found at the Capella Observatory website. A wide field view of the cirrus can be found on Oleg Bryzgalov's astrophoto website. The galaxy is interesting because it is showing both strong star formation activity and an active core. As the galaxy is an isolated system it is not clear what has triggered the current round of star formation. The galaxy appears to have a circumnuclear ring and the gas flowing through the bar appears to stall here and provide the material for massive star formation. This is not unlike what seems to be happening in our galaxy on a smaller scale. The ring appears to be about 1.5 billion years old and seem to have been forming stars for most of that time.

  Visually the galaxy is going to be a difficult target. From typical UK skies I think that at least 30cm+ aperture will be needed. Through a large telescope the galaxy shows a bright core and a fainter envelope. The envelope is definitely elliptical in shape. Smaller instruments may well just show the core.

  Owen Brazell - Galaxy Section Director

• September 2014 - Galaxy of the Month

  NGC 7339 in Pegasus

  

  This image was provided by the Sloan Sky Survey and this finder chart was produced using Megastar 5.

  NGC 7332 and NGC 7339 are an isolated bound pair of galaxies about 67 million light years away. NGC 7332 is lenticular galaxy with a boxy nucleus. Lenticular galaxies have a light profile that makes them look like spiral galaxies but they have no gas and new stars. They are usually found in large galaxy clusters where it is believed that the gas is stripped out by ram pressure as the galaxy moves through the intra-cluster medium. It is relatively unusual to see them in isolated situations like this.

  NGC 7339 is an edge on spiral that is unusually blue. The pair form number 57 0 in the catalogue of double galaxies by Karachentsev. Although NGC 7332 and 7339 appear to be a dynamically interacting pair there are no signs of tidal distortions in the system so the orbit is currently fairly wide. Deep radio observations of the system also show no evidence of tidal interactions although they have turned up some new dwarf galaxies associated with the pair. They do however show a stream of gas in NGC 73339 which could be the remains of a merger event which could account for the current star formation episode in it. Recent surveys looking for globular clusters suggest that both galaxies have a small number ~175 for NGC 7332 and perhaps 75 for NGC 7339. NGC 7339 was also home to supernova 1989L. Both the galaxies were discovered by William Herschel in 1784. NGC 7332 is catalogued as S0(pec) because of the box like shape of its nucleus. The box could be evidence for a bar in the galaxy. Unusually for an S0 type galaxy NGC 7332 does show evidence for a large amount of ionized gas so it maybe a young version of this type. NGC 7339 is probably an Sbc type spiral but is features are fairly low contrast.

  Both these galaxies are relatively bright and should be visible in telescopes of 20cm or above aperture from typical UK skies. The galaxies are an interesting pair because they are at right angles to each other. It should be noted that NGC 7339 is the fainter of the pair whne seen visually. It may be possible with larger telescopes to make out the box like shape. Of the nucleus of NGC 7332. They make a nice pair to warm up with before going are more challenging targets.

  Owen Brazell - Galaxy Section Director

• June 2014 - Galaxy of the Month

  NGC 6118 in Serpens Caput

  

  Image Courtesy of Astro Works Corporation and the Norma Rose Observatory, Queensland, Australia.

  Summer is not the best time for viewing galaxies as the northern skies never really get dark and the sky is dominated by the Milky Way and its attendant star clusters and nebulae. There are however some galaxies to be seen and my choice this month is the galaxy NGC 6118 in Serpens Caput.

  First discovered by William Herschel in 1785 this is a nearly edge on spiral galaxy. Classified as a grand design spiral NGC 6118 is believed to lie at a distance of about 83 million light years and at that distance its size would be about 110000 light years across, making it almost the same size as our Milky Way.

  Its full classification is SA(s)cd suggesting it has tightly wound spiral arms along with a small bar. Deep images show that it has a lot of star formation going on in its arms which are highlighted by the blue star clusters.

  In 2004 NGC 6118 was host to the type Ib/c supernova 2004dk. These are relatively unusual objects that are thought to occur in binary systems where mass is stripped from one star by the other.

  Unusually NGC 6118 does not appear to be part of any galaxy group but appears to be an isolated field galaxy. As such it is of interest is determining how galaxies evolve when found in isolation rather than the usual groups.

  As the galaxy is large and faint it can be a challenge to see with smaller telescopes and has earned the name of the Blinking Galaxy because of its tendency to flicker in and out when different eye positions are used (I suspect this is a reference to the use of averted vision). Even though its total magnitude is fairly bright the size of the galaxy suggests that its surface brightness will be quite low and you will need a medium/large aperture telescope and a dark sky to see more than the core. It is regarded as one of the toughest of the Herschel 400 objects to find because of its faintness. Strangely based on this it appears in Michael Bakich’s book 1001 Celestial Wonders to see before you die !!.

  A fine image of the object can be found at the European Southern Observatory (ESO) website

  Owen Brazell - Galaxy Section Director

• May 2014 - Galaxy of the Month

  NGC 5529 in Boötes

  

  Image Courtesy of Adam Block/Mount Lemmon SkyCenter/University of Arizona. Please click on image for a high resolution version.

  Although as we move into May chasing faint galaxies becomes more problematic with the shortness of the observing window there are still some possibilities early in the month. Although NGC 5529 was first discovered by William Herschel in 1785 this edge on spiral galaxy in Boötes has remained off the radar for many observers, perhaps because of its faintness. Thought to be at a distance of about 140 million light years its size would be about 250000 light years, about twice the size of our galaxy. The nucleus of the galaxy shows a box like shape, often taken as an indication of an interaction and the spiral arms also show a warp. The galaxy itself is classified as an Sc galaxy a few degrees from edge on (86 degrees) it is likely that it is a barred spiral. In this way it is very similar to the better known NGC 4565. In the same field of the galaxy are two other NGC objects in NGC 5524 and NGC 5527. These are both much fainter and were discovered in 1855 by Mitchell using the 72” at Birr. NGC 5527 may be a companion of 5529 but 5524 is likely to be further away. The galaxy that distorted NGC 5529 no longer appears to be in the field with it. Observations using the Infrared satellite ISO showed that NGC 5529 appears to have the largest known halo of PAH molecules yet seen (Polyaromatic Hydrocarbons). This must be symptomatic of some large scale outflow from the galaxy. Herschel observations of NGC 5529 also suggest some oddities with the dusk disk as it does not fit a simple pattern. NGC 5529 appears to be the dominant member of a group of about 17 small galaxies and this may also be the cause of the halo gas. Of these thirteen would appear to be NGC galaxies NGC’s 5529, 5533, 5544, 5545, 5577, 5589, 5590, 5596, 5614, 5656, 5675, 5684 and 5695. Observationally NGC 5529 is going to be a challenge and although observations have been reported with instruments as small as 15cm to see any detail, in particular the dust lane are going to require much larger instruments in the 40cm+ class, certainly from typical UK skies. A nice drawing through a 45cm telescope can be seen at the Astronomy Sketch of the Day website. As can be seen there are many other bright galaxies in the field including NGC 5557. These will fit in the medium power field of many telescopes. However to see the fainter members of the 5529 system you will need to use higher powers.

  A Megastar© identification chart for the galaxies near to NGC 5529.

  Owen Brazell - Galaxy Section Director

• April 2014 - Galaxy of the Month

  Hickson 68 in Canes Venatici

  

  Image Courtesy of Bernhard Hubl, Nussbach (Austria). Please click on image for a high resolution version.

  The 68^th member of Paul Hickson’s catalogue of 100 compact groups unusually consists of five NGC objects, numbers 5353, 5354, 5350, 5358, 5355. NGC’s 5350, 5353, 5354 and 5355 were all discovered by William Herschel in 1788 using his 18.7” reflector whilst NGC 5358 was discovered by Stephan in 1880 using a 31" reflector. This tight group of galaxies is well placed in Canes Venatici in late Spring and has the added bonus of the bright galaxy NGC 5371 nearby. The group is located about 8 degrees south east of the Whirlpool galaxy M51. NGC 5371 is not part of the group. As one of the brighter Hickson (HCG) groups most of the galaxies should be visible in a 22cm telescope under dark skies however probably 30cm+ will be needed to see the fainter members of the group. The group appears to be at a distance of about 100 million light years. Interestingly NGC 5371 is also at the same distance and appears to be physically associated with the HCG 68 group. If so this group of galaxies may contain over 20 galaxies. The whole group appears to lie on a filament of galaxies connecting the Coma cluster (AGC 1656) to the Virgo cluster. Hickson 68 and NGC 5371 make up the Big Lick Group. It is not clear why it should have be so named as this is after the town of Roanoke in Virginia which itself was named after the local salt pan. This may just be a case of people randomly attaching names to objects in the sky with no real association. A fine image and identification chart appears at the Distant Lights website. This also shows the many faint background galaxies in the same area. A nice sketch of the area can also be found on the ASOD website. Interestingly NGC 5371 is probably the same as NGC 5390 being a re-observation by John Herschel and a case of mistaken identity. NGC 5353 and NGC 5354 appear to be interacting and both galaxies are producing large amounts of radiation on the radio spectrum. Although NGC 5354 is classified as a lenticular galaxy, SA0, it does show a dust lane in deep images which would be unusual for this type of galaxy. They both show distortions arising from this interaction. It would appear that these galaxies are separated by only about 9kpc and are the process of merging. This merger should take place in the near future in astronomical terms. The other bright member of the group, NGC 5350, is also classified as a Type A Seyfert galaxy so it has an active galactic nucleus. This is altogether a fascinating group of galaxies that should repay study with both medium and large telescopes.'

  The Megastar© finder chart shows the Hickson 68 region.

  Owen Brazell - Galaxy Section Director

• March 2014 - Galaxy of the Month

  M99 in Coma Berenices

  

  Image Courtesy of Warren Keller, New Mexico. Please click on image for a high resolution version.

  M99 hit the news recently because it had the second supernova this year found in a Messier galaxy, the first being M82. The supernova in this case never got that bright reaching only about 14th magnitude at maximum. First discovered by Pierre Mechain in 1781 it was added to Messier's last instalment of his catalogue of Nebulae and clusters. It is one of the faintest of the Messier objects and this is not helped by it being a face on spiral. It became famous as the second galaxy that Lord Rosse observed to have a spiral shape after M51 in 1846. Messier 99 is a standard grand design Spiral galaxy located at about 50 million light years from us. This has led to a morphological classification of SA(s)c. Although situated in the constellation of Coma M99 is actually part of the Virgo cluster, although there are some suspicions that it may be entering the cluster for the first time and is subject to some ram pressure stripping. Messier 99 does have the highest recession velocity of all the Messier galaxies. The galaxy also appears to have star formation going on at perhaps three times the expected rate for a galaxy of this time which could have been triggered by the interaction. This may account for the supernova. There have been three supernovae identified in M99 in the last century. There also appears to be a stream of gas linking it to the dark galaxy VIRGOHI21. This object appears to be a cloud of neutral hydrogen gas (HI) but its internal motions suggest that it may contain a lot of dark matter. However there are also some theories that suggest that this cloud is merely part of the tidal tail from M99. It is also possible that the distorting galaxy may be the lenticular galaxy NGC 4262. If this was the case then the encounter happened maybe 280 million years ago. Although not shown on our image the chart shows the location of NGC 4262 in relation to M99. A close up of M99 taken by the HST can be found here.

  A nice sketch of the galaxy can be found on the ASOD website, as can a sketch of the galaxy with the supernova. The image also shows the lovely coloured double star HJ 207 – one of John Herschel’s discoveries.

  The Megastar© finder chart shows the M99 region.

  Owen Brazell - Galaxy Section Director

• February 2014 - Galaxy of the Month

  NGC 4088 in Ursa Major

  

  Image Credit - Volker Wendel and Bernd Flach-Wilken, Spiegelteam Astrofotografie. Please click on image for a high resolution version.

  The major galaxies M81/82 and 108,109 and 101 in Ursa Major usually get all the attention but the constellation is filled with other interesting galaxies. One of the overlooked ones is NGC 4088. Classified as an intermediate spiral galaxy it forms a physical pair with NGC 4085. NGC 4088 was first discovered by William Herschel in 1788. The same observer found NGC 4085 the following year in 1789. Described as a grand design Spiral galaxy Halton Arp included it in his Atlas of Peculiar galaxies as Arp 18 because it appears to have a detached spiral arm. Both NGC 4088 and 4085 are members of the M109 group of galaxies. This group lying about 55 million light years away contains maybe 39 galaxies including M109. It is also known as the Ursa Major North group. Unusually the group contains no major elliptical galaxies. NGC 4088 and 4085 are at the front of this group at perhaps 50 million light years. Distances however to galaxies this close are notoriously unreliable if it is based on redshift because the peculiar motion of the galaxy maybe a substantial part of the Hubble flow. Recently NGC 4088 had a supernova (2009dd). Previous to that it had one in 1991 so it is a relatively prolific supernova generator. The image here shows Sn2009dd near the core of the galaxy. Visually NGC 4088 is bright enough to be seen in quite small telescopes, certainly in the 8-10” class. Larger telescopes will show much more detail and a series of observations made with a range of telescopes can be found at the DeepSkyForum.

  An interesting set of drawings of NGC 4088 can be found Bertrand Laville's Extreme Deep Sky Drawings website. Another view is at the Astronomy Sketch of the Day website. NGC 4085 should be visible in 8-10” telescopes but is considerably fainter. It is also an edge on spiral. For those who like collecting lists NGC 4088 is part of the original Herschel 400.

  The included PDF chart shows both of these galaxies.

  There is a fine image showing both galaxies at Kai Wiechen's Deep Sky Astrophotography website.

  Owen Brazell - Galaxy Section Director

• January 2014 - Galaxy of the Month

  NGC 2683 in Lynx

  

  Image Credit - ESA/Hubble and NASA. Please click on image for a high resolution version.

  First discovered by William Herschel (who else) in 1788 NGC 2683 was nicknamed the UFO galaxy as its shape looked like the classic UFO saucer from early Sci-Fi movies. It is an edge on spiral galaxy with a boxy middle. Found in the fairly non-descript constellation of Lynx – not called because of any resemblance to the animal but because you would need the eyes of a Lynx to see any of its stars. Due to the angle at which it is seen it is not clear whether or not NGC 2362 is a normal or a barred spiral but many astronomers lean towards the latter designation. Although NGC 2362 is both smaller and less luminous than the Milky Way it does seem to have a very large number of globular clusters with about 300 known. Most of these globular clusters appear similar to those in our own galaxy although appears significantly younger at around 3 billion yeas which suggest a recent star formation (interaction) event. The galaxy also appears to have a low amount of neutral and molecular hydrogen and this leads to a currently low level of star formation. There is a fine close-up view of NGC 2683 taken by Hubble.

  NGC 2683 is relatively close to us at a distance of about 16 million light years. This distance may however be an underestimate as more modern distance suggest it is at around 8 Mpc which would be 24 million light years. The nuclear bulge of NGC 2683 appears yellowish on images and this is due to its light passing through the dust in the spiral arms. NGC 2683 also appears to a boundary object between a LINER and a Seyfert Type 2, both of these are forms of AGN and suggest an active massive black hole at the centre of the galaxy. NGC 2683 lies in front of a large number of faint anonymous galaxies that are much further away. Interestingly NGC 2683 does not appear to be part of a group of galaxies but is a true field galaxy. NGC 2683 is by far the brightest galaxy in Lynx but seems to have been overlooked by many observers. It is part of the Herschel 400 list. NGC 2683 does appear in the WSDSOH Vol 4 and is number 47 in Steven O’Meara’s book of Hidden Treasures. Obviously O’Meara’s observations are done with a 4” telescope but the Webb observations with an 8” suggest that it should easily be visible with that size telescope although to see details a larger telescope will be needed. Walter Scott Houston does say it was easily visible in a 3” telescope.

  Owen Brazell - Galaxy Section Director