Galaxy of the Month in Pisces

• NGC 7603 in Pisces

  September 2023 - Galaxy of the Month

  As the galaxy fields of autumn roll around, I have chosen NGC 7603, also known as Arp 92, in Pisces for the galaxy of the month. First discovered in 1864 by Albert Marth using William Lassell’s 48” speculum metal mirror telescope from Malta.

  Arp included it in his group of spiral galaxies with an elliptical companion. NGC 7603 appears to be interacting with the small elliptical galaxy PGC 71041 nearby, indeed there appears to be a filament connecting the two galaxies. Arp 92 is at the centre of various controversies about cosmological redshifts due to the fact there are two quasars involved with the filament, one at either end, note the dots in the accompanying SDSS image, as well which Arp and Hoyle took to mean they were connected and thus quasars were not at cosmological distances.

  NGC 7603 itself is a distorted spiral galaxy. It seems that occasionally PGC 71041 is also known as NGC 7603B. NGC 7603 is classified as a Seyfert class 1 AGN, although its type seems to have varied over the last 20 years or so due to changes in its spectrum. NGC 7603 is also a very strong blue source catalogued as Mrk 530.

  There are however issues with PGC 71041 being the cause of the interaction as it appears to be nearly twice as far away than NGC 7603. The fact that the spiral arm/filament overlies it appears to be totally coincidental. One other possible candidate for casing the disruption is the barred spiral NGC 7589 which appears to be at the same distance as NGC 7603. It is also possible that the plumes from NGC 7603 are the result of a merger event rather than an interaction.

  There do not seem to be any high-quality images of Arp 92 taken by the HST, but there is one image on Wikipedia. This is a relatively raw/ unprocessed Hubble image as evidenced by all the cosmic ray streaks.

  NGC 7603 would appear to lie at a distance of about 127 Mpc. It was also included in the extended VV catalogue of interacting galaxies as VV 1975.

  It is interesting that given the usual Arp mania there are no observations of Arp 92 in The Night Sky Observer's Guide (NSOG). I note that both Steve Gottlieb and Alvin Huey felt that NGC 7603 was not too hard to find in their large instruments but the companion was very faint in 50cm class telescopes and not surprisingly no spiral structure was seen. Both NGC 7603 and NGC 7589 should appear in the same field with a medium power eyepiece, however as both are quite faint it is probably worth using the highest power eyepiece you can that fits them both in the same field to find them. In Steve Gottlieb's complete NGC observations (on Adventures in Deep Space) he also has observations of the pair with a 48” Dobsonian.

  Owen Brazell - Galaxy Section Director

• NGC 470 in Pisces

  October 2022 - Galaxy of the Month

  Our galaxy of the month this month is the tight triplet of galaxies in Pisces around NGC 470. I must thank Mark Stuart for recommending this group to me. The triplet includes NGC 467, NGC 470 and NGC 474. All three galaxies were found by William Herschel. NGC 470 and NGC 474 in 1784 and then NGC 467 a year later in 1785.

  NGC 470 is a disturbed system and was included by Vorontosv-Velyaminov as number 948 in his extended catalogue. NGC 474 is also a disturbed system and Arp included it as Arp 227. It is not clear whether Arp meant Arp 227 to include both NGC 470 and NGC 474, or just NGC 474.

  Arp 227 is a shell galaxy and appears to be in a physical pair with NGC 470. The pair lie at about 100 million light-years from us. NGC 467 is also a shell galaxy but is much further away than the others, although some older sources do suggest it is gravitationally part of the NGC 474 group. NGC 467 is also suggested to be a lenticular galaxy.

  Shell galaxies are relatively rare, with maybe 10-20% of galaxies in this class, so to get two in the same field is unusual. Shell galaxies come about when another galaxy has been digested and the stars thrown out from the interaction form these shells. It would appear that NGC 474 ingested a spiral galaxy in two phases, the first pass being about 1.3 billion years ago and the final pass about 900,000 million years ago. It is not clear if NGC 470 is gravitationally interacting with NGC 474 as well.

  NGC 470 has some very chunky spiral arms and there are some suggestions of plumes in deep images. NGC 470 shows up strongly in the GALEX UV images which suggests that there is a lot of star formation going on in it. The other two galaxies barely register in the UV.

  Hubble took a nice image of NGC 474. NGC 474 would appear to be about 2.5 times the size of our Milky Way at about 250,000 light-years across. There is also a Canada France Hawaii Telescope (CFHT) image of both NGC 470 and NGC 474. NGC 474 seems to be catalogued as a lenticular galaxy, although there were suggestions that it may be an elliptical.

  The galaxy trio is pretty tight so all the galaxies will fit in the same field in a modern hyperwide eyepiece at medium to high power. The presence however of the 8th magnitude star HD7991 in the field may make finding NGC 467 more difficult than it might be. The Night Sky Observer's Guide (NSOG) Volume 1 suggests the whole group should be visible in 20-25cm telescopes but recommends 30-35cm for this. The NSOG also suggests that NGC 470 and NGC 474 have very bright nuclei but the rest of the galaxies are rather faint. Given the poorer skies of the UK I suspect that 40cm may be required to see much.

  Owen Brazell - Galaxy Section Director

• NGC 315 in Pisces

  August 2022 - Galaxy of the Month

  For the August galaxy of the month I have chosen NGC 315 in Pisces. Although perhaps a bit early for galaxies in Pisces, we are still in Milky Way season. NGC 315 was discovered by William Herschel in 1784. It appears to be part of a small group on the sky that also contains NGC 311 and NGC 318.

  NGC 315 contains an AGN, in this case a LINER, with a well collimated radio jet coming from the central black hole. The jet has also been detected in X-Rays. The jet appears as two main parts, a bright main jet and a smaller counter jet. The mass of the central black hole has been calculated to be of the order of 2x10⁹ solar masses from observations of cold molecular gas around it using ALMA. The nucleus also shows up well in the UV images from the GALEX satellite.

  There may be upwards of 30 galaxies in the group associated with NGC 315. NGC 315 is part of Zwicky cluster 0107.5+3212 (Zwicky et al. 1961), which is located in the Perseus-Pisces filament. It is also part of the group WBL 22 (which only contains NGC 311, NGC 315 and NGC 318) and LGG 14 (which contains many more). NGC 315 is classified as a cD elliptical galaxy; these are large elliptical galaxies found at the core of clusters. The group is thought to be at a distance of perhaps 55 Mpc. Most studies of this galaxy seem to concentrate on the jet.

  Observationally NGC 315 is defined to be part of a trio of galaxies including NGC 311 and NGC 318. NGC 311 and 318 are much fainter than NGC 315. NGC 311 was discovered by John Herschel in 1828 and NGC 318 by Bindon Stoney using Lord Rosse’s 72” telescope in 1850. They both appear to be lenticular type systems. Stoney also thought he discovered another two galaxies in the field that got the NGC numbers NGC 313 and NGC 316 but it turns out these were just stars.

  Night Sky Observer's Guide (NSOG) suggests that all three can be seen with a 35cm telescope, although NGC 318 is recorded as difficult to see. My suspicion however is that these observations were made from high altitude sites and from the UK it may require 40cm to see all three given the extra mile of crud above most UK observing sites. The group is a very tight one and will easily fit in a high power eyepiece field. Observations of the group maybe complicated by an 8th magnitude star close by in the field. NGC 315 is included as part of the Astronomical League H400 II list.

  Owen Brazell - Galaxy Section Director

• NGC 128 Group in Pisces

  October 2020 - Galaxy of the Month

  The small group of galaxies around NGC 128 in Pisces, also designated as LGG 6, was first discovered by William Herschel who found NGC 128 itself along with NGC 125 in 1790 using his 18.7” 20 foot reflecting telescope. NGC 126, NGC 127 and NGC 130 had to wait until 1850 when Bindon Stoney discovered them whilst examining the area using Lord Rosse’s 72” telescope.

  The LGG 6 group is composed of 11 galaxies including NGC 128, NGC 126, NGC 127 and NGC 130. Nearby MCG +0-2-45 is also associated with the group.

  NGC 128 itself appears to be interacting with NGC 127 and there is a tidal tail between the two. NGC 128 itself is an interesting galaxy as, although it is classified as a lenticular, it shows a boxy or peanut shaped nucleus with a strange X form. This could be the result of a previous merger or the ongoing interaction between itself and NGC 127. Although NGC 125 is also a disturbed galaxy it does not appear to be associated with NGC 128.

  NGC 125 appears to be a form of shell galaxy. This is shown up well in the image on the CHART32 website. Deep images suggest that NGC 126 also shows some sign of tidal tails so it is also undergoing a gravitational interaction, probably also with NGC 128. It appears that NGC 130 is also interacting with NGC 128 as well.

  There were some suggestions that NGC 125 might also be part of the group but its recession velocity is much larger than the others. The possibility remains however that NGC 128 and 125 have interacted in the past. The interaction of NGC 128 with NGC 127 is thought however to be a relatively recent phenomenon and has produced a counter rotating disk of stars in NGC 128 aligned with NGC 127.

  The interacting part of the group was also catalogued in the Vorontsov-Velyaminov of interacting galaxies as VV 894. The group also makes it into the WBL catalogue of poor clusters as WBL 10 and that group includes NGC 125 but not some of the others included in LGG 6. The group lies at a distance of perhaps 190 million light years from us.

  The group may be a tough one to observe with smaller telescopes. The Night Sky Observer's Guide (NSOG) suggests that only NGC 125 and NGC 128 will be visible in 10-12” scopes whilst the others may need telescopes in the 20” class to see, at least from UK skies. Observations with a 22cm from the UK suggest that NGC 128 was hard and that NGC 125 was not seen. Using a 37cm scope under mediocre skies showed NGC 128 as an edge on and NGC 125 as a circular patch. The other galaxies were not seen.

  

  The group is fairly tight so the use of high power is recommended in order to pick up the fainter members. They should all fit in the field of a modern hyperwide eyepiece at 350x. The fainter MCG member of the group is still close by and will again fit in the same field as the others when using a power around 260x. This is likely to be a challenge however for telescopes in the 20”+ class.

  Owen Brazell - Galaxy Section Director

• NGC 7778 in Pisces

  October 2019 - Galaxy of the Month

  My thanks to Mark Stuart for recommending this rather nice group of galaxies in Pisces. Three of these galaxies, NGC 7778, NGC 7779 and NGC 7782 were discovered by William Herschel in November 1784 and the fourth galaxy NGC 7781 was discovered by his son, John, in 1830 whilst reobserving his father’s objects. Also in this field, but very much fainter is the edge on galaxy, RFGC 4209.

  All of the NGC galaxies are included as a group WBL 727 which contains just the four NGC galaxies. The group is often called the NGC 7782 group after its brightest member. It also seems to be classified as cluster Zwicky 2350.6+0758.

  NGC 7778 and NGC 7779 are regarded as a physical pair, despite this they do not seem to show any signs of gravitational interaction. NGC 7778 is an elliptical whereas NGC 7779 appears to be a face on spiral with a very bright core, although it has also been classified as a lenticular galaxy. Both of these galaxies were digitised as stars in the GSC catalogue due to their bright cores.

  The group lies at a distance of perhaps 70 Mpc. The group is classified as a triple system in Alvin Huey’s guide to Galaxy Trios. Interestingly he does not include NGC 7782 as part of the triple but adds NGC 7781.

  Whilst NGC 7778 and NGC 7779 should be visible in relatively small instruments NGC 7781 will be far more of challenge with a listed blue magnitude of 15. It may be much brighter however in the visual, perhaps at 14th magnitude, nevertheless I would expect that from UK skies at least 40-cm will be needed to see it.

  The Night Sky Observer's Guide (NSOG) also includes a fifth galaxy, NGC 7780, in this group. Although probably not physically associated with the NGC 7782 group, NGC 7780 was discovered by Stephan in 1881 and independently by Swift in 1886. Both NGC 7780 and NCG 7781 are likely to be challenges for 45-cm telescopes according to the NSOG. NGC 7780 was host to sn 2001da. If these prove too easy then near NGC 7780 is MCG+1-60-44 for large telescopes.

  All five NGC galaxies should fit in the field of view of a medium power (240x) modern hyperwide (100 degree) eyepiece.

  If these galaxies are all too easy then try for RFGC 4209. I am not sure if RFGC 4209 will be visible in normal amateur class instruments however, perhaps some of the giant Dobsonians that seem to be around could give it a go. Here RFGC stands for the Revised Flat Galaxy Catalogue by Karachentsev et al. There are 4236 galaxies in this catalogue with axial ratios (a/b)B ≥ 7. Within this group RFGC 4209 would be classified as an Ultra thin. It is also known as LEDA 091829 but has no listed magnitude. It is not part of the group being much more distant. There is some interesting information and an image of this group at ManTrapSkies.

  Owen Brazell - Galaxy Section Director

• September 2016 - Galaxy of the Month

  NGC 741 in Pisces

  This interactive image of the NGC 741 group was provided by the Sloan Digital Sky Survey using Aladin Sky Atlas. We also have a finder chart should help you locate these galaxies.

  The galaxy pair NGC 741 and 742 were first discovered by William Herschel in December 1784 using his large 20 foot telescope. They are part of a small group of galaxies listed as WBL 61 which, along with NGC 741 and 742, also contains the galaxies UGC 1425 and 1435 along with a couple of anonymous small galaxies.

  The group does have some nomenclature confusion (as always) in the NGC/IC as a small galaxy close by the main pair is listed as IC 1751 and displayed as such in star charting programs such as Megastar and SkyTools. It is now known that in fact IC 1751 is a duplicate observation of NGC 741 and the galaxy formerly known as IC 1751 should now be called MCG 1-6-6. It is also part of the WBL 61 group.

  The main pair of galaxies appear to be interacting and probably had a collision a few 10’s of million years ago. It is likely that this interaction between NGC 741 and NGC 742 took the form of an almost head on collision.

  

  NGC 741 would also appear to be an inactive AGN as it shows an old faint radio lobe. There appears to be both a radio and an X-Ray filament linking NGC 741 and NGC 742 as well as a hot gas bubble in the group. Both NGC 741 and 742 show point radio sources at their core which suggests the collision was not too disruptive. The results of the collision mirror the optical remnants of the more well-known Taffy Galaxies UGC 12914/12915.

  In terms of group morphology NGC 741, NGC 742 and MCG 1-6-6 are all elliptical galaxies. UGC 1425’s type is unknown but it is probably either an elliptical or lenticular whilst UGC 1435 is probably a spiral galaxy. The interacting pair NGC 741/742 are also known as VV175. NGC 741 is a giant elliptical galaxy that appears to be the centre of a group of approximately 40 galaxies in total. The deep SDSS image shows a lot of faint galaxies in the area.

  Visually NGC 741 should be seen in perhaps 20cm but to see NGC 742 will require probably 30cm and a high power to separate from NGC 741. To get the third member of the triplet MCG 1-6-6 will probably require a telescope in the 40cm class and good skies. The two fainter galaxies may just appear as stellar spots. NGC 741 is also part of the Herschel II list from the AL. I suspect that to pick up the UGC galaxies visually, especially from the UK, will require 50cm aperture or better.

  Owen Brazell - Galaxy Section Director

  A few of our members have provided observations for this field.

• October 2015 - Galaxy of the Month

  NGC 7541 in Pisces

  This interactive image of the NGC 7541 / NGC 7537 pair of galaxies was provided by the Sloan Digital Sky Survey using Aladin Sky Atlas. We've also provided a finder chart for the group too.

  The galaxy pair NGC 7541 and NGC 7537 in Pisces were both discovered by William Herschel in 1785, although NGC 7541 may also be the nebulous object which was seen by Horace Tuttle in 1875 whilst looking for Encke’s comet and later catalogued as NGC 7581. They are both located within the circlet of Pisces.

  NGC 7541 and NGC 7537 are probably a true galaxy pair, although this is not 100% certain. They are both spiral galaxies at a distance of around 33 Mpc. NGC 7537 is classed as Sbc and NGC 7541 as SBc i..e. a barred spiral. Both galaxies are see close to edge on. At this distance NGC 7537 would be about 94000 light years across and NGC 7541 about 145000, so comparable in size to our Milky Way galaxy.

  NGC 7541 was home to the type Ia supernova 1998dh. Not to be outdone NGC 7537 was home to supernova SN 2002gd. This would appear to have been a Type II-p.

  It would appear from X-Ray observations that NGC 7541 is currently undergoing a period of high star formation. Whether this is in anyway related to a gravitational interaction with NGC 7537 is questionable.

  In 1999 astronomers combined images from two different camera on the Hubble space telescope to try and estimate the ages of the stars in the central regions of NGC 7537. This study appears to suggest that the bulges of spiral galaxies formed in a relatively short time in the early universe. This may have happened by the collapse of a single large gas cloud or by the merger of large star clusters.

  Both these two galaxies appear in NSOG Vol 1 and would appear to be visible in telescopes in the 20-22cm category, although instruments with a larger aperture will be required to see much detail. Both galaxies are also described in Luginbuhl and Skiff’s Observing Handbook and Catalogue of Deep Sky objects as reasonable in 25cm but easier with 30cm. NGC 7537 is fainter of the two and may require a larger aperture to be sure of.

  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

• November 2011 - Galaxy of the Month

  The NGC 383 Group of Galaxies (Arp 331)

  

  Image Courtesy of James Shuder, San Francisco, CA. Click on image for a larger version. For more images from James please visit his Image Gallery. The linked finder chart for NGC 383 will help identification of the galaxies and is courtesy Megastar.

  The NGC 383 group of galaxies, also known as Arp 331 has become popularly known as the Pisces chain or Pisces cloud. The group is part of the much larger Perseus-Pisces supercluster. The main core of the group is a line of galaxies centred on NGC 383 which consists mostly of Elliptical and S0 type galaxies. NGC 383 along with 379 and 380 were discovered by William Herschel in 1784. The rest of the group was discovered by Lord Rosse and colleagues at Birr with the 72".

  NGC 383 itself is a double radio galaxy with a quasar like appearance. The radio nature was discovered during the third Cambridge Survey (3C 31) and it has radio jets that appear to be interacting with the intergalactic medium. The jets have also been observed in the infra-red by Spitzer. Deep Hubble images of NGC 383 show dust arms circling the core of the galaxy. It is classified as SA0 so basically it shows the luminosity profile of a spiral galaxy but without arms. The centre of the cluster is also a strong source of X-Ray emission which appears to be coming from relativistic electrons from the jets of NGC 383.

  The full Pisces group consists of maybe 25 galaxies and was discovered by Hubble and Humason in 1931. The galaxy consisting of NGC 375, 379, 380, 382, 383, 385, 386, 387 and 388 together are listed as No. 331 in Arp's "Atlas of Peculiar Galaxies" under galaxy chains.

  Supernova SN 2000dk was found in NGC 382 which is the close companion to NGC 383. The main chain of galaxies here consists of 8 galaxies, although I feel that a relatively large telescope in the 40+cm class will be required to see all of them. The three discovered by Herschel should be visible in say 22cm. Outside the main group there are a number of other galaxies in the 14th-16th magnitude range that are probably part of the same group.

  The NGC 383 group is probably about 65 Mpc away and the suggestion is that unless there is a lot of dark matter in the system it cannot be gravitationally stable. The group does feature in the WSDSOH Volume 5 where George Whiston observed many of its members with a 16". It appears that as with many of these galaxy groups that once you have found them switch to medium or high power to pick up the fainter members. Also check Steve Gottlieb's observations.

  The NGC 507 group of galaxies is also known as the Pisces cluster so there can be some confusion. It is also one of the major subgroups in the Perseus-Pisces supercluster. The major constituents of this super cluster are the galaxy clusters Abell 262, 347 and 426.

  Owen Brazell - Galaxy Section Director