Galaxy of the Month in Leo

• NGC 3414 in Leo Minor

  January 2024 - Galaxy of the Month

  Our galaxy this month is the lenticular galaxy NGC 3414 in Leo Minor. First discovered by William Herschel in 1785 it is the central galaxy of the rich galaxy group known as the NGC 3504 group, which in turn is also part of the Leo II group, a series of clusters on the edge of the Virgo cluster. The group is also catalogued as LGG 227, a cluster of 9 galaxies. For more information on the Leo II group see An Atlas of the Universe.

  NGC 3414 is also known as Arp 162 and has a weak AGN of the LINER type. The Arp listing also includes NGC 3418, another nearby lenticular galaxy, although recent classifications suggest that this is a spiral galaxy. Interestingly the gas flows in NGC 3414 appear to follow a spiral pattern, however the gas in the inner part rotates in a different direction for the outer part. Deeper images also show signs of shells so all of this could be due to a recent merger. NGC 3414 also has a very strong bar in images.

  NGC 3414 lies at a distance of perhaps 23 Mpc and NGC 3418 lies perhaps 800,000 lyrs from NGC 3414. If NGC 3414 is at this distance, then it is perhaps 40,000 light-years across, perhaps half the size of our Milky Way Galaxy. NGC 3414 is classified as S0pec.

  It is probable that UGC 5958, a nearby edge on galaxy, is also associated with NGC 3414. Observations in the UV part of the spectrum with the GALEX satellite shows the bright core of NGC 3414 but also shows active regions in both NGC 3418 and UGC 5958 suggesting the galaxies are interacting. There also appear to be a number of dwarf spheroidal galaxies associated with NGC 3414, although these are far beyond amateur visual observations.

  NGC 3414 is bright enough to make it into the Herschel 400 list of the Astronomical League. Observations from the UK suggest that NGC 3414 can be seen in 20cm but NGC 3418 is tough in a 40cm., however other observations suggest that NGC 3418 is visible in 30cm under very dark skies, although the quality of the site here was not defined. The The Night Sky Observer's Guide (NSOG) Vol. 2 suggests that 20-25cm telescopes will show NGC 3418 as a bright core but that 30-35cm is needed to show NGC 3818. Luginbuhl and Skiff (L&S) suggest that 25cm is needed to show NGC 3414 clearly and again it shows a bright core.

  Owen Brazell - Galaxy Section Director

• Arp 232 in Leo

  May 2023 - Galaxy of the Month

  As the skies start to get brighter as we approach the summer season in the northern hemisphere, I have chosen the relatively bright galaxy NGC 2911, also known as Arp 232, as my galaxy of the month. The galaxy is also included in the extended Vorontsov-Velyaminov (VV) catalogue as VV 1290.

  Lying in the constellation of Leo, NGC 2911 was discovered by William Herschel in 1784. It is catalogued as a lenticular galaxy, although unusually for that type of galaxy it does contain a number of dust lanes. Arp catalogued it as an example of his galaxies in fission group, but also suggested that it might have concentric rings. NASA/IPAC Extragalactic Database (NED) suggests it is part of WBL 226, a small group of three galaxies, which also contains NGC 2914 along with UGC 5093.

  The nucleus of NGC 2911 appears to contain an AGN of the LINER type, which suggests there maybe, or have been interactions in the group. The AGN has also been classified as a type 3 Seyfert. There does not seem to be a lot of activity in the nucleus given that NGC 2911 is practically invisible in the UV images from GALEX.

  There is also some confusion in the group as an object (PGC 27167) was found that some sources include as NGC 2912. This cannot be true as studies of the original discovery notes for NGC 2912 show it cannot be this object and the object included in the New General Catalogue of Nebulae and Clusters of Stars (NGC) as NGC 2912 is now thought to be just a star.

  It is unlikely that NGC 2911 is interacting with NGC 2914. The group lies at a distance of perhaps 155 million light-years from us. Perhaps surprisingly for an Arp object there does not seem to have been a lot of research published on it. NGC 2914 was also included by Arp in his catalogue as Arp 137 so you get two Arp objects in the same field. NGC 2914 is also classified as a lenticular galaxy but this time showing what appears to be tidal tails. It may also be an example of a polar ring galaxy.

  The whole group is very compact and all three objects will fall in the field of a high power ultra-wide field eyepiece. A medium power field will also include the galaxy NGC 2919. Some sources suggest that this galaxy may also be part of the NGC 2911 group but it is probably unlikely. The Night Sky Observer's Guide (NSOG) Vol. 2 suggests that this galaxy group maybe more challenging than I suggested and it is a target for 40-45cm scopes and even with those NGC 2914 is no more than a faint patch. UGC 5093 is suggested to be an AV object with that class of telescope. Observations form the UK with a 40cm telescope would fit those notes with NGC 2911 being described as a faint oval.

  Owen Brazell - Galaxy Section Director

• NGC 3432 in Leo Minor

  April 2023 - Galaxy of the Month

  As we move into the brighter spring skies, I have stayed in the constellation of Leo Minor for this month’s GOM.

  NGC 3432 was first discovered by William Herschel in 1785 and was included by Halton Arp in his atlas of peculiar galaxies as Arp 206. It was also added as VV11 in Vorontsov-Velyaminov’s catalogue.

  NGC 3432 appears to be a barred spiral galaxy seen edge-on and is interacting with its neighbour the dwarf galaxy UGC 5983. This interaction appears to be causing intense star formation in NGC 3432 as well as filaments between them. The GALEX satellite image in the UV shows that star formation is occurring throughout the galaxy. Due to the amount of dust the core of the galaxy is not well seen.

  Interestingly despite all the star formation going on NGC 3242 is not classified as a starburst galaxy. This maybe because the number of really massive stars being formed is not that high yet. It is suggested that the interaction with UGC 5983 took place very recently, say less than 400 million years ago and that is not enough for a full starburst to get going, in fact the star formation rate is unusually low at the moment. It appears that both ends of NGC 3432 are strongly warped from the gravitational attraction.

  The pair is thought to lie about 30 million light-years from us. NGC 3432 was home to an unusual transient event catalogued as SN 2000ch, initially catalogued as a type II supernova it was later shown to be an LBV like Eta Car as it underwent numerous brightening events.

  There is a Hubble image on NASA's website, although a more normal coloured image by the HST can be seen on NGC 3432’s Wikipedia page.

  Interestingly the interaction does not appear to have sparked that much star formation in UGC 5983. There is an odd condensation though in NGC 3432 off to its northern end. At about 55,000 light-years across NGC 3432 is a relatively small galaxy. UGC 5983 is only 12-15 thousand light-years across and as such is a dwarf galaxy, about the size of the LMC. Observations suggest that NGC 3432 may hide an AGN of the LINER type at its core.

  The galaxy makes it into a number of popular observing lists including the Astronomical Leagues H400 list and Stephen O’Meara’s The Secret Deep.

  The visibility of the galaxy seems to depend on the observer’s location and the companion galaxy UGC 5983 appears to be very difficult to spot so that is the challenge for larger telescope observers.

  The Night Sky Observer's Guide (NSOG) suggests that in 20-25cm telescopes the galaxy is visible as a long spindle, which is backed up by observations from the UK. In 40-45cm telescopes the suggestion is that it will show some of the mottling in the spindle. Unfortunately, there are no large telescope observations in NSOG. There are also observations of the galaxy with a wide range of telescopes on the Webb Deep-Sky Society Observer's Handbook (WSDSOH) Volume 4.

  I suspect that using a medium power may be best to see this galaxy, although if the seeing and transparency conditions are good then high power may tease out UGC 5983.

  Owen Brazell - Galaxy Section Director

• NGC 3395 in Leo Minor

  March 2023 - Galaxy of the Month

  This month’s challenge is the galaxy pair in Leo Minor, NGC 3395 and NGC 3396, also known as Arp 270 and VV 246. The pair were discovered by William Herschel in December 1785. They are part of the NGC 3430 group, also known as LGG 218, which lists about 15 members lying at about 30 Mpc.

  There are a number of other fainter galaxies in the field that were discovered by Stephan Javelle using a 76cm refractor, these being IC 2604, IC 2605, IC 2608 and IC 2612, although IC 2605 is just a bright spot in NGC 3395. IC 2612 is not associated with the group being a background galaxy.

  UV observations of the group with the GALEX satellite show that large amounts of star formation appear to be going on in both NGC 3395 and 3396 along with the nearby galaxy NGC 3430, in fact NGC 3395 is classified as having a starburst nucleus.

  The galaxies appear to be in the early stages of an interaction and are still separate, although at the calculated distance they would only be about 12 kpc apart, about a third of the distance between our Milky Way and the LMC. The galaxies appear to be overlapping and a bridge and tidal tails have been detected in the pair. The suggestion is that they have already had one close pass and the second will be due in 10 million years or so.

  NGC 3395 has been classified as a distorted spiral and NGC 3396 as Im (a Magellanic style irregular), although with its bright line spectrum it has also been classified as a Wolf-Rayet galaxy because of all the massive star formation going on. NGC 3395 was one of the galaxies that the Rosse team at thought to be spirals after observations using the 72” at Birr.

  Perhaps surprisingly I can’t find an HST image of the pair. One assumes because they have strong infra-red emission, probably caused by the strong star formation, that at some point the JWST will have a look.

  The NGC 3395/3396 pair is one of the best and brightest of the galaxies in the Arp atlas. NGC 3395 makes the Astronomical League’s H400 list, although the brighter of the pair, NGC 3396 does not.

  The galaxies are a close pair so using high power to separate them will work well. A medium power field judiciously placed will also include the low surface brightness galaxy NGC 3430 in the same field of view as the others. This pair should be considerably easier to see than the last two GOM’s.

  There are many reports of people seeing them with a 25cm (10”) scope which suggest both galaxies are easy to see. The Night Sky Observer's Guide Vol. 2 suggests that at a medium power in 40-45cm (16-18”) scopes the pair is well seen and looks like a butterfly. The nucleus of NGC 3395 is almost stellar. The pair have an entry in OOTW in the DSF forum.

  Owen Brazell - Galaxy Section Director

• NGC 3356 in Leo

  February 2022 - Galaxy of the Month

  NGC 3356 is part of a small group of galaxies in Leo. NGC 3356 itself is classified as an Sb disturbed spiral. It was first discovered by William Herschel in 1784. NGC 3356 is also known as VV 529 from Vorontsov-Velyaminov’s catalogue of interacting galaxies.

  The next galaxy in the field, NGC 3349, was found by Marth in 1865. It is also an interacting system and has the designation VV 514. This object is actually a pair of galaxies, although I think Marth only saw a single galaxy here.

  There is also third galaxy, NGC 3362, close by in the same field, which is another Marth discovery. Marth was using Lassell’s 48” speculum metal telescope from Malta for these discoveries.

  NGC 3356 is obviously distorted and NASA/IPAC Extragalactic Database (NED) suggests that the distorting galaxy maybe UGC 5857. NGC 3356 is thought to be at a distance of around 85 Mpc, although the distance estimates vary quite a lot. Deep images show a lot of star forming regions in its spiral arms and it is very blue.

  NGC 3349 is also a very blue spiral galaxy. It has a companion listed as PGC 2800964 which is probably both a real as well as an apparent companion. PGC 2800964 is heavily distorted and lies at about the same distance as NGC 3349 (approximately 375 million light-years). NGC 3349 is also a radio galaxy. It is also possibly a WR type galaxy which suggests a lot of recent star formation. WR or Wolf-Rayet galaxies show the spectra of Wolf-Rayet stars which suggests the presence of a lot of them, which implies a lot of recent star formation to make these massive stars.

  NGC 3362 is another very blue face on spiral. It is classified as Seyfert 2 and is also a radio source. It has a fairly wide spiral structure delimited by many star forming regions and star clusters. It is not physically associated with the other galaxies, being at quite a different distance.

  Perhaps unsurprisngly none of the galaxies mentioned here make it into the Night Sky Observer's Guide (NSOG) or other observing guides. As Herschel found NGC 3356 it should not be that difficult in medium sized telescopes. Marth’s objects tend to be unspectacular so it is likely that a telescope of 40cm+ will be needed to see NGC 3349 and NGC 3362 on a good night. I would be interested to know what aperture Is required to see the second galaxy in the NGC 3349 pair. The whole group fits in the field of view of a modern hyperwide eyepiece at, say 265x. I suspect that to split the two galaxies in the NGC 3349 pair will require higher power and a dark transparent sky.

  Owen Brazell - Galaxy Section Director

• NGC 2872 in Leo

  March 2021 - Galaxy of the Month

  The small trio of galaxies around NGC 2872 in Leo, also known as VV 1284 and Arp 307, where it is included as part of the Double Galaxies class.

  The galaxies in the group were discovered by a number of different observers with the brightest pair of galaxies (NGC 2872 and NGC 2874) being discovered by William Herschel in 1784. It took Mitchell using the 72” at Birr to find NGC 2873 in 1857 however. Whilst observing the group he also found a number of other objects that he believed to be nebulae and one of these was later catalogued as NGC 2871. Unfortunately, this later turned out to be just a star. Another case one suspects of poor seeing making stars look nebulous. The Rosse team also thought they had found another nebula in the area, which it turns was actually a knot in one of the spiral arms of NGC 2874, however it got its own NGC number as 2875.

  NGC 2872 is an elliptical galaxy and possibly an AGN as it has a bright UV core and radio lobes. The group is also known as Holmberg 130. NGC 2872 is interacting with NGC 2874. NGC 2873 is probably only optically associated as it appears to be at a different redshift, otherwise not much seems to be known about it. The Galaxy Zoo project classifies NGC 2873 as a red spiral, one of the new types of galaxy classification to come out of that project. Intriguingly NGC 2874 also seem to be classified as heading that way although the GALEX images show a lot of star formation happening in its arms which is slightly odd if that is the case. Very deep images of NGC 2874 show signs of tidal streamers, possibly from an interaction or merger with a dwarf galaxy. The distance to the group is probably of the order of 110 million light-years (33Mpc). Arp lists the group under his classification of Double Galaxies.

  Hubble does seem to have observed the group a long time ago and no colour images seem to have been made however there is a black and white image.

  

  Interestingly the DSS image of the group shows NGC 2872 as quite a small elliptical. However deeper images from newer surveys (SDSS, PanSTARRS) show it has a bright core and a very much larger extended halo and here it is classified as an E2. Perhaps surprisingly as an Arp galaxy not much research appears to be available on this system.

  The group is very tight so observing this will require high power and steady seeing to split the galaxies. NGC 2872 and NGC 2874 should be quite easy but finding NGC 2873 may be a challenge for larger telescopes. Steven Gottlieb found it very faint even with a 24” and requiring averted vision to hold. Interestingly the group does not make the Night Sky Observer's Guide (NSOG), which is perhaps surprising as it has an Arp designation, it is perhaps time to remember that the core NSOG series is now pretty old and telescope sizes in particular have moved on. It does make Luginbuhl and Skiff (L&S) however where the suggestion is that from high altitude the two brighter galaxies are visible in 15cm but a 30cm shows them better. Interestingly they suggest that NGC 2873 should be visible in 30cm which does not tie in with Steve G’s observation above. I note that with a 25cm from the UK the group was not regarded as particularly impressive.

  Owen Brazell - Galaxy Section Director

• NGC 3245 in Leo Minor

  February 2018 - Galaxy of the Month

  NGC 3245 in Leo Minor is part of a small group of galaxies catalogued as LGG 197. The group also includes the galaxies NGC 3245A, NGC 3254, NGC 3277 and NGC 3265.

  NGC 3245 itself was first discovered by William Herschel in 1784 and is a mildly active galaxy of a type known as a LINER/HII transition object. NGC 3245 is classified as a lenticular galaxy and observations with the Hubble Space Telescope suggests that it contains a supermassive black hole at the centre. The mass of the black hole is probably going to be of the order of 2 x 10⁸ solar masses.

  NGC 3245 appears to form a physical pair with the superthin edge on galaxy NGC 3245A. It should be noted that the use of a letter on NGC designations normally comes from much later cataloguers, often from those using the POSS plates. In this case I believe the A designation comes from the RNGC catalogue of Sulentic and Tifft. The letter designations were also sometimes assigned in the RC2 catalogue which was published slightly later.

  NGC 3245 itself may not be much of a visual challenge as it is quite bright however its companion NGC3245A I think will be and is probably going to be one for observers with larger scopes of 40cm+ aperture in a good transparent sky. NGC 3245A is also classified as a low surface brightness galaxy. Steve Gottlieb in his NGC notes suggests that with his 17.5” telescope from altitude it was an averted vison object at best.

  It is not clear if the pair are tidally interacting, although GALEX images in the UV suggest there is a lot of star formation going on in NGC 3245A. NGC 3245A is also catalogued as RFGC 1796 in the revised flat galaxy catalogue. It is also listed in Alvin Huey’s Observing Flat Galaxies guide. The distance to the NGC 3245/3245A pair is of the order of 21 Mpc.

  Hubble observations, particularly with the NIC (Near Infrared Camera) seem to show dust features near the nucleus of NGC 3245, which is a little unusual for a S0 galaxy. Chandra also showed that there were X-Rays coming from a small jet from the nucleus.

  The other galaxies in the group are substantial distances away on the sky from NGC 3245, of the order of a degree or more so this is not a tight group of galaxies. The other galaxies in the group, with the exception of NGC 3245A, were also discovered by William Herschel, although not on the same sweeps. NGC 3254 was discovered almost a month earlier than the others.

  As such they should be relatively easy targets for medium aperture telescopes, say 30cm aperture. NGC 3265 may however be a bit more challenging as it is much fainter than the others. NGC 3254 is a nice edge on spiral the others are much less interesting.

  Owen Brazell - Galaxy Section Director

• NGC 3430 in Leo Minor

  January 2018 - Galaxy of the Month

  For the first time in the GOM column we head into the constellation of Leo Minor and the nice group of galaxies around NGC 3430. All of the NGC galaxies in the group (NGC 3430, NGC 3425, NGC 3413, NGC 3395 and NGC 3396) were discovered by William Herschel in 1785.

  The area is also littered with IC objects that were discovered by Bigourdan, although almost none of them are real, he was obviously having a bad night!

  The group is listed as LGG 218 which apparently contains 10 galaxies including the main core around NGC 3430. However, it appears from its radial velocity that NGC 3413 is not part of the physical group, just a line of sight addition.

  NGC 3395/6 are also known as Arp 270 and it maybe that Bigourdan saw a knot in the spiral arm of NGC 3395 part of this galaxy pair when he reported the object that became IC 2605. This pair were also noted in the VV catalogue of interacting systems that preceded Arp’s work. Arp 270 has also featured in the DSF OOTW column.

  NGC 3430 itself is classified as a Wolf-Rayet (WR) galaxy, a relatively rare type of galaxy undergoing a strong burst of star formation and showing emission lines in its spectra. The WR phenomena in galaxies are normally triggered by interactions between galaxies and it is thought that NGC 3430 is interacting with NGC 3424 and indeed deep images and radio observations suggest that both NGC 3430 and NGC 3424 do show signs of tidal interaction.

  NGC 3430 was also one of the galaxies that the Rosse team at Birr thought were spiral in nature, and it appears that they were correct in that call in this case. With the exception of NGC 3413 which is a lenticular galaxy all of the others in the field are spiral in nature.

  The group is probably of the order of 90 million light years away, although I have seen distances as close as 76 million light years quoted.

  Arp 270 is a merging galaxy system, probably in the early stages of the merger and there is a lot of star formation going on. There is a sixth NGC galaxy which is also part of the LGG 218 group in NGC 3442 but this is almost a degree north of the main core around NGC 3430.

  The main galaxies are bright enough to be seen in medium aperture telescopes, of the order of 30cm, and the group around NGC 3430 is a nice triple system when using high power. All five galaxies may appear on the same field when using a modern hyperwide eyepiece with a medium power of say 180x.

  Also in the same area is IC 2604, a 14th magnitude galaxy that was discovered by Javelle in 1896. It is also thought to be part of the group and will be a challenge for owners of larger telescopes. So overall an interesting group which appears to have two independent interaction events going on in it.

  Owen Brazell - Galaxy Section Director

• April 2017 - Galaxy of the Month

  NGC 2964 in Leo

  Having put out some very challenging galaxies of the month for the last couple we return to a galaxy grouping that that will be somewhat easier to see without a large telescope (Ed: it's actually on the Herschel 400 list for beginners like me).

  Sometimes known as the Leo triplet 2, or the forgotten Leo triplet, the three galaxies NGC 2964, 2988 and 2970 ride high above the head of Leo. NGC 2964 and NGC 2968 were both discovered in 1785 by William Herschel but NGC 2970 was not discovered until 1828 by John Herschel whilst revisiting his father’s observations.

  The group is an interesting mix of types with NGC 2964 being a spiral (SAB(r)bc), NGC 2968 being classified as I0 and NGC 2970 as E1. The WBL catalogue suggests they are a group and it is numbered WBL 235 and, although the distances are perhaps a bit discordant, it appears to be a true physical group about 80 million light years away or so.

  NGC 2964 is listed as a strong radio source, although does not appear to be an AGN. It is also classified as Markarian 404. In general Markarian galaxies are classified as those with nuclei which emit large amounts of UV light compared to normal galaxies. In the case of NGC 2964 and Mrk 404 it is not actually the nucleus that provides the UV excess that made Markarian classify it but a giant HII region in the spiral arms.

  There is some suggestion of an interaction and light bridge between NGC 2968 and NGC 2970 in deep images and certainly in this linked image by Bernhard Hubl you can see that NGC 2968 is very distorted and appears to have shells around it. Another deep image by Adam Block can be seen at Mount Lemmon SkyCenter (University of Arizona).

  NGC 2970 itself is also listed in the Markarian catalogue as number 405 and is linked with 2968 as an interacting pair. Some of the fainter galaxies in the field also seem to have similar redshifts and may be dwarf galaxies in the system.

  In terms of visibility Harrington in his book Cosmic Challenge suggests all three galaxies may be the range of a 20cm (8”) telescope. I do wonder about this, particularly with reference to NGC 2970 and I think a larger telescope will be needed from typical UK skies at least. Certainly, they were all easily visible with direct vision in less than ideal skies with my 55cm telescope, although NGC 2970 is just a faint dot. All three galaxies should fit in the field of a medium power (x265) modern hyperwide field (100) degree eyepiece, although perhaps lower powers around 180x might be better. I find that with fainter galaxies sometimes pushing the power which darkens the sky background will bring them into view.

  Owen Brazell - Galaxy Section Director

• February 2017 - Galaxy of the Month

  NGC 3801 Group in Leo

  Writing the galaxy of the month article is always a challenge, especially coming up with new targets so I am grateful this month for the suggestion from Andrew Robertson to have the small group of galaxies associated with NGC 3801 as the challenge.

  The group has quite a chequered discovery history, and the usual naming challenges. The brightest galaxy in the group is NGC 3801 and it was discovered by William Herschel, along with NGC 3790. Even the NGC sleuths seem to disagree about who discovered NGC 3806. This could have been either William Herschel or, more probably, John Herschel.

  Although NGC 3806 was bright enough to be seen by William at the time he was using his 18.7” reflector in Newtonian mode rather than in front view mode and Wolfgang Steinicke suggests the extra light loss may have contributed to him not seeing it.

  Some confusion has also reined over NGC 3806 being numbered as NGC 3807 but this is actually a star seen by the team at Birr. They did however discover the other two galaxies in the field, NGC 3802 and NGC 3803. Some software, for instance Megastar 5, still plots NGC 3806 as NGC 3807.

  The group is regarded as a physical system, or at least some of them are, and have been given the designation WBL 347, which lists 5 galaxies in the group. The group is also in the LGG catalogue as number 246, which lists 17 galaxies in the group, an interesting discrepancy. If this is true it would mean that this little group of galaxies covers over 3 degrees on the sky as the LGG survey also includes NGC 3800 and 3853 along with NGC 3768 as part of the group.

  NGC 3801 is classified as a S0 (lenticular galaxy) but as the attached Hubble image shows it has some very strange dust clouds in it which would be unusual for a S0 galaxy including one at right angles to the main axis.

  

  All of this suggests some form of interaction/merger, indeed in the UV NGC 3801 shows an intriguing S shape which suggests the merger hypothesis is the more likely. This is also borne out by looking closely at the SDSS image which shows evidence for shells or streams about the galaxy. It also has a radio jet and this is suggestive of an AGN.

  The SkyTools chart attached also does not mark NGC 3803, it is the fuzzy galaxy above NGC 3802. It is regarded as too faint to mark at this scale.

  Most of the galaxies here are regarded as lenticulars except for NGC 3806 which is a face on spiral.

  Interestingly none of these galaxies appear in Night Sky Observers' Guide (NSOG) or other popular resources, although it is in the AL Galaxy groups and clusters list.

  Owen Brazell - Galaxy Section Director

  We've received some excellent observations of this group of galaxies already!

• April 2013 - Galaxy of the Month

  Hickson 58 Group in Leo

  

  Image Courtesy of the Sloan Digital Sky Survey (SDSS). Click on image for a high resolution version. There is a Megastar© finder chart of the Hickson 58 Group.

  One of the often overlooked Hickson groups is Hickson 58. Consisting of 5 relatively bright NGC objects and spread over a larger area than most other Hickson groups it perhaps is worthy of more attention. The group lies on the Leo/Virgo border (which passes through the middle of the group) and consists of the five galaxies NGC 3817, 3819, 3820, 3822 and 3825. NGC 3822 and NGC 3825 were discovered by William Herschel in 1784. NGC 3817 and NGC 3819 by John Herschel in 1828 and the much fainter NGC 3820 by Heinrich d’Arrest in 1864. It is worth noting that even that was with an 11" refractor so should be visible in moderate sized telescopes. Observations however by the renowned observer Steve Gottlieb suggests that NGC 3820 may be much more difficult to see than that. The group consists of 2 spiral galaxies, one elliptical and perhaps unusually two lenticular galaxies. However to show the difficulty of galaxy classification some sources suggest there are 4 spirals and one elliptical in the group. These are not usually seen outside large clusters of galaxies. Hickson 58 appears to lie at the centre of a loose group of galaxies. Interactions within the group appear to have stripped most of the neutral hydrogen out of NGC 3825 and NGC 3822 itself appears to be very disturbed. The group itself appears to be about 285 million light years distant. If this distance is correct then both NGC 3825 and NGC 3822 are large spirals, about the size of our won Milky Way galaxy.

  There is some confusion over the identities of two of the two galaxies discovered by William Herschel in this group in the NGC. William Herschel observed two galaxies here in March 1784 and then reobserved the field in April 1784 and found two more. The galaxies discovered in March were given the identifications NGC 3848 and 3852. Later observers found nothing at the positions for these but Herschel's descriptions matched 3822 and 3825 so we can conclude that Herschel saw the same objects on two different occasions but got the positions wrong the first time. However some software may still plot these identifications.

  The spread and brightness of these objects makes it a good challenge for imagers and I am surprised to find no amateur images of this group. It also lies between two Abell galaxy clusters in AGG 1354 and AGC 1356 so there will be a nice background of galaxies as well. I suspect that neither of these groups will show anything visually except in the very largest amateur telescopes.

  Owen Brazell - Galaxy Section Director

• March 2013 - Galaxy of the Month

  M96 Group

  

  Image Courtesy of Adam Block, Arizona. For more images from Adam Block please visit his website. You can click on image for a high resolution version.

  First discovered by Pierre Mechain in 1781 along with M95 and M105. M96 is a Barred spiral classified as SAB(rs)ab. About 100 thousand light years across and at about 10.8 Mpc or 36 million light years away. M96 is about the size of our own Milky Way galaxy. The nucleus of M96 displays weak AGN type activity and is classified as a LINER.

  Messier received the information on his finding of M95 and M96 these galaxies from Mechain and observed M95 and M96 himself about 4 days later. Mechain found what became M105 a few days later and Messier did not have a chance to observe it and put it in the final printed catalogue. M105 was added in 1947 by Helen Sawyer-Hogg as an extension to Messer’s catalogue.

  In 1998 a supernova (1998bu) was seen in M96 and proved to be of type Ia. The supernova was of interest because M96 is near enough for the Hubble Space Telescope to measure its Cepheid’s and thus provide an independent confirmation of the standard candle distances from Type Ia supernova.

  M96 is one of the dominant members of the M96 group of galaxies that also contains M95 and M105. There are perhaps 8 bright galaxies in this group and may be 16 others. Also known as the Leo I group it may also include the better known Leo Trio (M65, 66 and NGC 3568). The Leo I group is a subgrouping (like our own Local Group) of the Virgo cluster. It is possible that the Leo I group and M65 group are sub clusters of a larger grouping as well.

  Intriguingly there is a giant ring of neutral Hydrogen (HI) gas which surrounds the Leo I group with a diameter of perhaps 200 kpc. Although centred on M105 the ring also has traces out to M96. The ring has two possible origins being either primordial or the result of a collision with another galaxy, possibly NGC 3384, in the past. Probably the most likely scenario is the collisional one. Ultraviolet observations with the GALEX satellite suggest that there may be clumps of OB stars forming in this ring.

  Observationally although M96 can be seen with small telescopes it will require larger instruments to make out any form. The whole group is a bit to spread out to be seen in a single eyepiece field except with wide field telescopes and here only a smudge may be seen. There are several other galaxies to be seen in the field particularly around M105, although many of these come under the very faint description. Although perhaps not quite as spectacular as the Leo triplet this is a group worth going after and is often overlooked.

  Owen Brazell - Galaxy Section Director

• March 2012 - Galaxy of the Month

  Abell 1367 in Leo

  

  Image Credit - Svend and Carl Freytag/Adam Block/NOAO/AURA/NSF. Click on image for a larger version.

  Galaxy clusters are some of the most interesting objects for observers as you can, in many cases, see multiple objects in one eyepiece field. Most observers are familiar with the Virgo and Coma clusters but Abell 1367 in Leo is often overlooked which is disappointing as there are 21 NGC galaxies in this field and with larger telescopes you can see up to 20 galaxies in the same eyepiece field.

  Abell 1367, also known as the Leo Cluster, is one of the richest of the nearby galaxy clusters however its brightest galaxies are spread randomly throughout its extent with many sub concentrations. Given the cluster diameter is about 100 arcminutes (so three the diameter of the full moon) this means you have to scan across the field to find all the sub-concentrations.

  I was introduced to Abell 1367 long ago via the Webb Society Deep-Sky Observer's Handbook (WSDSOH) Volume 5. This was one of my first attempts at a galaxy cluster from outside the normal run and I remember a cold night in Wales using a 16" whilst the others slept and being astonished by the number of galaxies I could see.

  The view of the cluster is somewhat hampered by a bright seventh magnitude star which is near the core of the cluster around the giant elliptical galaxy NGC 3842.

  The cluster does appear to have a higher ratio of spiral to elliptical galaxies than most clusters and as such is believed to have formed relatively recently as one would have expected the spiral galaxies to be destroyed by mergers and interactions over time. Indeed a number of the spiral galaxies appear to show tails in the radio which suggests matter being stripped out as they plunge through the intra cluster gas.

  There is a fine finder chart for the cluster which labels the main galaxies in the group. Even more detailed charts can be got from Alvin Huey's fine downloadable guide (also available in hardcopy from the Webb Deep-Sky Society).

  You should also take a look at Steve Gottlieb's observations where he identifies 63 cluster members.

  The WSDSOH lists 47 galaxies in the cluster and provides observations of many. Abell 1367 also features in Philip Harrington's excellent book Cosmic Challenge.

  The cluster is at about 95 Mpc from us and has an Abell classification of 2 1 II-III. When searching for information on the web use either Abell 1367 or AGC 1367 as it appears to be referenced under both. Abell 1367 together with Abell 1656 form the Coma super cluster which is the closest supercluster to the Virgo cluster of which our Local Group is a part. Both of these clusters along with the Hercules cluster appear to be part of a group of galaxies dubbed the Great Wall.

  Owen Brazell - Galaxy Section Director

• February 2012 - Galaxy of the Month

  NGC 3607 Group in Hercules

  

  Image Credit - Prof. Duncan A. Forbes, Swinburne University of Technology, Australia. Click on the image above for a larger version or visit Prof. Forbes web pages for more of his images. We also have a Megastar© chart of the NGC 3607 region.

  Our challenge for February is the galaxy group associated with NGC 3607. There are 3 galaxies intimately involved with this group which are NGC 3607, NGC 3608 and NGC 3605. The first two should be relatively easily seen in small telescopes.

  NGC 3607 is classified as SA(0) which is a lenticular galaxy. These are galaxies that appear to have the luminosity profile of a spiral but have no (or little) gas and dust and are normally found in clusters. NGC 3608 is an early type elliptical. It would appear that NGC 3607 and NGC 3608 are interacting and that the former maybe stealing material from its neighbour. Backing this theory up is the fact that NGC 3607 is a low luminosity active galaxy.

  NGC 3505 is much fainter and will require a larger telescope to see. It is also an elliptical galaxy but with a classification of E5 much more squashed. It is probably not associated with 3607 and 3608 but a background galaxy.

  The NGC 3607 group contains perhaps 14 galaxies and is part of the much larger Leo II groups of galaxies. This is a collection of small galaxy groups, probably not that much dissimilar to our own local group at a distance of perhaps 70-90 million light years. There appear to be 11 major groups in the Leo II cluster along with a number of other NGC galaxies. They are all part of the Virgo cluster.

  In the same medium power field as NGC 3607 there is also the galaxy NGC 3599 which is another relatively bright lenticular. All of these galaxies were discovered by William Herschel in 1784. NGC 3599 is not physically associated with the 3607 group.

  Much closer in to NGC 3607 is the very much fainter galaxy MCG +3-29-18 which at magnitude 16.3 is going to be a challenge for large scope observers and is perhaps more suited to imagers. This is also probably a background galaxy.

  NGC 3607 itself is a part of the RASC’s (Royal Astronomical Society of Canada) finest NGC list and as such should perhaps be better known that it is. The brightest galaxies in the NGC 3607 group are NGC 3607, NGC 3626, NGC 3686, NGC 3608 and NGC 3684. Because of its relative nearness the group spreads across perhaps 4 degrees of sky. If you like galaxy trios then NGC 3681, 3684 and 3691 are also a nice trio of galaxies that should show in the same medium power field with a medium sized telescope.

  Owen Brazell - Galaxy Section Director