mirrored file at http://SaturnianCosmology.Org/ For complete access to all the files of this collection see http://SaturnianCosmology.org/search.php ========================================================== The Local Group of Galaxies This is "our" group of galaxies <../g-group.html>. It was first recognized by Hubble, in the time of the first distance determinations and redshift measurements (see, e.g., his /The Realm of the Nebulae/). Messier objects: The Andromeda Galaxy M31 <../m/m031.html> and its satellites M32 <../m/m032.html> and M110 <../m/m110.html>, as well as the Triangulum Galaxy M33 <../m/m033.html>. Other members (over 30 in all) include our Milky Way Galaxy , the Large and the Small Magellanic Cloud (LMC <../xtra/ngc/lmc.html> and SMC <../xtra/ngc/smc.html>), which have been known before <../xtra/histlist/histlist.html> the invention of the telescope, as well as several smaller galaxies which were discovered more recently. These galaxies are spread in a volume of nearly 10 million light years diameter, centered somewhere between the Milky Way and M31. Membership is not certain for all these galaxies, and there are possible other candidate members. Of the Local Group member galaxies, the Milky Way and M31 are by far the most massive, and therefore dominant members. Each of these two giant spirals has accumulated a system of satellite galaxies, where * the system of the Milky Way contains many (nearby) dwarf galaxies, spread all over the sky, namely Sag DEG , LMC, SMC, the recently discovered and widely disrupted Canis Major Dwarf , and the dwarf galaxies in Ursa Minor, Draco, Carina, Sextans (dwarf), Sculptor, Fornax, Leo I, Leo II, and perhaps the Phoenix Dwarf, and Leo A (which may alternatively belong to the NGC 3109 subgroup), * the system of the Andromeda galaxy is seen from outside, and thus grouped around its main galaxy M31 in Andromeda, containing bright nearby M32 and M110 as well as fainter and more far-out NGCs 147 and 185, the very faint systems And I, And II, And III and possibly And IV (but for this one see remark below <#and4>), And V, And VI (Pegasus dwarf), And VII (Cassiopeia dwarf), and And VIII. The third-largest galaxy, the Triangulum spiral M33, may or may not be an outlying gravitationally bound companion of M31, but has itself probably the dwarf LGS 3 as a satellite. Also, IC 1613 may perhaps be a member of the M31 subgroup, as may be the doubtful members UGCA 86 and UGCA 92. * There is a third potential subgroup around irregular galaxy NGC 3109, which contains Sextans A, Sextans B, the Antlia Dwarf and perhaps Leo A (but that one may belong to the Milky Way subgroup). * The other members, mostly dwarf irregulars, cannot be assigned to one of these main subgroups, and float quite alone in the gravitational field of the giant group members. They tend to form a vast cloud, the Local Group Cloud. Only one dwarf galaxy, GR 8, seems to be so isolated that it doesn't belong to any of these substructures. The substructures of the group are probably not stable. Observations and calculations suggest that the group is highly dynamic and has changed significantly in the past: The galaxies around the large elliptical Maffei 1 have probably been once part of our galaxy group. As this shows, the Local Group is not isolated, but in gravitional interaction, and member exchange, with the nearest surrounding groups, notably: * the Maffei 1 group <../xtra/ngc/maffei1g.html>, which besides the giant elliptical galaxy Maffei 1 also contains smaller Maffei 2, and is associated with nearby IC 342 and a number of smaller galaxies. Highly obscurred by dark dust near the Milky Way's equatorial plane. * the Sculptor Group or South Polar Group <../xtra/ngc/sclgr.html> (with members situated around the South Galactic pole), dominated by NGC 253 <../xtra/ngc/n0253.html> * the M81 group * the M83 group The next more distant galaxy groups, the NGC 4244 group and the CVn I Cloud (with M94 <../m/m094.html> and M64 <../m/m064.html>) are probably too remote to have interacted significantly with the Local Group in the past. It is of interest that of the subgroups of the Local Group mentioned above, the NGC 3109 group tends to the general direction of the Maffei 1 group and the M81 group, while the Local Group Cloud tends to the general direction of the Sculptor Group. In the future, interaction between the member galaxies and with the cosmic neighborhood will continue to change the Local Group. Some astronomers speculate that the two large spirals, our Milky Way and the Andromeda Galaxy, may perhaps collide and merge in some distant future, to form a giant elliptical (see a summary of a possible scenario ). In addition, there is evidence that our nearest big cluster of galaxies, the Virgo Cluster , will probably stop our cosmological recession away from it, accelerate the Local Group toward itself so that it will finally fall and merge into this huge cluster of galaxies, see our Virgo Cluster & Local Group page . A table of the currently known Local Group member galaxies follows. While the positions are known very acurately, the distances are only very vaguely known for some members, and the sources even disagree for the most prominent members such as M31 and M33. If interested, look at our compilation of distances from various sources . Please note that this table is currently under review, as new data (Hipparcos distances, discovery of new members) keep our knowledge in flow. *Local Group Member Galaxies* *Galaxy RA Dec Type m_v dim RV Dist* ------------------------------------------------------------------------ *WLM <../xtra/ngc/wlm.html>* 00:02.0 -15:28 IB(s) IV-V 10.9 12 x 4 - 42 3400 *IC 10 <../xtra/ngc/i0010.html>* 00:20.4 +59:18 KBm? 10.3 7.3 x 6.4 - 83 4200: *Cet dw* 00:26.1 -11:02 dSph/E4 14.4 2800 *NGC 147* 00:33.2 +48:31 dE5 pec 9.5 15.0 x 9.4 + 89 2400 *And III* 00:35.4 +36:31 dSph/E2 13.5p 4.5 x 3.0 2900: *NGC 185* 00:39.0 +84:20 dE3 pec 9.2 14.5 x 12.5 + 39 2300 *M110 <../m/m110.html>* 00:41.3 +41:41 E5 pec 8.5 19.5 x 12.5 - 1 2900 *And VIII* 00:42.3 +40:37 dSph pec 9.1 45 x 10 -250 2700: *M 32 <../m/m032.html>* 00:42.7 +40:52 E2 (cE2) 8.1 11.0 x 7.3 + 35 2900 *M 31 <../m/m031.html>* 00:42.7 +41:16 SA(s)b I-II 3.4 185.0 x 75.0 - 59 2900 *And I* 00:45.7 +38:00 dSph/E3 pec ? 13.2 2.5 x 2.5 2900: *SMC <../xtra/ngc/smc.html>* 00:51.7 -73:14 SB(s)m pec 2.3 280 x 160 - 30 210 *And IX* 00:52.9 +43:12 dSph 16.2 5 2900: *Scl dw* 01:00.0 -33:42 dSph/E3 pec 10.5p +162 300: *LGS 3* 01:03.8 +21:53 Irr 15.4p 2 3000: *IC 1613* 01:05.1 +02:08 IAB(s)m V 9.2 20.0 x 18.5 -125 2900: *And V* 01:10.3 +47:38 dSph 15.9 2900: *And II* 01:16.4 +33:27 dSph/E0 13.5 3.6 x 2.5 2900: *M 33 <../m/m033.html>* 01:33.9 +30:39 SA(s)cd II-III 5.7 67.0 x 41.5 + 3 3000 *Phe dw* 01:51.1 -44:27 Irr 13.1 4.9 x 4.1 1600: *For dw* 02:39.9 -34:32 dSph/E2 8.1 12.0 x 10.2 500 *UGCA 92* 04:32.0 +63:36 Irr ? S0 ? 13.8 2.0 x 1.0 + 66 4700 *LMC <../xtra/ngc/lmc.html>* 05:19.7 -68:57 SB(s)m 0.1 650 x 550 + 13 179 *Car dw* 06:14.6 -50:58 dSph/E3 20.9 23.5 x 15.5 360 *CMa dw * 07:15 -28 Irr 720 25 *Leo A* 09:59.4 +30:45 IBm V 12.9 5.1 x 3.1 2500 *Sex B* 10:00.0 +05:20 Ir+ IV-V 11.8 5.1 x 3.5 4700 *NGC 3109* 10:03.1 -26:09 Ir+ IV-V 10.4 16.0 x 2.9 +131 4500 *Ant dw* 10:04.1 -27:20 dSph/E3 14.8 2.0 x 1.5 4600 *Leo I <../xtra/ngc/leo1.html>* 10:08.5 +12:18 dE3 9.8 9.8 x 7.4 900 *Sex A* 10:11.1 -04:43 Ir+ V 11.9 5.9 x 5.0 5200 *Sex dw* 10:13.2 -01:37 dSph/E3 12. 320 *Leo II* 11:13.5 +22:10 dSph/E0 pec 12.6 12.0 x 11.0 750 *GR 8* 12:58.7 +14:13 Im V 14.5 1.2 x 1.1 +165 7900: *UMi dw* 15:08.8 +67:12 dSph/E4 10.9 41.0 x 26.0 240 *Dra dw* 17:20.1 +57:55 dSph/E0 pec 9.9 51.0 x 31.0 280 *Milky Way * 17:45.6 -28:56 SAB(s)bc I-II ? - 0 28 *SagDEG * 18:55 -30:30 dSph/E7 +168 88 *SagDIG* 19:30.1 -17:42 IB(s)m V 15.5 2.9 x 2.1 4200 *NGC 6822 <../xtra/ngc/n6822.html>* 19:44.9 -14:49 IB(s)m IV-V 9.3 15.5 x 13.5 + 66 1800 *Aqr dw* 20:46.8 -12:51 Im V 13.9 2.3 x 1.2 3400 *Tuc dw* 22:41.7 -64:25 dSph/E5 15.7 2.9 x 1.2 3200 *UKS2323-326* 23:26.5 -32:23 Irr 13.9 1.5 x 1.2 4700 *And VII* 23:27.8 +50:35 dSph 2.5 x 2.0 2600 *Peg dw* 23:28.6 +14:45 Im V 13.2 5.0 x 2.7 3000: *And VI* 23:51.7 +24:36 dSph 11.2 3.5 x 3.5 2800 Possible further members: *UGCA 86* 03:59.9 +67:08 Irr ? S0 ? 13.5 0.8 x 0.7 +262 6200 *Willman 1* 10:49.4 +51:03 dSph? GC ? 15.3 1.75 147 *IC 5152 <../xtra/ngc/i5152.html>* 22:06.1 -51:17 IAB(s)m IV 10.6 4.9 x 3.0 + 30 5800 Below we list some nearby but probably non-member field galaxies (which are also not members of one of the neighboring groups listed above), in the same format as above: *Nearby Non-Member (?) Galaxies* *Galaxy RA Dec Type m_v dim RV Dist* ------------------------------------------------------------------------ *NGC 55* 00:14.9 -39:11 Sc/SB(s)m 8.8 32.4 x 5.6 +129 7000 *NGC 404* 01:09.4 +35:43 E0 10.1 4.4 x 4.1 +178 8000: *Cam A* 04:25.3 +72:48 Irr 14.8 3.7 x 2.1 6500:: *NGC 1569* 04:30.8 +64:51 Irp+ III-IV: 11.2v 2.9 x 1.5 + 87 7500:: *NGC 1560* 04:32.8 +71:53 Sd 11.5v 9.8 x 2.0 +151 7500:: *Argo dw* 07:05.3 -58:31 Irr 14.2 3.5 x 1.7 +554 12000: *UGC 9128* 14:15.9 +23:03 Irp+ 14.4 1.7 x 1.3 +154 *Key:* RA, Dec: Right Ascension and Declination for epoch 2000.0 Type: Classification type from Tom Polakis' article, or elsewhere m_v Apparent visual brightness in Magnitudes. A "p" indicates that only photographic magnitudes are available and given. dim Angular dimension in arc minutes RV: Radial velocity wrt galactic center in km/sec Dist: Distance in 1000 light years (kly) A colon following a number indicates this value is uncertain. *More data of and remarks on Local Group Galaxies* *Galaxy R SG Diam Mass Other names/Remarks* ------------------------------------------------------------------------ *WLM* (*) LGC 8 ? UGCA 444, DDO 221 *IC 10* LGC UGC 192 *Cet dw* LGC *NGC 147* M31 UGC 326, DDO 3 *And III* M31 PGC 2121 *NGC 185* M31 UGC 396 *M 110* M31 17 10000 NGC 205 *And VIII* M31 33 *M 32* M31 8 3000 NGC 221 *M 31* M31 195 400000 NGC 224 *And I* M31 PGC 2666 *SMC* MW 25 6000 NGC 292, Nubecula Minor *Scl dw* MW ESO 351- G 030, PCG 3589 *LGS 3* (*) M31/33 Psc dw, PCG 3792 *IC 1613* M31/LC UGC 668, DDO 8 *And V* M31 *And II* M31 PGC 4601 *M 33* M31/33 60 25000 NGC 598 *Phe dw* (I) MW/LGC ESO 245- G 007, PGC 6830 *For dw* MW ESO 356- G 004, PGC 10093 *UGCA 92* (I) M31? EGB 0427+63, PGC 15439 *LMC* MW 30 20000 ESO 056- G 115, PGC 17223, Nubecula Major *Car dw* MW ESO 206- G 220, ESO 206- GA020, PGC 19441 *CMa dw* MW *Leo A* M/3109 Leo III, UGC 5364, DDO 69 *Sex B* (I) N3109 UGC 5373, DDO 70 *NGC 3109* (I) N3109 UGCA 194, DDO 236 *Ant dw* (I) N3109 5 PGC 29194 *Leo I* MW UGC 5470, DDO 74, Harrington-Wilson 1, Regulus Galaxy *Sex A* N3109 UGCA 205, DDO 75 *Sex dw* MW *Leo II* MW Leo B, UGC 6253, DDO 93, Harrington-Wilson 2 *GR 8* (?) GR8 UGC 8091, DDO 155, VV 558 *UMi dw* MW UGC 9749, DDO 199 *Dra dw* MW UGC 10822, DDO 208 *Milky Way* MW 100 750000 *SagDEG* (*) MW Sgr dShp, Sgr I dw *SagDIG* (*) LGC Sgr dw, ESO 594- G 004, UKS 1927-177, PGC 63287, Kowal's Object *NGC 6822* LGC IC 4895, DDO 209, Barnard's Galaxy *Aqr dw* LGC DDO 210, PGC 65367 *Tuc dw* LGC PCG 69519 *UKS2323-326* LGC UGCA 438 *And VII* M31 Cas dSph, Cas dw *Peg dw* LGC UGC 12613, DDO 216, Peg DIG *And VI* M31 Peg dSph, Peg II Possible members: *UGCA 86* (?) M31/L? PGC 14241 *Willman 1* MW SDSSJ1049+5103 *IC 5152* (?) LGC? ESO 237- G 027 *Key:* R: Remarks: (*), (?) and (I); see below SG: Subgroup (after Mateo 1999). MW=Milky Way subgroup, M31: M31 subgroup, M31/33: M33 subgroup (probably part of M31 subgroup), LGC: Local Group Cloud (vast cloud of dwarf irregulars), N3109: NGC 3109 subgroup (not counted to Local Group by Van den Bergh), GR8: GR8 group (LG membership in doubt), M/N3109: Either MW or NGC 3109 group Diam: Diameter in 1000 light years (kly) Mass: Mass in million solar masses Remarks (*): * "WLM" is "Wolf-Lundmark-Melotte" * "LGS " stands for "Local Group (suspected)" (LGS 3) * "SagDEG" is the "Sagittarius Dwarf Elliptical Galaxy" (discovered 1994, containing M54 <../m/m054.html>) * "SagDIG" is the "Sagittarius Dwarf Irregular Galaxy" Galaxies marked with "(?)" may be non-members as they are not in the list of Irwin et.al. 1997 (this list has 35 Local Group members), in particular: * UGCA 86 may be a member of the Maffei 1 group <../xtra/ngc/maffei1g.html> * GR8 and IC 5152 are listed as nearby non-member galaxies in Irwin's list. They may be lonely nearby non-members near the edges of the group. * The Aquarius Dwarf is also listed by Irwin as non-member, but Van den Bergh (2000) reports its membership has now be confirmed. * Leo A was also listed in Irwin's list of non-members, but recent distant re-determination confirmed its membership. Galaxies marked with "(I)" are newly taken into the list from Irwin's list: Besides the newly discovered Antlia dwarf, these are the Phoenix dwarf, UGCA 92, Sextans B, and NGC 3109. More Data on the Probable Nearby Non-Members listed above: *Galaxy Other names/Remarks* ------------------------------------------------------------------------ *NGC 55* ESO 293- G 050 *NGC 404* UGC 718 *Cam A* *NGC 1569* UGC 3056 *NGC 1560* UGC 3060 *Argo dw* PGC 20125 *UGC 9128* DDO 187 Various sources have listed other, former Local Group candidates which however have not been confirmed: *"Galaxy" listed Rem* ------------------------------------------------------------------------ *1010-27* McGraw = Ant dw ? *DDO 187* (UGC 9128) McGraw Nearby probable non-member galaxy, see above *SDIG* KKT Member of the Sculptor Group of Galaxies *LGS 2* Irwin diffuse reflection nebulosity *And IV* vdB Background galaxy, or open cluster in M31 *Sex C* (A 1003) LGAA globular cluster Palomar 3 *UMa dw* (A 1127) dV,LGAA globular cluster Palomar 4 *Ser dw* (A 1513) dV globular cluster Palomar 5 *Cap dw* (A 2144) McGraw globular cluster Palomar 12 *Snickers* Radio observations of 1975 indicated this nearby galaxy candidate *NGC 6946 <../xtra/ngc/n6946.html>* Hubble Nearby non-member galaxy *IC 342* Hubble Member of the Maffei 1 or IC 342 Group of Galaxies *Maffei 1* Maffei Member of the Maffei 1 or IC 342 Group of Galaxies *Maffei 2* Maffei Member of the Maffei 1 or IC 342 Group of Galaxies *2318-42* Irwin Sources: dV: G. De Vaucouleurs 1975, Nearby Groups of Galaxies, ch. 4, The Local Group. Published in "Galaxies and the Universe," ed. by A. Sandage, M. Sandage and J. Kristian. Hubble E.P. Hubble 1936, The Realm of the Nebulae, Yale University Press. Local group table on p. 126. KKT: Kraan-Korteweg & Tammann, 1979. /Astronomische Nachrichten/ *300*, p. 181 LGAA: Le Grand Atlas de L'Astronomie, Encyclopedia Universalis, 1986. German edition: "Der große JRO Atlas der Astronomie" McGraw: McGraw-Hill Dictionary of Astronomy, by Sybil P. Parker (ed), p. 242 Maffei: P. Maffei 1968, /PASP/ *80*, p. 618 vdB: S. van den Bergh 1972, Search for Faint Companions to M31. /ApJ./ *171*, p. L31-L33. Andromeda IV is probably not an independent Local Group galaxy, but either a large open cluster in M31 (Jones, 1993 <#jones1993>), or a more remote background galaxy (Ferguson /et.al./, 2000 <#ferguson2000>) As our Milky Way obscures parts of the sky, there is still a steady flow of new discoveries of galaxies, in low galactic latitudes (i.e., near the equatorial plane of our galaxy, where the obscuring dust is most dense). Also, some of the galaxies are of extreme low surface brightness, and it was only recently possible to detect them. Therefore, it must be expected that more Local Group members exist, obscurred by dust, or extremely faint, and are still waiting for their detection somewhen in the future. Jeff Bondono has compiled a comprehensive list <../xtra/data/jb-lg.txt> of Local Group member and member candidate galaxies. Links You are invited to contribute more links which are of interest for this page; please contact the maintainer <../Contact/contact.html>. * Local Group Galaxies , images and more information on all known certain and possible member galaxies as well as all former candidates, at SEDS * Bill Arnett's table of Local Group galaxies * (Lengthy) article on the Local Group by George Lake * Mike Irwin's Local Group page and Local Group Member list * Brian Skiff's list of Local Group galaxies (based on Sidney van den Bergh's article in PASP May 2000 issue) * Local Group Galaxies table from NED (from Mateo 1998 <#mateo1998>) * Local Group Survey , by Phil Massey Based on High Resolution Images from the KPNO and CTIO 4-m telescopes. * Milky Way Satellite and Local Group pages (from An Atlas of the Universe, by Richard Powell) * Local Group galaxy images from the Astronomical Picture of the Day archives * Observing the Local Group by Tom Polakis; from Deep Sky Magazine #36. * The Local Group of Galaxies map and list , and The Milky Way's Satellite Galaxies , from An Atlas of the Universe * Distribution of Galaxies in the Local Group , an animated graphical 3D presentation by Wil Milan References * Annette M.N. Ferguson, J.S. Gallagher, and Rosemary F.G. Wyse, 2000. On the Nature of Andromeda IV. Astronomical Journal, Vol. 120, No. 2, p. 821-832 (08/2000) * Joseph H. Jones, 1993. CCD photometry of Andromeda IV - Dwarf irregular galaxy or M31 open cluster? Astronomical Journal, vol. 105, no. 3, p. 933-7 (03/1993) * Mario Mateo, 1998. Dwarf Galaxies of the Local Group. Annual Review of Astronomy and Astrophysics, Volume 36, 1998, p. 435-506 . Available online [framed version ] - table of Local Group galaxies (NED Level 5) * Sidney van den Bergh, 1972. Search for Faint Companions to M31. /Astrophysical Journal/, vol. 171, p. L31-L33 * Sidney van den Bergh, 1994. The Outer Fringes of the Local Group. Astronomical Journal 107, No. 4, p. 1328-1332 (April 1994) * Sidney van den Bergh, 2000. Updated Information on the Local Group. Publications of the Astronomical Society of the Pacific, Vol. 112, No. 770, p. 529-536 (April 2000) * *Tom Polakis* has published an interesting article for observers of local group galaxies, /Observing the Local Group/, in the /Deep Sky/ magazine (#36), which was reprinted in *David Eicher*'s book /Galaxies and the Universe/ <../m-ref.html#eicher92>. (was also available online but disappeared) * *Paul W. Hodge*, /Galaxies/. Harvard University Press, 1986. In particular Chapter 7: The Local Group. * *Edwin P. Hubble*, /The Realm of the Nebulae/, Yale University Press, 1936 (in particular, pp. 124, 145) ------------------------------------------------------------------------ This page has been used in the sci.astro FAQ ------------------------------------------------------------------------ Hartmut Frommert Christine Kronberg [contact] <../Contact/contact.html> [SEDS] [MAA] [Home] <../Messier.html> [Galaxy Groups] <../g-group.html> [Indexes] <../indexes.html> Last Modification: February 13, 2005