View source for M81 Group

{{short description|Galaxy group in Ursa Major and Camelopardalis}}
{{Galaxy cluster
| name = M81 Group
| image = [[Image:Messier 81 HST.jpg|300px]]
| epoch=[[J2000]]
| ra=
| dec=
| constellation = [[Ursa Major]]/[[Camelopardalis]]
| member_no = 34<ref name="karachentsev2005" />
| brightest_member = [[Messier 81|M81]]<ref name="karachentsev2005" /> (pictured)
| other_names = [[New General Catalogue|NGC]] 3031 Group
}}

The '''M81 Group''' is a [[galaxy group]] in the [[constellation]]s [[Ursa Major]] and [[Camelopardalis]] that includes the  galaxies [[Messier 81]] and [[Messier 82]], as well as several other galaxies with high apparent brightnesses.<ref name="karachentsev2005">{{cite journal
  | author=I. D. Karachentsev
  | title=The Local Group and Other Neighboring Galaxy Groups
  | journal=Astronomical Journal
  | date=2005
  | volume=129
  | issue=1
  | pages=178–188
  | bibcode=2005AJ....129..178K | doi = 10.1086/426368
|arxiv = astro-ph/0410065 | s2cid=119385141
 }}</ref>  The approximate center of the group is located at a distance of 3.6 [[Parsec|Mpc]], making it one of the nearest groups to the [[Local Group]].<ref name="karachentsev2005" />  The group is estimated to have a total mass of (1.03 ± 0.17){{e|12}}{{Solar mass|link=y}}.<ref name="Karachentsevetal2006">{{cite journal
  | author=Karachentsev, I. D.
  | author2=Kashibadze, O. G.
  | title=Masses of the local group and of the M81 group estimated from distortions in the local velocity field
  | journal=Astrophysics
  | date=2006
  | volume=49
  | issue=1
  | pages=3–18
  | bibcode=2006Ap.....49....3K  | doi = 10.1007/s10511-006-0002-6
| s2cid=120973010
 }}</ref>
The M81 Group, the Local Group, and other nearby groups all lie within the [[Virgo Supercluster]] (i.e. the Local Supercluster).<ref name="tully1982">{{cite journal
  | author= R. B. Tully
  | title=The Local Supercluster
  | journal=Astrophysical Journal
  | date=1982
  | volume=257
  | pages=389–422
  | bibcode=1982ApJ...257..389T | doi = 10.1086/159999
| doi-access=free
  }}</ref>

==Members==
{{more references needed|section|date=December 2024}}
The table below lists galaxies that have been identified as associated with the M81 Group by I. D. Karachentsev.<ref name="karachentsev2005" />
{{clear}}
{| class="wikitable sortable" style="text-align:center;border-collapse:collapse;" cellpadding="2"
|+'''Members of the M81 Group'''
|-
! style="background:#efefef;" | Name
! style="background:#efefef;" | [[Galaxy morphological classification|Type]]<ref name="ned">{{cite web
  | title=NASA/IPAC Extragalactic Database
  | work=Results for various galaxies
  | url=http://nedwww.ipac.caltech.edu/
  | access-date=2007-02-09
  | archive-date=2000-10-19
  | archive-url=https://web.archive.org/web/20001019032134/http://nedwww.ipac.caltech.edu/
  | url-status=bot: unknown
  }}</ref>
! style="background:#efefef;" | [[Right Ascension|R.A.]] ([[J2000]])<ref name="ned" />
! style="background:#efefef;" | [[Declination|Dec.]] ([[J2000]])<ref name="ned" />
! style="background:#efefef;" | [[Redshift]] ([[kilometer|km]]/[[second|s]])<ref name="ned" />
! style="background:#efefef;" | [[Apparent Magnitude]]<ref name="ned" />
|-
| [[Arp's Loop]]{{cn|date=December 2024}}<!--Simbad needed-->
|
| {{RA|09|57|32.6}}
| {{DEC|+69|17|00}}
| 99
| 16.1
|-
| [[DDO 78]]{{cn|date=December 2024}}<!--Simbad needed-->
| Im
| {{RA|10|26|27.4}}
| {{DEC|+67|39|16}}
| 55 ± 10
| 15.8
|-
| [[F8D1]]{{cn|date=December 2024}}<!--Simbad needed-->
| dE
| {{RA|09|44|47.1}}
| {{DEC|+67|26|19}}
|
| 13.9
|-
| [[FM1 (galaxy)|FM1]]{{cn|date=December 2024}}<!--Simbad needed-->
| dSph
| {{RA|09|45|10.0}}
| {{DEC|+68|45|54}}
|
| 17.5
|-
| [[HIJASS J1021+6842]]{{cn|date=December 2024}}<!--Simbad needed-->
|
| {{RA|10|21|00.0}}
| {{DEC|+68|42|00}}
| 46
| 20
|-
| [[HS 117]]{{cn|date=December 2024}}<!--Simbad needed-->
| I
| {{RA|10|21|25.2}}
| {{DEC|+71|06|51}}
| −37
| 16.5
|-
| [[Holmberg I]]{{cn|date=December 2024}}<!--Simbad needed-->
| IAB(s)m
| {{RA|09|40|32.3}}
| {{DEC|+71|10|56}}
| 139 ± 0
| 13.0
|-
| [[Holmberg II]]
| Im
| {{RA|08|19|05.0}}
| {{DEC|+70|43|12}}
| 142 ± 1
| 11.1
|-
| [[Holmberg IX]]
| Im
| {{RA|09|57|32.0}}
| {{DEC|+69|02|45}}
| 46 ± 6
| 14.3
|-
| [[IC 2574]]
| SAB(s)m
| {{RA|10|28|23.5}}
| {{DEC|+68|24|44}}
| 57 ± 2
| 13.2
|-
| [[IKN]]
|
| {{RA|10|08|05.9}}
| {{DEC|+68|23|57}}
|
| 17.0
|-
| [[KKH 57]]
| dSph
| {{RA|10|00|16.0}}
| {{DEC|+63|11|06}}
|
| 18.5
|-
| [[Messier 81]]
| SA(s)ab
| {{RA|09|55|33.2}}
| {{DEC|+69|03|55}}
| −34 ± 4
| 6.9
|-
| [[Messier 81 Dwarf A]]
| I
| {{RA|08|23|56.0}}
| {{DEC|+71|01|45}}
| 113 ± 0
| 16.5
|-
| [[Messier 82]]
| I0
| {{RA|09|55|52}}
| {{DEC|+69|40|47}}
| 203 ± 4
| 9.3
|-
| [[NGC 2366]]
| IB(s)m
| {{RA|07|28|54.7}}
| {{DEC|+69|12|57}}
| 80 ± 1
| 11.4
|-
| [[NGC 2403]]
| SAB(s)cd
| {{RA|07|36|51.4}}
| {{DEC|+65|36|09}}
| 131 ± 3
| 8.9
|-
| [[NGC 2976]]
| SAc pec
| {{RA|09|47|15.5}}
| {{DEC|+67|54|59}}
| 3 ± 5
| 10.8
|-
| [[NGC 3077]]
| I0 pec
| {{RA|10|03|19.1}}
| {{DEC|+68|44|02}}
| 14 ± 4
| 10.6
|-
| [[NGC 4236]]
| SB(s)dm
| {{RA|12|16|42}}
| {{DEC|+69|27|45}}
| 0 ± 4
| 10.1
|-
| [[PGC 28529]]
| Im
| {{RA|09|53|48.5}}
| {{DEC|+68|58|08}}
| −40
| 17.1
|-
| [[PGC 28731]]
| dE
| {{RA|09|57|03.1}}
| {{DEC|+68|35|31}}
| −135 ± 30
| 15.6
|-
| [[PGC 29231]]
| dE
| {{RA|10|04|41.1}}
| {{DEC|+68|15|22}}
|
| 16.7
|-
| [[PGC 31286]]
| dSph
| {{RA|10|34|29.8}}
| {{DEC|+66|00|30}}
|
| 16.7
|-
| [[PGC 32667]]
| Im
| {{RA|10|52|57.1}}
| {{DEC|+69|32|58}}
| 116 ± 1
| 14.9
|-
| [[UGC 4459]]
| Im
| {{RA|08|34|07.2}}
| {{DEC|+66|10|54}}
| 20 ± 0
| 14.5
|-
| [[UGC 4483]]
|
| {{RA|08|37|03.0}}
| {{DEC|+69|46|31}}
| 156 ± 0
| 15.1
|-
| [[UGC 5428]]
| Im
| {{RA|10|05|06.4}}
| {{DEC|+66|33|32}}
| −129 ± 0
| 18
|-
| [[UGC 5442]]
| Im
| {{RA|10|07|01.9}}
| {{DEC|+67|49|39}}
| −18 ± 14
| 18
|-
| [[UGC 5692]]
| Sm
| {{RA|10|30|35.0}}
| {{DEC|+70|37|07.2}}
| 56 ± 3
| 13.5
|-
| [[UGC 6456]]
| Pec
| {{RA|11|27|59.9}}
| {{DEC|+78|59|39}}
| −103 ± 0
| 14.5
|-
| [[UGC 7242]]
| Scd
| {{RA|12|14|08.4}}
| {{DEC|+66|05|41}}
| 68 ± 2
| 14.6
|-
| [[UGC 8201]]
| Im
| {{RA|13|06|24.9}}
| {{DEC|+67|42|25}}
| 31 ± 0
| 12.8
|-
| [[UGCA 133]]
| dSph
| {{RA|07|34|11.4}}
| {{DEC|+66|53|10}}
|
| 15.6
|-
|}

Note that the object names used in the above table differ from the names used by Karachentsev.  [[New General Catalogue|NGC]], [[Index Catalogue|IC]], [[Uppsala General Catalogue|UGC]], and [[Principal Galaxies Catalogue|PGC]] numbers have been used in many cases to allow for easier referencing.

==Interactions within the group==

Messier 81, Messier 82, and NGC 3077 are all strongly [[interacting galaxy|interacting]] with each other.<ref name="yunetal1994">{{cite journal
  | author=M. S. Yun
  | author2=P. T. P. Ho
  | author3=K. Y. Lo
  | title=A high-resolution image of atomic hydrogen in the M81 group of galaxies
  | journal=Nature
  | date=1994
  | volume=372
  | pages=530–532
  | bibcode=1994Natur.372..530Y | doi = 10.1038/372530a0
  | pmid=7990925
  | issue=6506
| s2cid=4369085
 }}</ref>  Observations of the 21-centimeter [[hydrogen line]] indicate how the galaxies are connected.<ref name="chynowethetal2008">{{cite journal 
|last1=Chynoweth 
|first1=Katie M. 
 |display-authors=etal 
|title=Neutral Hydrogen Clouds in the M81/M82 Group 
|journal=The Astronomical Journal 
|date=2008 
|volume=135 
|issue=2008 June 
|pages=1983–1992 
|doi=10.1088/0004-6256/135/6/1983|arxiv=0803.3631 
|bibcode=2008AJ....135.1983C 
 |s2cid=4490764 
 }}</ref> 
The gravitational interactions have stripped some [[hydrogen]] gas away from all three galaxies, leading to the formation of filamentary gas structures within the group.<ref name="yunetal1994" />  Bridges of neutral hydrogen have been shown to connect M81 with M82 and NGC 3077.<ref name="chynowethetal2008" /><ref name="hulst1978">{{cite journal |last1=Hulst 
|first1=J. M. van der 
|title=The Structure and Kinematics of the Neutral Hydrogen Bridge Between M 81 and NGC 3077 
|journal=Astronomy and Astrophysics 
|date=1978 
|volume=75 
|issue=1–2 
|pages=97–111}}</ref> Moreover, the interactions have also caused some [[interstellar medium|interstellar gas]] to fall into the centers of Messier 82 and NGC 3077, which has led to strong [[starburst galaxy|starburst activity]] (or the formation of many stars) within the centers of these two galaxies.<ref name="yunetal1994" /> Computer simulations of [[tidal forces|tidal interactions]] have been used to show how the current structure of the group could have been created.<ref name="yun1999">{{cite book 
|last1=Yun |first1=M. S. 
|chapter=Tidal Interactions in M81 Group 
|title=Galaxy Interactions at Low and High Redshift 
|date=1999 
|volume=186 
|page=81 
|doi=10.1007/978-94-011-4665-4_18 
|bibcode=1999IAUS..186...81Y 
|isbn=978-0-7923-5833-6 
|ref=1999IAUS..186...81Y}}</ref>

==Gallery==
<gallery>
The mysteries of UGC 8201.jpg|Galaxy [[UGC 8201]] is a dwarf irregular galaxy member of the M81 galaxy group.<ref>{{cite web|title=The mysteries of UGC 8201|url=http://www.spacetelescope.org/images/potw1510a/|access-date=18 June 2015}}</ref>
M81+M82-and other galaxies.jpg|Amateur picture [[Messier 81]] + [[Messier 82|82]] and [[NGC 3077]] all of the M81 group, 33 frames stacked of 1 minute each.
Image:M81m82 galex f.jpg|The spiral galaxies Messier 81 and 82 and the dwarf galaxy Holmberg IX from GALEX
Image:M81 wide Galex.jpg|Close up view of Messier 81 from GALEX
Image:Messier81 highres.jpg|The spiral galaxy Messier 81 from Spitzer Space Telescope
Image:Ssc2003-06c.jpg|The spiral galaxy Messier 81 from Spitzer Space Telescope
Image:M82 HST ACS 2006-14-a-large web.jpg|Starburst galaxy Messier 82 from Hubble Space Telescope
Image:NGC2403 3.6 5.8 8.0 microns spitzer.png|NGC 2403 in mid-infrared view, combining the 3.6, 5.8 and 8.0 μm bands of the Spitzer Space Telescope
Image:NGC2403 3.6 8.0 24 microns spitzer.png|NGC 2403 in Mid-infrared view, combining the 3.6, 8.0 and 24 μm bands of the Spitzer Space Telescope
Image:NGC 2403HST.jpg|NGC 2403 from Hubble Space Telescope
Image:NGC 2403HSTSN.jpg|NGC 2403 from Hubble Space Telescope illustrated
Image:Galaxy-NGC-2403-with-SN2004DJ.jpeg|Supernova SN2004DJ in the spiral galaxy NGC 2403
Image:NGC2403-SN2004dj.jpg|Supernova 2004dj in NGC 2403
Image:NGC 4236 I FUV g2006.jpg|NGC 4236 from GALEX
Image:NGC 2366HST.jpg|NGC 2366 from Hubble Space Telescope
Image:NGC 2976SSTFull.jpg|Galaxy NGC 2976 from Spitzer Space Telescope in infrared
Image:NGC2976.jpg|Galaxy NGC 2976 from an amateur Astronomer
Image:NGC 4605 GALEX WikiSky.jpg|Galaxy NGC 4605 from GALEX
Image:Ngc2363HST.jpg|NGC 2363 from Hubble Space Telescope
Image:NGC 2537 I FUV g2006.jpeg| NGC 2537 from GALEX
Image:Holmberg IISST.jpg| Holmberg II from Spitzer Space Telescope in infrared
Image:M81DwarBSST.jpg|UGC 5423 / M81 dwarf B from Spitzer Space Telescope in infrared
Image:NGC 3077 2MASS.jpg|NGC 3077 from 2MASS
Image:IC 2574 Hubble WikiSky.jpg|IC 2574
</gallery>

==See also==
* [[UGC 5497]]

==References==
{{Reflist}}

==External links==
* [http://messier.seds.org/more/m081gr.html M81 Group @ SEDS]
* [http://www.atlasoftheuniverse.com/galgrps/m81.html M81 Group from An Atlas of The Universe]
{{Portal bar|Astronomy|Stars|Outer space}}

[[Category:M81 Group| ]]
[[Category:Virgo Supercluster]]
[[Category:Galaxy clusters]]