Messier 94 969038 224567090 2008-07-09T13:19:03Z Sumanch 222446 {{otheruses2|M94}} {{Galaxybox begin | name = [[Messier object|Messier]] 94<ref name="tonryetal2001">{{cite journal | author=J. L. Tonry, A. Dressler, J. P. Blakeslee, E. A. Ajhar, A. B. Fletcher, G. A. Luppino, M. R. Metzger, C. B. Moore | title=The SBF Survey of Galaxy Distances. IV. SBF Magnitudes, Colors, and Distances | journal=Astrophysical Journal | year=2001 | volume=546 | issue=2 | pages=681–693 | url=http://adsabs.harvard.edu/abs/2001ApJ...546..681T | doi=10.1086/318301 }}</ref><ref name="karachentsevetal2003">{{cite journal | author=I. D. Karachentsev, M. E. Sharina, A. E. Dolphin, E. K. Grebel, D. Geisler, P. Guhathakurta, P. W. Hodge, V. E. Karachentseva, A. Sarajedini, P. Seitzer | title=Galaxy flow in the Canes Venatici I cloud | journal=Astronomy and Astrophysics | year=2003 | volume=398 | pages=467–477 | url=http://adsabs.harvard.edu/abs/2003A&A...398..467K | doi=10.1051/0004-6361:20021598 }}</ref><ref name="averageCalc">average(17.0 ± 1.4, 15 ± 2) = ((17.0 + 15) / 2) ± ((1.4<sup>2</sup> + 2<sup>2</sup>)<sup>0.5</sup> / 2) = 16.0 ± 1.3</ref> }} {{Galaxybox image | image = [[Image:Spiral Galaxy M94.jpg|300px]] | caption = [[Nordic Optical Telescope]] image of M94. }} {{Galaxybox observe | epoch = [[J2000]] | constell = [[Canes Venatici (constellation)|Canes Venatici]]<ref name="sinnott1988">{{cite book | author=R. W. Sinnott, editor | title= The Complete New General Catalogue and Index Catalogue of Nebulae and Star Clusters by J. L. E. Dreyer | year=1988 | publisher=Sky Publishing Corporation and Cambridge University Press | id=ISBN 0-933-34651-4}}</ref> | ra = {{RA|12|50|53.1}} <ref name="ned">{{cite web | title=NASA/IPAC Extragalactic Database | work=Results for M94 | url=http://nedwww.ipac.caltech.edu/ | accessdate=2006-11-09}}</ref> | dec = {{DEC|+41|07|14}} <ref name="ned" /> | appdim_v = 11.2 × 9.1 [[Minute of arc|moa]] <ref name="ned" /> | appmag_v = 8.99 <ref name="ned" /> }} {{Galaxybox character | g_type = (R)SA(r)ab<ref name="ned" />, [[LINER]]<ref name="ned" /> }} {{Galaxybox astrometry | h_radial_v = 308 | hrv_err = 1 <ref name="ned" /> | z = 0.001027 | z_err = 0.000005 <ref name="ned" /> | gal_v = 360 | gv_err = 3 <ref name="ned" /> | g_dist = 16.0 | dist_err = 1.3 }} {{Galaxybox catalog | names = [[New General Catalogue|NGC]] 4736, [[Uppsala General Catalogue|UGC]] 7996, [[Principal Galaxies Catalogue|PGC]] 43495<ref name="ned" /> }} {{Galaxybox end}} '''Messier 94''' (also known as ''NGC 4736'') is a [[spiral galaxy]] in the [[constellation]] [[Canes Venatici]]. It was discovered by [[Pierre Méchain]] in [[1781]],<ref name="NSOG">{{cite book |last= Kepple |first= George Robert |coauthors= Glen W. Sanner |title= The Night Sky Observer's Guide, Volume 2 |publisher= Willmann-Bell, Inc. |year= 1998 |id= ISBN 0-943396-60-3 |pages=51 }}</ref> and catalogued by [[Charles Messier]] two days later. Although some references describe M94 as a [[barred spiral galaxy]], the "bar" structure appears to be more oval-shaped.<ref name="kormendykennicutt04">{{cite journal | author=J. Kormendy, R. C. Kennicutt, Jr. | title=Secular Evolution and the Formation of Pseudobulges in Disk Galaxies | journal=Annual Reviews of Astronomy and Astrophysics | year=2004 | volume=42 | pages=603–683 | url=http://adsabs.harvard.edu/abs/2004ARA&A..42..603K | doi=10.1146/annurev.astro.42.053102.134024 }}</ref> The galaxy is also notable in that it has two ring structures.<ref name="ned" /> ==Nucleus== M94 is classified as having a [[low ionization nuclear emission region]] (LINER) nucleus.<ref name="hoetal1997">{{cite journal | author= L. C. Ho, A. V. Filippenko, W. L. W. Sargent | title=A Search for "Dwarf" Seyfert Nuclei. III. Spectroscopic Parameters and Properties of the Host Galaxies | journal=Astrophysical Journal Supplement | year=1997 | volume=112 | pages=315–390 | url=http://adsabs.harvard.edu/abs/1997ApJS..112..315H | doi= 10.1086/313041 }}</ref> LINERs in general are characterized by optical [[spectrum|spectra]] that reveal that [[ion]]ized gas is present but the gas is only weakly ionized (i.e. the atoms are missing relatively few electrons). ==Inner and outer rings== M94 contains both an inner ring with a diameter of 70" and an outer ring with a diameter of 600". These rings appear to form at [[resonance]] locations within the disk of the galaxy. The inner ring is the site of strong [[star formation]] activity and is sometimes referred to as a [[starburst (astronomy)|starburst]] ring. This star formation is fueled by gas that is dynamically driven into the ring by the inner oval-shaped bar-like structure.<ref name="munoztunonetal04">{{cite journal | author=C. Muñoz-Tuñón, N. Caon, J. Aguerri, L. Alfonso | title=The Inner Ring of NGC 4736: Star Formation on a Resonant Pattern | journal=Astronomical Journal | year=2004 | volume=127 | pages=58–74 | url=http://adsabs.harvard.edu/abs/2004AJ....127...58M | doi=10.1086/380610}}</ref> ==Pseudobulge== In a paper published in 2004, [[John Kormendy]] and [[Robert Kennicutt]] argued that M94 contains a prototypical [[bulge (astronomy)|pseudobulge]].<ref name="kormendykennicutt04" /> A classical [[spiral galaxy]] consists of a disk of gas and young stars that intersects a large sphere (or bulge) of older stars. In contrast, a galaxy with a pseudobulge does not have a large bulge of old stars but instead contain a bright central structure with intense star formation that looks like a bulge when the galaxy is viewed face-on. In the case of M94, this pseudobulge takes the form of a ring around a central oval-shaped region. ==Distance measurements== At least two techniques have been used to measure distances to M94. The [[surface brightness fluctuation]]s distance measurement technique estimates distances to spiral galaxies based on the graininess of the appearance of their bulges. The distance measured to M94 using this technique is 17.0 ± 1.4 [[light-year|Mly]] (5.2 ± 0.4 [[parsec|Mpc]]).<ref name="tonryetal2001" /> However, M94 is close enough that the [[Hubble Space Telescope]] can be used to resolve and measure the fluxes of the brightest individual stars within the galaxy. These measured fluxes can then be compared to the measured fluxes of similar stars within the [[Milky Way]] to measure the distance. The estimated distance to M94 using this technique is 15 ± 2 [[light-year|Mly]] (4.7 ± 0.6 [[parsec|Mpc]]).<ref name="karachentsevetal2003" /> Averaged together, these distance measurements give a distance estimate of 16.0 ± 1.3 [[light-year|Mly]] (4.9 ± 0.4 [[parsec|Mpc]]). ==Dark matter== In 2008 a study was published that appeared to show that M94 had very little or no [[dark matter]] present. The study analyzed the rotation curves of the galaxy's stars and the density of hydrogen gas and found that ordinary luminous matter appeared to account for all of the galaxy's mass. This result was unusual and somewhat controversial, as current models don't indicate how a galaxy could form without a dark matter halo or how a galaxy could lose its dark matter. Other explanations for galactic rotation curves, such as [[MOND]], also have difficulty explaining this galaxy.<ref>{{cite news| url=http://space.newscientist.com/article/dn13280-galaxy-without-dark-matter-puzzles-astronomers.html| title=Galaxy without dark matter puzzles astronomers| date= 06 February 2008| publisher= NewScientist.com news service| first= Stephen | last=Battersby}}</ref> ==Galaxy group information== M94 is one of the brightest galaxies within the [[M94 Group]], a [[group of galaxies]] that contains between 16 and 24 galaxies.<ref name="nbg">{{cite book | author=R. B. Tully | year=1988 | title=Nearby Galaxies Catalog | edition= | publisher=Cambridge University Press | location=Cambridge | id=ISBN 0-521-35299-1}}</ref><ref name="garcia1993">{{cite journal | author=A. Garcia | title=General study of group membership. II - Determination of nearby groups | journal=Astronomy and Astrophysics Supplement | year=1993 | volume=100 | pages=47–90 | url=http://adsabs.harvard.edu/abs/1993A&AS..100...47G}}</ref><ref name="giuricinetal2002">{{cite journal | author=G. Giuricin, C. Marinoni, L. Ceriani, A. Pisani | title=Nearby Optical Galaxies: Selection of the Sample and Identification of Groups | journal=Astrophysical Journal | year=2000 | volume=543 | pages=178–194 | url=http://adsabs.harvard.edu/abs/2000ApJ...543..178G | doi=10.1086/317070 }}</ref> This group is one of many that lies 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 | year=1982 | volume=257 | pages=389–422 | url=http://adsabs.harvard.edu/abs/1982ApJ...257..389T | doi= 10.1086/159999 }}</ref> Although a large number of galaxies may be associated with M94, only a few galaxies near M94 appear to form a gravitationally bound system. Most of the other nearby galaxies appear to be moving with the expansion of the universe.<ref name="karachentsevetal2003" /><ref name="karachentsev2005">{{cite journal | author=I. D. Karachentsev | title=The Local Group and Other Neighboring Galaxy Groups | journal=Astronomical Journal | year=2005 | volume=129 | pages=178–188 | url=http://adsabs.harvard.edu/abs/2005AJ....129..178K | doi=10.1086/426368 }}</ref> == See also == * [[NGC 1512]] - ''a galaxy with a similar inner ring'' == External links == * [http://ryutao.main.jp/english/st2k_m94.html Galaxy Messier 94 at the astro-photography site of Mr. T. Yoshida.] * [http://www.seds.org/messier/m/m094.html SEDS: Spiral Galaxy M94] * {{WikiSky}} ==References== {{reflist}} [[Category:Spiral galaxies|Messier 094]] [[Category:Barred spiral galaxies|Messier 094]] [[Category:LINER galaxies|Messier 094]] [[Category:M94 Group|Messier 094]] [[Category:Canes Venatici constellation|Messier 094]] [[Category:Messier objects|094]] [[Category:NGC objects|Messier 094]] [[Category:UGC objects|07996]] [[Category:PGC objects|43495]] [[bg:M94]] [[ca:Messier 94]] [[cs:Messier 94]] [[co:M94]] [[de:Messier 94]] [[es:Galaxia espiral M94]] [[eo:M94]] [[fr:M94]] [[hr:Messier 94]] [[it:M94 (astronomia)]] [[lb:Messier 94]] [[lt:Mesjė 94]] [[hu:Messier 94]] [[nl:Messier 94]] [[ja:M94]] [[pl:Messier 94]] [[pt:NGC 4736]] [[ro:Messier 94]] [[ru:Спиральная галактика M94]] [[sk:Galaxia M94]] [[fi:Messier 94]] [[uk:NGC 4736]] [[zh:M94 (螺旋星系)]]