Messier 94

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**Messier 94**
Observation data (Epoch J2000)
Galaxy	List of galaxies
Messier 94
Constellation	Canes Venatici
Right ascension	12^h 50^m 53.1^s<ref name="ned" />
Declination	+41° 07′ 14″<ref name="ned" />
Redshift	308 ± 1 km/s<ref name="ned" />
Distance	17.0 ± 1.4 Mly (5.2 ± 0.4 Mpc)<ref name="tonryetal2001">J. L. Tonry, A. Dressler, J. P. Blakeslee, E. A. Ajhar, A. B. Fletcher, G. A. Luppino, M. R. Metzger, C. B. Moore (2001). "The SBF Survey of Galaxy Distances. IV. SBF Magnitudes, Colors, and Distances". Astrophysical Journal 546: 681-693.</ref>
Type	SA(r)ab<ref name="ned">NASA/IPAC Extragalactic Database. Results for NGC 4736. Retrieved on 2006-11-09.</ref>
Apparent dimensions (V)	11′.2 × 9′.1<ref name="ned" />
Apparent magnitude (V)	9.0<ref name="ned" />
Notable features
Other designations
NGC 4736, UGC 7996, PGC 43495<ref name="ned" />

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">Kepple, George Robert, Glen W. Sanner (1998). The Night Sky Observer's Guide, Volume 2. Willmann-Bell, Inc., 51. ISBN 0-943396-60-3.</ref> and catalogued by Charles Messier 2 days later. Although some references describe M94 as a barred spiral galaxy, the "bar" structure appears to be more oval-shaped<ref name="kormendykennicutt04">J. Kormendy, R. C. Kennicutt, Jr. (2004). "Secular Evolution and the Formation of Pseudobulges in Disk Galaxies". Annual Reviews of Astronomy and Astrophysics 42: 603-683.</ref>. The galaxy is also notable in that it has two ring structures<ref name="ned" />.

1 Nucleus
2 Inner and outer rings
3 Pseudobulge
4 Environment
5 See also
6 External links
7 References

[edit] Nucleus

M94 is classified as having a low ionization nuclear emission region (LINER) nucleus<ref name="hoetal1997">L. C. Ho, A. V. Filippenko, W. L. W. Sargent (1997). "A Search for "Dwarf" Seyfert Nuclei. III. Spectroscopic Parameters and Properties of the Host Galaxies". Astrophysical Journal Supplement 112: 315-390.</ref>. LINERs in general are characterized by optical spectra that reveal that ionized gas is present but the gas is only weakly ionized (i.e. the atoms are missing relatively few electrons).

[edit] 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 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">C. Muñoz-Tuñón, N. Caon, J. Aguerri, L. Alfonso (2004). "The Inner Ring of NGC 4736: Star Formation on a Resonant Pattern". Astronomical Journal 127: 58-74.</ref>.

[edit] Pseudobulge

In a paper published in 2004, John Kormendy and Robert Kennicutt argued that M94 contains a prototypical pseudobulge<ref name="kormendykennicutt04" />. A classical spiral galaxy is comprised 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.

[edit] Environment

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">R. B. Tully (1988). Nearby Galaxies Catalog. Cambridge: Cambridge University Press. ISBN 0-521-35299-1.</ref><ref name="garcia1993">A. Garcia (1993). "General study of group membership. II - Determination of nearby groups". Astronomy and Astrophysics Supplement 100: 47-90.</ref><ref name="giuricinetal2002">G. Giuricin, C. Marinoni, L. Ceriani, A. Pisani (2000). "Nearby Optical Galaxies: Selection of the Sample and Identification of Groups". Astrophysical Journal 543: 178-194.</ref> This group is one of many that lies within the Virgo Supercluster (i.e. the Local Supercluster).<ref name="tully1982">R. B. Tully (1982). "The Local Supercluster". Astrophysical Journal 257: 389-422.</ref>