Messier 94

Coordinates: Sky map 12h 50m 53.1s, +41° 07′ 14″
Source: Wikipedia, the free encyclopedia.

"Cat's Eye Galaxy" redirects here. For the nebula, see Cat's Eye Nebula.
moa[5]
Other designations
NGC 4736, UGC 7996, PGC 43495[5]

Messier 94 (also known as NGC 4736, Cat's Eye Galaxy, Crocodile Eye Galaxy, or Croc's Eye Galaxy

northern constellation Canes Venatici. It was discovered by Pierre Méchain in 1781,[9]
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.[10] The galaxy has two ring structures.[5]

Structure

Detail of the central area of M94

M94 is classified as having a

low ionization nuclear emission region (LINER) nucleus.[11] 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).

M94 has an inner ring with a diameter of 70

starburst ring. This star formation is fueled by gas driven dynamically into the ring by the inner oval-shaped bar-like structure.[12]

A 2009 study

spiral arms
when viewed in mid-IR and UV. The study found that the outer disk of this galaxy is active. It contains approximately 23% of the galaxy's total stellar mass and contributes about 10% of the galaxy's new stars. In fact, the star formation rate of the outer disk is approximately two times greater than the inner disk because it is more efficient per unit of stellar mass.

There are several possible external events that could have led to the origin of M94's outer disk including the accretion of a satellite galaxy or the gravitational interaction with a nearby star system. However, further research found problems with each of these scenarios. Therefore, the report concludes that the inner disk of M94 is an oval distortion which led to the creation of this galaxy's peripheral disk.

In a paper published in 2004,

pseudobulge.[10] 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.

In 2008 a study was published

MOND, also have difficulty explaining this galaxy.[15]
This result has yet to be confirmed or accepted by other research groups, however, and has not actually been tested against the predictions of standard galaxy formation models.

Location

M94 as seen in at various wavelengths of light

At least two techniques have been used to measure distances to M94. The surface brightness fluctuations 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 Mly (5.2 ± 0.4 Mpc).[1] 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 Mly (4.7 ± 0.6 Mpc).[2] Averaged together, these distance measurements give a distance estimate of 16.0 ± 1.3 Mly (4.9 ± 0.4 Mpc).

M94 is one of the brightest galaxies within the

group of galaxies that contains between 16 and 24 galaxies.[16][17][18] This group is one of many that lie within the Virgo Supercluster (i.e. the Local Supercluster).[19] 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.[2][20]

See also

References

  1. ^ a b J. L. Tonry; A. Dressler; J. P. Blakeslee; E. A. Ajhar; et al. (2001). "The SBF Survey of Galaxy Distances. IV. SBF Magnitudes, Colors, and Distances".
    S2CID 17628238
    .
  2. ^ a b c I. D. Karachentsev; M. E. Sharina; A. E. Dolphin; E. K. Grebel; et al. (2003). "Galaxy flow in the Canes Venatici I cloud".
    S2CID 6310283
    .
  3. ^ average(17.0 ± 1.4, 15 ± 2) = ((17.0 + 15) / 2) ± ((1.42 + 22)0.5 / 2) = 16.0 ± 1.3
  4. ISBN 978-0-933346-51-2
    .
  5. ^ a b c d e f g h i j "NASA/IPAC Extragalactic Database". Results for M94. Retrieved 9 November 2006.
  6. ^ "Messier 94". SEDS Messier Catalog. Retrieved 30 April 2022.
  7. ^ "Messier 94: Cat's Eye Galaxy". Messier Objects. 15 August 2015. Retrieved 24 February 2024.
  8. ^ Anderson, Natali (19 October 2015). "Hubble Captures Stunning Image of Messier 94". Sci.News. Retrieved 24 February 2024.
  9. ^ Kepple, George Robert; Glen W. Sanner (1998). The Night Sky Observer's Guide. Vol. 2.
    ISBN 978-0-943396-60-6
    .
  10. ^ a b J. Kormendy; R. C. Kennicutt Jr. (2004). "Secular Evolution and the Formation of Pseudobulges in Disk Galaxies".
    S2CID 515479
    .
  11. ^ 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".
    S2CID 17086638
    .
  12. ^ C. Muñoz-Tuñón; N. Caon; J. Aguerri; L. Alfonso (2004). "The Inner Ring of NGC 4736: Star Formation on a Resonant Pattern".
    doi:10.1086/380610
    .
  13. ^ I. Trujillo; I. Martinez-Valpuesta; D. Martinez-Delgado; J. Penarrubia; et al. (2009). "Unveiling the Nature of M94's (NGC4736) Outer Region: A Panchromatic Perspective".
    S2CID 16368604
    .
  14. ^ J. Jałocha; Ł. Bratek; M. Kutschera (2008). "Is Dark Matter Present in NGC 4736? An Iterative Spectral Method for Finding Mass Distribution in Spiral Galaxies".
    S2CID 3009937
    .
  15. ^ Battersby, Stephen (6 February 2008). "Galaxy without dark matter puzzles astronomers". New Scientist.
  16. ^ R. B. Tully (1988). Nearby Galaxies Catalog.
    ISBN 978-0-521-35299-4
    .
  17. ^ A. Garcia (1993). "General study of group membership. II – Determination of nearby groups".
    Bibcode:1993A&AS..100...47G
    .
  18. ^ G. Giuricin; C. Marinoni; L. Ceriani; A. Pisani (2000). "Nearby Optical Galaxies: Selection of the Sample and Identification of Groups".
    S2CID 9618325
    .
  19. doi:10.1086/159999
    .
  20. ^ I. D. Karachentsev (2005). "The Local Group and Other Neighboring Galaxy Groups".
    S2CID 119385141
    .

External links

Wikimedia Commons has media related to Messier 94.
Retrieved from "https://en.wikipedia.org/w/index.php?title=Messier_94&oldid=1209958623"