NGC 4494

Last updated
NGC 4494
NGC 4494 2MASS.jpg
NGC 4494 by 2MASS
Observation data (J2000 epoch)
Constellation Coma Berenices
Right ascension 12h 31m 24.1s [1]
Declination +25° 46′ 31″ [1]
Redshift 1342 ± 5 km/s [1]
Distance 45 ± 10 Mly (13.7 ± 3.2 Mpc) [1]
Apparent magnitude  (V)9.7 [2]
Characteristics
Type E1-2 [1]
Apparent size  (V)4.8′ × 3.5′ [1]
Other designations
UGC 7662, MCG +04-30-002, PGC 41441 [1]

NGC 4494 is an elliptical galaxy located in the constellation Coma Berenices. It is located at a distance of circa 45 million light years from Earth, which, given its apparent dimensions, means that NGC 4494 is about 60,000 light years across. It was discovered by William Herschel in 1785.

Contents

Characteristics

The galaxy hosts a supermassive black hole with estimated mass 26.9 ± 20.4 millions M⊙, based on velocity dispersion. [3] A nuclear dust ring has been detected in NGC 4494, based on observations by the Hubble Space Telescope. It has semimajor axis 0.6 arcseconds, which corresponds to 60 parsec at the distance of NGC 4494. [4] Its ring is symmetric, implying that the dust has settled in this galaxy, [5] after the galaxy merger with a relatively gas rich galaxy that led to its creation. [6] The core of NGC 4494 is kinematically decoupled, as with many elliptical galaxies, probably a result of a galaxy merger. [7]

Dark matter

In observations by XMM-Newton observatory, the galaxy was quite faint in X-rays, nearly two orders of magnitude fainter than galaxies with similar optical luminosities. This fact has been attributed to lack of dark matter and hot gas of the galaxy. [8]

The amount of dark matter existing in the halo of NGC 4494 has been debated. [9] The galaxy is characterised as "naked" by Romanowsky et al., [10] Napolitano et al. found that the dark matter halo has unexpectedly low central density [11] and the analysis by Deason et al. revealed an unusually low dark matter fraction, 0.32 ± 0.12 at 5Re. [12] Rodionov and Athanassoula tried to set strict constraint to the halo mass, but with only partial success. [7] On the other hand, Morganti et al. found the dark matter fraction to be about 0.6 ± 0.1 at 5Re, with particularly high dark matter fraction inside ~ 3Re. [9]

Nearby galaxies

NGC 4494 belongs to the NGC 4565 group, named after the spiral galaxy NGC 4565. Other members of the group are NGC 4525, NGC 4562, NGC 4570, NGC 4725 and NGC 4747. [13] NGC 4494 is also a member of the Coma I Group [14] [15] [16] [17] which is part of the Virgo Supercluster. [18]

Related Research Articles

The study of galaxy formation and evolution is concerned with the processes that formed a heterogeneous universe from a homogeneous beginning, the formation of the first galaxies, the way galaxies change over time, and the processes that have generated the variety of structures observed in nearby galaxies. Galaxy formation is hypothesized to occur from structure formation theories, as a result of tiny quantum fluctuations in the aftermath of the Big Bang. The simplest model in general agreement with observed phenomena is the Lambda-CDM model—that is, that clustering and merging allows galaxies to accumulate mass, determining both their shape and structure. Hydrodynamics simulation, which simulates both baryons and dark matter, is widely used to study galaxy formation and evolution.

<span class="mw-page-title-main">Galaxy rotation curve</span> Observed discrepancy in galactic angular momenta

The rotation curve of a disc galaxy is a plot of the orbital speeds of visible stars or gas in that galaxy versus their radial distance from that galaxy's centre. It is typically rendered graphically as a plot, and the data observed from each side of a spiral galaxy are generally asymmetric, so that data from each side are averaged to create the curve. A significant discrepancy exists between the experimental curves observed, and a curve derived by applying gravity theory to the matter observed in a galaxy. Theories involving dark matter are the main postulated solutions to account for the variance.

<span class="mw-page-title-main">Messier 84</span> Galaxy in the constellation Virgo

Messier 84 or M84, also known as NGC 4374, is a giant elliptical or lenticular galaxy in the constellation Virgo. Charles Messier discovered the object in 1781 in a systematic search for "nebulous objects" in the night sky. It is the 84th object in the Messier Catalogue and in the heavily populated core of the Virgo Cluster of galaxies, part of the local supercluster.

<span class="mw-page-title-main">Galaxy merger</span> Merger whereby at least two galaxies collide

Galaxy mergers can occur when two galaxies collide. They are the most violent type of galaxy interaction. The gravitational interactions between galaxies and the friction between the gas and dust have major effects on the galaxies involved. The exact effects of such mergers depend on a wide variety of parameters such as collision angles, speeds, and relative size/composition, and are currently an extremely active area of research. Galaxy mergers are important because the merger rate is a fundamental measurement of galaxy evolution. The merger rate also provides astronomers with clues about how galaxies bulked up over time.

<span class="mw-page-title-main">NGC 1566</span> Galaxy in the constellation Dorado

NGC 1566, sometimes known as the Spanish Dancer, is an intermediate spiral galaxy in the constellation Dorado, positioned about 3.5° to the south of the star Gamma Doradus. It was discovered on May 28, 1826 by Scottish astronomer James Dunlop. At 10th magnitude, it requires a telescope to view. The distance to this galaxy remains elusive, with measurements ranging from 6 Mpc up to 21 Mpc.

<span class="mw-page-title-main">NGC 1052</span> Elliptical galaxy in the constellation Cetus

NGC 1052 is an elliptical galaxy in the constellation Cetus. It was discovered on January 10, 1785 by the astronomer William Herschel. It is a member of the eponymous NGC 1052 Group.

<span class="mw-page-title-main">NGC 988</span> Galaxy in the constellation Cetus

NGC 988 is a spiral galaxy located in the constellation Cetus. It lies at a distance of 50 million light years from Earth, which, given its apparent dimensions, means that NGC 988 is about 75,000 light years across. Magnitude 7.1 HD 16152 is superposed 52" northwest of the center of NGC 988. The galaxy was discovered by Édouard Jean-Marie Stephan in 1879. One ultraluminous X-ray source has been detected in NGC 988.

<span class="mw-page-title-main">NGC 3941</span> Galaxy in the constellation Ursa Major

NGC 3941 is a barred lenticular galaxy located in the constellation Ursa Major. It is located at a distance of circa 40 million light years from Earth, which, given its apparent dimensions, means that NGC 3941 is about 40,000 light years across. It was discovered by William Herschel in 1787.

<span class="mw-page-title-main">NGC 4458</span> Galaxy in the Virgo constellation

NGC 4458 is an elliptical galaxy located about 54 million light-years away in the constellation of Virgo. It was discovered by astronomer William Herschel on April 12, 1784. NGC 4458 is a member of Markarian's Chain which is part of the Virgo Cluster. It is in a pair with the galaxy NGC 4461. NGC 4458 and NGC 4461 are interacting with each other.

<span class="mw-page-title-main">NGC 720</span> Galaxy in the constellation Cetus

NGC 720 is an elliptical galaxy located in the constellation Cetus. It is located at a distance of circa 80 million light years from Earth, which, given its apparent dimensions, means that NGC 720 is about 110,000 light years across. It was discovered by William Herschel on October 3, 1785. The galaxy is included in the Herschel 400 Catalogue. It lies about three and a half degrees south and slightly east from zeta Ceti.

<span class="mw-page-title-main">NGC 5982</span> Galaxy in the constellation Draco

NGC 5982 is an elliptical galaxy located in the constellation Draco. It is located at a distance of circa 130 million light years from Earth, which, given its apparent dimensions, means that NGC 5982 is about 100,000 light years across. It was discovered by William Herschel on May 25, 1788.

<span class="mw-page-title-main">NGC 3489</span> Galaxy in the constellation Leo

NGC 3489 is a lenticular galaxy located in the constellation Leo. It is located at a distance of circa 30 million light years from Earth, which, given its apparent dimensions, means that NGC 3489 is about 30,000 light years across. It was discovered by William Herschel on April 8, 1784. NGC 3489 is a member of the Leo Group.

<span class="mw-page-title-main">NGC 4665</span> Galaxy in the constellation of Virgo

NGC 4665, also catalogued as NGC 4624 and NGC 4664, is a barred lenticular or spiral galaxy located in the constellation Virgo. It is a member of the Virgo II Groups, a series of galaxies and galaxy clusters strung out from the southern edge of the Virgo Supercluster. It is located at a distance of circa 60 million light years from Earth, which, given its apparent dimensions, means that NGC 4665 is about 75,000 light years across. NGC 4665 lies 2 and 3/4 degrees east-south east of Delta Virginis and 50 arcminutes southwest of 35 Virginis. It can be viewed through a moderately sized telescope with 23x magnification, forming a pair with an 11th magnitude star 1.5 arcminutes southwest. It is part of the Herschel 400 Catalogue.

<span class="mw-page-title-main">NGC 4636</span> Galaxy in the constellation Virgo

NGC 4636 is an elliptical galaxy located in the constellation Virgo. It is a member of the NGC 4753 Group of galaxies, which is a member of the Virgo II Groups, a series of galaxies and galaxy clusters strung out from the southern edge of the Virgo Supercluster. It is located at a distance of about 55 million light years from Earth, which, given its apparent dimensions, means that NGC 4636 is about 105,000 light years across.

<span class="mw-page-title-main">IC 1459</span> Elliptical galaxy in the constellation of Grus

IC 1459 is an elliptical galaxy located in the constellation Grus. It is located at a distance of circa 85 million light-years from Earth, which, given its apparent dimensions, means that IC 1459 is about 130,000 light-years across. It was discovered by Edward Emerson Barnard in 1892.

<span class="mw-page-title-main">NGC 4278</span> Galaxy in the constellation Coma Berenices

NGC 4278 is an elliptical galaxy located in the constellation Coma Berenices. It is located at a distance of circa 55 million light years from Earth, which, given its apparent dimensions, means that NGC 4278 is about 65,000 light years across. It was discovered by William Herschel on March 13, 1785. NGC 4278 is part of the Herschel 400 Catalogue and can be found about one and 3/4 of a degree northwest of Gamma Comae Berenices even with a small telescope.

<span class="mw-page-title-main">NGC 2974</span> Galaxy in the constellation Sextans

NGC 2974 is a lenticular galaxy located in the constellation Sextans. It is located at a distance of circa 90 million light years from Earth, which, given its apparent dimensions, means that NGC 2974 is about 90,000 light years across. It was discovered by William Herschel on January 6, 1785. NGC 2974 is located in the sky about 2 and a half degrees south-south east of Iota Hydrae and more than 6 degrees northeast of Alphard. A 10th magnitude star lies next to the galaxy, thus making it a challenging object at low magnifications. NGC 2974 is part of the Herschel 400 Catalogue.

<span class="mw-page-title-main">NGC 3741</span> Galaxy in the constellation Ursa Major

NGC 3741 is an irregular galaxy in the constellation Ursa Major. It was discovered by John Herschel on March 19, 1828. At a distance of about 10 million light-years, it is located in the M94 Group. It is relatively undisturbed by other galaxies.

<span class="mw-page-title-main">NGC 4365</span> Elliptical galaxy in the constellation Virgo

NGC 4365 is an elliptical galaxy located in the constellation Virgo. It was discovered by William Herschel on April 13, 1784.

References

  1. 1 2 3 4 5 6 7 "NASA/IPAC Extragalactic Database". Results for NGC 4494. Retrieved 2016-01-18.
  2. ↑ "NGC 4494". SIMBAD . Centre de données astronomiques de Strasbourg . Retrieved 2017-06-19.
  3. ↑ Sadoun, Raphael; Colin, Jacques (11 October 2012). "-σ relation between supermassive black holes and the velocity dispersion of globular cluster systems". Monthly Notices of the Royal Astronomical Society: Letters. 426 (1): L51–L55. arXiv: 1204.0144 . Bibcode:2012MNRAS.426L..51S. doi:10.1111/j.1745-3933.2012.01321.x. S2CID   117185846.
  4. ↑ Comerón, S.; Knapen, J. H.; Beckman, J. E.; Laurikainen, E.; Salo, H.; Martínez-Valpuesta, I.; Buta, R. J. (March 2010). "AINUR: Atlas of Images of NUclear Rings". Monthly Notices of the Royal Astronomical Society. 402 (4): 2462–2490. arXiv: 0908.0272 . Bibcode:2010MNRAS.402.2462C. doi:10.1111/j.1365-2966.2009.16057.x. S2CID   18376628.
  5. ↑ Lauer, Tod R.; Faber, S. M.; Gebhardt, Karl; Richstone, Douglas; Tremaine, Scott; Ajhar, Edward A.; Aller, M. C.; Bender, Ralf; Dressler, Alan; Filippenko, Alexei V.; Green, Richard; Grillmair, Carl J.; Ho, Luis C.; Kormendy, John; Magorrian, John; Pinkney, Jason; Siopis, Christos (May 2005). "The Centers of Early-Type Galaxies with Hubble Space Telescope. V. New WFPC2 Photometry". The Astronomical Journal. 129 (5): 2138–2185. arXiv: astro-ph/0412040 . Bibcode:2005AJ....129.2138L. doi:10.1086/429565. S2CID   15473461.
  6. ↑ Foster, Caroline; Spitler, Lee R.; Romanowsky, Aaron J.; Forbes, Duncan A.; Pota, Vincenzo; Bekki, Kenji; Strader, Jay; Proctor, Robert N.; Arnold, Jacob A.; Brodie, Jean P. (21 August 2011). "Global properties of 'ordinary' early-type galaxies: photometry and spectroscopy of stars and globular clusters in NGC 4494". Monthly Notices of the Royal Astronomical Society. 415 (4): 3393–3416. arXiv: 1104.5503 . Bibcode:2011MNRAS.415.3393F. doi:10.1111/j.1365-2966.2011.18965.x. S2CID   54172134.
  7. 1 2 Rodionov, S. A.; Athanassoula, E. (1 January 2011). "Dynamical models of the elliptical galaxy NGC 4494". Monthly Notices of the Royal Astronomical Society. 410 (1): 111–126. arXiv: 1007.5200 . Bibcode:2011MNRAS.410..111R. doi:10.1111/j.1365-2966.2010.17429.x. S2CID   119122130.
  8. ↑ O'Sullivan, E.; Ponman, T. J. (April 2004). "XMM-Newton and Chandra observations of three X-ray-faint early-type galaxies". Monthly Notices of the Royal Astronomical Society. 349 (2): 535–546. arXiv: astro-ph/0312266 . Bibcode:2004MNRAS.349..535O. doi:10.1111/j.1365-2966.2004.07518.x. S2CID   17208484.
  9. 1 2 Morganti, L.; Gerhard, O.; Coccato, L.; Martinez-Valpuesta, I.; Arnaboldi, M. (11 April 2013). "Elliptical galaxies with rapidly decreasing velocity dispersion profiles: NMAGIC models and dark halo parameter estimates for NGC 4494". Monthly Notices of the Royal Astronomical Society. 431 (4): 3570–3588. arXiv: 1303.2688 . Bibcode:2013MNRAS.431.3570M. doi:10.1093/mnras/stt442. S2CID   56274333.
  10. ↑ Romanowsky, A. J. (19 September 2003). "A Dearth of Dark Matter in Ordinary Elliptical Galaxies". Science. 301 (5640): 1696–1698. arXiv: astro-ph/0308518 . Bibcode:2003Sci...301.1696R. doi:10.1126/science.1087441. PMID   12947033. S2CID   120137872.
  11. ↑ Napolitano, N. R.; Romanowsky, A. J.; Coccato, L.; Capaccioli, M.; Douglas, N. G.; Noordermeer, E.; Gerhard, O.; Arnaboldi, M.; De Lorenzi, F.; Kuijken, K.; Merrifield, M. R.; O'Sullivan, E.; Cortesi, A.; Das, P.; Freeman, K. C. (21 February 2009). "The Planetary Nebula Spectrograph elliptical galaxy survey: the dark matter in NGC 4494". Monthly Notices of the Royal Astronomical Society. 393 (2): 329–353. arXiv: 0810.1291 . Bibcode:2009MNRAS.393..329N. doi:10.1111/j.1365-2966.2008.14053.x. S2CID   54039999.
  12. ↑ Deason, A. J; Belokurov, V.; Evans, N. W.; McCarthy, I. G. (20 March 2012). "Elliptical Galaxy Masses Out to Five Effective Radii: The Realm of Dark Matter". The Astrophysical Journal. 748 (1): 2. arXiv: 1110.0833 . Bibcode:2012ApJ...748....2D. doi:10.1088/0004-637X/748/1/2. S2CID   119109261.
  13. ↑ Makarov, Dmitry; Karachentsev, Igor (21 April 2011). "Galaxy groups and clouds in the local (z~ 0.01) Universe". Monthly Notices of the Royal Astronomical Society. 412 (4): 2498–2520. arXiv: 1011.6277 . Bibcode:2011MNRAS.412.2498M. doi:10.1111/j.1365-2966.2010.18071.x. S2CID   119194025. Archived from the original on 31 January 2016. Retrieved 20 July 2017.
  14. ↑ "Nearby Groups of Galaxies". ned.ipac.caltech.edu. Retrieved 2018-05-20.
  15. ↑ R. B. Tully (1988). Nearby Galaxies Catalog. Cambridge: Cambridge University Press. ISBN   978-0-521-35299-4.
  16. ↑ A. Garcia (1993). "General study of group membership. II - Determination of nearby groups". Astronomy and Astrophysics Supplement . 100: 47–90. Bibcode:1993A&AS..100...47G.
  17. ↑ Giuricin, Giuliano; Marinoni, Christian; Ceriani, Lorenzo; Pisani, Armando (2000). "Nearby Optical Galaxies: Selection of the Sample and Identification of Groups". The Astrophysical Journal. 543 (1): 178. arXiv: astro-ph/0001140 . Bibcode:2000ApJ...543..178G. doi:10.1086/317070. ISSN   0004-637X. S2CID   9618325.
  18. ↑ Gregory, Stephen A.; Thompson, Laird A. (April 1977). "The Coma i Galaxy Cloud". The Astrophysical Journal. 213: 345–350. Bibcode:1977ApJ...213..345G. doi:10.1086/155160. ISSN   0004-637X.


This page is based on this Wikipedia article
Text is available under the CC BY-SA 4.0 license; additional terms may apply.
Images, videos and audio are available under their respective licenses.