NGC 185

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NGC 185
Caldwell 18 (50289818793).jpg
NGC 185 imaged by the Hubble Space Telescope
Observation data (J2000.0 [1] epoch)
Constellation Cassiopeia
Right ascension 00h 38m 57.970s [1]
Declination +48° 20′ 14.56″ [1]
Redshift −202 ± 3 km/s [2]
Distance 2.05 ± 0.13 Mly (630 ± 40 kpc) [3] [4] [5] [a]
Apparent magnitude  (V)10.1 [2]
Characteristics
Type dSph/dE3, [2] Sy2 [1]
Apparent size  (V)11.7′ × 10.0′ [2]
Notable features Satellite galaxy of the
Andromeda Galaxy
Other designations
UGC 396, [2] PGC 2329, [2] LEDA 2329, [1] Caldwell  18

NGC 185 (also known as Caldwell 18) is a dwarf spheroidal galaxy located 2.08 million light-years from Earth, appearing in the constellation Cassiopeia. It is a member of the Local Group, and is a satellite of the Andromeda Galaxy (M31). [6] NGC 185 was discovered by William Herschel on November 30, 1787, and he cataloged it "H II.707". [6] John Herschel observed the object again in 1833 when he cataloged it as "h 35", and then in 1864 when he cataloged it as "GC 90" within his General Catalogue of Nebulae and Clusters . [6] NGC 185 was first photographed between 1898 and 1900 by James Edward Keeler with the Crossley Reflector of Lick Observatory. [6] Unlike most dwarf elliptical galaxies, NGC 185 contains young stellar clusters, and star formation proceeded at a low rate until the recent past. NGC 185 has an active galactic nucleus (AGN) and is usually classified as a type 2 Seyfert galaxy, [7] though its status as a Seyfert is questioned. [8] It is possibly the closest Seyfert galaxy to Earth, and is the only known Seyfert in the Local Group.

Contents

Distance measurements

At least two techniques have been used to measure distances to NGC 185. The surface brightness fluctuations distance measurement technique estimates distances to galaxies based on the graininess of their appearance. The distance measured to NGC 185 using this technique is 2.08 ± 0.15 Mly (640 ± 50 kpc). [3] However, NGC 185 is close enough that the tip of the red giant branch (TRGB) method may be used to estimate its distance. The estimated distance to NGC 185 using this technique is 2.02 ± 0.2 Mly (620 ± 60 kpc). [4] [5]

Star formation

Martínez-Delgado, Aparicio, & Gallart (1999) looked into the star formation history of NGC 185 and found that the majority of star formation in NGC 185 happened at early times. [8] In the last ~1 Gyr, stars have formed only near the center of this galaxy. Walter Baade discovered young blue objects within this galaxy in 1951, but these have turned out to be star clusters and not individual stars. A supernova remnant near the center was also discovered by Martínez-Delgado et al. [9]

See also

Related Research Articles

<span class="mw-page-title-main">Local Group</span> Group of galaxies that includes the Milky Way

The Local Group is the galaxy group that includes the Milky Way, where Earth is located. It has a total diameter of roughly 3 megaparsecs (10 million light-years; 9×1019 kilometres), and a total mass of the order of 2×1012 solar masses (4×1042 kg). It consists of two collections of galaxies in a "dumbbell" shape; the Milky Way and its satellites form one lobe, and the Andromeda Galaxy and its satellites constitute the other. The two collections are separated by about 800 kiloparsecs (3×10^6 ly; 2×1019 km) and are moving toward one another with a velocity of 123 km/s. The group itself is a part of the larger Virgo Supercluster, which may be a part of the Laniakea Supercluster. The exact number of galaxies in the Local Group is unknown as some are occluded by the Milky Way; however, at least 80 members are known, most of which are dwarf galaxies.

<span class="mw-page-title-main">Triangulum Galaxy</span> Spiral galaxy in the constellation Triangulum

The Triangulum Galaxy is a spiral galaxy 2.73 million light-years (ly) from Earth in the constellation Triangulum. It is catalogued as Messier 33 or NGC (New General Catalogue) 598. With the D25 isophotal diameter of 18.74 kiloparsecs (61,100 light-years), the Triangulum Galaxy is the third-largest member of the Local Group of galaxies, behind the Andromeda Galaxy and the Milky Way.

<span class="mw-page-title-main">Pegasus Dwarf Spheroidal Galaxy</span> Dwarf spheroidal galaxy in the constellation Pegasus

The Pegasus Dwarf Spheroidal is a dwarf spheroidal galaxy about 2.7 million light-years away in the constellation Pegasus. The Pegasus Dwarf is a member of the Local Group and a satellite galaxy of the Andromeda Galaxy (M31).

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

The Sombrero Galaxy is a peculiar galaxy of unclear classification in the constellation borders of Virgo and Corvus, being about 9.55 megaparsecs from the Milky Way galaxy. 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 has an isophotal diameter of approximately 29.09 to 32.32 kiloparsecs, making it slightly bigger in size than the Milky Way.

<span class="mw-page-title-main">NGC 404</span> Galaxy in the constellation Andromeda

NGC 404 is a field galaxy located about 10 million light years away in the constellation Andromeda. It was discovered by William Herschel in 1784, and is visible through small telescopes. NGC 404 lies just beyond the Local Group and does not appear gravitationally bound to it. It is located within 7 arc-minutes of second magnitude star Mirach, making it a difficult target to observe or photograph and granting it the nickname "Mirach's Ghost".

<span class="mw-page-title-main">Messier 32</span> Dwarf elliptical galaxy in the constellation Andromeda

Messier 32 is a dwarf "early-type" galaxy about 2,650,000 light-years (810,000 pc) from the Solar System, appearing in the constellation Andromeda. M32 is a satellite galaxy of the Andromeda Galaxy (M31) and was discovered by Guillaume Le Gentil in 1749.

<span class="mw-page-title-main">Messier 94</span> Galaxy in the constellation Canes Venatici

Messier 94 is a spiral galaxy in the mid-northern constellation Canes Venatici. It was discovered by Pierre Méchain in 1781, 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. The galaxy has two ring structures.

<span class="mw-page-title-main">Messier 110</span> Satellite galaxy of the Andromeda Galaxy

Messier 110, or M110, also known as NGC 205, is a dwarf elliptical galaxy that is a satellite of the Andromeda Galaxy in the Local Group.

<span class="mw-page-title-main">Sculptor Galaxy</span> Intermediate spiral galaxy in the constellation Sculptor

The Sculptor Galaxy is an intermediate spiral galaxy in the constellation Sculptor. The Sculptor Galaxy is a starburst galaxy, which means that it is currently undergoing a period of intense star formation.

<span class="mw-page-title-main">NGC 891</span> Galaxy in the constellation Andromeda

NGC 891 is an edge-on unbarred spiral galaxy about 30 million light-years away in the constellation Andromeda. It was discovered by William Herschel on October 6, 1784. The galaxy is a member of the NGC 1023 group of galaxies in the Local Supercluster. It has an H II nucleus.

<span class="mw-page-title-main">Andromeda I</span> Dwarf galaxy in the constellation Andromeda

Andromeda I is a dwarf spheroidal galaxy (dSph) about 2.40 million light-years away in the constellation Andromeda. Andromeda I is part of the local group of galaxies and a satellite galaxy of the Andromeda Galaxy (M31). It is roughly 3.5 degrees south and slightly east of M31. As of 2005, it is the closest known dSph companion to M31 at an estimated projected distance of ~40 kpc or ~150,000 light-years.

<span class="mw-page-title-main">NGC 147</span> Galaxy in the constellation Cassiopeia

NGC 147 is a dwarf spheroidal galaxy about 2.58 Mly away in the constellation Cassiopeia. NGC 147 is a member of the Local group of galaxies and a satellite galaxy of the Andromeda Galaxy (M31). It forms a physical pair with the nearby galaxy NGC 185, another remote satellite of M31. It was discovered by John Herschel in September 1829. Visually it is both fainter and slightly larger than NGC 185. This means that NGC 147 is more difficult to see than NGC 185, which is visible in small telescopes. In the Webb Society Deep-Sky Observer's Handbook, the visual appearance of NGC 147 is described as follows:

Large, quite faint, irregularly round; it brightens in the middle to a stellar nucleus.

<span class="mw-page-title-main">IC 342</span> Spiral galaxy in the constellation Camelopardalis

IC 342 is an intermediate spiral galaxy in the constellation Camelopardalis, located relatively close to the Milky Way. Despite its size and actual brightness, its location behind dusty areas near the galactic equator makes it difficult to observe, leading to the nickname "The Hidden Galaxy", though it can readily be detected even with binoculars. If the galaxy were not obscured, it would be visible by naked eye. The dust makes it difficult to determine its precise distance; modern estimates range from about 7 million light-years (Mly) to about 11 Mly. The galaxy was discovered by William Frederick Denning in 1892. It is one of the brightest in the IC 342/Maffei Group, one of the closest galaxy groups to the Local Group. Edwin Hubble first thought it to be in the Local Group, but it was later determined not to be a member.

<span class="mw-page-title-main">NGC 2683</span> Galaxy in the constellation Lynx

NGC 2683 is a field spiral galaxy in the northern constellation of Lynx. It was nicknamed the "UFO Galaxy" by the Astronaut Memorial Planetarium and Observatory. It was discovered by the astronomer William Herschel on February 5, 1788.

<span class="mw-page-title-main">NGC 3227</span> Galaxy in the constellation Leo

NGC 3227 is an intermediate spiral galaxy that is interacting with the dwarf elliptical galaxy NGC 3226. The two galaxies are one of several examples of a spiral with a dwarf elliptical companion that are listed in the Atlas of Peculiar Galaxies. Both galaxies may be found in the constellation Leo. It is a member of the NGC 3227 Group of galaxies, which is a member of the Leo II Groups, a series of galaxies and galaxy clusters strung out from the right edge of the Virgo Supercluster.

<span class="mw-page-title-main">NGC 3077</span> Galaxy in the constellation Ursa Major

NGC 3077 is a small disrupted elliptical galaxy, a member of the M81 Group, which is located in the northern constellation Ursa Major. Despite being similar to an elliptical galaxy in appearance, it is peculiar for two reasons. First, it shows wispy edges and scattered dust clouds that are probably a result of gravitational interaction with its larger neighbors, similar to the galaxy M82. Second, this galaxy has an active nucleus. This caused Carl Seyfert in 1943 to include it in his list of galaxies, which are now called Seyfert Galaxies. However, NGC 3077, though an emission line galaxy, is today no longer classified as a Seyfert galaxy.

<span class="mw-page-title-main">NGC 5102</span> Lenticular galaxy in the M83 group of galaxies

NGC 5102, also known as Iota's Ghost, is a lenticular galaxy in the Centaurus A/M83 Group of galaxies. It was discovered by John Herschel in 1835.

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

The Dorado Group is a loose concentration of galaxies containing both spirals and ellipticals. It is generally considered a 'galaxy group' but may approach the size of a 'galaxy cluster'. It lies primarily in the southern constellation Dorado and is one of the richest galaxy groups of the Southern Hemisphere. Gérard de Vaucouleurs was the first to identify it in 1975 as a large complex nebulae II in the Dorado region, designating it as G16.

<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">NGC 5846</span> Galaxy in the constellation Virgo

NGC 5846 is an elliptical galaxy located in the constellation Virgo. It is located at a distance of circa 90 million light years from Earth, which, given its apparent dimensions, means that NGC 5846 is about 110,000 light years across. It was discovered by William Herschel on February 24, 1786. It lies near 110 Virginis and is part of the Herschel 400 Catalogue. It is a member of the NGC 5846 Group of galaxies, itself one of the Virgo III Groups strung out to the east of the Virgo Supercluster of galaxies.

References

  1. 1 2 3 4 5 "NGC 185". SIMBAD . Centre de données astronomiques de Strasbourg . Retrieved 2014-05-05.
  2. 1 2 3 4 5 6 "NASA/IPAC Extragalactic Database". Results for NGC 185. Retrieved 2006-11-29.
  3. 1 2 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". Astrophysical Journal. 546 (2): 681–693. arXiv: astro-ph/0011223 . Bibcode:2001ApJ...546..681T. doi:10.1086/318301. S2CID   17628238.
  4. 1 2 I. D. Karachentsev; V. E. Karachentseva; W. K. Huchtmeier; D. I. Makarov (2004). "A Catalog of Neighboring Galaxies". Astronomical Journal. 127 (4): 2031–2068. Bibcode:2004AJ....127.2031K. doi: 10.1086/382905 .
  5. 1 2 Karachentsev, I. D.; Kashibadze, O. G. (2006). "Masses of the local group and of the M81 group estimated from distortions in the local velocity field". Astrophysics. 49 (1): 3–18. Bibcode:2006Ap.....49....3K. doi:10.1007/s10511-006-0002-6. S2CID   120973010.
  6. 1 2 3 4 "SEDS — NGC 185".
  7. ↑ Ho, Luis C.; Filippenko, Alexei V.; Sargent, Wallace L. W. (October 1997). "A Search for 'Dwarf' Seyfert Nuclei. III. Spectroscopic Parameters and Properties of the Host Galaxies". The Astrophysical Journal Supplement Series. 112 (2): 315–390. arXiv: astro-ph/9704107 . Bibcode:1997ApJS..112..315H. doi:10.1086/313041. S2CID   17086638.
  8. 1 2 Martins, Lucimara P.; Lanfranchi, Gustavo; Goncalves, Denise R.; Magrini, Laura; Teodorescu, Ana M.; Quireza, Cintia (February 2012). "The ionization mechanism of NGC 185: How to fake a Seyfert galaxy?". Monthly Notices of the Royal Astronomical Society. 419 (4): 3159–3166. arXiv: 1110.5891 . Bibcode:2012MNRAS.419.3159M. doi: 10.1111/j.1365-2966.2011.19954.x . S2CID   119188037.
  9. ↑ van den Bergh, Sidney (April 2000). "Updated Information on the Local Group". The Publications of the Astronomical Society of the Pacific. 112 (770): 529–536. arXiv: astro-ph/0001040 . Bibcode:2000PASP..112..529V. doi:10.1086/316548. S2CID   1805423.
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