Andromeda IV

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Andromeda IV
Andromeda IV Hubble WikiSky.jpg
Andromeda IV just about 30″ to the right from TYC 2801-551-1 star (mag: 10.3); HST
Observation data (J2000 epoch)
Constellation Andromeda
Right ascension 00h 42m 32.3s [1]
Declination +40° 34′ 19″ [1]
Redshift 256 ± 9 km/s [1]
Apparent magnitude  (V)16.6B [1]
Characteristics
Type Dwarf irregular [1]
Apparent size  (V)1.3′ × 1.0′ [1]
Other designations
And IV, [1] PGC 2544 [1]

Andromeda IV (And IV) is an isolated irregular dwarf galaxy. The moderate surface brightness, a very blue color, low current star formation rate and low metallicity are consistent with it being a small (background) dwarf irregular galaxy, perhaps similar to Local Group dwarfs such as IC 1613 and Sextans A. Arguments based on the observed radial velocity and the tentative detection of the RGB tip suggest that it lies well outside the confines of the Local Group. [2]

Contents

Further study using the Hubble Space Telescope has shown it to be a solitary irregular dwarf galaxy. The galaxy is between 22 and 24 million light years from Earth, and so is not close to the Andromeda Galaxy at all. The galaxy is severely isolated. The Holmberg diameter is 1880 parsecs, but neutral atomic hydrogen gas extends more than eight times further out in a disk. The galaxy is very dark, and the baryonic mass to dark matter ratio is 0.11. [3] [4]

History

It was discovered by Sidney van den Bergh in 1972. [5]

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. 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">Andromeda Galaxy</span> Barred spiral galaxy in the Local Group

The Andromeda Galaxy is a barred spiral galaxy and is the closest major galaxy to the Milky Way, where the Solar System resides. It was originally named the Andromeda Nebula and is cataloged as Messier 31, M31, and NGC 224. Andromeda has a diameter of about 46.56 kiloparsecs and is approximately 765 kpc from Earth. The galaxy's name stems from the area of Earth's sky in which it appears, the constellation of Andromeda, which itself is named after the princess who was the wife of Perseus in Greek mythology.

<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">Pegasus Dwarf Irregular Galaxy</span> Dwarf irregular galaxy in the constellation of Pegasus

The Pegasus Dwarf Irregular Galaxy is a dwarf irregular galaxy in the direction of the constellation Pegasus. It was discovered by A. G. Wilson in the 1950s. The Pegasus Dwarf is a companion of the Andromeda Galaxy in the Local Group.

<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">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 3109</span> Galaxy in the constellation Hydra

NGC 3109 is a small barred Magellanic type spiral or irregular galaxy around 4.34 Mly away in the direction of the constellation of Hydra. NGC 3109 is believed to be tidally interacting with the dwarf elliptical galaxy Antlia Dwarf. It was discovered by John Herschel on March 24, 1835 while he was in what is now South Africa.

<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">Wolf–Lundmark–Melotte</span> Irregular galaxy in the Local Group

The Wolf–Lundmark–Melotte (WLM) is a barred irregular galaxy discovered in 1909 by Max Wolf, located on the outer edges of the Local Group. The discovery of the nature of the galaxy was accredited to Knut Lundmark and Philibert Jacques Melotte in 1926. It is in the constellation Cetus.

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

The Tucana Dwarf Galaxy is a dwarf galaxy in the constellation Tucana. It was discovered in 1990 by R.J. Lavery of Mount Stromlo Observatory. It is composed of very old stars and is very isolated from other galaxies. Its location on the opposite side of the Milky Way from other Local Group galaxies makes it an important object for study.

<span class="mw-page-title-main">Pisces Dwarf</span>

The Pisces Dwarf, also known as Pisces I, is an irregular dwarf galaxy that is part of the Local Group. The galaxy, taking its name from the constellation Pisces where it appears, is suspected of being a satellite galaxy of the Triangulum Galaxy (M33). It displays a blueshift, as it is approaching the Milky Way at 287 km/s. It may be transition-type galaxy, somewhere between dwarf spheroidal and dwarf irregular. Alternatively, it may be a rare, but statistically acceptable, version of one of the two types.

Andromeda IX is a dwarf spheroidal satellite of the Andromeda Galaxy. It was discovered in 2004 by resolved stellar photometry from the Sloan Digital Sky Survey (SDSS), by Zucker et al. (2004). At the time of its discovery, it was the galaxy with the lowest known surface brightness, ΣV ≃ 26.8mags arcsec−2 and the faintest galaxy known from its intrinsic absolute brightness.

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

Andromeda II is a dwarf spheroidal galaxy about 2.22 Mly away in the constellation Pisces. While part of the Local Group, it is not quite clear if it is a satellite of the Andromeda Galaxy or the Triangulum Galaxy.

Andromeda III is a dwarf spheroidal galaxy about 2.44 million light-years away in the constellation Andromeda. It is part of the Local Group and is a satellite galaxy of the Andromeda Galaxy (M31). The galaxy was discovered by Sidney van den Bergh on photographic plates taken in 1970 and 1971.

Andromeda V is a dwarf spheroidal galaxy about 2.52 Mly away in the constellation Andromeda.

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

The Cassiopeia Dwarf (also known as Andromeda VII) is a dwarf spheroidal galaxy about 2.45 Mly away in the constellation Cassiopeia. The Cassiopeia Dwarf is part of the Local Group and a satellite galaxy of the Andromeda Galaxy (M31). In the sky, it appears behind the Milky Way's galactic plane, and so it is reddened by 0.194 magnitudes. With a luminosity of 1.8×107 L☉ and a stellar mass of 19.73×106 M☉, it is the brightest and most massive of the Andromeda Galaxy's dwarf spheroidal galaxy satellites. It also has the highest metallicity out of all of them.

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

Cetus Dwarf is a dwarf spheroidal galaxy. It lies approximately 2.46 Million light-years from Earth. It is an isolated galaxy of the Local Group, which also contains the Milky Way. All of the most readily observable stars in the galaxy are red giants.

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

The Antlia Dwarf is a dwarf spheroidal/irregular galaxy. It lies about 1.3 Mpc from Earth in the constellation Antlia. It is the fourth and faintest member of the nearby Antlia-Sextans Group of galaxies. The galaxy contains stars of all ages, contains significant amounts of gas, and has experienced recent star formation. The Antlia Dwarf is believed to be tidally interacting with the small barred spiral galaxy NGC 3109.

References

  1. 1 2 3 4 5 6 7 8 "NASA/IPAC Extragalactic Database". Results for Andromeda IV. Retrieved 15 March 2007.
  2. ↑ Ferguson; Gallagher; Wyse (2000). "On the nature of Andromeda IV". The Astronomical Journal . 120 (2): 821–832. arXiv: astro-ph/0005015 . Bibcode:2000AJ....120..821F. doi:10.1086/301485. S2CID   17907076.
  3. ↑ Nowakowski, Tomasz (22 December 2015). "Andromeda IV turns out to be a solitary gas-rich dwarf galaxy". physorg. Retrieved 25 December 2015.
  4. ↑ Karachentsev, I. D.; Chengalur, Jayaram. N.; Tully, R. B.; Makarova, L. N.; Sharina, M. E.; Begum, A.; Rizzi, L. (2015). "Andromeda IV, a solitary gas-rich dwarf galaxy". Astronomische Nachrichten. 337 (3): 306–314. arXiv: 1512.05907 . Bibcode:2016AN....337..306K. doi:10.1002/asna.201512354. S2CID   118583814.
  5. ↑ McConnachie, A. W.; Irwin, M. J.; Ferguson, A. M. N.; Ibata, R. A.; Lewis, G. F.; Tanvir, N. (2005). "Distances and metallicities for 17 Local Group galaxies". Monthly Notices of the Royal Astronomical Society . 356 (4): 979–997. arXiv: astro-ph/0410489 . Bibcode:2005MNRAS.356..979M. doi:10.1111/j.1365-2966.2004.08514.x.


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