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NGC 4522 is an edge-on
spiral galaxy
Spiral galaxies form a class of galaxy originally described by Edwin Hubble in his 1936 work ''The Realm of the Nebulae''light-year
A light-year, alternatively spelled light year, is a large unit of length used to express astronomical distances and is equivalent to about 9.46 trillion kilometers (), or 5.88 trillion miles ().One trillion here is taken to be 1012 ...
s away within the Virgo Cluster
The Virgo Cluster is a large cluster of galaxies whose center is 53.8 ± 0.3 Mly (16.5 ± 0.1 Mpc) away in the constellation Virgo. Comprising approximately 1,300 (and possibly up to 2,000) member galaxies, the cluster forms the heart of the lar ...
in the constellation Virgo
Virgo may refer to:
*Virgo (astrology), the sixth astrological sign of the zodiac
*Virgo (constellation), a constellation
*Virgo Cluster, a cluster of galaxies in the constellation Virgo
*Virgo Stellar Stream, remains of a dwarf galaxy
*Virgo Supe ...
. NGC 4522 is losing its molecular gas though ram-pressure stripping
Ram pressure is a pressure exerted on a body moving through a fluid medium, caused by relative bulk motion of the fluid rather than random thermal motion. It causes a drag force to be exerted on the body. Ram pressure is given in tensor form as
...
as it plows though the cluster
may refer to:
Science and technology Astronomy
* Cluster (spacecraft), constellation of four European Space Agency spacecraft
* Asteroid cluster, a small asteroid family
* Cluster II (spacecraft), a European Space Agency mission to study t ...
at a speed of more than 10 million kilometres per hour. The galaxy was discovered by astronomer John Herschel
Sir John Frederick William Herschel, 1st Baronet (; 7 March 1792 – 11 May 1871) was an English polymath active as a mathematician, astronomer, chemist, inventor, experimental photographer who invented the blueprint and did botanical wor ...
on January 18, 1828.
Ram-pressure stripping
The selectively disturbedinterstellar medium
In astronomy, the interstellar medium is the matter and radiation that exist in the space between the star systems in a galaxy. This matter includes gas in ionic, atomic, and molecular form, as well as dust and cosmic rays. It fills interstella ...
(ISM) of NGC 4522, together with a normal-appearing stellar disk, strongly suggest that the galaxy is undergoing ram-pressure stripping
Ram pressure is a pressure exerted on a body moving through a fluid medium, caused by relative bulk motion of the fluid rather than random thermal motion. It causes a drag force to be exerted on the body. Ram pressure is given in tensor form as
...
caused by an interaction between the intracluster medium
In astronomy, the intracluster medium (ICM) is the superheated plasma that permeates a galaxy cluster. The gas consists mainly of ionized hydrogen and helium and accounts for most of the baryonic material in galaxy clusters. The ICM is heated to t ...
(ICM) of the surrounding Virgo Cluster
The Virgo Cluster is a large cluster of galaxies whose center is 53.8 ± 0.3 Mly (16.5 ± 0.1 Mpc) away in the constellation Virgo. Comprising approximately 1,300 (and possibly up to 2,000) member galaxies, the cluster forms the heart of the lar ...
with the ISM of the galaxy itself.
However at NGC 4522's projected distance from Messier 87
Messier 87 (also known as Virgo A or NGC 4486, generally abbreviated to M87) is a supergiant elliptical galaxy with several trillion stars in the constellation Virgo. One of the largest and most massive galaxies in the local uni ...
(~1 Mpc), and assumption of a static smooth ICM and other "standard values", the force of the ram-pressure stripping exerted at the galaxy's location appears to be an order of magnitude less than needed to cause the observed truncation of the galaxy's gas disk. Despite this, NGC 4522 may have recently passed through a region of enhanced ICM density. Possibly, the infall of the Messier 49
Messier 49 (also known as M49 or NGC 4472) is a giant elliptical galaxy about away in the equatorial constellation of Virgo. This galaxy was discovered by astronomer Charles Messier in 1777.
As an elliptical galaxy, Messier 49 has the physica ...
group into the Virgo Cluster has stirred up the ICM of the cluster, locally enhancing the ram pressure exerted on NGC 4522.
Features
In NGC 4522, there are several features that have been suggested to be attributes of ram-pressure stripping. The northeast region of NGC 4522, contains a large, continuousdust lane
A dust lane consists of a relatively dense, obscuring clouds of interstellar dust, observed as a dark swath against the background of a brighter object(s), especially a galaxy. These dust lanes can usually be seen in spiral galaxies, such as ...
that curves out of the disk of the galaxy that is known as "The dust upturn”. The region also contains a wide lane of stars, including many young blue stars that has been named "The stellar upturn". At the top of the upturn, there are a couple of distinct HII regions
An H II region or HII region is a region of interstellar atomic hydrogen that is ionized. It is typically in a molecular cloud of partially ionized gas in which star formation has recently taken place, with a size ranging from one to hundred ...
.
The southwest region features a number of decoupled extraplanar dust clouds and an arm structure containing a number of HII regions and groupings of bright young blue stars.
Star formation
As a consequence ofram-pressure stripping
Ram pressure is a pressure exerted on a body moving through a fluid medium, caused by relative bulk motion of the fluid rather than random thermal motion. It causes a drag force to be exerted on the body. Ram pressure is given in tensor form as
...
, NGC 4522 has a shrunken star forming disk with an enhanced rate of star formation in the inner regions while there is lack of star formation
Star formation is the process by which dense regions within molecular clouds in The "medium" is present further soon.-->interstellar space
in the outer disk.
Some of the newly formed star
A star is an astronomical object comprising a luminous spheroid of plasma (physics), plasma held together by its gravity. The List of nearest stars and brown dwarfs, nearest star to Earth is the Sun. Many other stars are visible to the naked ...
s in NGC 4522 are forming in H II region
An H II region or HII region is a region of interstellar atomic hydrogen that is ionized. It is typically in a molecular cloud of partially ionized gas in which star formation has recently taken place, with a size ranging from one to hundreds ...
s in filaments of stripped gas rising from the star forming disk of the galaxy. These stars may enter the halo of NGC 4522 or escape into intergalactic space
Outer space, commonly shortened to space, is the expanse that exists beyond Earth and its atmosphere and between celestial bodies. Outer space is not completely empty—it is a near-perfect vacuum containing a low density of particles, predo ...
.
See also
* List of NGC objects (4001–5000) * NGC 4402 *ESO 137-001
ESO 137-001 is a barred spiral galaxy located in the constellation Triangulum Australe and in the cluster Abell 3627. As the galaxy moves to the center of the cluster at 1900 km/s, it is stripped by hot gas, thus creating a 260,000 light-y ...
References
External links
{{DEFAULTSORT:NGC 4522 Virgo (constellation) Spiral galaxies 4522 41729 7711 Astronomical objects discovered in 1828 Virgo Cluster Discoveries by John Herschel