HE0450-2958 is an unusual quasar. It has been called the "naked quasar" and the "quasar without a home" because it appears to lack a host galaxy. It is estimated to lie approximately one billion

parsec The parsec (symbol: pc) is a unit of length used to measure the large distances to astronomical objects outside the Solar System, approximately equal to or (au), i.e. . The parsec unit is obtained by the use of parallax and trigonometry, an ...

s away.

History

A team of researchers led by Pierre Magain of the

University of Liège The University of Liège (french: Université de Liège), or ULiège, is a major public university of the French Community of Belgium based in Liège, Wallonia, Belgium. Its official language is French. As of 2020, ULiège is ranked in the 301 ...

, Belgium announced their findings in the September 14, 2005 issue of the journal ''

Nature Nature, in the broadest sense, is the physical world or universe. "Nature" can refer to the phenomena of the physical world, and also to life in general. The study of nature is a large, if not the only, part of science. Although humans are ...

''.Magain, P. et al. (2005)
Discovery of a bright quasar without a massive host galaxy
''Nature'', 437, 381 The quasar lies close in the sky to a disturbed, starburst galaxy (see figure, upper left). However, no galaxy was seen around the quasar itself (figure, middle), leading the authors to speculate

One might suggest that the host galaxy has disappeared from our view as a result of the collision hich formed the disturbed galaxy but it is hard to imagine how the complete disruption of a galaxy could happen.

In order for the quasar's host galaxy to have escaped detection, Magain et al. estimated that it would need to be approximately five magnitudes (100 times) dimmer than expected for such a quasar, or to have a radius of 300 light-years or less (typical quasars are embedded in galaxies 5000 to 50,000 light-years across). Shortly after Magain et al.'s paper was published, three theoretical papers appeared, all in the week of November 6, 2005, which claimed to explain the peculiar properties of this object. Two of the papers—from groups in

Cambridge, Massachusetts Cambridge ( ) is a city in Middlesex County, Massachusetts, United States. As part of the Boston metropolitan area, the cities population of the 2020 U.S. census was 118,403, making it the fourth most populous city in the state, behind Boston ...

and

Cambridge, England Cambridge ( ) is a university city and the county town in Cambridgeshire, England. It is located on the River Cam approximately north of London. As of the 2021 United Kingdom census, the population of Cambridge was 145,700. Cambridge became ...

—suggested that the quasar was a

supermassive black hole A supermassive black hole (SMBH or sometimes SBH) is the largest type of black hole, with its mass being on the order of hundreds of thousands, or millions to billions of times the mass of the Sun (). Black holes are a class of astronomical ob ...

that had been ejected from the center of the nearby, disturbed galaxy, either by gravitational radiation recoil or by an interaction involving three black holes. The ejection velocity would have to be approximately 1000 km/s in order to place the quasar so far from its original host galaxy. The third paper, from a team led by

David Merritt David Roy Merritt (born November 16, 1955 in Los Angeles) is an American astrophysicist. Until 2017 he was a professor at the Rochester Institute of Technology in Rochester, New York, Rochester, New York (state), New York. He received in 1982 his ...

, critically examined the ejection hypothesis and concluded that it could not be correct. The two main arguments were: (1) The quasar spectrum reveals it to be a narrow-line Seyfert 1 galaxy. NLS1's are believed to have abnormally small black holes; since black hole size is strongly correlated with galaxy size, the host galaxy of the quasar should also be abnormally small, explaining why it had not been detected by Magain et al. (2) The quasar spectrum also reveals the presence of a classic, narrow emission line region (NLR). The gas producing the narrow lines lies roughly a thousand light-years from the black hole, and such gas could not remain bound to the black hole following a kick large enough to remove it from its host galaxy. These authors concluded that the "naked" quasar was in fact a perfectly normal, narrow-line Seyfert galaxy that happened to lie close on the sky to a disturbed galaxy. A number of scientific studies since 2005 have supported this conclusion. (1) Kim et al. (2006) made a more careful attempt to find the quasar's host galaxy. They concluded that it was impossible to rule out the presence of a galaxy given the confusing light from the quasar. (2) Zhou et al. (2007) observed the

X-ray An X-ray, or, much less commonly, X-radiation, is a penetrating form of high-energy electromagnetic radiation. Most X-rays have a wavelength ranging from 10 picometers to 10 nanometers, corresponding to frequencies in the range 30&nb ...

emission from the quasar and used it to estimate the mass of the black hole. They confirmed a small mass for the black hole, implying an even fainter host galaxy than predicted by Merritt et al. (3) Feain et al. (2007) detected radio emission from the quasar, which they interpreted as indicating ongoing star formation, which "contradicts any suggestion that this is a 'naked' quasar'". The current scientific consensus is that HE0450-2958 probably does have a host galaxy but that it is difficult to see behind the bright quasar light. Recently, the consensus has been questioned after a European Southern Observatory study. a study in 2010 discovered a "blob" of emmision near the quasar. this blob is thought to be the disterbed and compact host galaxy for the quazar.

References

External links

Black Hole in Search of a Home
(ESO)
Image HE0450-2958

Black Hole Caught Zapping Galaxy into Existence?

{{DEFAULTSORT:HE0450-2958 Quasars Supermassive black holes Caelum 75249 Dark galaxies 20050914

History

See also

References

External links