TON 618 | |
---|---|
Observation data (Epoch J2000.0) | |
Constellation | Canes Venatici |
Right ascension | 12h 28m 24.9s [1] |
Declination | +31° 28′ 38″ [1] |
Redshift | 2.219 [1] |
Distance | |
Type | Quasar [1] |
Apparent magnitude (V) | 15.9 [1] |
Notable features | Hyperluminous quasar in a Lyman-alpha blob |
Other designations | |
FBQS J122824.9+312837, B2 1225+31, QSO 1228+3128, 7C 1225+3145, CSO 140, 2E 2728, Gaia DR1 4015522739308729728 [1] | |
See also: Quasar, List of quasars |
TON 618 (abbreviation of Tonantzintla 618) is a hyperluminous, broad-absorption-line, radio-loud quasar, and Lyman-alpha blob [2] located near the border of the constellations Canes Venatici and Coma Berenices, with the projected comoving distance of approximately 18.2 billion light-years from Earth. [a] It possesses one of the most massive black holes ever found, at 40.7 billion M☉. [3]
As quasars were not recognized until 1963, [4] the nature of this object was unknown when it was first noted in a 1957 survey of faint blue stars (mainly white dwarfs) that lie away from the plane of the Milky Way. On photographic plates taken with the 0.7 m Schmidt telescope at the Tonantzintla Observatory in Mexico, it appeared "decidedly violet" and was listed by the Mexican astronomers Braulio Iriarte and Enrique Chavira as entry number 618 in the Tonantzintla Catalogue. [5]
In 1970, a radio survey at Bologna in Italy discovered radio emissions from TON 618, indicating that it was a quasar. [6] Marie-Helene Ulrich then obtained optical spectra of TON 618 at the McDonald Observatory which showed emission lines typical of a quasar. From the high redshift of the lines Ulrich deduced that TON 618 was very distant, and hence was one of the most luminous quasars known. [7]
As a quasar, TON 618 is believed to be the active galactic nucleus at the center of a galaxy, the engine of which is a supermassive black hole feeding on intensely hot gas and matter in an accretion disc. Given its observed redshift of 2.219, the light travel time of TON 618 is estimated to be approximately 10.8 billion years. Due to the brilliance of the central quasar, the surrounding galaxy is outshone by it and hence is not visible from Earth. With an absolute magnitude of −30.7, it shines with a luminosity of 4×1040 watts, or as brilliantly as 140 trillion times that of the Sun, making it one of the brightest objects in the known Universe. [1]
Like other quasars, TON 618 has a spectrum containing emission lines from cooler gas much further out than the accretion disc, in the broad-line region. The size of the broad-line region can be calculated from the brightness of the quasar radiation that is lighting it up. [8] Shemmer and coauthors used both NV and CIV emission lines in order to calculate the widths of the Hβ spectral line of at least 29 quasars, including TON 618, as a direct measurement of their accretion rates and hence the mass of the central black hole. [9]
The emission lines in the spectrum of TON 618 have been found to be unusually wide, [7] indicating that the gas is travelling very fast; the full width half maxima of TON 618 has been the largest of the 29 quasars, with hints of 10,500 km/s speeds of infalling material by a direct measure of the Hβ spectral line, indication of a very strong gravitational force. [9] From this, the mass of the central black hole of TON 618 has been estimated to be at 66 billion solar masses. [9] This is considered one of the highest masses ever recorded for such an object; higher than the mass of all the stars in the Milky Way galaxy combined, which is 64 billion solar masses, [10] and 15,300 times more massive than Sagittarius A*, the Milky Way's central black hole. With such high mass, TON 618 may fall into a proposed new classification of ultramassive black holes. [11] [12] A black hole of this mass has a Schwarzschild radius of 1,300 AU (about 390 billion km or 0.04 ly in diameter) which is more than 40 times the distance from Neptune to the Sun, and its event horizon is large enough to fit over 30 solar systems inside of it.
A more recent measurement in 2019 by Ge and colleagues which utilizes the C IV emission line, an alternative spectral line to Hβ, using the same data reproduced by the earlier paper by Shemmer found a lower relative velocity of the surrounding gas of 2,761 ± 423 km/s, which indicate a lower mass for the central black hole at 40.7 billion solar masses, consequentially lower than the previous estimate. [3]
The nature of TON 618 as a Lyman-alpha emitter has been well documented since at least the 1980s. [13] Lyman-alpha emitters are characterized by their significant emission of the Lyman-alpha line, an ultraviolet wavelength emitted by neutral hydrogen. Such objects, however, have been very difficult to study due to the Lyman-alpha line being strongly absorbed by air in the Earth's atmosphere, limiting study of Lyman-alpha emitters to those objects with high redshifts. TON 618, with its luminous emission of Lyman-alpha radiation along with its high redshift, has made it one of the most important objects in the study of the Lyman-alpha forest. [14]
Observations made by the Atacama Large Millimeter Array (ALMA) in 2021 revealed the apparent source of the Lyman-alpha radiation of TON 618: an enormous cloud of gas surrounding the quasar and its host galaxy. [2] This would make it a Lyman-alpha blob (LAB), one of the largest such objects yet known.
LABs are huge collections of gases, or nebulae, that are also classified as Lyman-alpha emitters. These enormous, galaxy-sized clouds are some of the largest nebulae known to exist, with some identified LABs in the 2000s reaching sizes of at least hundreds of thousands of light-years across. [15]
In the case of TON 618, the enormous Lyman-alpha nebula surrounding it has the diameter of at least 100 kiloparsecs (330,000 light-years), twice the size of the Milky Way. [2] The nebula consists of two parts: an inner molecular outflow and an extensive cold molecular gas in its circumgalactic medium, each having the mass of 50 billion M☉, [2] with both of them being aligned to the radio jet produced by the central quasar. The extreme radiation from TON 618 excites the hydrogen in the nebula so much that it causes it to glow brightly in the Lyman-alpha line, consistent with the observations of other LABs driven by their inner galaxies. [16] Since both quasars and LABs are precursors of modern-day galaxies, the observation on TON 618 and its enormous LAB gave insight to the processes that drive the evolution of massive galaxies, [2] in particular probing their ionization and early development.
A quasar is an extremely luminous active galactic nucleus (AGN). It is sometimes known as a quasi-stellar object, abbreviated QSO. The emission from an AGN is powered by accretion onto a supermassive black hole with a mass ranging from millions to tens of billions of solar masses, surrounded by a gaseous accretion disc. Gas in the disc falling towards the black hole heats up and releases energy in the form of electromagnetic radiation. The radiant energy of quasars is enormous; the most powerful quasars have luminosities thousands of times greater than that of a galaxy such as the Milky Way. Quasars are usually categorized as a subclass of the more general category of AGN. The redshifts of quasars are of cosmological origin.
An active galactic nucleus (AGN) is a compact region at the center of a galaxy that emits a significant amount of energy across the electromagnetic spectrum, with characteristics indicating that this luminosity is not produced by the stars. Such excess, non-stellar emissions have been observed in the radio, microwave, infrared, optical, ultra-violet, X-ray and gamma ray wavebands. A galaxy hosting an AGN is called an active galaxy. The non-stellar radiation from an AGN is theorized to result from the accretion of matter by a supermassive black hole at the center of its host galaxy.
3C 273 is a quasar located at the center of a giant elliptical galaxy in the constellation of Virgo. It was the first quasar ever to be identified and is the visually brightest quasar in the sky as seen from Earth, with an apparent visual magnitude of 12.9. The derived distance to this object is 749 megaparsecs. The mass of its central supermassive black hole is approximately 886 million times the mass of the Sun.
Seyfert galaxies are one of the two largest groups of active galaxies, along with quasar host galaxies. They have quasar-like nuclei with very high surface brightnesses whose spectra reveal strong, high-ionisation emission lines, but unlike quasars, their host galaxies are clearly detectable.
Messier 87 is a supergiant elliptical galaxy in the constellation Virgo that contains several trillion stars. One of the largest and most massive galaxies in the local universe, it has a large population of globular clusters—about 15,000 compared with the 150–200 orbiting the Milky Way—and a jet of energetic plasma that originates at the core and extends at least 1,500 parsecs, traveling at a relativistic speed. It is one of the brightest radio sources in the sky and a popular target for both amateur and professional astronomers.
A supermassive black hole 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 (M☉). Black holes are a class of astronomical objects that have undergone gravitational collapse, leaving behind spheroidal regions of space from which nothing can escape, including light. Observational evidence indicates that almost every large galaxy has a supermassive black hole at its center. For example, the Milky Way galaxy has a supermassive black hole at its center, corresponding to the radio source Sagittarius A*. Accretion of interstellar gas onto supermassive black holes is the process responsible for powering active galactic nuclei (AGNs) and quasars.
In the fields of Big Bang theory and cosmology, reionization is the process that caused electrically neutral atoms in the universe to reionize after the lapse of the "dark ages".
In astronomy, a Lyman-alpha blob (LAB) is a huge concentration of a gas emitting the Lyman-alpha emission line. LABs are some of the largest known individual objects in the Universe. Some of these gaseous structures are more than 400,000 light years across. So far they have only been found in the high-redshift universe because of the ultraviolet nature of the Lyman-alpha emission line. Since Earth's atmosphere is very effective at filtering out UV photons, the Lyman-alpha photons must be redshifted in order to be transmitted through the atmosphere.
APM 08279+5255 is a very distant, broad absorption line quasar located in the constellation Lynx. It is magnified and split into multiple images by the gravitational lensing effect of a foreground galaxy through which its light passes. It appears to be a giant elliptical galaxy with a supermassive black hole and associated accretion disk. It possesses large regions of hot dust and molecular gas, as well as regions with starburst activity.
A Lyman-alpha emitter (LAE) is a type of distant galaxy that emits Lyman-alpha radiation from neutral hydrogen.
A Pea galaxy, also referred to as a Pea or Green Pea, might be a type of luminous blue compact galaxy that is undergoing very high rates of star formation. Pea galaxies are so-named because of their small size and greenish appearance in the images taken by the Sloan Digital Sky Survey (SDSS).
Green bean galaxies (GBGs) are very rare astronomical objects that are thought to be quasar ionization echos. They were discovered by Mischa Schirmer and colleagues R. Diaz, K. Holhjem, N.A. Levenson, and C. Winge. The authors report the discovery of a sample of Seyfert-2 galaxies with ultra-luminous galaxy-wide narrow-line regions (NLRs) at redshifts z=0.2-0.6.
Lyman-alpha blob 1 (LAB-1) is a giant cosmic cloud of gas located in the constellation of Aquarius, approximately 11.5 billion light-years from Earth with a redshift (z) of 3.09. It was discovered unexpectedly in 2000 by Charles Steidel and colleagues, who were surveying for high-redshift galaxies using the 200 inch Hale Telescope at the Palomar Observatory. The researchers had been investigating the abundance of galaxies in the young Universe when they came across two objects which would become known as Lyman-alpha blobs—huge concentrations of gases emitting the Lyman-alpha emission line of hydrogen.
EGS-zs8-1 is a high-redshift Lyman-break galaxy found at the northern constellation of Boötes. In May 2015, EGS-zs8-1 had the highest spectroscopic redshift of any known galaxy, meaning EGS-zs8-1 was the most distant and the oldest galaxy observed. In July 2015, EGS-zs8-1 was surpassed by EGSY8p7 (EGSY-2008532660).
WISE J224607.57−052635.0 (or W2246−0526 for short) is an extremely luminous infrared galaxy (ELIRG) which, in 2015, was announced as the most luminous known galaxy in the observable universe. The brightness of this galaxy is 350 trillion times that of the Sun (349×1012L☉). The merger of smaller nearby galaxies may be contributing to its brightness. The light is generated by a quasar 10 billion times the mass of the Sun. The high energy optical light and ultraviolet light emitted by the accretion disc around the quasar's supermassive black hole is absorbed by the galaxy's dust and re-emitted in the infrared. The galaxy releases 10,000 times more energy than the Milky Way galaxy, although WISE J224607.57–052635.0 is the smaller of the two. WISE J224607.57–052635.0 has a light-travel distance of 12.5 billion light years from it to Earth. The galaxy was discovered using the Wide-field Infrared Survey Explorer.
The Teacup galaxy, also known as the Teacup AGN or SDSS J1430+1339 is a low redshift type 2 quasar, showing an extended loop of ionized gas resembling a handle of a teacup, which was discovered by volunteers of the Galaxy Zoo project and labeled as a Voorwerpje.
SBS 1425+606 also known as HS 1425+6039 and QSO B1425+606, is a quasar located in the constellation Ursa Major. Its redshift is 3.197157, putting the object at a light travel time distance of 11.4 billion light years.
PG 0844+349, also known as TON 951, is a galaxy in the southern constellation Lynx, near the border of Cancer. Its redshift is 0.064000, putting the galaxy at 849 million light-years away from Earth.
UM 287 known as PHL 868 and LBQS 0049+0045, is a quasar located in the Cetus constellation. Its redshift is 2.267134 estimating the object to be located 10.9 billion light-years away from Earth.