Radiation astronomy/High-velocity galaxies

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The irregular galaxy NGC 1427A is passing through the Fornax cluster at nearly 600 kilometers per second (400 miles per second). Credit: NASA, ESA, and The Hubble Heritage Team (STScI/AURA).{{free media}}

"The irregular galaxy NGC 1427A is a spectacular example of the resulting stellar rumble. Under the gravitational grasp of a large gang of galaxies, called the Fornax cluster, the small bluish galaxy is plunging headlong into the group at 600 kilometers per second or nearly 400 miles per second."[1]

"Galaxy clusters, like the Fornax cluster, contain hundreds or even thousands of individual galaxies. Within the Fornax cluster, there is a considerable amount of gas lying between the galaxies. When the gas within NGC 1427A collides with the Fornax gas, it is compressed to the point that it starts to collapse under its own gravity. This leads to formation of the myriad of new stars seen across NGC 1427A, which give the galaxy an overall arrowhead shape that appears to point in the direction of the galaxy's high-velocity motion."[1]

Active galaxies[edit | edit source]

NGC 1068 is a spiral, Seyfert 2, galaxy. Credit: Judy Schmidt.{{free media}}

The majority of active galaxies are very distant and show large Doppler shifts suggesting that active galaxies occurred in the early Universe and, due to cosmic inflation, are receding away from the Milky Way at very high speeds, where Quasars are the furthest active galaxies, some of them being observed at distances 12 billion light years away and Seyfert galaxies are much closer than quasars.[2][3]

Galaxy harassment[edit | edit source]

This image from the NASA/ESA Hubble Space Telescope shows the unusual galaxy IRAS 06076-2139, found in the constellation Lepus (The Hare). Credit: ESA/Hubble & NASA.{{free media}}

Galaxy harassment is a type of interaction between a low-luminosity galaxy and a brighter one that takes place within rich galaxy clusters, such as the Virgo Cluster and Coma Cluster, where galaxies are moving at high relative speeds and suffering frequent encounters with other systems of the cluster by the high galactic density of the latter, where computer simulations suggest the interactions convert the affected galaxy disks into disturbed barred spiral galaxies and produce starbursts followed by, if more encounters occur, loss of angular momentum and heating of their gas resulting in the conversion of (late type) low-luminosity spiral galaxies into dwarf spheroidals and dwarf ellipticals.[4]

Hubble’s Wide Field Camera 3 (WFC3) and Advanced Camera for Surveys (ACS) instruments observed the galaxy from a distance of 500 million light-years. This particular object stands out from the crowd by actually being composed of two separate galaxies rushing past each other at about 2 million kilometres per hour. This speed is most likely too fast for them to merge and form a single galaxy. However, because of their small separation of only about 20 000 light-years, the galaxies will distort one another through the force of gravity while passing each other, changing their structures on a grand scale. Such galactic interactions are a common sight for Hubble, and have long been a field of study for astronomers. The intriguing behaviours of interacting galaxies take many forms; galactic cannibalism, galaxy harassment and even galaxy collisions.

Quasars[edit | edit source]

Sloan Digital Sky Survey (SDSS) image of quasar 3C 273, illustrating the object's star-like appearance. The quasar's jet can be seen extending downward and to the right from the quasar. Credit: Sloan Digital Sky Survey.{{free media}}
Hubble Space Telescope images of quasar 3C 273. At right, a coronagraph is used to block the quasar's light, making it easier to detect the surrounding host galaxy. Credit: WFPC2 image: NASA and J. Bahcall (IAS). Credit for ACS image: NASA, A. Martel (JHU), H. Ford (JHU), M. Clampin (STScI), G. Hartig (STScI), G. Illingworth (UCO/Lick Observatory), the ACS Science Team and ESA.{{free media}}
Picture shows a cosmic mirage known as the Einstein Cross. Four apparent images are actually from the same quasar. Credit: ESA/Hubble & NASA.{{free media}}
Cloud of gas around the distant quasar SDSS J102009.99+104002.7, taken by Multi-unit spectroscopic explorer (MUSE).[5] Credit: ESO/Arrigoni Battaia et al.{{free media}}

Def. an "extragalactic object, starlike in appearance,[6] that [is among] the most luminous and [(putatively)] the most distant objects in the universe"[6] is called a quasar.

The power radiated by quasars is enormous: the most powerful quasars have luminosities thousands of times greater than a galaxy such as the Milky Way.[7]

High-resolution images of quasars, particularly from the Hubble Space Telescope, have demonstrated that quasars occur in the centers of galaxies, and that some host-galaxies are strongly interacting or merging galaxies.[8]

The peak epoch of quasar activity was approximately 10 billion years ago.[9] As of 2017, the most distant known quasar is ULAS J1342+0928 at redshift z = 7.54; light observed from this quasar was emitted when the universe was only 690 million years old. The supermassive black hole in this quasar, estimated at 800 million solar masses, is the most distant black hole identified to date.[10][11][12]

"So far, the clumsily long name 'quasi-stellar radio sources' is used to describe these objects. Because the nature of these objects is entirely unknown, it is hard to prepare a short, appropriate nomenclature for them so that their essential properties are obvious from their name. For convenience, the abbreviated form 'quasar' will be used throughout this paper."[13]

Blazars[edit | edit source]

Sloan Digital Sky Survey image is of blazar Markarian 421, illustrating the bright nucleus and elliptical host galaxy. Credit: Sloan Digital Sky Survey.{{free media}}

Def. a "very compact quasar, associated with [a supermassive black hole at the center][14] of an active galaxy"[15] or an "object which is either [an optically violent variable quasar or a BL Lac object][16] or which has properties of both"[15] is called a blazar.

Relativistic beaming of electromagnetic radiation from the jet makes blazars appear much brighter than they would be if the jet were pointed in a direction away from the Earth.[17]

In visible-wavelength images, most blazars appear compact and pointlike, but high-resolution images reveal that they are located at the centers of elliptical galaxies.[18]

In July 2018, the IceCube Neutrino Observatory announced that they have traced a neutrino that hit their Antarctica-based detector in September 2017 back to its point of origin in a blazar 3.7 billion light-years away, which is the first time that a neutrino detector has been used to locate an object in space.[19][20][21]

BL Lacertae objects[edit | edit source]

The optical spectrum is for the BL Lac object PG 1553+11. Credit: Rfalomo.{{free media}}
The BL Lac object H 0323+022 (z=0.147) is imaged at ESO NTT (R filter). The host galaxy and close companions are visible. Credit: Renato Falomo.{{free media}}

Def. "a type of active galaxy with an active galactic nucleus (AGN), named after its prototype, BL Lacertae"[22] is called a BL Lac object, or BL Lacertae object.

In contrast to other types of active galactic nuclei, BL Lacs are characterized by rapid and large-amplitude flux variability and significant optical polarization.[23] Because of these properties, the prototype of the class (BL Lacertae, BL Lac) was originally thought to be a variable star, but when compared to the more luminous active nuclei (quasars) with strong emission lines, BL Lac objects have spectra dominated by a relatively featureless non-thermal emission continuum over the entire electromagnetic range.[24] This lack of spectral lines historically hindered BL Lac's identification of their nature and proved to be a hurdle in the determination of their distance.[24]

All known BL Lacs are associated with core dominated radio sources, many of them exhibiting superluminal motion.[25]

OVV quasars are generally more luminous and have stronger emission lines than BL Lac objects.[26]

Seyfert galaxies[edit | edit source]

NGC 6814 is a Type I Seyfert galaxy with a highly variable source of X-ray radiation.[27] Credit: ESA/Hubble & NASA Acknowledgement: Judy Schmidt (Geckzilla).{{free media}}
Messier 94 is a galaxy with a Seyfert-like low-ionization nuclear emission-line region (LINER) nucleus. Credit: R Jay Gabany (Blackbird Obs.).{{free media}}
NGC 7469 (upper right) is a Type 1.2 Seyfert galaxy, IC 5283 is center left, by Hubble Space Telescope. Credit: NASA/JPL-Caltech.{{free media}}
NGC 1275 is a type 1.5 Seyfert galaxy Credit: NASA, ESA, and the Hubble Heritage (STScI/AURA)-ESA/Hubble Collaboration.{{free media}}
NGC 1365 is a Type 1.8 Seyfert galaxy. Credit: European Southern Observatory (ESO).{{free media}}
NGC 1161 is a Type 1.9 Seyfert galaxy. Credit: Sloan Digital Sky Survey (SDSS).{{free media}}
The Circinus Galaxy is a Type II Seyfert galaxy. Credit: NASA, Andrew S. Wilson (University of Maryland); Patrick L. Shopbell (Caltech); Chris Simpson (Subaru Telescope); Thaisa Storchi-Bergmann and F. K. B. Barbosa (UFRGS, Brazil); and Martin J. Ward (University of Leicester, U.K.).{{free media}}

Seyfert galaxies are one of the two largest groups of active galaxies, along with quasars, and have quasar-like nuclei (very luminous, distant and bright sources of electromagnetic radiation) with very high surface brightnesses whose spectra reveal strong, high-ionisation emission lines,[28] but unlike quasars, their host galaxies are clearly detectable.[29]

Seyfert galaxies account for about 10% of all galaxies.[30]

Seen in visible light, most Seyfert galaxies look like normal spiral galaxies, but when studied under other wavelengths, it becomes clear that the luminosity of their cores is of comparable intensity to the luminosity of whole galaxies the size of the Milky Way.[31]

Seyfert galaxies are named after Carl Keenan Seyfert, who first described this class in 1943.[32]

Very few Seyfert galaxies are ellipticals, most of them being spiral or barred spiral galaxies.[33]

A simple division into types I and II has been devised, with the classes depending on the relative width of their emission lines.[34]

It has been later noticed that some Seyfert nuclei show intermediate properties, resulting in their being further subclassified into types 1.2, 1.5, 1.8 and 1.9.[35][36]

Several dozen galaxies exhibiting the Seyfert phenomenon exist in the close vicinity (≈27 Mpc) of our own galaxy.[30] Seyfert galaxies form a substantial fraction of the galaxies appearing in the Markarian catalog, a list of galaxies displaying an ultraviolet excess in their nuclei.[37]

In a typical Seyfert galaxy, the nuclear source emits at visible wavelengths an amount of radiation comparable to that of the whole galaxy's constituent stars, while in a quasar, the nuclear source is brighter than the constituent stars by at least a factor of 100.[28][38]

Type I Seyferts are very bright sources of ultraviolet light and X-rays in addition to the visible light coming from their cores, with two sets of emission lines on their spectra: narrow lines with widths (measured in velocity units) of several hundred km/s, and broad lines with widths up to 104 km/s.[39]

The broad line emission region, RBLR, can be estimated from the time delay corresponding to the time taken by light to travel from the continuum source to the line-emitting gas.[40]

Type II Seyfert galaxies have the characteristic bright core, as well as appearing bright when viewed at infrared wavelengths.[41] Their spectra contain narrow lines associated with forbidden transitions, and broad lines associated with allowed strong dipole or intercombination transitions.[42]

The notations Seyfert 1.5, 1.8 and 1.9, the subclasses are based on the optical appearance of the spectrum, with the numerically larger subclasses having weaker broad-line components relative to the narrow lines.[43]

In Type 1.5, the strength of the Hα and Hβ lines are comparable.[44]

The narrow line Seyfert I galaxies (NLSy1) have been subject to extensive research in recent years.[45]

Narrow Line Seyfert galaxies[edit | edit source]

This is a Hubble image of NGC 4051. Credit: Fabian RRRR.{{free media}}
Red/Green/Blue image is of the galaxy NGC 4051 by the earthbound Liverpool Telescope. Credit: Göran Nilsson & The Liverpool Telescope.{{free media}}
NGC 4051 is imaged by GALEX. Credit: NASA, GALEX, WikiSky.{{free media}}
Quasar HE0450-2958 is imaged by the Hubble Space Telescope near the center. Credit: NASA, ESA, ESO, F. Courbin (Ecole Polytechnique Federale de Lausanne, Switzerland) and P. Magain (Universite de Liege, Belgium).{{free media}}
The "quasar without a home" is shown. Credit: ESO.{{free media}}

NGC 4051 is an intermediate spiral galaxy in the constellation of Ursa Major.[46] It was discovered on 6 February 1788 by John Herschel.[47]

NGC 4051, a narrow-line Seyfert 1 galaxy, contains a supermassive black hole with a mass of 1.73 million solar masses.[48] This galaxy was studied by the Multicolor Active Galactic Nuclei Monitoring 2m telescope.[49] Several supernovae have been discovered in NGC 4051: SN 1983I, SN 2010br, and SN 2003ie.[50]

The galaxy is a Seyfert galaxy that emits bright X-rays. However, in early 1998 the X-ray emission ceased as observed in by the Beppo-SAX satellite.[51]

NGC 4051 is a member of the Ursa Major Cluster.[52][53][54]

The second image down on the left is a quasar near the center of the image with no obvious host galaxy seen, but near the top of the image is a strongly disturbed and star-forming galaxy, the Starburst galaxy, and near the quasar is a blob of gas that is apparently being ionized by the quasar's radiation.[55]

"One might suggest that the host galaxy has disappeared from our view as a result of the collision [which formed the disturbed galaxy], but it is hard to imagine how the complete disruption of a galaxy could happen."[55]

A three-body kick to a bright quasar out of its galaxy during a merger is one theory.[56]

Possible evidence for the ejection of a supermassive black hole from an ongoing merger of galaxies is presented.[57]

The two main arguments against the ejection hypothesis were:[58]

  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.

The "naked" quasar is in fact a perfectly normal, narrow-line Seyfert galaxy that happened to lie close on the sky to a disturbed galaxy.[58]

A more careful attempt to find the quasar's host galaxy concluded that it was impossible to rule out the presence of a galaxy given the confusing light from the quasar.[59]

The X-ray emission observed from the quasar has been used to estimate the mass of the black hole confirming a small mass for the black hole, implying an even fainter host galaxy than predicted[58].[60]

Radio emission detected from the quasar may indicate ongoing star formation, which "contradicts any suggestion that this is a 'naked' quasar'".[61]

Quasar induced galaxy formation may be a new paradigm.[62]

A1689-zD1[edit | edit source]

Location of A1689-zD1 in infrared and visible light by Hubble Space Telescope and Spitzer Space Telescope. Credit: NASA, ESA, L. Bradley (Johns Hopkins University), R. Bouwens (University of California in Santa Cruz); H. Ford (Johns Hopkins University) and G. Illingworth (University of California in Santa Cruz).{{free media}}

A1689-zD1 is a galaxy in the Virgo constellation cluster. It was a candidate for the most distant and therefore earliest observed galaxy discovered, based on a photometric redshift.[63][64]

If the redshift, z~7.6,[65] is correct, it would explain why the galaxy's faint light reaches us at infrared wavelengths. It could only be observed with Hubble Space Telescope's Near Infrared Camera and Multi-Object Spectrometer (NICMOS) and the Spitzer Space Telescope's Infrared Array Camera exploiting the natural phenomenon of gravitational lensing: the galaxy cluster Abell 1689, which lies between Earth and A1689-zD1, at a distance of 2.2 billion light-years from us, functions as a natural "magnifying glass" for the light from the far more distant galaxy which lies directly behind it, at 700 million years after the Big Bang, as seen from Earth.[63]

A1703 zD6[edit | edit source]

A1703 zD6 is shown. Credit: NASA.{{free media}}

A1703 zD6 was reported as being a candidate for being a strongly lensed Lyman-break galaxy, within a 2012 publication by L.D.Bradley and others, within The Astrophysical Journal.[66] It has a redshift of 7 (a light travel time of 12.9 billion years), and its J2000 coordinates are 13 15 01.0 +51 50 04. It is located in the Canes Venatici constellation.

A2744-JD[edit | edit source]

A2744-JD is shown. Credit: NASA - Hubble Space Telescope.{{free media}}

For A2744-JD: Redshift zp≅9.8, Light travel distance 13.2 Gly, astronomical object type Galaxy.[67][68]

A2744 YD4[edit | edit source]

This image is dominated by a spectacular view of the rich galaxy cluster Abell 2744 from the NASA/ESA Hubble Space Telescope. Credit: ALMA (ESO/NAOJ/NRAO), NASA, ESA, ESO and D. Coe (STScI)/J. Merten (Heidelberg/Bologna).{{free media}}

Far beyond this cluster, and seen when the Universe was only about 600 million years old, is a very faint galaxy called A2744_YD4. New observations of this galaxy with the Atacama Large Millimeter Array (ALMA), shown in red, have demonstrated that it is rich in dust and the first signature of oxygen emitting light.[69]

Abell 115[edit | edit source]

"The very high velocity galaxy (ID 91) is a clear interloper far more than 3000 km s−1 from other galaxies. The other two high velocity galaxies (IDs 96 and 100), that are close enough in 2D [are] far from the high velocity BCM−A [3C 28] galaxy".[70]

There are "two structures of cluster-type well recognizable in the plane of the sky and [...] they differ of ~2000 km s−1 in the [line of sight] LOS velocity. The northern, high velocity subcluster (A115N) is likely centred on the second brightest cluster galaxy (BCM-A, coincident with radio source 3C28) and the northern X-ray peak."[70]

BDF-521[edit | edit source]

For BDF-521: Redshift z = 7.008, Light travel distance 13.04 Gly, astronomical object type Galaxy.[71]

BDF-3299[edit | edit source]

This view is a combination of images from ALMA and the Very Large Telescope. Credit: ESO/R. Maiolino.{{free media}}

For BDF-3299: Redshift z = 7.109, Light travel distance 13.05 Gly, Type of astronomical object: Galaxy.[71]

EGSY8p7[edit | edit source]

EGSY8p7 is imaged by the Hubble Space Telescope and Spitzer Space Telescope space telescopes. Credit: Ivo Labbe - Leiden University, NASA - Hubble & Spitzer Space Telescopes.{{free media}}

EGSY8p7 (EGSY-2008532660) is a distant galaxy in the constellation of Camelopardalis, with a spectroscopic redshift of z = 8.68 (photometric redshift 8.57), a light travel distance of 13.2 billion light-years from Earth; therefore, at an age of 13.2 billion years, it is observed as it existed 570 million years after the Big Bang, which occurred 13.8 billion years ago, using the W. M. Keck Observatory. In July 2015, EGSY8p7 was announced as the oldest and most-distant known object, surpassing the previous record holder, EGS-zs8-1, which was determined in May 2015 as the oldest and most distant object. In March 2016, Pascal Oesch, one of the discoverers of EGSY8p7, announced the discovery of GN-z11, an older and more distant galaxy.[72]

A possible explanation for the detection would be that reionization progressed in a "patchy" manner, rather than homogeneously throughout the universe, creating patches where the EGSY8p7 hydrogen Lyman-alpha emissions could travel to Earth, because there were no neutral hydrogen clouds to absorb the emissions.[73][74][75][76][77][78]

EGS-zs8-1[edit | edit source]

EGS-zs8-1 is viewed by the Hubble Space Telescope. Credit: NASA, ESA, P. Oesch and I. Momcheva (Yale University), and the 3D-HST and HUDF09/XDF Teams.{{free media}}

EGS-zs8-1 is a high-redshift Lyman-break galaxy found at the northern constellation of Boötes.[79] 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.[80][81] In July 2015, EGS-zs8-1 was surpassed by EGSY8p7 (EGSY-2008532660)[76]

The redshift of EGS-zs8-1 was measured at z = 7.73, corresponding to a light travel distance of about 13.04 billion light years from Earth, and age of 13.04 billion years. The galaxy shows a high rate of star formation, so it releases its peak radiation at the vacuum ultraviolet part of the electromagnetic spectrum, near the 121.567 nm (1,215.67 Å) Lyman-alpha emission line due to the intense radiation from newly formed blue stars, hence it is classified as a Lyman-break galaxy; high-redshift starburst galaxies emitting the Lyman-alpha emission line. Because of the cosmological redshift effect caused by the metric expansion of space, the peak light from the galaxy has become redshifted and has moved into the infrared part of the electromagnetic spectrum.[79] The galaxy has a comoving distance (light travel distance multiplied by the Hubble constant, caused by the metric expansion of space) of about 30 billion light years from Earth.[82]

EGS-zs8-1 was born 670 million years after the Big Bang, during the period of reionization, and it's 15 percent the size of the Milky Way. The galaxy was found to be larger than its other neighbors in that period when the universe was still very young.[81] Its mass at the time the light was emitted is estimated to have been about 15% of the Milky Way's current mass. The galaxy was making new stars at roughly 80 times the rate of the current Milky Way, or equivalent to 800 Solar mass worth of material turning to stars every year.[82] The light reaching Earth was made by stars in EGS-zs8-1 that were 100 million to 300 million years old at the time they emitted the light.[83] The age of EGS-zs8-1 places it in the reionization phase of creation, a time when hydrogen outside the galaxies was switching from a neutral to ionized state. According to the galaxy's discoverers, EGS-zs8-1 and other early galaxies were likely the causes of reionization.[84][85]

G2-1408[edit | edit source]

For G2-1408: Redshift z = 6.972, Light travel distance 13.03 Gly, and astronomical object type Galaxy.[86][87]

GN-108036[edit | edit source]

GN-108036 is shown as imaged by Hubble and Spitzer. Credit: NASA.{{free media}}

GN-108036 is a distant galaxy discovered and confirmed by the Subaru Telescope and the Keck Observatory located in Hawaii; its study was also completed by the Hubble Space Telescope and the Spitzer Space Telescope.[88]

For GN-108036: Redshift z = 7.213, Light travel distance = 13.07 Gly, type of astronomical object = Galaxy.[86][89]

GN-z11[edit | edit source]

GN-z11 is superimposed on an image from the GOODS-North survey. Credit: NASA, ESA, P. Oesch (Yale University), G. Brammer (STScI), P. van Dokkum (Yale University), and G. Illingworth (University of California, Santa Cruz).{{free media}}

GN-z11 is a high-redshift galaxy found in the constellation Ursa Major.[90] GN-z11 is currently the oldest and most distant known galaxy in the observable universe.[91] GN-z11 has a spectroscopic redshift of z = 11.09, which corresponds to a proper distance of approximately 32 billion light-years (9.8 billion parsecs).[92] At first glance, the distance of 32 billion light-years (9.8 billion parsecs) might seem impossibly far away in a Universe that is only 13.8 billion (short scale) years old, where a light year is the distance light travels in a year, and where nothing can travel faster than the speed of light. However, because of the expansion of the universe, the distance of 2.66 billion light years between GN-z11 and the Milky Way at the time when the light was emitted increased by a factor of (z+1)=12.1 to a distance of 32.2 billion light-years during the 13.4 billion years it has taken the light to reach us.

The object's name is derived from its location in the Great Observatories Origins Deep Survey field of galaxies and its high cosmological redshift number (GN + z11).[93] GN-z11 is observed as it existed 13.4 billion years ago, just 400 million years after the Big Bang;[94][95][96] as a result, GN-z11's distance is sometimes inappropriately[97] reported as 13.4 billion light years, its light travel distance measurement.[98][99]

The galaxy was identified by a team studying data from the Hubble Space Telescope's Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey (CANDELS) and Spitzer Space Telescope's Great Observatories Origins Deep Survey-North (GOODS-North).[100][101] The research team used Hubble's Wide Field Camera 3 to measure the distance to GN-z11 spectroscopically, by splitting the light into its component colors to measure the redshift caused by the expansion of the universe.[102] The findings, which were announced in March 2016, revealed the galaxy to be farther away than originally thought, at the distance limit of what the Hubble Telescope can observe. GN-z11 is around 150 million years older than the previous record-holder EGSY8p7,[93] and is observed (shortly after but) "very close to the end of the so-called Dark Ages of the universe",[102] and (during but) "near the very beginning" of the reionization era.[100]

HCM-6A[edit | edit source]

HCM-6A is a Lyman-alpha emitter (LAE) galaxy that was found in 2002 by using the W. M. Keck Observatory (Keck II Telescope) in Hawaii.[103] HCM-6A is located behind the Abell 370 galactic cluster, near Messier 77 (M77).[104] in the constellation Cetus, which enabled the astronomers to use Abell 370 as a gravitational lens to get a clearer image of the object.[103][105]

For HCM-6A: Redshift z = 6.56 and astronomical object type Galaxy, the first non-quasar galaxy found to exceed redshift 6 and exceeded the redshift of quasar SDSSp J103027.10+052455.0 of z = 6.28[106][107][108][109][110][111]

HVC 127-41-330[edit | edit source]

HVC 127-41-330 is a cloud rotating at high speed between Andromeda and the Triangulum Galaxy which may be a dark galaxy because of the speed of its rotation and its predicted mass.[112][113]

IOK-1[edit | edit source]

IOK-1 is imaged the Subaru Telescope. Credit: Masanori Iye, Subaru Telscope.{{free media}}

Notation: IOK stands for the observers' names Iye, Ota, and Kashikawa.

IOK-1 is a distant galaxy in the constellation Coma Berenice at redshift 6.96.[114]

The IOK-1's age and composition have been reliably established.[115][116]

LAE J095950.99+021219.1[edit | edit source]

LAE J095950.99+021219.1 is imaged. Credit: NASA.{{free media}}

LAE J095950.99+021219.1 is about 13 billion light years away and is a Lyman-alpha emitter.[117]

For LAE J095950.99+021219.1: Redshift z = 6.944, Light travel distance 13.03 Gly, astronomical object type Galaxy.[117]

MACS0647-JD[edit | edit source]

Hubble Space Telescope is image of MACS0647-JD. Credit: European Space Agency, NASA.{{free media}}
MACS0647-JD is very young and only a tiny fraction of the size of the Milky Way.[118] Credit: NASA, ESA, and M. Postman and D. Coe (Space Telescope Science Institute), and the CLASH team.{{free media}}

MACS0647-JD, a galaxy has a redshift of about z = 9.11, equivalent to a light travel distance of 13.26 billion light-years (4 billion parsecs), formed 130 million years after the Big Bang.[119][120][121][122][123]

MACS1149-JD1[edit | edit source]

Hubble and ALMA image shows galaxy cluster MACS J1149.5+2223 with an inset of MACS1149-JD1. Credit: ALMA (ESO/NAOJ/NRAO), NASA/ESA Hubble Space Telescope, W. Zheng (JHU), M. Postman (STScI), the CLASH Team, Hashimoto et al.{{free media}}

MACS1149-JD1 (also known as PCB2012 3020) is one of the farthest known galaxies from Earth and is at a redshift of about z=9.11,[124] or about 13.28 billion ly (4.07 billion pc) light-travel distance.[125]

For MACS1149-JD1: Redshift zp≅9.6, Light travel distance 13.2[126] Gly, astronomical object type Candidate galaxy or protogalaxy.[127]

NGC 1275[edit | edit source]

Hubble Space Telescope image is of NGC 1275. Credit: HST/NASA/ESA/STScI/AURA.{{free media}}

NGC 1275 consists of two galaxies, a central type-cD galaxy in the Perseus Cluster, and a so-called "high velocity system" (HVS) which lies in front of it. The HVS is moving at 3000 km/s[128] towards the dominant system, and is believed to be merging with the Perseus Cluster. The HVS is not affecting the cD galaxy as it lies at least 200 thousand light years from it.[129] however tidal interactions are disrupting it and ram-pressure stripping produced by its interaction with the intracluster medium of Perseus is stripping its gas as well as producing large amounts of star formation within it[130]

NGC 1365[edit | edit source]

A composite utilizing both HST and CXO data to visualize x-ray emission from the galaxy's nucleus. Credit: Judy Schmidt from USA.{{free media}}

NGC 1365 is notable for its central black hole spinning almost the speed of light.[131]

The image on the right is a composite utilizing both HST and CXO data to visualize x-ray emission from the galaxy's nucleus. Its bright central supermassive black hole is actively accreting matter and the surrounding disk is glowing hot with x-rays. Star formation encircling the nucleus also heats interstellar gas to create a diffuse, nebular glow further out from the nucleus.

Chandra data: Violet / Magenta overlay: ACIS .30-7.00 keV.

SDF J132418.3+271455[edit | edit source]

For SDF J132418.3+271455: Redshift z = 6.578 and astronomical object type Galaxy.[132][106][107][133]

SDF J132522.3+273520[edit | edit source]

For SDF J132522.3+273520: Redshift z = 6.597, astronomical object type Galaxy.[134][132]

SPT0615-JD[edit | edit source]

A closer detailed image is shown of SPT0615-JD. Credit: NASA/ESA/STScI/Brett Salmon.{{fairuse}}

For SPT0615-JD: Redshift z = 9.9, Light travel distance 13.27 Gly, astronomical object type Galaxy.[135]

This Hubble Space Telescope image on the right shows the farthest galaxy yet seen in an image that has been stretched and amplified by a phenomenon called gravitational lensing. The embryonic galaxy, named SPT0615-JD, existed when the universe was just 500 million years old. Though a few other primitive galaxies have been seen at this early epoch, they have essentially all looked like red dots, given their small size and tremendous distances. However, in this case, the gravitational field of a massive foreground galaxy cluster, called SPT-CL J0615-5746, not only amplified the light from the background galaxy but also smeared the image of it into an arc (about 2 arcseconds long). Image analysis shows that the galaxy weighs in at no more than 3 billion solar masses (roughly 1/100th the mass of our fully grown Milky Way galaxy). It is less than 2,500 light-years across, half the size of the Small Magellanic Cloud, a satellite galaxy of our Milky Way. The object is considered prototypical of young galaxies that emerged during the epoch shortly after the big bang.

SXDF-NB1006-2[edit | edit source]

SXDF-NB1006-2 is shown. Credit: Keck Telescope.{{free media}}

SXDF-NB1006-2 is a distant galaxy located in the Cetus constellation, with a spectroscopic redshift of z = 7.213 or 12.91 billion light-years away.[136] It was discovered by the Subaru XMM-Newton Deep Survey Field.[136] The galaxy was claimed to be the most distant galaxy at announcement in June 2012, as the more distant claimants were not confirmed spectroscopically at the time. It exceeded the previous confirmed distance holder, GN-108036, also discovered by the Subaru.[137] It contains the oldest oxygen in the Universe.[138]

UDFy-33436598[edit | edit source]

For UDFy-33436598: Redshift zp≅8.6, Light travel distance 13.1 Gly, astronomical object type Candidate galaxy or protogalaxy.[139]

UDFy-38135539[edit | edit source]

Hubble Space Telescope image of galaxy UDFy-38135539 located in the constellation Fornax at coordinates 03 32 38.13 -27 45 53.9. Credit: Hubble Space Telescope, NASA, ESA, G. Illingworth (UCO/Lick Observatory and University of California, Santa Cruz) and the HUDF09 Team.{{free media}}

For UDFy-38135539: Redshift z = 8.55, Light travel distance 13.1 Gly, astronomical object type Candidate galaxy or protogalaxy. A spectroscopic redshift of z = 8.55 was claimed for this source in 2010,[140] but has subsequently been shown to be mistaken.[141]

Astronomers using ESO’s Very Large Telescope (VLT) have now measured the distance to the most remote galaxy so far, UDFy-38135539 (the faint object shown in the excerpt on the right), which we see as it was when the Universe was only about 600 million years old (a redshift of 8.6). These are the first confirmed observations of a galaxy whose light is clearing the opaque hydrogen fog that filled the cosmos at this early time.

ULAS J1120+0641[edit | edit source]

In this composite image of ULAS J1120+0641 created from the Sloan Digital Sky Survey and the UKIRT Infrared Deep Sky Survey, the quasar appears as a faint red dot close to the centre. Credit: ESO/UKIDSS/SDSS.{{free media}}

ULAS J1120+0641 is the second most distant known quasar as of 6 December 2017, after ULAS J1342+0928.[10][12][11] ULAS J1120+0641 (at a comoving distance of 28.85 billion light-years) was the first quasar discovered beyond a redshift of 7.[142] Its discovery was reported in June 2011.[142] Various news reports, including those provided by the Associated Press, have stated that it is the brightest object seen so far in the universe.[143]

"ULAS J1120+0641 took the brightest object title from another quasar that wasn't formed until about 100 million years later, when the universe was 870 million years old."[143]

Such statements are erroneous, however; other quasars are known to be at least 100 times more luminous.[144]

ULAS J1120+0641 was discovered by the UKIRT Infrared Deep Sky Survey (UKIDSS), using the UK Infrared Telescope, located in Hawaii.[145] The name of the object is derived from UKIDSS Large Area Survey (ULAS), the name of the survey that discovered the quasar, and the location of the quasar in the sky in terms of right ascension (11h 20m) and declination (+06° 41'). This places the quasar in the constellation of Leo, close (on the plane of the sky) to σ Leo. The quasar was discovered by a telescope that operates at infrared wavelengths, which is at longer wavelength and lower energy than visible light. When the light was originally emitted by ULAS J1120+0641, it was in the ultraviolet, with shorter wavelength and higher energy than visible light. The change in energy and wavelength of the light is due to the expanding universe, which imparts a cosmological redshift to all light as it travels through the universe.[146]

The team of scientists spent years searching the UKIDSS for a quasar whose redshift was higher than 6.5. ULAS J1120+0641 is even farther away than they hoped for, with a redshift greater than 7.[147]

UKIDSS is a near infrared photometric survey, so the original discovery was only a photometric redshift of zphot>6.5.[142] Before announcing their discovery, the team used spectroscopy on the Gemini North Telescope and the Very Large Telescope to obtain a spectroscopic redshift of 7.085±0.003.[142]

ULAS J1120+0641 has a measured redshift of 7.085, which corresponds to a comoving distance of 28.85 billion light-years from Earth. Although this may appear to be larger than the size of the observable universe, this is not in fact a contradiction. As of 2011, it is the most distant quasar yet observed.[146] The quasar emitted the light observed on Earth today less than 770 million years after the Big Bang, about 13 billion years ago.[148] This is 100 million years earlier than light from the most distant previously known quasar.[149]

The quasar's luminosity is estimated at 6.3×1013
solar luminosities. This energy output is generated by a supermassive black hole estimated at 2++1.5
solar masses.[142][150] While the black hole powers the quasar, the light does not come from the black hole itself.[142]

"The super-massive black hole itself is dark but it has a disc of gas or dust around it that has become so hot that it will outshine an entire galaxy of stars."[146][142]

The light from ULAS J1120+0641 was emitted before the end of the theoretically-predicted transition of the intergalactic medium from an electrically neutral to an ionized state (the epoch of reionization). Quasars may have been an important energy source in this process, which marked the end of the cosmic Dark Ages, so observing a quasar from before the transition is of major interest to theoreticians.[150][151] Because of their high ultraviolet luminosity, quasars also are some of the best sources for studying the reionization process.

This is the first time scientists have seen a quasar with such a large fraction of neutral (non-ionized) hydrogen absorption in its spectrum. Mortlock estimates that 10% to 50% of the hydrogen at the redshift of ULAS J1120+0641 is neutral. The neutral hydrogen fraction in all other quasars seen, even those only 100 million years younger, was typically 1% or less.[146] The spectrum also lacked any significant indication of non-Big Bang nucleosynthesis metals, where the combination of the neutral hydrogen reading, and lack of metals is suggestive of the quasar being embedded in a protogalaxy in the midst of forming, and possibly creating the first Population III stars for the galaxy, or a pre-protogalaxy core still embedded in the primordial hydrogen fog, predating the Population III stellar population for this galaxy.[152]

The supermassive black hole in ULAS J1120+0641 has a higher mass than was expected, as the Eddington limit sets a maximum rate at which a black hole can grow, so the existence of such a massive black hole so soon after the Big Bang implies that it must have formed with a very high initial mass, through the merging of thousands of smaller black holes, or that the standard model of cosmology requires revision.[151]

ULAS J1342+0928[edit | edit source]

ULAS J1342+0928 is the most distant known quasar detected and contains the most distant and oldest known supermassive black hole.[10][11]

"This black hole grew far larger than we expected in only 690 million years after the Big Bang, which challenges our theories about how black holes form."[12][153] at a reported redshift of z = 7.54, surpassing the redshift of 7 for the previously known most distant quasar ULAS J1120+0641.[10] The ULAS J1342+0928 quasar is located in the Boötes constellation.[154] The related supermassive black hole is reported to be "800 million times the mass of the sun".[11]

On 6 December 2017,[10] astronomers published that they had found the quasar using data from the Wide-field Infrared Survey Explorer (WISE)[12] combined with ground-based surveys from one of the Magellan Telescopes at Las Campanas Observatory in Chile, as well as the Large Binocular Telescope in Arizona and the Gemini Observatory (Gemini North telescope) in Hawaii. The related black hole of the quasar existed when the universe was about 690 million years old (about 5 percent of its currently known age of 13.80 billion years).[10]

The quasar comes from a time known as "the epoch of reionization", when the universe emerged from its Dark Ages.[11] Extensive amounts of dust and gas have been detected to be released from the quasar into the interstellar medium of its host galaxy.[155]

ULAS J1342+0928 has a measured redshift of 7.54, which corresponds to a comoving distance of 29.36 billion light-years from Earth.[10][156] As of 2017, it is the most distant quasar yet observed. The quasar emitted the light observed on Earth today less than 690 million years after the Big Bang, about 13.1 billion years ago.[11][157]

The quasar's luminosity is estimated at 4×1013
solar luminosities.[10] This energy output is generated by a supermassive black hole estimated at 8×108
solar masses.[10] "This particular quasar is so bright that it will become a gold mine for follow-up studies and will be a crucial laboratory to study the early universe."[158][11]

The light from ULAS J1342+0928 was emitted before the end of the theoretically-predicted transition of the intergalactic medium from an electrically neutral to an ionized state (the epoch of reionization). Quasars may have been an important energy source in this process, which marked the end of the cosmic Dark Ages, so observing a quasar from before the transition is of major interest to theoreticians.[159][160] Because of their high ultraviolet luminosity, quasars also are some of the best sources for studying the reionization process. The discovery is also described as challenging theories of black hole formation, by having a supermassive black hole much larger than expected at such an early stage in the Universe's history,[12] though this is not the first distant quasar to offer such a challenge.[161]

"A black hole that grew to gargantuan size in the Universe's first billion years is by far the largest yet spotted from such an early date, researchers have announced. The object, discovered by astronomers in 2013, is 12 billion times as massive as the Sun, and six times greater than its largest-known contemporaries. Its existence poses a challenge for theories of the evolution of black holes, stars and galaxies, astronomers say. Light from the black hole took 12.9 billion years to reach Earth, so astronomers see the object as it was 900 million years after the Big Bang."[161] "That "is actually a very short time" for a black hole to have grown so large."[161]

"Now, researchers from the Max Planck Institute for Astronomy (MPIA) have discovered three quasars that challenge conventional wisdom on black hole growth. These quasars are extremely massive, but should not have had sufficient time to collect all that mass. The astronomers observed quasars whose light took nearly 13 billion years to reach Earth. In consequence, the observations show these quasars not as they are today, but as they were almost 13 billion years ago, less than a billion years after the big bang. The quasars in question have about a billion times the mass of the sun. All current theories of black hole growth postulate that, in order to grow that massive, the black holes would have needed to collect infalling matter, and shine brightly as quasars, for at least a hundred million years. But these three quasars proved to be have been active for a much shorter time, less than 100,000 years."[162]

"This is a surprising result. We don't understand how these young quasars could have grown the supermassive black holes that power them in such a short time."[162]

A small minority of sources argue that distant supermassive black holes whose large size is hard to explain so soon after the Big Bang, such as ULAS J1342+0928,[12] may be evidence that our universe is the result of a Big Bounce, instead of a Big Bang, with these supermassive black holes being formed before the Big Bounce.[163]

"It had reached its size just 690 million years after the point beyond which there is nothing. The most dominant scientific theory of recent years describes that point as the Big Bang — a spontaneous eruption of reality as we know it out of a quantum singularity. But another idea has recently been gaining weight: that the universe goes through periodic expansions and contractions — resulting in a “Big Bounce”. And the existence of early black holes has been predicted to be a key telltale as to whether or not the idea may be valid. This one is very big. To get to its size — 800 million times more mass than our Sun — it must have swallowed a lot of stuff. ... As far as we understand it, the universe simply wasn’t old enough at that time to generate such a monster."[163]

"This new theory that accepts that the Universe is going through periodic expansions and contractions is called "Big Bounce""[164]

z7 GSD 3811[edit | edit source]

For z7 GSD 3811: z = 7.66, light travel distance = 13.11 Gly, and it is a galaxy[165]

z8 GND 5296[edit | edit source]

This image from the NASA/ESA Hubble Space Telescope CANDELS survey highlights the most distant galaxy in the Universe with a definitively measured distance, dubbed z8_GND_5296. Credit: NASA, ESA, V. Tilvi (Texas A&M University), S. Finkelstein (University of Texas, Austin), and C. Papovich (Texas A&M University).{{free media}}

z8_GND_5296 is a dwarf galaxy[166] discovered in October 2013 which has the highest redshift that has been confirmed through the Lyman-alpha emission line of hydrogen,[167][168] placing it among the oldest and most distant known galaxies at approximately 13.1 billion light-years (4.0 Gpc) from Earth.[169][170] It is "seen as it was at a time just 700 million years after the Big Bang [...] when the universe was only about 5 percent of its current age of 13.8 billion years".[171] The galaxy is at a redshift of 7.51, and it is a neighbour to what was announced then as the second-most distant galaxy with a redshift of 7.2. The galaxy in its observable timeframe was producing stars at a phenomenal rate, equivalent in mass to about 330 Sun's per year.[167]

See also[edit | edit source]

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