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66-566: The SSA22 Protocluster , also known as EQ J221734.0+001701 , is a galaxy protocluster located at z=3.1 in the SSA 22 region. It is located at 22 17 34.0 +00° 17′ 01″ and was originally discovered in 1998. In 2006, a multifilamentary structure measuring 200 million light-years in width was announced, coinciding with the protocluster. Discovered in 2005 by Ryosuke Yamauchi from Tohoku University in Sendai, Japan, and his colleagues,

132-467: A {\displaystyle a} , e.g. a − 3 {\displaystyle a^{-3}} for matter etc., the Friedmann equation can be conveniently rewritten in terms of the various density parameters as where w {\displaystyle w} is the equation of state parameter of dark energy, and assuming negligible neutrino mass (significant neutrino mass requires

198-427: A laboratory, and its value is extremely small compared to vacuum energy theoretical predictions . The ΛCDM model has been shown to satisfy the cosmological principle , which states that, on a large-enough scale, the universe looks the same in all directions ( isotropy ) and from every location ( homogeneity ); "the universe looks the same whoever and wherever you are." The cosmological principle exists because when

264-566: A modification of the Einstein field equations and the Friedmann equations as seen in proposals such as modified gravity theory (MOG theory) or tensor–vector–scalar gravity theory (TeVeS theory). Other proposals by theoretical astrophysicists of cosmological alternatives to Einstein's general relativity that attempt to account for dark energy or dark matter include f(R) gravity , scalar–tensor theories such as galileon  [ ko ] theories (see Galilean invariance ), brane cosmologies ,

330-399: A more complex equation). The various Ω {\displaystyle \Omega } parameters add up to 1 {\displaystyle 1} by construction. In the general case this is integrated by computer to give the expansion history a ( t ) {\displaystyle a(t)} and also observable distance–redshift relations for any chosen values of

396-496: A preferred direction in studies of alignments in quasar polarizations, scaling relations in galaxy clusters, strong lensing time delay, Type Ia supernovae, and quasars and gamma-ray bursts as standard candles . The fact that all these independent observables, based on different physics, are tracking the CMB dipole direction suggests that the Universe is anisotropic in the direction of

462-413: A reasonably good account of: The model assumes that general relativity is the correct theory of gravity on cosmological scales. It emerged in the late 1990s as a concordance cosmology , after a period of time when disparate observed properties of the universe appeared mutually inconsistent, and there was no consensus on the makeup of the energy density of the universe. Some alternative models challenge

528-458: Is above or below the so-called critical density. During the 1970s, most attention focused on pure-baryonic models, but there were serious challenges explaining the formation of galaxies, given the small anisotropies in the CMB (upper limits at that time). In the early 1980s, it was realized that this could be resolved if cold dark matter dominated over the baryons, and the theory of cosmic inflation motivated models with critical density. During

594-412: Is called the S 8 {\displaystyle S_{8}} tension. The name "tension" reflects that the disagreement is not merely between two data sets: the many sets of early- and late-time measurements agree well within their own categories, but there is an unexplained difference between values obtained from different points in the evolution of the universe. Such a tension indicates that

660-418: Is fairly accurate for a > 0.01 {\displaystyle a>0.01} or t > 10 {\displaystyle t>10} million years. Solving for a ( t ) = 1 {\displaystyle a(t)=1} gives the present age of the universe t 0 {\displaystyle t_{0}} in terms of the other parameters. It follows that

726-458: Is one of b {\displaystyle \mathrm {b} } for baryons , c {\displaystyle \mathrm {c} } for cold dark matter , r a d {\displaystyle \mathrm {rad} } for radiation ( photons plus relativistic neutrinos ), and Λ {\displaystyle \Lambda } for dark energy . Since the densities of various species scale as different powers of

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792-400: Is the only cosmological model consistent with the observed continuing expansion of space, the observed distribution of lighter elements in the universe (hydrogen, helium, and lithium), and the spatial texture of minute irregularities ( anisotropies ) in the CMB radiation. Cosmic inflation also addresses the " horizon problem " in the CMB; indeed, it seems likely that the universe is larger than

858-423: Is the speed of light and G {\displaystyle G} is the gravitational constant . A critical density ρ c r i t {\displaystyle \rho _{\mathrm {crit} }} is the present-day density, which gives zero curvature k {\displaystyle k} , assuming the cosmological constant Λ {\displaystyle \Lambda }

924-417: Is the time-derivative of the scale factor. The first Friedmann equation gives the expansion rate in terms of the matter+radiation density ρ {\displaystyle \rho } , the curvature k {\displaystyle k} , and the cosmological constant Λ {\displaystyle \Lambda } , where, as usual c {\displaystyle c}

990-501: Is the use of the Phoenix galaxy cluster to observe a dwarf galaxy in its early high energy stages of star formation. Lambda-CDM model The Lambda-CDM , Lambda cold dark matter , or ΛCDM model is a mathematical model of the Big Bang theory with three major components: It is referred to as the standard model of Big Bang cosmology because it is the simplest model that provides

1056-531: Is violated on large scales. Data from the Planck Mission shows hemispheric bias in the cosmic microwave background in two respects: one with respect to average temperature (i.e. temperature fluctuations), the second with respect to larger variations in the degree of perturbations (i.e. densities). The European Space Agency (the governing body of the Planck Mission) has concluded that these anisotropies in

1122-453: Is zero, regardless of its actual value. Substituting these conditions to the Friedmann equation gives where h ≡ H 0 / ( 100 k m ⋅ s − 1 ⋅ M p c − 1 ) {\displaystyle h\equiv H_{0}/(100\;\mathrm {km{\cdot }s^{-1}{\cdot }Mpc^{-1}} )} is

1188-459: The Planck spacecraft . The discovery of the cosmic microwave background (CMB) in 1964 confirmed a key prediction of the Big Bang cosmology. From that point on, it was generally accepted that the universe started in a hot, dense state and has been expanding over time. The rate of expansion depends on the types of matter and energy present in the universe, and in particular, whether the total density

1254-471: The DGP model , and massive gravity and its extensions such as bimetric gravity . In addition to explaining many pre-2000 observations, the model has made a number of successful predictions: notably the existence of the baryon acoustic oscillation feature, discovered in 2005 in the predicted location; and the statistics of weak gravitational lensing , first observed in 2000 by several teams. The polarization of

1320-450: The Hubble diagram of Type Ia supernovae and quasars . This contradicts the cosmological principle. The CMB dipole is hinted at through a number of other observations. First, even within the cosmic microwave background, there are curious directional alignments and an anomalous parity asymmetry that may have an origin in the CMB dipole. Separately, the CMB dipole direction has emerged as

1386-436: The gravitational lensing of light by galaxy clusters; and the enhanced clustering of galaxies) that cannot be accounted for by the quantity of observed matter. The ΛCDM model proposes specifically cold dark matter , hypothesized as: Dark matter constitutes about 26.5 % of the mass–energy density of the universe. The remaining 4.9 % comprises all ordinary matter observed as atoms, chemical elements, gas and plasma,

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1452-441: The stress–energy tensor that, according to the general theory of relativity, causes accelerating expansion. The fraction of the total energy density of our (flat or almost flat) universe that is dark energy, Ω Λ {\displaystyle \Omega _{\Lambda }} , is estimated to be 0.669 ± 0.038 based on the 2018 Dark Energy Survey results using Type Ia supernovae or 0.6847 ± 0.0073 based on

1518-431: The 1980s, most research focused on cold dark matter with critical density in matter, around 95 % CDM and 5 % baryons: these showed success at forming galaxies and clusters of galaxies, but problems remained; notably, the model required a Hubble constant lower than preferred by observations, and observations around 1988–1990 showed more large-scale galaxy clustering than predicted. These difficulties sharpened with

1584-300: The 2018 release of Planck satellite data, or more than 68.3 % (2018 estimate) of the mass–energy density of the universe. Dark matter is postulated in order to account for gravitational effects observed in very large-scale structures (the "non-keplerian" rotation curves of galaxies;

1650-469: The CMB are, in fact, statistically significant and can no longer be ignored. Already in 1967, Dennis Sciama predicted that the cosmic microwave background has a significant dipole anisotropy. In recent years, the CMB dipole has been tested, and the results suggest our motion with respect to distant radio galaxies and quasars differs from our motion with respect to the cosmic microwave background . The same conclusion has been reached in recent studies of

1716-475: The CMB dipole. Nevertheless, some authors have stated that the universe around Earth is isotropic at high significance by studies of the cosmic microwave background temperature maps. Based on N-body simulations in ΛCDM, Yadav and his colleagues showed that the spatial distribution of galaxies is statistically homogeneous if averaged over scales 260 /h Mpc or more. However, many large-scale structures have been discovered, and some authors have reported some of

1782-599: The CMB, discovered in 2002 by DASI, has been successfully predicted by the model: in the 2015 Planck data release, there are seven observed peaks in the temperature (TT) power spectrum, six peaks in the temperature–polarization (TE) cross spectrum, and five peaks in the polarization (EE) spectrum. The six free parameters can be well constrained by the TT spectrum alone, and then the TE and EE spectra can be predicted theoretically to few-percent precision with no further adjustments allowed. Over

1848-497: The Hubble constant based on the cosmic background radiation compared to astronomical distance measurements. This difference has been called the Hubble tension . The Hubble tension in cosmology is widely acknowledged to be a major problem for the ΛCDM model. In December 2021, National Geographic reported that the cause of the Hubble tension discrepancy is not known. However, if the cosmological principle fails (see Violations of

1914-513: The Hubble constant. However, other work has found no evidence for this in observations, finding the scale of the claimed underdensity to be incompatible with observations which extend beyond its radius. Important deficiencies were subsequently pointed out in this analysis, leaving open the possibility that the Hubble tension is indeed caused by outflow from the KBC void. As a result of the Hubble tension, other researchers have called for new physics beyond

1980-448: The assumptions of the ΛCDM model. Examples of these are modified Newtonian dynamics , entropic gravity , modified gravity, theories of large-scale variations in the matter density of the universe, bimetric gravity , scale invariance of empty space, and decaying dark matter (DDM). The ΛCDM model includes an expansion of metric space that is well documented, both as the redshift of prominent spectral absorption or emission lines in

2046-403: The birth of the universe), defined relative to the present time, so a 0 = a ( t 0 ) = 1 {\displaystyle a_{0}=a(t_{0})=1} ; the usual convention in cosmology is that subscript 0 denotes present-day values, so t 0 {\displaystyle t_{0}} denotes the age of the universe. The scale factor is related to

SSA22 Protocluster - Misplaced Pages Continue

2112-418: The center of a galaxy cluster should lose more energy than photons coming from the edge of the cluster because gravity is stronger in the center. Light emitted from the center of a cluster has a longer wavelength than light coming from the edge. This effect is known as gravitational redshift . Using the data collected from 8000 galaxy clusters, Wojtak was able to study the properties of gravitational redshift for

2178-536: The collision velocity leads to strong ( 6.16 σ {\displaystyle 6.16\sigma } ) tension with the ΛCDM model. The properties of El Gordo are however consistent with cosmological simulations in the framework of MOND due to more rapid structure formation. The KBC void is an immense, comparatively empty region of space containing the Milky Way approximately 2 billion light-years (600 megaparsecs, Mpc) in diameter. Some authors have said

2244-416: The cosmological parameters, which can then be compared with observations such as supernovae and baryon acoustic oscillations . In the minimal 6-parameter Lambda-CDM model, it is assumed that curvature Ω k {\displaystyle \Omega _{k}} is zero and w = − 1 {\displaystyle w=-1} , so this simplifies to Observations show that

2310-471: The cosmological principle ), then the existing interpretations of the Hubble constant and the Hubble tension have to be revised, which might resolve the Hubble tension. Some authors postulate that the Hubble tension can be explained entirely by the KBC void , as measuring galactic supernovae inside a void is predicted by the authors to yield a larger local value for the Hubble constant than cosmological measures of

2376-392: The critical density; though other outcomes are possible in extended models where the dark energy is not constant but actually time-dependent. It is standard to define the present-day density parameter Ω x {\displaystyle \Omega _{x}} for various species as the dimensionless ratio where the subscript x {\displaystyle x}

2442-467: The diameter of the Andromeda Galaxy . Some scientists believe that these giant bubbles formed after massive stars born in the early universe exploded as supernovae and ejected their surrounding gases. The galaxies and gas bubbles that are part of this structure line up along three curved filaments, or arms, that formed approximately 2 billion years after the Big Bang . These filaments were observed with

2508-558: The discovery of CMB anisotropy by the Cosmic Background Explorer in 1992, and several modified CDM models, including ΛCDM and mixed cold and hot dark matter, came under active consideration through the mid-1990s. The ΛCDM model then became the leading model following the observations of accelerating expansion in 1998, and was quickly supported by other observations: in 2000, the BOOMERanG microwave background experiment measured

2574-558: The distribution of galaxies in clusters. He found that the light from the clusters was redshifted in proportion to the distance from the center of the cluster as predicted by general relativity. The result also strongly supports the Lambda-Cold Dark Matter model of the Universe, according to which most of the cosmos is made up of Dark Matter that does not interact with matter. Galaxy clusters are also used for their strong gravitational potential as gravitational lenses to boost

2640-442: The existence of the KBC void violates the assumption that the CMB reflects baryonic density fluctuations at z = 1100 {\displaystyle z=1100} or Einstein's theory of general relativity , either of which would violate the ΛCDM model, while other authors have claimed that supervoids as large as the KBC void are consistent with the ΛCDM model. Statistically significant differences remain in measurements of

2706-534: The following properties: There are three main components of a galaxy cluster. They are tabulated below: Galaxy clusters are categorized as type I, II, or III based on morphology. Galaxy clusters have been used by Radek Wojtak from the Niels Bohr Institute at the University of Copenhagen to test predictions of general relativity : energy loss from light escaping a gravitational field. Photons emitted from

SSA22 Protocluster - Misplaced Pages Continue

2772-552: The help of the Subaru and Keck telescopes located on the Mauna Kea volcano in Hawaii. This structure is not only incredibly large, but also very dense; the galaxies located in each of the filaments are four times closer to each other than the universe's average. Before its discovery, astronomers had predicted the existence of a structure like this one. According to computer models, several of

2838-574: The light from distant galaxies, and as the time dilation in the light decay of supernova luminosity curves. Both effects are attributed to a Doppler shift in electromagnetic radiation as it travels across expanding space. Although this expansion increases the distance between objects that are not under shared gravitational influence, it does not increase the size of the objects (e.g. galaxies) in space. Also since it originates from ordinary general relativity, it, like general relativity, allows for distant galaxies to recede from each other at speeds greater than

2904-485: The model and pin down the parameter values, most of which are constrained below 1 percent uncertainty. Research is active into many aspects of the ΛCDM model, both to refine the parameters and to resolve the tensions between recent observations and the ΛCDM model, such as the Hubble tension and the CMB dipole . In addition, ΛCDM has no explicit physical theory for the origin or physical nature of dark matter or dark energy;

2970-549: The most massive galaxies originated in structures like this. These galaxies are believed to have formed as a result of blobs like those constituent to this structure collapsing under their own gravity. Since the densest areas in the universe are thought to be the places where galaxies formed first, this structure may be one of the earliest to have formed. This structure may reveal when and how the first galaxies formed and could help us better understand how our own galaxy came to be. Galaxy protocluster Notable galaxy clusters in

3036-514: The most massive galaxy clusters found in the early Universe. In the last few decades, they are also found to be relevant sites of particle acceleration, a feature that has been discovered by observing non-thermal diffuse radio emissions, such as radio halos and radio relics . Using the Chandra X-ray Observatory , structures such as cold fronts and shock waves have also been found in many galaxy clusters. Galaxy clusters typically have

3102-461: The nearly scale-invariant spectrum of the CMB perturbations, and their image across the celestial sphere, are believed to result from very small thermal and acoustic irregularities at the point of recombination. Historically, a large majority of astronomers and astrophysicists support the ΛCDM model or close relatives of it, but recent observations that contradict the ΛCDM model have led some astronomers and astrophysicists to search for alternatives to

3168-563: The observable particle horizon . The model uses the Friedmann–Lemaître–Robertson–Walker metric , the Friedmann equations , and the cosmological equations of state to describe the observable universe from approximately 0.1 s to the present. The expansion of the universe is parameterized by a dimensionless scale factor a = a ( t ) {\displaystyle a=a(t)} (with time t {\displaystyle t} counted from

3234-418: The observed redshift z {\displaystyle z} of the light emitted at time t e m {\displaystyle t_{\mathrm {em} }} by The expansion rate is described by the time-dependent Hubble parameter , H ( t ) {\displaystyle H(t)} , defined as where a ˙ {\displaystyle {\dot {a}}}

3300-442: The predecessors of the ΛCDM model were being developed, there was not sufficient data available to distinguish between more complex anisotropic or inhomogeneous models, so homogeneity and isotropy were assumed to simplify the models, and the assumptions were carried over into the ΛCDM model. However, recent findings have suggested that violations of the cosmological principle, especially of isotropy, exist. These violations have called

3366-506: The radiation density is very small today, Ω rad ∼ 10 − 4 {\displaystyle \Omega _{\text{rad}}\sim 10^{-4}} ; if this term is neglected the above has an analytic solution where t Λ ≡ 2 / ( 3 H 0 Ω Λ )   ; {\displaystyle t_{\Lambda }\equiv 2/(3H_{0}{\sqrt {\Omega _{\Lambda }}})\ ;} this

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3432-487: The reach of telescopes. The gravitational distortion of space-time occurs near massive galaxy clusters and bends the path of photons to create a cosmic magnifying glass. This can be done with photons of any wavelength from the optical to the X-ray band. The latter is more difficult, because galaxy clusters emit a lot of X-rays. However, X-ray emission may still be detected when combining X-ray data to optical data. One particular case

3498-461: The reduced Hubble constant. If the cosmological constant were actually zero, the critical density would also mark the dividing line between eventual recollapse of the universe to a Big Crunch , or unlimited expansion. For the Lambda-CDM model with a positive cosmological constant (as observed), the universe is predicted to expand forever regardless of whether the total density is slightly above or below

3564-628: The relatively nearby Universe include the Virgo Cluster , Fornax Cluster , Hercules Cluster , and the Coma Cluster . A very large aggregation of galaxies known as the Great Attractor , dominated by the Norma Cluster , is massive enough to affect the local expansion of the Universe . Notable galaxy clusters in the distant, high-redshift universe include SPT-CL J0546-5345 and SPT-CL J2106-5844 ,

3630-588: The speed of light; local expansion is less than the speed of light, but expansion summed across great distances can collectively exceed the speed of light. The letter Λ ( lambda ) represents the cosmological constant , which is associated with a vacuum energy or dark energy in empty space that is used to explain the contemporary accelerating expansion of space against the attractive effects of gravity. A cosmological constant has negative pressure, p = − ρ c 2 {\displaystyle p=-\rho c^{2}} , which contributes to

3696-490: The structure was found in a region of the universe known to contain large concentrations of gas. The structure is a very distant object; the astronomers that discovered it were actually looking at something from 12 billion years ago. This object is made up of lyman-break galaxies and large gas bubbles, such as lyman-alpha blobs and lyman-alpha emitters gaseous filaments. Some of the gas bubbles that make up this colossal structure are up to 400,000 light-years across, over twice

3762-494: The structures to be in conflict with the predicted scale of homogeneity for ΛCDM, including Other authors claim that the existence of structures larger than the scale of homogeneity in the ΛCDM model does not necessarily violate the cosmological principle in the ΛCDM model. El Gordo is a massive interacting galaxy cluster in the early Universe ( z = 0.87 {\displaystyle z=0.87} ). The extreme properties of El Gordo in terms of its redshift, mass, and

3828-508: The stuff of which visible planets, stars and galaxies are made. The great majority of ordinary matter in the universe is unseen, since visible stars and gas inside galaxies and clusters account for less than 10 % of the ordinary matter contribution to the mass–energy density of the universe. The model includes a single originating event, the " Big Bang ", which was not an explosion but the abrupt appearance of expanding spacetime containing radiation at temperatures of around 10  K. This

3894-405: The total (matter–energy) density to be close to 100 % of critical, whereas in 2001 the 2dFGRS galaxy redshift survey measured the matter density to be near 25 %; the large difference between these values supports a positive Λ or dark energy . Much more precise spacecraft measurements of the microwave background from WMAP in 2003–2010 and Planck in 2013–2015 have continued to support

3960-408: The transition from decelerating to accelerating expansion (the second derivative a ¨ {\displaystyle {\ddot {a}}} crossing zero) occurred when which evaluates to a ∼ 0.6 {\displaystyle a\sim 0.6} or z ∼ 0.66 {\displaystyle z\sim 0.66} for the best-fit parameters estimated from

4026-419: The years, numerous simulations of ΛCDM and observations of our universe have been made that challenge the validity of the ΛCDM model, to the point where some cosmologists believe that the ΛCDM model may be superseded by a different, as yet unknown cosmological model. Extensive searches for dark matter particles have so far shown no well-agreed detection, while dark energy may be almost impossible to detect in

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4092-483: The ΛCDM model into question, with some authors suggesting that the cosmological principle is obsolete or that the Friedmann–Lemaître–Robertson–Walker metric breaks down in the late universe. This has additional implications for the validity of the cosmological constant in the ΛCDM model, as dark energy is implied by observations only if the cosmological principle is true. Evidence from galaxy clusters , quasars , and type Ia supernovae suggest that isotropy

4158-517: The ΛCDM model quantifies the amplitude of matter fluctuations in the late universe and is defined as Early- (e.g. from CMB data collected using the Planck observatory) and late-time (e.g. measuring weak gravitational lensing events) facilitate increasingly precise values of S 8 {\displaystyle S_{8}} . However, these two categories of measurement differ by more standard deviations than their uncertainties. This discrepancy

4224-411: The ΛCDM model, which include dropping the Friedmann–Lemaître–Robertson–Walker metric or modifying dark energy . On the other hand, Milgrom , McGaugh , and Kroupa have long been leading critics of the ΛCDM model, attacking the dark matter portions of the theory from the perspective of galaxy formation models and supporting the alternative modified Newtonian dynamics (MOND) theory, which requires

4290-439: The ΛCDM model. Moritz Haslbauer et al. proposed that MOND would resolve the Hubble tension. Another group of researchers led by Marc Kamionkowski proposed a cosmological model with early dark energy to replace ΛCDM. The S 8 {\displaystyle S_{8}} tension in cosmology is another major problem for the ΛCDM model. The S 8 {\displaystyle S_{8}} parameter in

4356-457: Was immediately (within 10 seconds) followed by an exponential expansion of space by a scale multiplier of 10 or more, known as cosmic inflation . The early universe remained hot (above 10 000 K) for several hundred thousand years, a state that is detectable as a residual cosmic microwave background , or CMB, a very low-energy radiation emanating from all parts of the sky. The "Big Bang" scenario, with cosmic inflation and standard particle physics,

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