The Experts below are selected from a list of 197490 Experts worldwide ranked by ideXlab platform
J Daângela - One of the best experts on this subject based on the ideXlab platform.
-
the 2df qso redshift survey xiv structure and evolution from the two point Correlation Function
Monthly Notices of the Royal Astronomical Society, 2005Co-Authors: S M Croom, B J Boyle, T Shanks, R J Smith, L Miller, P J Outram, N S Loaring, Fiona Hoyle, J DaângelaAbstract:In this paper we present a clustering analysis of quasi-stellar objects (QSOs) using over 20 000 objects from the final catalogue of the 2dF QSO Redshift Survey (2QZ), measuring the redshift-space Two-Point Correlation Function, ξ(s). When averaged over the redshift range 0.3 < z < 2.2 we find that ξ(s) is flat on small scales, steepening on scales above ∼25 h -1 Mpc. In a WMAP/2dF cosmology (Ω m = 0.27, Ω A = 0.73) we find a best-fitting power law with so = 5.48 +0.42 -0.48 h -1 Mpc and γ = 1.20 ± 0.10 on scales s = 1 to 25 h -1 Mpc. We demonstrate that non-linear redshift-space distortions have a significant effect on the QSO ξ(s) at scales less than ∼10 h -1 Mpc. A cold dark matter model assuming WMAP/2dF cosmological parameters is a good description of the QSO ξ(s) after accounting for non-linear clustering and redshift-space distortions, and allowing for a linear bias at the mean redshift of b Q (z = 1.35) = 2.02 ± 0.07. We subdivide the 2QZ into 10 redshift intervals with effective redshifts from z = 0.53 to 2.48. We find a significant increase in clustering amplitude at high redshift in the WMAP/2dF cosmology. The QSO clustering amplitude increases with redshift such that the integrated Correlation Function, ξ(s), within 20 h -1 Mpc is ξ(20, z = 0.53) = 0.26 ± 0.08 and ξ(20, z = 2.48) = 0.70 ± 0.17. We derive the QSO bias and find it to be a strong Function of redshift with b Q (z = 0.53) = 1.13 ± 0.18 and b Q (z = 2.48) = 4.24 ± 0.53. We use these bias values to derive the mean dark matter halo (DMH) mass occupied by the QSOs. At all redshifts 2QZ QSOs inhabit approximately the same mass DMHs with M DH = (3.0 ± 1.6) × 10 12 h -1 M ○. , which is close to the characteristic mass in the Press-Schechter mass Function, M*, at z = 0. These results imply that LQ QSOs at z ∼ 0 should be largely unbiased. If the relation between black hole (BH) mass and M DH or host velocity dispersion does not evolve, then we find that the accretion efficiency (L /L Edd ) for LQ QSOs is approximately constant with redshift. Thus the fading of the QSO population from z ∼ 2 to ∼0 appears to be due to less massive BHs being active at low redshift. We apply different methods to estimate, t Q , the active lifetime of QSOs and constrain t Q to be in the range 4 x 10 6 -6 x 10 8 yr at z ∼2. We test for any luminosity dependence of QSO clustering by measuring ξ(s) as a Function of apparent magnitude (equivalent to luminosity relative to L* Q ). However, we find no significant evidence of luminosity-dependent clustering from this data set.
-
the 2df qso redshift survey xiv structure and evolution from the two point Correlation Function
Monthly Notices of the Royal Astronomical Society, 2005Co-Authors: S M Croom, B J Boyle, T Shanks, R J Smith, L Miller, P J Outram, N S Loaring, Fiona Hoyle, J DaângelaAbstract:In this paper we present a clustering analysis of quasi-stellar objects (QSOs) using over 20 000 objects from the final catalogue of the 2dF QSO Redshift Survey (2QZ), measuring the redshift-space Two-Point Correlation Function, ξ(s). When averaged over the redshift range 0.3 < z < 2.2 we find that ξ(s) is flat on small scales, steepening on scales above ∼25 h -1 Mpc. In a WMAP/2dF cosmology (Ω m = 0.27, Ω A = 0.73) we find a best-fitting power law with so = 5.48 +0.42 -0.48 h -1 Mpc and γ = 1.20 ± 0.10 on scales s = 1 to 25 h -1 Mpc. We demonstrate that non-linear redshift-space distortions have a significant effect on the QSO ξ(s) at scales less than ∼10 h -1 Mpc. A cold dark matter model assuming WMAP/2dF cosmological parameters is a good description of the QSO ξ(s) after accounting for non-linear clustering and redshift-space distortions, and allowing for a linear bias at the mean redshift of b Q (z = 1.35) = 2.02 ± 0.07. We subdivide the 2QZ into 10 redshift intervals with effective redshifts from z = 0.53 to 2.48. We find a significant increase in clustering amplitude at high redshift in the WMAP/2dF cosmology. The QSO clustering amplitude increases with redshift such that the integrated Correlation Function, ξ(s), within 20 h -1 Mpc is ξ(20, z = 0.53) = 0.26 ± 0.08 and ξ(20, z = 2.48) = 0.70 ± 0.17. We derive the QSO bias and find it to be a strong Function of redshift with b Q (z = 0.53) = 1.13 ± 0.18 and b Q (z = 2.48) = 4.24 ± 0.53. We use these bias values to derive the mean dark matter halo (DMH) mass occupied by the QSOs. At all redshifts 2QZ QSOs inhabit approximately the same mass DMHs with M DH = (3.0 ± 1.6) × 10 12 h -1 M ○. , which is close to the characteristic mass in the Press-Schechter mass Function, M*, at z = 0. These results imply that LQ QSOs at z ∼ 0 should be largely unbiased. If the relation between black hole (BH) mass and M DH or host velocity dispersion does not evolve, then we find that the accretion efficiency (L /L Edd ) for LQ QSOs is approximately constant with redshift. Thus the fading of the QSO population from z ∼ 2 to ∼0 appears to be due to less massive BHs being active at low redshift. We apply different methods to estimate, t Q , the active lifetime of QSOs and constrain t Q to be in the range 4 x 10 6 -6 x 10 8 yr at z ∼2. We test for any luminosity dependence of QSO clustering by measuring ξ(s) as a Function of apparent magnitude (equivalent to luminosity relative to L* Q ). However, we find no significant evidence of luminosity-dependent clustering from this data set.
Alexander S Szalay - One of the best experts on this subject based on the ideXlab platform.
-
doppler term in the galaxy two point Correlation Function wide angle velocity doppler lensing and cosmic acceleration effects
Physics of the Dark Universe, 2017Co-Authors: Alvise Raccanelli, Donghui Jeong, Daniele Bertacca, Mark C Neyrinck, Alexander S SzalayAbstract:Abstract We study the parity-odd part (that we shall call Doppler term) of the linear galaxy Two-Point Correlation Function that arises from wide-angle, velocity, Doppler lensing and cosmic acceleration effects. As it is important at low redshift and at large angular separations, the Doppler term is usually neglected in the current generation of galaxy surveys. For future wide-angle galaxy surveys, however, we show that the Doppler term must be included. The effect of these terms is dominated by the magnification due to relativistic aberration effects and the slope of the galaxy redshift distribution and it generally mimics the effect of the local type primordial non-Gaussianity with the effective nonlinearity parameter f NL eff of a few; we show that this would affect forecasts on measurements of f NL at low-redshift. Our results show that a survey at low redshift with large number density over a wide area of the sky could detect the Doppler term with a signal-to-noise ratio of ∼ 1 − 20 , depending on survey specifications.
-
doppler term in the galaxy two point Correlation Function wide angle velocity doppler lensing and cosmic acceleration effects
arXiv: Cosmology and Nongalactic Astrophysics, 2016Co-Authors: Alvise Raccanelli, Donghui Jeong, Daniele Bertacca, Mark C Neyrinck, Alexander S SzalayAbstract:We study the parity-odd part (that we shall call Doppler term) of the linear galaxy Two-Point Correlation Function that arises from wide-angle, velocity, Doppler lensing and cosmic acceleration effects. As it is important at low redshift and at large angular separations, the Doppler term is usually neglected in the current generation of galaxy surveys. For future wide-angle galaxy surveys such as Euclid, SPHEREx and SKA, however, we show that the Doppler term must be included. The effect of these terms is dominated by the magnification due to relativistic aberration effects and the slope of the galaxy redshift distribution and it generally mimics the effect of the local type primordial non-Gaussianity with the effective nonlinearity parameter $f_{\rm NL}^{\rm eff}$ of a few, we show that this would affect forecasts on measurements of $f_{\rm NL}$ at low-redshift. Our results show that a survey at low redshift with large number density over a wide area of the sky could detect the Doppler term with a signal-to-noise ratio of $\sim 1-20$, depending on survey specifications.
-
the redshift space galaxy two point Correlation Function and baryon acoustic oscillations
Monthly Notices of the Royal Astronomical Society, 2015Co-Authors: Donghui Jeong, Marc Kamionkowski, Alexander S SzalayAbstract:Future galaxy surveys will measure baryon acoustic oscillations (BAOs) with high significance, and a complete understanding of the anisotropies of BAOs in redshift space will be important to exploit the cosmological information in BAOs. Here we describe the anisotropies that arise in the redshift-space galaxy Two-Point Correlation Function (2PCF) and elucidate the origin of features that arise in the dependence of the BAOs on the angle between the orientation of the galaxy pair and the line of sight. We do so with a derivation of the configuration-space 2PCF using streaming model. We find that, contrary to common belief, the locations of BAO peaks in the redshift-space 2PCF are anisotropic even in the linear theory. Anisotropies in BAO depend strongly on the method of extracting the peak, showing maximum 3 % angular variation. We also find that extracting the BAO peak of $r^2\xi(r,\mu)$ significantly reduces the anisotropy to sub-percent level angular variation. When subtracting the tilt due to the broadband behavior of the 2PCF, the BAO bump is enhanced along the line of sight because of local infall velocities toward the BAO bump. Precise measurement of the angular dependence of the redshift-space 2PCF will allow new geometrical tests of dark energy beyond the BAO.
Donghui Jeong - One of the best experts on this subject based on the ideXlab platform.
-
doppler term in the galaxy two point Correlation Function wide angle velocity doppler lensing and cosmic acceleration effects
Physics of the Dark Universe, 2017Co-Authors: Alvise Raccanelli, Donghui Jeong, Daniele Bertacca, Mark C Neyrinck, Alexander S SzalayAbstract:Abstract We study the parity-odd part (that we shall call Doppler term) of the linear galaxy Two-Point Correlation Function that arises from wide-angle, velocity, Doppler lensing and cosmic acceleration effects. As it is important at low redshift and at large angular separations, the Doppler term is usually neglected in the current generation of galaxy surveys. For future wide-angle galaxy surveys, however, we show that the Doppler term must be included. The effect of these terms is dominated by the magnification due to relativistic aberration effects and the slope of the galaxy redshift distribution and it generally mimics the effect of the local type primordial non-Gaussianity with the effective nonlinearity parameter f NL eff of a few; we show that this would affect forecasts on measurements of f NL at low-redshift. Our results show that a survey at low redshift with large number density over a wide area of the sky could detect the Doppler term with a signal-to-noise ratio of ∼ 1 − 20 , depending on survey specifications.
-
doppler term in the galaxy two point Correlation Function wide angle velocity doppler lensing and cosmic acceleration effects
arXiv: Cosmology and Nongalactic Astrophysics, 2016Co-Authors: Alvise Raccanelli, Donghui Jeong, Daniele Bertacca, Mark C Neyrinck, Alexander S SzalayAbstract:We study the parity-odd part (that we shall call Doppler term) of the linear galaxy Two-Point Correlation Function that arises from wide-angle, velocity, Doppler lensing and cosmic acceleration effects. As it is important at low redshift and at large angular separations, the Doppler term is usually neglected in the current generation of galaxy surveys. For future wide-angle galaxy surveys such as Euclid, SPHEREx and SKA, however, we show that the Doppler term must be included. The effect of these terms is dominated by the magnification due to relativistic aberration effects and the slope of the galaxy redshift distribution and it generally mimics the effect of the local type primordial non-Gaussianity with the effective nonlinearity parameter $f_{\rm NL}^{\rm eff}$ of a few, we show that this would affect forecasts on measurements of $f_{\rm NL}$ at low-redshift. Our results show that a survey at low redshift with large number density over a wide area of the sky could detect the Doppler term with a signal-to-noise ratio of $\sim 1-20$, depending on survey specifications.
-
the redshift space galaxy two point Correlation Function and baryon acoustic oscillations
Monthly Notices of the Royal Astronomical Society, 2015Co-Authors: Donghui Jeong, Marc Kamionkowski, Alexander S SzalayAbstract:Future galaxy surveys will measure baryon acoustic oscillations (BAOs) with high significance, and a complete understanding of the anisotropies of BAOs in redshift space will be important to exploit the cosmological information in BAOs. Here we describe the anisotropies that arise in the redshift-space galaxy Two-Point Correlation Function (2PCF) and elucidate the origin of features that arise in the dependence of the BAOs on the angle between the orientation of the galaxy pair and the line of sight. We do so with a derivation of the configuration-space 2PCF using streaming model. We find that, contrary to common belief, the locations of BAO peaks in the redshift-space 2PCF are anisotropic even in the linear theory. Anisotropies in BAO depend strongly on the method of extracting the peak, showing maximum 3 % angular variation. We also find that extracting the BAO peak of $r^2\xi(r,\mu)$ significantly reduces the anisotropy to sub-percent level angular variation. When subtracting the tilt due to the broadband behavior of the 2PCF, the BAO bump is enhanced along the line of sight because of local infall velocities toward the BAO bump. Precise measurement of the angular dependence of the redshift-space 2PCF will allow new geometrical tests of dark energy beyond the BAO.
-
clustering fossils from the early universe
Physical Review Letters, 2012Co-Authors: Donghui Jeong, Marc KamionkowskiAbstract:Many inflationary theories introduce new scalar, vector, or tensor degrees of freedom that may then affect the generation of primordial density perturbations. Here we show how to search a galaxy (or 21-cm) survey for the imprint of primordial scalar, vector, and tensor fields. These new fields induce local departures to an otherwise statistically isotropic Two-Point Correlation Function, or equivalently, nontrivial four-point Correlation Functions (or trispectra, in Fourier space), that can be decomposed into scalar, vector, and tensor components. We write down the optimal estimators for these various components and show how the sensitivity to these modes depends on the galaxy-survey parameters. New probes of parity-violating early-Universe physics are also presented.
Y P Jing - One of the best experts on this subject based on the ideXlab platform.
-
accurate fitting formula for the two point Correlation Function of dark matter halos
The Astrophysical Journal, 1998Co-Authors: Y P JingAbstract:An accurate fitting formula is reported for the Two-Point Correlation Function ? -->hh(r;M) of dark matter halos in hierarchical clustering models. It is valid for the linearly clustering regime, and its accuracy is about 10% in ? -->hh(r;M) for the halos with mass M > (10 -->?2-10 -->?3)M -->*, where M -->* is the characteristic nonlinear mass. The result is found on the basis of a careful analysis for a large set of scale-free simulations with 2563 particles. The fitting formula has a weak explicit dependence on the index n of the initial power spectrum but can be equally well applied to the cold dark matter (CDM) cosmological models if the effective index neff${r eff}$ -->$t SUBgt {r eff}t/SUBgt $ --> of the CDM power spectrum at the scale of the halo mass replaces the index n. The formula agrees with the analytical formula of Mo & White for massive halos with M > M -->*, but the Mo & White formula significantly underpredicts ? -->hh(r;M) for the less massive halos. The difference between the fitting and the analytical formulae amounts to a factor 2 in ? -->hh(r;M) for M=0.01M -->*. One of the most interesting applications of this fitting formula would be the clustering of galaxies, since the majority of halos hosting galaxies satisfies MM -->*.
-
spatial Correlation Function and pairwise velocity dispersion of galaxies cold dark matter models versus the las campanas survey
The Astrophysical Journal, 1998Co-Authors: Y P Jing, Gerhard BornerAbstract:We show, with the help of large N-body simulations, that both the real-space Two-Point Correlation Function and pairwise velocity dispersion of galaxies can be measured reliably from the Las Campanas Redshift Survey. The real-space Correlation Function is well fitted by the power law ξ(r) = (r0/r)γ with r0 = (5.06 ± 0.12) h-1 Mpc and γ = 1.862 ± 0.034, and the pairwise velocity dispersion at 1 h-1 Mpc is 570 ± 80 km s-1. A detailed comparison between these observational results and the predictions of current cold dark matter (CDM) cosmogonies is carried out. We construct 60 mock samples for each theoretical model from a large set of high-resolution N-body simulations, which allows us to include various observational selection effects in the analyses and to use exactly the same methods for both real and theoretical samples. We demonstrate that such a procedure is essential in the comparison between models and observations. The observed Two-Point Correlation Function is significantly flatter than the mass Correlation Function in current CDM models on scales 1 h-1 Mpc. The observed pairwise velocity dispersion is also lower than that of dark matter particles in these models. We propose a simple antibias model to explain these discrepancies. This model assumes that the number of galaxies per unit dark matter mass, N/M, decreases with the mass of dark haloes. The predictions of CDM models with σ8 Ω0.60~0.4-0.5 and Γ ~ 0.2 are in agreement with the observational results, if the trend of N/M with M is at the level already observed for rich clusters of galaxies. Thus CDM models with Γ ~ 0.2 and with cluster-abundance normalization are consistent with the observed Correlation Function and pairwise velocity dispersion of galaxies. A high level of velocity bias is not required in these models.
-
spatial Correlation Function and pairwise velocity dispersion of galaxies cdm models versus the las campanas survey
arXiv: Astrophysics, 1997Co-Authors: Y P Jing, G BoernerAbstract:We show, with the help of large N-body simulations, that the real-space Two-Point Correlation Function and pairwise velocity dispersion of galaxies can both be measured reliably from the Las Campanas Redshift Survey. The real-space Correlation Function is well fitted by the power law $\xi(r)=(r_0/r)^\gamma$ with $r_0=(5.06\pm0.12)\mpc$ and $\gamma=1.862\pm 0.034$, and the pairwise velocity dispersion at $1\mpc$ is $(570\pm 80)\kms$. A detailed comparison between these observational results and the predictions of current CDM cosmogonies is carried out. We construct 60 mock samples for each theoretical model from a large set of high resolution N-body simulations, which allows us to include various observational selection effects in the analyses and to use exactly the same methods for both real and theoretical samples. We demonstrate that such a procedure is essential in the comparison between models and observations. The observed Two-Point Correlation Function is significantly flatter than the mass Correlation Function in current CDM models on scales $\la 1\mpc$. The observed pairwise velocity dispersion is also lower than that of dark matter particles in these models. We propose a simple antibias model to explain these discrepancies. This model assumes that the number of galaxies per unit dark matter mass, $N/M$, decreases with the mass of dark haloes. The predictions of CDM models with $\sigma_8\Omega_0^{0.6}\sim 0.4$-0.5 and $\Omega_0 h\sim 0.2$ are in agreement with the observational results, if the trend of $N/M$ with $M$ is at the level already observed for rich clusters of galaxies. Thus CDM models with cluster-abundance normalization are consistent with the observed Correlation Function and pairwise velocity dispersion of galaxies. A high level of velocity bias is not required in these models.
V Terras - One of the best experts on this subject based on the ideXlab platform.
-
on the thermodynamic limit of form factors in the massless xxz heisenberg chain
arXiv: High Energy Physics - Theory, 2009Co-Authors: N Kitanine, Karol K Kozlowski, J M Maillet, N A Slavnov, V TerrasAbstract:We consider the problem of computing form factors of the massless XXZ Heisenberg spin-1/2 chain in a magnetic field in the (thermodynamic) limit where the size M of the chain becomes large. For that purpose, we take the particular example of the matrix element of the third component of spin between the ground state and an excited state with one particle and one hole located at the opposite ends of the Fermi interval (umklapp-type term). We exhibit its power-law decrease in terms of the size of the chain M, and compute the corresponding exponent and amplitude. As a consequence, we show that this form factor is directly related to the amplitude of the leading oscillating term in the long-distance asymptotic expansion of the Two-Point Correlation Function of the third component of spin.
-
form factors of the xxz heisenberg spin 1 2 finite chain
Nuclear Physics, 1999Co-Authors: N Kitanine, J M Maillet, V TerrasAbstract:Abstract Form factors for local spin operators of the XXZ Heisenberg spin-z finite chain are computed. Representation theory of Drinfel'd twists in terms of F-matrices for the quantum affine algebra U q ( s l 2 ) in finite-dimensional modules is used to calculate scalar products of two states involving one Bethe state (leading to Gaudin formula) and to solve the quantum inverse problem for local spin operators in the finite chain. Hence, we obtain the representation of the n-spin Correlation Functions in terms of expectation values (in ferromagnetic reference state) of the operator entries of the quantum monodromy matrix satisfying Yang-Baxter algebra. This leads to the direct calculation of the form factors of the XXZ Heisenberg spin-! finite chain as determinants of usual Functions of the parameters of the model. A Two-Point Correlation Function for adjacent sites is also derived using similar techniques.
-
form factors of the xxz heisenberg spin 1 2 finite chain
arXiv: Mathematical Physics, 1998Co-Authors: N Kitanine, J M Maillet, V TerrasAbstract:Form factors for local spin operators of the XXZ Heisenberg spin-1/2 finite chain are computed. Representation theory of Drinfel'd twists for the sl2 quantum affine algebra in finite dimensional modules is used to calculate scalar products of Bethe states (leading to Gaudin formula) and to solve the quantum inverse problem for local spin operators in the finite XXZ chain. Hence, we obtain the representation of the n-spin Correlation Functions in terms of expectation values(in ferromagnetic reference state) of the operator entries of the quantum monodromy matrix satisfying Yang-Baxter algebra. This leads to the direct calculation of the form factors of the XXZ Heisenberg spin-1/2 finite chain as determinants of usual Functions of the parameters of the model. A Two-Point Correlation Function for adjacent sites is also derived using similar techniques.
