The Experts below are selected from a list of 15075 Experts worldwide ranked by ideXlab platform
Bharat Ratra - One of the best experts on this subject based on the ideXlab platform.
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using pantheon and des supernova baryon Acoustic Oscillation and hubble parameter data to constrain the hubble constant dark energy dynamics and spatial curvature
Monthly Notices of the Royal Astronomical Society, 2021Co-Authors: Shu-lei Cao, Joseph V Ryan, Bharat RatraAbstract:We use Pantheon Type Ia supernova (SN Ia) apparent magnitude, DES-3yr binned SN Ia apparent magnitude, Hubble parameter, and baryon Acoustic Oscillation measurements to constrain six spatially flat and non-flat cosmological models. These sets of data provide mutually consistent cosmological constraints in the six cosmological models we study. A joint analysis of these data sets provides model-independent estimates of the Hubble constant, $H_0=68.8\pm1.8\ \rm{km \ s^{-1} \ Mpc^{-1}}$, and the non-relativistic matter density parameter, $\Omega_{\rm m_0}=0.294\pm0.020$. Although the joint constraints prefer mild dark energy dynamics and a little spatial curvature, they do not rule out dark energy being a cosmological constant and flat spatial hypersurfaces. We also add quasar angular size and H II starburst galaxy measurements to the combined data set and find more restrictive constraints.
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Quasar X-ray and UV flux, baryon Acoustic Oscillation, and Hubble parameter measurement constraints on cosmological model parameters
Monthly Notices of the Royal Astronomical Society, 2020Co-Authors: Narayan Khadka, Bharat RatraAbstract:We use the Risaliti & Lusso (2015) compilation of 808 X-ray and UV flux measurements of quasars (QSOs) in the redshift range $0.061 \leq z \leq 6.28$, alone and in conjuction with baryon Acoustic Oscillation (BAO) and Hubble parameter [$H(z)$] measurements, to constrain cosmological parameters in six cosmological models. The QSO data constraints are significantly weaker than, but consistent with, those from the $H(z)$ + BAO data. A joint analysis of the QSO + $H(z)$ + BAO data is consistent with the current standard model, spatially-flat $\Lambda$CDM, but mildly favors closed spatial hypersurfaces and dynamical dark energy.
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baryon Acoustic Oscillation hubble parameter and angular size measurement constraints on the hubble constant dark energy dynamics and spatial curvature
Monthly Notices of the Royal Astronomical Society, 2019Co-Authors: Joseph V Ryan, Y. Q. Chen, Bharat RatraAbstract:In this paper we use all available baryon Acoustic Oscillation, Hubble parameter, and quasar angular size data to constrain six dark energy cosmological models, both spatially flat and non-flat. Depending on the model and data combination considered, these data mildly favor closed spatial hypersurfaces (by as much as $1.7\sigma$) and dark energy dynamics (up to a little over $2\sigma$) over a cosmological constant $\Lambda$. The data also favor, at $1.8\sigma$ to $3.4\sigma$, depending on the model and data combination, a lower Hubble constant than what is measured from the local expansion rate.
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measuring the hubble constant and spatial curvature from supernova apparent magnitude baryon Acoustic Oscillation and hubble parameter data
Astrophysics and Space Science, 2019Co-Authors: Changyung Park, Bharat RatraAbstract:Cosmic microwave background (CMB) anisotropy (spatial inhomogeneity) data provide the tightest constraints on the Hubble constant, matter density, spatial curvature, and dark energy dynamics. Other data, sensitive to the evolution of only the spatially homogeneous part of the cosmological model, such as Type Ia supernova apparent magnitude, baryon Acoustic Oscillation distance, and Hubble parameter measurements, can be used in conjunction with the CMB data to more tightly constrain parameters. Recent joint analyses of CMB and such non-CMB data indicate that slightly closed spatial hypersurfaces are favored in nonflat untilted inflation models and that dark energy dynamics cannot be ruled out, and favor a smaller Hubble constant. We show that the constraints that follow from these non-CMB data alone are consistent with those that follow from the CMB data alone and so also consistent with, but weaker than, those that follow from the joint analyses of the CMB and non-CMB data.
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Constraints on dark energy dynamics and spatial curvature from Hubble parameter and baryon Acoustic Oscillation data
Monthly Notices of the Royal Astronomical Society, 2018Co-Authors: Joseph Ryan, Sanket Doshi, Bharat RatraAbstract:We use all available baryon Acoustic Oscillation distance measurements and Hubble parameter data to constrain the cosmological constant $\Lambda$, dynamical dark energy, and spatial curvature in simple cosmological models. We find that the consensus spatially flat $\Lambda$CDM model provides a reasonable fit to the data, but depending on the Hubble constant prior and cosmological model, it can be a little more than 1$\sigma$ away from the best-fit model, which can favor mild dark energy dynamics or non-flat spatial hypersurfaces.
Daniel J Eisenstein - One of the best experts on this subject based on the ideXlab platform.
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constraining the baryon dark matter relative velocity with the large scale three point correlation function of the sdss boss dr12 cmass galaxies
Monthly Notices of the Royal Astronomical Society, 2018Co-Authors: Zachary Slepian, Daniel J Eisenstein, Jonathan Blazek, Joel R Brownstein, Chiahsun Chuang, Hector Gilmarin, Shirley HoAbstract:We search for a galaxy clustering bias due to a modulation of galaxy number with the baryon-dark matter relative velocity resulting from recombination-era physics. We find no detected signal and place the constraint bv < 0.01 on the relative velocity bias for the CMASS galaxies. This bias is an important potential systematic of Baryon Acoustic Oscillation (BAO) method measurements of the cosmic distance scale using the 2-point clustering. Our limit on the relative velocity bias indicates a systematic shift of no more than 0.3% rms in the distance scale inferred from the BAO feature in the BOSS 2-point clustering, well below the 1% statistical error of this measurement. This constraint is the most stringent currently available and has important implications for the ability of upcoming large-scale structure surveys such as DESI to self-protect against the relative velocity as a possible systematic.
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modelling the large scale redshift space 3 point correlation function of galaxies
Monthly Notices of the Royal Astronomical Society, 2017Co-Authors: Zachary Slepian, Daniel J EisensteinAbstract:Author(s): Slepian, Zachary; Eisenstein, Daniel J | Abstract: We present a configuration-space model of the large-scale galaxy 3-point correlation function (3PCF) based on leading-order perturbation theory and including redshift space distortions (RSD). This model should be useful in extracting distance-scale information from the 3PCF via the Baryon Acoustic Oscillation (BAO) method. We include the first redshift-space treatment of biasing by the baryon-dark matter relative velocity. Overall, on large scales the effect of RSD is primarily a renormalization of the 3PCF that is roughly independent of both physical scale and triangle opening angle; for our adopted $\Omega_{\rm m}$ and bias values, the rescaling is a factor of $\sim 1.8$. We also present an efficient scheme for computing 3PCF predictions from our model, important for allowing fast exploration of the space of cosmological parameters in future analyses.
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modelling the large scale redshift space 3 point correlation function of galaxies
Monthly Notices of the Royal Astronomical Society, 2017Co-Authors: Zachary Slepian, Daniel J EisensteinAbstract:Author(s): Slepian, Z; Eisenstein, DJ | Abstract: We present a configuration-space model of the large-scale galaxy 3-point correlation function (3PCF) based on leading-order perturbation theory and including redshift-space distortions (RSD). This model should be useful in extracting distance-scale information from the 3PCF via the baryon Acoustic Oscillation method. We include the first redshift-space treatment of biasing by the baryon-dark matter relative velocity. Overall, on large scales the effect of RSD is primarily a renormalization of the 3PCF that is roughly independent of both physical scale and triangle opening angle; for our adoptedm and bias values, the rescaling is a factor of ∼1.8. We also present an efficient scheme for computing 3PCF predictions from our model, important for allowing fast exploration of the space of cosmological parameters in future analyses.
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measuring the baryon Acoustic Oscillation scale using the sloan digital sky survey and 2df galaxy redshift survey
Monthly Notices of the Royal Astronomical Society, 2007Co-Authors: Will J Percival, Shaun Cole, Daniel J Eisenstein, R C Nichol, J A Peacock, Adrian Pope, Alexander S SzalayAbstract:We introduce a method to constrain general cosmological models using Baryon Acoustic Oscillation (BAO) distance measurements from galaxy samples covering different redshift ranges, and apply this method to analyse samples drawn from the Sloan Digital Sky Survey (SDSS) and 2dF Galaxy Redshift Survey (2dFGRS). BAOs are detected in the clustering of the combined 2dFGRS and SDSS main galaxy samples, and measure the distance–redshift relation at z= 0.2. BAOs in the clustering of the SDSS luminous red galaxies measure the distance–redshift relation at z= 0.35. The observed scales of the BAOs calculated from these samples and from the combined sample are jointly analysed using estimates of the correlated errors, to constrain the form of the distance measure DV(z) ≡[(1 +z)2D2Acz/H(z)]1/3. Here DA is the angular diameter distance, and H(z) is the Hubble parameter. This gives rs/DV(0.2) = 0.1980 ± 0.0058 and rs/DV(0.35) = 0.1094 ± 0.0033 (1σ errors), with a correlation coefficient of 0.39, where rs is the comoving sound horizon scale at recombination. Matching the BAOs to have the same measured scale at all redshifts then gives DV(0.35)/DV(0.2) = 1.812 ± 0.060. The recovered ratio is roughly consistent with that predicted by the higher redshift Supernova Legacy Survey (SNLS) supernova data for Λ cold dark matter cosmologies, but does require slightly stronger cosmological acceleration at a low redshift. If we force the cosmological model to be flat with constant w, then we find Ωm= 0.249 ± 0.018 and w=−1.004 ± 0.089 after combining with the SNLS data, and including the WMAP measurement of the apparent Acoustic horizon angle in the cosmic microwave background.
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dark energy and curvature from a future baryonic Acoustic Oscillation survey using the lyman alpha forest
Physical Review D, 2007Co-Authors: Patrick Mcdonald, Daniel J EisensteinAbstract:We explore the requirements for a Lyman-$\ensuremath{\alpha}$ forest survey designed to measure the angular diameter distance and Hubble parameter at $2\ensuremath{\lesssim}z\ensuremath{\lesssim}4$ using the standard ruler provided by baryonic Acoustic Oscillations (BAO). The goal would be to obtain a high enough density of sources to probe the three-dimensional density field on the scale of the BAO feature. A percent-level measurement in this redshift range can almost double the Dark Energy Task Force figure of merit, relative to the case with only a similar precision measurement at $z\ensuremath{\sim}1$, if the Universe is not assumed to be flat. This improvement is greater than the one obtained by doubling the size of the $z\ensuremath{\sim}1$ survey, with Planck and a weak Sloan Digital Sky Survey-like $z=0.3$ BAO measurement assumed in each case. Galaxy BAO surveys at $z\ensuremath{\sim}1$ may be able to make an effective $\mathrm{Ly}\ensuremath{\alpha}$ forest measurement simultaneously at minimal added cost, because the required number density of quasars is relatively small. We discuss the constraining power as a function of area, magnitude limit (density of quasars), resolution, and signal-to-noise of the spectra. For example, a survey covering 2000 sq. deg. and achieving $S/N=1.8$ per \AA{} at $g=23$ ($\ensuremath{\sim}40\text{ }\text{ }\mathrm{quasars}$ per sq. deg.) with an $R\ensuremath{\gtrsim}250$ spectrograph is sufficient to measure both the radial and transverse Oscillation scales to 1.4% from the $\mathrm{Ly}\ensuremath{\alpha}$ forest (or better, if fainter magnitudes and possibly Lyman-break galaxies can be used). At fixed integration time and in the sky-noise-dominated limit, a wider, noisier survey is generally more efficient; the only fundamental upper limit on noise being the need to identify a quasar and find a redshift. Because the $\mathrm{Ly}\ensuremath{\alpha}$ forest is much closer to linear and generally better understood than galaxies, systematic errors are even less likely to be a problem.
Patrick Mcdonald - One of the best experts on this subject based on the ideXlab platform.
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the baryon Acoustic Oscillation broadband and broad beam array design overview and sensitivity forecasts
The Astronomical Journal, 2013Co-Authors: Jonathan C Pober, Tzuching Chang, Patrick Mcdonald, Aaron R Parsons, David R Deboer, Matthew Mcquinn, James E Aguirre, Richard F Bradley, M F MoralesAbstract:This work describes a new instrument optimized for a detection of the neutral hydrogen 21 cm power spectrum between redshifts of 0.5 and 1.5: the Baryon Acoustic Oscillation Broadband and Broad-beam (BAOBAB) array. BAOBAB will build on the efforts of a first generation of 21 cm experiments that are targeting a detection of the signal from the Epoch of Reionization at z ~ 10. At z ~ 1, the emission from neutral hydrogen in self-shielded overdense halos also presents an accessible signal, since the dominant, synchrotron foreground emission is considerably fainter than at redshift 10. The principle science driver for these observations are baryon Acoustic Oscillations in the matter power spectrum which have the potential to act as a standard ruler and constrain the nature of dark energy. BAOBAB will fully correlate dual-polarization antenna tiles over the 600-900 MHz band with a frequency resolution of 300 kHz and a system temperature of 50 K. The number of antennas will grow in staged deployments, and reconfigurations of the array will allow for both traditional imaging and high power spectrum sensitivity operations. We present calculations of the power spectrum sensitivity for various array sizes, with a 35 element array measuring the cosmic neutral hydrogen fraction as a function of redshift, and a 132 element system detecting the BAO features in the power spectrum, yielding a 1.8% error on the z ~ 1 distance scale, and, in turn, significant improvements to constraints on the dark energy equation of state over an unprecedented range of redshifts from ~0.5 to 1.5.
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baryon Acoustic Oscillation intensity mapping of dark energy
Physical Review Letters, 2008Co-Authors: Tzuching Chang, Jeffrey B Peterson, Patrick McdonaldAbstract:The expansion of the Universe appears to be accelerating, and the mysterious antigravity agent of this acceleration has been called ``dark energy.'' To measure the dynamics of dark energy, baryon Acoustic Oscillations (BAO) can be used. Previous discussions of the BAO dark energy test have focused on direct measurements of redshifts of as many as ${10}^{9}$ individual galaxies, by observing the 21 cm line or by detecting optical emission. Here we show how the study of Acoustic Oscillation in the 21 cm brightness can be accomplished by economical three-dimensional intensity mapping. If our estimates gain acceptance they may be the starting point for a new class of dark energy experiments dedicated to large angular scale mapping of the radio sky, shedding light on dark energy.
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dark energy and curvature from a future baryonic Acoustic Oscillation survey using the lyman alpha forest
Physical Review D, 2007Co-Authors: Patrick Mcdonald, Daniel J EisensteinAbstract:We explore the requirements for a Lyman-$\ensuremath{\alpha}$ forest survey designed to measure the angular diameter distance and Hubble parameter at $2\ensuremath{\lesssim}z\ensuremath{\lesssim}4$ using the standard ruler provided by baryonic Acoustic Oscillations (BAO). The goal would be to obtain a high enough density of sources to probe the three-dimensional density field on the scale of the BAO feature. A percent-level measurement in this redshift range can almost double the Dark Energy Task Force figure of merit, relative to the case with only a similar precision measurement at $z\ensuremath{\sim}1$, if the Universe is not assumed to be flat. This improvement is greater than the one obtained by doubling the size of the $z\ensuremath{\sim}1$ survey, with Planck and a weak Sloan Digital Sky Survey-like $z=0.3$ BAO measurement assumed in each case. Galaxy BAO surveys at $z\ensuremath{\sim}1$ may be able to make an effective $\mathrm{Ly}\ensuremath{\alpha}$ forest measurement simultaneously at minimal added cost, because the required number density of quasars is relatively small. We discuss the constraining power as a function of area, magnitude limit (density of quasars), resolution, and signal-to-noise of the spectra. For example, a survey covering 2000 sq. deg. and achieving $S/N=1.8$ per \AA{} at $g=23$ ($\ensuremath{\sim}40\text{ }\text{ }\mathrm{quasars}$ per sq. deg.) with an $R\ensuremath{\gtrsim}250$ spectrograph is sufficient to measure both the radial and transverse Oscillation scales to 1.4% from the $\mathrm{Ly}\ensuremath{\alpha}$ forest (or better, if fainter magnitudes and possibly Lyman-break galaxies can be used). At fixed integration time and in the sky-noise-dominated limit, a wider, noisier survey is generally more efficient; the only fundamental upper limit on noise being the need to identify a quasar and find a redshift. Because the $\mathrm{Ly}\ensuremath{\alpha}$ forest is much closer to linear and generally better understood than galaxies, systematic errors are even less likely to be a problem.
Zachary Slepian - One of the best experts on this subject based on the ideXlab platform.
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constraining the baryon dark matter relative velocity with the large scale three point correlation function of the sdss boss dr12 cmass galaxies
Monthly Notices of the Royal Astronomical Society, 2018Co-Authors: Zachary Slepian, Daniel J Eisenstein, Jonathan Blazek, Joel R Brownstein, Chiahsun Chuang, Hector Gilmarin, Shirley HoAbstract:We search for a galaxy clustering bias due to a modulation of galaxy number with the baryon-dark matter relative velocity resulting from recombination-era physics. We find no detected signal and place the constraint bv < 0.01 on the relative velocity bias for the CMASS galaxies. This bias is an important potential systematic of Baryon Acoustic Oscillation (BAO) method measurements of the cosmic distance scale using the 2-point clustering. Our limit on the relative velocity bias indicates a systematic shift of no more than 0.3% rms in the distance scale inferred from the BAO feature in the BOSS 2-point clustering, well below the 1% statistical error of this measurement. This constraint is the most stringent currently available and has important implications for the ability of upcoming large-scale structure surveys such as DESI to self-protect against the relative velocity as a possible systematic.
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modelling the large scale redshift space 3 point correlation function of galaxies
Monthly Notices of the Royal Astronomical Society, 2017Co-Authors: Zachary Slepian, Daniel J EisensteinAbstract:Author(s): Slepian, Zachary; Eisenstein, Daniel J | Abstract: We present a configuration-space model of the large-scale galaxy 3-point correlation function (3PCF) based on leading-order perturbation theory and including redshift space distortions (RSD). This model should be useful in extracting distance-scale information from the 3PCF via the Baryon Acoustic Oscillation (BAO) method. We include the first redshift-space treatment of biasing by the baryon-dark matter relative velocity. Overall, on large scales the effect of RSD is primarily a renormalization of the 3PCF that is roughly independent of both physical scale and triangle opening angle; for our adopted $\Omega_{\rm m}$ and bias values, the rescaling is a factor of $\sim 1.8$. We also present an efficient scheme for computing 3PCF predictions from our model, important for allowing fast exploration of the space of cosmological parameters in future analyses.
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modelling the large scale redshift space 3 point correlation function of galaxies
Monthly Notices of the Royal Astronomical Society, 2017Co-Authors: Zachary Slepian, Daniel J EisensteinAbstract:Author(s): Slepian, Z; Eisenstein, DJ | Abstract: We present a configuration-space model of the large-scale galaxy 3-point correlation function (3PCF) based on leading-order perturbation theory and including redshift-space distortions (RSD). This model should be useful in extracting distance-scale information from the 3PCF via the baryon Acoustic Oscillation method. We include the first redshift-space treatment of biasing by the baryon-dark matter relative velocity. Overall, on large scales the effect of RSD is primarily a renormalization of the 3PCF that is roughly independent of both physical scale and triangle opening angle; for our adoptedm and bias values, the rescaling is a factor of ∼1.8. We also present an efficient scheme for computing 3PCF predictions from our model, important for allowing fast exploration of the space of cosmological parameters in future analyses.
Christopher M Hirata - One of the best experts on this subject based on the ideXlab platform.
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small scale structure and the lyman α forest baryon Acoustic Oscillation feature
Monthly Notices of the Royal Astronomical Society, 2018Co-Authors: Christopher M HirataAbstract:The baryon-Acoustic Oscillation (BAO) feature in the Lyman-$\alpha$ forest is one of the key probes of the cosmic expansion rate at redshifts z~2.5, well before dark energy is believed to have become dynamically significant. A key advantage of the BAO as a standard ruler is that it is a sharp feature and hence is more robust against broadband systematic effects than other cosmological probes. However, if the Lyman-$\alpha$ forest transmission is sensitive to the initial streaming velocity of the baryons relative to the dark matter, then the BAO peak position can be shifted. Here we investigate this sensitivity using a suite of hydrodynamic simulations of small regions of the intergalactic medium with a range of box sizes and physics assumptions; each simulation starts from initial conditions at the kinematic decoupling era (z~1059), undergoes a discrete change from neutral gas to ionized gas thermal evolution at reionization (z~8), and is finally processed into a Lyman-$\alpha$ forest transmitted flux cube. Streaming velocities suppress small-scale structure, leading to less violent relaxation after reionization. The changes in the gas distribution and temperature-density relation at low redshift are more subtle, due to the convergent temperature evolution in the ionized phase. The change in the BAO scale is estimated to be of the order of 0.12% at z=2.5; some of the major uncertainties and avenues for future improvement are discussed. The predicted streaming velocity shift would be a subdominant but not negligible effect (of order $0.26\sigma$) for the upcoming DESI Lyman-$\alpha$ forest survey, and exceeds the cosmic variance floor. It is hoped that this study will motivate additional theoretical work on the magnitude of the BAO shift, both in the Lyman-$\alpha$ forest and in other tracers of large-scale structure.
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streaming velocities and the baryon Acoustic Oscillation scale
Physical Review Letters, 2016Co-Authors: J Blazek, Joseph E Mcewen, Christopher M HirataAbstract:At the epoch of decoupling, cosmic baryons had supersonic velocities relative to the dark matter that were coherent on large scales. These velocities subsequently slow the growth of small-scale structure and, via feedback processes, can influence the formation of larger galaxies. We examine the effect of streaming velocities on the galaxy correlation function, including all leading-order contributions for the first time. We find that the impact on the baryon Acoustic Oscillation (BAO) peak is dramatically enhanced (by a factor of ∼5) over the results of previous investigations, with the primary new effect due to advection: if a galaxy retains memory of the primordial streaming velocity, it does so at its Lagrangian, rather than Eulerian, position. Since correlations in the streaming velocity change rapidly at the BAO scale, this advection term can cause a significant shift in the observed BAO position. If streaming velocities impact tracer density at the 1% level, compared to the linear bias, the recovered BAO scale is shifted by approximately 0.5%. This new effect, which is required to preserve Galilean invariance, greatly increases the importance of including streaming velocities in the analysis of upcoming BAO measurements and opens a new window to the astrophysics of galaxy formation.
