324 research outputs found
Modeling the Anisotropic Two-Point Galaxy Correlation Function on Small Scales and Improved Measurements of H(z), D_A(z), and f(z)sigma_8(z) from the Sloan Digital Sky Survey DR7 Luminous Red Galaxies
We present a simple and efficient phenomenological model for the
two-dimensional two-point galaxy correlation function that works well over a
wide range of scales, from large scales down to scales as small as 25Mpc/h. Our
model incorporates nonlinear effects, a scale-dependent galaxy bias on small
scales, and allows the redshift-space distortions to be scale and direction
dependent. We validate our model using LasDamas mock catalogs, and apply it to
the Sloan Digital Sky Survey (SDSS) DR7 Luminous Red Galaxies (LRGs). Using
only the monopole and quadrupole of the correlation function measured from the
SDSS DR7 LRGs, we obtain improved measurements H(z)r_s(z_d)/c=0.0433\pm 0.0042,
D_A(z)/r_s(z_d)=6.59\pm 0.46, and f(z)sigma_8(z)=0.429\pm 0.089 at z=0.35,
using the scale range of 25<s<120Mpc/h. We expect our results and model to be
useful in tightening dark energy and gravity constraints from the full analysis
of current and future galaxy clustering data.Comment: 9 pages, 5 figures, accepted by MNRAS, the last version matches
accepted one. arXiv admin note: substantial text overlap with
arXiv:1205.5573, arXiv:1102.225
Using Multipoles of the Correlation Function to Measure H(z), D_A(z), and \beta(z) from Sloan Digital Sky Survey Luminous Red Galaxies
Galaxy clustering data can be used to measure the cosmic expansion history
H(z), the angular-diameter distance D_A(z), and the linear redshift-space
distortion parameter beta(z). Here we present a method for using effective
multipoles of the galaxy two-point correlation function (\xi_0(s), \xi_2(s),
\xi}_4(s), and \xi_6(s), with s denoting the comoving separation) to measure
H(z), D_A(z)$, and beta(z), and validate it using LasDamas mock galaxy
catalogs. Our definition of effective multipoles explicitly incorporates the
discreteness of measurements, and treats the measured correlation function and
its theoretical model on the same footing. We find that for the mock data,
\xi_0+\xi_2+\xi_4 captures nearly all the information, and gives significantly
stronger constraints on H(z), D_A(z), and beta(z), compared to using only
\xi_0+\xi_2.
We apply our method to the sample of luminous red galaxies (LRGs) from the
Sloan Digital Sky Survey (SDSS) Data Release 7 (DR7) without assuming a dark
energy model or a flat Universe. We find that \xi}_4(s) deviates on scales of
s<60Mpc/h from the measurement from mock data (in contrast to \xi_0(s),
\xi_2(s), and \xi_6(s)), thus we only use \xi_0+\xi_2 for our fiducial
constraints. We obtain {H(0.35), D_A(0.35), Omega_mh^2, beta(z)} =
{79.6_{-8.7}^{+8.3} km/s/Mpc, 1057_{-87}^{+88}Mpc, 0.103\pm0.015, 0.44\pm0.15}
using \xi_0+\xi_2. We find that H(0.35)r_s(z_d)/c and D_A(0.35)/r_s(z_d) (where
r_s(z_d) is the sound horizon at the drag epoch) are more tightly constrained:
{H(0.35)r_s(z_d)/c, D_A(0.35)/r_s(z_d)} = {0.0437_{-0.0043}^{+0.0041},
6.48_{-0.43}^{+0.44}\} using \xi_0+\xi_2.Comment: 12 pages, 11 figures. arXiv admin note: substantial text overlap with
arXiv:1102.225
Probing Dark Energy Using Galaxy Clustering Data
Dark energy is the most important unsolved mystery in cosmology today. Galaxy clustering provides one of the prime probes of dark energy. This work is focused on developing robust analysis techniques for interpreting galaxy clustering data. These are crucial for probing dark energy using galaxy clustering data.First, we present a method to measure the effective distance to z=0.35, DV(0.35) from the overall shape of the spherically-averaged two-point correlation function (2PCF) of the Sloan Digital Sky Survey Data Release 7 luminous red galaxy sample. We find DV(0.35) = 1428-73+74Mpc without assuming a dark energy model or a flat Universe. We find that the derived measurement of rs(zd)/DV(0.35) = 0.1143 ± 0.0030 (the ratio of the sound horizon at the drag epoch to the effective distance to z=0.35) has tighter constraint and is more robust with respect to possible systematic effects. It is also nearly uncorrelated to Ωm h^2 which might be sensitive to systematic effects.Then, we generalize the method to measure the Hubble parameter, H(z), and angular diameter distance, DA(z), from the two-dimensional 2PCF, and we find H(0.35) = 82.1-4.9+4.8km/s/Mpc, DA(0.35)=1048-58+60Mpc. We also find that the derived measurements of {H(0.35)rs(zd), rs(zd)/DA(0.35)} = {13020 ± 530 km/s, 0.1518 ± 0.0062} (with the correlation coefficient r = -0.0584) are nearly uncorrelated, have tighter constraints and are more robust with respect to possible systematic effects. Combining our results with the cosmic microwave background and supernova data, we obtain Ωk=-0.0004 ± 0.0070 and w=-0.996 ± 0.043 (assuming a constant dark energy equation of state).Our results represent the first measurements of H(z) and DA(z) from galaxy clustering data. Our work has significant implications for future surveys in establishing the feasibility of measuring both H(z) and DA(z) from galaxy clustering data
Completed SDSS-IV extended baryon oscillation spectroscopic survey: cosmological implications from two decades of spectroscopic surveys at the Apache Point Observatory
Artículo escrito por un elevado número de autores, solo se referencian el que aparece en primer lugar, los autores pertenecientes a la UAM y el nombre del grupo de colaboración, si lo hubiereTítulo del la versión editorial: The Completed SDSS-IV extended Baryon Oscillation Spectroscopic Survey:
Cosmological Implications from two Decades of Spectroscopic Surveys at the Apache
Point observator
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