Abstract
General relativistic effects have long been predicted to subtly influence the observed large-scale structure of the universe. The current generation of galaxy redshift surveys has reached a ...size where detection of such effects is becoming feasible. In this paper, we report the first detection of the redshift asymmetry from the cross-correlation function of two galaxy populations that is consistent with relativistic effects. The data set is taken from the Sloan Digital Sky Survey Data Release 12 CMASS galaxy sample, and we detect the asymmetry at the 2.7σ level by applying a shell-averaged estimator to the cross-correlation function. Our measurement dominates at scales around 10 h
−1 Mpc, larger than those over which the gravitational redshift profile has been recently measured in galaxy clusters, but smaller than scales for which linear perturbation theory is likely to be accurate. The detection significance varies by 0.5σ with the details of our measurement and tests for systematic effects. We have also devised two null tests to check for various survey systematics and show that both results are consistent with the null hypothesis. We measure the dipole moment of the cross-correlation function, and from this the asymmetry is also detected, at the 2.8σ level. The amplitude and scale dependence of the clustering asymmetries are approximately consistent with the expectations of general relativity and a biased galaxy population, within large uncertainties. We explore theoretical predictions using numerical simulations in a companion paper.
ABSTRACT Quasar emission lines are often shifted from the systemic velocity due to various dynamical and radiative processes in the line-emitting region. The level of these velocity shifts depends ...both on the line species and on quasar properties. We study velocity shifts for the line peaks (not the centroids) of various narrow and broad quasar emission lines relative to systemic using a sample of 849 quasars from the Sloan Digital Sky Survey Reverberation Mapping (SDSS-RM) project. The coadded (from 32 epochs) spectra of individual quasars have sufficient signal-to-noise ratio (S/N) to measure stellar absorption lines to provide reliable systemic velocity estimates, as well as weak narrow emission lines. The large dynamic range in quasar luminosity (∼2 dex) of the sample allowed us to explore potential luminosity dependence of the velocity shifts. We derive average line peak velocity shifts as a function of quasar luminosity for different lines, and quantify their intrinsic scatter. We further quantify how well the peak velocity can be measured as a function of continuum S/N, and demonstrate that there is no systematic bias in the velocity measurements when S/N is degraded to as low as ∼3 per SDSS pixel ( ). Based on the observed line shifts, we provide empirical guidelines on redshift estimation from O ii , O iii , Ne v , Mg ii, C iii, He ii , broad Hβ, C iv, and Si iv, which are calibrated to provide unbiased systemic redshifts in the mean, but with increasing intrinsic uncertainties of 46, 56, 119, 205, 233, 242, 400, 415, and 477 , in addition to the measurement uncertainties. These results demonstrate the infeasibility of measuring quasar redshifts to better than with only broad lines.
We analyse the anisotropic clustering of the Baryon Oscillation Spectroscopic Survey CMASS Data Release 11 sample, which consists of 690 827 galaxies in the redshift range 0.43 < z < 0.70 and has a ...sky coverage of 8498 deg2 corresponding to an effective volume of ∼ 6 Gpc3. We fit the Fourier space statistics, the power spectrum and bispectrum monopoles to measure the linear and quadratic bias parameters, b
1 and b
2, for a non-linear non-local bias model, the growth of structure parameter f and the amplitude of dark matter density fluctuations parametrized by σ8. We obtain b
1(z
eff)1.40σ8(z
eff) = 1.672 ± 0.060 and
$b_2^{0.30}(z_{\rm eff})\sigma _8(z_{\rm eff})=0.579\pm 0.082$
at the effective redshift of the survey, z
eff = 0.57. The main cosmological result is the constraint on the combination f 0.43(z
eff)σ8(z
eff) = 0.582 ± 0.084, which is complementary to fσ8 constraints obtained from two-point redshift-space distortion analyses. A less conservative analysis yields f 0.43(z
eff)σ8(z
eff) = 0.584 ± 0.051. We ensure that our result is robust by performing detailed systematic tests using a large suite of survey galaxy mock catalogues and N-body simulations. The constraints on f 0.43σ8 are useful for setting additional constraints on neutrino mass, gravity, curvature as well as the number of neutrino species from galaxy surveys analyses (as presented in a companion paper).
We measure the two-point clustering of spectroscopically confirmed quasars from the final sample of the Baryon Oscillation Spectroscopic Survey (BOSS) on comoving scales of 4 ≲ s ≲ 22 h
−1 Mpc. The ...sample covers 6950 deg2 ∼ 19 (h
− 1Gpc)3 and, over the redshift range 2.2 ≤ z ≤ 2.8, contains 55 826 homogeneously selected quasars, which is twice as many as in any similar work. We deduce b
Q = 3.54 ± 0.10; the most precise measurement of quasar bias to date at these redshifts. This corresponds to a host halo mass of ∼2 × 1012 h
−1 M⊙ with an implied quasar duty cycle of ∼1 per cent. The real-space projected correlation function is well fitted by a power law of index 2 and correlation length r
0 = (8.12 ± 0.22) h
− 1 Mpc over scales of 4 ≲ r
p ≲ 25 h
−1 Mpc. To better study the evolution of quasar clustering at moderate redshift, we extend the redshift range of our study to z ∼ 3.4 and measure the bias and correlation length of three subsamples over 2.2 ≤ z ≤ 3.4. We find no significant evolution of r
0 or bias over this range, implying that the host halo mass of quasars decreases somewhat with increasing redshift. We find quasar clustering remains similar over a decade in luminosity, contradicting a scenario in which quasar luminosity is monotonically related to halo mass at z ≈ 2.5. Our results are broadly consistent with previous BOSS measurements, but they yield more precise constraints based upon a larger and more uniform data set.
We present a detailed characterization of the 849 broad-line quasars from the Sloan Digital Sky Survey Reverberation Mapping (SDSS-RM) project. Our quasar sample covers a redshift range of 0.1 < z < ...4.5 and is flux-limited to iPSF < 21.7 without any other cuts on quasar properties. The main sample characterization includes: (1) spectral measurements of the continuum and broad emission lines for individual objects from the coadded first-season spectroscopy in 2014, (2) identification of broad and narrow absorption lines in the spectra, and (3) optical variability properties for continuum and broad lines from multi-epoch spectroscopy. We provide improved systemic redshift estimates for all quasars and demonstrate the effects of the signal-to-noise ratio on the spectral measurements. We compile measured properties for all 849 quasars along with supplemental multi-wavelength data for subsets of our sample from other surveys. The SDSS-RM sample probes a diverse range in quasar properties and shows well-detected continuum and broad-line variability for many objects from first-season monitoring data. The compiled properties serve as the benchmark for follow-up work based on SDSS-RM data. The spectral fitting tools are made public along with this work.
We investigate the anisotropic clustering of the Baryon Oscillation Spectroscopic Survey (BOSS) Data Release 12 sample, which consists of 1198 006 galaxies in the redshift range 0.2 < z < 0.75 and a ...sky coverage of 10 252 deg2. We analyse this data set in Fourier space, using the power-spectrum multipoles to measure redshift-space distortions simultaneously with the Alcock-Paczynski effect and the baryon acoustic oscillation scale. We include the power-spectrum monopole, quadrupole and hexadecapole in our analysis and compare our measurements with a perturbation-theory-based model, while properly accounting for the survey window function. To evaluate the reliability of our analysis pipeline, we participate in a mock challenge, which results in systematic uncertainties significantly smaller than the statistical uncertainties. While the high-redshift constraint on fs8 at zeff = 0.61 indicates a small (~1.4s) deviation from the prediction of the Planck ...CDM (... cold dark matter) model, the low-redshift constraint is in good agreement with Planck ...CDM. This paper is part of a set that analyses the final galaxy clustering data set from BOSS. The measurements and likelihoods presented here are combined with others in Alam et al. to produce the final cosmological constraints from BOSS. (ProQuest: ... denotes formulae/symbols omitted.)
We present a sample of 120 dust-reddened quasars identified by matching radio sources detected at 1.4 GHz in the Faint Images of the Radio Sky at Twenty Centimeters survey with the near-infrared Two ...Micron All Sky Survey catalog and color-selecting red sources. Optical and/or near-infrared spectroscopy provide broad wavelength sampling of their spectral energy distributions that we use to determine their reddening, characterized by E(B - V). We demonstrate that the reddening in these quasars is best described by Small-Magellanic-Cloud-like dust. This sample spans a wide range in redshift and reddening (0.1 lap z lap 3, 0.1 lap E(B - V) lap 1.5), which we use to investigate the possible correlation of luminosity with reddening. At every redshift, dust-reddened quasars are intrinsically the most luminous quasars. We interpret this result in die context of merger-driven quasar/galaxy coevolution where these reddened quasars are revealing an emergent phase during which the heavily obscured quasar is shedding its cocoon of dust prior to becoming a "normal" blue quasar. When correcting for extinction, we find that, depending on how the parent population is defined, these red quasars make up lap 15%-20% of the luminous quasar population. We estimate, based on the fraction of objects in this phase, that its duration is 15%-20% as long as the unobscured, blue quasar phase.
We study the effects of filaments on galaxy properties in the Sloan Digital Sky Survey (SDSS) Data Release 12 using filaments from the 'Cosmic Web Reconstruction' catalogue, a publicly available ...filament catalogue for SDSS. Since filaments are tracers of medium- to high-density regions, we expect that galaxy properties associated with the environment are dependent on the distance to the nearest filament. Our analysis demonstrates that a red galaxy or a high-mass galaxy tends to reside closer to filaments than a blue or low-mass galaxy. After adjusting the effect from stellar mass, on average, early-forming galaxies or large galaxies have a shorter distance to filaments than late-forming galaxies or small galaxies. For the main galaxy sample, all signals are very significant (>6 sigma ). For the LOWZ and CMASS sample, the stellar mass and size are significant (>2 sigma ). The filament effects we observe persist until z = 0.7 (the edge of the CMASS sample). Comparing our results to those using the galaxy distances from redMaPPer galaxy clusters as a reference, we find a similar result between filaments and clusters. Moreover, we find that the effect of clusters on the stellar mass of nearby galaxies depends on the galaxy's filamentary environment. Our findings illustrate the strong correlation of galaxy properties with proximity to density ridges, strongly supporting the claim that density ridges are good tracers of filaments.
We present an anisotropic analysis of the baryon acoustic oscillation (BAO) scale in the twelfth and final data release of the Baryon Oscillation Spectroscopic Survey (BOSS). We independently analyse ...the LOWZ and CMASS galaxy samples: the LOWZ sample contains 361 762 galaxies with an effective redshift of z
LOWZ = 0.32; the CMASS sample consists of 777 202 galaxies with an effective redshift of z
CMASS = 0.57. We extract the BAO peak position from the monopole power-spectrum moment, α0, and from the μ2 moment, α2, where μ is the cosine of the angle to the line of sight. The μ2-moment provides equivalent information to that available in the quadrupole but is simpler to analyse. After applying a reconstruction algorithm to reduce the BAO suppression by bulk motions, we measure the BAO peak position in the monopole and μ2-moment, which are related to radial and angular shifts in scale. We report H(z
LOWZ)r
s(z
d) = (11.60 ± 0.60) × 103 km s−1 and D
A(z
LOWZ)/r
s(z
d) = 6.66 ± 0.16 with a cross-correlation coefficient of
$r_{HD_{\rm A}}=0.41$
, for the LOWZ sample; and H(z
CMASS)r
s(z
d) = (14.56 ± 0.37) × 103 km s−1 and D
A(z
CMASS)/r
s(z
d) = 9.42 ± 0.13 with a cross-correlation coefficient of
$r_{HD_{\rm A}}=0.47$
, for the CMASS sample. We demonstrate that our results are not affected by the fiducial cosmology assumed for the analysis. We combine these results with the measurements of the BAO peak position in the monopole and quadrupole correlation function of the same data set (Cuesta et al. 2016, companion paper) and report the consensus values: H(z
LOWZ)r
s(z
d) = (11.63 ± 0.69) × 103 km s−1 and D
A(z
LOWZ)/r
s(z
d) = 6.67 ± 0.15 with
$r_{HD_{\rm A}}=0.35$
for the LOWZ sample; H(z
CMASS)r
s(z
d) = (14.67 ± 0.42) × 103 km s−1 and D
A(z
CMASS)/r
s(z
d) = 9.47 ± 0.12 with
$r_{HD_{\rm A}}=0.52$
for the CMASS sample.
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