Bispectrum as Baryon Acoustic Oscillation Interferometer

The galaxy bispectrum, measuring excess clustering of galaxy triplets, offers a probe of dark energy via baryon acoustic oscillations (BAOs). However up to now it has been severely underused due to the combinatorically explosive number of triangles. Here we exploit interference in the bispectrum to identify triangles that amplify BAOs. This approach reduces the computational cost of estimating covariance matrices, offers an improvement in BAO constraints equivalent to lengthening BOSS by 30%, and simplifies adding bispectrum BAO information to future large-scale redshift survey analyses.Comment: 6 pages, 3 figures; revised to match published versio

Robustness of Baryon Acoustic Oscillations Measurements with Photometric Redshift Uncertainties

We investigate the robustness of baryon acoustic oscillations (BAO) measurements with a photometric galaxy sample using mock galaxy catalogs with various sizes of photometric redshift (photo-$z$) uncertainties. We first investigate the robustness of BAO measurements, assuming we have a perfect knowledge of photo-$z$ uncertainties. We find that the BAO shift parameter $\alpha$ can be constrained in an unbiased manner for various sizes of photometric redshift uncertainties at $z=0.251$, $0.617$, and $1.03$ as long as the number density of galaxies is high. A sparse galaxy sample causes additional noise in the covariance matrix calculation and it can bias the constraint on $\alpha$. Next, we investigate the scenario where incorrect photometric redshift uncertainties are assumed in the fitting model and find that underestimating the photo-$z$ uncertainty leads to a degradation in the constraining power on $\alpha$. In addition, we investigate BAO measurements with a cross-correlation signal between a spec-$z$ sample and a photo-$z$ sample. We find BAO constraints are unbiased and slightly tighter than the auto-correlation signal of a photo-$z$ sample. We also quantify the constraining power on $\Omega_{\rm m0}$ assuming the LSST-like covariance and find that the 95\% confidence level is $\sigma(\Omega_{\rm m0})\sim0.03$-$0.05$ corresponding to the photo-$z$ uncertainties of 1\% to 3\% respectively. Finally, we examine whether the skewness in the photometric redshift can bias the constraint on $\alpha$ and confirm that the constraint on $\alpha$ is unbiased even if we use a fitting model assuming a Gaussian photo-$z$ uncertainty.Comment: 10 pages, 11 figures, 3 table

Galaxy-galaxy weak-lensing measurement from SDSS: II. host halo properties of galaxy groups

As the second paper of a series on studying galaxy-galaxy lensing signals using the Sloan Digital Sky Survey Data Release 7 (SDSS DR7), we present our measurement and modelling of the lensing signals around groups of galaxies. We divide the groups into four halo mass bins, and measure the signals around four different halo-center tracers: brightest central galaxy (BCG), luminosity-weighted center, number-weighted center and X-ray peak position. For X-ray and SDSS DR7 cross identified groups, we further split the groups into low and high X-ray emission subsamples, both of which are assigned with two halo-center tracers, BCGs and X-ray peak positions. The galaxy-galaxy lensing signals show that BCGs, among the four candidates, are the best halo-center tracers. We model the lensing signals using a combination of four contributions: off-centered NFW host halo profile, sub-halo contribution, stellar contribution, and projected 2-halo term. We sample the posterior of 5 parameters i.e., halo mass, concentration, off-centering distance, sub halo mass, and fraction of subhalos via a MCMC package using the galaxy-galaxy lensing signals. After taking into account the sampling effects (e.g. Eddington bias), we found the best fit halo masses obtained from lensing signals are quite consistent with those obtained in the group catalog based on an abundance matching method, except in the lowest mass bin. Subject headings: (cosmology:) gravitational lensing, galaxies: clusters: generalComment: 12 pages, 7 figures, submitted to Ap

Dark Energy Survey Year 1 Clusters are Consistent with Planck

The recent Dark Energy Survey Year 1 (DES-Y1) analysis of galaxy cluster abundances and weak lensing produced $\Omega_{\rm m}$ and $\sigma_8$ constraints in 5.6$\sigma$ tension with Planck. It is suggested in that work that this tension is driven by unmodelled systematics in optical cluster selection. We present a novel simulation-based forward modeling framework that explicitly incorporates cluster selection into its model predictions. Applying this framework to the DES-Y1 data we find consistency with Planck, resolving the tension found in the DES-Y1 analysis. An extension of this approach to the final DES data set will produce robust constraints on $\Lambda$CDM parameters and correspondingly strong tests of cosmological models.Comment: 6 pages, 2 figures, 1 table, Supplemental material with 2 figures. Submitted to Physical Review Letter

Mitigating the impact of fiber assignment on clustering measurements from deep galaxy redshift surveys

We examine the impact of fiber assignment on clustering measurements from fiber-fed spectroscopic galaxy surveys. We identify new effects which were absent in previous, relatively shallow galaxy surveys such as Baryon Oscillation Spectroscopic Survey . Specifically, we consider deep surveys covering a wide redshift range from z=0.6 to z=2.4, as in the Subaru Prime Focus Spectrograph survey. Such surveys will have more target galaxies than we can place fibers on. This leads to two effects. First, it eliminates fluctuations with wavelengths longer than the size of the field of view, as the number of observed galaxies per field is nearly fixed to the number of available fibers. We find that we can recover the long-wavelength fluctuation by weighting galaxies in each field by the number of target galaxies. Second, it makes the preferential selection of galaxies in under-dense regions. We mitigate this effect by weighting galaxies using the so-called individual inverse probability. Correcting these two effects, we recover the underlying correlation function at better than 1 percent accuracy on scales greater than 10 Mpc/h.Comment: 17 pages, 11 figure

Emergent gravity fails to explain color-dependent galaxy-galaxy lensing signals from SDSS Dr7

We test the Emergent Gravity(EG) theory using the galaxy-galaxy lensing technique based on SDSS DR7 data. In the EG scenario, we do not expect color dependence of the galaxy sample in the 'apparent dark matter' predicted by EG, which is exerted only by the baryonic mass. If the baryonic mass is similar, then the predicted lensing profiles from the baryonic mass should be similar according to the EG, regardless of the color of the galaxy sample. We use the stellar mass of the galaxy as a proxy of its baryonic mass. We divide our galaxy sample into 5 stellar mass bins, and further classify them as red and blue subsamples in each stellar mass bin. If we set halo mass and concentration as free parameters, $\Lambda$CDM is favored by our data in terms of the reduced $\chi^2$ while EG fails to explain the color dependence of ESDs from the galaxy-galaxy lensing measurement.Comment: 7 pages, 3 figures. Accepted by Ap