Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userThe Mass-Richness Relation of MaxBCG Clusters from Quasar Lensing Magnification using Variability
251
0
0.0
(
0
)
Ask ChatGPT about the research
No Arabic abstract
Accurate measurement of galaxy cluster masses is an essential component not only in studies of cluster physics, but also for probes of cosmology. However, different mass measurement techniques frequently yield discrepant results. The SDSS MaxBCG catalogs mass-richness relation has previously been constrained using weak lensing shear, Sunyaev-Zeldovich (SZ), and X-ray measurements. The mass normalization of the clusters as measured by weak lensing shear is >~25% higher than that measured using SZ and X-ray methods, a difference much larger than the stated measurement errors in the analyses. We constrain the mass-richness relation of the MaxBCG galaxy cluster catalog by measuring the gravitational lensing magnification of type I quasars in the background of the clusters. The magnification is determined using the quasars variability and the correlation between quasars variability amplitude and intrinsic luminosity. The mass-richness relation determined through magnification is in agreement with that measured using shear, confirming that the lensing strength of the clusters implies a high mass normalization, and that the discrepancy with other methods is not due to a shear-related systematic measurement error. We study the dependence of the measured mass normalization on the cluster halo orientation. As expected, line-of-sight clusters yield a higher normalization; however, this minority of haloes does not significantly bias the average mass-richness relation of the catalog.
rate research
Read More
We present a statistical weak-lensing magnification analysis on an optically selected sample of 3029 texttt{CAMIRA} galaxy clusters with richness $N>15$ at redshift $0.2leq z <1.1$ in the Subaru Hyper Suprime-Cam (HSC) survey. We use two distinct populations of color-selected, flux-limited background galaxies, namely the low-$z$ and high-$z$ samples at mean redshifts of $approx1.1$ and $approx1.4$, respectively, from which to measure the weak-lensing magnification signal by accounting for cluster contamination as well as masking effects. Our magnification bias measurements are found to be uncontaminated according to validation tests against the null-test samples for which the net magnification bias is expected to vanish. The magnification bias for the full texttt{CAMIRA} sample is detected at a significance level of $9.51sigma$, which is dominated by the high-$z$ background. We forward-model the observed magnification data to constrain the normalization of the richness-to-mass ($N$--$M$) relation for the texttt{CAMIRA} sample with informative priors on other parameters. The resulting scaling relation is $Npropto {M_{500}}^{0.92pm0.13} (1 + z)^{-0.48pm0.69}$, with a characteristic richness of $N=left(17.72pm2.60right)$ and intrinsic log-normal scatter of $0.15pm0.07$ at $M_{500} = 10^{14}h^{-1}M_{odot}$. With the derived $N$--$M$ relation, we provide magnification-calibrated mass estimates of individual texttt{CAMIRA} clusters, with the typical uncertainty of $approx39%$ and $approx32%$ at richness$approx20$ and $approx40$, respectively. We further compare our magnification-inferred $N$--$M$ relation with those from the shear-based results in the literature, finding good agreement.
Gravitational lensing magnification is measured with a significance of 9.7 sigma on a large sample of galaxy clusters in the Canada-France-Hawaii Telescope Lensing Survey (CFHTLenS). This survey covers ~154 deg^2 and contains over 18,000 cluster candidates at redshifts 0.2 <= z <= 0.9, detected using the 3D-Matched Filter cluster-finder of Milkeraitis et al. (2010). We fit composite-NFW models to the ensemble, accounting for cluster miscentering, source-lens redshift overlap, as well as nearby structure (the 2-halo term), and recover mass estimates of the cluster dark matter halos in range of ~10^13 M_sun to 2*10^14 M_sun. Cluster richness is measured for the entire sample, and we bin the clusters according to both richness and redshift. A mass-richness relation M_200 = M_0 (N_200 / 20)^beta is fit to the measurements. For two different cluster miscentering models we find consistent results for the normalization and slope, M_0 = (2.3 +/- 0.2)*10^13 M_sun, beta = 1.4 +/- 0.1 and M_0 = (2.2 +/- 0.2)*10^13 M_sun, beta = 1.5 +/- 0.1. We find that accounting for the full redshift distribution of lenses and sources is important, since any overlap can have an impact on mass estimates inferred from flux magnification.
We constrain the scaling relation between optical richness ($lambda$) and halo mass ($M$) for a sample of SDSS redMaPPer galaxy clusters within the context of the {it Planck} cosmological model. We use a forward modeling approach where we model the probability distribution of optical richness for a given mass, $P(ln lambda| M)$. To model the abundance and the stacked lensing profiles, we use an emulator specifically built to interpolate the halo mass function and the stacked lensing profile for an arbitrary set of halo mass and redshift, which is calibrated based on a suite of high-resolution $N$-body simulations. We apply our method to 8,312 SDSS redMaPPer clusters with $20le lambda le 100$ and $0.10le z_{lambda}le0.33$, and show that the log-normal distribution model for $P(lambda|M)$, with four free parameters, well reproduces the measured abundances and lensing profiles simultaneously. The constraints are characterized by the mean relation, $leftlangle ln{lambda}rightrangle(M)=A+Bln(M/M_{rm pivot})$, with $A=3.207^{+0.044}_{-0.046}$ and $B=0.993^{+0.041}_{-0.055}$ (68%~CL), where the pivot mass scale $M_{rm pivot}=3times 10^{14} h^{-1}M_odot$, and the scatter $sigma_{mathrm{lnlambda}|M}=sigma_0+qln(M/M_{rm pivot})$ with $sigma_0=0.456^{+0.047}_{-0.039}$ and $q=-0.169^{+0.035}_{-0.026}$. We find that a large scatter in halo masses is required at the lowest richness bins ($20le lambda lesssim 30$) in order to reproduce the measurements. Without such a large scatter, the model prediction for the lensing profiles tends to overestimate the measured amplitudes. This might imply a possible contamination of intrinsically low-richness clusters due to the projection effects. Such a low-mass halo contribution is significantly reduced when applying our method to the sample of $30le lambda le 100$.
We measure the logarithmic scatter in mass at fixed richness for clusters in the maxBCG cluster catalog, an optically selected cluster sample drawn from SDSS imaging data. Our measurement is achieved by demanding consistency between available weak lensing and X-ray measurements of the maxBCG clusters, and the X-ray luminosity--mass relation inferred from the 400d X-ray cluster survey, a flux limited X-ray cluster survey. We find sigma_{ln M|N_{200}}=0.45^{+0.20}_{-0.18} (95% CL) at N_{200} ~ 40, where N_{200} is the number of red sequence galaxies in a cluster. As a byproduct of our analysis, we also obtain a constraint on the correlation coefficient between ln Lx and ln M at fixed richness, which is best expressed as a lower limit, r_{L,M|N} >= 0.85 (95% CL). This is the first observational constraint placed on a correlation coefficient involving two different cluster mass tracers. We use our results to produce a state of the art estimate of the halo mass function at z=0.23 -- the median redshift of the maxBCG cluster sample -- and find that it is consistent with the WMAP5 cosmology. Both the mass function data and its covariance matrix are presented.
We introduce a technique to measure gravitational lensing magnification using the variability of type I quasars. Quasars variability amplitudes and luminosities are tightly correlated, on average. Magnification due to gravitational lensing increases the quasars apparent luminosity, while leaving the variability amplitude unchanged. Therefore, the mean magnification of an ensemble of quasars can be measured through the mean shift in the variability-luminosity relation. As a proof of principle, we use this technique to measure the magnification of quasars spectroscopically identified in the Sloan Digital Sky Survey, due to gravitational lensing by galaxy clusters in the SDSS MaxBCG catalog. The Palomar-QUEST Variability Survey, reduced using the DeepSky pipeline, provides variability data for the sources. We measure the average quasar magnification as a function of scaled distance (r/R200) from the nearest cluster; our measurements are consistent with expectations assuming NFW cluster profiles, particularly after accounting for the known uncertainty in the clusters centers. Variability-based lensing measurements are a valuable complement to shape-based techniques because their systematic errors are very different, and also because the variability measurements are amenable to photometric errors of a few percent and to depths seen in current wide-field surveys. Given the data volume expected from current and upcoming surveys, this new technique has the potential to be competitive with weak lensing shear measurements of large scale structure.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
