We present the integrated 3-point correlation functions (3PCF) involving both
the cosmic shear and the galaxy density fields. These are a set of higher-order
statistics that describe the modulation ...of local 2-point correlation functions
(2PCF) by large-scale features in the fields, and which are easy to measure
from galaxy imaging surveys. Based on previous works on the shear-only
integrated 3PCF, we develop the theoretical framework for modelling 5 new
statistics involving the galaxy field and its cross-correlations with cosmic
shear. Using realistic galaxy and cosmic shear mocks from simulations, we
determine the regime of validity of our models based on leading-order standard
perturbation theory with an MCMC analysis that recovers unbiased constraints of
the amplitude of fluctuations parameter $A_s$ and the linear and quadratic
galaxy bias parameters $b_1$ and $b_2$. Using Fisher matrix forecasts for a
DES-Y3-like survey, relative to baseline analyses with conventional
3$\times$2PCFs, we find that the addition of the shear-only integrated 3PCF can
improve cosmological parameter constraints by $20-40\%$. The subsequent
addition of the new statistics introduced in this paper can lead to further
improvements of $10-20\%$, even when utilizing only conservatively large scales
where the tree-level models are valid. Our results motivate future work on the
galaxy and shear integrated 3PCFs, which offer a practical way to extend
standard analyses based on 3$\times$2PCFs to systematically probe the
non-Gaussian information content of cosmic density fields.
Using HST WFPC2 V- and R-band data of the z=0.37 cluster MS 1512+36, we show that the z=2.72 ‘protogalaxy’ cB58 is not extraordinarily luminous intrinsically but lensed into a gravitational fold arc ...by the cluster. The arc has a surface- brightness-weighted axis ratio of 1:7, is marginally resolved in width and about 3 arcsec long. Its counterimage was identified and found to be very compact (r1/2=2.4–4.0 h−150 kpc in a q0=0.05 cosmology). In addition, we found three further multiple image systems, one with five and two with three images each. The positions of the multiple images can be explained by modelling the light deflection caused by the cluster and the cD galaxy with elliptical isothermal potentials. The major axis of the cluster potential approximately agrees with that of the cD light and that of the X-ray isophotes. As the multiple images are within ≈8 arcsec around the cD galaxy, a cluster core radius-cluster velocity dispersion degeneracy arises. Interpreting the observations conservatively, the cluster velocity dispersion and the core radius are limited to 540–670 km s−1 and 5–11 arcsec, respectively, and the brightness of the unlensed counterimage of cB58 is about 23.9±0.3 (R band), corresponding to a magnification- and extinction-corrected rest frame B-band absolute magnitude of -24.75±0.7 mag. The redshifts of the sources of the remaining three multiple image systems are predicted to be similar to that of cB58, while a strict upper limit of 4 is set as they are visible in B-band ground-based data. That part of the source of cB58 that is mapped into the arc is reconstructed and its magnification is found to be μarc≳50. This large magnification explains at least some of the untypical spectroscopic properties of cB58, e.g. that the star formation rate seems to be high and uniform and to take place in a large area.
We present the integrated 3-point shear correlation function \(i\zeta_{\pm}\) -- a higher-order statistic of the cosmic shear field -- which can be directly estimated in wide-area weak lensing ...surveys without measuring the full 3-point shear correlation function, making this a practical and complementary tool to 2-point statistics for weak lensing cosmology. We define it as the 1-point aperture mass statistic \(M_{\mathrm{ap}}\) measured at different locations on the shear field correlated with the corresponding local 2-point shear correlation function \(\xi_{\pm}\). Building upon existing work on the integrated bispectrum of the weak lensing convergence field, we present a theoretical framework for computing the integrated 3-point function in real space for any projected field within the flat-sky approximation and apply it to cosmic shear. Using analytical formulae for the non-linear matter power spectrum and bispectrum, we model \(i\zeta_{\pm}\) and validate it on N-body simulations within the uncertainties expected from the sixth year cosmic shear data of the Dark Energy Survey. We also explore the Fisher information content of \(i\zeta_{\pm}\) and perform a joint analysis with \(\xi_{\pm}\) for two tomographic source redshift bins with realistic shape-noise to analyse its power in constraining cosmological parameters. We find that the joint analysis of \(\xi_{\pm}\) and \(i\zeta_{\pm}\) has the potential to considerably improve parameter constraints from \(\xi_{\pm}\) alone, and can be particularly useful in improving the figure of merit of the dynamical dark energy equation of state parameters from cosmic shear data.
We present the integrated 3-point correlation functions (3PCF) involving both the cosmic shear and the galaxy density fields. These are a set of higher-order statistics that describe the modulation ...of local 2-point correlation functions (2PCF) by large-scale features in the fields, and which are easy to measure from galaxy imaging surveys. Based on previous works on the shear-only integrated 3PCF, we develop the theoretical framework for modelling 5 new statistics involving the galaxy field and its cross-correlations with cosmic shear. Using realistic galaxy and cosmic shear mocks from simulations, we determine the regime of validity of our models based on leading-order standard perturbation theory with an MCMC analysis that recovers unbiased constraints of the amplitude of fluctuations parameter \(A_s\) and the linear and quadratic galaxy bias parameters \(b_1\) and \(b_2\). Using Fisher matrix forecasts for a DES-Y3-like survey, relative to baseline analyses with conventional 3\(\times\)2PCFs, we find that the addition of the shear-only integrated 3PCF can improve cosmological parameter constraints by \(20-40\%\). The subsequent addition of the new statistics introduced in this paper can lead to further improvements of \(10-20\%\), even when utilizing only conservatively large scales where the tree-level models are valid. Our results motivate future work on the galaxy and shear integrated 3PCFs, which offer a practical way to extend standard analyses based on 3\(\times\)2PCFs to systematically probe the non-Gaussian information content of cosmic density fields.
Photometric redshift uncertainties are a major source of systematic error for ongoing and future photometric surveys. We study different sources of redshift error caused by choosing a suboptimal ...redshift histogram bin width and propose methods to resolve them. The selection of a too large bin width is shown to oversmooth small scale structure of the radial distribution of galaxies. This systematic error can significantly shift cosmological parameter constraints by up to \(6 \, \sigma\) for the dark energy equation of state parameter \(w\). Careful selection of bin width can reduce this systematic by a factor of up to 6 as compared with commonly used current binning approaches. We further discuss a generalised resampling method that can correct systematic and statistical errors in cosmological parameter constraints caused by uncertainties in the redshift distribution. This can be achieved without any prior assumptions about the shape of the distribution or the form of the redshift error. Our methodology allows photometric surveys to obtain unbiased cosmological parameter constraints using a minimum number of spectroscopic calibration data. For a DES-like galaxy clustering forecast we obtain unbiased results with respect to errors caused by suboptimal histogram bin width selection, using only 5k representative spectroscopic calibration objects per tomographic redshift bin.
Using the M31 PAndromeda Cepheid sample and the HST PHAT data we obtain the largest Cepheid sample in M31 with HST data in four bands. For our analysis we consider three samples: A very homogeneous ...sample of Cepheids based on the PAndromeda data, the mean magnitude corrected PAndromeda sample and a sample complementing the PAndromeda sample with Cepheids from literature. The latter results in the largest catalog with 522 fundamental mode (FM) Cepheids and 102 first overtone (FO) Cepheids with F160W and F110W data and 559 FM Cepheids and 111 FO Cepheids with F814W and F475W data. The obtained dispersion of the Period-Luminosity relations (PLRs) is very small (e.g. 0.138 mag in the F160W sample I PLR). We find no broken slope in the PLRs when analyzing our entire sample, but we do identify a subsample of Cepheids that causes the broken slope. However, this effect only shows when the number of this Cepheid type makes up a significant fraction of the total sample. We also analyze the sample selection effect on the Hubble constant.
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