scholarly journals CFHTLenS and RCSLenS: testing photometric redshift distributions using angular cross-correlations with spectroscopic galaxy surveys

2016 ◽  
Vol 463 (4) ◽  
pp. 3737-3754 ◽  
Author(s):  
A. Choi ◽  
C. Heymans ◽  
C. Blake ◽  
H. Hildebrandt ◽  
C. A. J. Duncan ◽  
...  
Keyword(s):  
Galaxy Surveys ◽  
Photometric Redshift ◽  
Cross Correlations

scholarly journals ANNz2 - Photometric redshift and probability density function estimation using machine-learning

2014 ◽  
Vol 10 (S306) ◽  
pp. 316-318
Author(s):  
Iftach Sadeh
Keyword(s):  
Machine Learning ◽  
Probability Density ◽  
Function Estimation ◽  
Photometric Redshifts ◽  
Galaxy Surveys ◽  
The Public ◽  
Photometric Redshift ◽  
Machine Learning Methods ◽  
Density Function Estimation ◽  
Full Probability

AbstractLarge photometric galaxy surveys allow the study of questions at the forefront of science, such as the nature of dark energy. The success of such surveys depends on the ability to measure the photometric redshifts of objects (photo-zs), based on limited spectral data. A new major version of the public photo-z estimation software, ANNz, is presented here. The new code incorporates several machine-learning methods, such as artificial neural networks and boosted decision/regression trees, which are all used in concert. The objective of the algorithm is to dynamically optimize the performance of the photo-z estimation, and to properly derive the associated uncertainties. In addition to single-value solutions, the new code also generates full probability density functions in two independent ways.

scholarly journals A joint analysis for cosmology and photometric redshift calibration using cross-correlations

2016 ◽  
Vol 466 (3) ◽  
pp. 3558-3568 ◽  
Author(s):  
Michael McLeod ◽  
Sreekumar T. Balan ◽  
Filipe B. Abdalla
Keyword(s):  
Joint Analysis ◽  
Photometric Redshift ◽  
Cross Correlations

scholarly journals Wide-angle effects on galaxy ellipticity correlations

2021 ◽  
Author(s):  
Maresuke Shiraishi ◽  
Atsushi Taruya ◽  
Teppei Okumura ◽  
Kazuyuki Akitsu
Keyword(s):  
Cosmological Parameters ◽  
Three Dimensional ◽  
New Physics ◽  
Opening Angle ◽  
Wide Angle ◽  
Galaxy Surveys ◽  
Point Correlation ◽  
Point Correlation Function ◽  
Cross Correlations ◽  
Three Dimensional Configuration

Abstract We show an efficient way to compute wide-angle or all-sky statistics of galaxy intrinsic alignment in three-dimensional configuration space. For this purpose, we expand the two-point correlation function using a newly introduced spin-dependent tripolar spherical harmonic basis. Therefore, the angular dependences on the two line-of-sight (LOS) directions pointing to each pair of objects, which are degenerate with each other in the conventional analysis under the small-angle or plane-parallel (PP) approximation, are unambiguously decomposed. By means of this, we, for the first time, compute the wide-angle auto and cross correlations between intrinsic ellipticities, number densities and velocities of galaxies, and compare them with the PP-limit results. For the ellipticity-ellipticity and density-ellipticity correlations, we find more than $10\%$ deviation from the PP-limit results if the opening angle between two LOS directions exceeds 30○ − 50○. It is also shown that even if the PP-limit result is strictly zero, the non-vanishing correlation is obtained over the various scales, arising purely from the curved-sky effects. Our results indicate the importance of the data analysis not relying on the PP approximation in order to determine the cosmological parameters more precisely and/or find new physics via ongoing and forthcoming wide-angle galaxy surveys.

scholarly journals Recent results and perspectives on cosmology and fundamental physics from microwave surveys

2016 ◽  
Vol 25 (06) ◽  
pp. 1630016
Author(s):  
Carlo Burigana ◽  
Elia Stefano Battistelli ◽  
Micol Benetti ◽  
Giovanni Cabass ◽  
Paolo De Bernardis ◽  
...  
Keyword(s):  
Particle Physics ◽  
Neutron Lifetime ◽  
Microwave Background ◽  
Fundamental Physics ◽  
Axion Mass ◽  
Galaxy Surveys ◽  
Primordial Power Spectrum ◽  
Cosmological Data ◽  
Cross Correlations ◽  
Standard Cosmological Model

Recent cosmic microwave background (CMB) data in temperature and polarization have reached high precision in estimating all the parameters that describe the current so-called standard cosmological model. Recent results about the integrated Sachs–Wolfe (ISW) effect from CMB anisotropies, galaxy surveys, and their cross-correlations are presented. Looking at fine signatures in the CMB, such as the lack of power at low multipoles, the primordial power spectrum (PPS) and the bounds on non-Gaussianities, complemented by galaxy surveys, we discuss inflationary physics and the generation of primordial perturbations in the early universe. Three important topics in particle physics, the bounds on neutrinos masses and parameters, on thermal axion mass and on the neutron lifetime derived from cosmological data are reviewed, with attention to the comparison with laboratory experiment results. Recent results from cosmic polarization rotation (CPR) analyses aimed at testing the Einstein equivalence principle (EEP) are presented. Finally, we discuss the perspectives of next radio facilities for the improvement of the analysis of future CMB spectral distortion experiments.

scholarly journals Mapping the Cosmic Web with the largest all-sky surveys

2014 ◽  
Vol 11 (S308) ◽  
pp. 143-148
Author(s):  
Maciej Bilicki ◽  
John A. Peacock ◽  
Thomas H. Jarrett ◽  
Michelle E. Cluver ◽  
Louise Steward
Keyword(s):  
Three Dimensional ◽  
Optical Data ◽  
Microwave Background ◽  
Sky Surveys ◽  
Photometric Redshift ◽  
Redshift Surveys ◽  
Cross Correlations ◽  
Galaxy Redshift ◽  
Celestial Sphere ◽  
The Universe

AbstractOur view of the low-redshift Cosmic Web has been revolutionized by galaxy redshift surveys such as 6dFGS, SDSS and 2MRS. However, the trade-off between depth and angular coverage limits a systematic three-dimensional account of the entire sky beyond the Local Volume (z< 0.05). In order to reliably map the Universe to cosmologically significant depths over the full celestial sphere, one must draw on multiwavelength datasets and state-of-the-art photometric redshift techniques. We have undertaken a dedicated program of cross-matching the largest photometric all-sky surveys – 2MASS, WISE and SuperCOSMOS – to obtain accurate redshift estimates of millions of galaxies. The first outcome of these efforts – the 2MASS Photometric Redshift catalog (2MPZ, Bilickiet al. 2014a) – has been publicly released and includes almost 1 million galaxies with a mean redshift ofz=0.08. Here we summarize how this catalog was constructed and how using the WISE mid-infrared sample together with SuperCOSMOS optical data allows us to push to redshift shells ofz∼ 0.2 –0.3 on unprecedented angular scales. Our catalogs, with ∼ 20 million sources in total, provide access to cosmological volumes crucial for studies of local galaxy flows (clustering dipole, bulk flow) and cross-correlations with the cosmic microwave background such as the integrated Sachs-Wolfe effect or lensing studies.

scholarly journals Evaluation of probabilistic photometric redshift estimation approaches for The Rubin Observatory Legacy Survey of Space and Time (LSST)

2020 ◽  
Author(s):  
S J Schmidt ◽  
A I Malz ◽  
J Y H Soo ◽  
I A Almosallam ◽  
M Brescia ◽  
...  
Keyword(s):  
Performance Metrics ◽  
Conditional Density ◽  
Galaxy Surveys ◽  
Photometric Redshift ◽  
Space And Time ◽  
Posterior Probability Density ◽  
Pdf Estimation ◽  
Template Library ◽  
Science Collaboration ◽  
The Impact

Abstract Many scientific investigations of photometric galaxy surveys require redshift estimates, whose uncertainty properties are best encapsulated by photometric redshift (photo-z) posterior probability density functions (PDFs). A plethora of photo-z PDF estimation methodologies abound, producing discrepant results with no consensus on a preferred approach. We present the results of a comprehensive experiment comparing twelve photo-z algorithms applied to mock data produced forLarge Synoptic Survey Telescope The Rubin Observatory Legacy Survey of Space and Time (lsst) Dark Energy Science Collaboration (desc). By supplying perfect prior information, in the form of the complete template library and a representative training set as inputs to each code, we demonstrate the impact of the assumptions underlying each technique on the output photo-z PDFs. In the absence of a notion of true, unbiased photo-z PDFs, we evaluate and interpret multiple metrics of the ensemble properties of the derived photo-z PDFs as well as traditional reductions to photo-z point estimates. We report systematic biases and overall over/under-breadth of the photo-z PDFs of many popular codes, which may indicate avenues for improvement in the algorithms or implementations. Furthermore, we raise attention to the limitations of established metrics for assessing photo-z PDF accuracy; though we identify the conditional density estimate (CDE) loss as a promising metric of photo-z PDF performance in the case where true redshifts are available but true photo-z PDFs are not, we emphasize the need for science-specific performance metrics.

scholarly journals Gaussian mixture models for blended photometric redshifts

2019 ◽  
Vol 490 (3) ◽  
pp. 3966-3986 ◽  
Author(s):  
Daniel M Jones ◽  
Alan F Heavens
Keyword(s):  
Mixture Models ◽  
Model Comparison ◽  
Gaussian Mixture Models ◽  
Gaussian Mixture ◽  
Computationally Efficient ◽  
Redshift Distribution ◽  
Photometric Redshifts ◽  
Galaxy Surveys ◽  
Photometric Redshift ◽  
Bayesian Model Comparison

ABSTRACT Future cosmological galaxy surveys such as the Large Synoptic Survey Telescope (LSST) will photometrically observe very large numbers of galaxies. Without spectroscopy, the redshifts required for the analysis of these data will need to be inferred using photometric redshift techniques that are scalable to large sample sizes. The high number density of sources will also mean that around half are blended. We present a Bayesian photometric redshift method for blended sources that uses Gaussian mixture models to learn the joint flux–redshift distribution from a set of unblended training galaxies, and Bayesian model comparison to infer the number of galaxies comprising a blended source. The use of Gaussian mixture models renders both of these applications computationally efficient and therefore suitable for upcoming galaxy surveys.

scholarly journals Predictions for the 21cm-galaxy cross-power spectrum observable with SKA and future galaxy surveys

2020 ◽  
Author(s):  
Dijana Vrbanec ◽  
Benedetta Ciardi ◽  
Vibor Jelić ◽  
Hannes Jensen ◽  
Ilian T Iliev ◽  
...  
Keyword(s):  
Power Spectrum ◽  
Wide Field ◽  
Galaxy Surveys ◽  
Lyman Alpha ◽  
Alpha Emitters ◽  
Cross Correlations ◽  
Square Kilometer Array ◽  
Lyman Alpha Emitters ◽  
Infrared Survey ◽  
Cross Power Spectrum

Abstract In this paper we use radiative transfer + N-body simulations to explore the feasibility of measurements of cross-correlations between the 21 cm field observed by the Square Kilometer Array (SKA) and high-z Lyman Alpha Emitters (LAEs) detected in galaxy surveys with the Subaru Hyper Supreme Cam (HSC), Subaru Prime Focus Spectrograph (PFS) and Wide Field Infrared Survey Telescope (WFIRST). 21cm-LAE cross-correlations are in fact a powerful probe of the epoch of reionization as they are expected to provide precious information on the progress of reionization and the typical scale of ionized regions at different redshifts. The next generation observations with SKA will have a noise level much lower than those with its precursor radio facilities, introducing a significant improvement in the measurement of the cross-correlations. We find that an SKA-HSC/PFS observation will allow to investigate scales below ∼10 h−1 Mpc and ∼60 h−1 Mpc at z = 7.3 and 6.6, respectively. WFIRST will allow to access also higher redshifts, as it is expected to observe spectroscopically ∼900 LAEs per square degree and unit redshift in the range 7.5 ≤ z ≤ 8.5. Because of the reduction of the shot noise compared to HSC and PFS, observations with WFIRST will result in more precise cross-correlations and increased observable scales.

scholarly journals Cross-correlating spectroscopic and photometric galaxy surveys

2014 ◽  
Vol 10 (S306) ◽  
pp. 213-215
Author(s):  
Martin B. Eriksen ◽  
Enrique Gaztañaga
Keyword(s):  
Dark Energy ◽  
Figure Of Merit ◽  
Stage Iv ◽  
The Other ◽  
Sample Variance ◽  
Two Stage ◽  
Galaxy Surveys ◽  
Other Hand ◽  
Growth History ◽  
Cross Correlations

AbstractDoes photometric and spectroscopic survey benefit from overlapping areas? The photometric survey measures 2D Weak Lensing (WL) information from galaxy shape distortions. On the other hand, the higher redshift precision of an spectroscopic survey allows measurements of redshift space distortions (RSD) and baryonic accustic oscillations (BAO) from 3D galaxy counts.The two surveys are combined using 2D-correlations, using sufficiently narrow bins to capture the radial information. This poster present effects of RSD and intrinsic correlations between narrow redshift bins. In understanding how the effects affects cosmological constrains, we first define two stage-IV and then present forecast for various configurations. When surveys overlap, they benefit from additional cross-correlations and sample variance cancellations from overlapping volumes. For a combined dark energy and growth history figure of merit, the result increase 50% for overlapping surveys, corresponding to 30% larger area.

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