We present new constraints on the relationship between galaxies and their host dark matter haloes, measured from the location of the peak of the stellar-to-halo mass ratio (SHMR), up to the most ...massive galaxy clusters at redshift z ∼ 0.8 and over a volume of nearly 0.1 Gpc3. We use a unique combination of deep observations in the CFHTLenS/VIPERS field from the near-UV to the near-IR, supplemented by ∼60 000 secure spectroscopic redshifts, analysing galaxy clustering, galaxy–galaxy lensing and the stellar mass function. We interpret our measurements within the halo occupation distribution (HOD) framework, separating the contributions from central and satellite galaxies. We find that the SHMR for the central galaxies peaks at
$M_{\rm h, peak} = 1.9^{+0.2}_{-0.1}\times 10^{12}{\,{\rm M}_{{\odot }}}$
with an amplitude of 0.025, which decreases to ∼0.001 for massive haloes (
${{{M}_{\rm h}}}> 10^{14} {\,{\rm M}_{{\odot }}}$
). Compared to central galaxies only, the total SHMR (including satellites) is boosted by a factor of 10 in the high-mass regime (cluster-size haloes), a result consistent with cluster analyses from the literature based on fully independent methods. After properly accounting for differences in modelling, we have compared our results with a large number of results from the literature up to z = 1: we find good general agreement, independently of the method used, within the typical stellar-mass systematic errors at low to intermediate mass (
${{{M}_{\rm \star }}}<10^{11} {\,{\rm M}_{{\odot }}}$
) and the statistical errors above. We have also compared our SHMR results to semi-analytic simulations and found that the SHMR is tilted compared to our measurements in such a way that they over- (under-) predict star formation efficiency in central (satellite) galaxies.
Sexual health is an integral part of overall health in older age. Research consistently reports that heterosexual and queer older people tend not to disclose sexual concerns and difficulties which ...increases the risks for sexually transmitted diseases. Older people are often absent from policies and information programmes and healthcare providers experience difficulties in initiating conversations around sexual health and history.
To identify what are the barriers that stop older people seeking sexual health advice and treatment.
A scoping review methodology was employed. Published and unpublished literature was scoped through development of a research question, identification of potentially relevant studies, selection of relevant studies using an iterative team approach, charting data, collating, summarising and reporting findings, and considering the implications of study findings for further research.
Electronic databases searches were run to identify published and unpublished literature, including Medline, Embase, PsycINFO, CINAHL, ASSIA, Social Sciences, RCN and Cochrane Libraries. Additional studies were located through hand searching.
Twelve studies from: the USA (n = 6); the UK (n = 3); Australia (n = 2); and one shared paper between New Zealand and UK met the inclusion criteria. Four barriers that stop older people seeking sexual health advice and treatment were identified, including (1) Cultural and societal views and beliefs toward sexual health; (2) Stigma, embarrassment and discrimination; (3) Lack of education and training of healthcare professionals; (4) Quality of relationship between patients and health professionals.
Barriers to seeking and receiving advice and treatment for sexual health in later life clearly exist and are both related to cultural and social factors. Overall, the papers reviewed in this scoping review indicate that healthcare providers are reluctant to initiate conversations around sexual health or offer appropriate advice or clinical tests, and that older people tend to be hesitant to seek medical help. Later life age groups independently from their sexual orientation represent a hidden population and are absent from sexual health campaigns and government policies. Efforts need to be made by influential institutions and healthcare providers to recognise sexuality in older age and give older people the opportunity to open up regarding their sexual health and experiences.
We introduce redMaGiC, an automated algorithm for selecting luminous red galaxies (LRGs). The algorithm was specifically developed to minimize photometric redshift uncertainties in photometric ...large-scale structure studies. redMaGiC achieves this by self-training the colour cuts necessary to produce a luminosity-thresholded LRG sample of constant comoving density. We demonstrate that redMaGiC photo-zs are very nearly as accurate as the best machine learning-based methods, yet they require minimal spectroscopic training, do not suffer from extrapolation biases, and are very nearly Gaussian. We apply our algorithm to Dark Energy Survey (DES) Science Verification (SV) data to produce a redMaGiC catalogue sampling the redshift range z ∈ 0.2, 0.8. Our fiducial sample has a comoving space density of 10−3 (h
−1 Mpc)−3, and a median photo-z bias (z
spec − z
photo) and scatter (σ
z
/(1 + z)) of 0.005 and 0.017, respectively. The corresponding 5σ outlier fraction is 1.4 per cent. We also test our algorithm with Sloan Digital Sky Survey Data Release 8 and Stripe 82 data, and discuss how spectroscopic training can be used to control photo-z biases at the 0.1 per cent level.
Shear peak statistics has gained a lot of attention recently as a practical alternative to the two-point statistics for constraining cosmological parameters. We perform a shear peak statistics ...analysis of the Dark Energy Survey (DES) Science Verification (SV) data, using weak gravitational lensing measurements from a 139 deg super( 2) field. We measure the abundance of peaks identified in aperture mass maps, as a function of their signal-to-noise ratio, in the signal-to-noise range ... To predict the peak counts as a function of cosmological parameters, we use a suite of N-body simulations spanning 158 models with varying ... and ..., fixing ..., to which we have applied the DES SV mask and redshift distribution. In our fiducial analysis we measure ..., after marginalizing over the shear multiplicative bias and the error on the mean redshift of the galaxy sample. We introduce models of intrinsic alignments, blending and source contamination by cluster members. These models indicate that peaks with ... would require significant corrections, which is why we do not include them in our analysis. We compare our results to the cosmological constraints from the two-point analysis on the SV field and find them to be in good agreement in both the central value and its uncertainty. We discuss prospects for future peak statistics analysis with upcoming DES data. (ProQuest: ... denotes formulae/symbols omitted.)
Abstract
We use weak-lensing shear measurements to determine the mean mass of optically selected galaxy clusters in Dark Energy Survey Science Verification data. In a blinded analysis, we split the ...sample of more than 8000 redMaPPer clusters into 15 subsets, spanning ranges in the richness parameter 5 ≤ λ ≤ 180 and redshift 0.2 ≤ z ≤ 0.8, and fit the averaged mass density contrast profiles with a model that accounts for seven distinct sources of systematic uncertainty: shear measurement and photometric redshift errors; cluster-member contamination; miscentring; deviations from the NFW halo profile; halo triaxiality and line-of-sight projections. We combine the inferred cluster masses to estimate the joint scaling relation between mass, richness and redshift,
${\cal M}(\lambda ,z) \propto M_0 \lambda ^{F} (1+z)^{G}$
. We find
$M_0 \equiv \langle M_{200\mathrm{m}}\,|\,\lambda =30,z=0.5 \rangle = 2.35 \pm 0.22\ \rm {(stat)} \pm 0.12\ \rm {(sys)} \times \ 10^{14}\ \mathrm{M}_{{\odot }}$
, with
$F = 1.12\,\pm \,0.20\ \rm {(stat)}\, \pm \, 0.06\ \rm {(sys)}$
and
$G = 0.18\,\pm \, 0.75\ \rm {(stat)}\, \pm \, 0.24\ \rm {(sys)}$
. The amplitude of the mass–richness relation is in excellent agreement with the weak-lensing calibration of redMaPPer clusters in SDSS by Simet et al. and with the Saro et al. calibration based on abundance matching of SPT-detected clusters. Our results extend the redshift range over which the mass–richness relation of redMaPPer clusters has been calibrated with weak lensing from z ≤ 0.3 to z ≤ 0.8. Calibration uncertainties of shear measurements and photometric redshift estimates dominate our systematic error budget and require substantial improvements for forthcoming studies.
We present data products from the Canada-France-Hawaii Telescope Lensing Survey (CFHTLenS). CFHTLenS is based on the Wide component of the Canada-France-Hawaii Telescope Legacy Survey (CFHTLS). It ...encompasses 154 deg2 of deep, optical, high-quality, sub-arcsecond imaging data in the five optical filters u*g
′
r
′
i
′
z
′. The scientific aims of the CFHTLenS team are weak gravitational lensing studies supported by photometric redshift estimates for the galaxies. This paper presents our data processing of the complete CFHTLenS data set. We were able to obtain a data set with very good image quality and high-quality astrometric and photometric calibration. Our external astrometric accuracy is between 60 and 70 mas with respect to Sloan Digital Sky Survey (SDSS) data, and the internal alignment in all filters is around 30 mas. Our average photometric calibration shows a dispersion of the order of 0.01-0.03 mag for g
′
r
′
i
′
z
′ and about 0.04 mag for u* with respect to SDSS sources down to i
SDSS ≤ 21. We demonstrate in accompanying papers that our data meet necessary requirements to fully exploit the survey for weak gravitational lensing analyses in connection with photometric redshift studies. In the spirit of the CFHTLS, all our data products are released to the astronomical community via the Canadian Astronomy Data Centre at http://www.cadc-ccda.hia-iha.nrc-cnrc.gc.ca/community/CFHTLens/query.html. We give a description and how-to manuals of the public products which include image pixel data, source catalogues with photometric redshift estimates and all relevant quantities to perform weak lensing studies.
Here we present the results of various approaches to measure accurate colours and photometric redshifts (photo-z) from wide-field imaging data. We use data from the Canada-France-Hawaii Telescope ...Legacy Survey which have been re-processed by the Canada-France-Hawaii Telescope Lensing Survey (CFHTLenS) team in order to carry out a number of weak gravitational lensing studies. An emphasis is put on the correction of systematic effects in the photo-z arising from the different point spread functions (PSFs) in the five optical bands. Different ways of correcting these effects are discussed and the resulting photo-z accuracies are quantified by comparing the photo-z to large spectroscopic redshift (spec-z) data sets. Careful homogenization of the PSF between bands leads to increased overall accuracy of photo-z. The gain is particularly pronounced at fainter magnitudes where galaxies are smaller and flux measurements are affected more by PSF effects. We discuss ways of defining more secure subsamples of galaxies as well as a shape- and colour-based star-galaxy separation method, and we present redshift distributions for different magnitude limits. We also study possible re-calibrations of the photometric zero-points (ZPs) with the help of galaxies with known spec-z. We find that if PSF effects are properly taken into account, a re-calibration of the ZPs becomes much less important suggesting that previous such re-calibrations described in the literature could in fact be mostly corrections for PSF effects rather than corrections for real inaccuracies in the ZPs. The implications of this finding for future surveys like the Kilo Degree Survey (KiDS), Dark Energy Survey (DES), Large Synoptic Survey Telescope or Euclid are mixed. On the one hand, ZP re-calibrations with spec-z values might not be as accurate as previously thought. On the other hand, careful PSF homogenization might provide a way out and yield accurate, homogeneous photometry without the need for full spectroscopic coverage. This is the first paper in a series describing the technical aspects of CFHTLenS.
We present results from a study of the photometric redshift performance of the Dark Energy Survey (DES), using the early data from a Science Verification period of observations in late 2012 and early ...2013 that provided science-quality images for almost 200 sq. deg. at the nominal depth of the survey. We assess the photometric redshift (photo-z) performance using about 15 000 galaxies with spectroscopic redshifts available from other surveys. These galaxies are used, in different configurations, as a calibration sample, and photo-z's are obtained and studied using most of the existing photo-z codes. A weighting method in a multidimensional colour-magnitude space is applied to the spectroscopic sample in order to evaluate the photo-z performance with sets that mimic the full DES photometric sample, which is on average significantly deeper than the calibration sample due to the limited depth of spectroscopic surveys. Empirical photo-z methods using, for instance, artificial neural networks or random forests, yield the best performance in the tests, achieving core photo-z resolutions ... ~ 0.08. Moreover, the results from most of the codes, including template-fitting methods, comfortably meet the DES requirements on photo-z performance, therefore, providing an excellent precedent for future DES data sets. (ProQuest: ... denotes formulae/symbols omitted.)
We study the clustering of galaxies detected at i < 22.5 in the Science Verification observations of the Dark Energy Survey (DES). Two-point correlation functions are measured using 2.3 × 106 ...galaxies over a contiguous 116 deg2 region in five bins of photometric redshift width Δz = 0.2 in the range 0.2 < z < 1.2. The impact of photometric redshift errors is assessed by comparing results using a template-based photo-z algorithm (BPZ) to a machine-learning algorithm (TPZ). A companion paper presents maps of several observational variables (e.g. seeing, sky brightness) which could modulate the galaxy density. Here we characterize and mitigate systematic errors on the measured clustering which arise from these observational variables, in addition to others such as Galactic dust and stellar contamination. After correcting for systematic effects, we measure galaxy bias over a broad range of linear scales relative to mass clustering predicted from the Planck Λ cold dark matter model, finding agreement with the Canada-France-Hawaii Telescope Legacy Survey (CFHTLS) measurements with χ2 of 4.0 (8.7) with 5 degrees of freedom for the TPZ (BPZ) redshifts. We test a ‘linear bias’ model, in which the galaxy clustering is a fixed multiple of the predicted non-linear dark matter clustering. The precision of the data allows us to determine that the linear bias model describes the observed galaxy clustering to 2.5 per cent accuracy down to scales at least 4–10 times smaller than those on which linear theory is expected to be sufficient.
ABSTRACT Spatially varying depth and the characteristics of observing conditions, such as seeing, airmass, or sky background, are major sources of systematic uncertainties in modern galaxy survey ...analyses, particularly in deep multi-epoch surveys. We present a framework to extract and project these sources of systematics onto the sky, and apply it to the Dark Energy Survey (DES) to map the observing conditions of the Science Verification (SV) data. The resulting distributions and maps of sources of systematics are used in several analyses of DES-SV to perform detailed null tests with the data, and also to incorporate systematics in survey simulations. We illustrate the complementary nature of these two approaches by comparing the SV data with BCC-UFig, a synthetic sky catalog generated by forward-modeling of the DES-SV images. We analyze the BCC-UFig simulation to construct galaxy samples mimicking those used in SV galaxy clustering studies. We show that the spatially varying survey depth imprinted in the observed galaxy densities and the redshift distributions of the SV data are successfully reproduced by the simulation and are well-captured by the maps of observing conditions. The combined use of the maps, the SV data, and the BCC-UFig simulation allows us to quantify the impact of spatial systematics on N(z), the redshift distributions inferred using photometric redshifts. We conclude that spatial systematics in the SV data are mainly due to seeing fluctuations and are under control in current clustering and weak-lensing analyses. However, they will need to be carefully characterized in upcoming phases of DES in order to avoid biasing the inferred cosmological results. The framework presented here is relevant to all multi-epoch surveys and will be essential for exploiting future surveys such as the Large Synoptic Survey Telescope, which will require detailed null tests and realistic end-to-end image simulations to correctly interpret the deep, high-cadence observations of the sky.
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