ORCID Profile
0000-0002-3827-0175
Current Organisation
Leiden University
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Astronomical and Space Sciences | Cosmology and Extragalactic Astronomy
Publisher: Oxford University Press (OUP)
Date: 17-01-2019
DOI: 10.1093/MNRAS/STZ189
Publisher: Oxford University Press (OUP)
Date: 08-03-2017
DOI: 10.1093/MNRAS/STX562
Publisher: Cambridge University Press (CUP)
Date: 07-2007
DOI: 10.1017/S1743921308017195
Abstract: NMAGIC is a parallel implementation of our made-to-measure (χ 2 M2M) algorithm for constructing N-particle models of stellar systems from observational data, which extends earlier ideas by Syer & Tremaine (1996). The χ 2 M2M algorithm properly accounts for observational errors, is flexible, and can be applied to various systems and geometries. We show its ability to reproduce the internal dynamics of an oblate isotropic rotator model and report on the modeling of the dark matter (DM) halo of NGC 3379 combining SAURON and PN.S kinematic data. The χ 2 M2M algorithm is practical, reliable and can be applied to various dynamical systems without symmetry restrictions. We conclude that χ 2 M2M holds great promise for unraveling the internal dynamics of bulges.
Publisher: Oxford University Press (OUP)
Date: 12-08-2016
Publisher: EDP Sciences
Date: 31-10-2012
Publisher: Oxford University Press (OUP)
Date: 11-04-2009
Publisher: Oxford University Press (OUP)
Date: 20-07-2016
Publisher: EDP Sciences
Date: 04-2019
DOI: 10.1051/0004-6361/201834819
Abstract: Exploiting the full statistical power of future cosmic shear surveys will necessitate improvements to the accuracy with which the gravitational lensing signal is measured. We present a framework for calibrating shear with image simulations that demonstrates the importance of including realistic correlations between galaxy morphology, size, and more importantly, photometric redshifts. This realism is essential to ensure that selection and shape measurement biases can be calibrated accurately for a tomographic cosmic shear analysis. We emulate Kilo-Degree Survey (KiDS) observations of the COSMOS field using morphological information from Hubble Space Telescope imaging, faithfully reproducing the measured galaxy properties from KiDS observations of the same field. We calibrate our shear measurements from lens fit, and find through a range of sensitivity tests that lens fit is robust and unbiased within the allowed two per cent tolerance of our study. Our results show that the calibration has to be performed by selecting the tomographic s les in the simulations, consistent with the actual cosmic shear analysis, because the joint distributions of galaxy properties are found to vary with redshift. Ignoring this redshift variation could result in misestimating the shear bias by an amount that exceeds the allowed tolerance. To improve the calibration for future cosmic shear analyses, it will also be essential to correctly account for the measurement of photometric redshifts, which requires simulating multi-band observations.
Publisher: EDP Sciences
Date: 10-2018
DOI: 10.1051/0004-6361/201732473
Abstract: Context . In the hierarchical two-phase formation scenario, the halos of early type galaxies (ETGs) are expected to have different physical properties from the galaxies’ central regions. Aims . The ePN.S survey characterizes the kinematic properties of ETG halos using planetary nebulae (PNe) as tracers, overcoming the limitations of absorption line spectroscopy at low surface brightness. Methods . We present two-dimensional velocity and velocity dispersion fields for 33 ETGs, including fast (FRs) and slow rotators (SRs). The velocity fields were reconstructed from the measured PN velocities using an adaptive kernel procedure validated with simulations, and extend to a median of 5.6 effective radii ( R e ). We complemented the PN kinematics with absorption line data from the literature, for a complete description of the kinematics from the center to the outskirts. Results . ETGs typically show a kinematic transition between inner regions and halo. Estimated transition radii in units of R e anti-correlate with stellar mass. SRs have increased but still modest rotational support at large radii. Most of the FRs show a decrease in rotation, due to the fading of the inner disk in the outer, more slowly rotating spheroid. 30% of the FRs are dominated by rotation also at large radii. Most ETGs have flat or slightly falling halo velocity dispersion profiles, but 15% of the s le have steeply falling profiles. All of the SRs and 40% of the FRs show signatures of triaxial halos such as kinematic twists or misalignments. We show with illustrative photometric models that this is consistent with the distribution of isophote twists from extended photometry. Conclusions . ETGs have more erse kinematic properties in their halos than in the central regions. FRs do contain inner disk components but these frequently fade in outer spheroids which are often triaxial. The observed kinematic transition to the halo and its dependence on stellar mass is consistent with ΛCDM simulations and supports a two-phase formation scenario.
Publisher: Oxford University Press (OUP)
Date: 28-10-2015
Publisher: Oxford University Press (OUP)
Date: 18-11-2011
Publisher: Oxford University Press (OUP)
Date: 30-07-2018
Publisher: Oxford University Press (OUP)
Date: 05-2013
DOI: 10.1093/MNRAS/STT529
Publisher: Oxford University Press (OUP)
Date: 27-06-2011
Publisher: Oxford University Press (OUP)
Date: 11-12-2016
Publisher: EDP Sciences
Date: 02-2023
DOI: 10.1051/0004-6361/202245210
Abstract: We present SKiLLS, a suite of multi-band image simulations for the weak lensing analysis of the complete Kilo-Degree Survey (KiDS), dubbed KiDS-Legacy analysis. The resulting catalogues enable joint shear and redshift calibration, enhancing the realism and hence accuracy over previous efforts. To create a large volume of simulated galaxies with faithful properties and to a sufficient depth, we integrated cosmological simulations with high-quality imaging observations. We also improved the realism of simulated images by allowing the point spread function (PSF) to differ between CCD images, including stellar density variations and varying noise levels between pointings. Using realistic variable shear fields, we accounted for the impact of blended systems at different redshifts. Although the overall correction is minor, we found a clear redshift-bias correlation in the blending-only variable shear simulations, indicating the non-trivial impact of this higher-order blending effect. We also explored the impact of the PSF modelling errors and found a small yet noticeable effect on the shear bias. Finally, we conducted a series of sensitivity tests, including changing the input galaxy properties. We conclude that our fiducial shape measurement algorithm, lens fit, is robust within the requirements of lensing analyses with KiDS. As for future weak lensing surveys with tighter requirements, we suggest further investments in understanding the impact of blends at different redshifts, improving the PSF modelling algorithm and developing the shape measurement method to be less sensitive to the galaxy properties.
Publisher: EDP Sciences
Date: 10-2021
DOI: 10.1051/0004-6361/202140706
Abstract: We constrain the luminosity and redshift dependence of the intrinsic alignment (IA) of a nearly volume-limited s le of luminous red galaxies selected from the fourth public data release of the Kilo-Degree Survey (KiDS-1000). To measure the shapes of the galaxies, we used two complementary algorithms, finding consistent IA measurements for the overlapping galaxy s le. The global significance of IA detection across our two independent luminous red galaxy s les, with our favoured method of shape estimation, is ∼10.7 σ . We find no significant dependence with redshift of the IA signal in the range 0.2 z 0.8, nor a dependence with luminosity below L r ≲ 2.9 × 10 10 h −2 L r , ⊙ . Above this luminosity, however, we find that the IA signal increases as a power law, although our results are also compatible with linear growth within the current uncertainties. This behaviour motivates the use of a broken power law model when accounting for the luminosity dependence of IA contamination in cosmic shear studies.
Publisher: Oxford University Press (OUP)
Date: 08-05-2019
Publisher: EDP Sciences
Date: 10-2020
DOI: 10.1051/0004-6361/202038505
Abstract: The physics of gravity on cosmological scales affects both the rate of assembly of large-scale structure and the gravitational lensing of background light through this cosmic web. By comparing the litude of these different observational signatures, we can construct tests that can distinguish general relativity from its potential modifications. We used the latest weak gravitational lensing dataset from the Kilo-Degree Survey, KiDS-1000, in conjunction with overlapping galaxy spectroscopic redshift surveys, BOSS and 2dFLenS, to perform the most precise existing litude-ratio test. We measured the associated E G statistic with 15 − 20% errors in five Δ z = 0.1 tomographic redshift bins in the range 0.2 z 0.7 on projected scales up to 100 h −1 Mpc. The scale-independence and redshift-dependence of these measurements are consistent with the theoretical expectation of general relativity in a Universe with matter density Ω m = 0.27 ± 0.04. We demonstrate that our results are robust against different analysis choices, including schemes for correcting the effects of source photometric redshift errors, and we compare the performance of angular and projected galaxy-galaxy lensing statistics.
Publisher: Oxford University Press (OUP)
Date: 24-11-2017
Publisher: EDP Sciences
Date: 08-2018
DOI: 10.1051/0004-6361/201731942
Abstract: We present a machine-learning photometric redshift (ML photo- z ) analysis of the Kilo-Degree Survey Data Release 3 (KiDS DR3), using two neural-network based techniques: ANNz2 and MLPQNA. Despite limited coverage of spectroscopic training sets, these ML codes provide photo- z s of quality comparable to, if not better than, those from the Bayesian Photometric Redshift (BPZ) code, at least up to z phot ≲ 0.9 and r ≲ 23.5. At the bright end of r ≲ 20, where very complete spectroscopic data overlapping with KiDS are available, the performance of the ML photo- z s clearly surpasses that of BPZ, currently the primary photo- z method for KiDS. Using the Galaxy And Mass Assembly (GAMA) spectroscopic survey as calibration, we furthermore study how photo- z s improve for bright sources when photometric parameters additional to magnitudes are included in the photo- z derivation, as well as when VIKING and WISE infrared (IR) bands are added. While the fiducial four-band ugri setup gives a photo- z bias 〈 δz /(1 + z )〉 = −2 × 10 −4 and scatter σ δz/(1+z) 0.022 at mean 〈 z 〉 = 0.23, combining magnitudes, colours, and galaxy sizes reduces the scatter by ~7% and the bias by an order of magnitude. Once the ugri and IR magnitudes are joined into 12-band photometry spanning up to 12 μ m, the scatter decreases by more than 10% over the fiducial case. Finally, using the 12 bands together with optical colours and linear sizes gives 〈 δz /(1 + z )〉 4 × 10 −5 and σ δz /(1+ z ) 0.019. This paper also serves as a reference for two public photo- z catalogues accompanying KiDS DR3, both obtained using the ANNz2 code. The first one, of general purpose, includes all the 39 million KiDS sources with four-band ugri measurements in DR3. The second dataset, optimised for low-redshift studies such as galaxy-galaxy lensing, is limited to r ≲ 20, and provides photo- z s of much better quality than in the full-depth case thanks to incorporating optical magnitudes, colours, and sizes in the GAMA-calibrated photo- z derivation.
Publisher: Oxford University Press (OUP)
Date: 02-2005
Publisher: Oxford University Press (OUP)
Date: 11-2017
Publisher: Oxford University Press (OUP)
Date: 03-08-2012
Publisher: Oxford University Press (OUP)
Date: 12-12-2011
Publisher: Oxford University Press (OUP)
Date: 21-12-2012
DOI: 10.1093/MNRAS/STS493
Publisher: Oxford University Press (OUP)
Date: 04-07-2011
Publisher: Wiley
Date: 25-11-2008
Abstract: We use density and temperature profiles obtained from XMM‐Newton observations to derive a potential of NGC 5846 out to 11 R e , thus probing the mass distribution deep into the halo. The inferred circular velocity is significantly higher than the extrapolation of dynamical models implying a halo, more massive than previously thought. Using an I ‐band surfacebrightness profile and a projected velocity dispersion profile consisting of long‐slit kinematic measurements and planetary nebulae (PNe) velocity dispersions, we solve the Jeans equations, assuming a non‐rotating spherical system. The solutions suggest a highly radially anisotropic galaxy outside 0.7 R e with β ∼ 0.75. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Publisher: Wiley
Date: 25-11-2008
Abstract: We present first results of a study of the halo kinematics for a s le of early type galaxies using planetary nebulae (PNe) as kinematical tracers. PNe allow to extend up to several effective radii ( R e ) the information from absorption line kinematics (confined to within 1 or 2 R e ), providing valuable information and constraints for merger simulations and galaxy formation models.We find that the specific angular momentum per unit mass has amore complex radial dependence when the halo region is taken into account and that the halo velocity dispersion is related to the total galaxy luminosity, isophotal shape, and number of PNe per unit of luminosity. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Publisher: EDP Sciences
Date: 30-04-2019
DOI: 10.1051/0004-6361/201834918
Abstract: Context . The Kilo-Degree Survey (KiDS) is an ongoing optical wide-field imaging survey with the OmegaCAM camera at the VLT Survey Telescope, specifically designed for measuring weak gravitational lensing by galaxies and large-scale structure. When completed it will consist of 1350 square degrees imaged in four filters ( ugri ). Aims . Here we present the fourth public data release which more than doubles the area of sky covered by data release 3. We also include aperture-matched Z Y J H K s photometry from our partner VIKING survey on the VISTA telescope in the photometry catalogue. We illustrate the data quality and describe the catalogue content. Methods . Two dedicated pipelines are used for the production of the optical data. The ASTRO -WISE information system is used for the production of co-added images in the four survey bands, while a separate reduction of the r -band images using the THELI pipeline is used to provide a source catalogue suitable for the core weak lensing science case. All data have been re-reduced for this data release using the latest versions of the pipelines. The VIKING photometry is obtained as forced photometry on the THELI sources, using a re-reduction of the VIKING data that starts from the VISTA pawprints. Modifications to the pipelines with respect to earlier releases are described in detail. The photometry is calibrated to the Gaia DR2 G band using stellar locus regression. Results . In this data release a total of 1006 square-degree survey tiles with stacked ugri images are made available, accompanied by weight maps, masks, and single-band source lists. We also provide a multi-band catalogue based on r -band detections, including homogenized photometry and photometric redshifts, for the whole dataset. Mean limiting magnitudes (5 σ in a 2″ aperture) and the tile-to-tile rms scatter are 24.23 ± 0.12, 25.12 ± 0.14, 25.02 ± 0.13, 23.68 ± 0.27 in ugri , respectively, and the mean r -band seeing is 0.″70.
Publisher: EDP Sciences
Date: 2020
DOI: 10.1051/0004-6361/201834878
Abstract: We present a tomographic cosmic shear analysis of the Kilo-Degree Survey (KiDS) combined with the VISTA Kilo-Degree Infrared Galaxy Survey. This is the first time that a full optical to near-infrared data set has been used for a wide-field cosmological weak lensing experiment. This unprecedented data, spanning 450 deg 2 , allows us to significantly improve the estimation of photometric redshifts, such that we are able to include robustly higher-redshift sources for the lensing measurement, and – most importantly – to solidify our knowledge of the redshift distributions of the sources. Based on a flat ΛCDM model we find S 8 ≡ σ 8 Ω m /0.3 = 0.737 +0.040 −0.036 in a blind analysis from cosmic shear alone. The tension between KiDS cosmic shear and the Planck-Legacy CMB measurements remains in this systematically more robust analysis, with S 8 differing by 2.3 σ . This result is insensitive to changes in the priors on nuisance parameters for intrinsic alignment, baryon feedback, and neutrino mass. KiDS shear measurements are calibrated with a new, more realistic set of image simulations and no significant B-modes are detected in the survey, indicating that systematic errors are under control. When calibrating our redshift distributions by assuming the 30-band COSMOS-2015 photometric redshifts are correct (following the Dark Energy Survey and the Hyper Suprime-Cam Survey), we find the tension with Planck is alleviated. The robust determination of source redshift distributions remains one of the most challenging aspects for future cosmic shear surveys.
Publisher: EDP Sciences
Date: 22-11-2019
DOI: 10.1051/0004-6361/201834879
Abstract: We present the curation and verification of a new combined optical and near infrared dataset for cosmology and astrophysics, derived by combining u g r i -band imaging from the Kilo-Degree Survey (KiDS) and Z Y J H K s -band imaging from the VISTA Kilo degree Infrared Galaxy (VIKING) survey. This dataset is unrivaled in cosmological imaging surveys due to the combination of its area (458 deg 2 before masking), depth ( r ≤ 25), and wavelength coverage ( u g r i Z Y J H K s ). This combination of survey depth, area, and (most importantly) wavelength coverage allows significant reductions in systematic uncertainties (i.e. reductions of between 10% and 60% in bias, outlier rate, and scatter) in photometric-to-spectroscopic redshift comparisons, compared to the optical-only case at photo- z above 0.7. The complementarity between our optical and near infrared surveys means that over 80% of our sources, across all photo- z , have significant detections (i.e. not upper limits) in our eight reddest bands. We have derived photometry, photo- z , and stellar masses for all sources in the survey, and verified these data products against existing spectroscopic galaxy s les. We demonstrate the fidelity of our higher-level data products by constructing the survey stellar mass functions in eight volume-complete redshift bins. We find that these photometrically derived mass functions provide excellent agreement with previous mass evolution studies derived using spectroscopic surveys. The primary data products presented in this paper are made publicly available through the KiDS survey website.
Publisher: EDP Sciences
Date: 02-2021
DOI: 10.1051/0004-6361/202037670
Abstract: Cosmological simulations predict that galaxies are embedded into triaxial dark matter haloes, which appear approximately elliptical in projection. Weak gravitational lensing allows us to constrain these halo shapes and thereby test the nature of dark matter. Weak lensing has already provided robust detections of the signature of halo flattening at the mass scales of groups and clusters, whereas results for galaxies have been somewhat inconclusive. Here we combine data from five weak lensing surveys (NGVSLenS, KiDS/KV450, CFHTLenS, CS82, and RCSLenS, listed in order of most to least constraining) in order to tighten observational constraints on galaxy-scale halo ellipticity for photometrically selected lens s les. We constrain f h , the average ratio between the aligned component of the halo ellipticity and the ellipticity of the light distribution, finding f h = 0.303 −0.079 +0.080 for red lens galaxies and f h = 0.217 −0.159 +0.160 for blue lens galaxies when assuming elliptical Navarro-Frenk-White density profiles and a linear scaling between halo ellipticity and galaxy ellipticity. Our constraints for red galaxies constitute the currently most significant (3.8 σ ) systematics-corrected detection of the signature of halo flattening at the mass scale of galaxies. Our results are in good agreement with expectations from the Millennium Simulation that apply the same analysis scheme and incorporate models for galaxy–halo misalignment. Assuming these misalignment models and the analysis assumptions stated above are correct, our measurements imply an average dark matter halo ellipticity for the studied red galaxy s les of ⟨| ϵ h |⟩ = 0.174 ± 0.046, where | ϵ h | = (1 − q )/(1 + q ) relates to the ratio q = b / a of the minor and major axes of the projected mass distribution. Similar measurements based on larger upcoming weak lensing data sets can help to calibrate models for intrinsic galaxy alignments, which constitute an important source of systematic uncertainty in cosmological weak lensing studies.
Publisher: Oxford University Press (OUP)
Date: 10-2009
Publisher: EDP Sciences
Date: 2013
Publisher: Cambridge University Press (CUP)
Date: 06-2008
DOI: 10.1017/S1743921308027981
Abstract: The GAMA survey aims to deliver 250,000 optical spectra (3–7 Å resolution) over 250 sq. degrees to spectroscopic limits of r AB 19.8 and K AB 17.0 mag. Complementary imaging will be provided by GALEX, VST, UKIRT, VISTA, HERSCHEL and ASKAP to comparable flux levels leading to a definitive multi-wavelength galaxy database. The data will be used to study all aspects of cosmic structures on 1kpc to 1Mpc scales spanning all environments and out to a redshift limit of z ≈ 0.4. Key science drivers include the measurement of: the halo mass function via group velocity dispersions the stellar, HI, and baryonic mass functions galaxy component mass-size relations the recent merger and star-formation rates by mass, types and environment. Detailed modeling of the spectra, broad SEDs, and spatial distributions should provide in idual star formation histories, ages, bulge-disc decompositions and stellar bulge, stellar disc, dust disc, neutral HI gas and total dynamical masses for a significant subset of the s le (~ 100k) spanning both the giant and dwarf galaxy populations. The survey commenced March 2008 with 50k spectra obtained in 21 clear nights using the Anglo Australian Observatory's new multi-fibre-fed bench-mounted dual-beam spectroscopic system (AAΩ).
Publisher: Oxford University Press (OUP)
Date: 12-2010
Publisher: American Astronomical Society
Date: 12-2021
Abstract: We present 97 new high-quality strong lensing candidates found in the final ∼350 deg 2 that complete the full ∼1350 deg 2 area of the Kilo-Degree Survey (KiDS). Together with our previous findings, the final list of high-quality candidates from KiDS sums up to 268 systems. The new s le is assembled using a new convolutional neural network (CNN) classifier applied to r -band (best-seeing) and g , r , and i color-composited images separately. This optimizes the complementarity of the morphology and color information on the identification of strong lensing candidates. We apply the new classifiers to a s le of luminous red galaxies (LRGs) and a s le of bright galaxies (BGs) and select candidates that received a high probability to be a lens from the CNN ( P CNN ). In particular, setting P CNN 0.8 for the LRGs, the one-band CNN predicts 1213 candidates, while the three-band classifier yields 1299 candidates, with only ∼30% overlap. For the BGs, in order to minimize the false positives, we adopt a more conservative threshold, P CNN 0.9, for both CNN classifiers. This results in 3740 newly selected objects. The candidates from the two s les are visually inspected by seven coauthors to finally select 97 “high-quality” lens candidates which received mean scores larger than 6 (on a scale from 0 to 10). We finally discuss the effect of the seeing on the accuracy of CNN classification and possible avenues to increase the efficiency of multiband classifiers, in preparation of next-generation surveys from ground and space.
Publisher: American Astronomical Society
Date: 20-07-2007
DOI: 10.1086/518358
Publisher: Oxford University Press (OUP)
Date: 02-11-2016
Publisher: Oxford University Press (OUP)
Date: 21-02-2009
Publisher: EDP Sciences
Date: 02-2021
DOI: 10.1051/0004-6361/202039063
Abstract: We present a joint cosmological analysis of weak gravitational lensing observations from the Kilo-Degree Survey (KiDS-1000), with redshift-space galaxy clustering observations from the Baryon Oscillation Spectroscopic Survey (BOSS) and galaxy-galaxy lensing observations from the overlap between KiDS-1000, BOSS, and the spectroscopic 2-degree Field Lensing Survey. This combination of large-scale structure probes breaks the degeneracies between cosmological parameters for in idual observables, resulting in a constraint on the structure growth parameter S 8 = σ 8 √(Ω m /0.3) = 0.766 −0.014 +0.020 , which has the same overall precision as that reported by the full-sky cosmic microwave background observations from Planck . The recovered S 8 litude is low, however, by 8.3 ± 2.6% relative to Planck . This result builds from a series of KiDS-1000 analyses where we validate our methodology with variable depth mock galaxy surveys, our lensing calibration with image simulations and null-tests, and our optical-to-near-infrared redshift calibration with multi-band mock catalogues and a spectroscopic-photometric clustering analysis. The systematic uncertainties identified by these analyses are folded through as nuisance parameters in our cosmological analysis. Inspecting the offset between the marginalised posterior distributions, we find that the S 8 -difference with Planck is driven by a tension in the matter fluctuation litude parameter, σ 8 . We quantify the level of agreement between the cosmic microwave background and our large-scale structure constraints using a series of different metrics, finding differences with a significance ranging between ∼3 σ , when considering the offset in S 8 , and ∼2 σ , when considering the full multi-dimensional parameter space.
Publisher: Oxford University Press (OUP)
Date: 08-11-2010
Publisher: Oxford University Press (OUP)
Date: 12-04-2016
DOI: 10.1093/MNRAS/STW747
Publisher: IOP Publishing
Date: 11-2002
DOI: 10.1086/342765
Publisher: Oxford University Press (OUP)
Date: 05-2009
Publisher: American Astronomical Society
Date: 08-08-2019
Publisher: EDP Sciences
Date: 2023
DOI: 10.1051/0004-6361/202244673
Abstract: Context. Weak lensing and clustering statistics beyond two-point functions can capture non-Gaussian information about the matter density field, thereby improving the constraints on cosmological parameters relative to the mainstream methods based on correlation functions and power spectra. Aims. This paper presents a cosmological analysis of the fourth data release of the Kilo Degree Survey based on the density split statistics, which measures the mean shear profiles around regions classified according to foreground densities. The latter is constructed from a bright galaxy s le, which we further split into red and blue s les, allowing us to probe their respective connection to the underlying dark matter density. Methods. We used the state-of-the-art model of the density splitting statistics and validated its robustness against mock data infused with known systematic effects such as intrinsic galaxy alignment and baryonic feedback. Results. After marginalising over the photometric redshift uncertainty and the residual shear calibration bias, we measured for the full KiDS-bright s le a structure growth parameter of $ S_8\\equiv \\sigma_8 \\sqrt{\\Omega_{\\mathrm{m}}/0.3}=0.73^{+0.03}_{-0.02} $ that is competitive and consistent with two-point cosmic shear results, a matter density of Ω m = 0.27 ± 0.02, and a constant galaxy bias of b = 1.37 ± 0.10.
Publisher: American Association for the Advancement of Science (AAAS)
Date: 19-09-2003
Abstract: The kinematics of the outer parts of three intermediate-luminosity elliptical galaxies were studied with the Planetary Nebula Spectrograph. The galaxies' velocity-dispersion profiles were found to decline with the radius, and dynamical modeling of the data indicates the presence of little if any dark matter in these galaxies' halos. This unexpected result conflicts with findings in other galaxy types and poses a challenge to current galaxy formation theories.
Publisher: European Southern Observatory (ESO)
Date: 2019
Publisher: Cambridge University Press (CUP)
Date: 06-2007
DOI: 10.1017/S1743921307014111
Abstract: We examine the dark matter properties of nearby early-type galaxies using planetary nebulae (PNe) as mass probes. We have designed a specialised instrument, the Planetary Nebula Spectrograph (PN.S) operating at the William Herschel telescope, with the purpose of measuring PN velocities with best efficiency. The primary scientific objective of this custom-built instrument is the study of the PN kinematics in 12 ordinary round galaxies. Preliminary results showing a dearth of dark matter in ordinary galaxies (Romanowsky et al . 2003) are now confirmed by the first complete PN.S datasets. On the other hand early-type galaxies with a “regular” dark matter content are starting to be observed among the brighter PN.S target s le, thus confirming a correlation between the global dark-to-luminous mass virial ratio ( f DM = M DM M * ) and the galaxy luminosity and mass.
Publisher: AIP
Date: 2010
DOI: 10.1063/1.3458512
Publisher: Oxford University Press (OUP)
Date: 24-03-2011
Publisher: EDP Sciences
Date: 11-2017
DOI: 10.1051/0004-6361/201731335
Abstract: In recent years, many studies have reported substantial populations of large galaxies with low surface brightness in local galaxy clusters. Various theories that aim to explain the presence of such ultra-diffuse galaxies (UDGs) have since been proposed. A key question that will help to distinguish between models is whether UDGs have counterparts in host haloes with lower masses, and if so, what their abundance as a function of halo mass is. We here extend our previous study of UDGs in galaxy clusters to galaxy groups. We measure the abundance of UDGs in 325 spectroscopically selected groups from the Galaxy And Mass Assembly (GAMA) survey. We make use of the overlapping imaging from the ESO Kilo-Degree Survey (KiDS), from which we can identify galaxies with mean surface brightnesses within their effective radii down to ~25.5 mag arcsec -2 in the r band. We are able to measure a significant overdensity of UDGs (with sizes r eff ≥ 1.5 kpc) in galaxy groups down to M 200 = 10 12 M ⊙ , a regime where approximately only one in ten groups contains a UDG that we can detect. We combine measurements of the abundance of UDGs in haloes that cover three orders of magnitude in halo mass, finding that their numbers scale quite steeply with halo mass: N UDG ( R R 200 ) ∝ M 200 1.11±0.07 . To better interpret this, we also measure the mass-richness relation for brighter galaxies down to M r * + 2.5 in the same GAMA groups, and find a much shallower relation of N Bright ( R R 200 ) ∝ M 200 0.78±0.05 . This shows that compared to bright galaxies, UDGs are relatively more abundant in massive clusters than in groups. We discuss the implications, but it is still unclear whether this difference is related to a higher destruction rate of UDGs in groups or if massive haloes have a positive effect on UDG formation.
Publisher: Oxford University Press (OUP)
Date: 03-2011
Publisher: EDP Sciences
Date: 2021
DOI: 10.1051/0004-6361/202039070
Abstract: We present cosmological constraints from a cosmic shear analysis of the fourth data release of the Kilo-Degree Survey (KiDS-1000), which doubles the survey area with nine-band optical and near-infrared photometry with respect to previous KiDS analyses. Adopting a spatially flat standard cosmological model, we find S 8 = σ 8 (Ω m /0.3) 0.5 = 0.759 −0.021 +0.024 for our fiducial analysis, which is in 3 σ tension with the prediction of the Planck Legacy analysis of the cosmic microwave background. We compare our fiducial COSEBIs (Complete Orthogonal Sets of E/B-Integrals) analysis with complementary analyses of the two-point shear correlation function and band power spectra, finding the results to be in excellent agreement. We investigate the sensitivity of all three statistics to a number of measurement, astrophysical, and modelling systematics, finding our S 8 constraints to be robust and dominated by statistical errors. Our cosmological analysis of different isions of the data passes the Bayesian internal consistency tests, with the exception of the second tomographic bin. As this bin encompasses low-redshift galaxies, carrying insignificant levels of cosmological information, we find that our results are unchanged by the inclusion or exclusion of this s le.
Publisher: Oxford University Press (OUP)
Date: 05-04-2018
DOI: 10.1093/MNRAS/STY859
Publisher: Oxford University Press (OUP)
Date: 25-11-2010
Publisher: Oxford University Press (OUP)
Date: 05-12-2017
Publisher: Cambridge University Press (CUP)
Date: 10-2016
DOI: 10.1017/S1743921317001144
Abstract: The decomposition of the 21 cm rotation curve of galaxies into contribution from the disk and dark halo depends on the adopted mass to light ratio ( M/L ) of the disk. Given the vertical velocity dispersion (σ z ) of stars in the disk and its scale height ( h z ), the disk surface density and hence the M/L can be estimated. Earlier works have used this technique to conclude that galaxy disks are submaximal. Here we address an important conceptual problem: star-forming spirals have an old (kinematically hot) disk population and a young cold disk population. Both of these populations contribute to the integrated light spectra from which σ z is measured. The measured scale height h z is for the old disk population. In the Jeans equation, σ z and h z must pertain to the same population. We have developed techniques to extract the velocity dispersion of the old disk from integrated light spectra and from s les of planetary nebulae. We present the analysis of the disk kinematics of the galaxy NGC 628 using IFU data in the inner regions and planetary nebulae as tracers in the outer regions of the disk. We demonstrate that using the scale height of the old thin disk with the vertical velocity dispersion of the same population, traced by PNe, results in a maximal disk for NGC 628. Our analysis concludes that previous studies underestimate the disk surface mass density by ~ 2, sufficient to make a maximal disk for NGC 628 appear like a submaximal disk.
Publisher: Oxford University Press (OUP)
Date: 23-11-2017
Publisher: Oxford University Press (OUP)
Date: 03-2008
Publisher: Oxford University Press (OUP)
Date: 21-12-2012
Publisher: Oxford University Press (OUP)
Date: 31-10-2018
Publisher: EDP Sciences
Date: 08-2020
DOI: 10.1051/0004-6361/202038389
Abstract: We present updated cosmological constraints for the KiDS+VIKING-450 cosmic shear data set (KV450) estimated through redshift distributions and photometric s les defined using self-organising maps (SOMs). Our fiducial analysis finds marginal posterior constraints of S 8 ≡ σ 8 Ω m /0.3 = 0.716 −0.038 +0.043 , which are smaller but otherwise consistent with previous works that have applied this data set (|Δ S 8 | = 0.023). We analysed additional s les and redshift distributions set up in three ways: (1) by excluding certain spectroscopic surveys during redshift calibration (2) by excluding lower-confidence spectroscopic redshifts in redshift calibration and (3) by considering only those photometric sources which are jointly calibrated by at least three spectroscopic surveys. In all cases, the method utilised here has been proven to be robust: we find a maximal deviation from our fiducial analysis of |Δ S 8 | ≤ 0.011 for all s les defined and analysed using our SOM. To demonstrate the reduction in systematic biases found within our analysis, we highlight our results when performing redshift calibration without the DEEP2 spectroscopic data set. In this case, we find marginal posterior constraints of S 8 = 0.707 −0.042 +0.046 this is a difference, with respect to the fiducial, that is both significantly smaller and in the opposite direction with regard to the equivalent shift from previous works. These results suggest that our improved cosmological parameter estimates are not sensitive to pathological misrepresentations of photometric sources by the spectroscopy used for direct redshift calibration and, therefore, that this systematic effect cannot be responsible for the observed difference between S 8 estimates made with KV450 and Planck CMB probes.
Publisher: European Southern Observatory (ESO)
Date: 2019
Publisher: Oxford University Press (OUP)
Date: 24-09-2018
Publisher: EDP Sciences
Date: 06-2021
DOI: 10.1051/0004-6361/202040108
Abstract: We present measurements of the radial gravitational acceleration around isolated galaxies, comparing the expected gravitational acceleration given the baryonic matter ( g bar ) with the observed gravitational acceleration ( g obs ), using weak lensing measurements from the fourth data release of the Kilo-Degree Survey (KiDS-1000). These measurements extend the radial acceleration relation (RAR), traditionally measured using galaxy rotation curves, by 2 decades in g obs into the low-acceleration regime beyond the outskirts of the observable galaxy. We compare our RAR measurements to the predictions of two modified gravity (MG) theories: modified Newtonian dynamics and Verlinde’s emergent gravity (EG). We find that the measured relation between g obs and g bar agrees well with the MG predictions. In addition, we find a difference of at least 6 σ between the RARs of early- and late-type galaxies (split by Sérsic index and u − r colour) with the same stellar mass. Current MG theories involve a gravity modification that is independent of other galaxy properties, which would be unable to explain this behaviour, although the EG theory is still limited to spherically symmetric static mass models. The difference might be explained if only the early-type galaxies have significant ( M gas ≈ M ⋆ ) circumgalactic gaseous haloes. The observed behaviour is also expected in Λ-cold dark matter (ΛCDM) models where the galaxy-to-halo mass relation depends on the galaxy formation history. We find that MICE, a ΛCDM simulation with hybrid halo occupation distribution modelling and abundance matching, reproduces the observed RAR but significantly differs from BAHAMAS, a hydrodynamical cosmological galaxy formation simulation. Our results are sensitive to the amount of circumgalactic gas current observational constraints indicate that the resulting corrections are likely moderate. Measurements of the lensing RAR with future cosmological surveys (such as Euclid) will be able to further distinguish between MG and ΛCDM models if systematic uncertainties in the baryonic mass distribution around galaxies are reduced.
Publisher: American Astronomical Society
Date: 03-12-2020
Publisher: American Astronomical Society
Date: 02-2022
Abstract: We report on the detection of a large, extended H i cloud complex in the Galaxy and Mass Survey G23 field, located at a redshift of z ∼ 0.03, observed as part of the MeerKAT Habitat of Galaxies Survey c aign (a pilot survey to explore the mosaicing capabilities of the MeerKAT telescope). The cloud complex, with a total mass of 10 10.0 M ⊙ , lies in proximity to a large galaxy group with M dyn ∼ 10 13.5 M ⊙ . We identify seven H ɪ peak concentrations, interconnected as a tenuous chain structure, extending ∼400 kpc from east to west, with the largest (central) concentration containing 10 9.7 M ⊙ in H ɪ gas distributed across 50 kpc. The main source is not detected in ultraviolet, optical, or infrared imaging. The implied gas mass-to-light ratio ( M H I / L r ) is extreme ( ) even in comparison to other dark clouds . The complex has very little kinematic structure (110 km s −1 ), making it difficult to identify cloud rotation. Assuming pressure support, the total mass of the central concentration is 10 10.2 M ⊙ , while a lower limit to the dynamical mass in the case of full rotational support is 10 10.4 M ⊙ . If the central concentration is a stable structure, it has to contain some amount of unseen matter, but potentially less than is observed for a typical galaxy. It is, however, not clear whether the structure has any gravitationally stable concentrations. We report a faint UV-optical-infrared source in proximity to one of the smaller concentrations in the gas complex, leading to a possible stellar association. The system nature and origins is enigmatic, potentially being the result of an interaction with or within the galaxy group it appears to be associated with.
Publisher: Oxford University Press (OUP)
Date: 26-07-2011
Publisher: Oxford University Press (OUP)
Date: 09-02-2018
DOI: 10.1093/MNRAS/STY310
Publisher: Oxford University Press (OUP)
Date: 14-03-2018
DOI: 10.1093/MNRAS/STY551
Publisher: Oxford University Press (OUP)
Date: 11-02-2017
DOI: 10.1093/MNRAS/STX344
Publisher: Oxford University Press (OUP)
Date: 15-07-2017
Publisher: EDP Sciences
Date: 10-2015
Publisher: EDP Sciences
Date: 05-2021
DOI: 10.1051/0004-6361/202039805
Abstract: We present constraints on extensions to the standard cosmological model of a spatially flat Universe governed by general relativity, a cosmological constant (Λ), and cold dark matter (CDM) by varying the spatial curvature Ω K , the sum of the neutrino masses ∑ m ν , the dark energy equation of state parameter w , and the Hu-Sawicki f ( R ) gravity f R 0 parameter. With the combined 3 × 2 pt measurements of cosmic shear from the Kilo-Degree Survey (KiDS-1000), galaxy clustering from the Baryon Oscillation Spectroscopic Survey (BOSS), and galaxy-galaxy lensing from the overlap between KiDS-1000, BOSS, and the spectroscopic 2-degree Field Lensing Survey, we find results that are fully consistent with a flat ΛCDM model with Ω K = 0.011 −0.057 +0.054 , ∑ m ν 1.76 eV (95% CL), and w = −0.99 −0.13 +0.11 . The f R 0 parameter is unconstrained in our fully non-linear f ( R ) cosmic shear analysis. Considering three different model selection criteria, we find no clear preference for either the fiducial flat ΛCDM model or any of the considered extensions. In addition to extensions to the flat ΛCDM parameter space, we also explore restrictions to common subsets of the flat ΛCDM parameter space by fixing the litude of the primordial power spectrum to the Planck best-fit value, as well as adding external data from supernovae and lensing of the cosmic microwave background (CMB). Neither the beyond-ΛCDM models nor the imposed restrictions explored in this analysis are able to resolve the ∼3 σ tension in S 8 between the 3 × 2 pt constraints and the Planck temperature and polarisation data, with the exception of w CDM, where the S 8 tension is resolved. The tension in the w CDM case persists, however, when considering the joint S 8 − w parameter space. The joint flat ΛCDM CMB lensing and 3 × 2 pt analysis is found to yield tight constraints on Ω m = 0.307 −0.013 +0.008 , σ 8 = 0.769 −0.010 +0.022 , and S 8 = 0.779 −0.013 +0.013 .
Publisher: Oxford University Press (OUP)
Date: 19-07-2017
Publisher: Oxford University Press (OUP)
Date: 14-01-2023
Abstract: Despite the success of galaxy-scale strong gravitational lens studies with Hubble-quality imaging, a number of well-studied strong lenses remains small. As a result, robust comparisons of the lens models to theoretical predictions are difficult. This motivates our application of automated Bayesian lens modelling methods to observations from public data releases of overlapping large ground-based imaging and spectroscopic surveys: Kilo-Degree Survey (KiDS) and Galaxy and Mass Assembly (GAMA), respectively. We use the open-source lens modelling software pyautolens to perform our analysis. We demonstrate the feasibility of strong lens modelling with large-survey data at lower resolution as a complementary avenue to studies that utilize more time-consuming and expensive observations of in idual lenses at higher resolution. We discuss advantages and challenges, with special consideration given to determining background source redshifts from single-aperture spectra and to disentangling foreground lens and background source light. High uncertainties in the best-fitting parameters for the models due to the limits of optical resolution in ground-based observatories and the small s le size can be improved with future study. We give broadly applicable recommendations for future efforts, and with proper application, this approach could yield measurements in the quantities needed for robust statistical inference.
Publisher: EDP Sciences
Date: 04-2019
DOI: 10.1051/0004-6361/201834714
Abstract: We directly constrain the non-linear alignment (NLA) model of intrinsic galaxy alignments, analysing the most representative and complete flux-limited s le of spectroscopic galaxies available for cosmic shear surveys. We measure the projected galaxy position-intrinsic shear correlations and the projected galaxy clustering signal using high-resolution imaging from the Kilo Degree Survey (KiDS) overlapping with the GAMA spectroscopic survey, and data from the Sloan Digital Sky Survey. Separating s les by colour, we make no significant detection of blue galaxy alignments, constraining the blue galaxy NLA litude A IA B = 0.21 −0.36 +0.37 to be consistent with zero. We make robust detections (∼9 σ ) for red galaxies, with A IA R = 3.18 −0.46 +0.47 , corresponding to a net radial alignment with the galaxy density field, and we find no evidence for any scaling of alignments with galaxy luminosity. We provide informative priors for current and future weak lensing surveys, an improvement over de facto wide priors that allow for unrealistic levels of intrinsic alignment contamination. For a colour-split cosmic shear analysis of the final KiDS survey area, we forecast that our priors will improve the constraining power on S 8 and the dark energy equation of state w 0 , by up to 62% and 51%, respectively. Our results indicate, however, that the modelling of red/blue-split galaxy alignments may be insufficient to describe s les with variable central/satellite galaxy fractions.
Publisher: EDP Sciences
Date: 02-2021
DOI: 10.1051/0004-6361/202038831
Abstract: We present the methodology for a joint cosmological analysis of weak gravitational lensing from the fourth data release of the ESO Kilo-Degree Survey (KiDS-1000) and galaxy clustering from the partially overlapping Baryon Oscillation Spectroscopic Survey (BOSS) and the 2-degree Field Lensing Survey (2dFLenS). Cross-correlations between BOSS and 2dFLenS galaxy positions and source galaxy ellipticities have been incorporated into the analysis, necessitating the development of a hybrid model of non-linear scales that blends perturbative and non-perturbative approaches, and an assessment of signal contributions by astrophysical effects. All weak lensing signals were measured consistently via Fourier-space statistics that are insensitive to the survey mask and display low levels of mode mixing. The calibration of photometric redshift distributions and multiplicative gravitational shear bias has been updated, and a more complete tally of residual calibration uncertainties was propagated into the likelihood. A dedicated suite of more than 20 000 mocks was used to assess the performance of covariance models and to quantify the impact of survey geometry and spatial variations of survey depth on signals and their errors. The s ling distributions for the likelihood and the χ 2 goodness-of-fit statistic have been validated, with proposed changes for calculating the effective number of degrees of freedom. The prior volume was explicitly mapped, and a more conservative, wide top-hat prior on the key structure growth parameter S 8 = σ 8 (Ω m /0.3) 1/2 was introduced. The prevalent custom of reporting S 8 weak lensing constraints via point estimates derived from its marginal posterior is highlighted to be easily misinterpreted as yielding systematically low values of S 8 , and an alternative estimator and associated credible interval are proposed. Known systematic effects pertaining to weak lensing modelling and inference are shown to bias S 8 by no more than 0.1 standard deviations, with the caveat that no conclusive validation data exist for models of intrinsic galaxy alignments. Compared to the previous KiDS analyses, S 8 constraints are expected to improve by 20% for weak lensing alone and by 29% for the joint analysis.
Publisher: Oxford University Press (OUP)
Date: 23-06-2018
Publisher: Oxford University Press (OUP)
Date: 23-08-2017
Publisher: Oxford University Press (OUP)
Date: 30-11-2013
Publisher: EDP Sciences
Date: 29-05-2020
DOI: 10.1051/0004-6361/201936154
Abstract: We present a combined tomographic weak gravitational lensing analysis of the Kilo Degree Survey (KV450) and the Dark Energy Survey (DES-Y1). We homogenize the analysis of these two public cosmic shear datasets by adopting consistent priors and modeling of nonlinear scales, and determine new redshift distributions for DES-Y1 based on deep public spectroscopic surveys. Adopting these revised redshifts results in a 0.8 σ reduction in the DES-inferred value for S 8 , which decreases to a 0.5 σ reduction when including a systematic redshift calibration error model from mock DES data based on the MICE2 simulation. The combined KV450+DES-Y1 constraint on S 8 = 0.762 −0.024 +0.025 is in tension with the Planck 2018 constraint from the cosmic microwave background at the level of 2.5 σ . This result highlights the importance of developing methods to provide accurate redshift calibration for current and future weak-lensing surveys.
Publisher: Oxford University Press (OUP)
Date: 05-2006
DOI: 10.1111/J.1365-2966.2006.10268.X
Abstract: We present a catalogue of positions, magnitudes and velocities for 3300 emission-line objects found by the Planetary Nebula Spectrograph in a survey of the Andromeda galaxy, M31. Of these objects, 2615 are found likely to be planetary nebulae (PNe) associated with M31. The survey area covers the whole of M31's disc out to a radius of . Beyond this radius, observations have been made along the major and minor axes, and the Northern Spur and Southern Stream regions. The calibrated data have been checked for internal consistency and compared with other catalogues. With the exception of the very central, high surface brightness region of M31, this survey is complete to a magnitude limit of m5007∼ 23.75, 3.5 mag into the PN luminosity function. We have identified emission-line objects associated with M31's satellites and other background galaxies. We have examined the data from the region tentatively identified as a new satellite galaxy, Andromeda VIII, comparing it to data in the other quadrants of the galaxy. We find that the PNe in this region have velocities that appear to be consistent with membership of M31 itself. The luminosity function of the surveyed PNe is well matched to the usual smooth monotonic function. The only significant spatial variation in the luminosity function occurs in the vicinity of M31's molecular ring, where the luminosities of PNe on the near side of the galaxy are systematically ∼0.2 mag fainter than those on the far side. This difference can be explained naturally by a modest amount of obscuration by the ring. The absence of any difference in luminosity function between bulge and disc suggests that the s le of PNe is not strongly populated by objects whose progenitors are more massive stars. This conclusion is reinforced by the excellent agreement between the number counts of PNe and the R-band light. The number counts of kinematically selected PNe also allow us to probe the stellar distribution in M31 down to very faint limits. There is no indication of a cut-off in M31's disc out to beyond four scalelengths, and no signs of a spheroidal halo population in excess of the bulge out to 10 effective bulge radii. We have also carried out a preliminary analysis of the kinematics of the surveyed PNe. The mean streaming velocity of the M31 disc PNe is found to show a significant asymmetric drift out to large radii. Their velocity dispersion, although initially declining with radius, flattens out to a constant value in the outer parts of the galaxy. There are no indications that the disc velocity dispersion varies with PN luminosity, once again implying that the progenitors of PNe of all magnitudes form a relatively homogeneous old population. The dispersion profile and asymmetric drift results are shown to be mutually consistent, but require that the disc flares with radius if the shape of its velocity ellipsoid remains invariant.
Publisher: EDP Sciences
Date: 2020
DOI: 10.1051/0004-6361/201936678
Abstract: We present a weak lensing detection of filamentary structures in the cosmic web, combining data from the Kilo-Degree Survey, the Red Cluster Sequence Lensing Survey, and the Canada-France-Hawaii Telescope Lensing Survey. The line connecting luminous red galaxies with a separation of 3 − 5 h −1 Mpc was chosen as a proxy for the location of filaments. We measured the average weak lensing shear around ∼11 000 candidate filaments selected in this way from the Sloan Digital Sky Survey. After nulling the shear induced by the dark matter haloes around each galaxy, we reported a 3.4 σ detection of an anisotropic shear signal from the matter that connects them. Adopting a filament density profile, motivated from N -body simulations, the average density at the centre of these filamentary structures was found to be 15 ± 4 times the critical density.
Publisher: Cambridge University Press (CUP)
Date: 2010
DOI: 10.1071/AS09053
Abstract: A heuristic greedy algorithm is developed for efficiently tiling spatially dense redshift surveys. In its first application to the Galaxy and MassAssembly (GAMA) redshift survey we find it rapidly improves the spatial uniformity of our data, and naturally corrects for any spatial bias introduced by the 2dF multi-object spectrograph. We make conservative predictions for the final state of the GAMA redshift survey after our final allocation of time, and can be confident that even if worse than typical weather affects our observations, all of our main survey requirements will be met.
Publisher: EDP Sciences
Date: 03-2021
DOI: 10.1051/0004-6361/201937405
Abstract: We present measurements of f h , the ratio of the aligned components of the projected halo and galaxy ellipticities, for a s le of central galaxies using weak gravitational lensing data from the Kilo-Degree Survey (KiDS). Using a lens galaxy shape estimation that is more sensitive to outer galaxy regions, we find f h = 0.50 ± 0.20 for our full s le and f h = 0.55 ± 0.19 for an intrinsically red sub-s le (that therefore has a higher stellar mass), rejecting the hypothesis that round halos and/or galaxies are not aligned with their parent halo at 2.5 σ and 2.9 σ , respectively. We quantify the 93.4% purity of our central galaxy s le using numerical simulations and overlapping spectroscopy from the Galaxy and Mass Assembly survey. This purity ensures that the interpretation of our measurements is not complicated by the presence of a significant fraction of satellite galaxies. Restricting our central galaxy ellipticity measurement to the inner isophotes, we find f h = 0.34 ± 0.17 for our red sub-s le, suggesting that the outer galaxy regions are more aligned with their dark matter halos than the inner regions. Our results are in agreement with previous studies and suggest that lower mass halos are rounder and/or less aligned with their host galaxy than s les of more massive galaxies, studied in galaxy groups and clusters.
Publisher: Oxford University Press (OUP)
Date: 09-08-2016
Publisher: Oxford University Press (OUP)
Date: 07-02-2013
DOI: 10.1093/MNRAS/STT030
Publisher: EDP Sciences
Date: 07-2023
DOI: 10.1051/0004-6361/202245158
Abstract: We present constraints on the flat Λ cold dark matter cosmological model through a joint analysis of galaxy abundance, galaxy clustering, and galaxy-galaxy lensing observables with the Kilo-Degree Survey. Our theoretical model combines a flexible conditional stellar mass function, which describes the galaxy-halo connection, with a cosmological N -body simulation-calibrated halo model, which describes the non-linear matter field. Our magnitude-limited bright galaxy s le combines nine-band optical-to-near-infrared photometry with an extensive and complete spectroscopic training s le to provide accurate redshift and stellar mass estimates. Our faint galaxy s le provides a background of accurately calibrated lensing measurements. We constrain the structure growth parameter to S 8 = σ 8 √Ω m /0.3 =√0.773 −0.030 +0.028 and the matter density parameter to Ω m = 0.290 −0.017 +0.021 . The galaxy-halo connection model adopted in the work is shown to be in agreement with previous studies. Our constraints on cosmological parameters are comparable to, and consistent with, joint ‘3 × 2pt’ clustering-lensing analyses that additionally include a cosmic shear observable. This analysis therefore brings attention to the significant constraining power in the often excluded non-linear scales for galaxy clustering and galaxy-galaxy lensing observables. By adopting a theoretical model that accounts for non-linear halo bias, halo exclusion, scale-dependent galaxy bias, and the impact of baryon feedback, this work demonstrates the potential for, and a way towards, including non-linear scales in cosmological analyses. Varying the width of the satellite galaxy distribution with an additional parameter yields a strong preference for sub-Poissonian variance, improving the goodness of fit by 0.18 in terms of the reduced χ 2 value (and increasing the p -value by 0.25) compared to a fixed Poisson distribution.
Publisher: Oxford University Press (OUP)
Date: 04-07-2017
Publisher: EDP Sciences
Date: 03-2021
DOI: 10.1051/0004-6361/202039018
Abstract: We present redshift distribution estimates of galaxies selected from the fourth data release of the Kilo-Degree Survey over an area of ∼1000 deg 2 (KiDS-1000). These redshift distributions represent one of the crucial ingredients for weak gravitational lensing measurements with the KiDS-1000 data. The primary estimate is based on deep spectroscopic reference catalogues that are re-weighted with the help of a self-organising map (SOM) to closely resemble the KiDS-1000 sources, split into five tomographic redshift bins in the photometric redshift range 0.1 z B ≤ 1.2. Sources are selected such that they only occupy that volume of nine-dimensional magnitude-space that is also covered by the reference s les (‘gold’ selection). Residual biases in the mean redshifts determined from this calibration are estimated from mock catalogues to be ≲0.01 for all five bins with uncertainties of ∼0.01. This primary SOM estimate of the KiDS-1000 redshift distributions is complemented with an independent clustering redshift approach. After validation of the clustering- z on the same mock catalogues and a careful assessment of systematic errors, we find no significant bias of the SOM redshift distributions with respect to the clustering- z measurements. The SOM redshift distributions re-calibrated by the clustering- z represent an alternative calibration of the redshift distributions with only slightly larger uncertainties in the mean redshifts of ∼0.01 − 0.02 to be used in KiDS-1000 cosmological weak lensing analyses. As this includes the SOM uncertainty, clustering- z are shown to be fully competitive on KiDS-1000 data.
Publisher: EDP Sciences
Date: 14-08-2013
Publisher: EDP Sciences
Date: 10-2020
DOI: 10.1051/0004-6361/202038693
Abstract: We simultaneously present constraints on the stellar-to-halo mass relation for central and satellite galaxies through a weak lensing analysis of spectroscopically classified galaxies. Using overlapping data from the fourth data release of the Kilo-Degree Survey (KiDS), and the Galaxy And Mass Assembly survey (GAMA), we find that satellite galaxies are hosted by halo masses that are 0.53 ± 0.39 dex (68% confidence, 3 σ detection) smaller than those of central galaxies of the same stellar mass (for a stellar mass of log( M ⋆ / M ⊙ ) = 10.6). This is consistent with galaxy formation models, whereby infalling satellite galaxies are preferentially stripped of their dark matter. We find consistent results with similar uncertainties when comparing constraints from a standard azimuthally averaged galaxy-galaxy lensing analysis and a two-dimensional likelihood analysis of the full shear field. As the latter approach is somewhat biased due to the lens incompleteness and as it does not provide any improvement to the precision when applied to actual data, we conclude that stacked tangential shear measurements are best-suited for studies of the galaxy-halo connection.
Publisher: EDP Sciences
Date: 2021
DOI: 10.1051/0004-6361/202038850
Abstract: We present weak lensing shear catalogues from the fourth data release of the Kilo-Degree Survey, KiDS-1000, spanning 1006 square degrees of deep and high-resolution imaging. Our ‘gold-s le’ of galaxies, with well-calibrated photometric redshift distributions, consists of 21 million galaxies with an effective number density of 6.17 galaxies per square arcminute. We quantify the accuracy of the spatial, temporal, and flux-dependent point-spread function (PSF) model, verifying that the model meets our requirements to induce less than a 0.1 σ change in the inferred cosmic shear constraints on the clustering cosmological parameter S 8 = σ 8 √Ω m /0.3.. Through a series of two-point null-tests, we validate the shear estimates, finding no evidence for significant non-lensing B -mode distortions in the data. The PSF residuals are detected in the highest-redshift bins, originating from object selection and/or weight bias. The litude is, however, shown to be sufficiently low and within our stringent requirements. With a shear-ratio null-test, we verify the expected redshift scaling of the galaxy-galaxy lensing signal around luminous red galaxies. We conclude that the joint KiDS-1000 shear and photometric redshift calibration is sufficiently robust for combined-probe gravitational lensing and spectroscopic clustering analyses.
Publisher: Oxford University Press (OUP)
Date: 26-04-2017
DOI: 10.1093/MNRAS/STX998
Publisher: Oxford University Press (OUP)
Date: 12-2003
Publisher: Oxford University Press (OUP)
Date: 20-09-2018
Publisher: Oxford University Press (OUP)
Date: 06-08-2015
Location: United Kingdom of Great Britain and Northern Ireland
Start Date: 2018
End Date: 11-2022
Amount: $390,877.00
Funder: Australian Research Council
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