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Henk Hoekstra

Publications and source records attributed to Henk Hoekstra.

At least 91 records · Page 5Linked to original sources
arXiv2019

Studying galaxy troughs and ridges using Weak Gravitational Lensing with the Kilo-Degree Survey

We study projected underdensities in the cosmic galaxy density field known as 'troughs', and their overdense counterparts, which we call 'ridges'. We identify these regions using a bright sample of foreground galaxies from the photometric Kilo-Degree Survey (KiDS), specifically selected to mimic the spectroscopic Galaxy And Mass Assembly survey (GAMA). Using background galaxies from KiDS, we measure the weak gravitational lensing profiles of the troughs/ridges. We quantify the amplitude of their lensing strength $A$ as a function of galaxy density percentile rank $P$ and galaxy overdensity $δ$, and find that the skewness in the galaxy density distribution is reflected in the total mass distribution measured by weak lensing. We interpret our results using the mock galaxy catalogue from the Marenostrum Institut de Ciències de l'Espai (MICE) simulation, and find a good agreement with our observations. Using signal-to-noise weights derived from the Scinet LIghtCone Simulations (SLICS) mock catalogue we optimally stack the lensing signal of KiDS troughs with an angular radius $θ_A$ = {5,10,15,20} arcmin, resulting in {16.8,14.9,10.13,7.55} $σ$ detections. Finally, we select troughs using a volume-limited sample of galaxies, split into two redshift bins between 0.1 < z < 0.3. For troughs/ridges with transverse comoving radius $R_A$ = 1.9 Mpc/h, we find no significant difference in the comoving Excess Surface Density as a function of $P$ and $δ$ between the low- and high-redshift sample. Using the MICE and SLICS mocks we predict that trough and ridge evolution could be detected with gravitational lensing using deeper and wider lensing surveys, such as those from the Large Synoptic Survey Telescope and Euclid.

astro-ph.CO↗
arXiv2019

The dependence of intrinsic alignment of galaxies on wavelength using KiDS and GAMA

The outer regions of galaxies are more susceptible to the tidal interactions that lead to intrinsic alignments of galaxies. The resulting alignment signal may therefore depend on the passband if the colours of galaxies vary spatially. To quantify this, we measured the shapes of galaxies with spectroscopic redshifts from the GAMA survey using deep gri imaging data from the KiloDegree Survey. The performance of the moment-based shape measurement algorithm DEIMOS was assessed using dedicated image simulations, which showed that the ellipticities could be determined with an accuracy better than 1% in all bands. Additional tests for potential systematic errors did not reveal any issues. We measure a significant difference of the alignment signal between the g,r and i-band observations. This difference exceeds the amplitude of the linear alignment model on scales below 2 Mpc/h. Separating the sample into central/satellite and red/blue galaxies, we find that that the difference is dominated by red satellite galaxies.

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arXiv2018

The PAU Survey: star-galaxy classification with multi narrow-band data

Classification of stars and galaxies is a well-known astronomical problem that has been treated using different approaches, most of them relying on morphological information. In this paper, we tackle this issue using the low-resolution spectra from narrow band photometry, provided by the PAUS (Physics of the Accelerating Universe) survey. We find that, with the photometric fluxes from the 40 narrow band filters and without including morphological information, it is possible to separate stars and galaxies to very high precision, 98.4% purity with a completeness of 98.8% for objects brighter than I = 22.5. This precision is obtained with a Convolutional Neural Network as a classification algorithm, applied to the objects' spectra. We have also applied the method to the ALHAMBRA photometric survey and we provide an updated classification for its Gold sample.

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arXiv2018

Luminous red galaxies in the Kilo Degree Survey: selection with broad-band photometry and weak lensing measurements

We use the overlap between multiband photometry of the Kilo-Degree Survey (KiDS) and spectroscopic data based on the Sloan Digital Sky Survey (SDSS) and Galaxy And Mass Assembly (GAMA) to infer the colour-magnitude relation of red-sequence galaxies. We then use this inferred relation to select luminous red galaxies (LRGs) in the redshift range of $0.1<z<0.7$ over the entire KiDS Data Release 3 footprint. We construct two samples of galaxies with different constant comoving densities and different luminosity thresholds. The selected red galaxies have photometric redshifts with typical photo-z errors of $σ_z \sim 0.014 (1+z)$ that are nearly uniform with respect to observational systematics. This makes them an ideal set of galaxies for lensing and clustering studies. As an example, we use the KiDS-450 cosmic shear catalogue to measure the mean tangential shear signal around the selected LRGs. We detect a significant weak lensing signal for lenses out to $z \sim 0.7$.

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arXiv2018

Unveiling Galaxy Bias via the Halo Model, KiDS and GAMA

We measure the projected galaxy clustering and galaxy-galaxy lensing signals using the Galaxy And Mass Assembly (GAMA) survey and Kilo-Degree Survey (KiDS) to study galaxy bias. We use the concept of non-linear and stochastic galaxy biasing in the framework of halo occupation statistics to constrain the parameters of the halo occupation statistics and to unveil the origin of galaxy biasing. The bias function $Γ_{\text{gm}}(r_{\text{p}})$, where $r_{\text{p}}$ is the projected comoving separation, is evaluated using the analytical halo model from which the scale dependence of $Γ_{\text{gm}}(r_{\text{p}})$, and the origin of the non-linearity and stochasticity in halo occupation models can be inferred. Our observations unveil the physical reason for the non-linearity and stochasticity, further explored using hydrodynamical simulations, with the stochasticity mostly originating from the non-Poissonian behaviour of satellite galaxies in the dark matter haloes and their spatial distribution, which does not follow the spatial distribution of dark matter in the halo. The observed non-linearity is mostly due to the presence of the central galaxies, as was noted from previous theoretical work on the same topic. We also see that overall, more massive galaxies reveal a stronger scale dependence, and out to a larger radius. Our results show that a wealth of information about galaxy bias is hidden in halo occupation models. These models should therefore be used to determine the influence of galaxy bias in cosmological studies.

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arXiv2018

The galaxy-subhalo connection in low-redshift galaxy clusters from weak gravitational lensing

We measure the gravitational lensing signal around satellite galaxies in a sample of galaxy clusters at $z<0.15$ by combining high-quality imaging data from the Canada-France-Hawaii Telescope with a large sample of spectroscopically-confirmed cluster members. We use extensive image simulations to assess the accuracy of shape measurements of faint, background sources in the vicinity of bright satellite galaxies. We find a small but significant bias, as light from the lenses makes the shapes of background galaxies appear radially aligned with the lens. We account for this bias by applying a correction that depends on both lens size and magnitude. We also correct for contamination of the source sample by cluster members. We use a physically-motivated definition of subhalo mass, namely the mass bound to the subhalo, $m_\mathrm{bg}$, similar to definitions used by common subhalo finders in numerical simulations. Binning the satellites by stellar mass we provide a direct measurement of the subhalo-to-stellar-mass relation, $\log m_\mathrm{bg}/\mathrm{M}_\odot = (11.54\pm0.05) + (0.95\pm0.10)\log[m_\star/(2\times10^{10}\mathrm{M}_\odot)]$. This best-fitting relation implies that, at a stellar mass $m_\star\sim3\times10^{10}\,\mathrm{M}_\odot$, subhalo masses are roughly 50 per cent of those of central galaxies, and this fraction decreases at higher stellar masses. We find some evidence for a sharp change in the total-to-stellar mass ratio around the clusters' scale radius, which could be interpreted as galaxies within the scale radius having suffered more strongly from tidal stripping, but remain cautious regarding this interpretation.

astro-ph.GA↗
arXiv2018

Calibration of colour gradient bias in shear measurement using HST/CANDELS data

Accurate shape measurements are essential to infer cosmological parameters from large area weak gravitational lensing studies. The compact diffraction-limited point-spread function (PSF) in space-based observations is greatly beneficial, but its chromaticity for a broad band observation can lead to new subtle effects that could hitherto be ignored: the PSF of a galaxy is no longer uniquely defined and spatial variations in the colours of galaxies result in biases in the inferred lensing signal. Taking Euclid as a reference, we show that this colourgradient bias (CG bias) can be quantified with high accuracy using available multi-colour Hubble Space Telescope (HST) data. In particular we study how noise in the HST observations might impact such measurements and find this to be negligible. We determine the CG bias using HST observations in the F606W and F814W filters and observe a correlation with the colour, in line with expectations, whereas the dependence with redshift is weak. The biases for individual galaxies are generally well below 1%, which may be reduced further using morphological information from the Euclid data. Our results demonstrate that CG bias should not be ignored, but it is possible to determine its amplitude with sufficient precision, so that it will not significantly bias the weak lensing measurements using Euclid data.

astro-ph.CO↗
arXiv2018

KiDS+GAMA: Cosmology constraints from a joint analysis of cosmic shear, galaxy-galaxy lensing and angular clustering

We present cosmological parameter constraints from a joint analysis of three cosmological probes: the tomographic cosmic shear signal in $\sim$450 deg$^2$ of data from the Kilo Degree Survey (KiDS), the galaxy-matter cross-correlation signal of galaxies from the Galaxies And Mass Assembly (GAMA) survey determined with KiDS weak lensing, and the angular correlation function of the same GAMA galaxies. We use fast power spectrum estimators that are based on simple integrals over the real-space correlation functions, and show that they are practically unbiased over relevant angular frequency ranges. We test our full pipeline on numerical simulations that are tailored to KiDS and retrieve the input cosmology. By fitting different combinations of power spectra, we demonstrate that the three probes are internally consistent. For all probes combined, we obtain $S_8\equiv σ_8 \sqrt{Ω_{\rm m}/0.3}=0.800_{-0.027}^{+0.029}$, consistent with Planck and the fiducial KiDS-450 cosmic shear correlation function results. Marginalising over wide priors on the mean of the tomographic redshift distributions yields consistent results for $S_8$ with an increase of $28\%$ in the error. The combination of probes results in a $26\%$ reduction in uncertainties of $S_8$ over using the cosmic shear power spectra alone. The main gain from these additional probes comes through their constraining power on nuisance parameters, such as the galaxy intrinsic alignment amplitude or potential shifts in the redshift distributions, which are up to a factor of two better constrained compared to using cosmic shear alone, demonstrating the value of large-scale structure probe combination.

astro-ph.CO↗
arXiv2018

Precise weak lensing constraints from deep high-resolution $K_\mathrm{s}$ images: VLT/HAWK-I analysis of the super-massive galaxy cluster RCS2$J$232727.7$-$020437 at $z=0.70$

We demonstrate that deep good-seeing VLT/HAWK-I $K_\mathrm{s}$ images complemented with $g$+$z$-band photometry can yield a sensitivity for weak lensing studies of massive galaxy clusters at redshifts \mbox{$0.7\lesssim z \lesssim 1.1$}, which is almost identical to the sensitivity of HST/ACS mosaics of single-orbit depth. Key reasons for this good performance are the excellent image quality frequently achievable for $K_\mathrm{s}$ imaging from the ground, a highly effective photometric selection of background galaxies, and a galaxy ellipticity dispersion that is noticeably lower than for optically observed high-redshift galaxy samples. Incorporating results from the 3D-HST and UltraVISTA surveys we also obtained a more accurate calibration of the source redshift distribution than previously achieved for similar optical weak lensing data sets. Here we studied the extremely massive galaxy cluster RCS2$J$232727.7$-$020437 (\mbox{$z=0.699$}), combining deep VLT/\mbox{HAWK-I} $K_\mathrm{s}$ images (point spread function with a 0\farcs35 full width at half maximum) with LBT/LBC photometry. The resulting weak lensing mass reconstruction suggests that the cluster consists of a single overdensity, which is detected with a peak significance of $10.1σ$. We constrained the cluster mass to \mbox{$M_\mathrm{200c}/(10^{15} \mathrm{M}_\odot) =2.06^{+0.28}_{-0.26}(\mathrm{stat.})\pm 0.12 (\mathrm{sys.})$} assuming a spherical Navarro, Frenk \& White model and simulation-based priors on the concentration, making it one of the most massive galaxy clusters known in the \mbox{$z\gtrsim 0.7$} Universe. We also cross-checked the HAWK-I measurements through an analysis of overlapping HST/ACS images, yielding fully consistent estimates of the lensing signal.

astro-ph.CO↗
arXiv2017

XMM-Newton X-ray and HST weak gravitational lensing study of the extremely X-ray luminous galaxy cluster ClJ120958.9+495352 ($z=0.902$)

Observations of relaxed, massive and distant clusters can provide important tests of standard cosmological models e.g. using the gas mass fraction. We study the very luminous, high redshift ($z=0.902$) galaxy cluster ClJ120958.9+495352 using XMM-Newton data and measure the temperature profile and cooling time to investigate the dynamical status with respect to the presence of a cool core as well as global cluster properties. We use HST weak lensing data to estimate its total mass and determine the gas mass fraction. We perform a spectral analysis using an XMM-Newton observation of 15ks cleaned exposure time. As the treatment of the background is crucial, we use two different approaches to account for the background emission to verify our results. We account for point-spread-function effects and deproject our results to estimate the gas mass fraction of the cluster. We measure weak lensing galaxy shapes from mosaic HST imaging and select background galaxies photometrically in combination with imaging data from the William Herschel Telescope. The X-ray luminosity of ClJ120958.9+495352 in the 0.1-2.4keV band estimated from our XMM-Newton data is $L_X = (13.4_{-1.0}^{+1.2})\times10^{44}$erg/s and thus it is one of the most X-ray luminous clusters known at similarly high redshift. We find clear indications for the presence of a cool core from the temperature profile and the central cooling time, which is very rare at such high redshifts. Based on the weak lensing analysis we estimate a cluster mass of $M_\mathrm{500}/10^{14}M_\odot=4.4^{+2.2}_{-2.0}(\mathrm{stat.})\pm0.6(\mathrm{sys.})$ and a gas mass fraction of $f_\mathrm{gas,2500} = 0.11_{-0.03}^{+0.06}$ in good agreement with previous findings for high redshift and local clusters.

astro-ph.CO↗
arXiv2017

KiDS-450 + 2dFLenS: Cosmological parameter constraints from weak gravitational lensing tomography and overlapping redshift-space galaxy clustering

We perform a combined analysis of cosmic shear tomography, galaxy-galaxy lensing tomography, and redshift-space multipole power spectra (monopole and quadrupole) using 450 deg$^2$ of imaging data by the Kilo Degree Survey (KiDS) overlapping with two spectroscopic surveys: the 2-degree Field Lensing Survey (2dFLenS) and the Baryon Oscillation Spectroscopic Survey (BOSS). We restrict the galaxy-galaxy lensing and multipole power spectrum measurements to the overlapping regions with KiDS, and self-consistently compute the full covariance between the different observables using a large suite of $N$-body simulations. We methodically analyze different combinations of the observables, finding that galaxy-galaxy lensing measurements are particularly useful in improving the constraint on the intrinsic alignment amplitude (by 30%, positive at $3.5σ$ in the fiducial data analysis), while the multipole power spectra are useful in tightening the constraints along the lensing degeneracy direction (e.g. factor of two stronger matter density constraint in the fiducial analysis). The fully combined constraint on $S_8 \equiv σ_8 \sqrt{Ω_{\rm m}/0.3} = 0.742 \pm 0.035$, which is an improvement by 20% compared to KiDS alone, corresponds to a $2.6σ$ discordance with Planck, and is not significantly affected by fitting to a more conservative set of scales. Given the tightening of the parameter space, we are unable to resolve the discordance with an extended cosmology that is simultaneously favored in a model selection sense, including the sum of neutrino masses, curvature, evolving dark energy, and modified gravity. The complementarity of our observables allows for constraints on modified gravity degrees of freedom that are not simultaneously bounded with either probe alone, and up to a factor of three improvement in the $S_8$ constraint in the extended cosmology compared to KiDS alone.

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arXiv2017

KiDS-450: Cosmological Constraints from Weak Lensing Peak Statistics-I: Inference from Analytical Prediction of High Signal-to-Noise Ratio Convergence Peaks

This paper is the first of a series of papers constraining cosmological parameters with weak lensing peak statistics using $\sim 450~\rm deg^2$ of imaging data from the Kilo Degree Survey (KiDS-450). We measure high signal-to-noise ratio (SNR: $ν$) weak lensing convergence peaks in the range of $3<ν<5$, and employ theoretical models to derive expected values. These models are validated using a suite of simulations. We take into account two major systematic effects, the boost factor and the effect of baryons on the mass-concentration relation of dark matter haloes. In addition, we investigate the impacts of other potential astrophysical systematics including the projection effects of large scale structures, intrinsic galaxy alignments, as well as residual measurement uncertainties in the shear and redshift calibration. Assuming a flat $Λ$CDM model, we find constraints for $S_{\rm 8}=σ_{\rm 8}(Ω_{\rm m}/0.3)^{0.5}=0.746^{+0.046}_{-0.107}$ according to the degeneracy direction of the cosmic shear analysis and $Σ_{\rm 8}=σ_{\rm 8}(Ω_{\rm m}/0.3)^{0.38}=0.696^{+0.048}_{-0.050}$ based on the derived degeneracy direction of our high-SNR peak statistics. The difference between the power index of $S_{\rm 8}$ and in $Σ_{\rm 8}$ indicates that combining the two probes has the potential to break the degeneracy in $σ_{\rm 8}$ and $Ω_{\rm m}$. Our results are consistent with the cosmic shear tomographic correlation analysis of the same dataset and $\sim 2σ$ lower than the Planck 2016 results.

astro-ph.CO↗
arXiv2017

A first constraint on the average mass of ultra diffuse galaxies from weak gravitational lensing

The recent discovery of thousands of ultra diffuse galaxies (UDGs) in nearby galaxy clusters has opened a new window into the process of galaxy formation and evolution. Several scenarios have been proposed to explain the formation history of UDGs, and their ability to survive in the harsh cluster environments. A key requirement to distinguish between these scenarios is a measurement of their halo masses which, due to their low surface brightnesses, has proven difficult if one relies on stellar tracers of the potential. We exploit weak gravitational lensing, a technique that does not depend on these baryonic tracers, to measure the average subhalo mass of 784 UDGs selected in 18 clusters at $z\leq0.09$. Our sample of UDGs has a median stellar mass $\langle m_\star\rangle=2\times10^8\,\mathrm{M}_\odot$ and a median effective radius $\langle r_\mathrm{eff}\rangle=2.8$ kpc. We constrain the average mass of subhaloes within 30 kpc to $\log m_\mathrm{UDG}(r<30\,\mathrm{kpc})/\mathrm{M}_\odot\leq10.99$ at 95 per cent credibility, implying an effective virial mass $\log m_{200}/\mathrm{M}_\odot\leq11.80$, and a lower limit on the stellar mass fraction within 10 kpc of 1.0 per cent. Such mass is consistent with a simple extrapolation of the subhalo-to-stellar mass relation of typical satellite galaxies in massive clusters. However, our analysis is not sensitive to scatter about this mean mass; the possibility remains that extreme UDGs reside in haloes as massive as the Milky Way.

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arXiv2017

KiDS-450: Cosmological Constraints from Weak Lensing Peak Statistics - II: Inference from Shear Peaks using N-body Simulations

We study the statistics of peaks in a weak lensing reconstructed mass map of the first 450 square degrees of the Kilo Degree Survey. The map is computed with aperture masses directly applied to the shear field with an NFW-like compensated filter. We compare the peak statistics in the observations with that of simulations for various cosmologies to constrain the cosmological parameter $S_8 = σ_8 \sqrt{Ω_{\rm m}/0.3}$, which probes the ($Ω_{\rm m}, σ_8$) plane perpendicularly to its main degeneracy. We estimate $S_8=0.750\pm0.059$, using peaks in the signal-to-noise range $0 \leq {\rm S/N} \leq 4$, and accounting for various systematics, such as multiplicative shear bias, mean redshift bias, baryon feedback, intrinsic alignment, and shear-position coupling. These constraints are $\sim25\%$ tighter than the constraints from the high significance peaks alone ($3 \leq {\rm S/N} \leq 4$) which typically trace single-massive halos. This demonstrates the gain of information from low-S/N peaks. However we find that including ${\rm S/N} < 0$ peaks does not add further information. Our results are in good agreement with the tomographic shear two-point correlation function measurement in KiDS-450. Combining shear peaks with non-tomographic measurements of the shear two-point correlation functions yields a $\sim20\%$ improvement in the uncertainty on $S_8$ compared to the shear two-point correlation functions alone, highlighting the great potential of peaks as a cosmological probe.

astro-ph.CO↗
arXiv2017

The abundance of ultra-diffuse galaxies from groups to clusters: UDGs are relatively more common in more massive haloes

In recent years, multiple studies have reported substantial populations of large, low-surface-brightness galaxies 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 differentiate between models is whether UDGs have counterparts in lower-mass host haloes, and what their abundance as a function of halo mass is. In this study we 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 M200=10^12 Msun, a regime where approximately only 1 in 10 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<R200) $\propto$ M200^(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<R200) $\propto$ M200^(0.78+/-0.05). This shows that UDGs are relatively more abundant, compared to bright galaxies, in massive clusters than in groups. We discuss implications, but whether this difference is related to a higher destruction rate of UDGs in groups, or whether massive haloes have a positive effect on their formation, is not yet clear.

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arXiv2017

Implications of a wavelength dependent PSF for weak lensing measurements

The convolution of galaxy images by the point-spread function (PSF) is the dominant source of bias for weak gravitational lensing studies, and an accurate estimate of the PSF is required to obtain unbiased shape measurements. The PSF estimate for a galaxy depends on its spectral energy distribution (SED), because the instrumental PSF is generally a function of the wavelength. In this paper we explore various approaches to determine the resulting `effective' PSF using broad-band data. Considering the Euclid mission as a reference, we find that standard SED template fitting methods result in biases that depend on source redshift, although this may be remedied if the algorithms can be optimised for this purpose. Using a machine-learning algorithm we show that, at least in principle, the required accuracy can be achieved with the current survey parameters. It is also possible to account for the correlations between photometric redshift and PSF estimates that arise from the use of the same photometry. We explore the impact of errors in photometric calibration, errors in the assumed wavelength dependence of the PSF model and limitations of the adopted template libraries. Our results indicate that the required accuracy for Euclid can be achieved using the data that are planned to determine photometric redshifts.

astro-ph.CO↗
arXiv2017

KiDS-450: Testing extensions to the standard cosmological model

We test extensions to the standard cosmological model with weak gravitational lensing tomography using 450 deg$^2$ of imaging data from the Kilo Degree Survey (KiDS). In these extended cosmologies, which include massive neutrinos, nonzero curvature, evolving dark energy, modified gravity, and running of the scalar spectral index, we also examine the discordance between KiDS and cosmic microwave background measurements from Planck. The discordance between the two datasets is largely unaffected by a more conservative treatment of the lensing systematics and the removal of angular scales most sensitive to nonlinear physics. The only extended cosmology that simultaneously alleviates the discordance with Planck and is at least moderately favored by the data includes evolving dark energy with a time-dependent equation of state (in the form of the $w_0-w_a$ parameterization). In this model, the respective $S_8 = σ_8 \sqrt{Ω_{\rm m}/0.3}$ constraints agree at the $1σ$ level, and there is `substantial concordance' between the KiDS and Planck datasets when accounting for the full parameter space. Moreover, the Planck constraint on the Hubble constant is wider than in LCDM and in agreement with the Riess et al. (2016) direct measurement of $H_0$. The dark energy model is moderately favored as compared to LCDM when combining the KiDS and Planck measurements, and remains moderately favored after including an informative prior on the Hubble constant. In both of these scenarios, marginalized constraints in the $w_0-w_a$ plane are discrepant with a cosmological constant at the $3σ$ level. Moreover, KiDS constrains the sum of neutrino masses to 4.0 eV (95% CL), finds no preference for time or scale dependent modifications to the metric potentials, and is consistent with flatness and no running of the spectral index. The analysis code is public at https://github.com/sjoudaki/kids450

astro-ph.CO↗
arXiv2017

The stellar-to-halo mass relation of GAMA galaxies from 100 square degrees of KiDS weak lensing data

We study the stellar-to-halo mass relation of central galaxies in the range 9.7 5x10^10 h^-2 M_sun, the stellar mass increases with halo mass as ~M_h^0.25. The ratio of dark matter to stellar mass has a minimum at a halo mass of 8x10^11 h^-1 M_sun with a value of M_h/M_*=56_-10^+16 [h]. We also use the GAMA group catalogue to select centrals and satellites in groups with five or more members, which trace regions in space where the local matter density is higher than average, and determine for the first time the stellar-to-halo mass relation in these denser environments. We find no significant differences compared to the relation from the full sample, which suggests that the stellar-to-halo mass relation does not vary strongly with local density. Furthermore, we find that the stellar-to-halo mass relation of central galaxies can also be obtained by modelling the lensing signal and stellar mass function of satellite galaxies only, which shows that the assumptions to model the satellite contribution in the halo model do not significantly bias the stellar-to-halo mass relation. Finally, we show that the combination of weak lensing with the stellar mass function can be used to test the purity of group catalogues.

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