Publications by Lance Miller

The fourth data release of the Kilo-Degree Survey: Ugri imaging and nine-band optical-IR photometry over 1000 square degrees

Astronomy and Astrophysics 625 (2019)

K Kuijken, C Heymans, A Dvornik, H Hildebrandt, JTA De Jong, AH Wright, T Erben, M Bilicki, B Giblin, HY Shan, F Getman, A Grado, H Hoekstra, L Miller, N Napolitano, M Paolilo, M Radovich, P Schneider, W Sutherland, M Tewes, C Tortora, EA Valentijn, GA Verdoes Kleijn

© ESO 2019. 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 ZYJHKs 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 (5σ 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.

Consistent cosmic shear in the face of systematics: A B -mode analysis of KiDS-450, DES-SV and CFHTLenS

Astronomy and Astrophysics 624 (2019)

M Asgari, C Heymans, H Hildebrandt, L Miller, P Schneider, A Amon, A Choi, T Erben, C Georgiou, J Harnois-Deraps, K Kuijken

© ESO 2019. We analyse three public cosmic shear surveys; the Kilo-Degree Survey (KiDS-450), the Dark Energy Survey (DES-SV) and the Canada France Hawaii Telescope Lensing Survey (CFHTLenS). Adopting the "COSEBIs" statistic to cleanly and completely separate the lensing E-modes from the non-lensing B-modes, we detect B-modes in KiDS-450 and CFHTLenS at the level of ∼2.7σ. For DES-SV we detect B-modes at the level of 2.8σ in a non-tomographic analysis, increasing to a 5.5σB-mode detection in a tomographic analysis. In order to understand the origin of these detected B-modes we measure the B-mode signature of a range of different simulated systematics including PSF leakage, random but correlated PSF modelling errors, camera-based additive shear bias and photometric redshift selection bias. We show that any correlation between photometric-noise and the relative orientation of the galaxy to the point-spread-function leads to an ellipticity selection bias in tomographic analyses. This work therefore introduces a new systematic for future lensing surveys to consider. We find that the B-modes in DES-SV appear similar to a superposition of the B-mode signatures from all of the systematics simulated. The KiDS-450 and CFHTLenS B-mode measurements show features that are consistent with a repeating additive shear bias.

Towards emulating cosmic shear data: Revisiting the calibration of the shear measurements for the Kilo-Degree Survey

Astronomy and Astrophysics 624 (2019)

A Kannawadi, H Hoekstra, L Miller, M Viola, I Fenech Conti, R Herbonnet, T Erben, C Heymans, H Hildebrandt, K Kuijken, M Vakili, AH Wright

© ESO 2019. 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 lensfit, and find through a range of sensitivity tests that lensfit 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 samples 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.

KiDS-i-800: comparing weak gravitational lensing measurements from same-sky surveys


A Amon, C Heymans, D Klaes, T Erben, C Blake, H Hildebrandt, H Hoekstra, K Kuijken, L Miller, CB Morrison, A Choi, JTA de Jong, K Glazebrook, N Irisarri, B Joachimi, S Joudaki, A Kannawadi, C Lidman, N Napolitano, D Parkinson, P Schneider, E van Uitert, M Viola, C Wolf

Weak-lensing study in VOICE survey - I. Shear measurement


L Fu, D Liu, M Radovich, X Liu, C Pan, Z Fan, G Covone, M Vaccari, V Amaro, M Brescia, M Capaccioli, D De Cicco, A Grado, L Limatola, L Miller, NR Napolitano, M Paolillo, G Pignata

Weak lensing study in VOICE survey - II. Shear bias calibrations


D Liu, L Fu, X Liu, M Radovich, C Wang, C Pan, Z Fan, G Covone, M Vaccari, MT Botticella, M Capaccioli, D De Cicco, A Grado, L Miller, N Napolitano, M Paolillo, G Pignata

Radio weak lensing shear measurement in the visibility domain - II. Source extraction

Monthly Notices of the Royal Astronomical Society 476 (2018) 2053-2062

M Rivi, L Miller

© 2018 The Author(s). This paper extends the method introduced in Rivi et al. (2016b) to measure galaxy ellipticities in the visibility domain for radio weak lensing surveys. In that paper, we focused on the development and testing of the method for the simple case of individual galaxies located at the phase centre, and proposed to extend it to the realistic case of many sources in the field of view by isolating visibilities of each source with a faceting technique. In this second paper, we present a detailed algorithm for source extraction in the visibility domain and show its effectiveness as a function of the source number density by running simulations of SKA1-MID observations in the band 950-1150 MHz and comparing original and measured values of galaxies' ellipticities. Shear measurements from a realistic population of 104 galaxies randomly located in a field of view of 1 deg2 (i.e. the source density expected for the current radio weak lensing survey proposal with SKA1) are also performed. At SNR ≥ 10, the multiplicative bias is only a factor 1.5 worse than what found when analysing individual sources, and is still comparable to the bias values reported for similar measurement methods at optical wavelengths. The additive bias is unchanged from the case of individual sources, but it is significantly larger than typically found in optical surveys. This bias depends on the shape of the uv coverage and we suggest that a uv-plane weighting scheme to produce a more isotropic shape could reduce and control additive bias.

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


S Joudaki, C Blake, A Johnson, A Amon, M Asgari, A Choi, T Erben, K Glazebrook, J Harnois-Deraps, C Heymans, H Hildebrandt, H Hoekstra, D Klaes, K Kuijken, C Lidman, A Mead, L Miller, D Parkinson, GB Poole, P Schneider, M Viola, C Wolf

A rapid occultation event in NGC 3227

Monthly Notices of the Royal Astronomical Society 481 (2018) 2470-2478

TJ Turner, JN Reeves, V Braito, A Lobban, S Kraemer, L Miller

© 2018 The Author(s). NGC 3227 exhibits rapid flux and spectral variability in the X-ray band. To understand this behaviour, we conducted a coordinated observing campaign using 320 ks of XMM- Newton exposures together with 160 ks of overlapping NuSTAR observations, spanning a month. Here, we present a rapid variability event that occurs toward the end of the campaign. The spectral hardening event is accompanied by a change in the depth of an unresolved transition array (UTA), whose time-dependent behaviour is resolved using the RGS data. This UTA fingerprint allows us to identify this as a transit event, where a clump of gas having NH ~ 5 × 1022 atoms cm-2, log Ξ ~ 2 occults ~ 60 per cent of the continuum photons over the course of approximately a day. This occulting gas is likely associated with clouds in the inner broad-line region. An additional zone of gas with lower column and higher ionization, matches the outflow velocity of the variable zone, and may represent transmission through the cloud limb.

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


E van Uitert, B Joachimi, S Joudaki, A Amon, C Heymans, F Koehlinger, M Asgari, C Blake, A Choi, T Erben, DJ Farrow, J Harnois-Deraps, H Hildebrandt, H Hoekstra, TD Kitching, D Klaes, K Kuijken, J Merten, L Miller, R Nakajima, P Schneider, E Valentijn, M Viola

Cosmological simulations for combined-probe analyses: Covariance and neighbour-exclusion bias

Monthly Notices of the Royal Astronomical Society 481 (2018) 1337-1367

J Harnois-Déraps, A Amon, A Choi, V Demchenko, C Heymans, A Kannawadi, R Nakajima, E Sirks, L van Waerbeke, YC Cai, B Giblin, H Hildebrandt, H Hoekstra, L Miller, T Tröster

© 2018 The Author(s). We present a public suite of weak-lensing mock data, extending the Scinet Light Cone Simulations (SLICS) to simulate cross-correlation analyses with different cosmological probes. These mocks include Kilo Degree Survey (KiDS)-450-and LSST-like lensing data, cosmic microwave background lensing maps and simulated spectroscopic surveys that emulate the Galaxy And Mass Assembly, BOSS, and 2-degree Field Lensing galaxy surveys. With 844 independent realizations, our mocks are optimized for combined-probe covariance estimation, which we illustrate for the case of a joint measurement involving cosmic shear, galaxy-galaxy lensing, and galaxy clustering from KiDS-450 and BOSS data. With their high spatial resolution, the SLICS are also optimal for predicting the signal for novel lensing estimators, for the validation of analysis pipelines, and for testing a range of systematic effects such as the impact of neighbour-exclusion bias on the measured tomographic cosmic shear signal. For surveys like KiDS and Dark Energy Survey, where the rejection of neighbouring galaxies occurs within ~2 arcsec, we show that the measured cosmic shear signal will be biased low, but by less than a per cent on the angular scales that are typically used in cosmic shear analyses. The amplitude of the neighbour-exclusion bias doubles in deeper, LSST-like data. The simulation products described in this paper are made available at

Lensing is low: cosmology, galaxy formation or new physics?


A Leauthaud, S Saito, S Hilbert, A Barreira, S More, M White, S Alam, P Behroozi, K Bundy, J Coupon, T Erben, C Heymans, H Hildebrandt, R Mandelbaum, L Miller, B Moraes, MES Pereira, SA Rodriguez-Torres, F Schmidt, H-Y Shan, M Viel, F Villaescusa-Navarro

Cross-correlating Planck tSZ with RCSLenS weak lensing: Implications for cosmology and AGN feedback

Monthly Notices of the Royal Astronomical Society 471 (2017) 1565-1580

A Hojjati, T Tröster, J Harnois-Déraps, IG McCarthy, L van Waerbeke, A Choi, T Erben, C Heymans, H Hildebrandt, G Hinshaw, YZ Ma, L Miller, M Viola, H Tanimura

© 2017 The Authors. We present measurements of the spatial mapping between (hot) baryons and the total matter in theUniverse, via the cross-correlation between the thermal Sunyaev-Zeldovich (tSZ)map from Planck and the weak gravitational lensing maps from theRed Cluster Sequence Lensing Survey (RCSLenS). The cross-correlations are performed on the map level where all the sources (including diffuse intergalactic gas) contribute to the signal. We consider two configurationspace correlation function estimators, ξ y-κ and ξ y-γt , and a Fourier-space estimator, C ℓy-κ , in our analysis. We detect a significant correlation out to 3° of angular separation on the sky. Based on statistical noise only, we can report 13σ and 17σ detections of the cross-correlation using the configuration-space y-κ and y-γ t estimators, respectively. Including a heuristic estimate of the sampling variance yields a detection significance of 7σ and 8σ, respectively. A similar level of detection is obtained from the Fourier-space estimator, C ℓy-κ . As each estimator probes different dynamical ranges, their combination improves the significance of the detection. We compare our measurements with predictions from the cosmo-OverWhelmingly Large Simulations suite of cosmological hydrodynamical simulations, where different galactic feedback models are implemented.We find that a model with considerable active galactic nuclei (AGN) feedback that removes large quantities of hot gas from galaxy groups and Wilkinson Microwave Anisotropy Probe 7-yr best-fitting cosmological parameters provides the bestmatch to the measurements. All baryonic models in the context of a Planck cosmology overpredict the observed signal. Similar cosmological conclusions are drawn when we employ a halo model with the observed 'universal' pressure profile.

KiDS-450: testing extensions to the standard cosmological model


S Joudaki, A Mead, C Blake, A Choi, J de Jong, T Erben, IF Conti, R Herbonnet, C Heymans, H Hildebrandt, H Hoekstra, B Joachimi, D Klaes, F Kohlinger, K Kuijken, J McFarland, L Miller, P Schneider, M Viola

Calibration of weak-lensing shear in the Kilo-Degree Survey


IF Conti, R Herbonnet, H Hoekstra, J Merten, L Miller, M Viola

CODEX weak lensing: Concentration of galaxy clusters at Z ~ 0.5

Monthly Notices of the Royal Astronomical Society 468 (2017) 1092-1116

N Cibirka, ES Cypriano, F Brimioulle, D Gruen, T Erben, L van Waerbeke, L Miller, A Finoguenov, C Kirkpatrick, J Patrick Henry, E Rykoff, E Rozo, R Dupke, JP Kneib, H Shan, P Spinelli

© 2017 The Authors. Published by Oxford University Press on behalf of the Royal Astronomical Society. We present a stacked weak-lensing analysis of 27 richness selected galaxy clusters at 0.40 ≤ z ≤ 0.62 in the COnstrain Dark Energy with X-ray galaxy clusters (CODEX) survey. The fields were observed in five bands with the Canada-France-Hawaii Telescope (CFHT). We measure the stacked surface mass density profile with a 14σ significance in the radial range 0.1 < R Mpc h-1 < 2.5. The profile is well described by the halo model, with the main halo term following a Navarro-Frenk-White profile (NFW) profile and including the off-centring effect. We select the background sample using a conservative colour-magnitude method to reduce the potential systematic errors and contamination by cluster member galaxies. We perform a Bayesian analysis for the stacked profile and constrain the best-fitting NFW parameters M200c = 6.6+1.0-0.8 × 1014 h -1M⊙ and c200c = 3.7+0.7-0.6. The off-centring effect was modelled based on previous observational results found for redMaPPer Sloan Digital Sky Survey clusters. Our constraints on M200c and c200c allow us to investigate the consistency with numerical predictions and select a concentration-mass relation to describe the high richness CODEX sample. Comparing our best-fitting values forM200c and C200c with other observational surveys at different redshifts, we find no evidence for evolution in the concentration-mass relation, though it could be mitigated by particular selection functions. Similar to previous studies investigating the X-ray luminosity-mass relation, our data suggest a lower evolution than expected from self-similarity.

Measuring light echoes in NGC 4051

Monthly Notices of the Royal Astronomical Society 467 (2017) 3924-3933

TJ Turner, L Miller, JN Reeves, V Braito

© 2017 The Authors. Five archived X-ray observations of NGC 4051, taken using the NuSTAR observatory, have been analysed, revealing lags between flux variations in bands covering a wide range of X-ray photon energy. In all pairs of bands compared, the harder band consistently lags the softer band by at least 1000 s, at temporal frequencies ∼5 × 10 −5 Hz. In addition, soft-band lags up to 400 s are measured at frequencies ∼2 × 10 −4 Hz. Light echoes from an excess of soft band emission in the inner accretion disc cannot explain the lags in these data, as they are seen in cross-correlations with energy bands where the softer band is expected to have no contribution from reflection. The basic properties of the time delays have been parametrized by fitting a top-hat response function that varies with photon energy, taking fully into account the covariance between measured time lag values. The low-frequency hard-band lags and the transition to soft-band lags are consistent with time lags arising as reverberation delays from circumnuclear scattering of X-rays, although greater model complexity is required to explain the entire spectrum of lags. The scattered fraction increases with increasing photon energy as expected, and the scattered fraction is high, indicating the reprocessor to have a global covering fraction ∼50 per cent around the continuum source. Circumnuclear material, possibly associated with a disc wind at a few hundred gravitational radii from the primary X-ray source, may provide suitable reprocessing.

KiDS-450: tomographic cross-correlation of galaxy shear with Planck lensing


J Harnois-Deraps, T Troster, NE Chisari, C Heymans, L van Waerbeke, M Asgari, M Bilicki, A Choi, T Erben, H Hildebrandt, H Hoekstra, S Joudaki, K Kuijken, J Merten, L Miller, N Robertson, P Schneider, M Viola

The third data release of the Kilo-Degree Survey and associated data products


JTA de Jong, GAV Kleijn, T Erben, H Hildebrandt, K Kuijken, G Sikkema, M Brescia, M Bilicki, NR Napolitano, V Amaro, KG Begeman, DR Boxhoorn, H Buddelmeijer, S Cavuoti, F Getman, A Grado, E Helmich, Z Huang, N Irisarri, F La Barbera, G Longo, JP McFarland, R Nakajima, M Paolillo, E Puddu, M Radovich, A Rifatto, C Tortora, EA Valentijn, C Vellucci, W-J Vriend, A Amon, C Blake, A Choi, IF Conti, SDJ Gwyn, R Herbonnet, C Heymans, H Hoekstra, D Klaes, J Merten, L Miller, P Schneider, M Viola

Galaxy-halo alignments in the Horizon-AGN cosmological hydrodynamical simulation


NE Chisari, N Koukoufilippas, A Jindal, S Peirani, RS Beckmann, S Codis, J Devriendt, L Miller, Y Dubois, C Laigle, A Slyz, C Pichon