|2017 - Present||Associate Professor, University of Louisville ‐ Department of Physics and Astronomy|
|2013 - 2016||Research Fellow, Leiden University|
|2012 - 2015||Guest Lecturer, University of Leiden|
|2010 - 2013||Research Fellow, European Space Agency|
|2009 - 2010||Lecturer, University of Cape Town|
|2008 - 2010||Guest Lecturer, National Astrophysics and Space Science Program|
|2008 - 2010||SARCHI Fellow, University of Cape Town|
|2005 - 2008||Postdoctoral Fellow, Space Telescope Science Institute|
|2005 - 2005||Lecturer, University Groningen|
|1998 - 1999||Co-Lecturer, The Open University|
|2000 - 2005||PhD., University of Groningen ‐ Astronomy|
|1995 - 2000||MsC., University of Groningen ‐ Astronomy|
Refereed Publications (102)
Diverse stellar haloes in nearby Milky Way mass disc galaxies. Faculty Scholarship (2017)
We have examined the resolved stellar populations at large galactocentric distances along the minor axis (from 10 kpc up to between 40 and 75 kpc), with limited major axis coverage, of six nearby highly inclined ...
Galaxy and Mass Assembly (GAMA) : active galactic nuclei in pairs of galaxies. Faculty Scholarship (2017)
There exist conflicting observations on whether or not the environment of broad- and narrow-line active galatic nuclei (AGN) differ and this consequently questions the validity of the AGN unification model. The high spectroscopic completeness of ...
First test of Verlinde’s theory of emergent gravity using weak gravitational lensing measurements. Faculty Scholarship (2017)
Verlinde proposed that the observed excess gravity in galaxies and clusters is the consequence of emergent gravity (EG). In this theory, the standard gravitational laws are modified on galactic and larger scales due to the ...
Galaxy And Mass Assembly (GAMA) : detection of low-surface-brightness galaxies from SDSS data. Faculty Scholarship (2016)
We report on a search for new low-surface-brightness galaxies (LSBGs) using Sloan Digital Sky Survey (SDSS) data within the Galaxy And Mass Assembly (GAMA) equatorial fields. The search method consisted of masking objects detected with ...
Dependence of GAMA galaxy halo masses on the cosmic web environment from 100 deg2 of KiDS weak lensing data. Faculty Scholarship (2016)
Galaxies and their dark matter haloes are part of a complex network of mass structures, collectively called the cosmic web. Using the tidal tensor prescription these structures can be classified into four cosmic environments: voids, ...
Galaxy and Mass Assembly (GAMA) : the stellar mass budget of galaxy spheroids and discs. Faculty Scholarship (2016)
We build on a recent photometric decomposition analysis of 7506 Galaxy and Mass Assembly (GAMA) survey galaxies to derive stellar mass function fits to individual spheroid and disc component populations down to a lower mass ...
Evolution of cosmic filaments and of their galaxy population from MHD cosmological simulations. Faculty Scholarship (2016)
Despite containing about a half of the total matter in the Universe, at most wavelengths the filamentary structure of the cosmic web is difficult to observe. In this work, we use large unigrid cosmological simulations ...
Galaxy And Mass Assembly (GAMA) : M–Re relations of z = 0 bulges, discs and spheroids. Faculty Scholarship (2016)
We perform automated bulge + disc decomposition on a sample of ∼7500 galaxies from the Galaxy And Mass Assembly (GAMA) survey in the redshift range of 0.002 < z < 0.06 using Structural Investigation of ...
The bright end of the z~9 and z~10 UV luminosity functions using all five CANDELS fields. Faculty Scholarship (2016)
The deep, wide-area (∼800–900 arcmin2 ) near-infrared/WFC3/IR + Spitzer/IRAC observations over the CANDELS fields have been a remarkable resource for constraining the bright end of high-redshift UV luminosity functions. However, the lack of Hubble Space ...
GAMA/H-ATLAS : common star formation rate indicators and their dependence on galaxy physical parameters. Faculty Scholarship (2016)
We compare common star formation rate (SFR) indicators in the local Universe in the Galaxy and Mass Assembly (GAMA) equatorial fields (∼160 deg2), using ultraviolet (UV) photometry from GALEX, far-infrared and sub-millimetre (sub-mm) photometry from ...
All NIRspec needs is HST/WFC3 pre-imaging? : the use of Milky Way stars in WFC3 imaging to register NIRspec MSA observations. Faculty Scholarship (2016)
The James Webb Space Telescope (JWST) will be an exquisite new near-infrared observatory with imaging and multi-object spectroscopy through ESA’s NIRspec instrument with its unique Micro-Shutter Array (MSA), allowing for slits to be positioned on ...
Galaxy And Mass Assembly (GAMA) : galaxy colour gradients versus colour, structure, and luminosity. Faculty Scholarship (2016)
Using single-component fits to SDSS/UKIDSS images of galaxies in the G09 region of the GAMA survey we study radial colour gradients across the galaxy population. We use the multi-wavelength information provided by MegaMorph analysis of ...
Galaxy And Mass Assembly (GAMA) : understanding the wavelength dependence of galaxy structure with bulge-disc decompositions. Faculty Scholarship (2016)
With a large sample of bright, low-redshift galaxies with optical–near-IR imaging from the GAMA survey we use bulge-disc decompositions to understand the wavelength-dependent behaviour of single-Sérsic structural measurements. We denote the variation in single-Sérsic index ...
Erratum: “Milky Way red dwarfs in the Borg survey; galactic scale-height and the distribution of dwarfs stars in WFC3 imaging". Faculty Scholarship (2016)
In the catalog of M-dwarfs presented in Holwerda et al. (2014, H14 hereafter), there is an issue with the conversion from celestial coordinates to Galactic ones, done with PYEPHEM a wrapper around a trusted and ...
Galaxy And Mass Assembly : accurate panchromatic photometry from optical priors using LAMBDAR. Faculty Scholarship (2016)
We present the Lambda Adaptive Multi-Band Deblending Algorithm in R (LAMBDAR), a novel code for calculating matched aperture photometry across images that are neither pixel- nor PSF-matched, using prior aperture definitions derived from high-resolution optical ...
WISE x SuperCOSMOS photometric redshift catalog : 20 million galaxies over 3pi steradians. Faculty Scholarship (2016)
We cross-match the two currently largest all-sky photometric catalogs—mid-infrared Wide-field Infrared Survey Explorer and SuperCOSMOS scans of UKST/POSS-II photographic plates—to obtain a new galaxy sample that covers 3π steradians. In order to characterize and purify ...
z 7 galaxies with red Spitzer/IRAC [3.6]–[4.5] colors in the full CANDELS data set : the brightest-known galaxies AT z ∼ 7–9 and a probable spectroscopic confirmation at z = 7.48. Faculty Scholarship (2016)
We identify four unusually bright (H160,AB < 25.5) galaxies from Hubble Space Telescope (HST) and Spitzer CANDELS data with probable redshifts z ∼ 7–9. These identifications include the brightest-known galaxies to date at z ...
The size and shape of the Milky Way disc and halo from M-type brown dwarfs in the BoRG survey. Faculty Scholarship (2016)
We have identified 274 M-type brown dwarfs in the Hubble Space Telescope's Wide Field Camera 3 pure parallel fields from the Brightest of Reionizing Galaxies (BoRG) survey for high-redshift galaxies. These are near-infrared observations with ...
Galaxy And Mass Assembly (GAMA) : the stellar mass budget by galaxy type. Faculty Scholarship (2016)
We report an expanded sample of visual morphological classifications from the Galaxy and Mass Assembly survey phase two, which now includes 7556 objects (previously 3727 in phase one). We define a local (z < 0.06) ...
Galaxy And Mass Assembly (GAMA): stellar mass growth of spiral galaxies in the cosmic web. Faculty Scholarship (2016)
We look for correlated changes in stellar mass and star formation rate (SFR) along filaments in the cosmic web by examining the stellar masses and UV-derived SFRs of 1799 ungrouped and unpaired spiral galaxies that ...
The GHOSTS survey – II. The diversity of halo colour and metallicity profiles of massive disc galaxies. Faculty Scholarship (2016)
We study the stellar halo colour properties of six nearby massive highly inclined disc galaxies using Hubble space telescope Advanced Camera for Surveys and Wide Field Camera 3 observations in both F606W and F814W filters ...
Galaxy And Mass Assembly (GAMA) : Panchromatic Data Release (far-UV–far-IR) and the low-z energy budget. Faculty Scholarship (2016)
We present the Galaxy And Mass Assembly (GAMA) Panchromatic Data Release (PDR) constituting over 230 deg2 of imaging with photometry in 21 bands extending from the far-UV to the far-IR. These data complement our spectroscopic ...
Galaxy And Mass Assembly (GAMA) : growing up in a bad neighbourhood – how do low-mass galaxies become passive? Faculty Scholarship (2016)
Both theoretical predictions and observations of the very nearby Universe suggest that low-mass galaxies(log10[M*/M⊙] < 9.5) are likely to remain star-forming unless they are affected by their local environment. To test this premise, we compare ...
Globular cluster populations : results including S4G late-type galaxies. Faculty Scholarship (2016)
Using 3.6 and 4.5 μm images of 73 late-type, edge-on galaxies from the S4 G survey, we compare the richness of the globular cluster populations of these galaxies to those of early-type galaxies that we ...