Lyndsay Old
A5060960019- Galaxies: Formation, Evolution, Phenomena
- Astronomy and Astrophysical Research
- Stellar, planetary, and galactic studies
- Gamma-ray bursts and supernovae
- Cosmology and Gravitation Theories
- Remote Sensing in Agriculture
- Astrophysics and Star Formation Studies
- Astrophysics and Cosmic Phenomena
- Advanced Vision and Imaging
- Scientific Research and Discoveries
- Leaf Properties and Growth Measurement
- Advanced Image Processing Techniques
- CCD and CMOS Imaging Sensors
- Retinal Imaging and Analysis
- Image and Signal Denoising Methods
- Calibration and Measurement Techniques
- Adaptive optics and wavefront sensing
- Radio Astronomy Observations and Technology
- Astronomical Observations and Instrumentation
- Plant Water Relations and Carbon Dynamics
- Computational Physics and Python Applications
- Cardiovascular Health and Disease Prevention
- Sparse and Compressive Sensing Techniques
European Space Astronomy Centre
2019-2022
University of Toronto
2017-2020
University of Nottingham
2013-2018
Barcelona Institute for Science and Technology
2016
University of Illinois Urbana-Champaign
2016
Cerro Tololo Inter-American Observatory
2014
We introduce the THE THREE HUNDRED project, an endeavour to model 324 large galaxy clusters with full-physics hydrodynamical re-simulations. Here we present data set and study differences observations for fundamental cluster properties scaling relations. find that modelled are generally in reasonable agreement respect baryonic fractions gas relations at redshift z = 0. However, there still some (model-dependent) differences, such as central galaxies being too massive, colours (g - r) bluer...
We study the stellar mass functions (SMFs) of star-forming and quiescent galaxies in 11 galaxy clusters at 1.0<z<1.4, drawn from Gemini Observations Galaxies Rich Early Environments (GOGREEN) survey. Based on more than 500 hours Gemini/GMOS spectroscopy, deep multi-band photometry taken with a range observatories, we probe SMFs down to limit 10^9.7 Msun (10^9.5 for galaxies). At this early epoch, fraction is already highly elevated compared field same redshift. The quenched excess (QFE)...
This article is the second in a series which we perform an extensive comparison of various galaxy-based cluster mass estimation techniques that utilise positions, velocities and colours galaxies. Our aim to quantify scatter, systematic bias completeness masses derived from diverse set 25 methods using two contrasting mock galaxy catalogues based on sophisticated halo occupation model semi-analytic model. Analysing 968 clusters, find wide range RMS errors log M200c delivered by different...
This paper is the first in a series which we perform an extensive comparison of various galaxy-based cluster mass estimation techniques that utilise positions, velocities and colours galaxies. Our primary aim to test performance these on diverse set models will increase complexity. We begin by providing participating methods with data from simple model delivers idealised clusters, enabling us quantify underlying scatter intrinsic techniques. The mock catalogue based Halo Occupation...
Abstract We study the star-forming (SF) population of galaxies within a sample 209 IR-selected galaxy clusters at 0.3 ≤ z 1.1 in ELAIS-N1 and XMM -LSS fields, exploiting first HSC-SSP data release. The large area depth these allow us to analyze dependence SF fraction, f , on stellar mass environment separately. Using R / 200 trace environment, we observe decrease from field toward cluster core, which strongly depends redshift. show an accelerated growth quiescent environment: versus relation...
We present results on the environmental dependence of star-forming galaxy main sequence in 11 cluster fields at $1.0 < z 1.5$ from Gemini Observations Galaxies Rich Early Environments Survey (GOGREEN) survey. use a homogeneously selected sample field and galaxies whose membership is derived dynamical analysis. Using [OII]-derived star formation rates (SFRs), we find that have suppressed SFRs fixed stellar mass comparison to their counterparts by factor 1.4 $\pm$ 0.1 ($\sim3.3\sigma$) across...
The Dark Energy Survey (DES) is a next generation optical survey aimed at understanding the accelerating expansion of universe using four complementary methods: weak gravitational lensing, galaxy cluster counts, baryon acoustic oscillations, and Type Ia supernovae. To perform 5000 sq-degree wide field 30 supernova surveys, DES Collaboration built Camera (DECam), 3 square-degree, 570-Megapixel CCD camera that was installed prime focus Blanco 4-meter telescope Cerro Tololo Inter-American...
We use TheThreeHundred project, a suite of 324 resimulated massive galaxy clusters embedded in broad range environments, to investigate (i) how the gas content surrounding haloes correlates with phase-space position at $z=0$, and (ii) role that ram pressure plays this correlation. By stacking all normalised planes containing 169287 subhaloes, we show halo is tightly correlated position. At $\sim\,1.5-2\,\text{R}_{\text{200}}$ cluster dark matter halo, find an extremely steep decline...
We describe a new Large Program in progress on the Gemini North and South telescopes: Observations of Galaxies Rich Early Environments (GOGREEN). This is an imaging deep spectroscopic survey 21 galaxy systems at $1<z<1.5$, selected to span factor $>10$ halo mass. The scientific objectives include measuring role environment evolution low-mass galaxies, dynamics stellar contents their host haloes. targets are from SpARCS, SPT, COSMOS SXDS surveys, be evolutionary counterparts today's clusters...
We study the star formation histories (SFHs) and mass-weighted ages of 331 UVJ-selected quiescent galaxies in 11 galaxy clusters field at 1<z<1.5 from Gemini Observations Galaxies Rich Early ENvironments (GOGREEN) survey. determine SFHs individual by simultaneously fitting rest-frame optical spectroscopy broadband photometry to stellar population models. confirm that are consistent with more massive having on average earlier times. Comparing found those field, we find $M_\ast<10^{11.3}$...
ABSTRACT Astronomical images are essential for exploring and understanding the Universe. Optical telescopes capable of deep observations, such as Hubble Space Telescope (HST), heavily oversubscribed in Community. Images also often contain additive noise, which makes denoising a mandatory step post-processing data before further analysis. In order to maximize efficiency information gain astronomical imaging, we turn machine learning. We propose Astro U-net, convolutional neural network image...
We present the first public data release of GOGREEN and GCLASS surveys galaxies in dense environments, spanning a redshift range $0.8<z<1.5$. The consist deep, multiwavelength photometry extensive Gemini GMOS spectroscopy 26 overdense systems ranging halo mass from small groups to most massive clusters. objective both projects was primarily understand how evolution is affected by their environment, determine physical processes that lead quenching star formation. There an emphasis on...
With the advent of wide-field cosmological surveys, we are approaching samples hundreds thousands galaxy clusters. While such large numbers will help reduce statistical uncertainties, control systematics in cluster masses is crucial. Here examine effects an important source systematic uncertainty galaxy-based mass estimation techniques: presence significant dynamical substructure. Dynamical substructure manifests as dynamically distinct subgroups phase-space, indicating 'unrelaxed' state....
We present a study of comparison spin distributions subhaloes found associated with host halo. The are within two cosmological simulation families Milky Way-like galaxies, namely the Aquarius and GHALO simulations. These simulations use different gravity codes cosmologies. employ 10 substructure finders, which span wide range methodologies from simple overdensity in configuration space to full 6D phase analysis particles. subject results common post-processing pipeline analyse consistent...
We study the systematic bias introduced when selecting spectroscopic redshifts of brighter cluster galaxies to estimate velocity dispersion galaxy clusters from both simulated and observational catalogues. select with Ngal > 50 at five low redshift snapshots a semi-analytic model catalogue, catalogue SDSS DR8 groups across range 0.021<z<0.098. employ various selection techniques explore whether is simply due lack dynamical information or result an underlying physical process occurring in...
The primary difficulty in measuring dynamical masses of galaxy clusters from data lies the separation between true cluster members interloping galaxies along line sight. We study impact membership contamination and incompleteness on mass estimates obtained with 25 commonly used techniques applied to nearly 1000 mock clusters. show that all methods overestimate or underestimate when contaminated incomplete samples respectively. This appears be main source intrinsic scatter scaling relation....
The Dark Energy Survey (DES) is an operating optical survey aimed at understanding the accelerating expansion of universe using four complementary methods: weak gravitational lensing, galaxy cluster counts, baryon acoustic oscillations, and Type Ia supernovae. To perform 5000 sq-degree wide field 30 supernova surveys, DES Collaboration built Camera (DECam), a 3 square-degree, 570-Megapixel CCD camera that was installed prime focus Blanco 4-meter telescope Cerro Tololo Inter-American...
We measure the rate of environmentally-driven star formation quenching in galaxies at $z\sim 1$, using eleven massive ($M\approx 2\times10^{14}\,\mathrm{M}_\odot$) galaxy clusters spanning a redshift range $1.0<z<1.4$ from GOGREEN sample. identify three different types transition galaxies: "green valley" (GV) identified their rest-frame $(NUV-V)$ and $(V-J)$ colours; "blue quiescent" (BQ) galaxies, found blue end quiescent sequence $(U-V)$ colour; spectroscopic post-starburst (PSB) galaxies....
Recent observations have shown that the environmental quenching of galaxies at z ~ 1 is qualitatively different to in local Universe. However, physical origin these differences has not yet been elucidated. In addition, while low-redshift comparisons between observed trends and predictions cosmological hydrodynamical simulations are now routine, there relatively few higher redshifts date. Here we confront three state-of-the-art suites (BAHAMAS+MACSIS, EAGLE+Hydrangea, IllustrisTNG) with field...
Abstract Utilizing the SDSS-DR13 spectroscopic data set, we create a new publicly available catalog of 1800 galaxy clusters (GalWeight cluster catalog, GalWCat19 ) and corresponding 34,471 identified member galaxies. The are from overdensities in redshift phase space. GalWeight technique introduced by Abdullah et al. is then applied to identify members. completeness ( procedure followed determine mass tested on Bolshoi N -body simulations. range between 0.01 0.2 have masses (0.4–14) × 10 14...
We present a new method for tracing the evolution of BCGs from $z\sim 2$ to 0$. conclude on basis semi-analytical models that best select BCG progenitors at is hybrid environmental density and stellar mass ranking approach. Ultimately we are able retrieve 45\% progenitors. apply this CANDELS UDS data construct progenitor sample high redshift. furthermore populate comparisons in local universe by using SDSS with statistically likely contamination ensure fair comparison between low redshifts....
We calculate H$\alpha$-based star formation rates and determine the rate-stellar mass relation for members of three SpARCS clusters at $z \sim 1.6$ serendipitously identified field galaxies similar redshifts to clusters. find in cluster throughout our range stellar masses. The results are comparable those seen other redshifts, consistent with previous photometric evidence little quenching activity One possible explanation is that have been accreted too recently show signs environmental...
We present results on the rest-frame H-band luminosity functions (LFs) of red-sequence galaxies in seven clusters at 1.0 < z 1.3 from Gemini Observations Galaxies Rich Early Environments Survey. Using deep GMOS and IRAC 3.6 μm imaging, we identify measure their LFs down to . By stacking entire sample, derive a shallow faint-end slope , suggesting that there is deficit faint high redshift. comparing stacked LF our sample with ∼ 0.6, find an evolution end red sequence over ∼2.6 Gyr between two...
Abstract Environmental effects are crucial to the understanding of evolution galaxies in dense environments, such as galaxy clusters. Using large field view SITELLE, unique imaging Fourier transform spectrograph at Canada–France–Hawaii Telescope, we able obtain 2D spectral information for a and complete sample cluster out infall region. We describe pipeline developed identify emission-line (ELGs) from datacube using cross-correlation techniques. present results based on spatial offsets...
Abstract We present the results of measured shapes 832 galaxies in 11 galaxy clusters at 1.0 < z 1.4 from GOGREEN survey. measure axis ratio ( q ), minor to major axis, cluster near-infrared Hubble Space Telescope imaging using Sérsic profile fitting and compare them with a field sample. find that median both star-forming quiescent increases stellar mass, similar field. Comparing distributions between four mass bins, for are consistent those Conversely, two environments distinct, most...