Publications by Cameron Alexander Campbell Lemon

Tdcosmo Xvii. New Time Delays in 22 Lensed Quasars From Optical Monitoring with the Eso-vst 2.6m and Mpg 2.2m Telescopes

Frédéric Courbin, Vivien François Bonvin, Aymeric Alexandre Galan, Eric Gérard Guy Paic, Cameron Alexander Campbell Lemon

We present new time delays, the main ingredient of time delay cosmography, for 22 lensed quasars resulting from high-cadence r-band monitoring on the 2.6 m ESO VLT Survey Telescope and Max-Planck-Gesellschaft 2.2 m telescope. Each lensed quasar was typical ...

EDP SCIENCES S A2025

JWST lensed quasar dark matter survey – I. Description and first results

Cameron Alexander Campbell Lemon

All rights reserved.The flux ratios of gravitationally lensed quasars provide a powerful probe of the nature of dark matter. Importantly, these ratios are sensitive to small-scale structure, irrespective of the presence of baryons. This sensitivity may all ...

2024

Nine lensed quasars and quasar pairs discovered through spatially extended variability in Pan-STARRS

Frédéric Courbin, Aymeric Alexandre Galan, Cameron Alexander Campbell Lemon

We present the proof of concept of a method for finding strongly lensed quasars using their spatially extended photometric variability through difference imaging in cadenced imaging survey data. We applied the method to Pan-STARRS, starting with an initial ...

Edp Sciences S A2024

Searching for Strong Gravitational Lenses

Frédéric Courbin, Cameron Alexander Campbell Lemon

Strong gravitational lenses provide unique laboratories for cosmological and astrophysical investigations, but they must first be discovered - a task that can be met with significant contamination by other astrophysical objects and asterisms. Here we revie ...

Springer2024

Strong lensing by edge-on galaxies in UNIONS

Frédéric Courbin, Elodie Marie Charlène Savary, Cameron Alexander Campbell Lemon

Current searches for galaxy-scale strong lenses focus on massive Luminous Red Galaxies but tend to overlook late-type lenses, in part because of their smaller Einstein radii. We take advantage of the superb seeing of the UNIONS survey in the r-band to perf ...

2024

Gravitationally lensed quasars in Gaia - IV. 150 new lenses, quasar pairs, and projected quasars

Frédéric Courbin, Aymeric Alexandre Galan, Cameron Alexander Campbell Lemon, Adriano Agnello

We report the spectroscopic follow-up of 175 lensed quasar candidates selected using Gaia Data Release 2 observations following Paper III of this series. Systems include 86 confirmed lensed quasars and a further 17 likely lensed quasars based on imaging an ...

OXFORD UNIV PRESS2023

PS J2107-1611: A new wide-separation, quadruply imaged lensed quasar with flux ratio anomalies

Frédéric Courbin, Cameron Alexander Campbell Lemon

We report the discovery of PS J2107-1611, a fold-configuration 4.3 ''-separation quadruply lensed quasar with a bright lensed arc. It was discovered using a convolutional neural network on Pan-STARRS gri images of pre-selected quasar candidates with multip ...

Edp Sciences S A2023

STRIDES: automated uniform models for 30 quadruply imaged quasars

Frédéric Courbin, Martin Raoul Robert Millon, Cameron Alexander Campbell Lemon

Gravitational time delays provide a powerful one-step measurement of H-0, independent of all other probes. One key ingredient in time-delay cosmography are high-accuracy lens models. Those are currently expensive to obtain, both, in terms of computing and ...

OXFORD UNIV PRESS2023

Uncovering a population of gravitational lens galaxies with magnified standard candle SN Zwicky

Johan Richard, Johannes Richard Cornelis Geerit Kruis, Rémy Elie Joseph, Cameron Alexander Campbell Lemon

Detecting gravitationally lensed supernovae is among the biggest challenges in astronomy. It involves a combination of two very rare phenomena: catching the transient signal of a stellar explosion in a distant galaxy and observing it through a nearly perfe ...

NATURE PORTFOLIO2023

J1721+8842: a gravitationally lensed binary quasar with a proximate damped Lyman-alpha absorber

Frédéric Courbin, Martin Raoul Robert Millon, Eric Gérard Guy Paic, Hung-Hsu Chan, Cameron Alexander Campbell Lemon, Adriano Agnello

High-redshift binary quasars provide key insights into mergers and quasar activity, and are useful tools for probing the spatial kinematics and chemistry of galaxies along the line of sight. However, only three sub-10-kpc binaries have been confirmed above ...

EDP SCIENCES S A2022

Discovery of strongly lensed quasars in the Ultraviolet Near Infrared Optical Northern Survey (UNIONS)

Elodie Marie Charlène Savary, Martin Raoul Robert Millon, Eric Gérard Guy Paic, Hung-Hsu Chan, Karina Alexandra Rojas Olate, Benjamin Yvan Alexandre Clement, Cameron Alexander Campbell Lemon, Georgios Vernardos

We report the discovery of five new doubly imaged lensed quasars from the first 2500 square degrees of the ongoing Canada-France Imaging Survey (CFIS), which is a component of the Ultraviolet Near Infrared Optical Northern Survey. The systems are preselect ...

EDP SCIENCES S A2022

Finding quadruply imaged quasars with machine learning - I. Methods

Cameron Alexander Campbell Lemon

Strongly lensed quadruply imaged quasars (quads) arc extraordinary objects. They arc very rare in the sky and yet they provide unique information about a wide range of topics, including the expansion history and the composition of the Universe, the distrib ...

2022

Evidence for a milliparsec-separation supermassive binary black hole with quasar microlensing

Frédéric Courbin, Martin Raoul Robert Millon, Eric Gérard Guy Paic, Hung-Hsu Chan, Cameron Alexander Campbell Lemon

We report periodic oscillations in the 15-year-long optical light curve of the gravitationally lensed quasar Q J0158-4325 at z(s) = 1.29. The signal is enhanced during a high magnification microlensing event of the quasar that the fainter lensed image, B, ...

EDP SCIENCES S A2022

Search of strong lens systems in the Dark Energy Survey using convolutional neural networks

Frédéric Courbin, Elodie Marie Charlène Savary, Aymeric Alexandre Galan, Hung-Hsu Chan, Karina Alexandra Rojas Olate, Benjamin Yvan Alexandre Clement, Cameron Alexander Campbell Lemon, Georgios Vernardos

We present our search for strong lens, galaxy-scale systems in the first data release of the Dark Energy Survey (DES), based on a color-selected parent sample of 18 745 029 luminous red galaxies (LRGs). We used a convolutional neural network (CNN) to grade ...

EDP SCIENCES S A2022

X-ray absorption and reprocessing in the z similar to 2.5 lensed quasar 2MASS J1042+1641

Cameron Alexander Campbell Lemon

We present new broad-band X-ray observations of the z similar to 2.5 lensed quasar 2MASS J1042+1641, combining XMM-Newton, Chandra, and NuSTAR to provide coverage of the X-ray spectrum over the 0.3-40 keV bandpass in the observed frame, corresponding to th ...

2022

Strong lensing in UNIONS: Toward a pipeline from discovery to modeling

Frédéric Courbin, Elodie Marie Charlène Savary, Hung-Hsu Chan, Karina Alexandra Rojas Olate, Benjamin Yvan Alexandre Clement, Cameron Alexander Campbell Lemon, Georgios Vernardos

We present a search for galaxy-scale strong gravitational lenses in the initial 2500 square degrees of the Canada-France Imaging Survey (CFIS). We designed a convolutional neural network (CNN) committee that we applied to a selection of 2 344 002 r-band im ...

EDP SCIENCES S A2022

Discovery of two bright high-redshift gravitationally lensed quasars revealed by Gaia

Cameron Alexander Campbell Lemon

We present the discovery and preliminary characterisation of two high-redshift gravitationally lensed quasar systems in Gaia Data Release 2 (DR2). Candidates with multiple close-separation Gaia detections and quasar-like colours in WISE, Pan-STARRS, and DE ...

2022

COSMOGRAIL: XIX. Time delays in 18 strongly lensed quasars from 15 years of optical monitoring star

Malte Tewes, Georges Meylan, Frédéric Courbin, Vivien François Bonvin, Martin Raoul Robert Millon, Aymeric Alexandre Galan, Eric Gérard Guy Paic, Rémy Elie Joseph, Olga Tihhonova, Hung-Hsu Chan, Cameron Alexander Campbell Lemon

We present the results of 15 years of monitoring lensed quasars, which was conducted by the COSMOGRAIL programme at the Leonhard Euler 1.2 m Swiss Telescope. The decade-long light curves of 23 lensed systems are presented for the first time. We complement ...

EDP SCIENCES S A2020

TDCOSMO II. Six new time delays in lensed quasars from high-cadence monitoring at the MPIA 2.2m telescope

Frédéric Courbin, Sun Hee Kim, Vivien François Bonvin, Martin Raoul Robert Millon, Eric Gérard Guy Paic, Hung-Hsu Chan, Karina Alexandra Rojas Olate, Cameron Alexander Campbell Lemon, Adriano Agnello

We present six new time-delay measurements obtained from Rc-band monitoring data acquired at the Max Planck Institute for Astrophysics (MPIA) 2.2m telescope at La Silla observatory between October 2016 and February 2020. The lensed quasars HE0047 1756, WG0 ...

EDP SCIENCES S A2020

The STRong lensing Insights into the Dark Energy Survey (STRIDES) 2017/2018 follow-up campaign: discovery of 10 lensed quasars and 10 quasar pairs

Frédéric Courbin, Cameron Alexander Campbell Lemon

We report the results of the STRong lensing Insights into the Dark Energy Survey (STRIDES) follow-up campaign of the late 2017/early 2018 season. We obtained spectra of 65 lensed quasar candidates with ESO Faint Object Spectrograph and Camera 2 on the NTT ...

OXFORD UNIV PRESS2020