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Hung-Hsu Chan

Cette personne a quitté l’EPFL

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Publications associées (51)

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

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

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

Boson star normal modes

Hung-Hsu Chan

Boson stars are gravitationally bound objects that arise in ultralight dark matter models and form in the centers of galactic halos or axion miniclusters. We systematically study the excitations of a boson star, taking into account the mixing between posit ...

Springer Nature2023

Condensation and evaporation of boson stars

Hung-Hsu Chan

Axion-like particles, including the QCD axion, are well-motivated dark matter candidates. Numerical simulations have revealed coherent soliton configurations, also known as boson stars, in the centers of axion halos. We study evolution of axion solitons im ...

Springer Nature2024

Survey of Gravitationally Lensed Objects in HSC Imaging (SuGOHI). II. Environments and Line-of-Sight Structure of Strong Gravitational Lens Galaxies to z similar to 0.8

Hung-Hsu Chan

We investigate the local and line-of-sight (LOS) overdensities of strong gravitational lens galaxies using wide-area multiband imaging from the Hyper Suprime-Cam Subaru Strategic Program. We present 41. new definite or probable lens candidates discovered i ...

2018

The GOGREEN survey: the environmental dependence of the star-forming galaxy main sequence at 1.0 < z < 1.5

Pascale Jablonka, Hung-Hsu Chan

We present results on the environmental dependence of the star-forming galaxy main sequence in 11 galaxy cluster fields at 1.0 < z < 1.5 from the Gemini Observations of Galaxies in Rich Early Environments Survey (GOGREEN) survey. We use a homogeneously sel ...

OXFORD UNIV PRESS2020

A SHARP view of H0LiCOW: H-0 from three time-delay gravitational lens systems with adaptive optics imaging

Frédéric Courbin, Hung-Hsu Chan, Vivien François Bonvin, Martin Raoul Robert Millon

We present the measurement of the Hubble constant, H-0, with three strong gravitational lens systems, We describe a blind analysis of both PG 1115+080 and 11E0435-1223 as well as an extension of our previous analysis of RXJ 1131-1231. For each lens, we com ...

OXFORD UNIV PRESS2019

HOLISMOKES VII. Time-delay measurement of strongly lensed Type Ia supernovae using machine learning

Vivien François Bonvin, Hung-Hsu Chan

The Hubble constant (H-0) is one of the fundamental parameters in cosmology, but there is a heated debate around the > 4 sigma tension between the local Cepheid distance ladder and the early Universe measurements. Strongly lensed Type Ia supernovae (LSNe I ...

EDP SCIENCES S A2022

TDCOSMO: I. An exploration of systematic uncertainties in the inference of H-0 from time-delay cosmography

Frédéric Courbin, Hung-Hsu Chan, Martin Raoul Robert Millon, Aymeric Alexandre Galan

Time-delay cosmography of lensed quasars has achieved 2.4% precision on the measurement of the Hubble constant, H0. As part of an ongoing effort to uncover and control systematic uncertainties, we investigate three potential sources: 1- stellar kinematics, ...

EDP SCIENCES S A2020

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

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

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

COSMOGRAIL XVII. Time delays for the quadruply imaged quasar PG 1115+080

Sun Hee Kim, Frédéric Courbin, Georges Meylan, Hung-Hsu Chan, Vivien François Bonvin, Malte Tewes, Martin Raoul Robert Millon, Karina Alexandra Rojas Olate, Eric Gérard Guy Paic

We present time-delay estimates for the quadruply imaged quasar PG 1115+080. Our results are based on almost daily observations for seven months at the ESO MPIA 2.2m telescope at La Silla Observatory, reaching a signal-to-noise ratio of about 1000 per quas ...

EDP SCIENCES S A2018

The GOGREEN Survey: Evidence of an Excess of Quiescent Disks in Clusters at 1.0

Pascale Jablonka, Hung-Hsu Chan

We present the results of the measured shapes of 832 galaxies in 11 galaxy clusters at 1.0 < z < 1.4 from the GOGREEN survey. We measure the axis ratio (q), the ratio of the minor to the major axis, of the cluster galaxies from near-infrared Hubble Space T ...

IOP Publishing Ltd2021

COSMOGRAIL XVIII. time delays of the quadruply lensed quasar WFI2033-4723

Sun Hee Kim, Frédéric Courbin, Georges Meylan, Hung-Hsu Chan, Vivien François Bonvin, Malte Tewes, Martin Raoul Robert Millon, Karina Alexandra Rojas Olate

We present new measurements of the time delays of WFI2033-4723. The data sets used in this work include 14 years of data taken at the 1.2 m Leonhard Euler Swiss telescope, 13 years of data from the SMARTS 1.3 m telescope at Las Campanas Observatory and a s ...

2019

Strongly lensed SNe Ia in the era of LSST: observing cadence for lens discoveries and time-delay measurements

Frédéric Courbin, Hung-Hsu Chan, Vivien François Bonvin

The upcoming Large Synoptic Survey Telescope (LSST) will detect many strongly lensed Type Ia supernovae (LSNe Ia) for time-delay cosmography. This will provide an independent and direct way for measuring the Hubble constant H0, which is necessary to addres ...

2019

Impact of the 3D source geometry on time-delay measurements of lensed type-Ia supernovae

Frédéric Courbin, Hung-Hsu Chan, Vivien François Bonvin, Martin Raoul Robert Millon, Elodie Marie Charlène Savary, Olga Tihhonova

It has recently been proposed that gravitationally lensed type-Ia supernovae can provide microlensing-free time-delay measurements provided that the measurement is taken during the achromatic expansion phase of the explosion and that color light curves are ...

EDP SCIENCES S A2019

The GOGREEN survey: post-infall environmental quenching fails to predict the observed age difference between quiescent field and cluster galaxies at z > 1

Pascale Jablonka, Hung-Hsu Chan

We study the star formation histories (SFHs) and mass-weighted ages of 331 UVJ-selected quiescent galaxies in 11 galaxy clusters and in the field at 1 < z < 1.5 from the Gemini Observations of Galaxies in Rich Early ENvironments (GOGREEN) survey. We determ ...

OXFORD UNIV PRESS2020

Lensed quasar search via time variability with the HSC transient survey

Hung-Hsu Chan

Gravitationally lensed quasars are useful for studying astrophysics and cosmology, and enlarging the sample size of lensed quasars is important for multiple studies. In this work, we develop a lens search algorithm for four-image (quad) lensed quasars base ...

2020

Measuring accretion disk sizes of lensed quasars with microlensing time delay in multi-band light curves

Frédéric Courbin, Hung-Hsu Chan, Vivien François Bonvin, Martin Raoul Robert Millon, Karina Alexandra Rojas Olate

Time-delay cosmography in strongly lensed quasars offers an independent way of measuring the Hubble constant, H-0. However, it has been proposed that the combination of microlensing and source-size effects, also known as microlensing time delay, can potent ...

EDP SCIENCES S A2021

Constraining the microlensing effect on time delays with a new time-delay prediction model in H-0 measurements

Frédéric Courbin, Hung-Hsu Chan, Vivien François Bonvin, Martin Raoul Robert Millon, Karina Alexandra Rojas Olate

Time-delay strong lensing provides a unique way to directly measure the Hubble constant (H-0). The precision of the H-0 measurement depends on the uncertainties in the time-delay measurements, the mass distribution of the main deflector(s), and the mass di ...

OXFORD UNIV PRESS2018

Models of the strongly lensed quasar DES J0408-5354

Frédéric Courbin, Georges Meylan, Eduardo Sanchez, Hung-Hsu Chan, Vivien François Bonvin, Cameron Alexander Campbell Lemon

We present detailed modelling of the recently discovered, quadruply lensed quasar J0408-5354, with the aim of interpreting its remarkable configuration: besides three quasar images (A, B, D) around the main deflector (G1), a fourth image (C) is significant ...

Oxford Univ Press2017

The impact of human expert visual inspection on the discovery of strong gravitational lenses

Frédéric Courbin, Hung-Hsu Chan, Martin Raoul Robert Millon, Benjamin Yvan Alexandre Clement, Karina Alexandra Rojas Olate, Elodie Marie Charlène Savary, Eric Gérard Guy Paic, Rémy Elie Joseph

We investigate the ability of human 'expert' classifiers to identify strong gravitational lens candidates in Dark Energy Survey like imaging. We recruited a total of 55 people that completed more than 25 per cent of the project. During the classification t ...

OXFORD UNIV PRESS2023