The James Webb Space Telescope is revolutionizing the field of strong gravitational lensing in galaxy clusters, allowing us to go further and fainter in our search for multiply imaged galaxies. I will present the recent results of the Canadian NIRISS Unbiased Cluster Survey (CANUCS), targeting 5 massive clusters with 3 instruments onboard JWST. With the example of MACS 0416 - the cluster with...
In this talk, I will discuss how gravitational weak lensing data can be leveraged to calibrate the masses of galaxy clusters. The South Pole Telescope (SPT) survey detects clusters via the thermal Sunyaev-Zel'dovich (SZ) effect, but this method does not yield direct mass measurements. Gravitational weak lensing provides a complementary approach, enabling accurate mass estimations that are...
CMB observations show that early density fluctuations were nearly Gaussian. The gravitational evolution of matter formed large structures, and nonlinear evolution introduced non-Gaussianity, making it challenging to analyze. In this project, we employ the scattering transform, a powerful statistical tool that shares ideas with convolutional neural networks (CNNs) but requires no training or...
Higher-order WL statistics can capture the non-Gaussian nature of the Cosmic Web and exploit that to offer stricter constraints on Cosmological/MG parameters. In this talk I will start by elaborating on the significance and advantages of looking into these higher-order statistics.
There are certain known systematic errors (like galaxy Intrinsic Alignment) that exist in WL data, which need...
Maximising the information that can be extracted from weak lensing measurements is a key goal for LSST and Euclid. This is typically achieved through statistics that are complementary to the cosmic shear two-point correlation function.
In this talk I will present the development of two such complementary statistics.
The first is weak lensing peaks. Typically, only the peak abundance is...
Cosmic voids are vast underdense regions in the universe that offer unique insights into dark energy and the large-scale structure of the cosmos. This talk presents a novel method for identifying voids in weak lensing convergence maps using a 2D watershed algorithm. By analyzing data from the CosmoGridV1 simulation and the Dark Energy Survey (DES), we demonstrate the algorithm's capability to...
The International LOFAR Telescope (ILT) is currently observing the entire northern sky at a resolution of 0.3 arcsec as part of the LOFAR Two-metre Sky Survey (LoTSS). Its large survey area and high resolution combined with steep number counts towards low frequencies make the ILT well suited for finding galaxy-scale lenses, but the inherent complexity of radio source morphologies make the...
The Euclid mission is expected to discover approximately 150,000 strong gravitational lenses, greatly expanding the known lens population (Collett et al. 2015). Low-redshift early-type galaxies (ETGs) offer a unique opportunity to probe the stellar initial mass function (IMF) as their Einstein radii, typically smaller than the effective radius, enable mass measurements more sensitive to...
We present a mass measurement for the secondary lens along the line of sight (LoS) in the multi-plane strong lens modeling of the group-scale lens CASSOWARY 31 (CSWA 31). The secondary lens at redshift z = 1.49 is a spiral galaxy well aligned along the LoS with the main lens at z = 0.683. Using the MUSE integral-field spectroscopy of this spiral galaxy, we measure its rotation velocities and...
Strong gravitational lensing is an astrophysical effect that happens when the gravitational field of a massive object bends light from a background source, creating multiple, often distorted, images of the same distant object. Accurate modelling of the mass distribution of strong gravitational lenses is crucial in order to use them as astrophysical and cosmological probes, such as for...
Strong gravitational lensing has proven to be a promising tool for detecting low-mass haloes through observing perturbations in the lensing potential, therefore allowing the testing of different dark matter (DM) models by comparing the theoretical predictions for the abundance of such haloes in different DM models with observations. However, to robustly constrain the mass function of low-mass...
We present a simulation-based inference analysis framework for a higher-order weak lensing observable called the integrated 3-point correlation function. For this we have created a forward model based on N-body simulations. This forward model can create realistic shear maps including survey masks, realistic shape noise, and relevant systematic effects. Furthermore, I present a Python package...
We present a foundation model for strong lensing based on diffusion transformers, which can solve a wide range of different simulation-based inference problems via representation learning. Image-like data such as observations are split into smaller patches, which together with their positions are embedded as tokens. Similarly, parametric models are also encoded via tokens. A strong lens system...
In the past, researchers have relied on single-resolution images from individual telescopes to detect gravitational lenses. We propose a search for galaxy-galaxy lenses that, for the first time, combines high-resolution single-band images (in our case Hubble Space Telescope, HST) with low-resolution multi-band images (in our case Legacy survey, LS) using machine learning. To compensate for the...
Strongly lensed supernovae (SNe) hold great promise for measuring the expansion rate of the Universe and studying SN progenitors and environments. However, finding lensed SNe resembles searching for the needle in a haystack, and following them up is very demanding and costly due to their faintness. For the best possible use of available resources, it is thus essential that we can securely...
With the upcoming start of Rubin Observatory Legacy Survey of Space and Time
(LSST), we expect to detect hundreds to thousands of strongly lensed supernovae,
which can be used for time-delay cosmography.
As part of the HOLISMOKES program, we focus on developing methods to measure time delays of strongly lensed type II supernovae (SNe II) to determine the Hubble Constant.
In my talk, I...
In the coming years, surveys such as Rubin Observatory Legacy Survey of Space and Time (LSST) are expected to increase the number of observed tidal disruption events (TDEs) substantially. This analysis is a followup to Szekerczes, et al. (2024). We similarly employ Monte Carlo integration to calculate the TDE rate as a function of limiting magnitude. We investigate multiple black hole mass...
