Talks and presentations

See a map of all the places I've given a talk!

Conference Talks

4MOST Cosmology Redshift Survey: Quasar Target Selection, and Science Programme Validation Results

July 03, 2026

Conference talk, European Astronomical Society Annual Meeting, Lausanne, Switzerland

The 4MOST Cosmology Redshift Survey (CRS) will provide the redshift measurement of 1.5 million quasars and Lyα-QSO at redshifts 0.9 2. We present the status of the CRS quasar target selection and its validation using CRS Science Programme Validation (SPV) observations. The baseline selection follows the optical–infrared colour approach introduced by Eltvedt et al. (2023). Within SPV, we test whether modest, physically motivated adjustments can increase the QSO surface density while maintaining tight control over contamination. This includes exploring expanded colour–magnitude boundaries and auxiliary features, and quantifying the resulting completeness–contamination trade-off. The SPV spectra provide a direct assessment of redshift success rate and the dominant contamination pathways, enabling purity measurements for both the baseline and expanded selections and an evaluation of their suitability for cosmological applications. In overlapping regions, we also benchmark performance against the DESI QSO target selection based on a random-forest classifier, using matched samples to compare redshift yield and contamination against an established machine-learning approach. We additionally assess how masking affects contamination and usable area for the CRS QSO selection.

4MOST Cosmology Redshift Survey: Survey Design, Clustering Tests, and Early Science Validation Results

July 03, 2026

Conference talk, European Astronomical Society Annual Meeting, Lausanne, Switzerland

The upcoming 4MOST Cosmology Redshift Survey (CRS) is designed to obtain nearly 5.4 million redshifts over ~5700deg^2 of the southern sky. CRS aims to deliver precise measurements of the baryon acoustic oscillation (BAO) scale and redshift-space distortions (RSD), providing an independent test of dark energy in light of recent indications of evolving dark energy. CRS will also complement major southern datasets, including Rubin Observatory LSST, Euclid, and CMB measurements, through joint analyses and cross-correlations. A central requirement for per cent-level cosmology is that the spectroscopic samples are selected in a way that is both efficient and spatially uniform. Variations in imaging depth, extinction, masking, and stellar contamination can imprint angular structure that mimics true clustering, biasing cosmological fits and distorting environmental measures. We therefore use two-point statistics as a validation tool, turning clustering into a set of quantitative null tests for target selection, masking strategy, and residual contamination. In this talk, we will present the CRS target selection and validation tests for its main tracers, focusing on bright galaxies, luminous red galaxies, and quasars. We will first summarise the sample characterisation and cosmological performance forecasts presented by Verdier et al. (2025), based on selections from DESI Legacy Surveys DR10.1 imaging. We will then present the clustering-based validation from Bandi et al. (2026). We measure the angular correlation function w(θ) for magnitude- and colour-selected subsamples, test sensitivity to photometric systematics, and quantify the impact of masking and veto choices, including Legacy Surveys quality flags and WISE-related artefact regions. We compare measurements between Galactic caps as a stringent uniformity test, perform Limber-scaling consistency checks across bright-galaxy magnitude slices, and infer redshift distributions via cross-correlation with DESI spectroscopy. These tests translate into concrete mitigation strategies and a systematics budget for early CRS cosmology. Finally, we will report results from the 4MOST Science Programme Validation (SPV) campaign from February to April 2026. We will assess instrument and pipeline performance, spectral quality, and redshift success rates, and present on-sky tests of CRS target selection using early spectra, including empirical contamination measurements and completeness as a function of masking and observing conditions. We will conclude by showing the first clustering measurements from 4MOST SPV spectra and their implications for CRS analyses ahead of routine survey operations.

Public and Outreach Talks

Mapping the Universe: The Past, Present, and Future of Sky Surveys

August 28, 2025

Outreach talk, Astronomy Festival, Herstmonceux Observatory, Herstmonceux, East Sussex, UK

A public talk on how sky surveys evolved from early star catalogues to modern projects such as Gaia, 4MOST, DESI, LSST, and Euclid, and how these surveys help answer questions about galaxy growth, dark energy, and the cosmic web.

The Earth’s favourite New year, Nowruz

April 03, 2024

Outreach talk, Lewes Astronomical Society, Lewes, UK

An outreach talk on Nowruz (the Persian New Year) and the astronomy of calendars, explaining how lunar, solar, and lunisolar systems keep time and why the Persian calendar is tied to the spring equinox. It also covered the history and structure of the Iranian calendar and the cultural traditions of Nowruz, from its origins to modern celebrations.

Tatooine Orbits

May 04, 2023

Outreach talk, Brighton Astro, Brighton, UK

The planet Tatooine in Star Wars orbits has two suns. We want to see if it’s possible for Tattoine to exist in the real world by simulating its orbit.

Collaboration Meeting Talks

CRS BG and LRG target selection and angular clustering

February 24, 2025

Collaboration meeting talk, 4MOST Science Team Meeting, University of Naples Federico II, Naples, Italy

The Cosmology Redshift Survey (4MOST-CRS) will enable precision cosmological measurements using spectroscopic clustering of galaxies and quasars over 0.1 < z < 2.5 across >7000 deg^2. This talk presented the CRS Bright Galaxy and Luminous Red Galaxy target selections and angular clustering tests used to assess catalogue quality and uniformity.

Angular two-point correlation function of Euclid Early Data

January 22, 2025

Collaboration meeting talk, Euclid Galaxy Clustering Meeting, Max Planck Institute for Extraterrestrial Physics, Garching, Germany

Presented measurements of the angular two-point correlation function using Euclid Early Data, focusing on methodology, early catalogue validation, and key systematic checks relevant to clustering analyses.

Behnood Bandi