Issue |
A&A
Volume 699, July 2025
|
|
---|---|---|
Article Number | A299 | |
Number of page(s) | 14 | |
Section | Cosmology (including clusters of galaxies) | |
DOI | https://doi.org/10.1051/0004-6361/202555023 | |
Published online | 17 July 2025 |
Flashlights: Prospects for constraining the initial mass function around cosmic noon with caustic-crossing events
1
Department of Physics, Ben-Gurion University of the Negev, PO Box 653, Beer-Sheva 84105, Israel
2
Department of Physics, The University of Hong Kong, Pokfulam Road, Hong Kong
3
School of Physics and Astronomy, University of Minnesota, 116 Church Street SE, Minneapolis, MN 55455, USA
4
Donostia International Physics Center, DIPC, Basque Country, San Sebastián 20018, Spain
5
Department of Physics, University of Basque Country UPV/EHU, Bilbao, Spain
6
Ikerbasque, Basque Foundation for Science, Bilbao, Spain
7
Department of Physics, Oklahoma State University, 145 Physical Sciences Bldg, Stillwater, OK 74078, USA
8
IFCA, Instituto de Física de Cantabria (UC-CSIC), Av. de Los Castros s/n, 39005 Santander, Spain
9
Department of Astronomy, University of California, Berkeley, CA 94720-3411, USA
⋆ Corresponding author: ashishmeena766@gmail.com
Received:
3
April
2025
Accepted:
7
June
2025
The Flashlights program with the Hubble Space Telescope imaged the six Hubble Frontier Fields galaxy clusters in two epochs and detected twenty transients. These are primarily expected to be caustic-crossing events (CCEs) where bright stars in distant lensed galaxies, typically at redshift z≈1–3, get temporarily magnified close to cluster caustics. Since CCEs are generally biased toward more massive and luminous stars, they offer a unique route for probing the high end of the stellar mass function. We take advantage of the Flashlights event statistics to place preliminary constraints on the stellar initial mass function (IMF) around cosmic noon. The photometry (along with spectral information) of lensed arcs is used to infer their various stellar properties, and stellar synthesis models are used to evolve a recent stellar population in them. We estimate the microlens surface density near each arc and, together with existing lens models and simple formalism for CCEs, calculate the expected rate for a given IMF. We find that, on average, a Salpeter-like IMF (α = 2.35) underpredicts the number of observed CCEs by a factor of ∼0.7, and a top-heavy IMF (α = 1.00) overpredicts by a factor of ∼1.7, suggesting that the average IMF slope may lie somewhere in between. However, given the large uncertainties associated with estimating the stellar populations, these results are strongly model-dependent. Nevertheless, we introduce a useful framework for constraining the IMF using CCEs. Observations with James Webb Space Telescope are already yielding many more CCEs and will soon enable more stringent constraints on the IMF at a range of redshifts.
Key words: gravitational lensing: strong / gravitational lensing: weak / stars: luminosity function, mass function
© The Authors 2025
Open Access article, published by EDP Sciences, under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
This article is published in open access under the Subscribe to Open model. Subscribe to A&A to support open access publication.
Current usage metrics show cumulative count of Article Views (full-text article views including HTML views, PDF and ePub downloads, according to the available data) and Abstracts Views on Vision4Press platform.
Data correspond to usage on the plateform after 2015. The current usage metrics is available 48-96 hours after online publication and is updated daily on week days.
Initial download of the metrics may take a while.