Observation of mulitply imaged quasars with the 4-m ILMT

TL;DR

This paper discusses the detection and measurement of multiply imaged quasars using the 4-m ILMT, highlighting preliminary observations and methods for accurate flux estimation to aid cosmological studies.

Contribution

It presents an estimation of the number of detectable multiply imaged quasars with the ILMT and introduces an adaptive PSF fitting method for precise flux measurements.

Findings

Estimated 15-50 multiply imaged quasars detectable with ILMT.

Successfully detected a quadruply imaged quasar in preliminary observations.

Proposed adaptive PSF fitting for accurate flux measurement.

Abstract

Gravitationally lensed quasars (GLQs) are known to potentially provide an independent way of determining the value of the Hubble-Lema\^{i}tre parameter $H_{0}$, to probe the dark matter content of lensing galaxies and to resolve tiny structures in distant active galactic nuclei. That is why multiply imaged quasars are one of the main drivers for a photometric monitoring with the 4-m International Liquid Mirror Telescope (ILMT). We would like to answer the following questions -- how many multiply imaged quasars should we be able to detect with the ILMT? And how to derive accurate magnitudes of the GLQ images? Our estimation of the possible number of multiply imaged quasars is $15$, although optimistic forecasts predict up to $50$ of them. We propose to use the adaptive PSF fitting method for accurate flux measurements of the lensed images. During preliminary observations in spring 2022 we were able to detect the quadruply imaged quasar - SDSS J1251+2935 in the $\it{i}$ and $\it{r}$ spectral bands.