Spectro-photometric variability of quasars caused by lensing of diffuse massive substructure: Consequences on flux anomaly and precise astrometric measurements

TL;DR

This paper explores how small mass diffuse structures can cause spectro-photometric variability and flux anomalies in lensed quasars, affecting astrometric measurements and potentially detectable by space missions.

Contribution

It demonstrates that small mass diffuse structures can induce observable flux anomalies and astrometric shifts in quasars, expanding understanding of lensing effects beyond macrolensing.

Findings

Small mass diffuse structures can cause flux anomalies in lensed quasars.

Lensing by such structures can produce milliarcsecond shifts in quasar photocenters.

Detectable variability and image splitting may occur on short timescales for low-redshift deflectors.

Abstract

We investigate the spectro-photometric variability of quasars due to lensing of small mass substructure (from several tens to several hundreds solar masses). The aim of this paper is to explore the milli/microlensing influence on the flux anomaly observed between images of a lensed quasar in different spectral bands and possible influence of small mass structure lensing of non-macrolensed quasars.We find that spectro-photometric variability may be also caused by lensing of small mass diffuse structure and can produce the flux anomaly which is sometimes seen in different images of a lensed quasar. Additionally, we found that the lensing by small mass diffuse structure may produce significant changes in photo-center position of a quasar, and sometimes can split or deviate images of one source that can be detected as separate from the scale from 0.1 to several milliarcseconds. This can be measured ith Gaialike space astrometric missions. We point out a special case where a low redshifted deflector zd = 0.01 is lensing a high redshifted source, for which the variability in the flux and photocenter (several milliarcseconds) may be detected on a relatively short time scale.