$R$-band host galaxy contamination of TeV $\gamma$-ray blazar Mrk 501: effects of the aperture size and seeing

TL;DR

This study simulates how host galaxy contamination affects R-band flux measurements of Mrk 501 under various aperture sizes and seeing conditions, revealing that proper subtraction is crucial for detecting intrinsic micro variability.

Contribution

It introduces a simulation method to quantify host galaxy contamination effects on flux measurements, improving the detection of intrinsic micro variability in blazar observations.

Findings

Aperture size impacts flux measurements more than seeing conditions.

Host subtraction weakens seeing-brightness correlations.

Intrinsic micro variability can be better identified after correction.

Abstract

We simulated the $R$-band contribution of the host galaxy of TeV $\gamma$-ray BL Lac object Mrk 501 in different aperture sizes and seeing conditions . The intensive observations were run with the 1.02 m optical telescope at Yunnan Observatories from 2010 May 15 to 18. Based on the host subtraction data presented in Nilsson et al. (2007), the subtraction of host galaxy contamination results in significant seeing-brightness correlations. These correlations would lead to illusive large amplitude variations at short timescales, which will mask the intrinsic micro variability, thus gives rise to difficulty in detecting the intrinsic micro variability. Both aperture size and seeing condition influence the flux measurements, but aperture size impact the result more significantly. Based on the parameters of elliptical galaxy provided in Nilsson et al. (1999), we simulated the host contributions of Mrk 501 in the different aperture sizes and seeing conditions. Our simulation data of the host galaxy obviously weaken these significant seeing-brightness correlations for the host-subtracted brightness of Mrk 501, and can help us discover the intrinsic short timescale micro variability. The pure nuclear flux is $\sim$ 8.0 $\rm{mJy}$ in \emph{R} band, i.e., AGN has a magnitude of $R\sim13^{m}_{\cdot}96$.