Vol 18, No 2

R-band host galaxy contamination of TeV γ-ray blazar Mrk 501: effects of aperture size and seeing

Hai-Cheng Feng, Hong-Tao Liu, Ying-He Zhao, Jin-Ming Bai, Fang Wang, Xu-Liang Fan


Abstract We simulated the R-band contribution of the host galaxy of TeV γ-ray BL Lac object Mrk 501 in different aperture sizes and seeing conditions. An intensive set of observations was acquired with the 1.02 m optical telescope, managed by Yunnan Observatories, from 2010 May 15 to 18. Based on the host subtraction data usually used in the literature, 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 microvariability, thus giving rise to difficulty in detecting the intrinsic microvariability. Both aperture size and seeing condition influence the flux measurements, but the aperture size impacts the result more significantly. Based on the parameters of an elliptical galaxy provided in the literature, we simulated the host contributions of Mrk 501 in 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 microvariability. The pure nuclear flux is ∼8.0 mJy in the R band, i.e., the AGN has a magnitude of R ∼ 13.96 mag.


Keywords galaxies: active — BL Lacertae objects: individual (Mrk 501) — techniques: photometric — methods: data analysis

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