Mrk 509 is a Seyfert galaxy, which harbors a supermassive black hole at its center. Because of its unique X-ray brightness, Mrk 509 is intensively observed using ground and space based telescopes. This multiwavelength observation allowed Kaastra et al. (2011) to obtain one of the best broad band spectral energy distribution (SED) ever constructed for any active galactic nuclei (AGN). The radiation from central nucleus is absorbed by the warm ionized gas, so called warm absorber (WA) located in the line of sight at distances of 0.01 -100 pc from the BH. WA is visible due to absorption lines presented in high resolution spectra obtained with XMM-Newton, Chandra, and Suzaku.
In this context, the strength of the absorption is described in terms of absorption measure distribution (AMD). AMD measures the distribution of the absorbing column over the range of the distances (and hence the ionization parameters) from the central source. Using the broad band SED of Mrk 509, Tek P. Adhikari, from the Copernicus Astronomical Center, and collaborators has obtained the theoretical AMD in Mrk 509 which matches with the observational AMD obtained by Detmers et al. (2011) on the basis of 600 ks XMM-Newton data. Using the photoionization simulation, Tek P. Adhikari and collaborators showed that the observed discontinuities in the AMD can be reproduced assuming that WA is a zone under a total pressure (radiation pressure + gas pressure) equilibrium. This result is obtained for the first time explaining the origin of two dips seen in AMD of Mrk 509. Those dips reflect regions where the absorber is thermally unstable due to illumination.
The figure shows the theoretical & observed AMD for Mrk 509, where observations are given by black histogram, and our model by red triangles. The article „Absorption Measure Distribution in Mrk 509” by Adhikari T.P., Różańska A., Sobolewska M., Czerny B. is accepted for publication in the Astrophysical Journal.
