Dust-to-gas ratio in a complete sample of type-1 AGN

Resumen del póster presentado al XIII Scientific Meeting of the Spanish Astronomical Society, celebrado en la Universidad de Salamanca del 16 al 20 de julio de 2018.
According to the Unified Model of Active Galactic Nuclei (AGN), unobscured AGN based on its optical spectrum (detection of rest-frame UV-optical broad emission lines, type-1 AGN) should appear as X-ray unabsorbed AGN. However, there is an important fraction (10-30%) of AGN whose optical and X-ray classifications do not match, and the origin of the discrepancy is not clear. To provide insight into this topic, we have conducted a statistical analysis of the optical obscuration and X-ray absorption properties of the optically type1 AGN from the Bright Ultra-hard XMM-Newton Survey (BUXS) with L2−10keV >1042 erg s−1 and z=0.05-1. We have high-quality spectra from XMM-Newton and either SDSS spectra or proprietary observations for the selected sample. In order to provide the most complete sample as possible, we have conducted a detailed analysis of the emission lines to provide a reliable classification of the AGNs. We derive the X-ray absorption by fitting their XMM-Newton spectra and the optical extinction using UV/optical spectral continuum fits. As BUXS is a flux limited X-ray selected sample at hard energies (f4.510keV ≤6×10−14 ergs−1cm−2), it is complete for NH column densities up to the Compton-thick limit (∼1024cm−2). Our preliminary results show that most type-1 AGN in our sample show consistent optical and X-ray classification, but there is a large fraction ( 20%) of objects with large NH column densities (NH >4×1021 cm−2).