The Chandra high-energy transmission grating observation of an X-ray ionization cone in Markarian 3

We present a preliminary analysis of the first high-resolution X-ray spectrum of a Seyfert 2 galaxy, Markarian 3, obtained with the High-Energy Transmission Grating Spectrometer on board the Chandra X-Ray Observatory. The high-energy spectrum (lambda less than or similar to 4 Angstrom) is dominated by reflection of the active galactic nucleus continuum radiation in a cold, optically thick medium and contains bright Ka! fluorescent lines from iron and silicon as well as weak, blended lines from sulfur and magnesium. The soft X-ray emission (4 Angstrom less than or similar to lambda 23 Angstrom) is spatially extended along the [O III] ionization cone and shows discrete signatures of emission following recombination and photoexcitation produced in a warm photoionized region. The measured iron L line fluxes indicate that emission from collisionally ionized plasma is almost completely negligible and does not contribute significantly to the total energy budget of the X-ray emission. We find that significant fractions of the H- and He-like resonance lines, as well as the observed iron L lines, are produced through reemission from the warm absorbing medium observed in Seyfert 1 galaxies. Its X-ray spectral properties are qualitatively consistent with those of a typical Seyfert 1 galaxy viewed at a different orientation and provide further convincing evidence for the existence of an obscured Seyfert 1 nucleus in Mrk 3.