Chandra Observations of Mrk 273: Unveiling the Central Agn and the Extended Hot Gas Halo

We report X-ray observations of the field containing the ultraluminous IRAS galaxy Mrk 273. The data were obtained using the ACIS-S3 instrument on board Chandra. The high resolution X-ray image, for the first time, reveals a compact hard X-ray nucleus in Mrk 273. Its position is coincident with the northern nucleus identified in the optical, infrared, radio and in molecular CO maps. Its X-ray energy distribution is well described by a heavily obscured AGN spectrum with an absorbed power-law plus a narrow FeKα emission line at 6.4 keV. The neutral hydrogen column density is about 4 × 10 cm, implying an absorption-corrected X-ray luminosity (0.1–10 keV) for the nucleus of LX ≈ 6.5 × 10 43 erg s for H0 = 50 km s Mpc. The X-ray properties therefore firmly establishes the northern nucleus of Mrk 273 as a Seyfert 2 active galactic nucleus. There are also bright soft X-ray clumps and diffuse soft X-ray emissions surrounding the central hard X-ray nucleus within the 10 of the nuclear region. Its spectrum can be fitted by a MEKAL thermal model with temperature of about 0.8 keV and high metallicity (Z ∼ 1.5Z⊙) plus emission lines from α elements and ions. We find that a soft X-ray clump, about 4 (projected separation of about 4 kpc) southwest of the northern hard X-ray nucleus, is coincident with a nebula with strong [O iii]λ5007 emissions. Further outside the central region, the Chandra observations reveal a very extended hot halo in Dept. of Physics, Tianjin Normal University, 300074 Tianjin, China National Astronomical Observatories, Chinese Academy of Sciences, A20 Datun Road, 100012 Beijing, China Univ. of Manchester, Jodrell Bank Observatory, Macclesfield, Cheshire SK11 9DL, UK Max-Planck-Institute für Extraterrestrische Physik, Postfach 1312 D-85741 Garching, Germany Dept. of Physics, Graduate School, Chinese Academy of Sciences, 100039 Beijing, China