The kinematics and physical conditions of the ionized gas in Markarian 509. I. Chandra high energy grating spectroscopy

We observed the Seyfert 1 galaxy Mrk 509 for similar to59 ks with the Chandra high-energy transmission gratings, simultaneously with HST/STIS and RXTE. Here we present a detailed analysis of the soft X-ray spectrum observed with Chandra. We measure strong absorption lines from He-like Ne and Mg and from H-like N, O, and Ne. Weaker absorption lines may also be present. The lines are unresolved except for Ne x Lyalpha (lambda12.134) and Ne IX 1s(2)-1s2p (lambda13.447), which appear to be marginally resolved. The profiles are blueshifted with respect to the systemic velocity of Mrk 509, indicating an outflow of similar to-200 km s(-1). There is also a hint that the profiles may have a velocity component near systemic. The soft X-ray spectrum can be described in remarkable detail with a simple, single-zone photoionized absorber having an equivalent neutral hydrogen column density of 2.06(-0.45)(+0.39) x 10(21) cm(-2) and an ionization parameter of logxi = 1.76(-0.14)(+0.13) (or log U = 0.27). Although the photoionized gas almost certainly is comprised of matter in more than one ionization state and may consist of several kinematic components, data with better spectral resolution and signal-to-noise ratio would be required to justify a more complex model. The UV data, on the other hand, have a velocity resolution of similar to10 km s(-1) and can easily detect eight kinematic components, covering roughly the same velocities as the X-ray absorption profiles. Even though the X-ray and UV absorbers share the same velocity space, the UV absorbers have a much smaller column density and ionization state. We show that models of the X-ray data do not predict significant UV absorption and are therefore consistent with the UV data. Finally, we do not detect any soft X-ray emission lines.