A TWO-PHASE LOW-VELOCITY OUTFLOW IN THE SEYFERT 1 GALAXY Ark 564

The Seyfert 1 galaxy Ark 564 was observed with Chandra high-energy transmission gratings for 250 ks. We present the high-resolution X-ray spectrum that shows several associated absorption lines. The photoionization model requires two warm absorbers (WAs) with two different ionization states (log U = 0.39 ± 0.03 and log U = −0.99 ± 0.13), both with moderate outflow velocities (∼100 km s−1) and relatively low line of sight column densities (log NH = 20.94 and 20.11 cm−2). The high-ionization phase produces absorption lines of O vii, O viii, Ne ix, Ne x, Mg xi, Fe xvii, and Fe xviii, while the low-ionization phase produces lines at lower energies (O viand O vii). The pressure–temperature equilibrium curve for the Ark 564 absorber does not have the typical “S” shape, even if the metallicity is super-solar; as a result, the two WA phases do not appear to be in pressure balance. This suggests that the continuum incident on the absorbing gas is perhaps different from the observed continuum. We also estimated the mass outflow rate and the associated kinetic energy and find it to be at most 0.009% of the bolometric luminosity of Ark 564. Thus, it is highly unlikely that these outflows provide significant feedback required by the galaxy formation models.