Absorption and Reddening in the Seyfert Galaxy NGC 3227

We have obtained low-dispersion spectra of NGC 3227 with the Space Telescope Imaging Spectrograph (STIS) to study the intrinsic UV absorption and the reddening of the nucleus in this Seyfert 1 galaxy. The UV spectra show a wealth of absorption lines at the systemic redshift that span a wide range in ionization state (Mg I to N V). The equivalent widths of the lines are consistent with our earlier prediction that a " lukewarm absorber " (T e = 18,000 K at the ionized face) with a substantial column of gas (N H = 2 x 10 21 cm −2) is present and likely responsible for the reddening of the nucleus. The lukewarm absorber is also responsible for most of the absorption in the X-rays at energies less than 1 keV, although a more highly ionized " warm absorber " is needed to account for the O VII and O VIII ionization edges. In addition, we require a small column (N H = 5 x 10 19 cm −2) of cold gas to match the strengths of the neutral and singly-ionized lines in the UV spectra. NGC 3227 is the first Seyfert galaxy in which a strong link between the reddening and intrinsic UV absorption has been found. By comparing our STIS UV and optical spectra with those of the unred-dened Seyfert NGC 4151, we have determined a reddening curve for the nuclear continuum source in NGC 3227 over the 1150 – 10,200Å range. The reddening curve does not show a 2200Å bump, and is steeper in the UV than reddening curves derived for the Galaxy, LMC, and SMC, suggesting a preponderence of small dust grains near the nucleus.