Absorption and reddening in the Seyfert galaxy NGC 3227

We have obtained low-dispersion spectra of NGC 3227 with the Space Telescop e 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 we alth 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 con sistent with our earlier prediction that a "lukewarm absorber" (T-e = 18,00 0 K at the ionized face) with a substantial column of gas (N-H = 2x 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 th e 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. I n addition, we require a small column (N-H = 5x10(19) cm(-2)) of cold gas t o match the strengths of the neutral and singly ionized lines in the UV spe ctra. NGC 3227 is the first Seyfert galaxy in which a strong link between t he reddening and intrinsic UV absorption has been found. By comparing our S TIS UV and optical spectra with those of the unreddened Seyfert galaxy NGC 4151, we have determined a reddening curve for the nuclear continuum source in NGC 3227 over the 1150-10200 Angstrom range. The reddening curve does n ot show a 2200 Angstrom bump and is steeper in the UV than reddening curves derived for the Galaxy, LMC, and SMC, suggesting a preponderance of small dust grains near the nucleus.