Observing programs comprising multiple scientific objectives will enhance the productivity of NASAs next UV/Visible mission. Studying active galactic nuclei (AGN) is intrinsically important for understanding how black holes accrete matter, grow throu
gh cosmic time, and influence their host galaxies. At the same time, the bright UV continuum of AGN serves as an ideal background light source for studying foreground gas in the intergalactic medium (IGM), the circumgalactic medium (CGM) of individual galaxies, and the interstellar medium (ISM) and halo of the Milky Way. A well chosen sample of AGN can serve as the observational backbone for multiple spectroscopic investigations including quantitative measurements of outflows from AGN, the structure of their accretion disks, and the mass of the central black hole.
We present a detailed analysis of the Astrophysical Research Consortium 3.5 m telescope spectrum of QSO SDSS J0838+2955. The object shows three broad absorption line (BAL) systems at 22,000, 13,000, and 4900 km s^-1 blueshifted from the systemic reds
hift of z=2.043. Of particular interest is the lowest velocity system that displays absorption from low-ionization species such as Mg II, Al II, Si II, Si II*, Fe II and Fe II*. Accurate column densities were measured for all transitions in this lowest velocity BAL using an inhomogeneous absorber model. The ratio of column densities of Si II* and Fe II* with respect to their ground states gave an electron number density of log n_e (cm^-3) = 3.75 +/- 0.22 for the outflow. Photoionization modeling with careful regards to chemical abundances and the incident spectral energy distribution predicts an ionization parameter of log U_H = -1.93 +/- 0.21 and a hydrogen column density of log N_H (cm^-2) = 20.80 +/- 0.28. This places the outflow at 3.3+1.5-1.0 kpc from the central AGN. Assuming that the fraction of solid angle subtended by the outflow is 0.2, these values yield a kinetic luminosity of (4.5+3.1-1.8) x 10^45 erg s^-1, which is (1.4+1.1-0.6)% the bolometric luminosity of the QSO itself. Such large kinetic luminosity suggests that QSO outflows are a major contributor to AGN feedback mechanisms.
We examine the variability in the intrinsic absorption in the Seyfert 1 galaxy Mrk 279 using three epochs of observations from the Far Ultraviolet Spectroscopic Explorer (FUSE) and two epochs of observations with the Space Telescope Imaging Spectrogr
aph on the Hubble Space Telescope. Rather than finding simple photoionization responses of the absorbing gas to changes in the underlying continuum, the observed changes in the absorption profiles can be understood more clearly if the effective covering fraction of the gas in all emission components, continuum and broad and intermediate velocity width emission lines, is accounted for. While we do not uniquely solve for all of these separate covering fractions and the ionic column densities using the spectral data, we examine the parameter space using previously well-constrained solutions for continuum and single emission component covering fractions. Assuming full coverage of the continuum, we find that of the two velocity components of the Mrk 279 absorption most likely associated with its outflow, one likely has zero coverage of the intermediate line region while the other does not. For each component, however, the broad line region is more fully covered than the intermediate line region. Changes in the O VI column densities are unconstrained due to saturation, but we show that small changes in the nonsaturated C IV and N V column densities are consistent with the outflow gas having zero or partial covering of the intermediate line region and an ionization parameter changing from ~0.01 to ~0.1 from 2002 to 2003 as the UV continuum flux increased by a factor of ~8. The absence of a change in the C III absorbing column density is attributed to this species arising outside the Mrk 279 outflow.
