Browsing by Author "Benn, C."

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    BAL phosphorus abundance and evidence for immense ionic column densities in quasar outflows: vlt/x-shooter observations of quasar SDSS J1512+1119
    Borguet, Benoit C. J.; Edmonds, Douglas; Arav, Nahum; Benn, C.; Chamberlain, Carter (IOP Publishing Ltd., 2012-10)
    We present spectroscopic analysis of the broad absorption line (BAL) outflow in quasar SDSS J1512+1119. In particular, we focus our attention on a kinematic component in which we identify P V and S IV/S IV* absorption troughs. The shape of the unblended phosphorus doublet troughs and the three S IV/S IV* troughs allow us to obtain reliable column density measurements for these two ions. Photoionization modeling using these column densities and those of He I* constrain the abundance of phosphorus to the range of 0.5-4 times the solar value. The total column density, ionization parameter, and metallicity inferred from the P V and S IV column densities lead to large optical depth values for the common transition observed in BAL outflows. We show that the true C IV optical depth is similar to 1000 times greater in the core of the absorption profile than the value deduced from its apparent optical depth.
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    Galactic-scale absorption outflow in the low-luminosity quasar IRAS F04250-5718: Hubble Space Telescope/Cosmic Origins Spectrograph observations
    Edmonds, Douglas; Borguet, Benoit; Arav, Nahum; Dunn, Jay P.; Penton, S.; Kriss, G. A.; Korista, K. T.; Costantini, E.; Steenbrugge, K. C.; Gonzalez-Serrano, J. I.; Aoki, K.; Bautista, M. A.; Behar, E.; Benn, C.; Crenshaw, D. M.; Everett, J.; Gabel, J.; Kaastra, J.; Moe, M.; Scott, J. (IOP Publishing Ltd., 2011-09)
    We present absorption line analysis of the outflow in the quasar IRAS F04250-5718. Far-ultraviolet data from the Cosmic Origins Spectrograph on board the Hubble Space Telescope reveal intrinsic narrow absorption lines from high ionization ions (e. g., C IV, N V, and O VI) as well as low ionization ions (e. g., C II and Si III). We identify three kinematic components with central velocities ranging from similar to-50 to similar to-230 km s(-1). Velocity-dependent, non-black saturation is evident from the line profiles of the high ionization ions. From the non-detection of absorption from a metastable level of C II, we are able to determine that the electron number density in the main component of the outflow is less than or similar to 30 cm(-3). Photoionization analysis yields an ionization parameter log U-H similar to -1.6 +/- 0.2, which accounts for changes in the metallicity of the outflow and the shape of the incident spectrum. We also consider solutions with two ionization parameters. If the ionization structure of the outflow is due to photoionization by the active galactic nucleus, we determine that the distance to this component from the central source is greater than or similar to 3 kpc. Due to the large distance determined for the main kinematic component, we discuss the possibility that this outflow is part of a galactic wind.
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    Major contributor to AGN feedback: VLT X-shooter observations of S iv BALQSO outflows
    Borguet, Benoit C. J.; Arav, Nahum; Edmonds, Douglas; Chamberlain, Carter; Benn, C. (IOP Publishing Ltd., 2013-01)
    We present the most energetic BALQSO outflow measured to date, with a kinetic luminosity of at least 1046 erg s(-1), which is 5% of the bolometric luminosity of this high Eddington ratio quasar. The associated mass-flow rate is 400 solar masses per year. Such kinetic luminosity and mass-flow rate should provide strong active galactic nucleus feedback effects. The outflow is located at about 300 pc from the quasar and has a velocity of roughly 8000 km s-1. Our distance and energetic measurements are based in large part on the identification and measurement of S iv and S IV* broad absorption lines (BALs). The use of this high-ionization species allows us to generalize the result to the majority of high-ionization BALQSOs that are identified by their C iv absorption. We also report the energetics of two other outflows seen in another object using the same technique. The distances of all three outflows from the central source (100-2000 pc) suggest that we observe BAL troughs much farther away from the central source than the assumed acceleration region of these outflows (0.01-0.1 pc).
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    Measuring column densities in quasar outflows: VLT observations of QSO 2359-1241
    Arav, Nahum; Moe, Maxwell; Costantini, E.; Korista, K. T.; Benn, C.; Ellison, S. (IOP Publishing Ltd., 2008-07)
    We present high-resolution spectroscopic VLT observations of the outflow seen in QSO 2359-1241. These data contain absorption troughs from five resonance Fe II lines with a resolution of similar to 7 km s(-1) and a signal-to-noise ratio per resolution element of order 100. We use this unprecedented high-quality data set to investigate the physical distribution of the material in front of the source and by that to determine the column densities of the absorbed troughs. We find that the apparent optical depth model gives a very poor fit to the data and greatly underestimates the column density measurements. Power-law distributions and partial covering models give much better fits, with some advantage to power-law models, while both models yield similar column density estimates. The better fit of the power-law model solves a long-standing problem plaguing the partial covering model when applied to large distance scale outflow: how to obtain a velocity-dependent covering factor for an outflow situated at distances thousands of time greater than the size of the AGN emission source. This problem does not affect power-law models. Therefore, based on the better fit and plausibility of the physical model, we conclude that in QSO 2359-1241, the outflow covers the full extent of the emission source but in a nonhomogeneous way.
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    Physical Conditions in Quasar Outflows: Very Large Telescope Observations of QSO 2359-1241
    Korista, K. T.; Bautista, M. A.; Arav, Nahum; Moe, Maxwell; Costantini, E.; Benn, C. (IOP PUBLISHING LTD, 2008-11)
    We analyze the physical conditions of the outflow seen in QSO 2359-1241 (NVSS J235953-124148), based on high-resolution spectroscopic VLT observations. This object was previously studied using Keck HIRES data. The main improvement over the HIRES results is our ability to accurately determine the number density of the outflow. For the major absorption component, the populations from five different Fe II excited levels yield a gas density n(H) = 10(4.4) cm(-3) with less than 20% scatter. We find that the Fe II absorption arises from a region with roughly constant conditions and temperature greater than 9000 K, before the ionization front where temperature and electron density drop. Further, we model the observed spectra and investigate the effects of varying gas metallicities and the spectral energy distribution of the incident ionizing radiation field. The accurately measured column densities allow us to determine the ionization parameter (log U-H approximate to -2.4) and total column density of the outflow [log N-H(cm(-2)) approximate to 20.6]. Combined with the number density finding, these are stepping stones toward determining the mass flux and kinetic luminosity of the outflow, and therefore its importance to AGN feedback processes.
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    The quasar outflow contribution to AGN feedback: VLT measurements of SDSS J0318-0600
    Dunn, Jay P.; Bautista, M. A.; Arav, Nahum; Moe, Maxwell; Korista, K. T.; Costantini, E.; Benn, C.; Ellison, S.; Edmonds, Douglas (IOP Publishing Ltd., 2010-02)
    We present high spectral resolution Very Large Telescope observations of the broad absorption line quasar SDSS J0318-0600. This high-quality data set allows us to extract accurate ionic column densities and determine an electron number density of n(e) = 10(3.3 +/- 0.2) cm(-3) for the main outflow absorption component. The heavily reddened spectrum of SDSS J0318-0600 requires purely silicate dust with a reddening curve characteristic of predominately large grains, from which we estimate the bolometric luminosity. We carry out photoionization modeling to determine the total column density, ionization parameter, and distance of the gas and find that the photoionization models suggest abundances greater than solar. Due to the uncertainty in the location of the dust extinction, we arrive at two viable distances for the main ouflow component from the central source, 6 and 17 kpc, where we consider the 6 kpc location as somewhat more physically plausible. Assuming the canonical global covering of 20% for the outflow and a distance of 6 kpc, our analysis yields a mass flux of 120 M(circle dot) yr(-1) and a kinetic luminosity that is similar to 0.1% of the bolometric luminosity of the object. Should the dust be part of the outflow, then these values are similar to 4x larger. The large mass flux and kinetic luminosity make this outflow a significant contributor to active galactic nucleus feedback processes.