VTechWorks staff will be away for the Thanksgiving holiday beginning at noon on Wednesday, November 27, through Friday, November 29. We will resume normal operations on Monday, December 2. Thank you for your patience.

Browsing by Author "Dunn, Jay P."

Now showing 1 - 6 of 6
  • Thumbnail Image
    BAL outflow contribution to AGN feedback: frequency of S IV outflows in the SDSS
    Dunn, Jay P.; Arav, Nahum; Aoki, Kentaro; Wilkins, Ashlee; Laughlin, Courtney; Edmonds, Douglas; Bautista, Manuel (IOP Publishing Ltd., 2012-05)
    We present a study of broad absorption line (BAL) quasar outflows that show S IV lambda 1063 and S IV* lambda 1073 troughs. The fractional abundances of S IV and C IV peak at similar value of the ionization parameter, implying that they arise from the same physical component of the outflow. Detection of the S IV* troughs will allow us to determine the distance to this gas with higher resolution and higher signal-to-noise spectra, therefore providing the distance and energetics of the ubiquitous C IV BAL outflows. In our bright sample of 156 SDSS quasars, 14% show C IV and 1.9% S IV troughs, which are consistent with a fainter magnitude sample with twice as many objects. One object in the fainter sample shows evidence of a broad S IV trough without any significant trough present from the excited state line, which implies that this outflow could be at a distance of several kpc. Given the fractions of C IV and S IV, we establish firm limits on the global covering factor on S IV that ranges from 2.8% to 21% (allowing for the k-correction). Comparison of the expected optical depth for these ions with their detected percentage suggests that these species arise from common outflows with a covering factor closer to the latter.
  • Thumbnail Image
    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.
  • Thumbnail Image
    Ionization-driven Fragmentation of Gas Outflows Responsible for FeLoBALs in Quasars
    Bautista, M. A.; Dunn, Jay P. (IOP PUBLISHING LTD, 2010-07)
    We show that time variations in the UV ionizing continuum of quasars, on scales of similar to 1 yr, affect the dynamic structure of the plasmas responsible for low-ionization broad absorption lines. Variations of the ionizing continuum produce non-equilibrium photoionization conditions over a significant fraction of the absorbing clouds and supersonically moving ionization fronts. When the flux drops, the contraction of the ionized region drives a supersonic cooling front toward the radiation source and a rarefaction wave in the opposite direction. The pressure imbalance is compensated by an increased speed of the cool gas relative to the front. When the flux recovers, the cool gas is re-ionized and re-heated by a supersonic ionization front traveling away from the radiation source and a forward shock is created. The re-heated clouds equilibrate to a temperature of similar to 10(4) K and are observed to have different radial velocities than the main cloud. Such fragmentation seems consistent with the multicomponent structure of troughs seen in some objects. The velocity differences measured among various components in the quasars QSO 2359-1241 and SDSS J0318-0600 can be reproduced by our model if strong magnetic fields (similar to 10 mG) are present within the clouds.
  • Thumbnail Image
    Physical conditions in the ultraviolet absorbers of IRAS F22456-5125
    Dunn, Jay P.; Crenshaw, D. M.; Kraemer, S. B.; Trippe, M. L. (IOP Publishing Ltd., 2010-04)
    We present the ultraviolet (UV) and X-ray spectra observed with the Far Ultraviolet Spectroscopic Explorer (FUSE) and the XMM-Newton satellite, respectively, of the low-z Seyfert 1 galaxy IRAS F22456-5125. This object shows absorption from five distinct, narrow kinematic components that span a significant range in velocity (similar to 0 to -700 km s(-1)) and ionization (Lyman series, C III, N III, and O VI). We also show that three of the five kinematic components in these lines appear to be saturated in Ly beta lambda 1026 and that all five components show evidence of saturation in the O vi doublet lines lambda lambda 1032, 1038. Further, all five components show evidence for partial covering due to the absorption seen in the O VI doublet. This object is peculiar because it shows no evidence for corresponding X-ray absorption to the UV absorption in the X-ray spectrum, which violates the 1: 1 correlation known for low-z active galactic nuclei (AGNs). We perform photoionization modeling of the UV absorption lines and predict that the O VII column density should be small, which would produce little to no absorption in agreement with the X-ray observation. We also examine the UV variability of the continuum flux for this object (an increase of a factor of 6). As the absorption components lack variability, we find a lower limit of similar to 20 kpc for the distance for the absorbers from the central AGN.
  • Thumbnail Image
    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.
  • Thumbnail Image
    Radial velocity offsets due to mass outflows and extinction in active galactic nuclei
    Crenshaw, D. M.; Schmitt, H. R.; Kraemer, S. B.; Mushotzky, R. F.; Dunn, Jay P. (IOP Publishing Ltd., 2010-01)
    We present a study of the radial velocity offsets between narrow emission lines and host galaxy lines (stellar absorption and Hi 21 cm emission) in Seyfert galaxies with observed redshifts less than 0.043. We find that 35% of the Seyferts in the sample show [O III] emission lines with blueshifts with respect to their host galaxies exceeding 50 km s(-1), whereas only 6% show redshifts this large, in qualitative agreement with most previous studies. We also find that a greater percentage of Seyfert 1 galaxies show blueshifts than Seyfert 2 galaxies. Using Hubble Spce Talescope/Space Telescope Imaging Spectrograph spatially resolved spectra of the Seyfert 2 galaxy NGC 1068 and the Seyfert 1 galaxy NGC 4151, we generate geometric models of their narrow-line regions (NLRs) and inner galactic disks, and show how these models can explain the blueshifted [O III] emission lines in collapsed STIS spectra of these two Seyferts. We conclude that the combination of mass outflow of ionized gas in the NLR and extinction by dust in the inner disk (primarily in the form of dust spirals) is primarily responsible for the velocity offsets in Seyfert galaxies. More exotic explanations are not needed. We discuss the implications of this result for the velocity offsets found in higher redshift active galactic nuclei.