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Browsing by Author "Kraemer, S. B."

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    Mass Outflow in the Seyfert 1 Galaxy NGC 5548
    Crenshaw, D. M.; Kraemer, S. B.; Schmitt, H. R.; Kaastra, J. S.; Arav, Nahum; Gabel, J. R.; Korista, K. T. (IOP PUBLISHING LTD, 2009-06)
    We present a study of the intrinsic UV absorption and emission lines in an historically low-state spectrum of the Seyfert 1 galaxy NGC 5548, which we obtained in 2004 February at high spatial and spectral resolution with the Space Telescope Imaging Spectrograph on the Hubble Space Telescope. We isolate a component of emission with a width of 680 km s(-1) that arises from an "intermediate-line region" (ILR), similar to that we discovered in NGC 4151, at a distance of similar to 1 pc from the central continuum source. From a detailed analysis of the five intrinsic absorption components in NGC 5548 and their behavior over a span of eight years, we present evidence that most of the UV absorbers only partially cover the ILR and do not cover an extended region of UV continuum emission, most likely from hot stars in the circumnuclear region. We also find that four of the UV absorbers are at much greater distances (greater than 70 pc) than the ILR, and none have sufficient N V or C IV column densities to be the ILR in absorption. At least a portion of the UV absorption component 3, at a radial velocity of -530 km s(-1), is likely responsible for most of the X-ray absorption, at a distance less than 7 pc from the central source. The fact that we see the ILR in absorption in NGC 4151 and not in NGC 5548 suggests that the ILR is located at a relatively large polar angle (similar to 45 degrees) with respect to the narrow-line region outflow axis.
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    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.
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    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.