High-resolution ultraviolet spectra of the dwarf Seyfert 1 galaxy NGC 4395: Evidence for intrinsic absorption

被引:15
作者
Crenshaw, DM
Kraemer, SB
Gabel, JR
Schmitt, HR
Filippenko, AV
Ho, LC
Shields, JC
Turner, TJ
机构
[1] Georgia State Univ, Dept Phys & Astron, Astron Off, Atlanta, GA 30303 USA
[2] Catholic Univ Amer, Greenbelt, MD 20771 USA
[3] NASA, Astron & Solar Phys Lab, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA
[4] Univ Colorado, Ctr Astrophys & Space Astron, UCB 389, Boulder, CO 80309 USA
[5] Natl Radio Astron Observ, Charlottesville, VA 22903 USA
[6] Univ Calif Berkeley, Dept Astron, Berkeley, CA 94720 USA
[7] Observ Carnegie Inst Washington, Pasadena, CA 91101 USA
[8] Ohio Univ, Dept Phys & Astron, Athens, OH 45701 USA
[9] Univ Maryland Baltimore Cty, Joint Ctr Astrophys, Baltimore, MD 21250 USA
关键词
galaxies : individual (NGC 4395); galaxies : Seyfert; ultraviolet : galaxies;
D O I
10.1086/422468
中图分类号
P1 [天文学];
学科分类号
0704 ;
摘要
We present ultraviolet spectra of the dwarf Seyfert 1 nucleus of NGC 4395, obtained with the Far Ultraviolet Spectroscopic Explorer ( FUSE) and the Hubble Space Telescope Space Telescope Imaging Spectrograph at velocity resolutions of 7 - 15 km s(-1). We confirm our earlier claim of C IV absorption in low-resolution UV spectra and detect a number of other absorption lines with lower ionization potentials. In addition to the Galactic lines, we identify two kinematic components of absorption that are likely to be intrinsic to NGC 4395. We consider possible origins of the absorption, including the interstellar medium ( ISM) of NGC 4395, the narrow-line region, the outflowing UV absorbers, and the X-ray "warm absorbers.'' Component 1, at a radial velocity of - 770 km s(-1) with respect to the nucleus, is only identified in the C IV lambda1548.2 line. It most likely represents an outflowing UV absorber, similar to those seen in a majority of Seyfert 1 galaxies, although additional observations are needed to confirm the reality of this feature. Component 2, at - 114 km s(-1), most likely arises in the ISM of NGC 4395; its ionic column densities cannot be matched by photoionization models with a power-law continuum. Our models of the highly ionized X-ray absorbers claimed for this active galactic nucleus indicate that they would have undetectable C IV absorption, but large O vi and H I columns should be present. We attribute our lack of detection of the O vi and Lybeta absorption from the X-ray absorbers to a combination of noise and dilution of the nuclear spectrum by hot stars in the large FUSE aperture.
引用
收藏
页码:152 / 158
页数:7
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