Broad emission features in QSOs and active galactic nuclei. II - New observations and theory of Fe II and H I emission

Wills, Beverley J.; Netzer, H.; Wills, D.

doi:10.1086/162767

Cited by 355 publications

(395 citation statements)

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“…Therefore, we have adopted a reddening value of E BÀV ¼ 0:10 AE 0:05, of which 0.04 is Galactic (Schlegel, Finkbeiner, & Davis 1998). This is in rough agreement with Kriss et al (1996a) but suggests a UV power law that is more consistent with typical values for low-luminosity AGNs (Wills, Netzer, & Wills 1985). If the dust composition and dust-to-gas ratio are the same as in our Galaxy (see Mathis, Rumpl, & Nordsieck 1977), the intrinsic reddening, E BÀV % 0:06, requires a neutral hydrogen column of $3:0 Â 10 20 cm À2 (Shull & van Steenberg 1985).…”

Section: Inputs To the Modelsmentioning

confidence: 79%

Variable Ultraviolet Absorption in the Seyfert 1 Galaxy NGC 3516: The Case for Associated Ultraviolet and X‐Ray Absorption

Kraemer

Crenshaw

George

et al. 2002

ApJ

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We present observations of the UV absorption lines in the Seyfert 1 galaxy NGC 3516, obtained at a resolution of =D % 40; 000 with the Space Telescope Imaging Spectrograph (STIS) on 2000 October 1. The UV continuum was $4 times lower than that observed during 1995 with the Goddard High Resolution Spectrograph (GHRS), and the X-ray flux from a contemporaneous Chandra X-Ray Observatory observation was a factor of $8 below that observed with ASCA. The STIS spectra show kinematic components of absorption in Ly , C iv, and N v at radial velocities of À376, À183, and À36 km s À1 (components 1, 2, and 3+4, respectively), which were detected in the earlier GHRS spectra; the last of these is a blend of two GHRS components that have increased greatly in column density. Four additional absorption components have appeared in the STIS spectra at radial velocities of À692, À837, À994, and À1372 km s À1 (components 5-8); these may also have been present in earlier low-flux states observed by the International Ultraviolet Explorer. Based on photoionization models, we suggest that the components are arranged in increasing radial distance in the order 3+4, 2, 1, followed by components 5-8. We have achieved an acceptable fit to the X-ray data using the combined X-ray opacity of the UV components 1, 2, and 3+4. By increasing the UV and X-ray fluxes of these models to match the previous high states, we are able to match the GHRS C iv column densities, the absence of detectable C iv absorption in components 5-8, and the 1994 ASCA spectrum. We conclude that variability of the UV and X-ray absorption in NGC 3516 is primarily due to changes in the ionizing flux.

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Section: Inputs To the Modelsmentioning

confidence: 79%

Variable Ultraviolet Absorption in the Seyfert 1 Galaxy NGC 3516: The Case for Associated Ultraviolet and X‐Ray Absorption

Kraemer

Crenshaw

George

et al. 2002

ApJ

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“…The intensity ratio of FeII(opt)/Hβ is estimated to be 3.5±1.1. This value is slightly larger than those of low-z quasars; 1.63±0.88 (Wills et al 1985). However, we cannot conclude that S4 0636+68 belongs to a class of strong iron quasars (cf.…”

Section: S4 0636+68mentioning

confidence: 55%

“…Yoshii, Tsujimoto, & Nomoto (1996) 2) PKS 1937−101: The little evidence for Fe emission lines suggests that the major epoch of star formation in this quasar host is different from that in B1422+231. The α elements, such as O and Mg, come from SNII's of massive star origin and thus are quickly expelled into the interstellar space after the major episode of star formation (within a few 10 6 to 10 7 years).…”

Section: Discussionmentioning

confidence: 95%

“…However, our observation has shown that the major Fe enrichment has not yet been made in PKS 1937−101. The bulk of iron come from SNIa's whose progenitors' lifetime is very likely to cluster around ∼ 1.5 Gyr (Yoshii et al 1996). Therefore, the Fe enrichment may start at 1.5 Gyr after the onset of the first, major star formation in quasar host galaxies.…”

Section: Discussionmentioning

confidence: 99%

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The Epoch of Major Star Formation in High-z Quasar Hosts

Taniguchi

Arimoto

Murayama

et al. 1997

ESO Astrophysics Symposia

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“…Photoionization models considered here do not include iron, which can dominate the thermal equilibrium of lower ionization clouds (Wills, Netzer, & Wills 1985). Work is now underway within the atomic physics community to generate the basic data needed to treat FeII emission properly.…”

Section: The Atomic Databasementioning

confidence: 99%