High-Resolution Emission-Line Imaging of Seyfert Galaxies. II. Evidence for Anisotropic Ionizing Radiation

Wilson, A. S.; Ward, M. J.; Haniff, Christopher A.

doi:10.1086/166822

Cited by 71 publications

(41 citation statements)

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“…the ULIRGs are powered by star-bursts. For several of the Seyferts in our sample, however, at least 50% of the FIR emission may come from the AGN activity, even if a star-burst also contributes to the total luminosity: Kohno et al (1999) suggest that Seyferts with jets have particularly bright HCN emission and that the dense gas, which is a component of a large-scale obscuration 11 confines the jet (Antonucci & Miller 1985;Wilson et al 1988;Tadhunter & Tsvetanov 1989;Wilson & Tsvetanov 1994;Baker & Scoville 1998). Also, Bryant (1997); Kohno et al (1999) discuss the connection between very high HCN/CO ratios and these nuclei and point out that Seyfert nuclei are associated with the lowest published HCN/CO ratios 9 We achieve the same value using only galaxies with v > ∼ 4000 km s −1 , thus again indicating that the CO may be centralised.…”

Section: Discussionmentioning

confidence: 92%

Dense molecular gas in Seyfert galaxies

Curran

Aalto

Booth

2000

Astron. Astrophys. Suppl. Ser.

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Abstract.We have used the 20 m Onsala and 15 m SEST telescopes to observe the CO J = 1 → 0 (simultaneously with CO J = 2 → 1 at SEST) and HCN J = 1 → 0 (simultaneously with CS J = 3 → 2 at SEST) transitions in 20 Seyfert galaxies. The sample consists of the 18 galaxies detected in CO J = 1 → 0 by Heckman et al. (1989) plus 2 which were not detected in their survey. We have successfully detected all of the galaxies in the CO transition and 13 in HCN of which NGCs 1667, 2273, 5033, 5135, 6814 and Mrk 273 are new detections. For the galaxies in which the beam-width exceeds ≈ 10 kpc we find that LHCN LCO ≈ 1/6, i.e. a global ratio similar to that of ultraluminous infrared galaxies and over 10 times the ratio for normal spiral galaxies. This implies thatLFIR LCO (normal spirals) and we believe that the far infrared fluxes in our sample arise from star-burst activity, although we cannot rule out the possibility of a contribution from active galactic nuclei.

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Section: Discussionmentioning

confidence: 92%

Dense molecular gas in Seyfert galaxies

Curran

Aalto

Booth

2000

Astron. Astrophys. Suppl. Ser.

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“…Wilson et al 1988;Baum & Heckman 1989;Axon et al 2000;O'Dea et al 2000). Assuming radiative recombination under case B conditions, the number of ionizing photons N Hβ needed to produce the observed Hβ luminosity L Hβ is:…”

Section: Can the Central Agn Power The Emission Line Luminosity In Thmentioning

confidence: 99%

HST/STIS low dispersion spectroscopy of three Compact Steep Spectrum sources

Labiano¹,

O’Dea²,

Gelderman³

et al. 2005

A&A

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Abstract. We present Hubble Space Telescope Imaging Spectrograph long-slit spectroscopy of the emission line nebulae in the compact steep spectrum radio sources 3C 67, 3C 277.1, and 3C 303.1. We derive BPT (Baldwin-Philips-Terlevich; Baldwin et al. 1981) diagnostic emission line ratios for the nebulae which are consistent with a mix of shock excitation and photoionization in the extended gas. In addition, line ratios indicative of lower ionization gas are found to be associated with higher gas velocities. The results are consistent with a picture in which these galaxy scale radio sources interact with dense clouds in the interstellar medium of the host galaxies, shocking the clouds thereby ionizing and accelerating them.

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“…Emission-line imaging shows anisotropic ionization cones around many Seyfert 2 galaxies, indicating that the ionizing radiation emitted from the nucleus is collimated (Wilson et al 1993;Pogge & De Robertis 1993;Wilson & Tsvetanov 1994). The apparent deficit of ionizing photons in Seyfert 2 galaxies seems to originate from a Compton-thick dusty torus blocking high-energy photons (Wilson et al 1988;Storchi-Bergmann et al 1992) but reprocessing them into mid-IR photons.…”

Section: Introductionmentioning

confidence: 97%

Probing the Dust Obscuration in Seyfert Galaxies using Infrared Spectroscopy. II. Implication for the Unification of Seyfert Galaxies

Rhee¹,

Larkin²

2005

ApJ

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We report near-IR spectroscopic observations of 11 Seyfert galaxies (six Seyfert 1s, one Seyfert 1.9, and four Seyfert 2s) and additional galaxies (four LINERs, two H ii, and one type 2 transition) for comparison, obtained using the Gemini twin-channel near-IR camera on the Shane 3 m telescope at Lick Observatory. With the unique design of the Gemini camera, full J and K spectra were taken simultaneously through the same slit. This produced accurate line ratios of hydrogen recombination lines over a large wavelength baseline. For the Seyfert 1s ( 1.5), the line ratios of Pa /Br are not only comparable in both broad-and narrow-line regions but also consistent with case B recombination, indicating little or no reddening in both narrow-and broad-line regions. Seyfert 2 (>1.5) galaxies, however, show substantial reddening toward the narrow-line regions. We compare optical reddening data from the literature and find significant support for the dichotomy between Seyfert 1s and Seyfert 2s, at least in lowluminosity objects. Two different scenarios are explored to explain the observed difference in reddening: a difference in reddening due to an extended dusty torus under active galactic nucleus unification, and a difference due to a different grain size distribution between the two Seyfert types. We also discuss a similar potential difference found in the strength of the 9.7 m silicate line, along with a possible correlation between the narrow-line reddening and the strength of the silicate absorption line. We also analyzed CO band head absorption features longward of 2.3 m to look for nonstellar contamination and evidence of recent star formation activity. The CO band head in Seyfert 1s shows heavy contamination from nonstellar radiation, which is correlated with an H À K nuclear color excess. We confirm that the CO spectroscopic indices in both Seyfert types do not show evidence of recent star formation. Taking the nonstellar contamination into account, there is little evidence from the CO index for a difference in star formation rates in the nuclei of Seyfert 1s and Seyfert 2s in our low-luminosity sample.

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High-Resolution Emission-Line Imaging of Seyfert Galaxies. II. Evidence for Anisotropic Ionizing Radiation

Cited by 71 publications

References 0 publications

Dense molecular gas in Seyfert galaxies

Dense molecular gas in Seyfert galaxies

HST/STIS low dispersion spectroscopy of three Compact Steep Spectrum sources

Probing the Dust Obscuration in Seyfert Galaxies using Infrared Spectroscopy. II. Implication for the Unification of Seyfert Galaxies

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