Detailed observations of NGC 4151 with IUE - I Low dispersion data up to 1979 January*

Penston, M. V.; Boksenberg, A.; Bromage, G. E.; Clavel, J.; Elvius, A.; Gondhalekar, P. M.; Jordan, C.; Lind, J.; Lindegren, L.; Perola, G. C.; Snijders, M. A. J.; Tanzi, E. G.; Tarenghi, M.; Ulrich, M. H.

doi:10.1093/mnras/196.4.857

Cited by 38 publications

(17 citation statements)

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“…Alexander et al 1999) report reddening estimates which range from almost negligible E ( B − V ) = 0.04–0.05) (e.g. Penston et al 1981; Kriss et al 1995) to the considerable E ( B − V ) = 0.13 (Malkan 1983). From a variety of methods (and data), including near‐IR emission lines, Ward et al (1987) get E ( B − V ) ∼ 0.23 mag, while Rieke & Lebofsky (1981) obtain 0.5 < A V < 0.8.…”

Section: Discussionmentioning

confidence: 99%

Feeding versus feedback in NGC 4151 probed with Gemini NIFS - I. Excitation

Storchi‐Bergmann

McGregor

Riffel

et al. 2009

Monthly Notices of the Royal Astronomical Society

140

242

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We have used the Gemini Near‐infrared Integral Field Spectrograph (NIFS) to map the emission‐line intensity distributions and ratios in the narrow‐line region (NLR) of the Seyfert galaxy NGC 4151 in the Z, J, H and K bands at a resolving power ≥5000, covering the inner ≈200 × 300 pc of the galaxy at a spatial resolution of ≈8 pc. We present intensity distributions in 14 emission lines, which show three distinct behaviours. (1) Most of the ionized gas intensity distributions are extended to ≈100 pc from the nucleus along the region covered by the known biconical outflow (position angle, PA = 60/240°, NE–SW), consistent with an origin in the outflow; while the recombination lines show intensity profiles which decrease with distance r from the nucleus as I∝r−1, most of the forbidden lines present a flat intensity profile (I∝r0) or even increasing with distance from the nucleus towards the border of the NLR. (2) The H2 emission lines show completely distinct intensity distributions, which avoid the region of the bicone, extending from ≈10 to ≈60 pc from the nucleus approximately along the large‐scale bar, almost perpendicular to the bicone axis. This morphology supports an origin for the H2‐emitting gas in the galaxy plane. (3) The coronal lines show a steep intensity profile, described by I∝r−2; the emission is clearly resolved only in the case of [Si vii], consistent with an origin in the inner NLR. Using the line‐ratio maps [Fe ii] 1.644/1.257 and Pa β/Br γ, we obtain an average reddening of E(B−V) ≈ 0.5 along the NLR and E(B−V) ≥ 1 at the nucleus. Our line‐ratio map [Fe ii] 1.257 μm/[P ii] 1.189 μm of the NLR of NGC 4151 is the first such map of an extragalactic source. Together with the [Fe ii]/Paβ map, these line ratios correlate with the radio intensity distribution, mapping the effects of shocks produced by the radio jet on the NLR. These shocks probably release the Fe locked in grains and produce an enhancement of the [Fe ii] emission at ≈1 arcsec from the nucleus. At these regions, we obtain electron densities Ne≈ 4000 cm−3 and temperatures Te≈ 15 000 K for the [Fe ii]‐emitting gas. For the H2‐emitting gas, we obtain much lower temperatures of Texc≈ 2100 K and conclude that the gas is in thermal equilibrium. The heating necessary to excite the molecule may be due to X‐rays escaping perpendicular to the cone (through the nuclear torus, if there is one) or to shocks probably produced by the accretion flow previously observed along the large‐scale bar. The distinct intensity distributions and physical properties of the ionized and molecular gas, as well as their locations, the former along the outflowing cone, and the latter in the galaxy plane surrounding the nucleus, suggest that the H2‐emitting gas traces the active galactic nuclei feeding, while the ionized gas traces its feedback.

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Section: Discussionmentioning

confidence: 99%

Feeding versus feedback in NGC 4151 probed with Gemini NIFS - I. Excitation

Storchi‐Bergmann

McGregor

Riffel

et al. 2009

Monthly Notices of the Royal Astronomical Society

140

242

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“…Mrk 817 is not alone in exhibiting variable absorbers. Variability in UV absorption lines has been detected in several Seyfert 1s, including NGC 4151 (e.g., Penston et al 1981;Bromage et al 1985;Kraemer et al 2006), NGC 3516 (e.g., Ulrich & Boisson 1983), NGC 5548 (e.g., Shull & Sachs 1993;Crenshaw et al 2009), and NGC 3783 (e.g., Maran et al 1996;Gabel et al 2005). The cause of variability of intrinsic absorbers is attributed to a change in ionization state or shielding of the photo-ionizing continuum of an outflowing wind or bulk motions of an absorbing cloud/clouds.…”

Section: Intrinsic Absorptionmentioning

confidence: 99%

Ultraviolet and X-Ray Variability of the Seyfert 1.5 Galaxy Markarian 817

Winter

Danforth

Vasudevan

et al. 2011

ApJ

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We present an investigation of the ultraviolet and X-ray spectra of the Seyfert 1.5 galaxy Markarian 817. The ultraviolet analysis includes two recent observations taken with the Cosmic Origins Spectrograph in August and December 2009, as well as archival spectra from the International Ultraviolet Explorer and the Hubble Space Telescope. Twelve Lyα absorption features are detected in the 1997 GHRS and 2009 COS spectra -of these, four are associated with high-velocity clouds in the interstellar medium, four are at low-significance, and the remaining four are intrinsic features, which vary between the GHRS and COS observations. The strongest intrinsic absorber in the 1997 spectrum has a systemic velocity of ∼ −4250 km s −1 . The corresponding feature in the COS data is five times weaker than the GHRS absorber. The three additional weak (equivalent width from 13-54 mÅ) intrinsic Lyα absorbers are at systemic velocities of −4100 km s −1 , −3550 km s −1 , and −2600 km s −1 . However, intrinsic absorption troughs from highly ionized C IV and N V, are not detected in the COS observations. No ionized absorption signatures are detected in the ∼ 14 ks XMM-Newton EPIC spectra. The factor of five change in the intrinsic Lyα absorber is most likely due to bulk motions in the absorber, since there is no drastic change in the UV luminosity of the source from the GHRS to the COS observations. In a study of variability of Mrk 817, we find that the X-ray luminosity varies by a factor of ∼ 40 over 20 years, while the UV continuum/emission lines vary by at most a factor of ∼ 2.3 over 30 years. The variability of the X-ray luminosity is strongly correlated with the X-ray power-law index, but no correlation is found with the simultaneous optical/UV photometry.

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“…Estimates of the reddening of the NLR in NGC 4151 range from almost negligible, E b−v = 0.04 (Kriss et al 1995), 0.05 (Penston et al 1981;Wu & Weedman 1978;Boksenberg et al 1978), to considerable, E b−v = 0.12 (Kaler 1976), 0.13 (Malkan 1983), and 0.09 to 0.28 (Ward et al 1987). The elemental abundances and the internal dust content of the line emitting gas are even less certain.…”

Section: The Line Emitting Gasmentioning

confidence: 99%

Infrared Spectroscopy of NGC 1068: Probing the Obscured Ionizing AGN Continuum

Alexander

Lutz

Sturm

et al. 2000

ApJ

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The ISO-SWS 4 infrared spectroscopic observations of the nucleus of Seyfert galaxy NGC 4151, which are described in a companion paper, are used together with a compilation of UV to IR narrow emission line data to determine the spectral shape of the obscured extreme-UV continuum that photoionizes the narrow line emitting gas in the active galactic nucleus. We present a new method to determine the best fitting photoionizing continuum and emission line cloud model from a heterogeneous set of emission line data.For NGC 4151, we find a best-fit model that reproduces the observed line fluxes to within a factor of 2 on average, and which is consistent with the observed geometry of the optical Narrow Line Region (NLR). Our model consists of a clumpy, optically thick (ionization bounded) gas distribution, with a hydrogen gas density of ∼ 1000 cm −3 and a volume filling factor of 6.5 10 −4 .Our best fitting spectral energy distribution (SED) falls sharply beyond the Lyman limit and then rises sharply again towards 100 eV. In particular, it does not display a 'Big Blue Bump' signature of a hot accretion disk. We find that this SED, which best reproduces the NLR line emission on the 100-500 pc scale, does not have enough UV photons to produce the observed BLR recombination emission from the inner 1 pc. This suggests that the BLR is photoionized by the intrinsic continuum source, which does have a strong UV component (perhaps a Big Blue Bump), but that this UV component is absorbed by material located between the NLR and BLR. Our analysis suggests that the absorber consists of ∼ 5 10 19 cm −2 of neutral hydrogen. Such an absorber was independently detected by UV absorption lines (Kriss et al. 1992(Kriss et al. , 1995.Using our new method, we confirm our previous conclusion that a Big Blue Bump is present in the SED of the Seyfert 2 galaxy Circinus.4 Based on observations made with ISO, an ESA project with instruments funded by ESA member states (especially the PI countries: France, Germany, The Netherlands and the United Kingdom) and with the participation of ISAS and NASA. The SWS is a joint project of SRON and MPE.-2 -

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Detailed observations of NGC 4151 with IUE - I Low dispersion data up to 1979 January*

Cited by 38 publications

References 0 publications

Feeding versus feedback in NGC 4151 probed with Gemini NIFS - I. Excitation

Feeding versus feedback in NGC 4151 probed with Gemini NIFS - I. Excitation

Ultraviolet and X-Ray Variability of the Seyfert 1.5 Galaxy Markarian 817

Infrared Spectroscopy of NGC 1068: Probing the Obscured Ionizing AGN Continuum

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