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NASA NTRS1990

Observational effects of interaction in the Seyfert galaxy NGC 7469

Some pecularities of the circummucleus of the Seyfert galaxy NGC 7469 were revealed, plausibly caused by interaction with the satellite IC 5283 and a starlike detail, situated on the edge of the west spiral branch 14 seconds from the nucleus. Shock excited H II regions were noted in the part of NGC 7469 turned toward the satellite IC 5283. The galaxy's central radio structure (lambda approx. 6 cm) stretches in the direction toward the satellite IC 5283 and the starlike detail. The spectum and color index of the starlike detail suggest that it is a cluster of early type stars (M sub V = -19 sup m) and dust clouds (A sub V = 3 sup m), in NGC 7469.

Pronik, I. I.↗
NASA NTRS1990

Accretion tori and cones of ionizing radiation in Seyfert galaxies

The photoionization of extended narrow-line regions in Seyfert galaxies by the radiation produced in a thick accretion disk is studied. The emission-line spectrum is calculated for a range of black hole masses, varying the values of the ionization parameter and the disk size. It is found that models with a million solar masses fit observations of very large accretion disk sizes, while models with 10 million solar masses fit them better with smaller disks. The latter models are preferable since they have lower super-Eddington accretion rates.

Acosta-Pulido, Jose A.↗
NASA NTRS1988

Ultraviolet spectra of the narrow-lined Seyfert galaxies Markarian 573 and Markarian 1388

Ultraviolet spectra, obtained with the IUE satellite, are presented for the unusually narrow-lined Seyfert galaxies Mrk 573 and Mrk 1388. The data support class 2 identifications for both galaxies and also suggest the need for more energetic ionizing radiation in the most recently published Seyfert 2 galaxy photoionization calculation.

Macalpine, Gordon M.↗
NASA NTRS1992

The broad emission line and continuum variations of Seyfert galaxies. I - Time scales and amplitudes

Spectroscopic observations of 13 Seyfert 1 galaxies made from 1979 to 1984 at Palomar and Steward Observatories were analyzed for Balmer-line and optical continuum variability. The majority of the galaxies showed significant variations, particularly in the continuum. Typical peak-to-peak changes for H-beta and H-gamma integrated line fluxes were 100-200 percent, while the continua varied by 200-350 percent. In several cases, Balmer-line and continuum variations were found to be strongly correlated, as expected for photoionization by a central continuum source. However, these correlations were found to be highly nonlinear. Significant correlations were found between variability amplitude and global AGN properties such as luminosity. Moreover, a significant number of variations occurring on short time scales constrains the size of the broad-line region in Seyfert galaxies to about 90 lt-days across or less.

Rosenblatt, Edward I.↗
NASA NTRS2003

An XMM-Newton Observation of the Seyfert Galaxy 1H0419-577 in an Extreme Low State

Previous observations of the luminous Seyfert galaxy 1H 0419-577 have found its X-ray spectrum to range from that of a typical Seyfert 1 with 2-10 keV power law index Gamma approx. 1.9 to a much flatter power law of Gamma approx. 1.5 or less. We report here a new XMM-Newton observation which allows the low state spectrum to be studied in much greater detail than hitherto. We find a very hard spectrum (Gamma approx. 1.0) which exhibits broad features that can be modelled with the addition of an extreme relativistic Fe K emission line or with partial covering of the underlying continuum by a substantial column density of near-neutral gas. Both the EPIC and RGS data show evidence for strong line emission of OVII and OVIII requiring an extended region of low density photoionised gas in 1H 0419- 577. Comparison with an earlier XMM-Newton observation when 1H 0419-577 was X-ray bright indicates the dominant spectral variability occurs via a steep power law component.

Pounds, K. A.↗
NASA NTRS1975

On the interpretation of FE 2 emission profiles in Seyfert galaxies and QSOs

High-resolution spectral scans of several QSOs and Seyfert galaxies show broad Balmer lines and permitted Fe II lines in emission. It is suggested that a careful comparison of the Fe II and Balmer profiles may distinguish between the different proposed mechanisms for broadening of the lines. In particular, if the Fe II profile is much narrower that the hydrogen profile, the suprathermal particle mechanism is most likely presented.

Ptak, R.↗
NASA NTRS1997

A Near-Infrared Imaging Study of Seyfert Galaxies with Extended Emission line Regions

We present a near-infrared J,H,K and L' band (1.25 - 3.80 mue) imaging study of a sample of Seyfert galaxies, including some of the best studied examples of these with extended emission line regions (EELR). The observed near-IR nuclear colors are consistent with mixture of emmisions from an old stellar population and unredening hot dust.

Near-Infrared Seyfert Galaxies↗
NASA NTRS1976

On the interpretation of Fe II emission profiles in Seyfert galaxies and QSOs

Recent high-resolution spectral scans of several QSOs and Seyfert galaxies show broad Balmer lines and permitted Fe II lines in emission. It is suggested that a careful comparison of the Fe II and Balmer profiles may distinguish between the different proposed mechanisms for broadening of the lines. For a suprathermal-particle model, the hydrogen and Fe II lines arise in the same region, with the Fe II emission produced by the dense ambient gas that is excited by the flux of suprathermal particles. Hence, such a model predicts that the Fe II lines are substantially narrower than the hydrogen lines.

Ptak, R.↗
NASA NTRS1994

Near-infrared continuum and 3.3 micrometer(s) polycyclic aromatic hydrocarbon imaging of the starburst ring in the type 1 Seyfert galaxy NGC 7469

High resolution near-infrared images of the type 1 Seyfert galaxy NGC 7469 have been obtained to probe its dusty nuclear environment. Direct J, H, and K images are relatively featureless, but residual images created by subtracting a smooth model based on best-fitting elliptical isophotes reveal a tight inner spiral whose high surface-brightness portions correspond to a previously detected 3 sec (1 kpc) diameter ring of radio continuum emission. The inner infrared spiral arms extended approximately equal to 4 sec NW and SE from the nucleus, and the NW arm joins up with large-scale spiral structure visible in the R band. The residual images also show a bar-like structure aligned with the brightest infrared/radio hotspots at PA approximately equal to 50 deg. Three infrared hotspots are detected which align remarkably well with 6 cm radio continuum sources. The near-infrared ring and the hotspots are visible in the residual images, and in a high-resolution direct K-band image restored to an effective resolution of 0.65 sec (FWHM) using the Richardson-Lucy algorithm. The infrared hotspots have luminosities of nuL(sub nu) (2.2 micrometer(s)) approximately equal to 10(exp 8) solar luminosity (M(sub k) approximately equal to -16 mag), suggesting they are either giant H II regions or individual supernovae. The two brightest regions may be associated with enhanced star formation triggered by orbit crowding of gas where spiral arms emerge from an inner bar. Narrowband (delta lambda/lambda approximately 1.5%) imaging in the 3.28 micrometer(s) dust emission feature and surrounding continuum confirms the 3 sec diameter 3.28 micrometer(s) emission region detected previously using multiaperture photometry. The extended polycyclic aromatic hydrocarbon (PAH) emission is slightly elongated and aligned with published 1O III1 line emission and 12.5 micrometer(s) continuum emission, apparently tracing the starburst. The presence of approximately equal to 25% of the total 3.28 micrometer(s) PAH emission within R less than 1 sec demonstrates that a starburst within the central few hundred parsecs must supply a significant fraction of the infrared continuum from the nucleus, and there is apparently sufficient shielding material between the starburst and the active galactic nucleus (AGN) to preserve the PAHs along our line of sight to the nucleus.

Mazzarella, J. M.↗
NASA NTRS2002

Using Multiwavelength Observations to Determine the Black Hole Mass and Accretion Rate in the Type 1 Seyfert Galaxy NGC 5548

We model the spectral energy distribution of the type 1 Seyfert galaxy NGC 5548, fitting data from simultaneous optical, UV, and X-ray monitoring observations. We assume a geometry consisting of a hot central Comptonizing region surrounded by a thin accretion disk. The properties of the disk and the hot central region are determined by the feedback occurring between the hot Comptonizing region and thermal reprocessing in the disk that, along with viscous dissipation, provides the seed photons for the Comptonization process. The constraints imposed upon this model by the multiwavelength data allow us to derive limits on the central black hole mass, Mu is approximately or less than 2x10(exp 7) solar mass, the accretion rate, Mu is approximately or less than 2.5x10(exp 5) sq solar mass per year/Mu, and the radius of the transition region between the thin outer disk and the geometrically thick, hot inner region, is approximately 2-5x10(exp 14) cm.

Chiang, James↗
NASA NTRS1993

Near-Infrared Continuum and 3.3um PAH Imaging of the Starburst Ring in the Type I Seyfert Galaxy NGC 7469

High resolution near-infrared images of the type 1 Seyfert Galaxy NGC 7469 have been obtained to probe its dusty nuclear environment. Direct images are relatively featureless, but residual images created by subtacting a smooth model based on best-fitting elliptical isoophotes reveal a tight inner spiral whose high surface-brightness portions correspond to a previously detected 3.

ring↗
NASA NTRS2008

Constraining the Active Galactic Nucleus Contribution in a Multiwavelength Study of Seyfert Galaxies

We have studied the relationship between the high- and low-ionization [O IV] (lambda)25.89 microns, [Ne III] (lambda)15.56 microns, and [Ne II] (lambda)12.81 microns emission lines with the aim of constraining the active galactic nuclei (AGNs) and star formation contributions for a sample of 103 Seyfert galaxies.We use the [O IV] and [Ne II] emission as tracers for the AGN power and star formation to investigate the ionization state of the emission-line gas.We find that Seyfert 2 galaxies have, on average, lower [O IV]/[Ne II] ratios than Seyfert 1 galaxies. This result suggests two possible scenarios: (1) Seyfert 2 galaxies have intrinsically weaker AGNs, or (2) Seyfert 2 galaxies have relatively higher star formation rates than Seyfert 1 galaxies. We estimate the fraction of [Ne II] directly associated with the AGNs and find that Seyfert 2 galaxies have a larger contribution from star formation, by a factor of approx.1.5 on average, than what is found in Seyfert 1 galaxies. Using the stellar component of [Ne II] as a tracer of the current star formation, we found similar star formation rates in Seyfert 1 and Seyfert 2 galaxies.We examined the mid- and far-infrared continua and found that [Ne II] is well correlated with the continuum luminosity at 60 microns and that both [Ne III] and [O IV] are better correlated with the 25 micron luminosities than with the continuum at longer wavelengths, suggesting that the mid-infrared continuum luminosity is dominated by the AGN, while the far-infrared luminosity is dominated by star formation. Overall, these results test the unified model of AGNs and suggest that the differences between Seyfert galaxies cannot be solely due to viewing angle dependence.

Melendez, M.↗
NASA NTRS1983

Far-infrared observations of the type 1 Seyfert galaxy NGC 4051

The Kuiper Airborne Observatory was used, together with a seven-element array, in measurements of the far-IR flux from the Seyfert galaxy NGC 4051. Flux densities within and outside of the central region were found to be comparable, with a possible local peak of emission in the west, and a total far-IR luminosity of 3.4 + or - 0.8 billion solar luminosities. The spectral shape of the radiation and its extended distribution, together with data at other wavelengths, suggest that the IR emission arises from warm dust. The relatively weak IR flux, and the apparent lack of dust and gas by comparison to the total (virial) material, indicate less active star formation than that found in such galaxies as the type 2 Seyfert, NGC 1068.

Smith, H. A.↗
NASA NTRS1981

The C IV 1550 profile in type 1 Seyfert galaxies

The paper presents C IV 1550 A line profiles for the type 1 Seyfert galaxies NGC 5548, Mrk 509, NGC 7469, and MCG-2-58-22. Several line broadening mechanisms and theoretical line profiles are considered, and random motion of discrete clouds is ruled out. A spherical ensemble of discrete clouds with steady outflow or inflow produces a logarithmic profile, but does not account for the highly extended wings. A spherical ensemble with ballistic outflow produces a profile of the first exponential integral function, and fits the observed profile to the continuum level. Although C IV profiles favor the ballistic model, both Mrk 509 and NGC 7469 have significant asymmetry, and Balmer lines with a higher optical depth show higher asymmetry and redshift than all four galaxies.

Wu, C.-C.↗
NASA NTRS1990

The nature of the optical variations of Seyfert galaxy 3C 120

Results are presented from 61 years of optical observations of the Seyfert galaxy 3C 120. A previously published model of the 3C 120 light curve, derived from power spectrum analysis, is found to be valid for historical as well as current data. It is concluded that the optical variations of 3C 120 can be separated into a linear component, a sinusoidal component, and rapid, high-amplitude flares. Possible sources of the regular variations observed in 3C 120 are also suggested in the context of accretion models and other theoretical models.

Webb, James R.↗