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A program to obtain simultaneous observations from the X-ray to the IR of Seyfert I galaxies is outlines. Of particular interest is the variability of these Seyfert nuclei. The continuum flux distribution in the UV for AkN 120 and ESO 113-IG45 (F-9) is examined.
Strong variable X-ray emission from the nearby low luminosity Seyfert 1 galaxy NGC 4051 was discovered during observations with the imaging proportional counter of the Einstein Observatory. During one 2304 second observation, the X-ray flux more than doubled in an approximately linear fashion, and a 70% increase for 150 seconds was seen during another 968 second observation. Evidence is presented which demonstrates that the X-ray spectrum of NGC 4051 is unusually soft compared to Seyfert 1 galaxies or QSOs. The emission mechanism is probably not synchrotron or synchrotron self-Compton, but the emission can be plausibly explained by various black hole accretion models.
It is shown that the X-ray source X0459 + 034 is a Seyfert galaxy of intermediate type, and optical spectroscopy and radio observations were performed to study the nature of the object. The object appears almost stellar and slightly diffuse on Palomar Sky Survey prints. The source is identified as a Type 1.5 Seyfert with broad and narrow line components of redshift 0.016 + or - 0.001, according to H-Beta line profile. In addition, the broad line component H-Beta equivalent width is larger than that of the narrow line component by a factor of three. Finally, it is shown that this is a weak radio source with a steep nonthermal spectrum and an angular extent of approximately 3 in., and the composite radio-to-X-ray spectrum suggests that in different spectral regions, different relativistic electron populations or emission mechanisms are contributing factors.
IUE Explorer data with a 6-A resolution are reported for Ly-alpha, C IV 1550 A, C III semiforbidden line 1909 A, and Mg II 2800 A, as well as the continuum at 1450 A, for 20 Seyfert galaxies and one quasar. Good correlation is found between the continuum and the line fluxes, indicating that photoionization is the dominant heating mechanism for these active galactic nuclei. A combination of the data for Seyferts and high redshift quasars covering five orders of magnitude in continuum luminosity shows the lower luminosity objects to have higher equivalent widths for their emission lines, suggesting that the covering factor increases with decreasing luminosity.
Seyfert's Sextet and VV 172, 5-m photographs have been subjected to image processing to yield field-galaxy density analysis, redshift-scaled imagery, interaction morphology display and enhancement, color difference imagery,modeling of the VV 172 halo, and image texture analysis of the spiral galaxy components of Seyfert's Sextet. An effort is made to evaluate the evidence for physical association of the discordant redshift components of these groups. An especially noteworthy characteristic of the groups is their extended luminous halos. The halo of VV 172 cannot be explained by the overlapping envelopes of galaxies with normal luminosity profiles, and the high redshift spiral galaxy in the Sextet is found to have an asymmetric internal structure and associated filament which suggest gravitational perturbation by the other members of the group.
It is pointed out that a determination of the reddening caused by intervening dust is a prerequisite to understanding the astrophysics of the broad line emission in quasars and their close cousins Seyfert 1 galaxies. Previous discussions of the reddening question have tended to be incomplete. The present investigation represents an attempt to asses critically the various techniques used to measure the reddening to quasars. It is found that if certain arguments presented are correct, there are no useful reddening indicators for the broad lines of quasars and Seyfert 1 galaxies. It seems safest to assume that reddening due to dust associated with quasars is negligible. However, small amounts of reddening toward quasars are certainly possible, and large amounts of reddening, while unlikely, cannot be ruled out.
Strong variable X-ray emission from the nearby low luminosity Seyfert 1 galaxy NGC 4051 was discovered during observations with the imaging proportional counter of the Einstein Observatory. During one 2304 second observation, the X-ray flux more than doubled in an approximately linear fashion, and a 70 percent increase for 150 seconds was seen during another 968 second observation. Evidence is presented which demonstrates that the X-ray spectrum of NGC 4051 is unusually soft compared to Seyfert 1 galaxies or QSOs. The emission mechanism is probably not synchrotron or synchrotron self-Compton, but the emission can be plausibly explained by various black hole accretion models. Previously announced in STAR as N83-23265
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.
Baldwin (1977) has inferred that the Ly-alpha/H-alpha line ratio in quasars was a factor of 10 lower than predicted by case B recombination theory, and direct observations of the Ly-alpha line in low-redshift quasars and Seyfert galaxies and of the Balmer lines in high-redshift quasars have confirmed this discrepancy. The present investigation is concerned with the Ly-alpha/H-alpha and Fe II/H-beta line ratios of a larger sample of quasars and Seyfert galaxies, taking into account the possibility of X-ray heating. Attention is given to details regarding the data set and to tests of X-ray heating in the broad-line region. The significance of the tests for the predictions of a model considered by Kwan and Krolik (1981) is evaluated.
The photon spectra of two Seyfert galaxies NGC 4151 and MCG 8-11-11 are good experimentally established in the X-ray and gamma range. The annihilation of the high temperature positrons with cold electrons is proposed as the possible mechanism of photon production in the Seyfert galaxy NGC 4151. The photon spectrum of NGC 4151 with its observed features from the soft X to the gamma ray range is described by annihilation of positrons and electrons at temperatures 3 x 10 to the 12th power K and 10 to the 8th power K respectively. The photon spectra from annihilation of unthermalized plasma with above parameters should be shifted to the lower energy by redshift z = 100. In that case the source of photons should be placed closely to the black hole horizon (r approximately equal to 1.0001 r sub g.
VLA high resolution observations of the Seyfert 1.5 galaxy MCG 8-11-11 at 2 and 6 cm show the center of the galaxy to contain a triple radio source of 400 pc, with a less than 30-pc diameter central component that may be identified as the center of the galaxy. The triple source is in turn embedded in more diffuse emission which has a major axis position angle similar to that in the optical galaxy, but differing from the position angle of the triple source by 50 deg. While the overall morphology of the source is S-shaped, the curvature of the triple source at the ends is abrupt rather than continuous and gradual. It appears that the core radio emission in Seyfert 1 and 1.5 galaxies may be weakly correlated with their X-ray emission.
Possible models are discussed in which the radio emitting components in Seyfert II nuclei can compress and accelerate the ambient nuclear medium to produce the characteristics of the narrow line region. A first order model, which considers only the expansion of the radio components, is briefly described. However, in many Seyfert nuclei it appears that the linear motion of the radio components is also important. This can result in shock heating of the ambient medium, and if the cooling time is long enough, can lead to a displacement between the radio component and the associated emission lines. This effect may be present in NGC 1068 and NGC 5929 and by considering ram pressure balance and the cooling length it is possible to estimate lobe velocities and ambient densities.
Einstein X-ray observations of optically selected radio-quiet quasars are presented (summarizing the report of Kriss and Canizares, 1985) and analyzed along with published data. The data set comprises 77 quasars (including nine new high-red-shift quasars) and Seyferts and 101 upper limits. The ratio of X-ray to optical luminosity in the quasars is found to decrease as optical luminosity increases and to depend only weakly on red shift, and statistical discrepancies between the optically selected sample and the X-ray-selected Medium Sensitivity Survey (Gioia et al., 1984) are discussed. Also included are analyses of X-ray spectra and short-timescale variability for 64 Seyfert galaxies: variability is detected in IIIZw2, Mkn 766, and Mkn 78.
The warm electron scattering region posited in 1985 by Antonucci and Miller to exist in NGC 1068 may be a characteristic feature of Seyfert galaxies. Whenever it exists, it presents a unique signature in Fe X-ray features. Predictions of the strength of the Fe K-edge and K-alpha line in both type 1 and type 2 Seyfert galaxies are presented and interpreted.
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.
Direct imaging and long-slit spectroscopic mapping of the emission-line gas in the Seyfert 2 galaxy 0714 - 2914 (M4-1, MCG - 5-18-2) are reported. The nuclear regions contain an extended (1 kpc size), high-excitation nebulosity that is well aligned with the jet-like nonthermal radio source. The profiles of Forbidden O III 5007A are asymmetric, with extended red wings to the north and west of the nucleus and extended blue wings to the south and east. This switch in the sense of asymmetry is accounted for in terms of a combination of normal rotational motions in the galaxy disk and high-velocity outflow or infall associated with the Seyfert activity.
Calculations are presented describing the ionization, chemical, and thermal state of molecular material in the obscuring tori close to the nuclei of many Seyfert galaxies. These are unusual molecular clouds: their electron fractions are about .001 and their temperatures are about 1000 K. Cooling is accomplished primarily by radiation of NIR H2 lines and FIR CO lines. High-J (C-12)(O-16) rotational lines should eventually be detectable from the nearer Seyfert galaxies. Medium-J lines due to (C-13)(O-16) and (C-12)(O-18) as well as (C-12)(O-16) should also be strong. Because ordinary molecular clouds are weak in these lines, the nuclear CO emissions can be distinguished from CO emission farther out in the host galaxy's disk.
The CO (J = 1-0) emission of three Seyfert galaxies, NGC 3227, NGC 7469, and NGC 5033 was imaged. The CO emission in NGC 3227 and NGC 7469 appears as compact structures centered on the active nuclei, containing substantial fractions of the single-dish flux. In NGC 3227, 10 percent of the CO flux detected by the interferometer is contained within the ionized narrow-line region. The unresolved molecular gas concentrations in the nucleus of NGC 3227 imply a CO mass of 65 million solar masses concentrated within a diameter less than 50 pc. The CO emission in NGC 5033 is not detected at this resolution, implying a CO structure size of 20 to 60 arcsec. Continuum emission at 2.7 mm is not detected in any of the three galaxies. In the center of NGC 7469, the H2 mass is comparable to the dynamical mass. Kinematic studies of the detected gas reveal a rotational motion of the gas in NGC 3227 and NGC 7469, allowing identification of the gas in NGC 7469 with a nuclear starburst. These data are consistent with the idea that interactions between galaxies cause gas to concentrate in their nuclei thereby feeding starburst and Seyfert activity.