Far-infrared properties of optically-selected quasars and Seyfert galaxies

Pointed IRAS observations and ground based observations are used to determine the infrared properties of optically selected galaxies and quasars. The use of complete, unbiased, optically selected samples means that statistical tests can be applied to probe the underlying properties of active galactic nuclei (AGNs). The near infrared to millimeter spectral energy distributions (SEDs) were studied of the CfA Seyfert galaxies, a well defined, unbiased sample of 25 Type 1 and 23 Type 2 Seyfert galaxies selected by optical spectroscopy. Data given show strong trends in the infrared SEDs. Strong evidence is also given that the infrared spectra of Seyfert 2 galaxies are dominated by thermal emission from warm dust, while nonthermal emission is more important in the spectra of quasars and luminous Seyfert 1 nuclei

On the relation between the IR continuum and the active galactic nucleus in Seyfert galaxies

A sample of the brightest known Seyfert galaxies from the CfA sample is analyzed on the basis of ISO photometric and spectroscopic data. Regardless of the Seyfert type, the mid-IR continuum emission from these galaxies is found to be correlated with the coronal line emission arising in the nuclear active region. Conversely, the correlation degrades progressively when moving from the mid- to the far-IR emission, where it ends to vanish. It is concluded that the mid-IR emission is largely dominated by dust heated by processes associated with the active nucleus whereas the far-IR is a different component most probably unrelated with the active region. We suggest that the far-IR component is due to dust heated by the stellar population in the disks of these galaxies.Comment: 6 pages, 3 figures To be published in Astronomy and Astrophysic

The X-Ray Spectral Variability of Mrk 766

Analysis results from ASCA and ROSAT observations of the narrow-line Seyfert 1 galaxy Mrk 766 are reported. In the ASCA observation we observed rapid variability with a doubling time scale of 1000 seconds. A spectral variability event was observed in which the spectrum softened and hardened above and below ~1 keV, respectively, as the flux increased. The spectra could be modeled with 5 components: a power law, warm absorber, iron K(alpha) line and soft excess component flux. The spectral variability resulted from a highly significant change in the intrinsic photon law index from Gamma ~1.6 to ~2.0, an increase in the warm absorber ionization, and a marginally significant decrease in the soft component normalization. A ~100 eV equivalent width narrow iron K(alpha) line was detected in the high state spectrum. Spectral hardening during flux increases was observed in three ROSAT observations. The change in intrinsic photon index and disappearance of the soft excess component in the ASCA spectra can be explained as a transition from a first order pair reprocessed spectrum to a pair cascade brought about by a sudden increase in the injected electron Lorentz factor. The change in the ionization of the warm absorber, though model dependent, could correspond to the increase in flux at the oxygen edges resulting from the spectral index change. The ROSAT spectral variability can be interpreted by variable intensity hard power law and a relatively nonvarying soft component, possibly primary disk emission. These results are compared with those reported from other narrow-line Seyfert 1 galaxies.Comment: 29 pages using (AASTeX) aaspp4.sty and 18 Postscript figures. To appear in the September 1, 1996, issue of The Astrophysical Journa

Potential for cogeneration of heat and electricity in California industry, phase 2

The nontechnical issues of industrial cogeneration for 12 California firms were analyzed under three categories of institutional settings: (1) industrial ownership without firm sales of power; (2) industrial ownership with firm sales of power; and (3) utility or third party ownership. Institutional issues were analyzed from the independent viewpoints of the primary parties of interest: the industrial firms, the electric utilities and the California Public utilities Commission. Air quality regulations and the agencies responsible for their promulgation were examined, and a life cycle costing model was used to evaluate the economic merits of representative conceptual cogeneration systems at these sites. Specific recommendations were made for mitigating measures and regulatory action relevant to industrial cogeneration in California

Simultaneous EUV and X-ray variability of NGC 4051

We present a flux variability study of simultaneous RXTE and EUVE observations of the highly variable Seyfert galaxy NGC4051. We find a strong correlation between variability in the EUV and medium energy X-ray bands,indicating that both are sampling the same power-law continuum. The lag between the two bands is less than 20 ks and, depending on model assumptions, may be <1 ks. We examine the consequences of such a small lag in the context of simple Comptonisation models for the production of the power-law continuum. A lag of <1 ks implies that the size of the Comptonising region is less than 20 Schwarzschild radii for a black hole of mass >1E6 solar masses.Comment: 8 pages, accepted for publication in MNRA

Complex X-ray spectral variability in Mkn 421 observed with XMM-Newton

The bright blazar Mkn 421 has been observed four times for uninterrupted durations of ~ 9 - 13 hr during the performance verification and calibration phases of the XMM-Newton mission. The source was strongly variable in all epochs, with variability amplitudes that generally increased to higher energy bands. Although the detailed relationship between soft (0.1 - 0.75 keV) and hard (2 - 10 keV) band differed from one epoch to the next, in no case was there any evidence for a measurable interband lag, with robust upper limits of $| \tau | < 0.08$ hr in the best-correlated light curves. This is in conflict with previous claims of both hard and soft lags of ~1 hr in this and other blazars. However, previous observations suffered a repeated 1.6 hr feature induced by the low-Earth orbital period, a feature that is not present in the uninterrupted XMM-Newton data. The new upper limit on $|\tau|$ leads to a lower limit on the magnetic field strength and Doppler factor of B \delta^{1/3} \gs 4.7 G, mildly out of line with the predictions from a variety of homogeneous synchrotron self-Compton emission models in the literature of $B \delta^{1/3} = 0.2 - 0.8$ G. Time-dependent spectral fitting was performed on all epochs, and no detectable spectral hysteresis was seen. We note however that the source exhibited significantly different spectral evolutionary behavior from one epoch to the next, with the strongest correlations in the first and last and an actual divergance between soft and hard X-ray bands in the third. This indicates that the range of spectral variability behavior in Mkn 421 is not fully described in these short snippets; significantly longer uninterrupted light curves are required, and can be obtained with XMM-Newton.Comment: 21 pages, 4 figures, accepted for ApJ, scheduled for August 1, 200

On the relation between the coronal line emission and the IR/X-ray emission in Seyfert galaxies

The relation between the X-ray, the coronal line and the infrared (IR) emissions in a sample of the brightest known Seyfert galaxies is analysed. A close relationship between the absorption-corrected soft X-ray emission and both the mid-IR and the coronal line emission is found for the Seyfert type 2 objects in the sample. The coronal line and the X-ray emissions are both main tracers of the central activity, hence their relationship with the mid-IR emission points to nuclear energetic process as the main responsibles of the heating of the circumnuclear dust. On the other hand, the above relations do not seem to hold for the Seyfert type 1 discussed in the sample, at least when the comparisons are done in a flux diagram. This is partially because of the reduced number of objects of this type analysed in this work and the fact that the measured soft X-ray emission in Seyfert 1s is systematically larger, by at least an order of magnitude, than that in the Seyfert 2 counterparts. Finally, the hard X-ray emission in the studied sample appears unrelated to either the mid-IR or the coronal line emission.Comment: 14 pages, 3 figures To be published in MNRAS (accepted