arXiv subjects

M. Calvani

Publications and source records attributed to M. Calvani.

25 records · Page 2Linked to original sources

arXiv2002

Average Quasar Spectra in the Context of Eigenvector 1

[LaTeX removed] Recent work has shown that it is possible to systematize quasar spectral diversity in a parameter space called ``Eigenvector 1'' (E1). We present median AGN spectra for fixed regions of the E1 (optical) parameter space (FWHM(H-beta) vs. equivalent width ratio RFE=W(FeII4570)/W(H-beta). Comparison of the median spectra for different regions show considerable differences. We suggest that an E1-driven approach to median/average spectra emphasizes significant differences between AGN, and offers more insights into AGN physics and dynamics than a single population median/average derived from a large and heterogeneous sample of sources. We find that the H-beta broad component line profile changes in shape along the E1 sequence both in average centroid shift and asymmetry. While objects with FWHM(H-beta)< 4000 km/s are well fitted by a Lorentz function, AGN with FWHM(H-beta)> 4000 km/s are well fitted if two broad line components are used: a broad (the "classical" broad line component) and a very broad/redshifted component.

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arXiv2001

Searching for the Physical Drivers of the Eigenvector 1 Correlation Space

[Latex markup removed] We recently discussed an Eigenvector 1 (E1) parameter space that provides optimal discrimination between the principal classes of broad-line Active Galactic Nuclei (AGN). In this paper we begin a search for the most important physical parameters that are likely to govern correlations and data point distribution in E1 space. We focus on the principal optical parameter plane involving the width of the H-beta broad component and the equivalent width ratio between the FeII blend at 4570 A and H-beta broad component. We show that the observed correlation for radio-quiet sources can be accounted for if it is primarily driven by the ratio of AGN luminosity to black hole mass (L/M proportional to Eddington ratio) convolved with source orientation. L/M apparently drives the radio-quiet correlation only for FWHM(H-beta) < 4000 km/s which includes Narrow Line Seyfert 1 (NLSy1) galaxies and can be said to define an AGN ``main sequence.'' Source orientation plays an increasingly important role as FWHM(H-beta) increases. We also argue that AGN lying outside the radio-quiet ``main sequence,'' and specifically those with optical FeII much stronger than expected for a given FWHM(H-beta), may all be Broad Absorption Line QSOs.

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arXiv1998

Disk Models for MCG-06-30-15: The Variability Challenge

Recent observations have shown that the Fe Kalpha line profile of the Seyfert~1 galaxy MCG-06-30-15 is strongly variable. We attempt accretion disk model fits to the Fa Kalpha line profiles in a high, low and medium continuum luminosity phase of this source. During the monitoring by Iwasawa et al. (1996) a broad red-shifted component remained reasonably constant while a narrower component at $\approx$ 6.4 keV strongly responded to continuum changes. Physically consistent fits are possible if the index xi of the power-law emissivity changes from 0.7 (high phase) to 3.0 (low phase). The shape of the red-shifted component at low phase is crucial to the disk model interpretation. We suggest that the actual shape may be a broad redshifted Gaussian. Three lines of evidence support the interpretation of the Fe Kalpha line as multicomponent, beyond the lack of correlation in the response to continuum changes of the red and blue components in MCG -06-30-15. (1) We show that the strong concentration of narrow peak centroids at 6.4 keV is inconsistent with expectations of a random distribution of disk orientations. (2) The average Fe Kalpha profile for a sample of 16 mostly Seyfert~1's suggests a natural decomposition into two Gaussians one unshifted/narrow and the other redshifted/broad. (3) Evidence for emission in excess to the expectation of disk models on the high energy side of the Fe Kalpha profile is both a challenge for low inclination disk models and support for the two component decomposition.

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arXiv1997

On the Origin of Broad Fe K alpha and Hi H alpha Lines in AGN

We examine the properties of the Fe emission lines that arise near 6.4 keV in the ASCA spectra of AGN. Our emphasis is on the Seyfert 1 galaxies where broad and apparently complex Fe K alpha emission is observed. We consider various origins for the line but focus on the pros and cons for line emitting accretion disk models. We develop a simple model of an illuminated disk capable of producing both X-ray and optical lines from a disk. The model is able to reproduce the observed Fe K alpha FWHM ratio as well as the radii of maximum emissivity implied by the profile redshifts. The overall profile shapes however do not fit well the predictions of our disk illumination model nor do we derive always consistent disk inclinations for the two lines. We conclude that the evidence for and against an accretion disk origin for the Fe K alpha emission is equal at best. The bulk of the data requires a very disparate set of line fits which shed little light on a coherent physical model. We briefly consider alternatives to disk emission models and show that a simple bicone model can reproduce the FE line profiles equally well.

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arXiv1996

On the Difference Between Radio Quiet and Radio Loud AGN

A systematic difference in alignment between the central black hole spin and the angular momentum of the accreting gas may help explain several differences found in the optical and UV HST spectra of radio loud and radio quiet AGN.

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arXiv1994

Pictor A: A New Double-Peaked Emission Line Quasar

We obtained a new spectrum for the radio galaxy Pictor~A in December 1993. Comparison with previous data obtained in 1983 and 1987 shows that the broad component of the Balmer lines has increased considerably in strength and complexity. The Balmer lines now show a boxy, double peaked profile with FWZI$\sim$24000 \kms. Although the 1993 H\a\ profile is reminiscent of Arp~102B, accretion disk models face immediate difficulty because (1) the redshifted peak in the profile is considerably stronger than the blue one, and (2) the red and blue peaks varied at different epochs. The latter finding strongly favors a predominance of radial motion. We argue that Pictor~A, and the rare objects with similar extremely broad emission line profiles, are better understood if the orientation is such that the gas is predominantly moving along the line of sight (i.e.\ a geometrical extremum).

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arXiv1993

The Peculiar Balmer Line Profiles of OQ 208

We present spectrophotometric observations of the Broad Line Radio Galaxy OQ 208 (Mrk 668, 1404+286) obtained between 1985 and 1991. We show that the Balmer line fluxes and profile shapes undergo remarkable changes. The ratio of intensities between the broad and narrow components of Hbeta increased monotonically from 15 in 1985 to 40 in 1991. The peak of the broad components of Hbeta and Halpha were known to be strongly displaced to the red. We have discovered a correlation between the amplitude of the broad peak displacement and the luminosity of Hbeta, in the sense that the displacement is larger when the line luminosity is higher. We suggest that the observations are not compatible with either a binary Broad Line Region model or one involving ballistic acceleration of the line emitting gas. Radiative acceleration of a system of outflowing clouds readily explains the correlation between line shift and luminosity as well as the peculiar line profiles. Furthermore, it seems that most or all of the Balmer emission originates from the inward face of the clouds. Theoretical line profiles suggest that the observed Hbeta profile is best fit assuming the contribution of an ensemble which might be spherical or confined in a thick disk in addition to a component emitted in a thin shell contained in a cone of half opening angle 12 degrees seen along its axis.

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