On Core Collapse Supernovae in Normal and in Seyfert Galaxies

This paper estimates the relative frequency of different types of core-collapse supernovae, in terms of the ratio f between the number of type Ib--Ic and of type II supernovae. We estimate f independently for all normal and Seyfert galaxies whose radial velocity is <=14000 km/s, and which had at least one supernova event recorded in the Asiago catalogue from January 1986 to August 2000. We find that the ratio f is approx. 0.23+/-0.05 in normal galaxies. This value is consistent with constant star formation rate and with a Salpeter Initial Mass Function and average binary rate approx. 50 %. On the contrary, Seyfert galaxies exceed the ratio f in normal galaxies by a factor approx. 4 at a confidence level >= 2 sigma. A caveat is that the numbers for Seyferts are still small (6 type Ib-Ic and 6 type II supernovae discovered as yet). Assumed real, this excess of type Ib and Ic with respect to type II supernovae, may indicate a burst of star formation of young age (<= 20 Myr), a high incidence of binary systems in the inner regions (r <= 0.4 R25) of Seyfert galaxies, or a top-loaded mass function.Comment: Accepted for Publication in MNRA

3C 57 as an Atypical Radio-Loud Quasar: Implications for the Radio-Loud/Radio-Quiet Dichotomy

Lobe-dominated radio-loud (LD RL) quasars occupy a restricted domain in the 4D Eigenvector 1 (4DE1) parameter space which implies restricted geometry/physics/kinematics for this subclass compared to the radio-quiet (RQ) majority of quasars. We discuss how this restricted domain for the LD RL parent population supports the notion for a RQ-RL dichotomy among Type 1 sources. 3C 57 is an atypical RL quasar that shows both uncertain radio morphology and falls in a region of 4DE1 space where RL quasars are rare. We present new radio flux and optical spectroscopic measures designed to verify its atypical optical/UV spectroscopic behaviour and clarify its radio structure. The former data confirms that 3C 57 falls off the 4DE1 quasar "main sequence" with both extreme optical FeII emission (R_{FeII} ~ 1) and a large CIV 1549 profile blueshift (~ -1500 km/s). These parameter values are typical of extreme Population A sources which are almost always RQ. New radio measures show no evidence for flux change over a 50+ year timescale consistent with compact steep-spectrum (CSS or young LD) over core-dominated morphology. In the 4DE1 context where LD RL are usually low L/L_{Edd} quasars we suggest that 3C 57 is an evolved RL quasar (i.e. large Black Hole mass) undergoing a major accretion event leading to a rejuvenation reflected by strong FeII emission, perhaps indicating significant heavy metal enrichment, high bolometric luminosity for a low redshift source and resultant unusually high Eddington ratio giving rise to the atypical CIV 1549.Comment: Accepted for publication in MNRAS; 10 pages, 6 figures, 4 table

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.Comment: 28 pages + tables and figures available upon request, Latex, No preprint numbe

Fifty Years of Quasars: Physical Insights and Potential for Cosmology

Last year (2013) was more or less the 50th anniversary of the discovery of quasars. It is an interesting time to review what we know (and don't know) about them both empirically and theoretically. These compact sources involving line emitting plasma show extraordinary luminosities extending to one thousand times that of our Milky Way in emitting volumes of a few solar system diameters (bolometric luminosity log L$_{bol} \sim$ 44-48 [erg s$^{-1}$]: D=1-3 light months $\sim$ $10^3$ - $10^4$ gravitational radii). The advent of 8-10 meter class telescopes enables us to study them spectroscopically in ever greater detail. In 2000 we introduced a 4D Eigenvector 1 parameters space involving optical, UV and X-Ray measures designed to serve as a 4D equivalent of the 2D Hertzsprung-Russell diagram so important for depicting the diversity of stellar types and evolutionary states. This diagram has revealed a principal sequence of quasars distinguished by Eddington ratio (proportional to the accretion rate per unit mass). Thus while stellar differences are primarily driven by the mass of a star, quasar differences are apparently driven by the ratio of luminosity-to-mass. Out of this work has emerged the concept of two quasars populations A and B separated at Eddington ratio around 0.2 which maximizes quasar multispectral differences. The mysterious 8% of quasars that are radio-loud belong to population B which are the lowest accretors with the largest black hole masses. Finally we consider the most extreme population A quasars which are the highest accretors and in some cases are among the youngest quasars. We describe how these sources might be exploited as standard candles for cosmology.Comment: Accepted for publication in Journal of Physics Conference Series (10 pages, 4 figures). Invited Lecture at International Symposium on the Physics of Ionized Gas (SPIG 2014), Belgrade 26-29 August 201

Blue outliers among intermediate redshift quasars

[Oiii]{\lambda}{\lambda}4959,5007 "blue outliers" -- that are suggestive of outflows in the narrow line region of quasars -- appear to be much more common at intermediate z (high luminosity) than at low z. About 40% of quasars in a Hamburg ESO intermediate-z sample of 52 sources qualify as blue outliers (i.e., quasars with [OIII] {\lambda}{\lambda}4959,5007 lines showing large systematic blueshifts with respect to rest frame). We discuss major findings on what has become an intriguing field in active galactic nuclei research and stress the relevance of blue outliers to feedback and host galaxy evolution.Comment: Accepted for publication in Astrophysics and Space Science, Special Issue on Line Shifts in Astrophysics and Laboratory Plasm