4 research outputs found
1.4 GHz on the Fundamental Plane of Black Hole Activity
The fundamental plane of black hole activity is an empirical relationship
between the OIII/X-ray luminosity depicting the accretion power, the radio
luminosity as a probe of the instantaneous jet power and the mass of the black
hole. For the first time, we use the 1.4 GHz FIRST radio luminosities on the
optical fundamental plane, to investigate whether or not FIRST fluxes can trace
nuclear activity. We use a SDSS-FIRST cross-correlated sample of 10149 active
galaxies and analyse their positioning on the optical fundamental plane. We
focus on various reasons that can cause the discrepancy between the observed
FIRST radio fluxes and the theoretically expected core radio fluxes, and show
that that FIRST fluxes are heavily contaminated by non-nuclear, extended
components and other environmental factors. We show that the subsample of
'compact sources', which should have negligible lobe contribution,
statistically follow the fundamental plane when corrected for relativistic
beaming, while all the other sources lie above the plane. The sample of LINERs,
which should have negligible lobe and beaming contribution, also follow the
fundamental plane. A combined fit of the low-luminosity AGN and the X-ray
binaries, with the LINERs, results in the relation log L = 0.77 log
L + 0.69 log M. Assuming that the original fundamental plane relation
is correct, we conclude that 1.4 GHz FIRST fluxes do not trace the pure 'core'
jet and instantaneous nuclear activity in the AGN, and one needs to be careful
while using it on the fundamental plane of black hole activity.Comment: 10 pages, 5 figures, accepted for publication by MNRA
Using infrared/X-ray flare statistics to probe the emission regions near the event horizon of Sgr A*
The supermassive black hole at the centre of the Galaxy flares at least daily
in the infrared (IR) and X-ray bands, yet the process driving these flares is
still unknown. So far detailed analysis has only been performed on a few bright
flares. In particular, the broadband spectral modelling suffers from a strong
lack of simultaneous data. However, new monitoring campaigns now provide data
on thousands of flaring events, allowing a statistical analysis of the flare
properties. In this paper, we investigate the X-ray and IR flux distributions
of the flare events. Using a self-consistent calculation of the particle
distribution, we model the statistical properties of the flares. Based on a
previous work on single flares, we consider two families of models: pure
synchrotron models and synchrotron self-Compton (SSC) models. We investigate
the effect of fluctuations in some relevant parameters (e.g. acceleration
properties, density, magnetic field) on the flux distributions. The
distribution of these parameters is readily derived from the flux distributions
observed at different wavelengths. In both scenarios, we find that fluctuations
of the power injected in accelerated particles plays a major role. This must be
distributed as a power-law (with different indices in each model). In the
synchrotron dominated scenario, we derive the most extreme values of the
acceleration power required to reproduce the brightest flares. In that model,
the distribution of the acceleration slope fluctuations is constrained and in
the SSC scenario we constrain the distributions of the correlated magnetic
field and flow density variations.Comment: 9 pages, 3 tables, 6 figures, MNRAS, June 201