1,109 research outputs found
On the AGN radio luminosity distribution and the black hole fundamental plane
We have studied the dependence of the AGN nuclear radio (1.4 GHz) luminosity
on both the AGN 2-10 keV X-ray and the host-galaxy K-band luminosity. A
complete sample of 1268 X-ray selected AGN (both type 1 and type 2) has been
used, which is the largest catalogue of AGN belonging to statistically well
defined samples where radio, X and K band information exists. At variance with
previous studies, radio upper limits have been statistically taken into account
using a Bayesian Maximum Likelihood fitting method. It resulted that a good fit
is obtained assuming a plane in the 3D L_R-L_X-L_K space, namely logL_R= xi_X
logL_X + xi_K logL_K + xi_0, having a ~1 dex wide (1 sigma) spread in radio
luminosity. As already shown, no evidence of bimodality in the radio luminosity
distribution was found and therefore any definition of radio loudness in AGN is
arbitrary. Using scaling relations between the BH mass and the host galaxy
K-band luminosity, we have also derived a new estimate of the BH fundamental
plane (in the L_5GHz -L_X-M_BH space). Our analysis shows that previous
measures of the BH fundamental plane are biased by ~0.8 dex in favor of the
most luminous radio sources. Therefore, many AGN studies, where the BH
fundamental plane is used to investigate how AGN regulate their radiative and
mechanical luminosity as a function of the accretion rate, or many AGN/galaxy
co-evolution models, where radio-feedback is computed using the AGN fundamental
plane, should revise their conclusions.Comment: Submitted to MNRAS. Revised version after minor referee comments. 12
pages, 12 figure
A full descriptive definition of the BV-integral
summary:We present a Cauchy test for the almost derivability of additive functions of bounded BV sets. The test yields a full descriptive definition of a coordinate free Riemann type integral
Analysis of the Parameters Affecting the Stiffness of Short Sisal Fiber Biocomposites Manufactured by Compression-Molding
The use of natural fiber-based composites is on the rise in many industries. Thanks to their eco-sustainability, these innovative materials make it possible to adapt the production of components, systems and machines to the increasingly stringent regulations on environmental protection, while at the same time reducing production costs, weight and operating costs. Optimizing the mechanical properties of biocomposites is an important goal of applied research. In this work, using a new numerical approach, the effects of the volume fraction, average length, distribution of orientation and curvature of fibers on the Young’s modulus of a biocomposite reinforced with short natural fibers were studied. Although the proposed approach could be applied to any biocomposite, sisal fibers and an eco-sustainable thermosetting matrix (green epoxy) were considered in both simulations and the associated experimental assessment. The results of the simulations showed the following effects of the aforementioned parameters on Young’s modulus: a linear growth with the volume fraction, nonlinear growth as the length of the fibers increased, a reduction as the average curvature increased and an increase in stiffness in the x-y plane as the distribution of fiber orientation in the z direction decreased
The rest-frame UV-to-optical spectroscopy of APM 08279+5255 - BAL classification and black hole mass estimates
We present the analysis of the rest-frame optical-to-UV spectrum of APM
08279+5255, a well-known lensed broad absorption line (BAL) quasar at . The spectroscopic data are taken with the optical DOLoRes and near-IR
NICS instruments at TNG, and include the previously unexplored range between C
III] 1910 and [O III] 4959,5007. We investigate the
possible presence of multiple BALs by computing "balnicity" and absorption
indexes (i.e. BI, BI and AI) for the transitions Si IV 1400, C IV
1549, Al III 1860 and Mg II 2800. No clear evidence
for the presence of absorption features is found in addition to the already
known, prominent BAL associated to C IV, which supports a high-ionization BAL
classification for APM 08279+5255. We also study the properties of the [O III],
H and Mg II emission lines. We find that [O III] is intrinsically weak
(), as it is typically found in
luminous quasars with a strongly blueshifted C IV emission line (2500 km
s for APM 08279+5255). We compute the single-epoch black hole mass based
on Mg II and H broad emission lines, finding M, with the magnification factor that can
vary between 4 and 100 according to CO and rest-frame UV-to-mid-IR imaging
respectively. Using a Mg II equivalent width (EW)-to-Eddington ratio relation,
the EW \AA\ measured for APM 08279+5255 translates into an
Eddington ratio of 0.4, which is more consistent with . This
magnification factor also provides a value of that is consistent
with recent reverberation-mapping measurements derived from C IV and Si IV.Comment: 10 pages, 4 figures, 4 tables, accepted for publication in A&
Canaryseed (Phalaris canariensis L.) accessions from nineteen countries show useful genetic variation for agronomic traits
Fifty-seven accessions of canaryseed (47 populations and 10 cultivars) from 19 countries were evaluated for agronomic traits in four field trials sown over 3 yr in the province of Buenos Aires, Argentina. Genetic variation was found for all traits scored: grain yield and its components (grain weight, grain number per square meter, grain number per head and head number per square meter), harvest index, percent lodging, and phenological characters (emergence to heading, emergence to harvest maturity and heading to harvest maturity). Although genotype×environment interaction was observed for all traits, the additive differences between accessions were sufficient to enable promising breeding materials to be identified. Accessions superior in performance to the local Argentinean population, which in general gave values close to the overall mean of the accessions evaluated, were identified. For example, a population of Moroccan origin gave good yield associated with elevated values of the highly heritable character grain weight, rather than with the more commonly observed grain number per square meter. This population was also of relatively short stature and resistant to lodging, and, although it performed best when sown within the normal sowing date, tolerated late sowing fairly well. Other accessions were also observed with high grain weight, a useful characteristic in itself, since large grains are desirable from a quality point of view. Regarding phenology,
the accessions showed a range of 160 degree days (8 calendar days in our conditions) in maturity, which, while not large in magnitude, may be of some utility in crop rotation management. Some accessions were well adapted to late sowing. Grain yield in general was strongly correlated with grain number per square meter. Principal components analysis (PCA) carried out for all characteristics provided indications of accessions combining useful characteristics and identified three components that explained approximately 70% of the phenotypic variation. Furthermore, a second PCA plus regression showed that approximately 60% of the variation in grain yield could be explained by a component associated with harvest index and grain number per square meter. Pointers were provided to possible future breeding targets
The WISSH quasars Project: II. Giant star nurseries in hyper-luminous quasars
Studying the coupling between the energy output produced by the central
quasar and the host galaxy is fundamental to fully understand galaxy evolution.
Quasar feedback is indeed supposed to dramatically affect the galaxy properties
by depositing large amounts of energy and momentum into the ISM. In order to
gain further insights on this process, we study the SEDs of sources at the
brightest end of the quasar luminosity function, for which the feedback
mechanism is supposed to be at its maximum. We model the rest-frame UV-to-FIR
SEDs of 16 WISE-SDSS Selected Hyper-luminous (WISSH) quasars at 1.8 < z < 4.6
disentangling the different emission components and deriving physical
parameters of both the nuclear component and the host galaxy. We also use a
radiative transfer code to account for the contribution of the quasar-related
emission to the FIR fluxes. Most SEDs are well described by a standard
combination of accretion disk+torus and cold dust emission. However, about 30%
of them require an additional emission component in the NIR, with temperatures
peaking at 750K, which indicates the presence of a hotter dust component in
these powerful quasars. We measure extreme values of both AGN bolometric
luminosity (LBOL > 10^47 erg/s) and SFR (up to 2000 Msun/yr). A new relation
between quasar and star-formation luminosity is derived (LSF propto
LQSO^(0.73)) by combining several Herschel-detected quasar samples from z=0 to
4. Future observations will be crucial to measure the molecular gas content in
these systems, probe the impact between quasar-driven outflows and on-going
star-formation, and reveal the presence of merger signatures in their host
galaxies.Comment: 19 pages, 12 figures; Accepted for publication in Astronomy &
Astrophysics on June 13, 201
Physical properties of AGN host galaxies as a probe of SMBH feeding mechanisms
Using an advanced semi analytic model (SAM) for galaxy formation, we have
investigated the statistical effects of assuming two different mechanisms for
triggering AGN activity on the properties of AGN host galaxies. We have
considered a first accretion mode where AGN activity is triggered by disk
instabilities (DI) in isolated galaxies, and a second feeding mode where such
an activity is triggered by galaxy mergers and fly-by events (interactions,
IT). We obtained the following results:i) for hosts with , both DI and IT modes are able to account for the observed AGN
hosts stellar mass function; for more massive hosts, the DI scenario predicts a
lower space density than the IT model, lying below the observational estimates
for z>0.8.ii) The analysis of the color-magnitude diagram (CMD) of AGN hosts
for redshift z < 1.5 can provide a good observational test to effectively
discriminate between the DI and IT mode, since DIs are expected to yield AGN
host galaxy colors skewed towards bluer colors, while in the IT scenario the
majority of hosts are expected to reside in the red sequence.iii) While both IT
and DI scenarios can account for AGN triggered in main sequence or starburst
galaxies, DIs fail in triggering AGN activity in passive galaxies.iv) The two
modes are characterized by a different duration of the AGN phase, with DIs
lasting even on time scales Gyr, much longer with respect to the IT
scenario.v) The scatter of the relation could represent another
crucial diagnostics to discriminate between the two triggering modes, since the
DI scenario predicts an appreciably lower scatter of the relation than the IT
scenario. vi) Disk instabilities are not able to account for the observed
fraction of AGN in groups for z < 1 and clusters for z < 0.7, while the IT
scenario provides a good match to observational data.Comment: Paper accepted for publication in section 4. Extragalactic astronomy
of Astronomy and Astrophysic
Blowin' in the wind: both `negative' and `positive' feedback in an obscured high-z Quasar
Quasar feedback in the form of powerful outflows is invoked as a key
mechanism to quench star formation in galaxies, preventing massive galaxies to
over-grow and producing the red colors of ellipticals. On the other hand, some
models are also requiring `positive' AGN feedback, inducing star formation in
the host galaxy through enhanced gas pressure in the interstellar medium.
However, finding observational evidence of the effects of both types of
feedback is still one of the main challenges of extragalactic astronomy, as few
observations of energetic and extended radiatively-driven winds are available.
Here we present SINFONI near infrared integral field spectroscopy of XID2028,
an obscured, radio-quiet z=1.59 QSO detected in the XMM-COSMOS survey, in which
we clearly resolve a fast (1500 km/s) and extended (up to 13 kpc from the black
hole) outflow in the [OIII] lines emitting gas, whose large velocity and
outflow rate are not sustainable by star formation only. The narrow component
of Ha emission and the rest frame U band flux from HST-ACS imaging enable to
map the current star formation in the host galaxy: both tracers independently
show that the outflow position lies in the center of an empty cavity surrounded
by star forming regions on its edge. The outflow is therefore removing the gas
from the host galaxy (`negative feedback'), but also triggering star formation
by outflow induced pressure at the edges (`positive feedback'). XID2028
represents the first example of a host galaxy showing both types of feedback
simultaneously at work.Comment: 9 pages, 5 figures, accepted for publication in Ap
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