We compute the non-thermal emissions produced by relativistic particles accelerated by the shocks driven by the active galactic nucleus (AGN) in NGC 1068, and we compare the model predictions with ...the observed γ-ray and radio spectra. The former is produced by pion decay, inverse Compton scattering, and bremsstrahlung, while the latter is produced by synchrotron radiation. We derive the γ-ray and radio emissions by assuming the standard acceleration theory, and we discuss how our results compare with those corresponding to other commonly assumed sources of γ-ray and radio emissions, like supernova remnants (SNR) or AGN jets. We find that the AGN-driven shocks observed in the circumnuclear molecular disk of NGC 1068 provide a contribution to the γ-ray emission comparable to that provided by the starburst activity when standard particle acceleration efficiencies are assumed, while the shocks can yield the whole γ-ray emission only when the parameters describing the acceleration efficiency and the proton coupling with the molecular gas are tuned to values larger than those assumed in standard, SNR-driven shocks. We discuss the range of acceleration efficiencies (for protons and electrons) and of proton calorimetric fractions required to account for the observed γ-ray emission in the AGN outflow model. We further compare the neutrino flux expected in our model with constraints from current experiments, and we provide predictions for the detections by the upcoming KM3NeT neutrino telescope. This analysis strongly motivates observations of NGC 1068 at ≳TeV energies with current and future Cherenkov telescopes in order to gain insight into the nature of the γ-rays source.
We derive the contribution to the extragalactic gamma-ray background (EGB) from active galactic nuclei (AGN) winds and star-forming galaxies by including a physical model for the γ-ray emission ...produced by relativistic protons accelerated by AGN-driven and supernova-driven shocks into a state-of-the-art semi-analytic model of galaxy formation. This is based on galaxy interactions as triggers of AGN accretion and starburst activity and on expanding blast waves as the mechanism to communicate outwards the energy injected into the interstellar medium by the active nucleus. We compare the model predictions with the latest measurement of the EGB spectrum performed by the Large Area Telescope (LAT) on board the Fermi Gamma-ray Space Telescope (Fermi) in the range between 100 MeV and 820 GeV. We find that AGN winds can provide ~35 ± 15% of the observed EGB in the energy interval Eγ = 0.1–1 GeV, for ~73 ± 15% at Eγ = 1–10 GeV, and for ~60 ± 20% at Eγ ≳10 GeV. The AGN wind contribution to the EGB is predicted to be larger by a factor of ~3–5 than that provided by star-forming galaxies (quiescent plus starburst) in the hierarchical clustering scenario. The cumulative γ-ray emission from AGN winds and blazars can account for the amplitude and spectral shape of the EGB, assuming the standard acceleration theory, and AGN wind parameters that agree with observations. We also compare the model prediction for the cumulative neutrino background from AGN winds with the most recent IceCube data. We find that for AGN winds with accelerated proton spectral index p = 2.2–2.3, and taking into account internal absorption of γ-rays, the Fermi-LAT and IceCube data could be reproduced simultaneously.
We have reanalyzed the giant outburst of the blazar PKS 1510−089 (z = 0.36) that occurred on 2011 October−November. The γ-ray flux in the 0.1−100 GeV energy range exceeded the value of 10-5 ph cm-2 ...s-1 for several days. The peak flux was reached on 2011 October 19, with a value of ~4.4 × 10-5 ph cm-2 s-1, which in turn corresponds to a luminosity of ~2 × 1049 erg s-1. A very short timescale variability was measured. Particularly on 2011 October 18, the flux-doubling time was as short as ~20 min. This is the shortest variability ever detected in the MeV-GeV energy band. We compared our analysis with two other outbursts observed in 2009 March and 2012 February−March, when the blazar was also detected by H.E.S.S. and MAGIC to infer information about the emission at hundreds of GeV.
The flat-spectrum radio quasar PKS 1222+216 (4C+21.35, z = 0.432) was detected in the very high energy γ-ray band by MAGIC during a highly active γ-ray phase following an alert by the Large Area ...Telescope (LAT) onboard Fermi. Its relatively hard spectrum (70–400 GeV photon index Γ = 2.7 ± 0.3) without a cut off, together with its observed variability on a timescale of ~10 min challenges standard emission models. In particular, if the emission originates in a portion of the relativistic jet located inside the broad line region (BLR), severe absorption of γ rays above a few tens of GeV is expected to be caused by the γγ → e ± process. These observations therefore imply that there is a very compact (Rb ~ 5 × 1014 cm) and rapidly moving blob located far beyond the BLR radius (to avoid the gamma-ray absorption through pair production) that is responsible for the rapidly varying high energy flux. However, the long-term (day-week) coherent evolution of the GeV flux recorded by LAT indicates that there could also be a substantial contribution from another, larger emission region. We model the spectral energy distribution of PKS 1222+216 during the epoch of the MAGIC detection assuming three different scenarios, namely: (1) a one-zone model considering only the emission from a compact blob outside the BLR; (2) a two-zone model consisting of a compact blob plus an emitting region encompassing the whole jet cross-section located outside the BLR; and (3) a two-zone model with the jet emitting region inside the BLR. In all cases we find that the high-energy emission from the compact blob is dominated by the inverse Compton scattering of the infrared thermal radiation of the dusty torus. Furthermore, both regions are matter-dominated, with the Poynting flux providing a negligible contribution to the total jet power. These results do not support models in which the compact blob is the result of reconnection events inside the jet or “needles” of high-energy electrons accelerated close to the BH. The observational framework and our radiative models might instead be compatible with scenarios in which the jet is re-collimated and focussed at large distances from the central BH.
The gamma-ray emission offers a powerful diagnostic tool to probe jets and their surroundings in flat-spectrum radio quasars (FSRQs). This motivates us to start a systematic study of flares with ...bright emission above 10 GeV, examining archival data of the Fermi-LAT gamma-ray telescope. Among others, we investigate the SED of a peculiar flare of 3C 454.3, showing a remarkably hard gamma-ray spectrum, quite different from the brightest flares of this source, and a bright flare of CTA 102. We modeled the SED in the framework of the one-zone leptonic model, using also archival optical spectroscopic data to derive the luminosity of the broad lines and thus estimate the disk luminosity, from which the structural parameters of the FSRQ nucleus can be inferred. We discussed the observed spectra and variability timescales in terms of injection and cooling of energetic particles, arguing that these flares could be triggered by magnetic reconnection events or turbulence in the flow.
Experimental and clinical evidence reported that some polyphenol-rich natural products may offer opportunities for the prevention and treatment of type 2 diabetes, due to their biological properties. ...Natural products have been suggested to modulate carbohydrate metabolism by various mechanisms, such as restoring β-cell integrity and physiology and enhancing insulin-releasing activity and glucose uptake. Endothelium is fundamental in regulating arterial function, whereas insulin resistance plays a pivotal role in pathophysiological mechanisms of prediabetic and diabetic states. Glucose and insulin actions in the skeletal muscle are improved by insulin-dependent production of nitric oxide, favoring capillary recruitment, vasodilatation, and increased blood flow. Endothelial dysfunction, with decreased nitric oxide bioavailability, is a critical step in the development of atherosclerosis. Furthermore, insulin resistance has been described, at least in part, to negatively affect endothelial function. Consistent with this, conditions of insulin resistance are usually linked to endothelial dysfunction, and the exposure of the endothelial cells to cardiovascular risk factors such as hypertension, dyslipidemia, and hyperglycemia is associated with reduced nitric oxide bioavailability, resulting in impaired endothelial-dependent vasodilatation. Moreover, endothelial dysfunction has been described as an independent predictor of cardiovascular risk and events. Cocoa and cocoa flavonoids may positively affect the pathophysiological mechanisms involved in insulin resistance and endothelial dysfunction with possible benefits in the prevention of cardiometabolic diseases.
Imaging Atmospheric Cherenkov Telescopes (IACT) are designed to detect γ-ray photons in the very-high energy (VHE) band from 50 GeV to more than 10 TeV. The few degree-scale field of view and the ...good angular resolution < 0.1 deg, favor morphological studies on extended sources and on diffuse emission. The description of the PSF (Point Spread Function) of IACT is a prerequisite to assess, for example, the possibility to reveal diffuse emission around point like sources. We study the PSF on γ-ray photons of IACTs using Crab Nebula data collected with the MAGIC stereoscopic system. Through a careful description of the background and response of the instrument we can build the γ-ray PSF corrected for the angular acceptance. We find a good analytical model describing the γ-ray PSF for IACTs and assess its stability.
Heart failure with preserved ejection fraction (HFpEF) is very frequently associated to sleep breathing disorders (SDB). Red blood cell distribution width (RDW) has been shown to be a potential ...inflammatory index linked to the degree of hypoxia and oxidative stress.
To identify the existence of a possible relationship between sleep apnea, oxygen saturation (SaO2) and RDW in a population of subjects affected by acute HFpEF (AHFpEF).
AHFpEF patients with known history of SDB were enrolled and performed blood chemistry, echocardiography, and 24-h polysomnography (PSG).
A total of 34 acute HFpEF patients (mean age 72.8 +/-8.63) were enrolled in the study. A control group of 24 non-HF patients were considered. Compared to controls, HFpEF patients showed a higher mean apnea hypopnea index (AHI), with prevalence of central apneas. A moderate to severe desaturation pattern was observed in AHFpEF vs. controls. RDW was significantly higher in AHFpEF patients vs. controls (mean value 14.7 +/-2.6 % vs. 9.1 +/-2.2,
< 0.05). In AHFpEF, RDW showed a positive correlation with time of SaO2 < 90% (
= 0.35,
= 0.04), and with mean length of apneic events (60 +/-28 s,
= 0.29,
= 0.03).
In patients with AHFpEF and SDB, a dependence relationship between RDW and duration of oxygen desaturation was observed, as if oxidative stress and inflammation related to RDW increase could also be linked to severity of sleep disorders in this population.
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