Deeper Chandra Follow-up of Cygnus TeV Source Perpetuates Mystery

A 50 ksec Chandra observation of the unidentified TeV source in Cygnus reported by the HEGRA collaboration reveals no obvious diffuse X-ray counterpart. However, 240 Pointlike X-ray sources are detected within or nearby the extended TeV J2032+4130 source region, of which at least 36 are massive stars and 2 may be radio emitters. That the HEGRA source is a composite, having as counterpart the multiple point-like X-ray sources we observe, cannot be ruled out. Indeed, the distribution of point-like X-ray sources appears non-uniform and concentrated broadly within the extent of the TeV source region. We offer a hypothesis for the origin of the very high energy gamma-ray emission in Cyg OB2 based on the local acceleration of TeV range cosmic rays and the differential distribution of OB vs. less massive stars in this association.Comment: Substantially revised version; incorporates referee suggestions & expanded discussio

Universal upper limit on inflation energy scale from cosmic magnetic field

Recently observational lower bounds on the strength of cosmic magnetic fields were reported, based on gamma-ray flux from distant blazars. If inflation is responsible for the generation of such magnetic fields then the inflation energy scale is bounded from above as rho_{inf}^{1/4} < 2.5 times 10^{-7}M_{Pl} times (B_{obs}/10^{-15}G)^{-2} in a wide class of inflationary magnetogenesis models, where B_{obs} is the observed strength of cosmic magnetic fields. The tensor-to-scalar ratio is correspondingly constrained as r< 10^{-19} times (B_{obs}/10^{-15}G)^{-8}. Therefore, if the reported strength B_{obs} \geq 10^{-15}G is confirmed and if any signatures of gravitational waves from inflation are detected in the near future, then our result indicates some tensions between inflationary magnetogenesis and observations.Comment: 12pages, v2: several discussions and references added, version accepted for publication by JCA

Constrained Simulations of the Magnetic Field in the Local Universe and the Propagation of UHECRs

We use simulations of LSS formation to study the build-up of magnetic fields (MFs) in the ICM. Our basic assumption is that cosmological MFs grow in a MHD amplification process driven by structure formation out of a seed MF present at high z. Our LCDM initial conditions for the density fluctuations have been statistically constrained by the observed galaxies, based on the IRAS 1.2-Jy all-sky redshift survey. As a result, prominent galaxy clusters in our simulation coincide closely with their real counterparts. We find excellent agreement between RMs of our simulated clusters and observational data. The improved resolution compared to previous work also allows us to study the MF in large-scale filaments, sheets and voids. By tracing the propagation of UHE protons in the simulated MF we construct full-sky maps of expected deflection angles of protons with arrival energies E=1e20eV and 4e19eV, respectively. Strong deflections are only produced if UHE protons cross clusters, however covering only a small area on the sky. Multiple crossings of sheets and filaments over larger distances may give rise to noticeable deflections, depending on the model adopted for the magnetic seed field. Based on our results we argue that over a large fraction of the sky the deflections are likely to remain smaller than the present experimental angular sensitivity. Therefore, we conclude that forthcoming air shower experiments should be able to locate sources of UHE protons and shed more light on the nature of cosmological MFs.Comment: 3revised version, JCAP, accepte

Risk of Post-Traumatic Stress Disorder in 111 survivors the 2009 Viareggio (Italy) Rail Crash: The role of mood spectrum comorbidity

Objectives: To explore the presence of PTSD and the potential correlations between the risk of developing PTSD and the lifetime mood spectrum signs and symptoms, as assessed with the Mood Spectrum Questionnaire Lifetime Version (MOODS-SR), in a sample of survivors of a liquid gas train crash in Italy, in 2009. Methods: One hundred eleven subjects were assessed with the Structured Clinical Interview for Axis I Disorder (SCID-I), the Mood Spectrum Questionnaire (MOODS-SR) Lifetime version, the Impact of Event Scale-Revised (IES-R), and the Trauma and Loss Spectrum Questionnaire (TALS-SR). Results: Sixty-six subjects, of the 111 who completed the SCID-I (59.5%), met criteria for PTSD. PTSD patients showed higher comorbidity rates for Generalized Anxiety Disorder (GAD) (p < 0.001), and lifetime and current Major Depressive Disorder (MDD) (p < 0.001) than subjects who did not develop PTSD. Lifetime MOODS-SR 'Sociability/Extraversion' factor and the prevalence of lifetime MDD differentiated subjects with from those without PTSD, when a multiple logistic regression analysis was performed. Conclusions: Although further research is needed, our results show a significant correlation between the risk of developing PTSD and the mood spectrum comorbidity

Testing hydrostatic equilibrium in galaxy cluster MS 2137

We test the assumption of strict hydrostatic equilibrium in galaxy cluster MS2137.3-2353 (MS 2137) using the latest CHANDRA X-ray observations and results from a combined strong and weak lensing analysis based on optical observations. We deproject the two-dimensional X-ray surface brightness and mass surface density maps assuming spherical and spheroidal dark matter distributions. We find a significant, 40%-50%, contribution from non-thermal pressure in the core assuming a spherical model. This non-thermal pressure support is similar to what was found by Molnar et al. (2010) using a sample of massive relaxed clusters drawn from high resolution cosmological simulations. We have studied hydrostatic equilibrium in MS 2137 under the assumption of elliptical cluster geometry adopting prolate models for the dark matter density distribution with different axis ratios. Our results suggest that the main effect of ellipticity (compared to spherical models) is to decrease the non-thermal pressure support required for equilibrium at all radii without changing the distribution qualitatively. We find that a prolate model with an axis ratio of 1.25 (axis in the line of sight over perpendicular to it) provides a physically acceptable model implying that MS 2137 is close to hydrostatic equilibrium at about 0.04-0.15 Rvir and have an about 25% contribution from non-thermal pressure at the center. Our results provide further evidence that there is a significant contribution from non-thermal pressure in the core region of even relaxed clusters, i.e., the assumption of hydrostatic equilibrium is not valid in this region, independently of the assumed shape of the cluster.Comment: 11 pages, 4 figures, accepted for publication in Ap

EGMF Constraints from Simultaneous GeV-TeV Observations of Blazars

Attenuation of the TeV gamma-ray flux from distant blazars through pair production with extragalactic background light leads to the development of electromagnetic cascades and subsequent, lower energy, GeV secondary gamma-ray emission. Due to the deflection of VHE cascade electrons by extragalactic magnetic fields (EGMF), the spectral shape of this arriving cascade gamma-ray emission is dependent on the strength of the EGMF. Thus, the spectral shape of the GeV-TeV emission from blazars has the potential to probe the EGMF strength along the line of sight to the object. We investigate constraints on the EGMF derived from observations of blazars for which TeV observations simultaneous with those by the Fermi telescope were reported. We study the dependence of the EGMF bound on the hidden assumptions it rests upon. We select blazar objects for which simultaneous Fermi/LAT GeV and Veritas, MAGIC or HESS TeV emission have been published. We model the development of electromagnetic cascades along the gamma-ray beams from these sources using Monte Carlo simulations, including the calculation of the temporal delay incurred by cascade photons, relative to the light propagation time of direct gamma-rays from the source. Constraints on EGMF could be derived from the simultaneous GeV-TeV data on the blazars RGB J0710+591, 1ES 0229+200, and 1ES 1218+304. The measured source flux level in the GeV band is lower than the expected cascade component calculated under the assumption of zero EGMF. Assuming that the reason for the suppression of the cascade component is the extended nature of the cascade emission, we find that B>10^{-15} G (assuming EGMF correlation length of ~1 Mpc) is consistent with the data. Alternatively, the assumption that the suppression of the cascade emission is caused by the time delay of the cascade photons the data are consistent with B>10^{-17} G for the same correlation length.Comment: 9 pages, 9 figure

GZK Photons Above 10 EeV

We calculate the flux of "GZK-photons", namely the flux of photons produced by extragalactic nucleons through the resonant photoproduction of pions, the so called GZK effect. This flux depends on the UHECR spectrum on Earth, of the spectrum of nucleons emitted at the sources, which we characterize by its slope and maximum energy, on the distribution of sources and on the intervening cosmological backgrounds, in particular the magnetic field and radio backgrounds. For the first time we calculate the GZK photons produced by nuclei. We calculate the possible range of the GZK photon fraction of the total UHECR flux for the AGASA and the HiRes spectra. We find that for nucleons produced at the sources it could be as large as a few % and as low as 10^{-4} above 10 EeV. For nuclei produced at the sources the maximum photon fraction is a factor of 2 to 3 times smaller above 10 EeV but the minimum could be much smaller than for nucleons. We also comment on cosmogenic neutrino fluxes.Comment: 20 pages, 9 figures (21 panels), iopart.cls and iopart12.clo needed to typese