Observational evidence of spin-induced precession in active galactic nuclei

We show that it is possible to explain the physical origin of jet precession in active galactic nuclei (AGNs) through the misalignment between the rotation axes of the accretion disk and of the Kerr black hole. We apply this scenario to quasars, Seyfert galaxies and also to the Galactic Center black hole Sgr A*, for which signatures of either jet or disk precession have been found. The formalism adopted is parameterized by the ratio of the precession period to the black hole mass and can be used to put constraints to the physical properties of the accretion disk as well as to the black hole spin in those systems.Comment: 10 pages, 1 figure, accepted for publication in ApJ Letter

Host galaxies of bright high redshift quasars: Luminosities and colours

We present the results of a near-infrared imaging study of high redshift (z~3) quasars using the ESO-VLT. Our targets were selected to have luminosities among the highest known (absolute magnitude M_B <~ -28. We searched for resolved structures underlying the bright point-source nuclei by comparing the QSO images with stars located in the same fields. Two QSOs (HE2348-1444 at z=2.904 and HE2355-5457 at z=2.933) are clearly resolved in K_S, and with somewhat lower significance also in H; one object is resolved only in K_S. At these redshifts, H and K_S correspond almost exactlly to rest-frame B and V, respectively, with virtually no K-correction. We also report briefly the non-detection of some additional QSOs. The detected host galaxies are extremely luminous with M_V ~ -25. Their rest-frame B-V colours, however, are close to zero in the Vega system, indicating substantial contributions from young stars and a stellar mass-to-light ratio below 1 (in solar units). Tentatively converting M_V and B-V into rough estimates of stellar masses, we obtain values of M_star in the range of several 10^11 M_sun, placing them within the high-mass range of recent high-redshift galaxy surveys. We present optical spectra and use CIV line width measurements to predict virial black hole masses, obtaining typical values of M_bh ~ 5x10^9 M_sun. With respect to the known correlation between host galaxy luminosity L_V(host) and M_bh, our measurements reach to higher luminosities and redshifts than previous studies, but are completely consistent with them. Comparing our objects with the local (z~0) M_bh - M_bulge relation and taking also the low stellar mass-to-light ratios into account, we find tentative evidence for an excess in the M_bh/M_bulge mass ratio at z~3.Comment: 9 pages, 7 figures, accepted for publication in A&

What is Minimal Model of 3He Adsorbed on Graphite? -Importance of Density Fluctuations in 4/7 Registered Solid -

We show theoretically that the second layer of 3He adsorbed on graphite and solidified at 4/7 of the first-layer density is close to the fluid-solid boundary with substantial density fluctuations on the third layer. The solid shows a translational symmetry breaking as in charge-ordered insulators of electronic systems. We construct a minimal model beyond the multiple-exchange Heisenberg model. An unexpectedly large magnetic field required for the measured saturation of magnetization is well explained by the density fluctuations. The emergence of quantum spin liquid is understood from the same mechanism as in the Hubbard model and in \kappa-(ET)_2Cu_2(CN)_3 near the Mott transitions.Comment: 9 pages, 5 figure

APOE4 allele disrupts resting state fMRI connectivity in the absence of amyloid plaques or decreased CSF Aβ42

Identifying high risk populations is an important component of disease prevention strategies. One approach is examining neuroimaging parameters that differ in Alzheimer’s disease (AD), including functional connections known to be disrupted within the “default mode network” (DMN). We have previously shown these same disruptions in cognitively normal elderly, who have amyloid-beta (Aβ) plaques detected using PIB PET imaging, suggesting neuronal toxicity of plaques. Here we sought to determine if pathological effects of apolipoprotein E ε4 (APOE4) genotype could be seen independent of Aβ plaque toxicity by examining resting state fMRI functional connectivity (fcMRI ) in participants without preclinical fibrillar amyloid deposition (PIB−). Cognitively normal participants enrolled in longitudinal studies (n = 100, mean age = 62) who were PIB− were categorized into those with and without an APOE 4 allele and studied using fcMRI. APOE 4 allele carriers (E4+) differed significantly from E4− in functional connectivity of the precuneus to several regions previously defined as having abnormal connectivity in a group of AD participants. These effects were observed prior to any manifestations of cognitive changes and in the absence of brain fibrillar amyloid-beta (Aβ) plaque deposition, suggesting that early manifestations of a genetic effect can be detected using fcMRI and that these changes may antedate the pathological effects of fibrillar amyloid plaque toxicity

On the central black hole mass in Mkn~501

We analyse the apparent disagreement between the mass estimates of the central black hole(s) in Mkn~501 based on (i) the observations of the host galaxy, (ii) the high energy (HE) emission mechanism, and (iii) the modulation of the beamed radiation by a black hole (BH) binary system. While method (i) seems to imply a central mass > 5\times 10^8 M_{sun}, method (ii) suggests a BH mass less than 6 \times 10^7 M_{sun}. We critically discuss the estimates inferred from (i) showing that current uncertainties may permit a central mass as low as ~(2-3)\times 10^8 M_{sun}. We demonstrate that in this case the estimates (i) and (ii) might be brought into agreement by assuming a binary BH system where the jet dominating the HE emission originates from the less massive (secondary) BH as suggested by method (iii). On the other hand, if Mkn~501 has in fact a high central BH mass of order 10^9 M_{sun}, a change of fundamental assumptions seems to be required in the context of several HE emission models. We show, that in this case a binary scenario following (iii) may be still possible if the jet which dominates the emission emerges from the more massive (primary) BH and if the binary evolution passes through phases of super-Eddington accretion and/or decreased conversion efficiency.Comment: 6 pages, 1 figure; accepted for publication in A&

GEMINI 3D spectroscopy of BAL+IR+Fe II QSOs: II. IRAS 04505-2958 an explosive QSO with hypershell and a new scenario for galaxy formation and galaxy end

From a study of BAL + IR + Fe II QSOs (using deep Gemini GMOS-IFU spectroscopy) new results are presented: for IRAS 04505-2958. Specifically, we have studied in detail the out flow (OF) process and their associated structures, mainly at two large galactic scales: (i) two blobs/shells (S1, S2) at radius r = 1.1 and 2.2 kpc; and (ii) an external hypergiant shell (S3) at r = 11 kpc. In addition, the presence of two very extended hypergiant shells (S4, S5) at r = 80 kpc is discussed. From this GMOS study the following main results were obtained: (i) For the external hypergiant shell S3 the kinematics GMOS maps of the ionized gas show very similar features to those observed for the prototype of exploding external supergiant shell: in NGC 5514. (ii) The main knots K1, K2 and K3 -of this hypergiant shell S3- show a stellar population and emission line ratios associated with the presence of a starburst + OF/shocks. (iii) The internal shells S1 and S2 show structures, OF components and properties very similar to those detected in the nuclear shells of Mrk 231. (iv) The shells S1+S2 and S3 are aligned at PA = 131: i.e. suggesting that the OF process is in the blow-out phase with bipolar structure. In addition, the shells S4 and S5 (at 80-100 kpc scale) are aligned at PA = 40, i.e.: a bipolar OF perpendicular to the internal OF. Finally, the generation of UHE cosmic rays and neutrino/ dark-matter -associated with HyNe in BAL + IR + Fe II QSOs- is discussed.Comment: Submitted MNRAS, 81 pages, 25 Figure

All-sky search for time-integrated neutrino emission from astrophysical sources with 7 years of IceCube data

Since the recent detection of an astrophysical flux of high energy neutrinos, the question of its origin has not yet fully been answered. Much of what is known about this flux comes from a small event sample of high neutrino purity, good energy resolution, but large angular uncertainties. In searches for point-like sources, on the other hand, the best performance is given by using large statistics and good angular reconstructions. Track-like muon events produced in neutrino interactions satisfy these requirements. We present here the results of searches for point-like sources with neutrinos using data acquired by the IceCube detector over seven years from 2008--2015. The discovery potential of the analysis in the northern sky is now significantly below $E_\nu^2d\phi/dE_\nu=10^{-12}\:\mathrm{TeV\,cm^{-2}\,s^{-1}}$, on average $38\%$ lower than the sensitivity of the previously published analysis of four years exposure. No significant clustering of neutrinos above background expectation was observed, and implications for prominent neutrino source candidates are discussed.Comment: 19 pages, 17 figures, 3 tables; ; submitted to The Astrophysical Journa

Warping and precession in galactic and extragalactic accretion disks

The Bardeen-Petterson general relativistic effect has been suggested as the mechanism responsible for precession in some accretion disk systems. Here we examine separately four mechanisms (tidally-induced, irradiation-induced, magnetically-induced and Bardeen-Petterson-induced) that can lead to warping and precession. We use a sample of eight X-ray binaries and four Active Galactic Nuclei (AGNs) that present signatures of warping and/or precession in their accretion disks to explore the viability of the different mechanisms. For the X-ray binaries SMC X-1 and 4U 1907+09 all four mechanisms provide precession periods compatible with those observed, while for Cyg X-1 and the active galaxies Arp 102B and NGC 1068, only two mechanisms are in agreement with the observations. The irradiation-driven instability seems incapable of producing the inferred precession of the active galaxies in our sample, and the tidally-induced precession can probably be ruled out in the case of Arp 102B. Perhaps the best case for a Bardeen-Petterson precession can be achieved for NGC 1068. Our results show that given the many observational uncertainties that still exist, it is extremely difficult to confirm unambiguously that the Bardeen-Petterson effect has been observed in any of the other sources of our sample.Comment: 35 pages, 8 figures, accepted for publication in The Astrophysical Journa

Searches for sterile neutrinos with the IceCube detector

The IceCube neutrino telescope at the South Pole has measured the atmospheric muon neutrino spectrum as a function of zenith angle and energy in the approximate 320 GeV to 20 TeV range, to search for the oscillation signatures of light sterile neutrinos. No evidence for anomalous nu(mu) or (nu) over bar (mu) disappearance is observed in either of two independently developed analyses, each using one year of atmospheric neutrino data. New exclusion limits are placed on the parameter space of the 3 + 1 model, in which muon antineutrinos experience a strong Mikheyev-Smirnov-Wolfenstein-resonant oscillation. The exclusion limits extend to sin(2)2 theta(24) <= 0.02 at Delta m(2) similar to 0.3 eV(2) at the 90% confidence level. The allowed region from global analysis of appearance experiments, including LSND and MiniBooNE, is excluded at approximately the 99% confidence level for the global best-fit value of vertical bar U-e4 vertical bar(2)

An All-Sky Search for Three Flavors of Neutrinos from Gamma-Ray Bursts with the IceCube Neutrino Observatory

We present the results and methodology of a search for neutrinos produced in the decay of charged pions created in interactions between protons and gamma-rays during the prompt emission of 807 gamma-ray bursts (GRBs) over the entire sky. This three-year search is the first in IceCube for shower-like Cherenkov light patterns from electron, muon, and tau neutrinos correlated with GRBs. We detect five low-significance events correlated with five GRBs. These events are consistent with the background expectation from atmospheric muons and neutrinos. The results of this search in combination with those of IceCube's four years of searches for track-like Cherenkov light patterns from muon neutrinos correlated with Northern-Hemisphere GRBs produce limits that tightly constrain current models of neutrino and ultra high energy cosmic ray production in GRB fireballs.Comment: 33 pages, 14 figures; minor changes made to match published version in the Astrophysical Journal, 2016 June 2