We measure the correlation between the arrival directions of the highest energy cosmic rays detected by the Pierre Auger Observatory with the position of the galaxies in the HI Parkes All Sky Survey (HIPASS) catalogue, weighted for their HI flux and Auger exposure. The use of this absorption-free catalogue, complete also along the galactic plane, allows us to use all the Auger events. The correlation is significant, being 86.2% for the entire sample of HI galaxies, and becoming 99% when considering the richest galaxies in HI content, or 98% with those lying between 40-55. We interpret this result as the evidence that spiral galaxies are the hosts of the producers of UHECR and we briefly discuss classical (i.e energetic and distant) long Gamma Ray Burst (GRBs), short GRBs, as well as newly born or late flaring magnetars as possible sources of the Auger events. With the caveat that these events are still very few, and that the theoretical uncertainties are conspicuous, we found that newly born magnetars are the best candidates. If so, they could also be associated with sub-energetic, spectrally soft, nearby, long GRBs. We finally discuss why there is a clustering of Auger events in the direction on the radio-galaxy Cen A and an absence of events in the direction of the radio-galaxy M87.
The recent superflare of 27 December 2004 from the magnetar SGR 1806-20 was the brightest extrasolar flash ever recorded in the modern era. The chances for seeing exotic ultrahigh energy (UHE) radiation - neutrons, neutrinos, gamma rays and charged cosmic rays - from it are far better from an energetic point of view than from cosmological gamma ray bursts (GRBs). The chances for detecting the various components are discussed in light of recent data from the 27 December event.
We use the two-dimensional Kolmogorov-Smirnov (KS) test to study the correlation between the 60 cosmic ray events above 4x10^19 eV from the AGASA experiment and the positions of infrared luminous galaxies from the IRAS PSCz catalog. These galaxies are expected to be hosts to gamma ray bursts (GRB) and magnetars, both of which are associated with core collapse supernovae and have been proposed as possible acceleration sites for ultra high energy cosmic rays. We find consistency between the models and the AGASA events to have been drawn from the same underlying distribution of positions on the s…
We consider the voltage structure in the open-field circuit and outer magnetosphere of a magnetar. The standard polar-cap model for radio pulsars is modified significantly when the polar magnetic field exceeds 1.8x10^{14} G. Pairs are created by accelerated particles via resonant scattering of thermal X-rays, followed by the nearly instantaneous conversion of the scattered photon to a pair. A surface gap is then efficiently screened by e+- creation, which regulates the voltage in the inner part of the circuit to ~10^9 V. We also examine the electrostatic gap structure that can form when the ma…
I show that the relativistic winds of newly born magnetars with khz initial spin rates, occurring in all normal galaxies, can accelerate ultrarelativistic light ions with an E^{-1} injection spectrum, steepening to E^{-2} at higher energies, with an upper cutoff above 10^{21} eV. Interactions with the CMB yield a spectrum in good accord with the observed spectrum of Ultra-High Energy Cosmic Rays (UHECR), if ~ 5-10% of the magnetars are born with voltages sufficiently high to accelerate the UHECR. The form the spectrum spectrum takes depends on the gravitational wave losses during the magnetars…
The prototype for events that we call MFs - "March Fifth" events or "Magnetar Flares" - was observed on March 5, 1979. There is evidence that MFs are powered by catastrophic magnetic instabilities in ultramagnetized neutron stars. These events begin with brief (~ 0.1 - 1 s), intense, hard spikes of gamma rays followed by long (~ 100 s) softer tails of hard X-rays, modulated on the stellar rotation period. Prototypical MFs could have been detected by BATSE out to ~ 13 Mpc, nearly reaching the Virgo cluster. The likely number of isotropic, standard-candle MFs detected by the BATSE experiment is …
The short term variability of the Galactic cosmic ray flux (CRF) reaching Earth has been previously associated with variations in the global low altitude cloud cover. This CRF variability arises from changes in the solar wind strength. However, cosmic ray variability also arises intrinsically from variable activity of and motion through the Milky Way. Thus, if indeed the CRF climate connection is real, the increased CRF witnessed while crossing the spiral arms could be responsible for a larger global cloud cover and a reduced temperature, thereby facilitating the occurrences of ice ages. This …
Radio observations can show how cluster galaxies are affected by various environmental factors. We made three frequency radio-polarimetric VLA observations and performed sensitive XMM-Newton observations in X-rays and UV light of NGC4254. The distribution of total radio intensity at 8.46 4.86 GHz reveals a global asymmetry with a more diffuse and almost two times larger extension to the north than to the south. The radio polarized intensity is even more asymmetric, showing a strange bright ridge in the southern disk edge, displaced to the downstream side of the local density wave. Magnetic arm…
Magnetars can accelerate cosmic rays to high energies through the unipolar effect, and are also copious soft photon emitters. We show that young, fast-rotating magnetars whose spin and magnetic moment point in opposite directions emit high energy neutrinos from their polar caps through photomeson interactions. We identify a neutrino cut-off band in the magnetar period-magnetic field strength phase diagram, corresponding to the photomeson interaction threshold. Within uncertainties, we point out four possible neutrino emission candidates among the currently known magnetars, the brightest of whi…
We estimate the high energy neutrino flux from the giant flare of SGR 1806-20 on December 27, 2004, which irradiated Earth with a gamma-ray flux ~10^4 times larger than the most luminous gamma-ray bursts (GRBs) ever detected. The Antarctic Cherenkov neutrino detector AMANDA was on-line during the flare, and may either have detected high energy neutrinos for the first time from a cosmic point source, or put constraints on the flare mechanism of magnetars. If TeV neutrinos are detected, one would expect also detectable EeV cosmic rays and possibly TeV gamma-ray emission in coincidence.
Slow dissipation of non-potential magnetic fields in the magnetosphere of the magnetar is assumed to accelerate particles to hundreds MeV along the magnetic field lines. We consider interaction of fast particles with the surface of the magnetar. We argue that the collisionless dissipation does not work in the atmosphere of the neutron star because the two-stream instability is stabilized by the inhomogeneity of the atmosphere. Rather, the dominant dissipation mechanism is collisional Landau levelexcitations followed by pair production via the deexcitation gamma-rays ultimately leading to elect…
Highly luminous rapid flares are characteristic of processes around compact objects like white dwarfs, neutron stars or black holes. In the high energy regime of X- and gamma-rays, outbursts with variability time-scales of seconds and faster are routinely observed, e.g. in gamma-ray bursts or Soft Gamma Repeaters. In the optical, flaring activity on such time-scales has never been observed outside the prompt phase of GRBs. This is mostly due to the fact that outbursts with strong, fast flaring usually are discovered in the high-energy regime. Most optical follow-up observations of such transie…
A sudden release of high energy cosmic rays at the centre of a wind sustaining a spiral magnetic field produces cavities of low density and low magnetic field along the axis. The trajectories of high energy cosmic rays are focussed onto the axis, and lower energy cosmic rays and thermal plasma can escape through the cavities. This may explain the jets often seen in accretion systems and elsewhere.
Interstellar magnetic fields are strong: up to 25 muG in spiral arms and 40 muG in nuclear regions. In the spiral galaxy NGC 6946 the average magnetic energy density exceeds that of the thermal gas. Magnetic fields control the evolution of dense clouds and possibly the global star formation efficiency in galaxies. Gas flows and shocks in spiral arms and bars are modified by magnetic fields. Magnetic forces in star-forming circumnuclear regions are able to drive mass inflow towards the active nucleus. Magnetic fields are essential for the propagation of cosmic rays and the formation of galactic…
We are conducting a search for supermassive black holes (SMBHs) with masses below 10^7 M_sun by looking for signs of extremely low-level nuclear activity in nearby galaxies that are not known to be AGNs. Our survey has the following characteristics: (a) X-ray selection using the Chandra X-ray Observatory, since x-rays are a ubiquitous feature of AGNs; (b) Emphasis on late-type spiral and dwarf galaxies, as the galaxies most likely to have low-mass SMBHs; (c) Use of multiwavelength data to verify the source is an AGN; and (d) Use of the highest angular resolution available for observations in x…
Intriguing evidence has been accumulating for the production of cosmic rays in the Cygnus region of the Galactic plane. We here show that the IceCube experiment can produce incontrovertible evidence for cosmic ray acceleration by observing neutrinos from the decay of charged pions accompanying the TeV photon flux observed in the HEGRA, Whipple, Tibet and Milagro experiments. Our assumption is that the TeV photons observed are the decay products of neutral pions produced by cosmic ray accelerators in the nearby spiral arm of the Galaxy. Because of the proximity of the sources, IceCube will obta…
Some general features of cosmic ray acceleration are summarized along with some inferences that can be drawn concerning the origin of the UHE component. The UHE luminosity density is found to be similar to that derived for GeV cosmic rays and its slope suggests a distinct origin. Reports of clustering on small angular scale, if confirmed, would rule out most proposed source models. More generally, it is argued that the highest energy particles can only be accelerated in sites that can induce an EMF ${\cal E}\go3\times10^{20}$ V and an associated power $L_{min} \go {\cal E}^2/Z\sim10^{39}$ W, w…
The recently discovered soft gamma-ray emission from the anomalous X-ray pulsar 1E 1841-045 has a luminosity L_g ~ 10^{36} ergs/s. This luminosity exceeds the spindown power by three orders of magnitude and must be fed by an alternative source of energy such as an ultrastrong magnetic field. A gradual release of energy in the stellar magnetosphere is expected if it is twisted and a strong electric current is induced on the closed field lines. We examine two mechanisms of gamma-ray emission associated with the gradual dissipation of this current. (1) A thin surface layer of the star is heated b…
This paper discusses several aspects of current research on high energy emission from supernova remnants, covering the following main topics: 1) The recent evidence for magnetic field amplification near supernova remnant shocks, which makes that cosmic rays are more efficiently accelerated than previously thought. 2) The evidence that ions and electrons in some remnants have very different temperatures, and only equilibrate through Coulomb interactions. 3) The evidence that the explosion that created Cas A was asymmetric, and seems to have involved a jet/counter jet structure. And finally, 4),…
Spectral energy distributions (SEDs) are some of the most important sources of information for galaxies, especially for high redshift ones. Here we review recent work on the subject. We discuss the integrated spectra of galaxies of different morphological and activity type, their application to derive K-corrections and classification of high redshift objects. We also discuss the radio to X-rays SEDs of Seyfert 2's, Starbursts and normal galaxies, their behavior as a function of the waveband, their bolometric fluxes and the wavebands that contribute most to it.
We have performed a multiparametric analysis of luminosity data for a sample of 234 normal spiral and irregular galaxies observed in X-rays with the {\it Einstein Observatory}. This sample is representative of S and Irr galaxies, with a good coverage of morphological types and absolute magnitudes. In addition to X-ray and optical da ta, we have compiled H-band magnitudes, IRAS near- and far-infrared, and 6cm radio co ntinuum observations for the sample from the literature. We have also performed a carefu l compilation of distance estimates. We have explored the effect of morphology by dividing…
Gamma rays in the band from 20 MeV to 300 GeV, used in combination with data from radio and X-ray bands, provide a powerful tool for studying the origin of cosmic rays in our sister galaxies Andromeda and the Magellanic Clouds. Gamma-ray Large Area Space Telescope (GLAST) will spatially resolve these galaxies and measure the spectrum and intensity of diffuse gamma radiation from the collisions of cosmic rays with gas and dust in them. Observations of Andromeda will give an external perspective on a spiral galaxy like the Milky Way. Observations of the Magellanic Clouds will permit a study of c…
We compare the soft diffuse X-ray emission from Chandra images of 12 nearby intermediate inclination spiral galaxies to the morphology seen in Halpha, molecular gas, and mid-infrared emission. We find that diffuse X-ray emission is often located along spiral arms in the outer parts of spiral galaxies but tends to be distributed in a rounder morphology in the center. The X-ray morphology in the spiral arms matches that seen in the mid-infrared or Halpha and so implies that the X-ray emission is associated with recent active star formation. We see no strong evidence for X-ray emission trailing t…
In the first part of this review we discuss the basic observational features at the end of the cosmic ray energy spectrum. We also present there the main characteristics of each of the experiments involved in the detection of these particles. We then briefly discuss the status of the chemical composition and the distribution of arrival directions of cosmic rays. After that, we examine the energy losses during propagation, introducing the Greisen-Zaptsepin-Kuzmin (GZK) cutoff, and discuss the level of confidence with which each experiment have detected particles beyond the GZK energy limit. In …
