Revised equipartition and minimum energy formula for magnetic field strength estimates from radio synchrotron observations

The commonly used classical equipartition or minimum‐energy estimate of total magnetic fields strengths from radio synchrotron intensities is of limited practical use because it is based on the hardly known ratio K of the total energies of cosmic ray protons and electrons and also has inherent problems. We present a revised formula, using the number density ratio K for which we give estimates. For particle acceleration in strong shocks K is about 40 and increases with decreasing shock strength. Our revised estimate for the field strength gives larger values than the classical estimate for flat radio spectra with spectral indices of about 0.5–0.6, but smaller values for steep spectra and total fields stronger than about 10 µG. In very young supernova remnants, for example, the classical estimate may be too large by up to 10×. On the other hand, if energy losses of cosmic ray electrons are important, K increases with particle energy and the equipartition field may be underestimated significantly. Our revised larger equipartition estimates in galaxy clusters and radio lobes are consistent with independent estimates from Faraday rotation measures, while estimates from the ratio between radio synchrotron and X‐ray inverse Compton intensities generally give much weaker fields. This may be explained e.g. by a concentration of the field in filaments. Our revised field strengths may also lead to major revisions of electron lifetimes in jets and radio lobes estimated from the synchrotron break frequency in the radio spectrum. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

A new look at the position of the 1604 Supernova (V843 Ophiuchi)

The position of the supernova of 1604 (V843 Oph) is re‐assessed, with relevant discussion pertaining to the present‐day remnant, 3C 358. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

http://www.sciencedirect.com/science/article/pii/S1674987114000681

We present the disaster-forced biological evolution model as a general framework that includes Darwinian "phylogenic gradualism",Eldredge-Gould's "punctuated equilibrium",mass extinctions,and allopatric.parapatric,and sympatric speciation.It describes how reproductive isolation of organisms is established through global disasters due to supernova encounters and local disasters due to radioactive volcanic ash fall-outs by continental alkaline volcanism.Our new evolution model uniquely highlights three major factors of disaster-forced speciation:enhanced mutation rate by higher natural radiation level,smaller population size,and shrunken habitat size(i.e.,isolation among the individual populations).We developed a mathematical model describing speciation of a half-isolated group from a parental group,taking into account the population size(N_e),immigration rate(m),and mutation rate(μ).The model gives a quantitative estimate of the speciation,which is consistent with the observations of speciation speed.For example,the speciation takes at least 10~5 generations,if mutation rate is less than10~(-3) per generation per individual.This result is consistent with the previous studies,in which μ is assumed to be 10~(-3)-10~(-5).On the other hand,the speciation is much faster(less than 10~5 generations)for the case that μ is as large as 0.1 in parapatric conditions(m μ).Even a sympatric(m ~ 1) speciation can occur within 10~3 generations,if mutation rate is very high(μ~1 mutation per individual per generation),and if N_e 20-30.Such a high mutation rate is possible during global disasters due to supernova encounters and local disasters due to radioactive ash fall-outs.They raise natural radiation level by a factor of 100-1000.Such rapid speciation events can also contribute to macro-evolution during mass extinction events,such as observed during the Cambrian explosion of biodiversity.A similar rapid speciation(though in a much smaller scale) also has been undergoing in cichlid fishes and great African apes in the last several tens of thousand years in the current African rift valley,including the origin of humankind due to the radioactive ash fall-outs by continental alkaline volcanism.     

Diagnostics of supernova remnant shock waves

Fairly simple models can explain the emission from non-radiative shock waves in supernova remnants. This talk reviews some of the more robust diagnostics of shock parameters and some of the implications for the physics of collisionless shock waves in interstellar gas. The Hopkins Ultraviolet Telescope observed several non-radiative shocks during the ASTRO-2 mission, and the spectra have interesting implications for the physics of collisionless shocks.     

X-ray spectro-imagery of supernova remnants

Supernovae and their remnants play an essential role in the Interstellar Medium as one of the main sources of mechanical energy and heavy element production and as cosmic-ray accelerators. X-ray spectro-imagery is a key approach to look at these issues, as the collision of high velocity ejecta with the ambient medium generates high temperatures of the order of ten million degrees. I present recent results from the XMM-Newton and Chandra X-ray satellites on the elemental composition of young supernova remnants, on the spatial distribution of these synthesized elements and on the constraints obtained on the efficiency of particle acceleration at the shocks. This revised version was published online in September 2006 with corrections to the Cover Date.     

A search for young Galactic supernova remnants

A sample of eight small-diameter radio sources has been selected from the Molonglo Galactic Plane Survey (MGPS) as candidates for young Galactic supernova remnants. The sources have been identified in the IRAS and Midcourse Space Experiment infrared data bases and imaged in the H107α radio recombination line (RRL) using the Australia Telescope Compact Array (ATCA). Seven of the sources display high ratios of infrared-to-radio-continuum flux density and/or detectable RRLs and are almost certainly H ii regions. One source (G282.8−1.2) is identified as a possible new young Galactic supernova remnant, based on its relatively weak infrared emission, steep radio spectrum, and possible X-ray emission. The adopted method for distinguishing thermal and non-thermal Galactic radio sources seems promising and could be fruitfully applied to more than 100 small-diameter sources listed in the MGPS.     

Radial distributions of gamma-ray bursts and type Ib/c supernovae in galaxies

Data on the positions of gamma-ray bursts (GRBs) in galaxies are used to construct the radial distributions of their surface density. The gradient in GRB surface density is shown to decrease sharply at a galactocentric distance equal to the effective galactic radius. In central galactic regions, the GRB density distribution agrees with the galactic surface-brightness distribution; in outer regions, the GRB density decreases more slowly than does the surface brightness. Based on improved statistics, we analyze the radial distribution of type Ib/c supernovae. We show that it differs insignificantly from the distributions of other types of supernova and exhibits a much closer similarity to the distribution of star-forming regions than do GRBs. Although the statistics for GRBs is poor, the deviation of their distribution from the distribution of active star-forming regions in nearby galaxies seems to have been firmly established. A correlation of GRBs with the distribution of dark matter in outer galactic regions is not ruled out.     

Tomography of the Earth’s core using supernova neutrinos

We investigate the possibility to use the neutrinos coming from a future galactic supernova explosion to perform neutrino oscillation tomography of the Earth’s core. We propose to use existing or planned detectors, resulting in an additional payoff. Provided that all of the discussed uncertainties can be reduced as expected, we find that the average matter densities of the Earth’s inner and outer cores could be measured with a precision competitive with geophysics. However, since seismic waves are more sensitive to matter density jumps than average matter densities, neutrino physics would give partly complementary information.     

The unusual supernova remnant surrounding the ultraluminous X-ray source IC 342 X-1

We report the results of an observation of a large-diameter (110 pc) supernova remnant (SNR) found to encircle the position of the ultraluminous X-ray source (ULX) IC 342 X-1. The inferred initial energy input to the SNR is at least 2–3 times greater than the canonical energy for an 'ordinary' SNR. Two regions on the inside of the shell are bright in [O iii ]λ5007 emission, possibly as the result of X-ray photoionization by the ULX. If this is the case, then the morphology of this nebulosity implies that the X-ray emission from the ULX is anisotropic. The presence of the ULX, most probably a black hole X-ray binary, within an unusually energetic SNR suggests that we may be observing the aftermath of a gamma-ray burst, although other origins for the energetic nebula are discussed.