The longevity of para-aminopropiophenone (PAPP) wild dog baits and the implications for effective and safe baiting campaigns

Considerable effort goes into mitigating the impacts caused by invasive animals and prohibiting their establishment or expansion. In Australia, management of wild dogs (Canis lupus dingo and their hybrids) and their devastating impacts is reliant upon poison baiting. The recent release of baits containing the humane toxin para-aminopropiophenone (PAPP) offers potential improvements for control of wild dogs, but little is known about the environmental persistence of PAPP in manufactured baits that could be used to inform best practice guidelines. We investigated the degradation rate of PAPP wild dog baits (DOGABAIT™) under typical field usage and storage conditions in north-eastern Australia and calculated optimal deployment and withholding periods. The PAPP content of buried baits declines faster than surface-laid baits, but both presentations retained lethal doses to wild and domestic dogs for considerable periods (6–16 weeks). Domestic or working dogs should be suitably restrained or excluded from baited areas for extended periods, particularly under dry conditions, to minimise poisoning risk. The period of persistence of PAPP baits may provide opportunities to improve the duration or longer term efficacy of baiting campaigns, but care is needed to protect domestic and working dogs to ensure responsible and safe use

Cosmic ray acceleration parameters from multi-wavelength observations. The case of SN 1006

The properties of the Galactic supernova remnant SN 1006 are theoretically reanalysed. Nonlinear kinetic theory is used to determine the acceleration efficiency of cosmic rays (CRs) in the supernova remnant SN 1006. The known range of astronomical parameters and the existing measurements of nonthermal emission are examined in order to define the values of the relevant physical parameters which determine the CR acceleration efficiency. It is shown that the parameter values -- proton injection rate, electron to proton ratio and downstream magnetic field strength -- are determined with the appropriate accuracy. In particular also the observed azimuthal variations in the gamma-ray morphology agree with the theoretical expectation. These parameter values, together with the reduction of the gamma-ray flux relative to a spherically symmetric acceleration geometry, allow a good fit to the existing data, including the recently detected TeV emission by H.E.S.S. SN 1006 represents the first example where a high efficiency of nuclear CR production, required for the Galactic CR sources, is consistently established.Comment: 10 pages, 6 figures, accepted for publication in A&

Nonthermal Bremsstrahlung and Hard X-ray Emission from Clusters of Galaxies

We have calculated nonthermal bremsstrahlung (NTB) models for the hard X-ray (HXR) tails recently observed by BeppoSAX in clusters of galaxies. In these models, the HXR emission is due to suprathermal electrons with energies of about 10-200 keV. Under the assumption that the suprathermal electrons form part of a continuous spectrum of electrons including highly relativistic particles, we have calculated the inverse Compton (IC) extreme ultraviolet (EUV), HXR, and radio synchrotron emission by the extensions of the same populations. For accelerating electron models with power-law momentum spectra (N[p] propto p^{- mu}) with mu <~ 2.7, which are those expected from strong shock acceleration, the IC HXR emission exceeds that due to NTB. Thus, these models are only of interest if the electron population is cut-off at some upper energy <~1 GeV. Similarly, flat spectrum accelerating electron models produce more radio synchrotron emission than is observed from clusters if the ICM magnetic field is B >~ 1 muG. The cooling electron model produces vastly too much EUV emission as compared to the observations of clusters. We have compared these NTB models to the observed HXR tails in Coma and Abell 2199. The NTB models require a nonthermal electron population which contains about 3% of the number of electrons in the thermal ICM. If the suprathermal electron population is cut-off at some energy above 100 keV, then the models can easily fit the observed HXR fluxes and spectral indices in both clusters. For accelerating electron models without a cutoff, the electron spectrum must be rather steep >~ 2.9.Comment: Accepted for publication in the Astrophysical Journal. 10 pages with 5 embedded Postscript figures in emulateapj.sty. An abbreviated abstract follow

IRAC Observations of Taurus Pre-Main Sequence Stars

We present infrared photometry obtained with the IRAC camera on the Spitzer Space Telescope of a sample of 82 pre-main sequence stars and brown dwarfs in the Taurus star-forming region. We find a clear separation in some IRAC color-color diagrams between objects with and without disks. A few ``transition'' objects are noted, which correspond to systems in which the inner disk has been evacuated of small dust. Separating pure disk systems from objects with remnant protostellar envelopes is more difficult at IRAC wavelengths, especially for objects with infall at low rates and large angular momenta. Our results generally confirm the IRAC color classification scheme used in previous papers by Allen et al. and Megeath et al. to distinguish between protostars, T Tauri stars with disks, and young stars without (inner) disks. The observed IRAC colors are in good agreement with recent improved disk models, and in general accord with models for protostellar envelopes derived from analyzing a larger wavelength region. We also comment on a few Taurus objects of special interest. Our results should be useful for interpreting IRAC results in other, less well-studied star-forming regions.Comment: 29 pages 10 figures, to appear in Ap

The high energy gamma-ray emission expected from Tycho's supernova remnant

A nonlinear kinetic model of cosmic ray (CR) acceleration in supernova remnants (SNRs) is used to describe the properties of Tycho's SNR. Observations of the expansion characteristics and of the nonthermal radio and X-ray emission spectra, assumed to be of synchrotron origin, are used to constrain the overall dynamical evolution and the particle acceleration parameters of the system, in addition to what is known from independent estimates of the distance and thermal X-ray observations. It is shown that a very efficient production of nuclear cosmic rays, leading to strong shock modification, and a large downstream magnetic field strength B_d approx 240muG are required to reproduce the observed synchrotron emission from radio to X-ray frequencies. This field strength is still well within the upper bound for the effective magnetic field, consistent with the acceleration process. The pi^0-decay gamma-ray flux turns out to be somewhat greater than the inverse Compton (IC) flux off the Cosmic Microwave Background at energies below 1 TeV, dominating it strongly at 10 TeV. The predicted TeV gamma-ray flux is consistent with but close to the very low upper limit recently obtained by HEGRA. A future detection at E_gamma ~ 10 TeV would clearly indicate hadronic emission.Comment: 8 pages, 6 figures. Accepted in Astronomy and Astrophyic

Variation of cosmic ray injection across supernova shocks

The injection rate of suprathermal protons into the diffusive shock acceleration process should vary strongly over the surface of supernova remnant shocks. These variations and the absolute value of the injection rate are investigated. In the simplest case, like for SN 1006, the shock can be approximated as being spherical in a uniform large-scale magnetic field. The injection rate depends strongly on the shock obliquity and diminishes as the angle between the ambient field and the shock normal increases. Therefore efficient particle injection, which leads to conversion of a significant fraction of the kinetic energy at a shock surface element, arises only in relatively small regions near the "poles", reducing the overall CR production. The sizes of these regions depend strongly on the random background field and the Alfven wave turbulence generated due to CR streaming instability. For the cases of SN 1006 and Tycho's SNR they correspond to about 20, and for Cas A to between 10 and 20 percent of the entire shock surface. In first approximation, the CR production rate, calculated under the assumption of spherical symmetry, has therefore to be renormalized by this factor, while the shock as such remains roughly spherical.Comment: 10 pages, 4 figures. To appear in Astronomy and Astrophyics; Corrected typos, references change

Cosmic Ray Protons and Magnetic Fields in Clusters of Galaxies and their Cosmological Consequences

The masses of clusters of galaxies estimated by gravitational lensing exceed in many cases the mass estimates based on hydrostatic equilibrium. This may suggest the existence of nonthermal pressure. We ask if radio galaxies can heat and support the cluster gas with injected cosmic ray protons and magnetic field densities, which are permitted by Faraday rotation and gamma ray observations of clusters of galaxies. We conclude that they are powerful enough to do this within a cluster radius of roughly 1 Mpc. If present, nonthermal pressures could lead to a revised estimate of the ratio of baryonic mass to total mass, and the apparent baryonic overdensity in clusters would disappear. In consequence, $\Omega_{\rm cold}$, the clumping part of the cosmological density $\Omega_{o}$, would be larger than $0.4\,h_{50}^{-1/2}$.Comment: Accepted by ApJ, 16 pages, LaTeX, 2 figures, epsfig.sty, aaspp4.st