Gamma-rays from dark matter annihilations strongly constrain the substructure in halos

Recently, it has been shown that electrons and positrons from dark matter (DM) annihilations provide an excellent fit to the Fermi, PAMELA, and HESS data. Using this DM model, which requires an enhancement of the annihilation cross section over its standard value to match the observations, we show that it immediately implies an observable level of gamma-ray emission for the Fermi telescope from nearby galaxy clusters such as Virgo and Fornax. We show that this DM model implies a peculiar feature from final state radiation that is a distinctive signature of DM. Using the EGRET upper limit on the gamma-ray emission from Virgo, we constrain the minimum mass of substructures within DM halos to be > 5x10^-3 M_sun -- about four orders of magnitudes larger than the expectation for cold dark matter. This limits the cutoff scale in the linear matter power spectrum to k < 35/kpc which can be explained by e.g., warm dark matter. Very near future Fermi observations will strongly constrain the minimum mass to be > 10^3 M_sun: if the true substructure cutoff is much smaller than this, the DM interpretation of the Fermi/PAMELA/HESS data must be wrong. To address the problem of astrophysical foregrounds, we performed high-resolution, cosmological simulations of galaxy clusters that include realistic cosmic ray (CR) physics. We compute the dominating gamma-ray emission signal resulting from hadronic CR interactions and find that it follows a universal spectrum and spatial distribution. If we neglect the anomalous enhancement factor and assume standard values for the cross section and minimum subhalo mass, the same model of DM predicts comparable levels of the gamma-ray emission from DM annihilations and CR interactions. This suggests that spectral subtraction techniques could be applied to detect the annihilation signal.Comment: 5 pages, 2 figures (published version; minor corrections to figures and result, equation added

Human-animal interactions and safety during dairy cattle handling - comparing moving cows to milking and hoof trimming

Cattle handling is a dangerous activity on dairy farms, and cows are a major cause of injuries to livestock handlers. Even if dairy cows are generally tranquil and docile, when situations occur that they perceive or remember as aversive, they may become agitated and hazardous to handle. This study aimed to compare human-animal interactions, cow behavior, and handler safety when moving cows to daily milking and moving cows to more rarely occurring and possibly aversive hoof trimming. These processes were observed on 12 Swedish commercial dairy farms. The study included behavioral observations of handler and cows and cow heart rate recordings, as well as recording frequencies of situations and incidents related to an increased injury risk to the handler. At milking, cows were quite easily moved using few interactions. As expected, the cows showed no behavioral signs of stress, fear, or resistance and their heart rate only rose slightly from the baseline (i.e., the average heart rate during an undisturbed period before handling). Moving cows to hoof trimming involved more forceful and gentle interactions compared with moving cows to milking. Furthermore, the cows showed much higher frequencies of behaviors indicative of aversion and fear (e.g., freezing, balking, and resistance), as well as a higher increase in heart rate. The risk of injury to which handlers were exposed also increased when moving cows to hoof trimming rather than to routine milking. Some interactions (such as forceful tactile interactions with an object and pulling a neck strap or halter) appeared to be related to potentially dangerous incidents where the handler was being kicked, head-butted, or run over by a cow. In conclusion, moving cows to hoof trimming resulted in higher frequencies of behaviors indicating fear, more forceful interactions, and increased injury risks to the handler than moving cows to milking. Improving potentially stressful handling procedures (e.g., by better animal handling practices and preparation of cows to cope with such procedures) can increase handler safety, animal welfare, ease of handling, and efficiency