Indirect Searches for Dark Matter: a status review

I review in a schematic way the current status of indirect searches for Dark Matter: I list the main relevant experimental results of the recent years and I discuss the excitements and disappointments that their phenomenological interpretations in terms of almost-standard annihilating Dark Matter have brought along. I then try to individuate the main directions which have emerged from the recent very intense model-building activity. In passing, I list the main sources of uncertainties that affect this kind of searches.Comment: 32 pages, several figures. Extended version of the text for the Proceedings of Lepton-Photon 2011, Mumbai. Comments and notifications of inaccuracies, oversights or omissions are welcome (except on ref. [154]). v2: refs added. v3: updated bounds and added short discussions of gamma-ray line claims. (v4: just a couple of corrections in refs.) v5: more refs & details added, updated neutrino bound

Updated galactic radio constraints on Dark Matter

We perform a detailed analysis of the synchrotron signals produced by Dark Matter annihilations and decays. We consider different set-ups for the propagation of electrons and positrons, the galactic magnetic field and Dark Matter properties. We then confront these signals with radio and microwave maps, including Planck measurements, from a frequency of 22 MHz up to 70 GHz. We derive two sets of constraints: conservative and progressive, the latter based on a modeling of the astrophysical emission. Radio and microwave constraints are complementary to those obtained with other indirect detection methods, especially for dark matter annihilating into leptonic channels.Comment: 20 pages, 10 figures. v2: some small additions, matches journal versio

PPPC 4 DM secondary: A Poor Particle Physicist Cookbook for secondary radiation from Dark Matter

We enlarge the set of recipes and ingredients at disposal of any poor particle physicist eager to cook up signatures from weak-scale Dark Matter models by computing two secondary emissions due to DM particles annihilating or decaying in the galactic halo, namely the radio signals from synchrotron emission and the gamma rays from bremsstrahlung. We consider several magnetic field configurations and propagation scenarios for electrons and positrons. We also provide an improved energy loss function for electrons and positrons in the Galaxy, including synchrotron losses in the different configurations, bremsstrahlung losses, ionization losses and Inverse Compton losses with an updated InterStellar Radiation Field.Comment: 25 pages, many figures. v2: a small clarification on the use of custom galactic magnetic fields added, matches version published on JCAP. All results are available at http://www.marcocirelli.net/PPPC4DMID.htm

Constraints on Dark Matter annihilations from reionization and heating of the intergalactic gas

Dark Matter annihilations after recombination and during the epoch of structure formation deposit energy in the primordial intergalactic medium, producing reionization and heating. We investigate the constraints that are imposed by the observed optical depth of the Universe and the measured temperature of the intergalactic gas. We find that the bounds are significant, and have the power to rule out large portions of the `DM mass/cross section' parameter space. The optical depth bound is generally stronger and does not depend significantly on the history of structure formation. The temperature bound can be competitive in some cases for small masses or the hadronic annihilation channels (and is affected somewhat by the details of structure formation). We find in particular that DM particles with a large annihilation cross section into leptons and a few TeV mass, such as those needed to explain the PAMELA and FERMI+HESS cosmic ray excesses in terms of Dark Matter, are ruled out as they produce too many free electrons. We also find that low mass particles (<~ 10 GeV) tend to heat too much the gas and are therefore disfavored.Comment: 22 pages, 5 figures; v2: minor comments added, matches version published on JCA

Bremsstrahlung gamma rays from light Dark Matter

We discuss the often-neglected role of bremsstrahlung processes on the interstellar gas in computing indirect signatures of Dark Matter (DM) annihilation in the Galaxy, particularly for light DM candidates in the phenomenologically interesting O(10) GeV mass range. Especially from directions close to the Galactic Plane, the expected gamma-ray spectrum is altered via two effects: directly, by the photons emitted in the bremsstrahlung process on the interstellar gas by energetic electrons which are among the DM annihilation byproducts; indirectly, by the modification of the same electron spectrum, due to the additional energy loss process in the diffusion-loss equation (e.g. the resulting inverse Compton emission is altered). We quantify the importance of the bremsstrahlung emission in the GeV energy range, showing that it is the dominant component of the gamma-ray spectrum for some cases. We also find that, in regions in which bremsstrahlung dominates energy losses, the related gamma-ray emission is only moderately sensitive to possible large variations in the gas density. Still, we stress that, for computing precise spectra in the (sub-)GeV range, it is important to obtain a reliable description of the inner Galaxy gas distribution as well as to compute self-consistently the gamma emission and the solution to the diffusion-loss equation. For example, these are crucial issues to quantify and interpret meaningfully gamma-ray map `residuals' in terms of (light) DM annihilations.Comment: 17 pages, 5 figures, 1 table; references added, changed to match the published versio