The Difguse radio emission and Dark Matter Marco Regis (Torino) - PowerPoint PPT Presentation

The Difguse radio emission and Dark Matter Marco Regis (Torino)

The ARCADE excess As we heard in previous talks, quite diffjcult to get rid of it! Possible explanations: Fornengo,MR+ JCAP 2014 I) Observations: issues on calibration of zero level for the low-frequency maps? disfavoured → Al Kogut, Dale Fixsen’s talks II) Galactic foreground : rather peculiar underhanded aspects? disfavoured → Nicolao Fornengo’s talk III) Extragalactic sources faint (< µ Jy), difguse (Mpc scale) and/or exceptionally numerous population (or truly difguse/high-z cosmological sources) Radio Synchrotron Background Conference, Richmond, 20/07/2017 Marco Regis

Proposed interpretations “New” radio source population taking over in the number counts at m Jy level (Singal+ 2010, Ysard&Lagache 2012, ...) Fornengo,MR+ PRL 2011 Galaxies would violate FIR-radio relation. Some “exotic” solutions: - WIMP DM annihilations (Fornengo+2011, Hooper+ 2012, Fang&Linden 2015) - late decay of metastable particle (Cline&Vincent 2013) - ultracompact minihalos (Yang+ 2013) - quark nugget dark matter (Lawson&Zhitnitsky 2013) - cluster mergers (Fang&Linden 2015) - fast radio transient (Kehayias+ 2015) Radio Synchrotron Background Conference, Richmond, 20/07/2017 Marco Regis

Dark matter interpretation Synchrotron emission induced by WIMP Fornengo,MR+ JCAP 2012 annihilations is a viable solution → see also Tim Linden’s talk Fang&Linden 2015 Requires signifjcant substructure contributions and large-scale magnetic fjelds . Constraints from other probes (such as the local e + -e - fmux that would be injected by DM) Radio Synchrotron Background Conference, Richmond, 20/07/2017 Marco Regis

Synchrotron radiation from DM Annihilations (or decays) of WIMP DM particles in astrophysical structures inject fmuxes of electrons and positrons (at GeV-TeV energy). If emitted in a medium with magnetic fjeld → radio continuum difguse emission associated to synchrotron radiation . Energy corresponding to the peak of synchrotron power (in the monochromatic approximation): It is an indirect^3 method to probe particle DM: source+propagation+radiation Radio Synchrotron Background Conference, Richmond, 20/07/2017 Marco Regis

DM source of e - /e + Spectrum of injection Morphology Halo profjle and concentration M R & U l Substructure distribution l i o , P R differential yield D Halo/subhalo mass function at small scales 2 0 0 8 e.g. the so called “clumping factor”: M R energy in units of DM mass + , P R L 2 0 1 5 Plot from Sanchez-Conde talk, 2014 Radio Synchrotron Background Conference, Richmond, 20/07/2017 Marco Regis

Transport of e - /e + Confjnement length << halo size = WIMP annihilation → morphology following DM e + γ Confjnement length ~ halo size Confjnement length >> halo size → morphology reshaped → signifjcant fraction of power carried away γ e + e + γ Radio Synchrotron Background Conference, Richmond, 20/07/2017 Marco Regis

Synchrotron emission DM main halo and subhalos Magnetic fjeld non-thermal population of galactic electrons Image credit: NASA, ESA, and T. Brown and J. Tumlinson (STScI) Dark structure It afgects both SED and morphology of the synchrotron emission V i a L a c t e a p r o j e c t Radio Synchrotron Background Conference, Richmond, 20/07/2017 Marco Regis

Promising cases Dark structure + magnetic fjeld “Traditional” structure with non-quiescient baryonic distribution but large scale magnetic fjeld Radio Synchrotron Background Conference, Richmond, 20/07/2017 Marco Regis

Awkward cases Dark structure with very feeble magnetic fjeld (e.g. only cosmological one) “Traditional” structure with non-quiescient baryonic distribution and with magnetic fjeld following baryons Radio Synchrotron Background Conference, Richmond, 20/07/2017 Marco Regis

How to test the DM source Digging into the unresolved radio background: Maps from Fornasa et al., 2013 - 1-point statistics: P(D) - 2-point statistics: auto and cross correlation Deep observations of individual sources : - Dwarf spheroidal galaxies - Clusters of galaxies - Big (and edge-on) galaxies - Filaments? Radio Synchrotron Background Conference, Richmond, 20/07/2017 Marco Regis

P(D) Observations by (Vernstrom+ 2015) suggest a contribution Fornengo,MR+ 2011 due to difguse emission above the point-like contribution (at the level of about 40% of the unresolved background) → see Tessa Vernstrom’s talk Radio Synchrotron Background Conference, Richmond, 20/07/2017 Marco Regis

Auto and cross correlations AUTO CORRELATION CROSS CORRELATION Holder 2014 with tracers of the DM distribution Fornengo&Regis 2014 → see Gil Holder’s talk Synchrotron signal from particle DM is concentrated at low z Radio Synchrotron Background Conference, Richmond, 20/07/2017 Marco Regis

EMU EMU is a deep (~10 m Jy/beam rms) radio continuum survey of the entire Southern Sky (below +30 deg) at 1.4 GHz, with a 10 arcsec resolution and sensitive to scales up to ~15 arcmin. It is expected to detect about 70 million galaxies Radio Synchrotron Background Conference, Richmond, 20/07/2017 Marco Regis

Correlations with EMU First ASKAP early science data have been recently released EMU early science cosmology should start this summer Full- project: 1.5 years of telescope time Raccanelli+ 2012 Mancuso+ 2015 SKA1 EMU Radio Synchrotron Background Conference, Richmond, 20/07/2017 Marco Regis

Dwarf spheroidal galaxies Hot and rapidly evolving fjeld: SDSS has more than doubled the known Local Group dSphs (25 new discoveries) A dozen of new ultrafaint satellites, mostly coming from DES observations, were discovered in the past couple of years Many more to come from near-future surveys. Low level of star formation Metal-poor stellar systems Hernandez et al., 2000 McConnachie, 2013 Carina dSph → The non-thermal Inferred from colour-magnitude diagram emission related to star- formation is expected to be extremely low . Why to perform radio observations? Radio Synchrotron Background Conference, Richmond, 20/07/2017 Marco Regis

Local Group dSph McConnachie, 2013 McConnachie, 2013 → Mass budget largely dominated by DM Very large mass-to-light ratio Promising target for particle DM searches! Radio Synchrotron Background Conference, Richmond, 20/07/2017 Marco Regis

ATCA campaigns Observations performed with the Australia Compact Telescope Array in two campaigns (2011 and 2016) 16 cm band, 20-30 hours on each dSph BootesII, Carina, Fornax, Hercules, ReticulumII, Sculptor , Segue2 (MR et al., MNRAS 2015a, MNRAS2015b, JCAP2014, JCAP 2017) - long baselines to map background sources - short baselines for the difguse emission search See also works from Spekkens et al. for similar searches but with a single dish (Green Bank Telescope) Radio Synchrotron Background Conference, Richmond, 20/07/2017 Marco Regis

Source subtraction Short-baseline map Source subtraction in UV-plane → Source subtraction is necessary to bring the noise down from its confusion level Radio Synchrotron Background Conference, Richmond, 20/07/2017 Marco Regis

WIMP hunt Radio Synchrotron Background Conference, Richmond, 20/07/2017 Marco Regis

Limits on difguse emission No signifjcant detection of an extended (few arcmin) emission. Bounds are far from the expected non-thermal emission related to star formation (which is in some cases possibly achievable by the SKA) Radio Synchrotron Background Conference, Richmond, 20/07/2017 Marco Regis