1 / 13

Deciphering the gamma-ray background: stafrorming galaxies, AGN, and the search for Dark Matter in the GeV Band.

Deciphering the gamma-ray background: stafrorming galaxies, AGN, and the search for Dark Matter in the GeV Band. Vasiliki Pavlidou Einstein Fellow. Shin’ichiro Ando (Caltech) Brandon Hensley (Caltech) Luis Reyes (U. Chicago) Jennifer Siegal-Gaskins (Ohio State) Tonia Venters (Goddard).

darva
Download Presentation

Deciphering the gamma-ray background: stafrorming galaxies, AGN, and the search for Dark Matter in the GeV Band.

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. Deciphering the gamma-ray background: stafrorming galaxies, AGN, and the search for Dark Matter in the GeV Band. Vasiliki PavlidouEinstein Fellow Shin’ichiro Ando (Caltech) Brandon Hensley (Caltech) Luis Reyes (U. Chicago) Jennifer Siegal-Gaskins (Ohio State) Tonia Venters (Goddard)

  2. 4 days of Fermi LAT Credit: LAT collaboration The gamma-ray sky

  3. What is making the GeV isotropic diffuse background? • Guaranteed sources: active galaxies, starforming galaxies • Hypothesized source classes: starburst galaxies, galaxy clusters, dark matter cusps

  4. VP & Fields 02, Ando & VP 09 Learn about B-fieldat high-z! What physics can we learn about galaxies? • How galaxies make gamma rays: • Gas makes stars • Stars blow up and make supernova remnants • Supernova remnants accelerate cosmic rays • Cosmic rays collide with gas, make pions, • Pions decay into gamma rays • How much diffuse gamma-ray emission due to all galaxies, everywhere, ever? Physics input to this calculation: • Cosmic star formation history (how much star formation, gas) • Cosmic-ray -- gas interactions • Cosmic-ray acceleration, confinement, escape

  5. Credit: J. Buckley 1998 (Science),illustration: K. Sutliff VP & Venters 08 Venters, Reyes & VP 09 What physics can we learn about AGN? • How AGN make gamma rays: • Gamma-ray loud AGN (blazar) has relativistic jet aimed at you • Some disturbance (?) accelerates electrons (?) to relativistic energies • Relativistic electrons Compton-upscatter soft photons (synchrotron? accretion disk? rescattered from broad line region?)to GeV energies • How much diffuse gamma-ray emission due to all AGN, everywhere, ever? Physics input to this calculation: • Luminosity function • Energy spectrum • Duty cycle • Extragalactic UV, optical, IR backgrounds! More input parameters, more complicated problem, less understood physics, fewer well-constrained inputs But also: more observables, more potential for discovery!

  6. Time passes, structure forms, density cusps develop, annihilation rate should be higher @ cusps! (Kolb 98) Why look for dark matter in -rays? Bang!

  7. Siegal-Gaskins & Pavlidou 2009, PhysRevLett.102.241301, arXiv:0901.3776 1GeV 10 GeV Siegal-Gaskins 08 Where do we look for DM with -rays? Where should we be looking? Individual sources: • Galactic Center (but: messy) • Nearby low-gas dwarf galaxies (but: faint) • Nearby MW substructure clumps (but: where?) Unresolved emission (isotropic diffuse): • Contribution from MW halo substructure, extragalactic sources • But: astrophysical foregrounds! DM signal could be subdominant… If only we could somehow enhance a subdominantDM signal…

  8. Siegal-Gaskins & Pavlidou 2009 PhysRevLett.102.241301, arXiv:0901.3776 Can we enhance a subdominant DM signal? Yes, we can! Take into account information about angular anisotropies • MW subhalos: few, nearby, lots of power at small scales • Blazars: many, faraway, very little power at small scales • There should be a transition in angular power at small scales as we move from low E (no DM) to high E (some DM)

  9. How well can we do? Preliminary Hensley, Siegal-Gaskins & Pavlidouin preparation

  10. How much can we learn? Preliminary We could measure the annihilation spectrum! Hensley, Siegal-Gaskins & Pavlidouin preparation

  11. Conclusions • A wealth of information on high-energy processes is encoded in the isotropic diffuse background in GeV energies starforming galaxies, blazars, dark matter(+ galaxy clusters, starburst galaxies, …) • A dark matter signal from the Milky Way substructure could be hiding in the isotropic diffuse background:More substructure away from Galactic center, where clumps are not tidally disrupted  collective unresolved clump emission appears isotropic • The DM signal can be robustly separated from other astrophysical contributions by combining spectral and anisotropy information • DM particle mass, annihilation spectrum can be recovered • Fermi is performing spectacularlyThe future is bright, stay tuned!

More Related