1 / 10

Cosmology with the extragalactic gamma-ray background

Cosmology with the extragalactic gamma-ray background. Vasiliki Pavlidou University of Chicago. Outline. EGRB vs CMB: information content Cosmology with the EGRB: constraining the Cosmic Star Formation Rate The future. EGRB vs CMB. CMB EGRB

albert
Download Presentation

Cosmology with the extragalactic gamma-ray background

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. Cosmology with the extragalactic gamma-ray background Vasiliki PavlidouUniversity of Chicago

  2. Outline • EGRB vs CMB: information content • Cosmology with the EGRB: constraining the Cosmic Star Formation Rate • The future Vasiliki Pavlidou Great Lakes Cosmology Workshop 8 Ohio State University, 01June 2007

  3. EGRB vs CMB CMB EGRB • Origin: cosmological cosmological truly diffuse unresolved point sources • Foregrounds: Milky Way Milky Way • Energies: ~ 2.7 K ~ 109eV (1GeV) • Spectrum: blackbody power law Vasiliki Pavlidou Great Lakes Cosmology Workshop 8 Ohio State University, 01June 2007

  4. Credit: Strong et al 2004 EGRB: how is it measured? what does it look like? • Space-born gamma-ray telescopes: • EGRET aboard CGRO (1990’s) • LAT aboard GLAST (about to be launched) • Take all -sky map, subtract: • Emission from the Milky Way • Point sources Vasiliki Pavlidou Great Lakes Cosmology Workshop 8 Ohio State University, 01June 2007

  5. What makes up the EGRB? • Guaranteed contributions: established classes of gamma-ray emitters • Normal galaxies • Active galaxies • Extragalactic unidentified sources • Truly diffuse emission? • Exotic physics? Vasiliki Pavlidou Great Lakes Cosmology Workshop 8 Ohio State University, 01June 2007

  6. And now… cosmology Vasiliki Pavlidou Great Lakes Cosmology Workshop 8 Ohio State University, 01June 2007

  7. compilation by Hopkins & Beacom 2006 The Cosmic Star Formation Rate • The Cosmic Star Formation Rate: how much gas mass is converted to stars per unit time per unit cosmic volume • An essential measure of: • baryonic energy production • feedback processes in galaxy formation • stellar contribution to reionization • metal production • Traditional measures: SF makes stars - young stars emit in UV, IR Vasiliki Pavlidou Great Lakes Cosmology Workshop 8 Ohio State University, 01June 2007

  8. Stecker 1999 Starforming galaxies (VP & Fields 2002)Unidentified sources (VP, Siegal-Gaskins, Fields, Olinto & Brown 2007)Blazars (VP & Venters 2007)EGRET gamma-ray background, conservative (Strong et al 2004) Maximal EGRET gamma-ray background (Sreekumar et al 1998) The SF - gamma-ray connection • Star Formation -> Supernovae -> Cosmic ray acceleration -> interaction with ISM -> gamma rays • Characteristic normal galaxy spectral feature imprinted on spectral shape of gamma-ray background • Star Formation -> Background starlight (EBL) -> interaction with gamma rays • EBL imprinted on spectra of: individual -ray sources, -ray background Vasiliki Pavlidou Great Lakes Cosmology Workshop 8 Ohio State University, 01June 2007

  9. Prodanovic, VP & Fields preliminary Strigari, Beacom, Walker & Zhang 2005 How do we utilize this connection? • Until now: use knowledge of CSFR to predict signal/effects for gamma-ray telescopes • The future: GLAST observations will allow inversion of the problem: use observations of gamma-ray signal/effects to constrain CSFR • Uncertainties: significant, BUT largely uncorrelated with uncertainties of low-E methods Vasiliki Pavlidou Great Lakes Cosmology Workshop 8 Ohio State University, 01June 2007

  10. Conclusions • Cosmic star formation history imprinted on extragalactic gamma-ray background: • Normal galaxy spectral feature @ ≈ 1GeV • EBL absorption pileup/suppression @ ≥20GeV • GLAST will: • resolve thousands of bright point sources (e.g. AGNs) but at most 3 normal galaxies -> normal galaxy feature expected to become visible • Probe the >20GeV regime, map the shape of high-E absorption feature • A new era: observations of the EGRB can strongly constrain the cosmic history of star formation Vasiliki Pavlidou Great Lakes Cosmology Workshop 8 Ohio State University, 01June 2007

More Related