Cosmology with the extragalactic gamma ray background
Download
1 / 10

Cosmology with the extragalactic gamma-ray background - PowerPoint PPT Presentation


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. CMBEGRB

Related searches for Cosmology with the extragalactic gamma-ray background

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha

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.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -

Presentation Transcript


Cosmology with the extragalactic gamma-ray background

Vasiliki PavlidouUniversity of Chicago


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


EGRB vs CMB

CMBEGRB

  • Origin: cosmologicalcosmologicaltruly diffuseunresolved point sources

  • Foregrounds:Milky WayMilky Way

  • Energies: ~ 2.7 K ~ 109eV (1GeV)

  • Spectrum:blackbodypower law

Vasiliki Pavlidou Great Lakes Cosmology Workshop 8 Ohio State University, 01June 2007


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


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


And now… cosmology

Vasiliki Pavlidou Great Lakes Cosmology Workshop 8 Ohio State University, 01June 2007


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


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


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


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


ad
  • Login