1. The National Science FoundationThe Kavli Foundation AAS 211th meeting - Austin, TX Implications of Recent UHECR Data for Multi-Messenger Studies of Cosmic Accelerators Vasiliki Pavlidou University of Chicago

2. The National Science FoundationThe Kavli Foundation AAS 211th meeting - Austin, TX Why multi-messenger?

3. The National Science FoundationThe Kavli Foundation AAS 211th meeting - Austin, TX In Context: High-Energy Observations in the Next Decade GLAST: continuous full-sky coverage in GeV gamma rays Ground-based TeV telescopes (CTA/AGIS/HAWC): full sky accessible in TeV gamma rays, high angular resolution Neutrino telescopes (IceCube, KM3NeT): continuous full-sky coverage in TeV neutrinos Auger South + North: continuous full-sky coverage in UHECRs (+ photons, neutrinos) Auxiliary: radio, IR, optical, UV, X-ray Perks: LIGO, LISA

4. The National Science FoundationThe Kavli Foundation AAS 211th meeting - Austin, TX UHECR astronomy: some questions What makes the highest-energy particles in the universe? –progress from lower energies, different messengers? –progress from theory? Hadron vs lepton acceleration –progress with gamma-rays? –progress with neutrinos? Particle energy spectrum at source –progress with extrapolation? some of the expected unique UHECR contributions to the multi-messenger picture  now: add some UHECR data refine the puzzles

5. The National Science FoundationThe Kavli Foundation AAS 211th meeting - Austin, TX The UHECR Sky Cen A AGN

6. The National Science FoundationThe Kavli Foundation AAS 211th meeting - Austin, TX Correlation with AGN  AGN are the sources –What are the sources? –How do we find them at the one-event-per-source limit? Need multiple candidate source catalogs –Good southern sky coverage, complete, homogeneous (selected by physical property), with redshifts! What kind of catalogs? –By object type (e.g., starburst galaxies, BL Lacs, galaxy clusters, Seyferts, radio-loud AGN …) –By likely counterpart emission (gamma-ray sources, radio sources, neutrino sources…) Statistics of selection –Need at the same time less sky coverage, more hits Source identification at the single-event-per-source limit

7. The National Science FoundationThe Kavli Foundation AAS 211th meeting - Austin, TX The UHECR Sky

8. The National Science FoundationThe Kavli Foundation AAS 211th meeting - Austin, TX Where is the Virgo Cluster? Is deficit of events significant? Assuming the effect is real, what may be going on here? –Source ecology –Confinement –Propagation

9. The National Science FoundationThe Kavli Foundation AAS 211th meeting - Austin, TX The UHECR Sky Cen A doublet When should we expect the first UHECR source catalogue?

10. The National Science FoundationThe Kavli Foundation AAS 211th meeting - Austin, TX Multimessenger insight from other high-energy experiments How would one claim / measure point sources? –Claiming source significance: probability to get observed event excess as a fluctuation of the background –Claiming source flux: background model + source of flux F maximize the likelihood to obtain observed data Key input: model of background!

11. The National Science FoundationThe Kavli Foundation AAS 211th meeting - Austin, TX Complications specific to cosmic-ray astronomy Background –At highest energies: no cosmological background –Highest-E CR distribution anisotropic - sources cluster –Non-trivial to decide what expectations for events are if you take away one single source in a region with many candidate sources –Source density key Point Spread Function –Not a function of the instrument, B-field dependent, largely unknown –Different for different parts of the sky

12. The National Science FoundationThe Kavli Foundation AAS 211th meeting - Austin, TX The inverse multi-messenger problem What are the doublets telling us? –We have 4 sources correlated with 8 events within 3.2 degrees. –Data collected with the equivalent of ~ 1 year of full-Auger exposure –Auger south ~ complete –if real sources, in 1yr we should have 8±3 events from them –Attack most-promising objects with multi-messenger campaigns Complications –If sources are bursting rather than steady, we are stuck with studying sources in quiescence due to time spreads

13. The National Science FoundationThe Kavli Foundation AAS 211th meeting - Austin, TX Outlook UHECR Astronomy Identification of source population at the 1-event-per-source limit -> homogeneous, complete, property selected catalogs of candidate sources Within ~ 1 year: Is there a Virgo problem? What are the most likely southern sky sources? (triplets) Statistically significant detection of point sources, spectra: challenging, need much better statistics, Auger North In another year: meaningful constraints on source density, we will know how long we have to wait

14. The National Science FoundationThe Kavli Foundation AAS 211th meeting - Austin, TX