1 / 12

EBL Absorption Signatures in DC2 Data

EBL Absorption Signatures in DC2 Data. Jennifer Carson (SLAC) DC2 closeout meeting June 1, 2006. Motivation. How well can we measure EBL absorption in 55 days of data? How sure can we be that we are distinguishing intrinsic spectral breaks from absorption signatures?

stu
Download Presentation

EBL Absorption Signatures in DC2 Data

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. EBL Absorption Signatures in DC2 Data Jennifer Carson (SLAC) DC2 closeout meeting June 1, 2006

  2. Motivation • How well can we measure EBL absorption in 55 days of data? • How sure can we be that we are distinguishing intrinsic spectral breaks from absorption signatures? • Fit spectra with broken power law model + absorption. • Compare results to simple power law fits.

  3. Basic Procedure • v2 of catalog • 10° regions around LR’s 9 sources, 20° source regions • Only class A events • Diffuse components: extragalactic, galactic, high-energy residual, low-energy residual • Diffuse prefactors allowed to float in fits • All catalog point sources in FOV included (fixed PLs) • Broken power law model with EBL absorption (“BPLExpCutoff”): prefactor, 2 indices, break energy, Eabs, P1 •  = (E – Eabs) / P1 • Likelihood twice: DRMNGB for convergence, MINUIT for errors

  4. Example Fits bright blazar (BPL+EBL) bright blazar (BPL+EBL) galactic & EG residual background residual background faint blazar(PL)

  5. Kneiske Kneiske High-UV Primack Stecker BPL Results  BPL

  6. Kneiske Kneiske High-UV Primack Stecker BPL Results  BPL  PL

  7. BPL E0 (GeV) PL E0 (GeV) BPL Results vs. PL Results • PL E0 higher than BPL E0 for most sources • Intrinsic breaks can pull E0 to lower energies

  8. High-Redshift Sources • Found all sources with z > 2 in ASDC catalog (10) • ROI = 5°, source region = 15°

  9. High-Redshift Sources • Found all sources with z > 2 in ASDC catalog (10) • ROI = 5°, source region = 15° Can’t get good fits! (Despite hand-holding)

  10. Fit Comparison: Idea • Three types of fits: • Broken power law + fixed EBL absorption • Broken power law + no EBL absorption • Simple power law + floating EBL absorption • Four free parameters in each fit • Test statistic  goodness of fit

  11. Fit Comparison: Results • red: TSBPL+EBL – TSBPL • blue: TSBPL+EBL – TSPL+EBL • TS generally better for BPL+EBL vs. pure BPL • TS generally better for BPL+EBL vs. PL+EBL

  12. Conclusions • In < 2 months, difficult to constrain the EBL – no models ruled out • PL & BPL results are close, but BPL generally predicts higher E0 values • Especially difficult measure E0 for z > 2 sources • TS indicates that: • BPL+EBL better fit than PL+EBL • BPL+EBL better fit than pure BPL • High-energy residuals made finding E0 even harder • Future work • More data! What would a year of data tell us? • Automated search for flares + spectral analysis • Improve cuts to remove high-energy residual. • Need likelihood to converge reliably with correct errors.

More Related