ebl absorption signatures in dc2 data
DESCRIPTION
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? - PowerPoint PPT PresentationTRANSCRIPT
![Page 1: EBL Absorption Signatures in DC2 Data](https://reader035.vdocument.in/reader035/viewer/2022062517/56813c41550346895da5be06/html5/thumbnails/1.jpg)
EBL Absorption Signatures in DC2 Data
Jennifer Carson (SLAC)
DC2 closeout meeting
June 1, 2006
![Page 2: EBL Absorption Signatures in DC2 Data](https://reader035.vdocument.in/reader035/viewer/2022062517/56813c41550346895da5be06/html5/thumbnails/2.jpg)
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.
![Page 3: EBL Absorption Signatures in DC2 Data](https://reader035.vdocument.in/reader035/viewer/2022062517/56813c41550346895da5be06/html5/thumbnails/3.jpg)
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
![Page 4: EBL Absorption Signatures in DC2 Data](https://reader035.vdocument.in/reader035/viewer/2022062517/56813c41550346895da5be06/html5/thumbnails/4.jpg)
Example Fits
bright blazar (BPL+EBL)
faint blazar(PL)
residual background
residual background
bright blazar (BPL+EBL)
galactic & EG
![Page 5: EBL Absorption Signatures in DC2 Data](https://reader035.vdocument.in/reader035/viewer/2022062517/56813c41550346895da5be06/html5/thumbnails/5.jpg)
BPL Results
BPL KneiskeKneiske High-UVPrimackStecker
![Page 6: EBL Absorption Signatures in DC2 Data](https://reader035.vdocument.in/reader035/viewer/2022062517/56813c41550346895da5be06/html5/thumbnails/6.jpg)
BPL Results
BPL PL
KneiskeKneiske High-UVPrimackStecker
![Page 7: EBL Absorption Signatures in DC2 Data](https://reader035.vdocument.in/reader035/viewer/2022062517/56813c41550346895da5be06/html5/thumbnails/7.jpg)
BPL Results vs. PL Results
• PL E0 higher than BPL E0 for most sources
• Intrinsic breaks can pull E0 to lower energies
BP
L E
0 (
Ge
V)
PL E0 (GeV)
![Page 8: EBL Absorption Signatures in DC2 Data](https://reader035.vdocument.in/reader035/viewer/2022062517/56813c41550346895da5be06/html5/thumbnails/8.jpg)
High-Redshift Sources• Found all sources with z > 2 in ASDC catalog (10)• ROI = 5°, source region = 15°
![Page 9: EBL Absorption Signatures in DC2 Data](https://reader035.vdocument.in/reader035/viewer/2022062517/56813c41550346895da5be06/html5/thumbnails/9.jpg)
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)
![Page 10: EBL Absorption Signatures in DC2 Data](https://reader035.vdocument.in/reader035/viewer/2022062517/56813c41550346895da5be06/html5/thumbnails/10.jpg)
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
![Page 11: EBL Absorption Signatures in DC2 Data](https://reader035.vdocument.in/reader035/viewer/2022062517/56813c41550346895da5be06/html5/thumbnails/11.jpg)
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
![Page 12: EBL Absorption Signatures in DC2 Data](https://reader035.vdocument.in/reader035/viewer/2022062517/56813c41550346895da5be06/html5/thumbnails/12.jpg)
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.