Advanced search for the extension of unresolved TeV sources with - PowerPoint PPT Presentation

Advanced search for the extension of unresolved TeV sources with H.E.S.S. Markus Holler for the H.E.S.S. Collaboration ICRC 2017 Busan, 15th July 2017

2 Quantity Type (per pixel, telescope, or for array) Advanced Extension Active IACTs - Measurements Telescope Tracking array Source Position array Optical Efficiency ε telescope Transparency Coefficient array ■ New, more realistic simulation Camera Focus telescope approach (poster GA, contrib. 755) Trigger Settings telescope ▪ Simulating each observation run of a Live-Time fraction telescope Broken Pixels pixel data set PMT Gain pixel ▪ Using actual observation and Hi-Lo Ratio pixel instrument conditions Flatfield Coefficient pixel Night-Sky Background pixel ■ Run MC analysis on given data set Pointing Uncertainties telescope with corresponding analysis settings and assumed source spectrum ■ Use Sherpa for the extension fit M. Holler . Extension of unresolved TeV sources with H.E.S.S. . ICRC . 15th July 2017

3 Tests on Point-Like Sources ■ Focus on highly significant (> 100 σ ) sources with large S/B ratio ▪ PKS 2155-304: large, diverse data set ▪ Markarian 421: extreme zenith angle ( θ > 61° ) ■ Other sources tested as well, with identical outcome M. Holler . Extension of unresolved TeV sources with H.E.S.S. . ICRC . 15th July 2017

4 PKS 2155-304 ■ Detection significance: 125 σ ■ S/B ratio: 6.9 ■ Source appears point-like ■ Extension upper limits (2D Gaussian width): ▪ 13.7’’ (1 σ ) ▪ 23’’ (3 σ ) M. Holler . Extension of unresolved TeV sources with H.E.S.S. . ICRC . 15th July 2017

5 Markarian 421 ■ Detection significance: 196 σ ■ S/B ratio: 35 ■ No hints of systematics despite extremely large zenith angle ■ Extension upper limits (2D Gaussian width): ▪ 23.4’’ (1 σ ) ▪ 33.5’’ (3 σ ) ■ Factor of ~ 3 below the currently most constraining size limit of any TeV source! M. Holler . Extension of unresolved TeV sources with H.E.S.S. . ICRC . 15th July 2017

6 Checking Unresolved Sources ■ New quality of extension measurements in VHE gamma-ray astronomy ■ Search for extensions well below instrument PSF possible, down to ≤ 40’’ ■ Several to be checked, up to now one studied in detail M. Holler . Extension of unresolved TeV sources with H.E.S.S. . ICRC . 15th July 2017

7 Checking Unresolved Sources ■ New quality of extension measurements in VHE gamma-ray astronomy ■ Search for extensions well below instrument PSF possible, down to ≤ 40’’ ■ Several to be checked, up to now one studied in detail M. Holler . Extension of unresolved TeV sources with H.E.S.S. . ICRC . 15th July 2017

8 Checking Unresolved Sources ■ New quality of extension measurement in VHE gamma-ray astronomy ■ Search for extensions well below instrument PSF possible, down to ≤ 40’’ Albert et al. (2008) ■ Several to be checked, up to now one studied in detail ■ Limits on the Crab Nebula up to now: ▪ < 1.5’ for E < 10 TeV (HEGRA) ▪ < 2.2’ for E > 500 GeV (MAGIC I) M. Holler . Extension of unresolved TeV sources with H.E.S.S. . ICRC . 15th July 2017

9 Crab Nebula, E > 700 GeV ■ Detection significance 137 σ ■ S/B ratio 58 ■ Highly incompatible with point-source PSF M. Holler . Extension of unresolved TeV sources with H.E.S.S. . ICRC . 15th July 2017

10 Measuring the Crab Extension ■ Quote: Do your crabs measure greatcrabgear.com up? Even the most careful measurement is only as good as the gauge you use... and an inaccurate gauge can result in a steep fine for keeping undersize crabs. Gauges can be inaccurate for a number of reasons. ■ Ok fine, we now believe our gauge… and use Sherpa for the measurement itself (convolving PSF with different 2D Gaussian widths and checking LogLikelihood) M. Holler . Extension of unresolved TeV sources with H.E.S.S. . ICRC . 15th July 2017

11 ■ Extension TS = 83 (~ 9 σ ) ■ Best-fit Gaussian width: (52.2 ± 2.9 stat ± 7.8 sys )’’ M. Holler . Extension of unresolved TeV sources with H.E.S.S. . ICRC . 15th July 2017

12 H.E.S.S. Crab ICRC 2017 M. Holler . Extension of unresolved TeV sources with H.E.S.S. . ICRC . 15th July 2017

13 MWL Comparison M. Holler . Extension of unresolved TeV sources with H.E.S.S. . ICRC . 15th July 2017

14 MWL Comparison M. Holler . Extension of unresolved TeV sources with H.E.S.S. . ICRC . 15th July 2017

UV 15 X-rays VHE M. Holler . Extension of unresolved TeV sources with H.E.S.S. . ICRC . 15th July 2017

16 Energy Dependency M. Holler . Extension of unresolved TeV sources with H.E.S.S. . ICRC . 15th July 2017

17 Model vs. Data ■ Used updated model from Kennel & Coroniti, assuming magnetisation parameter of 0.01 ■ r TS = 0.15 pc (in line with newer measurements) ■ Observed extension can be well reproduced M. Holler . Extension of unresolved TeV sources with H.E.S.S. . ICRC . 15th July 2017

18 Conclusions ■ Reached new quality of extension measurements in VHE gamma-ray astronomy ■ Crab Nebula resolved at VHE energies for the first time ■ Gaussian width: (52.2 ± 2.9 stat ± 7.8 sys )’’ ■ TeV IC nebula larger than synchrotron X-ray one ■ arXiv identifier: 1707.04196 M. Holler . Extension of unresolved TeV sources with H.E.S.S. . ICRC . 15th July 2017

19 Backup M. Holler . Extension of unresolved TeV sources with H.E.S.S. . ICRC . 15th July 2017

20 Likelihood Profiles M. Holler . Extension of unresolved TeV sources with H.E.S.S. . ICRC . 15th July 2017

21 Year-by-Year Stability M. Holler . Extension of unresolved TeV sources with H.E.S.S. . ICRC . 15th July 2017

22 Termination Shock Radius ■ Inner ring corresponding to ~ 15.6 arcsec (see e.g. Ng. & Romani 2007) ■ For an assumed distance of 2 kpc: r TS = 0.15 pc M. Holler . Extension of unresolved TeV sources with H.E.S.S. . ICRC . 15th July 2017