1 / 24

Search of Optimized Cuts for Pulsar Detection

Search of Optimized Cuts for Pulsar Detection. Andrea Caliandro - INFN Bari DC2 CloseOut May 31 2006 Goddard Space Flight Center. Summary. Have been searched the best ROI & Energy band that maximize the probability for a point source to be periodic Parameter considered Sky position

yoko
Download Presentation

Search of Optimized Cuts for Pulsar Detection

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. Search of Optimized Cuts for Pulsar Detection Andrea Caliandro - INFN Bari DC2 CloseOut May 31 2006 Goddard Space Flight Center

  2. Summary • Have been searched the best ROI & Energy band that maximize the probability for a point source to be periodic • Parameter considered • Sky position • Flux • Observation Time • For this work a sample of 900 pulsars and diffuse emission have been simulated 15 times • Each simulation is characterized by a value of flux attributed to all the pulsars and by the Observation time • PSR flux: 1e-6, 0.3e-6, 1e-7, 0.3e-7, 1e-8 ph/cm2s • ObsTime: 1 Week, 2Week, 4Week • Finally this search has been tested on the DC2 sky • All the radio loud PSR in the pulsarDB have been analyzed

  3. Sky Simulation Lateral Center Center Lateral AntiCenter (2,-2)(6, 2)(10, 6) • Is taken into account the strip of sky |b|<10 • This strip is subdivided in 9 regions • Center2-2, Center2_6, Center 6_10 • Lateral2-2, Lateral2_6, Lateral6_10 • Anticenter2-2, Anticenter2_6, Anticenter6_10 • In each region there are 100 psr uniformly distributed • In this way the statistic is the same for each region • This is not a simulation of a real pulsar population • Diffuse emission simulation • Galactic diffuse emission • Extragalactic diffuse emission • gtorbsim parameter • Pointing strategy: SLEWING • Rocking angle = 35°

  4. Pulsar Simulation • 2 peaks pulse shape • Phase position, width and height are random • There is just the constrain for the peak distance to be more than 0.3 phase • P = 1s, Pdot = 0s/s, Pddot = 0s/s2 • These choices are just to simplify the analysis, but do not affect the result • b = 1 • E0 = 10GeV • g is a random number distributed as e gaussian N(1.4, 0.2) • These choices are based on the data of the Gamma-ray Pulsars (Nel, De Jager 1995) and how I have chosen the Energy band to investigate • See next slide (Nel and De Jager,1995) ScienceTools: CelestialSource/Pulsar

  5. Base Analysis Histogram by Cuts Radius (Degrees) ROI: Disk with Radius R centerd on the source (gtselect) Binning: 0.25° 2° 0.50° 3° 0.75° 4° 1° 6° 1.5° 8° Emin (MeV) Energy cut: Energy band from the selected Emin value to the maximum observable Energy (200GeV) (gtselect) Binning: 20 MeV 50 MeV 100 MeV 200 MeV 400 MeV 600 MeV 1 GeV 10 GeV Emin (keV) • For each source are selected a series of ROI and Energy cut • For each of these selection are calculated the Htest and the relative probability (PHtest)

  6. Htest Algorithm For N>=100 m=20 For N<100 m=N/5 Probability that H could be greater of the found value P(>H) For H<=23 For 23<H<50 For H>=50 For N < 100 If H>=30 For N < 20 If H>=25 For N < 10: (De Jager et al. 1989)

  7. Histograms & Distributions • From the Single Pulsar Histograms • Htest & PHtest histograms • Are obtained, for each value of PSR flux & Observation Time (i.e. for each simulation) and relative to each Region of the sky • Mean Htest & PHtest Histograms • Simply the normalized sum of the Single Pulsar Histogram • Distribution of the Max Htest Values • Taken by each Htest Single Pulsar Histogram • See next slides • Distribution of the Minimum PHtest Values • Taken by each PHtest Single Pulsar Histogram • See next slides • Cut Distribution for which Htest is Max • From each Single Pulsar Histogram are taken the cuts relative to the max value • See next slides • Cut Distribution for which PHtest is Min • From each Single Pulsar Histogram are taken the cuts relative to the min value • See next slides Single Pulsar Histograms PHtest Htest Htest This two histograms are relative to PSRflux=1e-7 ObsTime=4Weeks Region=Lateral2-2 PHtest

  8. Htest Center2_6 Center2-2 Center6_10 AntiCenter2_6 AntiCenter2-2 AntiCenter6_10 Lateral2_6 Lateral2-2 Lateral6_10 Center2_6 Center2-2 Center6_10 AntiCenter2_6 AntiCenter6_10 AntiCenter2-2 AllRegions Lateral2_6 Lateral6_10 Lateral2-2 AllRegions consider the Regions all together -all 900 psr The plots showed in this slide are relative to PSRflux=1e-7 ObsTime=4Weeks • Htest Max Value Distributions • Cut Distribution for which Htest is Maximum

  9. Center2_6 Center2-2 Center6_10 AntiCenter2_6 AntiCenter2-2 AntiCenter6_10 • PHtest Min Value Distributions Lateral2_6 Lateral2-2 Lateral6_10 Center2_6 Center2-2 Center6_10 • Cut Distribution for which PHtest is Minimum AntiCenter2_6 AntiCenter6_10 AntiCenter2-2 AllRegions Lateral2_6 Lateral6_10 Lateral2-2 AllRegions consider the Regions all together -all 900 psr The plots showed in this slide are relative to PSRflux=1e-7 ObsTime=4Weeks PHtest

  10. Overview on All RegionsHtest Distributions (ObsTime = 4Weeks) Flux 1e-6 ph/cm^2 s Flux 1e-8 ph/cm^2 s Flux 1e-7 ph/cm^2 s Cut Distribution for which Htest is Maximum Htest Max Value Distribution • Cuts Distribution: • Decreasing the Flux • The distribution become more broad • The peak is displaced toward high Energy • Max Value Distribution: • Decreasing the Flux • The distribution is less broad • The peak is at lower values

  11. Overview on All RegionsHtest Plots vs Flux vs Fluence 1Week 2Weeks 4Weeks Htest Htest Flux (ph/cm^2s) Fluence (ph/cm^2) Emin (MeV) Emin (MeV) Flux (ph/cm^2s) Fluence (ph/cm^2) Radius (degree) Radius (degree) Flux (ph/cm^2s) Fluence (ph/cm^2) By Max value Distribution • Htest vs Flux and Fluence • Mean value of distribution • Errors bars: right and left RMS • Htest is proportional to the flux and the fluence By Cuts Distribution • Energy Cut Plots • Energy coordinate of the Peak of the distribution • Errors bars: right and left RMS respect to the Peak • Seems to converge towards Emin=200MeV • Radius Plots • Radius coordinate of the Peak of the distribution • Errors bars: right and left RMS respect to the Peak • The peaks increase toward 1.5°

  12. Overview on All RegionsPHtest Distributions (ObsTime = 4Weeks) Flux 1e-6 ph/cm^2 s Flux 1e-8 ph/cm^2 s Flux 1e-7 ph/cm^2 s Cut Distribution for which PHtest is Minimum PHtest Min Value Distribution This peak correspond to the case N>100 & H>50 (the best one) • Cuts Distribution: • The behavior is the same of Htest Cuts Distribution • But the positions of the peak aren’t the same of Htest Cuts Distribution This peak is due to the case N<100 & H>30 ( see slide 6 )

  13. Overview on All RegionsPHtest Plots vs Flux vs Fluence 1Week 2Weeks 4Weeks PHtest (log10) PHtest (log10) Flux (ph/cm^2s) Fluence (ph/cm^2) Emin (MeV) Emin (MeV) Flux (ph/cm^2s) Fluence (ph/cm^2) Radius (degree) Radius (degree) Flux (ph/cm^2s) Fluence (ph/cm^2) By Min value Distribution • PHtest vs Flux and Fluence • Mean value of distribution • Errors bars: standard RMS • There is a smooth step starting at 2E-2ph/cm2 ending at 3E-1ph/cm2 By Cuts Distribution • Energy Cut Plots • Energy coordinate of the Peak of the distribution • Errors bars: right and left RMS respect to the Peak • For low fluence is convenient to cut at Energy greater of 200MeV • For high fluence cut aren’t needed • Radius Plots • Radius coordinate of the Peak of the distribution • Errors bars: right and left RMS respect to the Peak • Radius decrease until 0.25°

  14. Diffuse Htest Diffuse Distribution example for the simulation with ObsTime = 4Weeks and psr Flux = 1e-6 • The described analysis has been performed on the Diffuse Data file alone • Related to each psr sky position, the Htest & PHtest histograms are builded • The Distributions are calculated in two different way • Absolute Calculation • The max value is taken from each Htest histogram • The min value is taken from each PHtest histogram • Relative Calculation • From the Htest and PHtest histograms is taken the value relative to the Best Cut for the corresponding pulsar Htest PHtest Absolute Calculation Relative Calculation

  15. PHtest with Diffuse line AllRegions Diffuse Absolute Calculation Diffuse Relative Calculation • Relative Calculation • The PHtest on the Diffuse is not constant but increase with the fluence • PHtest values under the dotted line means pulsar with good significance • above ~6E-2ph/cm2 the PHtest value of pulsar are all good • Absolute Calculation • The PHtest on the Diffuse is independent from the fluence • We can say that a source is a pulsar with good significance if log10(PHtest)<-2.5

  16. PHtest Center Regions Center2_6 Center6_10 Center2-2 over ~1E-1ph/cm2 the PHtest value of pulsar are all good

  17. PHtest Lateral Regions Lateral2_6 Lateral6_10 Lateral2-2 over ~4E-2ph/cm2 the PHtest value of pulsar are all good

  18. PHtest Anticenter Regions AntiCenter2_6 AntiCenter6_10 AntiCenter2-2 over ~5E-2ph/cm2 the PHtest value of pulsar are all good

  19. First Conclusions • Max Htest value in Cut Histogram not always correspond to Minimum PHtest value • Infact the distribution are different • See slide 10 & 12 • Cuts Distribution are too broad to determine a precice value for Energy cut and Radius of the ROI as function of the fluence and the position in the sky region • For low fluence are necessary Energy cut above 100 or 200MeV • For high fluence to have a good PHtest value is enough to take radius not greater than 1.5° or 2° • By the PHtest performed on the diffuse we can say that in first approximation a source is a pulsar with good significance if log10(PHtest)<-2.5 • We have also seen that the application of the best cut increase this value in function of the fluence

  20. DC2 Pulsar Analysis Center2-2 Center2_6 Center6_10 AntiCenter2-2 AntiCenter2_6 AntiCenter6_10 Lateral2-2 Lateral2_6 Lateral6_10 External • Best cuts have been searched for all the pulsar in the DC2pulsarDB • DC2pulsarDB and LATsourceCatalog have been compared • 40 pulsars have been found in the LATsourceCatalog • In this way we also obtain a flux estimation for these pulsars • Distribution of pulsar population in the sky • About 90% of the pulsar population is in the Central and Lateral Region with |b|<6 • A different analysis has been performed for pulsars with and without flux estimation

  21. DC2 psr with Flux estimation The best ROI radius for all pulsars but 3 is less than 2° Considering the threshold at log10(PHtest)=-2.5 we lost 6 pulsars Below 1ph/cm2 the Energy cut are broadly distributed from Emin=50MeV to Emin=1GeV Above 1ph/cm2 there is a concentration of pulsars without Energy cut

  22. Pulsar not in LAT catalog • Distribution of Cuts • Most of the pulsars have the best ROI radius <2° • and No Energy cut • Distribution of PHtest • There are 23 pulsars below the threshold of log10(PHtest)=-2.5 • 15 have the best possible value of the PHtest

  23. Some Light Curve Rad=8 Emin=200 Log(P)=-4.4 Nevt=30413 Rad=0.75 Emin=200 Log(P)=-6.8 Nevt=2098 Rad=0.5 Emin=50 Log(P)=-6.3 Nevt=100 Rad=0.25 Emin=20 Log(P)=-7.4 Nevt=158 Rad=0.75 Emin=100 Log(P)=-6.6 Nevt=2223 Rad=0.25 Emin=20 Log(P)=-2.9 Nevt=269 Rad=0.25 Emin=20 Log(P)=-7.4 Nevt=143 Rad=0.5 Emin=400 Log(P)=-2.6 Nevt=632 Maybe a trick of the simulators?

  24. Conclusions • Appling the search of the Energy cut and the ROI radius that minimize the PHtest value we have found 23 pulsars that aren’t in the LATsourceCatalog • The cut found are not standard cut • Most of the psr have a best radius <-2° • Most of the psr have not Energy cut • Maybe could be useful to build a Science Tools that make this search

More Related