Status report on Light Simulator

Claudia Cecchi Francesca Marcucci

Monica Pepe

Software meeting Udine

January 30-31 2003

Why the light simulator…

Fast simulation of the sky map seen by GLAST to be used starting point for statistical analysis.

Generation of a photon list, with photons distributed randomly,

according to PSF, AS and ED distributions (determination of

the true and measured energy, the incidence angle, the true and

the measured position and the arrival time of the photons)

The code (C++) is working under windows and under Linux

Next step: generation of a database with photon’s information available on the web.

Input: map of the galactic background (Egret or Galprop) Third Egret Catalogue with sources photon energy range (0.1 – 100 GeV) region of the sky (-90° - 90°, -180° - 180°) orbit or fix time

Simulation: extragalactic background

Output: FITS-images of sky-map view and sources

galactic background

sources

exposure

convolution

Bkg-differential flux C (P0) ( cm-2 t-1-1) = all contributions

map of the sky in small regions of 0.5° x 0.5° without detector effects convolution of our result with the SA, PSF and ED.

 

Convolution with PSF, SA and EDBackground and Sources

For Bkg:= 2.1I0 =C (P0) • =dl · db · cos(b)

In each pixel P0:

D(E) = 0-60° E(θ,E) · I0 •E –dθ

Generation of a photon list

N = E D(E)

Each randomly distributed in the map with:

random energy Etrue[Emin, Emax] according to D(E)

inclination angle θ distributed according to E(θ, Etrue)

Emeas obtained using the function ED(Etrue , Emeas )

angular distance, ρ, from origin point P0 (l0, b0) consistent with PSF( , Etrue )

final position of each photon is P1 (l1, b1) obtained considering that the total angular distance from P0 is

New w.r.t. the previous version

Calculation of Sun/Moon positions and angle with respect to SC

Mcllwain’s parameters calculation with GEOPAK

New Exposure improved SC latitude and longitude calculation

New PSF from S. Digel and J. Norris, depending on the incidence angle and on conversion point in the detector, front (2.5% X0 – 12 layers), back (25% X0 – 4 layers).

Faint sources, model from Stecker and Salomon ’96; flux (E> 100 MeV) between 10-10 and 10-7 photons cm-2 s-1.

Arrival photon’s time : the number of generated photons follows a Poissonian distribution

Spacecraft and orbit parameters

Output: two tables Photon parameters

FITS-images of sky-map view and sources

Photon Time

Arrival photon’s time : the number of generated photons follows a Poissonian distribution

Time interval from zero to T where T is the minimun interval of time with Nph different from zero

T divided into n steps t of 100 s (GLAST dead time)

For each step calculate the probability P that a photons is in t

if P < Rate t timephoton = n t

PSF comparison

OLD PSF (S. Ritz) is assumed to be a single gaussian, does not depend on the incidence angle and is averaged over converter thickness

NEW PSF (S.Digel & J.Norris) is the sum of two

gaussians, 1(95%) 2 (68%), depends on the incidence angle and on the conversion point (Front or Back)

Old PSF

New PSF

Exposure 827 orbits

2.2e+10 2.4e+10 2.6e+10 2.8e+10

Long (deg)

Lat

(deg)

StartDate EndDate SCposX SCposY SCposZ LatRaZ LatDecZs s Km Km Km deg deg

30 60 6920 200 109 1,33 -29,460 90 6910 400 218 1,43 -28,690 120 6890 600 326 1,53 -27,7

LatRaX LatDecX RaZ DecZ SCmode Tlive ins SAAdeg deg deg deg s12,2 -35,9 0,11 0,9 1 27 012,5 -36,8 0,22 1,8 1 27 012,7 -37,7 0,33 2,7 1 27 0

SClon SClat SCalt SunRA SunDEC MoonRA MoonDECdeg deg km deg deg deg deg-108 0,91 550 4,9 -0,4 4,45 -0,41-100 1,81 550 4,9 -0,4 4,45 -0,41-107 2,72 550 4,9 -0,4 4,45 -0,41

Emeas Etrue ED(Etrue) Theta RAtrue DecTrue RAmeasGeV GeV GeV deg deg deg deg0,09 0,11 0,1 26 275 -27,7 2790,26 0,19 0,08 14 275 -27,7 2730,16 0,15 0,09 16,1 275 -27,7 274

DecMeasphoton time time DeadTimeZenith angleEarth Azimut angledeg s s s deg deg-28,6 54,4 90 0 62 75,1-26,6 112 150 0 65,6 77,8-29,9 117 150 0 65,6 77,8

SC x SC y SC z B LLat GeoMagLong Geomagkm km km gauss Earth radii deg deg

5630 -3570 -1890 3750 146 1,48 5,245880 -3230 -1710 3820 142 1,48 5,245880 -3230 -1710 3820 142 1,48 5,24

All sky + sources 0.1-30 GeV827 orbits bg with PSF

Bkg + sources sources

Previous version

All sky + sources 0.1-30 GeV827 orbits bg with PSF

Bkg + sources sources

New version

Bkg + sourcessources

Long (deg)

Lat

(deg)

Lat

(deg)

Long (deg)

3C279-60 sky + sources 0.1-30GeV Bg with PSF 827 orbits

Previous version

New version ANGLE- PSF total3C279-60 sky + sources 0.1-30GeV Bg with PSF (no Front-Back) 827 orbits

Bkg + sources sources

Bkg + sources sources

Long (deg)

Lat

(deg)

Lat

(deg)

Long (deg)

3C279-60 sky + sources 0.1-30GeV Bg with PSF 827 orbits

New version

0 20 40 60 0 20 40 50

Lat

(deg)

Lat

(deg)

3010

3C279 region seen by EGRET

x 2.0 E05

CONCLUSIONS and PERSPECTIVES

Last version is not running under Linux, problems with GEOPAK, under investigation

Simulation of 1 year of GLAST data tacking generation of a photon’s DB (under Linux)

First version of a note has been sent to S. Digel, new version with modifications ready for next week

Implementation of an algorithm to retrieve photon information from pixel index (Gino)

Implementation of the simulator in Gaudi as a standalone package (in collaboration with Toby)

Possibility of studying the PSF from Gleam to be used in the simulator (discussion)

255 sources from the Third Egret Catalogue

3EG J0010+7309 2.56 73.17 119.92 10.54 1.8464610E+00 4.8522080E+02 1.6500180E-103EG J0038-0949 9.74 -9.82 112.69 -72.44 2.7042760E+00 1.5626760E+02 5.3436390E-103EG J0118+0248 19.6 2.81 136.23 -59.36 2.6336160E+00 1.7153680E+02 2.3813020E-103EG J0130-1758 22.7 -17.97 169.71 -77.11 2.5050740E+00 1.9170150E+02 3.2784570E-103EG J0159-3603 29.84 -36.06 248.89 -73.04 2.8922490E+00 1.2666270E+02 8.0606110E-103EG J0204+1458 31.11 14.97 147.95 -44.32 2.2321450E+00 2.6488440E+02 1.3811020E-103EG J0210-5055 32.58 -50.93 276.1 -61.89 1.9899620E+00 2.8397580E+02 8.8435840E-103EG J0215+1123 34 11.38 153.75 -46.37 2.0280930E+00 6.0997420E+02 8.8540930E-123EG J0222+4253 35.7 42.9 140.22 -16.89 2.0100220E+00 4.1280090E+02 9.5417540E-113EG J0229+6151 37.32 61.86 134.2 1.15 2.2863630E+00 2.3071570E+02 5.4674250E-10

Source name AR DEC Long. Lat. Spectral index Standard energy Flux @st.energy

Elliptic orbit defined by the following parameters:

·         a semi-major axis of the ellipse (distance of the orbit from the Earth 550 Km)·         e eccentricity (is set to zero, because we assume a circular orbit)·         P epoch (time of transit to the perigee)·         T period ( 5739 s )·         anomaly (the angle between the perigee and the point from where we start to calculate the orbit)·         i inclination of the orbit with respect to the terrestrial equator (28.5°)·         (t) the orientation of the semi-major axis of the ellipse·         R rocking (35°).  Simulated with a geometrical approach by steps of 30 ( 2°) assuming that within each step the parameters are constant. Output total exposure calculated as the sum over all the steps.

The orbit

Differential flux of photons from diffuse extra galactic background described (Skreekumer, 1997) as:

[1]

(photons · cm -2· s -1 · GeV -1· sr -2)

Total contribution of the extra galactic background obtained by the integration of (1) between Emin and Emax

taken into account only if |b| > 15°.

 

Diffuse extra galactic background

2.1-2.16- E · 0.451 · 10 · 7.3dE

dN

Galprop simulates the gamma ray background taking into account: neutral pion decay; bremsstrahlung; inverse Compton scattering.

Galprop produces FITS file containing 24 imagesin the energy range from 0.001 to 104 GeV

The gamma ray galactic background

EGRET map measured between 0.1 and 30 GeV

First approximation: sources point-like located at an infinite distance Intensity of photons:

(photons cm -2 s -1 GeV -1 )

Sources information: localization, and I0 from Third Egret Catalogue.

EIEI 0)(

Sources

Observation time fixed:  E(θ, E) = SA(θ, E) t cos θ

Exposure

r0

r

Observation time not fixed:E(θ, E) = r0 E0 (θ, E) · ε

E0 (θ, E) = SA(θ, E) • t ε = 90%Zenith