# Presentation: 652217

## Overview of Analyzing GLAST Data

**David Band **
**(GLAST SSC—GSFC/UMBC)**** **

## The Goal of Today’s Presentation

**Last meeting we presented details on the definition and development of the Standard Analysis Environment (SAE).**
**Definition by a joint LAT-GSSC working group**
**Development managed by the LAT team with major GSSC participation**
**Supplements and is compatible with FTOOLS**
**Will also analyze GBM burst data with the addition of two GBM-specific tools**
**Today we focus on the methods underlying the SAE.  We also present the relationship between the SAE and the standard FTOOLS.**
**In the future we will address the user interface and the documentation, and arrange for the Users’ Committee to beta test the tools.**

## Data Analysis Issues

**The PSF is large at low energy, small at high energy.  **
**With the LAT’s large effective area, many sources will be detected; their PSFs will merge at low energy.**
**Analysis is inherently 3D—2 spatial and 1 spectral (& users are interested in temporal!)**
**For a typical analysis the source model must include**
**All point sources within a few PSF lengths of the region of interest**
**Diffuse sources (e.g., supernova remnants)**
**Diffuse Galactic emission (modeled)**
**Diffuse extragalactic emission**
**Sources are defined by position, spectra, and perhaps time history. Initial values may be extracted from the point source catalog that will be compiled by the LAT team.**
**The source model will have many parameters.  In an analysis some will be fitted, some will be fixed.**

## Data Analysis Issues-II

**The instrument response (PSF, effective area, energy resolution) will most likely be a function of energy, angle to the LAT normal, conversion layer (the front or back of the LAT), and the electron-positron vertex angle.  The IRF may also depend on the charged particle background resulting from the geomagnetic latitude, Solar cycle phase, etc.**
**The LAT will usually survey the sky.  Therefore a source will be observed at different instrument orientations.**
**Pointed observations will keep the source of interest within 30° of normal.**

## Observables

**The observables for a photon are:**
**Apparent energy**
**Apparent origin in sky coordinates (2 observables)**
**Apparent origin in instrument coordinates (2 observables)**
**Time**
**Front vs. back of LAT**
**Other detailed information from the LAT (e.g., the vertex angle between the electron-positron pair)**
**	****Note that with aspect information—where the instrument was pointed as a function of time—there is a redundancy among the time and the apparent origins in sky and instrument coordinates. **
**Therefore, a very large data space results.  Even with 10****5**** counts, this data space will be sparsely populated.**

## Planned Basic Analysis Strategy

**We plan to detect sources, determine source intensities, fit spectral parameters, set upper limits, etc., using the likelihood ******** of the observed counts given a source model.**
**Burst, pulsar analysis will take advantage of the source’s temporal variations.**
**Today methodology is the focus, but a schematic of the SAE architecture is helpful for context.**

## Schematic of SAE

- Pulsar
- ephem. (D4)

- Level 1 (D1)

- LAT Point source
- catalog (D5)

- Interstellar em.
- model (U5)

- Pointing/livetime
- history (D2)

- Astron.
- catalogs (D6)

- Level 0.5

- IRFs (D3)

- Alternative source for testing high-level analysis

- Alternative for making additional cuts on already-retrieved event data

- Pt.ing/livetime
- simulator (O1)

- Observation
- simulator (O2)

- Pt.ing/livetime
- extractor (U3)

-  Data sub-
- selection (U2)

- Data extract
- (U1)

- Exposure
- calc. (U4)

- Likelihood (A1)

- Map gen(U6)

- Src. ID (A2)

- Event
- display (UI1)

- Pulsar
- profiles (A3)1

- Catalog
- Access (U9)

- Pt.ing/livetime
- extractor (U3)

- Pulsar phase
- assign (U12)

- Pulsar period
- search (A4)

- GRB spectral-temporal
- modeling (A10)

- Source model
- def. tool (U7)

- Arrival time
- correction (U10)

- GRB temporal
- analysis (A7)2

- GRB LAT DRM
- gen. (U14)

- GRB spectral
- analysis (A8)2

- GRB event
- binning (A5)

- GRB unbinned
- spectral analysis (A9)

- GRB visual-
- ization (U13)

- IRF visual-
- ization (U8)

- Ephemeris
- extract (U11)

- GRB rebinning
- (A6)2

- Note that some details have changed

## Data Extraction

- Pulsar
- ephem. (D4)

- Level 1 (D1)

- LAT Point source
- catalog (D5)

- Interstellar em.
- model (U5)

- Pointing/livetime
- history (D2)

- Astron.
- catalogs (D6)

- Level 0.5

- IRFs (D3)

- Alternative source for testing high-level analysis

- Alternative for making additional cuts on already-retrieved event data

- Pt.ing/livetime
- simulator (O1)

- Observation
- simulator (O2)

- Pt.ing/livetime
- extractor (U3)

-  Data sub-
- selection (U2)

- Data extract
- (U1)

- Exposure
- calc. (U4)

- Likelihood (A1)

- Map gen(U6)

- Src. ID (A2)

- Event
- display (UI1)

- Pulsar
- profiles (A3)1

- Catalog
- Access (U9)

- Pt.ing/livetime
- extractor (U3)

- Pulsar phase
- assign (U12)

- Pulsar period
- search (A4)

- GRB spectral-temporal
- modeling (A10)

- Source model
- def. tool (U7)

- Arrival time
- correction (U10)

- GRB temporal
- analysis (A7)2

- GRB LAT DRM
- gen. (U14)

- GRB spectral
- analysis (A8)2

- GRB event
- binning (A5)

- GRB unbinned
- spectral analysis (A9)

- GRB visual-
- ization (U13)

- IRF visual-
- ization (U8)

- Ephemeris
- extract (U11)

- GRB rebinning
- (A6)2

- Swap in simulated data

## Likelihood

- Pulsar
- ephem. (D4)

- Level 1 (D1)

- LAT Point source
- catalog (D5)

- Interstellar em.
- model (U5)

- Pointing/livetime
- history (D2)

- Astron.
- catalogs (D6)

- Level 0.5

- IRFs (D3)

- Alternative source for testing high-level analysis

- Alternative for making additional cuts on already-retrieved event data

- Pt.ing/livetime
- simulator (O1)

- Observation
- simulator (O2)

- Pt.ing/livetime
- extractor (U3)

-  Data sub-
- selection (U2)

- Data extract
- (U1)

- Exposure
- calc. (U4)

- Likelihood (A1)

- Map gen(U6)

- Src. ID (A2)

- Event
- display (UI1)

- Pulsar
- profiles (A3)1

- Catalog
- Access (U9)

- Pt.ing/livetime
- extractor (U3)

- Pulsar phase
- assign (U12)

- Pulsar period
- search (A4)

- GRB spectral-temporal
- modeling (A10)

- Source model
- def. tool (U7)

- Arrival time
- correction (U10)

- GRB temporal
- analysis (A7)2

- GRB LAT DRM
- gen. (U14)

- GRB spectral
- analysis (A8)2

- GRB event
- binning (A5)

- GRB unbinned
- spectral analysis (A9)

- GRB visual-
- ization (U13)

- IRF visual-
- ization (U8)

- Ephemeris
- extract (U11)

- GRB rebinning
- (A6)2

**Data in**

## GRB Tools

- Pulsar
- ephem. (D4)

- Level 1 (D1)

- LAT Point source
- catalog (D5)

- Interstellar em.
- model (U5)

- Pointing/livetime
- history (D2)

- Astron.
- catalogs (D6)

- Level 0.5

- IRFs (D3)

- Alternative source for testing high-level analysis

- Alternative for making additional cuts on already-retrieved event data

- Pt.ing/livetime
- simulator (O1)

- Observation
- simulator (O2)

- Pt.ing/livetime
- extractor (U3)

-  Data sub-
- selection (U2)

- Data extract
- (U1)

- Exposure
- calc. (U4)

- Likelihood (A1)

- Map gen(U6)

- Src. ID (A2)

- Event
- display (UI1)

- Pulsar
- profiles (A3)1

- Catalog
- Access (U9)

- Pt.ing/livetime
- extractor (U3)

- Pulsar phase
- assign (U12)

- Pulsar period
- search (A4)

- GRB spectral-temporal
- modeling (A10)

- Source model
- def. tool (U7)

- Arrival time
- correction (U10)

- GRB temporal
- analysis (A7)2

- GRB LAT DRM
- gen. (U14)

- GRB spectral
- analysis (A8)2

- GRB event
- binning (A5)

- GRB unbinned
- spectral analysis (A9)

- GRB visual-
- ization (U13)

- IRF visual-
- ization (U8)

- Ephemeris
- extract (U11)

- GRB rebinning
- (A6)2

**Data in**

## Pulsar Tools

- Pulsar
- ephem. (D4)

- Level 1 (D1)

- LAT Point source
- catalog (D5)

- Interstellar em.
- model (U5)

- Pointing/livetime
- history (D2)

- Astron.
- catalogs (D6)

- Level 0.5

- IRFs (D3)

- Alternative source for testing high-level analysis

- Alternative for making additional cuts on already-retrieved event data

- Pt.ing/livetime
- simulator (O1)

- Observation
- simulator (O2)

- Pt.ing/livetime
- extractor (U3)

-  Data sub-
- selection (U2)

- Data extract
- (U1)

- Exposure
- calc. (U4)

- Likelihood (A1)

- Map gen(U6)

- Src. ID (A2)

- Event
- display (UI1)

- Pulsar
- profiles (A3)1

- Catalog
- Access (U9)

- Pt.ing/livetime
- extractor (U3)

- Pulsar phase
- assign (U12)

- Pulsar period
- search (A4)

- GRB spectral-temporal
- modeling (A10)

- Source model
- def. tool (U7)

- Arrival time
- correction (U10)

- GRB temporal
- analysis (A7)2

- GRB LAT DRM
- gen. (U14)

- GRB spectral
- analysis (A8)2

- GRB event
- binning (A5)

- GRB unbinned
- spectral analysis (A9)

- GRB visual-
- ization (U13)

- IRF visual-
- ization (U8)

- Ephemeris
- extract (U11)

- GRB rebinning
- (A6)2

**Data in**

## Catalog Tools

- Pulsar
- ephem. (D4)

- Level 1 (D1)

- LAT Point source
- catalog (D5)

- Interstellar em.
- model (U5)

- Pointing/livetime
- history (D2)

- Astron.
- catalogs (D6)

- Level 0.5

- IRFs (D3)

- Alternative source for testing high-level analysis

- Alternative for making additional cuts on already-retrieved event data

- Pt.ing/livetime
- simulator (O1)

- Observation
- simulator (O2)

- Pt.ing/livetime
- extractor (U3)

-  Data sub-
- selection (U2)

- Data extract
- (U1)

- Exposure
- calc. (U4)

- Likelihood (A1)

- Map gen(U6)

- Src. ID (A2)

- Event
- display (UI1)

- Pulsar
- profiles (A3)1

- Catalog
- Access (U9)

- Pt.ing/livetime
- extractor (U3)

- Pulsar phase
- assign (U12)

- Pulsar period
- search (A4)

- GRB spectral-temporal
- modeling (A10)

- Source model
- def. tool (U7)

- Arrival time
- correction (U10)

- GRB temporal
- analysis (A7)2

- GRB LAT DRM
- gen. (U14)

- GRB spectral
- analysis (A8)2

- GRB event
- binning (A5)

- GRB unbinned
- spectral analysis (A9)

- GRB visual-
- ization (U13)

- IRF visual-
- ization (U8)

- Ephemeris
- extract (U11)

- GRB rebinning
- (A6)2