You are viewing an old version of this page. View the current version.

Compare with Current View Page History

Version 1 Next »

Introduction

With Pass 8, event_types are introduced.  Even though these are essentially a generalization of conversion_type (i.e., front vs back converting events) in that the the event types partition the data into distinct subclasses which have their own effective area, point spread, and energy dispersion functions, in Pass 8, there are alternative partitions for a given class.  For example, the Pass 8 SOURCE class selection can be partitioned in one of three ways:  into front vs back converting events,  into events belonging to one of 4 "PSF" subclasses, or into events belonging to one of 4 "EDISP" classes.  The Pass 8 event classes and types descriptions and usage are described in the following links.

Pass 8 Descriptions

Changes to gt-tools

  • gtobssim:

    • The event type partition has been added as an option for gtobssim.  Examples for P8_SOURCE_V5:

      gtobssim irfs=P8_SOURCE_V5 evtype=none
gtobssim irfs=P8_SOURCE_V5 evtype=PSF
gtobssim irfs=P8_SOURCE_V5 evtype=EDISP

      evtype=none is the default, in which case the application will use the front/back partition, consistent with pre-Pass 8 behavior.

    • DSS keywords specifying the event_type partition that was used will be written to the FT1 files that are produced.  These keywords will show the bit pattern that would be used to mask to obtain the corresponding partition, e.g., for evtype=PSF:

      DSTYP2: BIT_MASK(EVENT_CLASS,128,P8)
DSUNI2: DIMENSIONLESS
DSVAL2: 1:1

DSTYP2: BIT_MASK(EVENT_TYPE,60,P8)
DSUNI2: DIMENSIONLESS
DSVAL2: 1:1

      Here 60 = 0b111100, the binary representation of the mask with bits 2-5 set.

    • Since there is no information in the IRFs on cross-membership between event_type partitions, only bits for the selected partition will be set in the FT1 file.  This means that choosing event_types in gtselect for a different partition will result in no events passing the cut.
  • gtselect
    • The evtype option has been added, and DSS keywords indicating this selection will be written.

    • For both evclass and evtype, the user must specify the integer corresponding to bit-mask that selects the desired events within a single partition:

      gtselect evclass=128 evtype=3     # P8_SOURCE_V5, front and back (i.e., all) events
gtselect evclass=128 evtype=1     # P8_SOURCE_V5, front-only events
gtselect evclass=128 evtype=60    # P8_SOURCE_V5, PSF[0-3] (all) events
gtselect evclass=256 evtype=960   # P8_CLEAN_V5, EDISP[0-3] (all) events

      The evtype=[3,60,960] selections all return all of the events, but they also specify the irfs corresponding to the event_type partition selected.  This information is written to the DSS keywords and read by downstream tools.

    • evtype selections that cross partitions can be specified, but the behavior of the tools (i.e., which irfs are used) is undefined.
  • gtdiffrsp
  • gtexpcube2
  • gtirfs

CALDB changes

  • CALDB/data/glast/lat/bcf/irf_index.fits
  • CALDB/data/glast/lat/caldb.indx

  • No labels