Chandra Calibration Cookbook: ACIS Data

PRELIMINARY PREPARATIONS

1. Definition of the Basic Tools

CIAO 2.1: `Chandra Interactive Analysis of Observations'; the software is located in /net/xray/usr/local/ciao_2.1

HEAsoft: a unified Release of the FTOOLS and XANADU Software Packages

FV : `The Interactive FITS File Editor'

ds9 : SAOImager, what you will use to display the images in CIAO
 

3. To start and use any of the packages,  your .chsrc file (located in your home directory on your machine) must be modified. Add these lines to this file:

## CIAO 2.1 version:
setenv CALDB /net/xray/usr/local/ciao_2.1
setenv CALDBCONFIG $CALDB/software/tools/caldb.config
setenv CALDBALIAS $CALDB/software/tools/alias_config.fits
alias ciao "source /net/xray/usr/local/ciao_2.1/bin/ciao_users.csh"

FirstLook: GUI for looking at the data, quick spectrum, light curve, etc.
FilterWindow: GUI for filter creation
Prism: GUI for browsing
CHiPS: for imaging, plotting
Sherpa: for fitting, modeling
datamodel (command-line based) : filtering and binning language (have printed out manual)

Fits View (FV)
setenv FV /net/xray/usr/local/fv2.6/linux/
set path = ($FV/bin $path)
type fv & to start
 

XANADU (incl. XSpec, FTools, etc.)
setenv LHEASOFT /net/xray/usr/local/lheasoft/Linux_2.2_i686
source $LHEASOFT/lhea-init.csh
type xspec to start
 

SAO Image Window
alias ds9 "/net/xray/usr/ds9"
type ds9 to start
note: you may want to add this line to your .cshrc file as well as the above CIAO commands

IDL (Interactive Data Language):

IDL programs for the analysis of ACIS data (e.g. PSF analysis software) can be found at
 /net/xray/usr/local/idladd/chandraidl

and general xray idl programs can be found at
/net/xray/pub/xrayidl
 Instructions to run Daniel's IDL startup script can be found here

Special CIAO software downloaded from the user-exchange software page

Maxim Markevitch's programs for blank sky background issues and for filtering data:

badpixfilter
lc_clean
make_acisbg
are located in /net/xray/usr/local/acisbg/bin.redhat62/
 

Spatially-weighted RMF and ARF files (background and filtering) used for spectral analysis of extended emission:

calcarf
calcrmf
are located in /net/xray/usr/local/ciao_2.0/bin.rh/

when using any of these programs, you must type the path as part of the command, i.e.
/net/xray/usr/local/ciao_2.0/bin.rh/calcrmf -phafile galaxy.pi -wmap galaxy_wmap.fits -o galaxy.wrmf
/net/xray/usr/local/acisbg/bin.redhat62/lc_clean lc_clean.par
 
 

CALIBRATION OF ACIS DATA

Outline:
1. Examine Chandra data,  get familiar with file structure
2. Append appropriate "bad pixel" file to data
3. Restrict the energy range to energies for which the calibration is well known
4. Check for background flares by making a lightcurve of your dataset -- 2 ways
 

1. Examine Chandra data and familiarize yourself with file structure

   data will come as tar file, e.g. gc.tar; need to unpack

                tar xvf gc.tar

A - what are the components of my dataset?

ls
oif.fits  primary  secondary

oif.fits --> "Observation Index File"

primary:
acisf00945N001_cntr_img2.fits  --> high resolution image of ctr in sky coords
acisf00945N001_src2.fits       --> list of detected sources, ct. rates
acisf00945N001_evt2.fits       --> filtered events file; 'good' photons *** most important file!***
acisf00945_000N001_evt1.fits   --> raw events file
acisf00945N001_full_img2.fits  --> low resolution of full field in sky coords
acisf00945_000N001_flt1.fits   --> list of good time intervals

secondary:

acisf00945_000N001_aoff1.fits --> aspect offsets ***you will be using this file also***
acisf00945_000N001_mtl1.fits  --> mission timeline
acisf00945_000N001_bpix1.fits --> bad pixel lists
acisf00945_000N001_soff1.fits --> alignment offsets
acisf00945_000N001_msk1.fits  --> mask
acisf00945_000N001_stat1.fits --> exposure statistics

the events level 2 file is the fits file you will be using in all of the following

B - use the datamodel language to learn more about the dataset
 

dmlist acisf00945N001_evt2.fits header | grep DATE-OBS

C - check which CCDs were on, what the exposure time is, how many counts, etc.:
 

dmlist acisf00945N001_evt2.fits blocks

     Block Name                          Type         Dimensions
------------------------------------------------------------------------------
Block    1: PRIMARY                        Null
Block    2: EVENTS                         Table        15 cols x 596739   rows
Block    3: GTI3                           Table         2 cols x 1        rows
Block    4: GTI0                           Table         2 cols x 2        rows
Block    5: GTI1                           Table         2 cols x 3        rows
Block    6: GTI2                           Table         2 cols x 4        rows
Block    7: GTI6                           Table         2 cols x 3        rows
Block    8: GTI7                           Table         2 cols x 1        row
 

dmlist acisf00945N001_evt2.fits header | grep ONTIME

0079 ONTIME0       49376.0000459850 [s]       Real8        [s] Sum of GTIs
0082 ONTIME1       49372.8000459820 [s]       Real8        [s] Sum of GTIs
0085 ONTIME2       49369.6000459790 [s]       Real8        [s] Sum of GTIs
0088 ONTIME3       49379.2000459880 [s]       Real8        [s] Sum of GTIs
0091 ONTIME6       49372.8000459820 [s]       Real8        [s] Sum of GTIs
0094 ONTIME7       49379.2000459880 [s]       Real8        [s] Sum of GTIs
0097 ONTIME        49379.2000459880 [s]       Real8        [s] Sum of GTIs
 

2. Use Observation-specific Bad Pixel Files

Follow CIAO 2.1 Science Thread- part A (Changing ardlib manually)

Follow CIAO 2.1 Science Thread - part C (Restrict the energy range)

Follow CIAO 2.1 Science Thread - part D (Eliminate High Background Times)