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Last modified: 7 November 2022

URL: https://cxc.cfa.harvard.edu/ciao/data_products_guide/region.html
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Region Files

Filename Description Content SDP Pipeline
acis_bpix1.fits bad pixel list BADPIX ACIS1
hrc_bpix1.fits bad pixel list BADPIX HRC1
acis_src2.fits imaging source list SRC ACIS2
hrc_src2.fits imaging source list SRC HRC2
acis_fov1.fits field of view FOV ACIS1
hrc_fov1.fits field of view FOV HRC1
acis_msk1.fits detector mask MSK ACIS1
hrc_msk1.fits detector mask MSK HRC1
acis_src1a.fits grating source list TGSRC TG1.5
hrc_src1a.fits grating source list TGSRC TG1.5

Bad Pixel List

Filename Description Content SDP Pipeline
acis_bpix1.fits bad pixel list BADPIX ACIS1
hrc_bpix1.fits bad pixel list BADPIX HRC1

Description:

A list of pixels identified as "bad"; criteria for flagging a pixel are listed in the Bad Pixels dictionary entry. Any tool that reads this file will exclude the bad pixels from its calculations.

Creator tool: acis_build_badpix, hrc_build_badpix

ACIS Columns:

Column Name Units Description
SHAPE region shape
COMPONENT Component number
CHIP(CHIPX,CHIPY)[2] pixel CHIP X location
TIME s Time pixel went bad
TIME_STOP s Time pixel went bad
STATUS[4] coded Badpixel status code

HRC Columns:

Column Name Units Description
CHIP_ID Chip ID
SHAPE shape of bad element
COMPONENT component index
CHIPX[2] pixel chip X
CHIPY[2] pixel chip Y
STATUS Status Bitarray

Imaging Source List

The src2.fits files are no longer created as of DS 8.4 (June 2011).

Filename Description Content SDP Pipeline
acis_src2.fits imaging source list SRC ACIS2
hrc_src2.fits imaging source list SRC HRC2

Description:

The imaging source candidate list is obtained from a single run of celldetect with S/N threshold equal to 3 and should not be used directly in analysis. Users interested in spatial analysis should perform their own detection runs with one of the three Chandra Detect tools: celldetect, wavdetect, and vtpdetect. The Detect Manual describes which tool is suited to a particular analysis.

Creator tool: celldetect

Columns:

Column Name Units Description
RA deg Source Right Ascension
DEC deg Source Declination
RA_ERR deg Source Right Ascension Error
DEC_ERR deg Source Declination Error
POS(X,Y) pixel Physical coordinates
X_ERR pixel Source X position error
Y_ERR pixel Source Y position error
CELLPOS(CELL_X,CELL_Y) pixel Physical coordinates
DETSIZE pixel source cell size
BKGSIZE pixel background cell size
NPIXSOU pixel pixels in source cell
NPIXBKG pixel pixels in background cell
NET_COUNTS count Net source counts
NET_COUNTS_ERR count Error in net source counts
BKG_COUNTS count Background counts (scaled to source cell)
BKG_COUNTS_ERR count Error in BKG_COUNTS
NET_RATE count/s Source count rate
NET_RATE_ERR count/s Source count rate error
BKG_RATE count/s Background count rate
BKG_RATE_ERR count/s/pixel Background count rate error
EXPTIME s Effective exposure time
SNR Signal-to-Noise ratio
SHAPE Shape of source region
R[2] pixel Radii of source region source
ROTANG deg Rotation angle of source region
PSFRATIO ratio of source ellipse size to PSF size
BLOCK blocking factor
COMPONENT Source Number
EXPO_RATIO ratio of average background and detect cell exp
DOUBLE double detection flag
DOUBLE_ID double source component

Field of View

Filename Description Content SDP Pipeline
acis_fov1.fits field of view FOV ACIS1
hrc_fov1.fits field of view FOV HRC1

Description:

The field-of-view file contains regions which describe the edges of each instrument chip (one polygon per chip). This region file can be used to filter event files or images to contain specific chips.

Creator tool: skyfov

Columns:

Column Name Units Description
POS(X,Y)[13] pixel Position
SHAPE Region shape type
R[2] pixel Radius
ROTANG[2] pixel Angle
COMPONENT Component number
CCD_ID CCD ID

Detector Mask

Filename Description Content SDP Pipeline
acis_msk1.fits detector mask MSK ACIS1
hrc_msk1.fits detector mask MSK HRC1

Description:

The mask file records the valid part of the detector element - ACIS CCD or HRC plate - used for the observation (i.e. the portion for which events can be telemetered). The active portion of an element may be smaller than the default regions if an observation was performed using subarrays or custom windows

Creator tool: acis_build_mask, hrc_build_mask

Columns:

Column Name Units Description
SHAPE region shape
COMPONENT Component index
CHIP(CHIPX,CHIPY)[2] pixel CHIP position
SAMP_CYC sampling cycle
PHAMIN minimum pulse height
PHAMAX maximum pulse height

For ACIS, each CCD is 1024x1024 pixels. The mask file for a standard full-frame observation will contain 3 rows. The first row will SAMP_CYC=1 and will have X and Y values 2:1023. The 2nd and 3rd rows will have SAMP_CYC=0, indicating that no events are recorded there; row2 will have X and Y values going from 1:1024, row3 will have X and Y values going from 2:1023 with the shape set to "!rectangle". This is logic used to specify that no events are detected in the 1 pixel border around the chip.

Grating Source List

Filename Description Content SDP Pipeline
acis_src1a.fits grating source list TGSRC TG1.5
hrc_src1a.fits grating source list TGSRC TG1.5

Description:

The zero-order centroid location for grating observations. if there are multiple observation intervals (OBIs), then the table is formed by merging each OBI's table with the previous using source-matching to form a unique source identifier column.

Creator tools: celldetect, tgidselectsrc, tgmatchsrc

Columns:

Column Name Units Description
RA deg Source Right Ascension
DEC deg Source Declination
RA_ERR deg Source Right Ascension Error
DEC_ERR deg Source Declination Error
POS(X,Y) pixel Physical coordinates
X_ERR pixel Source X position error
Y_ERR pixel Source Y position error
CELLPOS(CELL_X,CELL_Y) pixel Physical coordinates
DETSIZE pixel source cell size
BKGSIZE pixel background cell size
NPIXSOU pixel pixels in source cell
NPIXBKG pixel pixels in background cell
NET_COUNTS count Net source counts
NET_COUNTS_ERR count Error in net source counts
BKG_COUNTS count Background counts (scaled to source cell)
BKG_COUNTS_ERR count Error in BKG_COUNTS
NET_RATE count/s Source count rate
NET_RATE_ERR count/s Source count rate error
BKG_RATE count/s Background count rate
BKG_RATE_ERR count/s/pixel Background count rate error
EXPTIME s Effective exposure time
SNR Signal-to-Noise ratio
SHAPE Shape of source region
R[2] pixel Radii of source region source
ROTANG deg Rotation angle of source region
PSFRATIO ratio of source ellipse size to PSF size
BLOCK blocking factor
COMPONENT Source Number
EXPO_RATIO ratio of average background and detect cell exp
DOUBLE double detection flag
DOUBLE_ID double source component
TG_SRCID
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