CSC Data Products

Using the L3 Data Products

In addition to the tabulated properties for each detected source and observation in the Master Sources Table and Source Observations Table, a number of file-based Level 3 data products are produced for each source and observation individually, in formats suitable for analysis in CIAO. These include such things as:

Source region, background, and PSF images
Source region photon event lists
Limiting sensitivity maps
Auxiliary Response Files (ARFs)
Source and background light curves
Pulse invariant (PI) spectra and Redistribution Matrix Files (RMFs) [for ACIS observations]

Full-Field Level 3 Data Products | Source Region Level 3 Data Products

Full-Field Level 3 Data Products

A set of full-field (i.e. observation-based) data products is created for each observation that undergoes catalog processing. They are identified by the observation identification (ObsId) and observation interval identification (ObI), and by cycle for ACIS alternating exposure (interleaved) mode observations.

Data product	Pipeline	Filename
Full-Field Event File	Calibration	acis_evt3.fits, hrc_evt3.fits
Full-Field Image File (FITS, JPEG)	Detection	acis_img3.fits, hrc_img3.fits acis_img3.jpg, hrc_img3.jpg
Full-Field Background Image File	Detection	acis_bkgimg3.fits, hrc_bkgimg3.fits
Full-Field Exposure Map File	Calibration	acis_exp3.fits, hrc_exp3.fits
Full-Field Sensitivity Map File	Detection	acis_sens3.fits, hrc_sens3.fits
Aspect Histogram File	Calibration	acis_ahst3.fits, hrc_ahst3.fits
Bad Pixel File	Calibration	acis_bpix3.fits, hrc_bpix3.fits
Field of View File	Calibration	acis_fov3.fits, hrc_fov3.fits

Source Region Level 3 Data Products

A set of source-based data products is created for each detected source region in each observation that undergoes catalog processing. The source region data products are identified by the region identifier, observation identification (ObsId) and observation interval identification (ObI), and by cycle for ACIS alternating exposure (interleaved) mode observations.

Examples of source regions from two ObIs

Data product	Pipeline	Filename
Source Region Events File	Source	acis_regevt3.fits, hrc_regevt3.fits
Source Region Image File (FITS, JPEG)	Source	acis_regimg3.fits, hrc_regimg3.fits acis_regimg3.jpg, hrc_regimg3.jpg
Source Region PHA File	Source	acis_pha3.fits
Source Region ARF	Source	acis_arf3.fits, hrc_arf3.fits
Source Region RMF File	Source	acis_rmf3.fits
Source Region Exposure Map File	Source	acis_regexp3.fits, hrc_regexp3.fits
Source Region PSF File (FITS, JPEG)	Source	acis_psf3.fits, hrc_psf3.fits acis_psf3.jpg, hrc_psf3.jpg
Light Curve File	Source	acis_lc3.fits, hrc_lc3.fits
Region File	Detection	acis_reg3.fits, hrc_reg3.fits

Full-Field Event File (evt3.fits)

The full-field event file consists of a single FITS format event file for each observation that results from catalog processing. The observation event file has been reprocessed through acis_process_events or hrc_process_events, as appropriate, to apply the latest instrument calibrations and the standard event status and event grade (ACIS only) filters. In addition, the destreak algorithm has been applied to the ACIS-S4 CCD. Good time intervals have been revised to eliminate periods of background flares.

The good time intervals (GTIs) associated with full-field event data are included as additional FITS HDUs (CXC Data Model blocks) in the full-field FITS event file. For an event file containing ACIS data, there is a GTI for each ACIS CCD included in the full-field observation; there is a single GTI for an event file containing HRC data.

Note: The evt3.fits file is similar to the evt2.fits file from the Chandra Data Archive, but has different GTIs due to the filtering of background flares.

The full-field event FITS file is named

<s><obs>_<obi>N<v>[_<c>]_evt3.fits

where  is the instrument designation, <s> is the data source, <obs> is the observation identification, <obi> is the observation interval identification, <v> is the data product version number, and <c> is the cycle. The optional discriminator identified in square brackets is included only for ACIS alternating exposure (interleaved) mode observations.

Full-Field Image Files (img3.fits, img3.jpg)

FITS

The full-field image files consist of a single FITS format image file for each observation and science energy band; they are the image equivalents of the full-field event files filtered by the appropriate science energy band, blocked at multiple resolutions in SKY coordinates, and background-subtracted. The images are recorded in flux units of photons s^-1 cm^-2 by subtracting the full-field background image in the appropriate science energy band from the filtered and blocked full-field event data, and dividing the result by the full-field exposure map. Each image is 2048 x 2048 blocked SKY pixels in size. The blocking factors match those used in the source detection process (wavdetect), and are instrument-specific; they are 1, 2, and 4 for ACIS (-I or -S); 2, 5, and 12 for HRC-I; and 2, 5, 12, and 25 for HRC-S. The images are recorded in successive FITS HDUs (CXC Data Model blocks), in order of decreasing field coverage.

FITS HDUs (CXC Data Model blocks):

ACIS (-I or -S): IMAGE4, IMAGE2, IMAGE1
HRC-I: IMAGE12, IMAGE5, IMAGE2
HRC-S: IMAGE25, IMAGE12, IMAGE5, IMAGE2

[ACIS-I background Full-Field Events Image]

ACIS-I Full-Field Events Image

The full-field image FITS file is named

<s><obs>_<obi>N<v>[_<c>]__img3.fits

where  is the instrument designation, <s> is the data source, <obs> is the observation identification, <obi> is the observation interval identification, <v> is the data product version number, <c> is the cycle, and  is the energy band designation. The optional discriminator identified in square brackets is included only for ACIS alternating exposure (interleaved) mode observations.

JPEG

A set of JPEG format image files are also produced for each full-field observation. For ACIS observations, multicolor images are generated by combining the image equivalents of the full-field event file filtered by the soft, medium, and hard science energy bands, blocked at multiple resolutions in SKY coordinates, according to the algorithm of Lupton et al. (2004, PASP, 116, 133). For HRC observations, the images are generated from the image equivalent of the full-field event file filtered by the wide science energy band, blocked at multiple resolutions in SKY coordinates. In both cases, the images are exposure corrected by dividing the filtered and blocked full-field event data by the full-field exposure map.

The full-field JPEG image files are named

<s><obs>_<obi>N<v>[_<c>]_<f>_img3.jpg

where  is the instrument designation, <s> is the data source, <obs> is the observation identification, <obi> is the observation interval identification, <v> is the data product version number, <c> is the cycle, and <f> is the blocking factor. The optional discriminator identified in square brackets is included only for ACIS alternating exposure (interleaved) mode observations. Each image will be 1024 x 1024 pixels in size.

Full-Field Background Image File (bkgimg3.fits)

The full-field background FITS format image files consist of a background counts image for each observation and science energy band, blocked at multiple resolutions in SKY coordinates. The images are recorded in units of counts, and are 2048 X 2048 blocked SKY pixels in size. The blocking factors match those used for the corresponding images that comprise the full-field image files. The background counts images are recorded in successive FITS HDUs (CXC Data Model blocks), in order of decreasing field coverage.

FITS HDUs (CXC Data Model blocks):

ACIS (-I or -S): IMAGE4, IMAGE2, IMAGE1
HRC-I: IMAGE12, IMAGE5, IMAGE2
HRC-S: IMAGE25, IMAGE12, IMAGE5, IMAGE2

ACIS-I background map

The full-field background image FITS file is named

<s><obs>_<obi>N<v>[_<c>]__bkgimg3.fits

where  is the instrument designation, <s> is the data source, <obs> is the observation identification, <obi> is the observation interval identification, <v> is the data product version number, <c> is the cycle, and  is the energy band designation. The optional discriminator identified in square brackets is included only for ACIS alternating exposure (interleaved) mode observations.

Full-Field Exposure Map (exp3.fits)

The full-field exposure map file consists of a single FITS format file for each observation and science energy band that results from catalog processing. A full-field instrument map is generated at the equivalent monochromatic energy for each science energy band, and a set of exposure maps, blocked at multiple resolutions in SKY coordinates, are computed by applying the aspect histogram sampled at 0.5 arcsec resolution. Each exposure map is 2048 X 2048 blocked SKY pixels in size. The blocking factors match those used for the corresponding images that comprise the full-field image files. The exposure maps are recorded in successive FITS HDUs (CXC Data Model blocks), in order of decreasing field coverage.

FITS HDUs (CXC Data Model blocks):

ACIS (-I or -S): EXPMAP4, EXPMAP2, EXPMAP1
HRC-I: EXPMAP12, EXPMAP5, EXPMAP2
HRC-S: EXPMAP25, EXPMAP12, EXPMAP5, EXPMAP2

Note: The exp3.fits exposure maps are created as shown in the CIAO thread "Multiple Chip ACIS Exposure Map."

ACIS-I exposure map

The full-field exposure map FITS file is named

<s><obs>_<obi>N<v>[_<c>]__exp3.fits

where  is the instrument designation, <s> is the data source, <obs> is the observation identification, <obi> is the observation interval identification, <v> is the data product version number, <c> is the cycle, and  is the energy band designation. The optional discriminator identified in square brackets is included only for ACIS alternating exposure (interleaved) mode observations.

Full-Field Sensitivity Map (sens3.fits)

The full-field sensitivity map consists of a single FITS format file for each observation and science energy band that records the limiting sensitivity for a point source to satisfy the minimum flux significance criterion. The limiting sensitivity is determined in units of photons s^-1 cm^-2. The sensitivity map is 2048 X 2048 blocked SKY pixels in size, with a blocking factor of 4 for ACIS (-I or -S), 12 for HRC-I, and 25 for HRC-S.

ACIS-I sensitivity map

The full-field sensitivity map FITS file is named

<s><obs>_<obi>N<v>[_<c>]__sens3.fits

where  is the instrument designation, <s> is the data source, <obs> is the observation identification, <obi> is the observation interval identification, <v> is the data product version number, <c> is the cycle, and  is the energy band designation. The optional discriminator identified in square brackets is included only for ACIS alternating exposure (interleaved) mode observations.

Aspect Histogram File (ahst3.fits)

The aspect histogram file consists of a single FITS format file for each observation that records the histogram of aspect pointing and roll offsets during the observation. The aspect histogram is used in catalog processing to compute the response matrix averaged over the observation.

FITS HDUs (CXC Data Model blocks):

ACIS: asphist0, asphist1, asphist2, asphist3, asphist4, asphist5, asphist6, asphist7, asphist8, asphist9
HRC: ASPHIST

Note: The ahst3.fits file is generated by the asphist tool, as users would in CIAO data analysis.

Aspect Histogram

The aspect histogram FITS file is named

<s><obs>_<obi>N<v>[_<c>]_ahst3.fits

Bad Pixel File (bpix3.fits)

The bad pixel file consists of a single FITS format file for each observation that records the bad pixel information for the observation. The bad pixel information is used in catalog processing to flag for removal the effects of detector bad pixels during the observation.

FITS HDUs (CXC Data Model blocks):

ACIS: BADPIX0, BADPIX1, BADPIX2, BADPIX3, BADPIX4, BADPIX5, BADPIX6, BADPIX7, BADPIX8, BADPIX9
HRC: BADPIX

Note: For ACIS, the bpix3.fits file is the same as the bpix1.fits file from the Chandra Data Archive. The HRC bpix3.fits may have a newer degap correction applied than the bpix1.fits version.

The bad pixel FITS file is named

<s><obs>_<obi>N<v>[_<c>]_bpix3.fits

Field of View File (fov3.fits)

The field of view file consists of a single FITS format file for each observation that records the region of the sky that was imaged by the detector during the observation, including the effects of spacecraft dither.

Note: The fov3.fits file may be slightly different than the fov1.fits from the Chandra Data Archive, due to the different GTIs from background flare filtering.

Field of View (detector sky coverage)

The field of view FITS file is named

<s><obs>_<obi>N<v>[_<c>]_fov3.fits

Source Region Event File (regevt3.fits)

The source region event file consists of a single FITS format event file for each detection source region of each observation; it is the result of applying a rectangular SKY region filter to the corresponding full-field event file for the observation. The rectangular SKY region filter is equal in size to the background region of interest (ROI) corresponding to the detected source region.

The good time intervals (GTIs) associated with source region event data are included as additional FITS HDUs (CXC Data Model blocks) in the source region FITS event file. For an event file containing ACIS data, there is a GTI for each ACIS CCD included in the source region; there is a single GTI for an event file containing HRC data.

The source region event FITS file is named

<s><obs>_<obi>N<v>[_<c>]_<r>_regevt3.fits

where  is the instrument designation, <s> is the data source, <obs> is the observation identification, <obi> is the observation interval identification, <v> is the data product version number, <r> is the region identifier, and <c> is the cycle. The optional discriminator identified in square brackets is included only for ACIS alternating exposure (interleaved) mode observations.

Source Region Spectrum Files (pha3.fits, arf3.fits, rmf3.fits)

PHA

The PHA spectrum file consists of a single FITS format file for each detection source region of each ACIS observation that records the low resolution PI spectrum of the events extracted from the source region, resulting from catalog processing. The PI spectrum is constructed using weighted responses for the areas of the detector over which the source region dithers. A low resolution PI spectrum of the events extracted from the background region is recorded in the FITS HDU (CXC Data Model block) immediately following the source PHA spectrum HDUs.

FITS HDUs (CXC Data Model blocks):

ACIS: SPECTRUM1, SPECTRUM2

The PHA spectrum FITS file is named

acis<s><obs>_<obi>N<v>[_<c>]_<r>_pha3.fits

where <s> is the data source, <obs> is the observation identification, <obi> is the observation interval identification, <v> is the data product version number, <r> is the region identifier, and <c> is the cycle. The optional discriminator identified in square brackets is included only for ACIS alternating exposure (interleaved) mode observations.

ARF

The auxiliary response file consists of a single FITS format file for each detection source region of each observation that records the weighted ARF for the areas of the detector over which the source region for an observation dithers.

The auxiliary response FITS file is named

<s><obs>_<obi>N<v>[_<c>]_<r>_arf3.fits

where  is the instrument designation, <s> is the data source, <obs> is the observation identification, <obi> is the observation interval identification, <v> is the data product version number, <r> is the region identifier, and <c> is the cycle. The optional discriminator identified in square brackets is included only for ACIS alternating exposure (interleaved) mode observations.

RMF

The redistribution matrix file consists of a single FITS format file for each detection source region of each ACIS observation that records the weighted RMF for the areas of the detector over which the source region for an observation dithers.

The redistribution matrix FITS file is named

acis<s><obs>_<obi>N<v>[_<c>]_<r>_rmf3.fits

Source Region Image Files (regimg3.fits, regimg3.jpg)

FITS

The source region image files consist of a set of FITS format image files, one for each detection source region of each observation, for each science energy band. Each source region image file is the image equivalent of the source region event file filtered by the appropriate science energy band, and blocked in SKY coordinates at the lowest blocking factor (highest spatial resolution) used in the source detection process (wavdetect) that includes the location of the source region. The images are recorded in flux units of photons s^-1 cm^-2 by dividing the filtered and blocked source region event data by the source region exposure map.

ACIS Source Region Events Image

The source region image FITS files is named

<s><obs>_<obi>N<v>[_<c>]_<r>_regimg3.fits

where  is the instrument designation, <s> is the data source, <obs> is the observation identification, <obi> is the observation interval identification, <v> is the data product version number, <r> is the region identifier,  is the energy band designation, and <c> is the cycle. The optional discriminator identified in square brackets is included only for ACIS alternating exposure (interleaved) mode observations.

JPEG

One or more JPEG format image files are also produced for each source region observation. For both ACIS and HRC observations, single band source region images are generated from the image equivalent of the source region event file that has been filtered by each of the science energy bands defined for the instrument, and blocked in SKY coordinates at the lowest blocking factor (highest spatial resolution) used in the source detection process (wavdetect) that includes the location of the source region. In addition, for ACIS, a multicolor source region image is generated by combining the image equivalents of the source region event file filtered by the soft (red), medium (green), and hard (blue) science energy bands, blocked in SKY coordinates at the same resolution as the corresponding single band source region images, according to the algorithm of Lupton et al. (2004, PASP, 116, 133). In all cases, the image is exposure-corrected by dividing the filtered and blocked source region event data by the source region exposure map.

The single band source region JPEG images are named

<s><obs>_<obi>N<v>[_<c>]_<r>_regimg3.jpg

and the multicolor source region JPEG images are named

<s><obs>_<obi>N<v>[_<c>]_<r>_reg3img3.jpg

where  is the instrument designation, <s> is the data source, <obs> is the observation identification, <obi> is the observation interval identification, <v> is the data product version number, <r> is the region identifier,  is the energy band designation, and <c> is the cycle. The optional discriminator identified in square brackets is included only for ACIS alternating exposure (interleaved) mode observations.

Source Region Exposure Map (regexp3.fits)

The source region exposure map consists of a single FITS format file for each detection source region of each observation that results from catalog processing, for each science energy band. A full resolution instrument map that covers the detected source region bounding box is generated at the equivalent monochromatic energy for each energy band, and the exposure map is computed by applying the aspect histogram sampled at 0.5 arcsec resolution and blocking in SKY coordinates. The blocking factor matches that used for the corresponding full-field image file.

Counts image and exposure map of an ACIS detection

The source region exposure map FITS file is named

<s><obs>_<obi>N<v>[_<c>]_<r>_regexp3.fits

where  is the instrument designation, <s> is the data source, <obs> is the observation identification, <obi> is the observation interval identification, <v> is the data product version number, <r> is the region identifier,  is the energy band designation, and <c> is the cycle. The optional discriminator identified in square brackets is included only for ACIS alternating exposure (interleaved) mode observations.

Source Region PSF Files (psf3.fits, psf3.jpg)

FITS

The point spread function files consist of a set of FITS format image files, one for each detection source region of each observation, for each science energy band. Each point spread function file records the normalized PSF computed at the equivalent monochromatic energy of the appropriate science energy band, sampled on the same pixel grid as the source region image file.

Simulated PSF at source location

The point spread function FITS files are named

<s><obs>_<obi>N<v>[_<c>]_<r>_psf3.fits

where  is the instrument designation, <s> is the data source, <obs> is the observation identification, <obi> is the observation interval identification, <v> is the data product version number, <r> is the region identifier,  is the energy band designation, and <c> is the cycle. The optional discriminator identified in square brackets is included only for ACIS alternating exposure (interleaved) mode observations.

JPEG

One or more JPEG format image files are also produced for each source region point spread function. Point spread function images are generated from the point spread function FITS files in each of the science energy bands defined for the instrument, sampled on the same pixel grid as the source region image.

The point spread function JPEG image files are named

<s><obs>_<obi>N<v>[_<c>]_<r>_psf3.jpg

where  is the instrument designation, <s> is the data source, <obs> is the observation identification, <obi> is the observation interval identification, <v> is the data product version number, <r> is the region identifier,  is the energy band designation, and <c> is the cycle. The optional discriminator identified in square brackets is included only for ACIS alternating exposure (interleaved) mode observations.

Light Curve Files (lc3.fits)

The light curve files consist of a set of FITS format files, one for each detection source region of each observation, for each science energy band. Each light curve file records the multi-resolution light curve output by the Gregory-Loredo analysis of the receipt times of the source events within the source region. A background light curve with identical time-binning to the source light curve is derived from an analysis of the events within the background region. The background light curve is recorded in the FITS HDU (CXC Data Model block) immediately following the source light curve HDUs. A detailed description of the computation of the multi-resolution light curve is forthcoming.

Gregory-Loredo light curve (top) compared to the same light curve with the effects of dither removed (bottom)

The light curve FITS files are named

<s><obs>_<obi>N<v>[_<c>]_<r>_lc3.fits

where  is the instrument designation, <s> is the data source, <obs> is the observation identification, <obi> is the observation interval identification, <v> is the data product version number, <r> is the region identifier,  is the energy band designation, and <c> is the cycle. The optional discriminator identified in square brackets is included only for ACIS alternating exposure (interleaved) mode observations.

Region File (reg3.fits)

The region file consists of a single FITS format region file for each detection source region of each observation, which records the region description for the modified source region and the corresponding modified background region, in consecutive HDUs.

FITS HDUs (CXC Data Model blocks):

ACIS, HRC: SRCREG, BKGREG

[example of source region evt3 file with reg3 regions overlaid]

Source region event 3 image with corresponding Level 3 region file source and background regions overlaid

The region FITS file is named

<s><obs>_<obi>N<v>[_<c>]_<r>_reg3.fits

where  is the instrument designation, <s> is the data source, <obs> is the observation identification, <obi> is the observation interval identification, <v> is the data product version number, <r> is the region identifier, and <c> is the cycle. The optional discriminator identified in square brackets is included only for ACIS alternating exposure (interleaved) mode observations.