This section provides a general description of the final products obtained when running the SAS chains on OM data.
The chains produce intermediate files that are sometimes overwritten by different tasks. They are recognized by the first letter of their name (``I'' in omichain, ``F'' in omfchain, ``g'' and ``u'' in omgchain). Their detailed description can be found in the on-line documentation.
Similar files are generated by the standard pipeline processing run at the SSC, but the user shall be aware that they may have subtle differences between the two sets. All intermediate files are deleted in the pipeline processing. By running the tasks interactively, the user can maintain these intermediate products for a better understanding of the whole process.
OM processing chains and pipeline products are named as ``zooooooooooOMueeettttttsxxx.fff'', where:
In the following we refer to a data type by the tttttt identifier, e.g. such as tttttt= SIMAGE for the OM sky image product. We omit the window and source number identifier (sxxx).
In combined images resulting from ommosaic or after processing the full frame image produced by omcomb, files with data type IMAGE_ and SIMAGE, ``s'' indicates the corresponding filter used. The optical filters are noted V, B and U, while L, M and S represent UVW1, UVM2 and UVW2 respectively.
There are two products associated with the tracking history files, namely the TSHPLT.PDF and the TSTRTS.FIT file. There are three data products per OSW, namely IMAGE_.FIT, SIMAGE.FIT and SWSRLI.FIT. If fast mode data are present, there are two products per OSW, namely TIMESR.FIT and its graphics version TIMESR.PDF. There are two products generated on a per observation basis, which are FLAFLD.FIT and OBSMLI.FIT.
It should be noted that the pipeline produces compressed FITS files named .FTZ while the output obtained when the chains are run by the user is not compressed , .FIT.
TSHPLT.PDF provides a visualization of the tracking history file. It gives an overview of the pointing stability in the course of an exposure. The drift history of an exposure is displayed as a vector diagram. Each data point represents the average attitude solution of one tracking frame, lasting typically 20 s. The pointing drift is calculated with respect to the OM attitude at the time where the reference frame was defined. The reference attitude of an exposure is determined at the beginning of a science exposure. Histograms at the side of the vector diagram show the projection of the OM pointing drift onto the x- and y-direction. The second output page shows the incremental OM drift between 2 subsequent tracking frames. A clustering of points at one location would indicate a systematic drift into one direction. Typically the pointing stability is better than 1 arcsec during one exposure, which corresponds to 2 pixel on the diagrams. There is one TSHPLT PDF file produced for each THX file.
TSTRTS.FIT file:. There is one TSTRTS FITS file produced for each THX file. The binary extension comprises n columns, i.e. one for each tracking star used. Each column list the count rate (cts/s) of a tracking star averaged over the tracking frame duration. Each row indicates a new tracking frame and one column corresponds to a time series of a specific star. The number of columns corresponds to the number of tracking stars used in an exposure. It can be any number up to 15.
IMAGE_.FIT file: The Primary array contains the flatfield and mod8 corrected image. The header contains the WCS parameters applied to the raw image. The MODES extension lists the details of the window configuration. The QUALITY extension contains in an image the quality array. Any non-zero entry in the quality array reflects a bad pixel notified in the calibration bad pixel map or any location of the image where problems were encountered during the image processing. The pseudo images generated for fast mode windows follow this naming too.
SIMAGE.FIT file: The primary array of this dataset contains the north aligned sky image. The image is flatfielded, mod8 corrected, resampled and distortion corrected. The image is north aligned. WCS coordinates are contained as header keywords. Coincidence losses and dead time are not corrected in this image. The north aligned sky pseudo images generated for fast mode windows follow this naming too.
SWSRLI.FIT file: The primary header of an OSW source list file contains, besides the definition of the OSW within the exposure and the observation, the sensitivity limit of the plate expressed in count rates and in instrumental magnitudes. The binary extension holds the list of detected sources. There are the following entries for each detected source: identifier within the OSW, source position in pixel, source position in RA/Dec and galactic coordinates, the positional uncertainty, the extracted source count rates and its error estimate, the significance of the source detection, the brightness in instrumental magnitudes, the shape of the source expressed as the two semi-axes of an ellipse (for point sources the two axes should agree), the orientation of the ellipse and three quality flags, describing whether the source is thought to be extended, confused or affected by bad pixels. The last entry is the source identifier in the final combined source list.
FLAFLD.FIT file: This image is either part of the pipeline products or generated by omflatgen. There is one file per observation containing an image extension. The image describes the flatfield response covering the whole detector at coarse resolution. It is set to unity.
TIMESR.FIT file: The time series contains source (background subtracted) and background rates and their error estimates as a function of time, within the specified time sampling.
TIMESR.PDF file: The time series is plotted here to produce a graphic light curve, together with some statistics performed on the data.
OBSMLI.FIT file: This file contains the combined source list for all OSWs of an observation. Information of sources whose spatial position coincides within the specified nsigma are merged together. An observation source identifier is assigned to each source, which can be used to look up the sources in OSW source lists (SWSRLI files). The list contains: the observation source identifier, the position in RA/Dec and galactic coordinates, the positional uncertainty, the detection significance and corrected count rates in the different filters, the source brightness expressed in instrumental magnitudes and its uncertainty, the quality, source extension and confusion flag for each filter, the characterization and orientation of the spatial extent (described as in the SWSRLI files by the two semi-axes and the orientation angle with respect to the image x-axis) for each filter, and finally, if a transformation was possible, the source brightness in a standard photometric system, as well as the color indices.
AB magnitudes and fluxes for all filters are included as well.
In SAS version 6.5, all these quantities in the OBSMLI file were vectorized (values for each filter) in order to reduce the number of file columns. In newer versions there is again one simple column for each computed parameter and filter.
IMAGE_.FIT file: This image is similar to the normal image processing one. It is a copy of the original raw image, with completed header information and modulo_8 correction.
RIMAGE_.FIT file: The undistorted and rotated image produced by omgprep. It is the basis for the automatic spectral detection and extraction, and for interactive extraction with omgsource. This file may also be named GIMAGE_.FIT in future pipeline products.
SWSRLI.FIT file: It contains the position and characteristics of the detected zero and first orders and the correlations found between them. The results of the grism astrometry are included in this file.
REGION.ASC file: This is an ASCII version of the SWSRLI source list file for use with ds9 display.
SPECLI.FIT file: This is similar to the SWSRLI file, but it contains only the zero and first order positions of the main target extracted spectrum, or if ''extractfieldspectra=yes'' was used, all final extracted spectra. For each extracted spectrum, the nature of the source is also given (Target, Field Object, Default Extraction,...)
SPCREG.ASC file: This is an ASCII version of the SPECLI source list file for use with ds9 display.
SPECTR.FIT file: The extracted and calibrated spectra are written in this file. For each spectrum a table extension is given. On its columns we can find:
- wavelength
- net spectrum (count rate)
- error in net spectrum
- background rate
- error in background
- flux calibrated spectrum
- error in flux
SPECTR.PDF / SPECTR.PS files: They contain plots of the extracted spectra in the corresponding SPECTR.FIT file.