ACIS Cycle 11 Aimpoint and Off-Axis RMFs/ARFs

NOTICE TO CY11 PROPOSAL PLANNERS -- FINAL RELEASE

This is the final release of the CY11 proposal planning files.

The *.arf files below have been updated to include a new and better model of the HRMA axial effective area, which applies to all configurations. (We have elected NOT to upgrade the ACIS Optical Blocking Filter contamination model, which is under further investigation.) The new hrma files is named "hrmaD1996-12-20axeffaN0008.fits" and is being released with CalDB 4.1.1. An incumbent adjustment of the HETG grating efficiencies is also being released, to maintain the HEG and MEG 1st-order cross-calibration accuracy.

The update to the HRMA model involves a more self-consistent application of small contamination layers on the iridium mirror surfaces, and uses a different method of weighting the HRMA pre-launch calibration data. The result of the change is an improvement in high-temperature cluster modeling with the HRMA/ACIS-S and HRMA/ACIS-I configurations, with derived plasma temperatures more consistent between these two internal configurations, and better cross-calibration with the XMM telescope as well.

The new *.arf files below do not include the "cy11_p.arf" specification which formerly was to designate them as provisional ARFs. Users should download these new *.arf files and delete all of the *cy11_p.arf files released previously in Cycle 11.

We have prepared sample RMFs and corresponding ARFs for proposal planning purposes. These are positioned at the aimpoints of the ACIS-I and ACIS-S arrays, and at selected off-axis points to allow the proposer to estimate the effects of the ACIS CTI on the chips' performance using the current operational mode at focal plane temperature of -120C. Table 1 includes the filenames and corresponding chip and sky coordinates to which they apply.

To download individual files, <Shift>-click on the filename. The complete set of responses is available as a gzipped tarfile from the anonymous FTP site asc.harvard.edu in the directory /pub/caldb/CY11.

These files were built with CIAO 4.1 and CALDB 4.1.1. The RMFs are PI RMFs built with the CIAO phase-2 response tool mkacisrmf. They have 1024 linear energy bins (0.255 keV to 12.0 keV for both ACIS-I and ACIS-S), and 1024 linear PI bins (1-1024). (1-1024). All of the ACIS-I RMF files above are for the CTI-corrected response case, including the CTI corrections for ACIS-S3. That is, the P2_RESP input file used is acisD2000-01-29p2_respN0006.fits, and the new CTI-corrected gain file acisD2000-01-29gain_ctiN0006.fits has been applied in mkacisrmf to set the PI energy scale.

The ARFs were built with mkarf, using the appropriate RMF for the energy scale. They are "2-pi" ARFs (no encircled energy correction) and assume a point source. They have been corrected for the time- and spatially-dependent contaminant absorption projected for the date 2010-05-15 (TT=390268865.184s), using the ARDLIB CONTAM file feature in CIAO 4.1, with the same CalDB file as used in the previous two cycles, namely acisD1999-08-13contamN0004.fits.

Caveats

1. These ARFs and RMFs are for proposal planning purposes only. They should not be used for analysis of any real Chandra data. The Imaging Spectroscopy threads give instructions for building an observation-specific RMF and ARF.

2. The ACIS-I (FI) RMFs should be accurate to within a few percent between 0.5-6.0 keV. Below 0.5 keV, the effective area and gain for the FI devices is uncertain by 5-10%. Similar uncertainties apply above 6 keV. See the RESPONSE PRODUCTS RELEASE NOTES FOR ACIS for details.

3. The effective areas were derived for -120C ACIS focal plane temperature, and as such include CTI corrections in quantum efficiency valid for that temperature. These CTI corrections result in an energy-dependent QE gradient, which is visible in the effective area values at different distances from the readouts. Calculated count rates will be reasonably accurate without additional compensation for CTI when using these ARFs.