ACS Prism/Grism Performance

As of January 23, 2003, the Cycle 11 Interim Calibration derived aXe configuration files are available from the ECF. (Link goes to the aXe User Manual.)

The web version of the November 2002 ST-ECF Newsletter features detailed articles about the grism mode of the ACS.

Raw HRC grism spectrum
The HRC G800L grism spectrum of the Wolf Rayet star WR45 acquired at the centre of the field of view. Exposure time is 60 s. The 0th, 1st and 2nd orders are visible from left to right. The tilt of the spectrum is 38 degrees to the detector X direction.
A. Pasquali, N. Pirzkal, J. R. Walsh (ST-ECF) 27 Jun 2002 (postscript)

Extracted HRC 1st order grism spectrum
The extracted, wavelength calibrated and background-subtracted 1st order spectrum of the Wolf Rayet star WR45 taken with the HRC and G800L grism.
A. Pasquali, N. Pirzkal, J. R. Walsh (ST-ECF) 27 Jun 2002 (postscript)

WFC grism sensitivity
The provisional sensitivity for the WFC G800L 1st order derived from the observations of GD 153 shown in wfc_lam.ps. For comparison, the theoretical computation of the sensitivity from the Instrument Handbook is shown.
A. Pasquali, N. Pirzkal, J. R. Walsh (ST-ECF) 27 Jun 2002 (postscript)

Raw WFC grism spectrum
The G800L grism spectrum of the Wolf Rayet star WR45 obtained at the centre of the WFC field of view. Exposure time is 20 s. The 0th, 1st, and 2nd orders are visible from left to right. Spectrum is tilted by 2 degrees to the detector X direction.
A. Pasquali, N. Pirzkal and J. R. Walsh (ST-ECF) 27 Jun 2002 (postscript)

Extracted WFC 1st order grism spectrum
The extracted, background subtracted and wavelength calibrated WFC G800L 1st order spectrum of the Wolf Rayet star WR45 from the image in wfc_wr45.ps.
A. Pasquali, N. Pirzkal, J. R. Walsh (ST-ECF) 27 Jun 2002 (postscript)

Extracted WFC grism spectrum
The extracted and background-subtracted WFC G800L 1st order spectrum of the White Dwarf GD153. The wavelength scale is from ground calibration only. The predicted count rate from the ACS spectroscopic ETC is shown for comparison.
A. Pasquali, N. Pirzkal, J. R. Walsh (ST-ECF) 27 Jun 2002 (postscript)

HRC prism sensitivity 1
The extracted spectrum of the White Dwarf GD71 was compared with the tabulated spectrum from Bohlin, Colina & Finlay (1995) to derive the absolute calibration for the HRC prism PR200L. The resulting sensitivity (green line) is compared with the theoretical calculation from the Instrument Handbook (dashed red line).
A. Pasquali, N. Pirzkal, J. R. Walsh (ST-ECF) 27 Jun 2002 (postscript)

HRC prism sensitivity 2
Whilst the in-orbit PR200L sensitivity matches the theoretical one rather poorly at wavelengths beyond 3500A (where the prism dispersion is highly non-linear), below 3500A the match is excellent as shown in this expanded view of prism_sens1.ps.
A. Pasquali, N. Pirzkal, J. R. Walsh (ST-ECF) 27 Jun 2002 (postscript)