The WFC3 grism mode

Besides imaging, WFC3 offers slitless spectroscopy on both the ultra-violet/optical (UVIS) and infrared (IR) channels. The UVIS channel is equipped with the G280 grism, which has a resolving power R~70 in the wavelength range 200-400nm. The IR channel includes the grisms G102 and G141 with resolving powers R~210 in the range 800-1150nm and R~130 in the range 1100-1700nm, respectively. Further information on WFC3 is available on the WFC3 STScI pages.

The WFC3 simulation application

The ST-ECF is responsible for supporting the WFC3 slitless spectroscopic modes. As part of this support, we have developed aXeSIM, a dedicated software package to simulate 2-dimensional WFC3 slitless spectroscopic images. In order to mimic observational data very closely, aXeSIM also can optionally produce a matching direct image (through a user-selected filter) for each slitless image.

aXeSIM is distributed as a PyRAF/IRAF package and operates from within any recent version of PyRAF. In addition, aXeSIM for WFC3 is available via a Web application. Without any registration the user can select a WFC3 slitless mode, choose or adjust additional parameters and start the simulation. Once ready, the simulation images and data can then be downloaded from the web. The web interface targets new, less experienced or occasional users and offers a subset of all options existing in aXeSIM.

Disclaimer

The WFC3 slitless image simulator was developed independently of the STScI Exposure Time Calculator (ETC). While every effort has been made to ensure that the imaging simulator provides similar estimates of detected counts to the ETC, differences are bound to result. The STScI ETC is to be taken as the official tool and should be used to determine exposure times for the purposes of critical time justification in Phase I and II. The WFC3 ETC can be found here.

The following link allows to simulate WFC3 slitless images via a Web application:

More information on the Web application of aXeSIM and help pages can be found at Slitless spectroscopy simulations.

To download the complete PyRAF/IRAF package of the simulation software follow the link below:

WFC3 calibration

The configuration and calibration files presented on this page were derived from data taken during WFC3 thermal vacuum 2 testing in summer 2007. They are in the correct format to be used with the aXe simulation software aXeSIM and the aXe extraction software aXe. To use these calibration products with aXe and aXeSIM, copy them into a directory and set your AXE_CONFIG_PATH environment variable to point to that directory.

UVIS/G280 grism

• configuration file: WFC3.UV.CHIP1.TV2_sim.conf
• sensitivity 1st order: wfc3_abscal_UVg280_1st_sens.fits
• sensitivity 0th order: wfc3_abscal_UVg280_0th_sens.fits
• sensitivity -1st order: wfc3_abscal_UVg280_-1st_sens.fits
• sensitivity -2nd order: wfc3_abscal_UVg280_-2nd_sens.fits
• sensitivity 2nd order: wfc3_abscal_UVg280_2nd_sens.fits
• sensitivity -3rd order: wfc3_abscal_UVg280_-3rd_sens.fits
• sensitivity 3rd order: wfc3_abscal_UVg280_3rd_sens.fits
• sensitivity -4th order: wfc3_abscal_UVg280_-4th_sens.fits
• sensitivity 4th order: wfc3_abscal_UVg280_4th_sens.fits

IR/G102 grism

• configuration file: WFC3.IR.G102.TV2_sim.conf
• sensitivity 1st order: wfc3_abscal_IRg102_1st_sens.fits
• sensitivity 0th order: wfc3_abscal_IRg102_0th_sens.fits
• sensitivity 2nd order: wfc3_abscal_IRg102_2nd_sens.fits

IR/G141 grism

• configuration file: WFC3.IR.G141.TV2_sim.conf
• sensitivity 1st order: wfc3_abscal_IRg141_1st_sens.fits
• sensitivity 0th order: wfc3_abscal_IRg141_0th_sens.fits
• sensitivity 2nd order: wfc3_abscal_IRg141_2nd_sens.fits
• sensitivity 3rd order: wfc3_abscal_IRg141_3rd_sens.fits

 

Maintained by Harald Kuntschener <hkuntsch@eso.org>