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aXe
Simulating Slitless Spectra with aXeSIM

aXeSIM

A dedicated simulation software package aXeSIM has been developed as part of the support for the WFC3 slitless spectroscopic modes. However, aXeSIM can also simulate spectral images for other slitless spectroscopic instruments, and has been used, for example, in the planning of observations with JWST NIRISS and Euclid NISP.

Software Access

aXeSIM is available in two forms:

1. As a sub-package of STSDAS.

aXeSIM is distributed along with aXe as a sub-package of STSDAS (from STSDAS v3.10 onward). The latest version of aXeSIM (v1.4) was released in STSDAS v3.12 in June 2010. Starting with aXeSIM version 1.4 and aXe version 2.1, the two packages have been united at the code level.

To verify an aXeSIM installation and to help users taking their first steps with aXeSIM, we have composed test packages for some HST instruments with slitles spectroscopic observing modes.

Please download the tarball, unpack it and follow the instructions in the README file.

2. For the simulation of WFC3 UVIS and IR grism spectra, aXeSIM is also available via the aXeSIMweb application.

In addition to the aXeSIM task that is available in STSDAS, aXeSIM can also be run as a web application for the WFC3 grism modes. The web application offers only a subset of all the options available in aXeSIM in order to simplify use for new, less experienced or occasional users of the software. The user can select a WFC3 slitless mode, choose or adjust additional parameters and start the simulation. Once ready, the simulated images and data can then be downloaded from the web.

Disclaimer: aXeSIMweb was developed independently of the STScI WFC3 spectroscopic Exposure Time Calculators (ETC). While every effort has been made to ensure that aXeSIMweb provides similar estimates of detected counts as the ETC, differences will inevitably 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 HST Phase I and II proposals.

What's New?

Documentation

The aXeSIM Users’ Manual describes how aXeSIM works and how to perform simulations with it. It is available for browsing and download in three formats: