Space Telescope Science Institute (STScI)
3700 San Martin Drive
Baltimore, MD 21218
Slitless spectroscopy with HST has come to the forefront in recent years with a growing fraction of telescope time being allocated to this mode, especially in the most recent Cycle 18. The WFC3 IR grisms have been receiving much of the attention but ACS and STIS also have slitless modes, and an extensive set of NICMOS grism observations are also available in the archives. In addition, the aXe software developed at ST-ECF (Space Telescope European Coordinating Facility) now makes it much easier to reduce slitless spectroscopy. For example, this software has been used to extract spectra for 32,149 different objects based on ACS G800L data and 1,923 targets for NICMOS G141 observations.
STScI, in collaboration with the ST-ECF and ESA, held a two day workshop on November 15 - 16, 2010 to support reduction and analysis of slitless spectroscopy. Both experts and beginners were invited. The workshop worked through specific data sets from start to finish using the aXe software, and also provided opportunities for people to present and discuss details of their own analysis.
Participants were able to download the software, cookbook, and relevant datasets before arriving at the workshop.
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|Monday, November 15||Workshop||9:00 a.m. - 5:00 p.m.|
|Tuesday, November 16||Workshop||9:00 a.m. - 3:00 p.m.|
Please see Workshop Agenda for a full breakdown of sessions.
Speaker: Hakim Atek
Abstract: The WISP Survey is a large pure-parallel program that is obtaining WFC3 slitless spectra with G102 and G141 over > 500 orbits. I will present the characteristics of the data reduction in parallel mode, and how to deal with some specific problems. I will also show more general results about the WFC3 IR grism spectroscopy performance.
Speaker: John OMera
Abstract: In addition to the G102 and G141 infrared grisms, WFC3 has a UV sensitive grism, the G280. I present data from our snapshot program to survey for Lyman limit systems that showcase the G280 data, and briefly discuss data characteristics and extraction challenges.
Speaker: Benjamin Weiner
Abstract: The sensitivity and field of view of the WFC3-IR grisms make it possible to carry out sizable infrared spectroscopic surveys from space. I will discuss why one would want to do such a thing, and some of the advantages and pitfalls that are encountered during survey and data reduction, focusing mainly on the example of observing emission line galaxies at redshift ~1.
Brad Whitmore (Chair)
(Cosponsored by STScI and ESA)
For the practical exercise we will take you through a standard data reduction of the WFC3/G141 grism data from the Early Release Science program (see Straughn et al. 2010, AJ accepted, arXiv:1005.3071) by making use of the aXe software package developed by the ST-ECF. A full manual (pdf) for aXe is available. However, we have also prepared a step-by-step cookbook (pdf) for the WFC3/G141 dataset, which we would recommend you to read prior to the workshop.
In order to be able to participate in the practical exercise you must have installed the following software on your laptop:
IRAF version 2.14
PYRAF with STSDAS version 3.12
Note, that aXe version 2.1 is part of STSDAS 3.12 if you are using a Linux system. For Mac OSX you can either install the aXe binaries or install the full scisoft package (version 2010.10.2b) provided by Nor Pirzkal (for Mac OSX 10.6 only).
In order to enable the final step of the cookbook (data visualization) you will require the tool aXe2web, version 1.2.
Furthermore, it is essential to download, prior to the workshop, the WFC3/G141 dataset (~70MB) required for the practical exercise. On the second day of the workshop we will be available for consultation on more detailed aspects of reducing and calibrating WFC3 and ACS slitless data.
If you have any questions concerning the aXe software and/or installation please send an email. We look forward to seeing you at the workshop.