The ST-ECF ACS Grism Hubble Legacy Archive Project

In 2006 the Space Telescope European Coordinating Facility (ST-ECF), together with its partners at the STScI and the CADC, started a project to build a Hubble Legacy Archive (HLA): a collection of high-level Hubble data products and access tools to ease scientific analysis in the age of the Virtual Observatory. The ST-ECF has focused on providing extracted spectra from slitless spectroscopy HST images. The slitless NICMOS G141 data were presented at previous ADASS meetings and have already been released. In this contribution we present an overview of the ongoing project of processing the ACS/WFC G800L data which cover a larger area and contain more spectra. There are around 150 ACS/WFC G800L datasets covering an area of ∼ 600 arcmin, and we expect to extract and publish about 20,000 fullycalibrated spectra. We discuss the techniques and methods that were developed to automatically extract the spectra from the observations and present a selection of ACS/WFC G800L spectra as examples. 1. The Hubble Legacy Archive The current Hubble Space Telescope (HST) data archives at the ST-ECF, the Canadian Astronomy Data Centre (CADC) and the Space Telescope Science Intstitute (STScI) offer images with calibrated pixel values for download. Further processing, such as the coadding of single images, must be done by the archive researcher individually. After almost 20 years of HST observations, a large amount of expertise has been accumulated for all past and currently-active HST instruments, and it is the right time to start building a Hubble Legacy Archive (HLA) containing high-level science data products for immediate scientific use (Walsh & Hook 2006). While the CADC and the STScI concentrate on providing image products (e.g. stamp images and cutout services), the contribution of the ST-ECF to the HLA focuses on the area of slitless spectroscopy. Currently the archives deliver slitless data with only basic calibration applied (bias, dark), hence the improvements of an HLA with science-ready spectra is large. NICMOS G141 slitless data (Freudling et al. 2008; Kummel et al. 2008) were part of the first data release in February 2008. Now we are working on the ACS/WFC G800L data, which are distributed over ∼ 150 separate datasets. Figure 1 shows the location of the data in galactic coordinates. Many of these datasets are close to each other and thus not individually recognizable. The sky coverage is ∼ 600 arcmin. 430 HLA ACS Grism Project 431 -75 -60 -45 -30 -15