1. The Hubble Legacy Archive (HLA) Slitless Spectroscopy Project
Jeremy Walsh,
Martin Kümmel & Harald Kuntschner, ST-ECF
STScI Slitless Spectroscopy Workshop November 2010

2. The Hubble Legacy Archive (HLA)
The HLA is a joint project between STScI, CADC and ST-ECF to create well-calibrated HST science data and make them accessible via user friendly interfaces
Exploiting our expertise we decided to concentrate on slitless spectra, first from NICMOS then ACS
Since routinely calibrated 1D and 2D spectra from these modes were not publically available, contribute a unique science product

3. NICMOS G141 spectra l,b distribution of pointings of
NICMOS had 3 grisms (G096, G141 and G206)
G141 (1.1 – 1.9μm) most used
Variety of programmes from nearby cool dwarfs to high redshift QSOs
Interactive extraction software developed at ST-ECF (NICMOSLook)
Developed automatic PHLAG pipeline to form associations of well-aligned pointings (800), combine images, run Sextractor on combined direct images, extract 1D and 2D spectra with aXe as the engine*
l,b distribution of pointings of
NICMOS HLA released spectra
*Config. file for G141

4. NICMOS HLA G141 spectra
Quality checks – comparison to 2MASS photometry and direct / spectroscopic mags
Human evaluation of all released spectra
Rich metadata added
1923 spectra released in 2008
Freudling et al. 2008, A&A, 490, 1165

5. ACS G800L archive
Following-on from NICMOS HLA release turned to ACS. WFC G800L most used grism – pointed (GRAPES, PEARS) and parallel programmes
153 spatial grism associations identified (out of 168 possible) but x40 increase in number of extracted spectra over NICMOS
Alignment of direct images (tweakshifts) and combination (multidrizzle)
Absolute astrometry by cross correlation with reference catalogues – GSC2, UCAC2, ... → <0.3’’ accuracy
Distribution of 153 ACS
associations in Galactic
coordinates

6. ACS G800L processing PHLAG pipeline amended for ACS
Generation of deep detection ‘white light’ image for each association
SExtractor catalogues in multiple bands (F430W … F850LP, as available)
Quality control of image data to ensure best alignment
fluxcube method used for contamination estimation
Combination of 2D drizzled spectra with aXedrizzle

7. HLA ACS QC of spectra
For imaged stars, compared extracted spectrum with K-M templates → derived wavelength correction per association
Compared direct image mags and synthesized grism mags
Pre-release of 1235 spectra in HUDF parallel fields released in 2009
73581 spectra extracted in total
Based on training set of 2020 randomly selected spectra, classified ‘good’ and ‘bad’ by 4 separate pairs of eyes
weka automatic classification algorithm used to extend training set to whole sample
Final HLA release of spectra in May 2010

8. HLA ACS G800L release
Characterisation of released spectra in terms of emission line flux limits by comparison with ESO GOODS spectra in CDFS
Concise summary page for each target
Release of spectra on STScI HLA site with spatial footprints
Kümmel et al in prep. To be submitted to A&A.