1. ST-ECFAnnual Review March 14 2007 Instrument Science Activities
Jeremy Walsh
Wolfram Freudling
Martin Kümmel
Harald Kuntschner
Michael Rosa

2. Background Current instrument science activities
Spectroscopic instrument modelling:
STIS
UV line atlas for Pt/Cr-Ne hollow cathode lamp [5000 new lines]
ESO projects – CRIRES, X-Shooter
HST slitless spectroscopy – NICMOS & ACS
HLA NICMOS Slitless Spectroscopy Pilot Project
WFC3 slitless spectroscopy
14 March 2007
ST-ECF Annual Review

3. STIS calibration activities
Scientifically validating Instrument Model for the STIS FUV and NUV echelle modes
Assess improvements of model-based wavelength calibration v. calstis (on-going). Aim to replace calstis for these modes
Further options:
Use of model-based dispersion relations in spectral extraction (cross-dispersion profile)
Model based support for echelle flux calibration (blaze functions)
Coverage of other STIS spectral modes with benefit, such as long slit low dispersion
STIS FUV MAMA lamp
exposure
Model v. actual lamp
line positions
14 March 2007
ST-ECF Annual Review

4. STIS Calibration Enhancement
2D dispersion model applied to 200 E140H Echelle lamp calibration spectra. Central wavelength specified by one angle – grating tilt
Difference (obs-model) for grating tilt shows small offsets depending on the mode used, as well as a secular trend
14 March 2007
ST-ECF Annual Review

5. ACS slitless spectroscopy
Evolution from support for NICMOS slitless grism spectroscopy (since 1997)
Activities: ground and in-orbit calibration, extraction software, user support, documentation
Impact of ACS slitless modes (only current working HST UV-optical spectrometer since Aug 2004): in Cycle 14, ACS spectroscopy held 9.7% of awarded orbits
Science spin-offs: HUDF parallels – HRC and WFC (NICMOS parallel); GRAPES (Cycle 12); PEARS (Cycle 14)
January 2007 – loss of ACS WFC and HRC. Slitless mode with two prisms still available in Solar Blind Channel (SBC)
14 March 2007
ST-ECF Annual Review

6. Slitless spectroscopy from space
+ Low background from space
+ Continuous wavelength coverage – no atmospheric windows or emission lines > 1500Å
+ Compact PSF
= High sensitivity for point and compact sources
Low spectral resolution grisms but very sensitive for continuum break spectra
- Overlap of sources and contamination of spectra
- Larger objects have lower spectral resolution
[OII] z=1.38
[OIII] z=0.67
[OIII],Hαz=0.35
CIV],[CIII] z=3.19
Ly-αz=4.78
Xu et al 2007
Composite SN1a
spectrum at z>1
from Reiss et al
2007
14 March 2007
ST-ECF Annual Review

7. UV spectroscopy with ACS SBC prisms
PR110L, PR130L
Following a GO alert with red-star SBC spectra,
investigated possible ‘red leak’ of MAMA with spectra of blue/red standard stars. Cy16 calibration programme to better determine red sensitivity.
In-orbit λcalibration using Ly-α and CIV] in two QSO’s (z=0.09, 0.17); flux
calibration with standards
14 March 2007
ST-ECF Annual Review

8. SBC Contamination CheckWD
Our SBC prism calibration programme to check the red leak provided a check of the contamination post the January Side 2 fuse blow
Black is old data; Red is yesterday’s observation
=> No obvious loss in UV sensitivity 1σ 1σ
14 March 2007
ST-ECF Annual Review

9. software
Continue to support and develop aXe the slitless spectroscopy extraction package – available in STSDAS
Configuration and calibration files for NICMOS slitless spectra provide an alternative to the interactive NICMOSLook
Extensive use on science data – HUDF parallels, GRAPES, and PEARS programmes; SNae at z>1. IMPRS Ph.D. thesis on surveys with ACS parallel slitless spectra (B. Eder)
Spectra of dropout objects from Bouwens et al.; search for emission line sources
z~6.7
z=4.76
14 March 2007
ST-ECF Annual Review

10. NICMOS HLA Pilot Project
Pipeline reduction of all NICMOS G141 spectra
Developed PHLAG - Pipeline for HLA Grism
End to end approach: start with the raw data, end with extracted 1D spectra in the archive
Modular, not monolithic; consists of a series of reduction steps
Uses external software: SExtractor, pyraf, MultiDrizzle, aXe, aXe2web
Implemented in Python
14 March 2007
ST-ECF Annual Review

11. Modules of PHLAG data retrieval from ECF archive
basic processing (calnic) and enhancements (non-linearity correction; staypuft)
background subtraction
image combination (MultiDrizzle)
object detection (SExtractor)
spectral extraction (aXe)
quality control
metadata
data ingestion into HLA archive
14 March 2007
ST-ECF Annual Review

12. Image combination “Best” filter Using MultiDrizzle Standard settings
14 March 2007
ST-ECF Annual Review

13. Object detection SExtractor Conservative settings
Prime aim: get all objects for spectroscopy
“Reasonable” photometry
Boundary objects, splitting still problematic
14 March 2007
ST-ECF Annual Review

14. Spectral extraction: aXe software
14 March 2007
ST-ECF Annual Review

15. Example of a spectral extraction
input
intermediate steps
result
grism image
local backgr.
backgr. subtr.
stamp image
extracted spectrum
direct image
14 March 2007
ST-ECF Annual Review

16. Re-adjustment of trace
Filter wheel position is not reproducible
Require individual trace solution for every grism image
Fitting of object traces
Differences: ± 1pix over trace length
14 March 2007
ST-ECF Annual Review

17. Re-adjustment of wavelength zero point
readjusted
original
Shift determined with cross-correlation techniques
14 March 2007
ST-ECF Annual Review

18. Statistics / Status
PHLAG run 1.0 on all the NICMOS G141 data in December 2006
~ 1000 datasets (associations)
~ 5000 grism images
8 day of computing time
(single Linux box)
~ spectra
PHLAG run 2.0 in progress
14 March 2007
ST-ECF Annual Review

19. WFC3 UVIS channel – spare WFPC1 grism: G280 (200-500nm, @14A/pix)
IR channel – two grisms: G102 ( nm; 2.2nm/pix) and G141 ( nm; 4.1 nm/pix)
Agreement signed for undertaking comprehensive WFC3 grism calibration and support activities
2005 ground testing of UVIS and IR grisms (dispersion solutions, relative throughput). Two ISR’s
2006 replacement of IR grisms (out of focus from substrate distortion)
2007 testing of UVIS and IR grisms in ambient and Thermal Vacuum
14 March 2007
ST-ECF Annual Review