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Introduction to Reducing HST Data Version 6.0 March, 2006 Introduction to Reducing HST Data Space Telescope Science Institute 3700 San Martin Drive Baltimore, Maryland 21218 [email protected] Operated by the Association of Universities for Research in Astronomy, Inc., for the National Aeronautics and Space Administration User Support For prompt answers to any question, please contact the STScI Help Desk. • E-mail: [email protected] • Phone: (410) 338-1082 (800) 544-8125 (U.S., toll free) World Wide Web Information and other resources are available on the Web site: • URL: http://www.stsci.edu. Revision History Version Date Editors 1.0 February 1994 Stefi Baum 2.0 December 1995 Claus Leitherer 3.0, Vol.. I October 1997 Mark Voit 3.0, Vol.. II October 1997 Tony Keyes 3.1 March 1998 Tony Keyes 4.0 January 2002 Bahram Mobasher, Chief Editor, HST Data Handbook Michael Corbin, Jin-chung Hsu, Editors, HST Introduction 5.0 July 2004 Diane Karakla and Jennifer Mack, Editors, HST Introduction. Susan Rose, Technical Editor, HST Introduction. 6.0 March 2006 Diane Karakla, Editor, HST Introduction. Susan Rose, Techni- cal Editor, HST Introduction. Contributors to V 6.0: Inga Kamp, Dorothy Fraquelli, Al Holm, Brian McLean. Send comments or corrections to: Space Telescope Science Institute 3700 San Martin Drive Baltimore, Maryland 21218 E-mail:[email protected] Table of Contents Preface .................................................................................... vii Chapter 1: Getting HST Data............................. 1-1 1.1 Archive Overview ....................................................... 1-2 1.1.1 Archive Registration................................................. 1-3 1.1.2 Archive Documentation and Help ............................ 1-4 1.2 Getting Data with StarView...................................... 1-4 1.2.1 Downloading and Setting Up StarView.................... 1-4 1.2.2 Simple Use of StarView........................................... 1-5 1.2.3 Marking and Retrieving Data with StarView ............ 1-9 1.2.4 Using StarView to Retrieve Calibration Files and Proposal Information and for Duplication Checking ... 1-10 1.2.5 Advanced Features of StarView ............................ 1-12 1.2.6 StarView and the Visual Target Tuner................... 1-14 1.2.7 Quick Proprietary Data Retrieval with StarView .... 1-14 1.3 Getting Data with the World Wide Web .............. 1-15 1.3.1 WFPC2 Associations............................................. 1-17 1.3.2 High Level Science Products................................. 1-19 1.4 Reading HST Data Disks ....................................... 1-20 Chapter 2: HST File Formats............................. 2-1 2.1 FITS File Format ........................................................ 2-2 2.1.1 Working with FITS Image Extensions...................... 2-3 2.1.2 Working with FITS Table Extensions....................... 2-8 2.2 GEIS File Format...................................................... 2-11 2.2.1 Converting FITS to GEIS....................................... 2-13 2.2.2 GEIS Data Groups................................................. 2-13 2.2.3 Working with GEIS Files........................................ 2-15 2.2.4 The “waiver” FITS Format...................................... 2-17 iii iv Table of Contents Chapter 3: Analyzing HST Data ...................... 3-1 3.1 Alternative Means of Accessing HST Data.......... 3-2 3.1.1 Interactive Data Language (IDL) ............................. 3-2 3.1.2 Python...................................................................... 3-2 3.1.3 Fortran and C........................................................... 3-3 3.1.4 Java ......................................................................... 3-3 3.1.5 PyRAF ..................................................................... 3-3 3.2 Navigating STSDAS .................................................. 3-4 3.2.1 STSDAS Structure................................................... 3-4 3.2.2 Packages of General Interest .................................. 3-6 3.3 Displaying HST Images ............................................ 3-7 3.3.1 The Display Task..................................................... 3-7 3.3.2 Working with Image Sections ................................ 3-10 3.4 Analyzing HST Images ........................................... 3-11 3.4.1 Basic Astrometry.................................................... 3-12 3.4.2 Examining and Manipulating Image Data.............. 3-14 3.4.3 Working with STIS, ACS, and NICMOS Imsets..... 3-16 3.4.4 Photometry ............................................................ 3-19 3.4.5 Combining Dithered HST Datasets with MultiDrizzle ......................................................... 3-22 3.5 Displaying HST Spectra ......................................... 3-24 3.5.1 Specview ............................................................... 3-24 3.5.2 STIS Spectra ......................................................... 3-25 3.5.3 FOS and GHRS Spectra........................................ 3-26 3.5.4 Producing Hardcopy .............................................. 3-27 3.6 Analyzing HST Spectra........................................... 3-29 3.6.1 Preparing STIS Spectra for Analysis in IRAF/STSDAS or Pyraf .......................................... 3-29 3.6.2 Preparing FOS and GHRS Data............................ 3-32 3.6.3 Photometry ............................................................ 3-35 3.6.4 General Tasks for Spectra..................................... 3-35 3.6.5 STSDAS Fitting Package ...................................... 3-38 3.6.6 Specfit.................................................................... 3-41 3.7 References ................................................................ 3-41 3.7.1 Available from STScI ............................................. 3-41 3.7.2 Available from NOAO ............................................ 3-42 3.7.3 Other References Cited in This Chapter ............... 3-42 Table of Contents v Appendix A: IRAF Primer .....................................A-1 A.1 Initiating IRAF ..............................................................A-2 A.2 IRAF Basics..................................................................A-4 A.3 Getting IRAF and STSDAS ....................................A-14 Appendix B: HST File Names ...........................B-1 B.1 Rootnames ...................................................................B-3 B.2 Suffixes of Files Common to All Instruments .......B-4 B.3 Associations .................................................................B-5 Appendix C: Observation Logs ......................C-1 C.1 Observation Log Files................................................C-1 C.2 Retrieving Observation Logs .................................C-11 C.3 Using Observation Logs..........................................C-12 Index .................................................................................Index-1 vi Table of Contents Preface The HST Data Handbook is comprised of three separate sections which are merged together to form a single document: • Part I is a general introduction which describes the process of retrieving and reducing Hubble Space Telescope (HST) data. • Part II is an instrument-specific document which describes the reduction procedures, calibrations, and sources of error specific to each active HST instrument. • Part III is a general set of appendices which includes an IRAF primer, a description of HST file names, and a summary of the obser- vation log files. Use of HST data necessarily involves using software to retrieve, analyze, and view it. With regard to analysis and visualization, there are many different tools and packages available. It would be impractical for a handbook to show how to do this for all available software. Since much of the software developed by STScI for calibrating, analyzing, and visualizing HST data has been based on the IRAF system, the focus of this handbook will be on use of IRAF, STSDAS, and TABLES for doing so. Chapter 3 will briefly mention other software tools for accessing HST data and where to get more information about these tools. PyRAF is a new command language (CL) for IRAF and, as such, allows the use of almost all IRAF tools. It is briefly discussed in Chapter 3, but for the most part, the IRAF examples given will work exactly the same in PyRAF. The specifics of the data produced by each of the four active instruments, FGS, WFPC2, NICMOS, and ACS, are described in separate versions of Part II. A fifth version exits for STIS which recently failed in 2004. The general information in Parts I and III, referred to as ‘the introductory chapters’, are tacked onto the beginning and end of each instrument-specific part. We recommend a careful reading of the introductory chapters before proceeding to the instrument-specific section and before starting to work on your HST data. The present introductory chapters are based on information available as of January 2006. Several changes in the HST Data Archive and data reduction software have occurred since the last revision of the HST Data Handbook introductory chapters. vii viii Preface Future changes in this handbook are anticipated as the Multimission Archive at STScI (MAST) expands to cover additional missions, and as StarView, PyRAF, and STSDAS software continue to evolve. The reader is advised to consult the STScI web site at http://www.stsci.edu/hst for the latest information. (Editor, HST Introduction) CHAPTER 1: Getting HST Data In this chapter... 1.1 Archive Overview
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