HST Archival Studies of HH 30 WFPC2 Data Retrieval and Reduction Liu, Jimmy Chun-Fan Supervisor: Dr....
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Transcript of HST Archival Studies of HH 30 WFPC2 Data Retrieval and Reduction Liu, Jimmy Chun-Fan Supervisor: Dr....
HST Archival Studies of HH 30WFPC2 Data Retrieval and Reduction
Liu, Jimmy Chun-Fan
Supervisor: Dr. Shang, Hsien
August 23, 2002
Summer Student Program 2002 Oral Presentation
August 23, 2002 2
Outline
• HH 30 : The Herbig-Haro Object
• HST Archive Overview
• WFPC2 : The Instrument Performance
• Data Reduction
Studies based on
“Hubble Space Telescope Observation of the Disk and Jet of HH 30”, Burrows et al, ApJ 473 437, Dec 1996
August 23, 2002 3
The Herbig-Haro Objects
• Nebulosities with high speed relative to the surroundings.
• Cataloged independently by G. Herbig and G. Haro in the early 1950’s.
• Now is extended to a protostellar system with jets.
August 23, 2002 4
1000 A.U.
1000 A.U.
1000 A.U.
August 23, 2002 5
“My” Object - HH 30
• RA : 4h31m37s.60• Dec : +18:12' 26".0• Constellation : Taurus• Distance ~ 140 pc• Extension in the sky :
5' NNE(1995) ; 3' SSW(1990)
• WHY we choose HH30 ?
August 23, 2002 6
© Lisa Chien
5º
Accretion Disk
“Counterjet”
Reflection Nebulosities Jet
Protostar
Why the Shape ?
Observer
August 23, 2002 7
HST Archive Search Quick guide
1. Register a one-year-valid account.
2. Search for what you need from searching form.
3. Mark the datasets you want for scientific use.
4. Choose the method of retrieving data (via ftp is a good choice in IAA).
5. Receive letter regarding data storage status.
6. Retrieve datasets via anonymous ftp
(ftp archive.stsci.edu).
August 23, 2002 8
HST Archive Search Form
• Web-based Search Form: archive.stsci.edu/cgi-bin/hst/– Handy and convenient.
• StarView: A software handling dataset search and retrieval.– The search criteria can be more specified.
August 23, 2002 9
HST Archive Search
Specify object nameSpecify object name
Radius from the specified objectRadius from the specified object
Exposure timeExposure time
The data can only be publicly accessible after this date
The data can only be publicly accessible after this date
The “color” of the image can be chose
The “color” of the image can be chose
August 23, 2002 10
What to Retrieve ?
“Cleaned” data“Cleaned” data
Calibrating filesCalibrating filesRaw dataRaw data
Calibrated dataCalibrated data
Pipeline Calibration (According to CCD properties)
Pipeline Calibration (According to CCD properties)
Data Reduction(Cosmic Rays, CCD performance)
Data Reduction(Cosmic Rays, CCD performance)
Recalibrate myselfRecalibrate myself
Data AnalysisData Analysis
Prepare for Data ReductionPrepare for Data Reduction
August 23, 2002 11
Question:
How do we go from to ?
Before…After…
Or Furthermore…
M16 - The Eagle Nebula
©STScI
August 23, 2002 12
Wavelength specified by “Filter”
Why WFPC2 (pronounced as WiFPiC-2) ?
NICMOS20355Å
WFPC25047Å
WFPC27940Å
Processed using PowerPoint by Lowering Brightness and Lifting Contrast
August 23, 2002 13
The Wide-Field and Planetary Camera 2
• 4 camera combined: 800×800 pixels– PC: 0.0455" per pixel > Higher resolution for planets– WF2,3,4: 0.0996" per pixel > Wide filed of view
• CCD Performance:– QE: 14% in the red (peak)– A-to-D gain (5 or 7 e-/DN)– Read noise: 5~6 electrons
• Camera Performance– Undersampling
WF2
WF4
PC
WF3 1'
August 23, 2002 14
Undersampling: What and Why ?
• What ?– 70% of the starlight hit the ONE center pixel– Stars look extremely sharp in the CCD
• Why ?– Pixel too large: technique limit– Point Spread Function (PSF) too narrow:
GOOD seeing in the space!
• Why should I care ?
August 23, 2002 15
Data Reduction Procedure for WFPC2
• Using Image Reduction and Analysis Facilities (IRAF) developed by NOAO
• Cosmic rays rejection
• Warm pixels fixing
• Streaks (due to charge trapping of CCD)
August 23, 2002 16
Cosmic rays
Cosmic rays or faint stars?
“dark” streak
Star and “bright” streak
August 23, 2002 17
Cosmic Ray “Pick-up” Strategy
• Many images with sub-pixel offset– Dithering (dividing pixels)
• Many images with the same field of view and the same exposure time– crrej task of IRAF/STSDAS
• What if I only have ONE single frame?– cosmicrays task in IRAF/STSDAS– other method suggested (e.g. edge detection, etc.)
August 23, 2002 18
Datasets Regarding the Paper
• 1994 data • F555W 5407Å; 350sec exposure 1 image• F675W 6714Å; 120sec exposure 1 image• F814W 7940Å; 60sec exposure 1 image
– Try cosmicrays task
• 1995 data• F675W 6714Å; 800sec exposure 2 images • F814W 7940Å; 1200sec exposure 2 images
– Use crrej task
August 23, 2002 19
The 1994 Data Results (F555W)
August 23, 2002 20
U2KY0101T U2KY0102T
• Please compare these two images
Two Exposures of 1995 at 6714Å
August 23, 2002 21
The 1995 Data Results (F675W)
Trial 1 Trial 5
August 23, 2002 22
Comparison with Paper
Burrows et al, 1996
August 23, 2002 23
Future Work
• Deconvolution of the images
• Data analysis: reproduce Burrows’ results– Photometry of the knots– Astrometry (position, proper motion, etc)
• Further data analysis from different cameras of HST
August 23, 2002 24
Acknowledgement
• Dr. Shang for guideline and project direction.• Drs. Andrew Wang and S-Y Wang for CCD
knowledge.• Dr. Yen and Mr. Hsieh for IRAF discussions.• Computer Guys for problem solving!• Mei-Yin and Hsin-Lun for help and discussions.• Summer Students for mutual supports.• Our “baby-sitters”: Dr. King and Ken Chen! • And others who helped me in IAA.