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

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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.

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1000 A.U.

1000 A.U.

1000 A.U.

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“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 ?

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© Lisa Chien

5º

Accretion Disk

“Counterjet”

Reflection Nebulosities Jet

Protostar

Why the Shape ?

Observer

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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).

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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.

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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

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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

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Question:

How do we go from to ?

Before…After…

Or Furthermore…

M16 － The Eagle Nebula

©STScI

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Wavelength specified by “Filter”

Why WFPC2 (pronounced as WiFPiC-2) ?

NICMOS20355Å

WFPC25047Å

WFPC27940Å

Processed using PowerPoint by Lowering Brightness and Lifting Contrast

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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'

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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 ?

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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)

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Cosmic rays

Cosmic rays or faint stars?

“dark” streak

Star and “bright” streak

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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.)

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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

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The 1994 Data Results (F555W)

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U2KY0101T U2KY0102T

• Please compare these two images

Two Exposures of 1995 at 6714Å

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The 1995 Data Results (F675W)

Trial 1 Trial 5

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Comparison with Paper

Burrows et al, 1996

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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

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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.