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Data products Pipelines Preliminary work. Introduction to Spitzer and some applications. K. Nilsson, J.M. Castro Cerón, J.P.U. Fynbo, D.J. Watson, J. Hjorth and A.L. Aguilar Minor. - launched 25 August 2003; Cape Ca ñ averal, Florida (USA) - 2.5 year mission (nominal length; 5+ expected)

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Introduction to Spitzer and some applications

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Data products

Pipelines

Preliminary work

Introduction to Spitzer and some applications

K. Nilsson, J.M. Castro Cerón,

J.P.U. Fynbo, D.J. Watson, J. Hjorth and A.L. Aguilar Minor


- launched 25 August 2003; Cape Cañaveral, Florida (USA)

- 2.5 year mission (nominal length; 5+ expected)

- 0.85 m telescope

- 3 cryogenically cooled science instruments (< 5.5 K)

- wavelengths:imaging/photometry 3 – 180 m

spectroscopy 5 – 40 m

spectrophotometry50 – 100 m

- diffraction limit:6.5 m


Instrumentation

IRAC: InfraRed Array Camera

- provides images at 3.6, 4.5, 5.8 and 8.0m

- dual band imaging via dichroic beamsplitters

IRS: InfraRed Spectrograph

- low resolution: 5.2 to 38.0m

- high resolution 9.9 to 37.2 m

MIPS: Multiband Imaging Photometer for Spitzer

- photometry, super resolution imaging and efficient mapping

- three wavelengths centred near 24, 70 and 160m

- low resolution spectrography: 55 to 95 m


Observation planning

SPOT: a publicly available software package used by Spitzer observers to plan observations and submit proposals.

Data archive

LEOPARD: a publicly available software package used to download data.


Data products

RAW

- unprocessed data packaged into a FITS format

- calibration data is also provided

BCD (basic calibrated data)

- single frame FITS format data products

- removal of known instrumental signatures necessary

(dark subtraction, multiplexer bleed, detector linearisation, flat fielding and cosmic ray detection)

- calibrated in scientifically useful units

Post BCD

- in each wavelength this processing yields corrected images co-added into a mosaic and a list of extracted point sources


Pipelines

RAW -> BCD

- no pipeline is publicly available at this time

- SSC pipe linked to many external libraries/modules

- will not work outside SSC

- user is alone

BCD -> Post BCD

- publicly available

- made up of several modules (Perl scripts)

- Linux and/or Solaris


Post BCD modules (IRAC ch1/2(3/4))

COSMETIC FIX

- fixes two artifacts present in IRAC

*multiplexer bleeding: enhanced output level pixels trailing a bright spot

*column pull down: intensity reduction of the signal at ~35,000 DN

- optional background subtraction

FLAT FIELD CORRECTION

- creates a flat field for one set and applies it to images in the set

BACKGROUND MATCHING/OVERLAP

- cumulative pixel by pixel difference between overlapping areas for all pairs is minimised with respect to unknown constant offsets of the input

- interpolation is linear -> offset is conserved


POINTING REFINEMENT

- improves the pointing provided by the on-board star tracker by minimising discrepancies between positions of point sources matched in each pair of images

- relative (self consistent images) or absolute (usually 2MASS)

MOSAICING (with/out outlier detection)

- interpolation and co-addition of input images onto a common grid

- area overlap interpolation is performed

- drizzle interpolation is implemented

- correction for optical distortion in the input images is applied during interpolation

ASTRONOMICAL POINT SOURCE EXTRACTION

- multi-frame and single-frame point source extraction

- for multi-frame, the extraction is performed on co-added image


BANDMERGING

- reads two to seven input ASCII table files of single band point source information and produces a list of band combinations


A)

-0.8233± 0.0072

-0.8144 ± 0.0069

B)

0.9156 ± 0.0328

0.8956 ± 0.0328

C)

1.7675 ± 0.0612

1.6675 ± 0.0621

OURS

D)

1.3682 ± 0.1080

1.2661 ± 0.1055

E)

0.7336 ± 0.0428

0.7116 ± 0.0401

F)

1.2188 ± 0.0471

1.1800 ± 0.0442

SSC


GRB hosts: faint, blue sub-mm galaxies


GRB hosts: faint, blue sub-mm galaxies


Lya-selection of high redshift galaxies


GOODS – Great Observatories Origins Deep Survey

Joint effort of NASA, ESO, ESA, NOAO...

”Great observatories”: Spitzer, HST, VLT, CXO, XMM...

Goal is to ”study galaxy formation and evolution over a wide range of redshifts and cosmic look-back time”.

Two fields with deep observations: HDF-N and CDF-S (and HUDF).


HST vs. Spitzer – the battle of giants


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