Introduction to Spitzer and some applications Data products Pipelines Preliminary work K. Nilsson, J.M. Castro Cerón, J.P.U. Fynbo, D.J. Watson, J. Hjorth.

Introduction to Spitzer and some applications

Data products

Pipelines

Preliminary work

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

spectrophotometry 50 – 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 ± 0.0069B) 0.9156 ± 0.0328 0.8956 ± 0.0328C) 1.7675 ± 0.0612 1.6675 ± 0.0621

OURS

SSCD) 1.3682 ± 0.1080 1.2661 ± 0.1055E) 0.7336 ± 0.0428 0.7116 ± 0.0401F) 1.2188 ± 0.0471 1.1800 ± 0.0442

GRB hosts: faint, blue sub-mm galaxies

GRB hosts: faint, blue sub-mm galaxies

Ly-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