Spitzer Space Telescope - Archive Research Proposal #40847


A Reanalysis of IR Background Fluctuations in Spitzer IRAC GOODS fields

Principal Investigator: Asantha Cooray
           Institution: University of California Irvine

     Technical Contact: Asantha Cooray, University of California Irvine

Co-Investigators: 
Ranga Chary, Caltech                                                  
Mark Dickinson, NOAO                                                  
James Davies, NOAO                                                    
Henry Ferguson, STScI                                                 
James Bock, Caltech/JPL                                               
Ian Sullivan, Caltech                                                 
Daniel Stern, JPL/Caltech                                             
Elizabeth Barton, UC Irvine                                           
Alexandre Amblard, UC Irvine                                          
Devdeep Sarkar, UC Irvine                                             
Edward Wright, UCLA                                                   
Stefano Casertano, STScI                                              

Science Category: cosmic infrared background 
Dollars Approved: 66973 

Abstract:
We propose a reanalysis of IRAC GOODS HDF-N and CDF-S data to measure clustering
of the unresolved IR background (IRB) present in "empty" pixels. These
clustering measurements will be used to study any indications for the presence
of an unresolved, diffuse IR background from redshifts related to reionization
and associated with redshifted UV emission from first-light galaxies. We will
improve previous analyses by cross-correlating unresolved IR fluctuations
between different IRAC channels to determine if the color of unresolved
fluctuations are consistent with spectra expected for first-light galaxies
containing Population III stars. The cross-correlation analysis will also allow
us to separate various noise and systematic effects that are not common to IRAC
passbands. A significiant effort in this proposed program will be to understand
statistical errors and systematic uncertainties in fluctuation measurements.
Given first-light galaxy fluctuations cluster at 10 arcminute angular scales and
individual IRAC images are limited to 5 arcminutes, we will remosaic GOODS BCDs
by inserting simulated patterns of first-light galaxies and measure clustering
in new mosaics to see if we recover the input fluctuations and to establish the
accuracy of diffuse backgrounds in the mosaic. For fluctuation measurements, we
will also implement a likelihood analysis of IR images to measure the power
spectrum of anisotropies in multipole space. These techniques are commonly used
in CMB studies and are optimized to handle issues associated with complex mask
and window functions that are applied to images. With such a technique we can
directly address if our existing procedure based on Fourier transforms leads to
biased estimates of clustering or not. Data products involving masked images,
new mosaics of GOODS, and software to measure clustering will all be made
publicly available, as we have done in the past in our similar studies.