Here is a tarball containing the data used for analysis in Hayes, Scarlata, & Siana (2011) Nature 476, xxx. The following text is the README, also included in the tarball.

DOWNLOAD THE DATA

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Data Release README for Hayes, Scarlata, & Siana (2011) Nature, 476, 
304 - Central powering of largest Lyman-alpha nebula is revealed by 
polarized radiation. 

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In short, we release the reduced science data obtained with VLT/FORS
under programme ID 084.A-0954. For more information about how we 
arrived at this point, see the Supplementary Information of the paper.

In order to quantify the polarization level, one needs to split the 
incoming light into orthogonally polarized beams, known as the 
'ordinary' and 'extraordinary' beams. Further these beams are rotated 
to four different angles: 0, 22.5, 45, and 67.5 degrees. Thus there are
eight final science frames. These are in units of ADU/sec. 
Furthermore, in order to quantify the significance/error of each pixel,
each science frame has an associated error frame. This is supplied as 
the r.m.s. frame. Thus in reduced data we supply 16 frames.

Work with these frames and you will just see noise. 

In order to get a meaningful estimate of the polarization signal we 
binned the data using the adaptive binning method of Voronoi 
Tessellation. We used the code of Diehl & Statler (2006, MNRAS, 368, 
497). It is available here: 
	http://www.phy.ohiou.edu/~diehl/WVT/
We release also the binned versions of the 8 (or 16, depending on how 
you count) science frames. 

The polarization fraction (P) and angle (chi) follow from these 
frames, using some rather straightforward algebra, which is described
in the Supplementary Information and just about every paper on 
polarization. We release also the maps of P, and chi. Errors on these 
quantities are highly non-linear and asymmetric, and are estimated by
Monte Carlo simulation and integration of the p.d.f. These are 
also supplied at the 68% and 95% level.

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Get and inflate the tarball. It will create a directory called 
H11LabPolData/. 



Science frame nomenclature: 

  All files are called nnnn_XXXa_bbbb_ttt.fits 

  where: 
    nnnn = name (always lab1)
    XXX  = HWP angle [000,225,450,675] = [0.0, 22.5, 45.0, 67.5] deg
    a    = beam [o,e] = [ordinary,extraordinary]
    bbbb = bin? [bin,unbin]
    ttt  = type [sci,std] = [intensity frame,error frame]



A directory listing: 

  unbinned               - unbinned science data (16 frames)
  binned                 - binned science data (16 frames)
  lab1_000s_bin_s2n.fits - map of S/N in the binned intensity frames
  lab1_SigP.fits         - map of polarization fraction, P
  lab1_SigT.fits         - map of polarization angle, chi
  lab1_Std1P.fits        - map of 1 sigma error on P
  lab1_Std2P.fits        - map of 2 sigma error on P
  lab1_stack_fa.fits     - adaptively smoothed intensity frame
  mask.fits              - a mask to cut off the edges of the MOS
  plot_pol.py            - script for generating Figure 2 
  lab1_pol.pdf           - the output of plot_pol.py
  README.txt             - you have just finished reading it

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