XMM-Newton Science Analysis System


eimsimreduce (eimsim-2.4) [xmmsas_20190531_1155-18.0.0]

For each of the input source-list columns X and Y: a histogram of position against flux

These are not so much histograms as binned averages of various position-related quantities at a series of values of detected flux. This pair of histograms is written to tables X_VS_S and Y_VS_S in the output data set.

Log10 of the flux values are taken before the binning process is begun.

A description of the columns written (taking again the $Y$ spatial coordinate as the example) is as follows:

• FLUX_MID: $i$th value given by $10$ to the power of $(\log_{10}[S_{i+1}]+\log_{10}[S_i])/2$ where $S$ is taken from column FLUX.

• Y_DIFF: the bin-averaged value of Y - SIM_Y.

• Y_DIFF_STDDEV: for each bin, the standard deviation $\sigma$ of the values of Y - SIM_Y which fall within that bin, according to the formula

  
  

  $$\sigma^2 = \frac{1}{N-1} \sum_{i=1}^N (\Delta p_i - <\Delta p>)^2$$
  
  

  where $\Delta p = p_\mathrm{det}-p_\mathrm{sim}$ and $N$ is the number of values within the bin. $\sigma$ is of course undefined for $N<2$.

• Y_DS_ERR: a rough estimate of the uncertainty of Y_DIFF_STDDEV, derived by dividing Y_DIFF_STDDEV by the square root of the number of values in the bin.

• Y_AVE_ERR: this is the simple mean of values of the input source list column Y_ERR which fall within the histogram bin.