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\label{fig:inclass_lab}  Figure supporting an in-class exercise on understanding image values and signal-to-noise, carried out during the lab period.  \begin{quote}  Consider the attached image of a nova observed with the millimeter telescope CARMA at 96 GHz (Panel A). Histograms of pixel values are shown in Panels B and C (Panel C is just a zoom-in of a region on Panel B); these are just like the histograms you made in DS9's \texttt{Scale Parameters}. The pixel values after calibration are expressed as flux density per pixel (units of mJy/pixel). The plotted range ($-2$ to $36\,\mathrm{mJy/pixel}$) includes all pixels in the image.  \begin{enumerate}  \item Estimate the average background value ($\bar{S}$) and explain your reasoning.  \item Estimate the standard deviation of the background ($\sigma$), and explain your reasoning.  \item Estimate the peak flux density of the nova ($S_{\mathrm{max}}$), and explain your reasoning.  \item Astronomers usually only take detections seriously if they are 5 or more $\sigma$ significant---that is, if the detected source is at least five times brighter than the   standard deviation of the background. In other words, the source's peak flux should be $S_{\mathrm{max}} > (\bar{S} + 5 \sigma)$. Estimate how many sigma the peak flux density of the nova is, and show your reasoning. Would this detection be taken seriously by other astronomers?  \end{enumerate}  \end{quote}