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\begin {document}

\section {The Sample}
\label{sec:sample}

The targets for this survey were selected from five fields of low foreground Galactic cirrus levels that were mapped by deep {\it Spitzer} imaging programs.  Four of the fields were surveyed by {\it Spitzer} as part of the $\sim$50~square degree SWIRE program (Lonsdale et al. 2003); only the four northern SWIRE fields were considered to enable follow-up from ground-based telescopes in the northern hemisphere.  The fifth field studied here was surveyed as part of the $\sim$5~square degree extragalactic component of the {\it Spitzer} First Look Survey (Fadda et al. 2006).  Table~\ref{tab:fields} provides a summary of the target fields.  The SWIRE and First Look Surveys have 24\micron\ sensitivities of 0.2--0.3~mJy (5$\sigma$), and so each detection in this sample of 5--100~mJy 24\micron\ sources is quite robust.
%SWIRE: 230uJy (5 sigma); 90% complete @ 280uJy
%FLS  : 210uJy (3?sigma); 50% complete @ 300uJy

%A total of 330 sources were ultimately chosen for follow-up {\it Spitzer} spectroscopy.  The 330 sources in this `Final Sample' were randomly chosen from 800 sources in what we refer to as the `Parent Sample'.  The Parent Sample was constructed after excising the entire catalog of 5--100~mJy 24\micron\ sources for stars, extended targets, targets with nearby companions or pre-existing {\it Spitzer} spectroscopy, and targets lacking IRAC data.  A breakdown of the number of targets in each field is provided in Table~\ref{tab:fields}.  To ensure that the Final Sample properly reflected the characteristics of the larger Parent Sample, the random selection was 

There are a total of 1737 sources in these fields with a 24\micron\ flux density between 5 and 100~mJy.  A breakdown of the number of targets in each field is provided in Table~\ref{tab:fields} ({\it maybe we don't want to include the column titled `Total Sample'}).  After excluding stars, extended targets (to maximize the flux that falls within the spectrograph's slit), targets with nearby companions or pre-existing {\it Spitzer} spectroscopy, and targets lacking IRAC data, the `Parent Sample' consists of 800 potential sources.  From the Parent Sample a total of 330 sources were randomly chosen for follow-up {\it Spitzer} spectroscopy.  To ensure that the Final Sample properly reflected the characteristics of the larger Parent Sample, the selection was forced to yield the same fraction of targets in 24\micron\ flux density bins of 5--7, 7--10, 10--15, 15--25, and 25--100~mJy (see Figure~\ref{fig:counts}).  Figure~\ref{fig:colors} shows that the Final and Parent Samples show similar distributions of mid-infrared colors as a function of 24\micron\ brightness.

{\it Do we want to say anything on this?}  In addition to ensuring that the selection was carried out appropriately in terms of colors and the proportion of objects appearing at different brightnesses, we can check whether the exlusion of extended targets significantly biased our sample.  Figure~XXX and Table~YYY ... The sizes of the sources in the Final Sample statistically differ very little from those in the Parent Sample.

%0=800 ok
%1= 47 IRS archival exists
%2=269 too extended
%3=117 companion
%4= 62 24um morphology uncertain
%5=275 star
%6=167 need IRAC cutouts
%=====
% 1737 total
 
\begin {thebibliography}{dum}
\bibitem{Lon03} Lonsdale, C. et al. 2003, \pasp, 225, 897
\bibitem{Fad06} Fadda, D. et al. 2006, \aj, 131, 2859
\end {thebibliography}

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%TABLES
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
\begin{deluxetable}{lcccccc}
\def\a{\tablenotemark{a}}
\def\b{\tablenotemark{b}}
\def\c{\tablenotemark{c}}
\def\p{$\pm$}
\tabletypesize{\scriptsize}
\tablenum{1}
\label{tab:fields}
%\tablecaption{Fields for Selecting 24\micron\ Targets}
\tablecaption{Target Fields}
\tablewidth{0pc}
\tablehead{
\colhead{Field} &
\colhead{$\alpha_0~~~\delta_0$} &
\colhead{Cirrus} &
\colhead{24\micron} &
\colhead{Total\a} &
\colhead{Parent\b} &
\colhead{Final\c} 
\\
\colhead{} &
\colhead{(J2000.0)} &
\colhead{$I(100\micron)$} &
\colhead{Map Size} &
\colhead{Sample} &
\colhead{Sample} &
\colhead{Sample} 
\\
\colhead{} &
\colhead{} &
\colhead{(MJy/sr)} &
\colhead{($\sq\degr$)} &
\colhead{} &
\colhead{} &
\colhead{} 
}
\startdata
%ELAIS S1 &003830$-$440000&0.42 &~6.8&188&~92&~0\\
XMM-LSS	 &022120$-$043000&1.3~~&~9.1&314&159&75\\
%Chandra S&033200$-$281600&0.46 &~7.8&215&111&~0\\
Lockman	 &104500$+$580000&0.38 &11.1&288&133&79\\
ELAIS N1 &161100$+$550000&0.44 &~9.3&365&173&96\\
ELAIS N2 &163648$+$410145&0.42 &~4.2&183&~73&41\\
FLS Exgal&171800$+$593000&1.2~~&~5.0&184&~59&39\\
\enddata
%\tablecomments{\footnotesize Placeholder.}
\tablenotetext{a}{\footnotesize The total number of 24\micron\ sources in each field with flux densities between 5 and 100~mJy.}
\tablenotetext{b}{\footnotesize The number of 5--100~mJy 24\micron\ sources after excluding stars, extended targets, targets with nearby compansions or existing {\it Spitzer} spectroscopy, and targets lacking IRAC data.}
\tablenotetext{c}{\footnotesize The number of 24\micron\ sources randomly chosen from the Parent Sample for follow-up {\it Spitzer} spectroscopy.}
\end{deluxetable}

%FIGURES
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
\begin{figure}
 \plotone{counts.eps}
 \caption{A comparison of how the Final and Parent Samples populate different bins of 24\micron\ flux density.}
 \label{fig:counts}
\end{figure}

\begin{figure}
 \plotone{colors.eps}
 \caption{A comparison of mid-infrared colors in the Final and Parent Samples.}
 \label{fig:colors}
\end{figure}
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
\end{document}
%Targets will be selected from all fields surveyed to adequate depth by Spitzer, most prominently the six SWIRE fields covering a total of 50 sq. deg., the FLS field with 5 sq. deg., the Bootes field with 9 sq. deg, and other smaller fields if needed.  At a density of 12 galaxies/sq. deg., these fields arelready provide well over 800 extragalactic sources in the range 5 to 100 mJy.

%The choice to target 458 objects rests on statistical considerations of bin sizes and of new object discovery probabilities.  1. Large numbers are needed to support any attempt to sort the SEDs into bins and estimate dispersion or average within bins.  Figure 1 suggests about twenty bins are needed to sort the spectra into distinct types, so even with 500 objects, each bin will contain 25 SEDs on average, and fewer in many cases.  2. In order to determine the frequency of a $\sim$5\% classes with $\pm$2\% accuracy against Poisson noise, we need a total of 500 spectra.  AGN for instance are expected to occur at $<$30\% frequency, and will certainly display several SED types (Figure 1).  3. Large numbes are also required to ensure detection of rare classes.  We need 458 SEDs in order to achieve a 99\% likelihood of detecting a class with a 1\% true incidence; even failure to detect new classes would be a significant statement in this case.  An interesting example of a 1\% class discovered from the IRAS Bright Galaxy Sample follow-up is the ``nascent starburst'' phenomenon (Roussle+ 2006); it was first identified as rare (2 out of 312) radio deficient objects (compared to the standard radio-IR ratio), and later shown to be long-quiescent galaxies thrust into a new starburst epidos $<$ Myr ago.  We have therefore settled on a sample of 458 objects.
