% Documentation for The 6C Survey of Radio Sources - III.  The 
% Zone 48d<Dec<+68d, 05h25m<RA<18h17m. (Hales, Masson, Warner and 
% Baldwin 1990)
%
% Document Number:
% Written: July 1993  by N. A. Oliversen
% TeX Ver: July 1993 by N. A. Oliversen
%
\documentstyle [adc,11pt]{article}
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\newcommand{\cat}{The 6C Survey of Radio Sources - III.  The Zone
  48\degree$<Dec<$68\degree, $05^{h}25^{m} < RA < 18^{h}17^{m}$}
\newcommand{\abbr}{6CSRSIII}
\newcommand{\prefp}{Hales, Masson, Warner and Baldwin (1990)}
\newcommand{\docnum}{ADC }
%
\begin{document}
%
\title{\cat}
\author{\prefp}
\docauthor{N. A. Oliversen}
\date{July 1993 \\ (Revised March 1994)}
\docno{NSSDC/WDC-A-R\&S 93-25}
\maketitle
\date{}

\begin{abstract}
This catalogue contains the third section of the 6C Cambridge survey
of radio sources at 151 MHz.  This part of the survey covers the
region from 48\degree\ to 68\degree\ in declination and between
$5^{h}25^{m}$ and $18^{h}17^{m}$ in right ascension. This survey has an
angular resolution of 4$\mindot$2 x 4$\mindot$2 x cosec(dec)
(half-power at map center).  The limiting flux density varies between
160 mJy to 600 mJy as a function of map and declination. Data include
the source positions (B1950), peak flux density, integrated flux
density, contour map panel number and contour map field names. This
part of the survey contains 8749 sources, covering an area of 1950
square degrees. This catalogue slightly overlaps the Hales et al.
(1988) survey. 

\end{abstract}

\section{Introduction}

{\bf A copy of this document should be distributed with every 
copy of the machine-readable catalog.}

\subsection {Description}

``\cat'' (\abbr) contains a compilation of radio source
observations made with the use of an (non-tracking) Earth-rotation
aperture synthesis telescope comprising many small aerial arrays on an
east-west baseline operating at 151 MHz.  This paper is the third in a
series of papers giving radio source observations at 151 MHz.  See the
discussion in Baldwin et al. (1985) for details on the design and
operation of the telescope and the generation of the survey. 
Other papers in this series include Hales et al. (1988) and
Hales et al. (1991).

This portion of the catalogue contains a listing of 8749 radio
sources ordered by increasing right ascension.  The survey is
centered on a declination of 58\degree\ to facilitate calibration
using Cassiopea A.  This survey has been divided into six  separate
fields with up to 32 panels per field.  

Flux densities are on the scale of Roger, Bridle, and Costain
(1973) (RBC).  The authors believe the flux density scale is
consistent with the RBC scale to within $\pm$5\%.  Both the peak 
flux density and the integrated flux densities required a 
primary-beam correction, and the peak flux densities required a 
further correction for the reduction in peak brightness caused by
chromatic aberration.  The latter correction is dependent on the 
distance of the source from the field center.  See \abbr\ and
Hales et al. (1988) for details on source selection criterion, 
calibration, and error analysis. 

Source positions have been adjusted by 1.1s to 2.3s in right ascension
and up to -40$''$ in declination, to agree with known positions 
of bright sources.  The authors believe that the residual 
systematic errors are less than $\pm$5$''$ in each coordinate.

Note that this file only contains the catalogue of radio sources.
It is intended to be used with the radio maps 
originally published on microfiche in \prefp.  The source lists and
FITS format maps for the four regions of the 6C survey published
todate have been placed on a CDROM entitled ``Images from the
Radio Universe'', which is available from the address below.  A
nominal fee may be charged for such requests.  

\samepage{
\hspace*{1.5in}Prof. Jim Condon \\
\hspace*{1.5in}NRAO \\
\hspace*{1.5in}Edgemont Road \\
\hspace*{1.5in}Charlottesville, Virginia  22903-2475 \\ }

\subsection{Reference}
\begin{references}
\item Hales, S.E.G., Masson, C.R., Warner, P. J. and Baldwin, 
J.E. 1990, MNRAS, 246, 256.

\end {references}

\section {Structure}
\subsection{The File as a Whole}

``\cat'' consists of a single fixed-block file of 8749 48-byte 
records.  The original file contained 51-byte records. Detailed
descriptions of some of the fields in the file are given in the
following sections. 

\subsection{Catalog File}

\begin{table}[h]
\centering
\begin{tabular}{ c c c l }
\hline\hline
         &         &Suggested &                \\
Bytes    & Units   &  Format  & \multicolumn{1}{c}{Item}     \\
\hline
 1- 2    & h       & I2    & Right ascension (B1950)  \\
 4- 5    & min     & I2    & Right ascension (B1950) \\
 7-10    & s       & F4.1  & Right ascension (B1950) \\
12-14    & \degree\  & I3    & Declination (B1950) \\
16-17    & $'$     & I2    & Declination (B1950) \\
19-20    & $''$    & I2    & Declination  (B1950) \\
23-27    & Jy      & F5.2  & Flux density (peak)  \\ 
30-34    & Jy      & F5.2  & Flux density (integ.) \\
35       &         & A1    & Integrated flux flag  \\
37-39    &         & I3    & Contour map panel number\\
   40    &         & A1    & The character ``:'' \\
41-47    &         & A7     & Contour map field name \\
\hline\hline
\end{tabular}
\caption{Catalog Record Format}
\label{t:catfig}
\end{table}

\pagebreak

{\bf Flux density (peak):} Source peak flux density at 151 MHz.

{\bf Flux density (integrated):} Source integrated flux density
at 151 MHz.  Integrated flux densities were carried out for
sources with fitted peak flux densities above 456 mJy per beam
area (before primary beam correction). The integration was
carried out to a limiting level of 10\% of the fitted peak (or 98
mJy for sources having fitted peak values $<$0.98 Jy). Note that
for unresolved sources the integrated flux value can fall below
the peak value.  

{\bf Integrated flux flag:}  If the column is marked with a dash (-), the
peak flux was not strong enough to calculate the integrated flux.
If the column is marked with an asterisk (*), the peak flux
was strong enough to qualify for integration, but it has been
integrated into a brighter adjoining peak. 

{\bf Contour map panel number:} This column contains the name of the
map panel in which the source appears.  There are up to 32 panels 
per map field in this survey.  The panel number and map field name
tell the user where to look up the source of interest in the published
contour map.  A panel number listed with a negative sign indicates 
that the data are accommodated at the location but come from another 
map or area of sky.

{\bf Contour map field name:} This column contains the name of the 
field in which the source appears.  Six fields have been included in 
this survey: 0700+58, 0900+58, 1100+58, 1300+58, 1500+58, and 1700+58.
The panel number and map field name tell the user where to look up
the source of interest in the published contour map.

\section{History}

\subsection{Remarks and Modification}

``\cat'' was received by the Astronomical Data Center (ADC), NASA
Goddard Space Flight Center, from Dr. Heinz Andernach.
The catalog was originally submitted by the first author, Dr. Sally 
Hales.

The integrated flux flag column was added by the ADC/CDS by extracting
the character information from the Integrated flux density column. 
This was done to avoid mixing character and numeric information in
the same column.

\section{Reference to the Documentation}
\begin{references}
\item {Baldwin, J.E., Boysen, R.C., Hales, S.E.G., Jennings, J.E.,
Waggett, P.C., Warner, P.J. and Wilson, D.M.A.  1985, MNRAS, 217, 
717}
\item {Hales, S.E.G., Baldwin, J.E. and Warner, P.J. 1988, MNRAS, 
234, 919 }
\item {Hales, S.E.G., Masson, C.R., Warner, P.J. and Baldwin, J.E.
  1990, MNRAS, 246, 256}
\item {Hales, S.E.G., Mayer, C.J., Warner, P.J. and Baldwin, J.E.
  1991, MNRAS, 251, 46}
\item {Roger, R.S., Bridle, A.H. and Costain, C.H. 1973, AJ, 78, 
1030}

\end{references}
\end{document}
