% Documentation for The 6C Survey of Radio Sources - II.  The Zone
%   30d<Dec<51d, 08h30m<RA<17h30m (Hales, Baldwin, and Warner 1988)
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% Document Number:
% Written: July 1993  by N. A. Oliversen
% TeX Ver: July 1993  by N. A. Oliversen
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\documentstyle [adc,11pt]{article}
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\newcommand{\cat}{The 6C Survey of Radio Sources - II.  The Zone
 30\degree$<Dec<$51\degree, $08^{h}30^{m} < RA < 17^{h}30^{m}$}
\newcommand{\abbr}{6CSRSII}
\newcommand{\prefp}{Hales, Baldwin and Warner (1988)}
\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 93-24}
\maketitle
\date{}

\begin{abstract}
This catalogue contains the second section of the 6C Cambridge survey of
radio sources at 151 MHz, covering the region from 30\degree\ to
51\degree\ in declination and between $8^{h}30^{m}$ and
$17^{h}30^{m}$ in right ascension.  The survey has an angular
resolution of 4$\mindot$2 x 4$\mindot$2 x cosec(dec).  
Data include the source positions (B1950), peak flux density, integrated 
flux density, contour map panel number and contour map field names. 
Its limiting flux density depends weakly on right ascension and
strongly on declination and is 190 mJy in the central part of
the declination strip but rises to over 400 mJy near its
northern and southern boundaries.  This part of the survey
contains 8278 sources, covering an area of 2030 square degrees. 

\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 second in a series:  Details on the design and
operation of the telescope and the reduction of the survey were
first discussed in Baldwin et al. (1985).  The third paper
in this series was published in Hales et al. (1990) and the
fourth paper in the series was published in Hales et al. (1991). 

The catalogue contains a listing of 8278 radio sources ordered by
increasing right ascension from $8^{h}30^{m}$ to $17^{h}30^{m}$.
The survey is centered on a declination of 41\degree\ and
includes from declination 30\degree\ to 50\degree.  Five fields
have been included in this survey: 0940+41, 1120+41, 1300+41,
1440+41, and 1620+41. 

Attenuation corrections were applied to all flux densities and maps using
tables derived for each synthesis.  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\%.  See \abbr\ for details on source selection
criterion and error analysis.

Source positions have been systematically adjusted (by 0.6s in 
right ascension and by up to 10$''$ in declination) to agree with 
known positions of bright sources.  The residual rms scatter in
the corrected positions of the reference sources relative to their
true positions is estimated to be $\pm$4-5$''$ in each coordinate.
See \abbr\ for details.

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
t-date 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., Baldwin, J. E. and Warner, P. J. 1988, 
MNRAS, 234, 919.

\end {references}

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

``\cat'' consists of a single fixed-block file of 8278 50-byte 
records.  The original file contained 80-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  \\
38-39    &         & I2    & Contour map panel number  \\
   41    &         & A1    & The character ``:''\\
43-49    &         & 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 apparent flux densities above 483 mJy. The
integration was carried out to a limiting level of 10\% of the
fitted peak (or for 103 mJy for sources having apparent flux
densities \(< 1.03\) 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 panel
number of the contour map in which the source appears in the
survey.  Each map field is divided into 32 contour panels.  The
panel number and the map field name tell the user where to look
up the source of interest in the published contour map. 

{\bf Contour map field name:} This column contains the name of the
field in which the source appears.  There are five fields in this
survey: 0940+41, 1120+41, 1300+41, 1440+41, and 1620+41.  The panel
number and the 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. 1990, MNRAS, 246, 256}
\item {Hales, S.E.G. 1991, MNRAS, 251, 46}
\item {Roger, R.S., Bridle, A.H. and Costain, C.H. 1973, AJ, 78, 
1030}

\end{references}
\end{document}
