% Documentation for The 6C Survey of Radio Sources - IV.  The Zone
%   67d<Dec<82d, 0h<RA<24h (Hales, Mayer, Warner and Baldwin 1988)
%
% Document Number:
% Written: April 12, 1993  by N. A. Oliversen
% TeX Ver: April 12, 1993  by N. A. Oliversen
%
\documentstyle [adc,11pt]{article}
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\newcommand{\cat}{The 6C Survey of Radio Sources - IV.  The Zone
 67\degree $<Dec<$ 82\degree, $0^{h} < RA < 24^{h}$}
\newcommand{\abbr}{6CSRSIV}
\newcommand{\prefp}{Hales, Mayer, Warner and Baldwin (1991)}
\newcommand{\docnum}{ADC }
%
\begin{document}
%
\title{\cat}
\author{\prefp}
\docauthor{N. A. Oliversen}
\date{July 1993}
\docno{NSSDC/WDC-A-R\&S 93-26}
\maketitle
\date{}

\begin{abstract}
This catalogue contains the fourth section of the 6C Cambridge
survey of radio sources at 151 MHz, covering the region from
67\degree\ to 82\degree\ in declination and between $0^{h}$ and
$24^{h}$ 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. 
The limiting flux density is 160 mJy at 151 MHz in the present
zone with completeness achieved at 400 mJy on the best maps and
at about 800 mJy on the worst. This part of the survey contains
5421 sources, covering an area of 1440 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
oservations 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 fourth 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).  Other papers in the
series include Hales et al. (1988) and Hales et al. (1990).
The present zone overlaps that covered in Baldwin et al. (1985)
over the range 80\degree $<Dec<$ 82\degree\ and also that covered in
Hales et al. (1990) over the range 67\degree $<Dec<$ 68\degree\ and
$5^{h}25^{m} < RA < 18^{h}17^{m}$.

The catalogue contains a listing of 5421 radio sources ordered by
increasing right ascension from $0^{h}$ to $24^{h}$. The survey
is centered on a declination of 75\degree\ and includes from
declination 67\degree\ to 82\degree.  Eight fields have been
included in this survey: 0100+75, 0400+75, 0700+75, 1000+75,
1300+75, 1600+75, 1900+75, and 2200+75. 

Attenuation corrections were applied to all flux densities and maps using
tables derived for each synthesis (see Hales et al. 1988).  
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\ and
Baldwin et al. (1985) for details on source selection criterion
and error analysis. 

Source positions have been adjusted (by 2.8s to 5.5s in right
ascension and by up to 11$''$ 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$3-5$''$ 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
to 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., Mayer, C.J., Warner, P.J. and Balwin J.E. 1991, 
MNRAS, 251, 46.

\end {references}

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

``\cat'' consists of a single fixed-block file of 5421 50-byte 
records.  The original file was variable format with 49-bytes per
record.  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.) \\
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 513 mJy. The
integration was carried out to a limiting level of 10\% of the
fitted peak (or for 110 mJy for sources having apparent flux
densities \(< 1.10 \) Jy).  For the right-half of the field 
1900+75, the threshold to qualify for integration was raised to
1.54 Jy and for the apex of the field 2200+75, to 0.96 Jy, with 
limiting level for both cases of 10\% (or 154 mJy for sources
having apparent peak flux densities $< 1.54$ Jy).  Note that for
unresolved sources the integrated flux value can fall below the
peak value.  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.  The number of contour panels per map field varies from
27 to 32.  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.  Eight fields have been
included in this survey: 0100+75, 0400+75, 0700+75, 1000+75,
1300+75, 1600+75, 1900+75, and 2200+75.  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 of
Instituto de Astrofisica de Canarias, IAC, Tenerife, Spain. 

\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}