% Documentation for The 6C Survey of Radio Sources - I.  Declination
% Zone Dec>+80deg. (Baldwin, Boysen, Hales, Jennings, Wagget,
% Warner and Wilson 1985)
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% Document Number:
% Written: July 93  by N. A. Oliversen
% TeX Ver: July 93  by N. A. Oliversen
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\documentstyle [adc,11pt]{article}
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\newcommand{\cat}{The 6C Survey of Radio Sources - I.  Declination
  Zone $Dec>80$\degree}
\newcommand{\abbr}{6CSRSI}
\newcommand{\prefp}{Baldwin, Boysen, Hales, Jennings, Waggett, Warner
  and Wilson (1985)}
\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 93-23}
\maketitle
\date{}

\begin{abstract}
This catalogue contains the first section of the 6C Cambridge
survey of radio sources at 151 MHz.  This part of the
survey covers the region north of a declination of 80\degree.
This survey has an angular resolution of
4$\mindot$2 x 4$\mindot$2 x cosec(dec) (half-power at map center)
and a limiting flux density of 120mJy at 151 MHz.  Data include the
source positions (B1950), peak flux density, integrated flux density,
and contour map number. This part of the survey contains 1761 sources.

\end{abstract}

\section{Introduction}

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

\subsection {Description}

``\cat'' (6CSRSI) 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 first in a series of papers giving radio
source observations at 151 MHz.  See the discussion in \abbr\ for
details on the design and operation of the telescope and the
generation of the survey.  The other papers in this series include,
Hales et al. (1988), Hales et al. (1990) and Hales et al. (1991).

This portion of the catalogue contains a listing of 1761 radio
sources ordered by increasing right ascension.  The survey covers
a circular area of radius 10\degree\ centered on the North
Celestial Pole. This survey has been divided into 32 separate
maps.

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$10\%.  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\
for details on source selection criterion, calibration, and error
analysis.

Source positions have been systematically adjusted with respect to a
frame defined by standard positions of the 3C sources in the field.
Positional uncertainties have been estimated to correspond to
approximately 4 arcsec/S, where S is the apparent peak flux density
(in Jy) before primary beam correction.  See \abbr\ for further 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 Baldwin, J.E., Boysen, R.C., Hales, S.E.G., Jennings, J.E.,
Waggett, P.C., Warner, P.J. 1985, MNRAS, 217, 717.

\end {references}

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

``\cat'' consists of a single fixed-block file of 1761 36-byte
records.  The original file contained 40-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    & m       & I2    & Right ascension (B1950) \\
 7- 8    & s       & I2    & Right ascension (B1950) \\
10-12    & \degree\  & I3    & Declination (B1950) \\
14-15    & $'$     & I2    & Declination (B1950) \\
17-18    & $''$    & I2    & Declination  (B1950) \\
21-25    & Jy      & F5.2  & Flux density (peak)  \\
27-31    & Jy      & F5.2  & Flux density (integ.) \\
35-36    &         & I2    & Contour map panel \\
\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 300 mJy per beam
area (before primary beam correction). The integration was
carried out to a limiting level of 10\% of the fitted peak (or 50
mJy for sources having fitted peak values $<$500 mJy.  The
sums were then normalized by comparison with the same procedure
applied to an ideal point source of 1 Jy.  Note that for
unresolved sources the integrated flux value can fall below the
peak value.  If the column is blank the peak flux was not strong
enough to calculate the integrated flux.

{\bf Contour map panel:} This column contains the number of the
map panel in which the source appears.  There are 32 panels in
this survey.

\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.

\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. et al. 1990, MNRAS, 246, 256}
\item {Hales, S.E.G. et al. 1991, MNRAS, 251, 46}
\item {Roger, R.S., Bridle, A.H. and Costain, C.H. 1973, AJ, 78,
1030}

\end{references}
\end{document}