RRS8C38MHZ - 8C Revised Rees Survey 38-MHz Source Catalog
Users of these data should consult and cite the original survey paper by Rees as primary reference (1990MNRAS.244..233R) with the present publication (1995MNRAS.274..447H) as a supplementary revision. The recommended style of reference is thus: "The revised Rees 38-MHz survey (Rees 1990, catalogue revised Hales et. al 1995)."
In the Hales et al. (1995) paper, the authors aimed to improve the accuracy of the source positions to <~ 1 arcminute, so that a search radius smaller than the survey resolution of 4.5 arcminutes was practicable everywhere.
Note that for interest the source list includes data on some sources at declinations lower than +60 degrees, but that the right ascension coverage is not complete below +60 degrees.
A revised machine-readable source list for the Rees 38-MHz survey. Hales S.E.G., Waldram E.M., Rees N., Warner P.J. <Mon. Not. R. Astron. Soc. 274, 447 (1995)> =1995MNRAS.274..447H A deep 38-MHz radio survey of the area declination > +60 degrees. Rees N. <Mon. Not. R. Astron. Soc. 244, 233 (1990)> =1990MNRAS.244..233R
The position-based source designation recommended by the CDS Dictionary of Nomenclature of Celestial Objects, viz., '8C HHMM+DDdA', where the numerical part of the name is the truncated B1950.0 position of the radio source (to 1 minute of time in RA and 0.1 degrees in Dec). Where there are two apparently independent sources which would otherwise have the same abbreviated source name, the authors added an a 'A' or 'B' to the name. The HEASARC created these names from the positions, as they were not present in the original table.
The Right Ascension of the 38-MHz radio source in the selected equinox. This was given in B1950.0 equatorial coordinates in the original table to a precision of 1 second of time. A comparison of these positions with those in the Taxas and 6C catalogs showed that, although small systematic effectes undoubtedly remained, the target accuracy of 1 arcminute was comfortably achieved. For example, of those sources which had 1 Jy (0.5 Jy) counterparts in the Texas survey, 68% were within ~ 20 (~ 30) arcseconds of their Texas positions.
The Declination of the 38-MHz radio source in the selected equinox. This was given in B1950.0 equatorial coordinates in the original table to a precision of 1 arcsecond. A comparison of these positions with those in the Taxas and 6C catalogs showed that, although small systematic effectes undoubtedly remained, the target accuracy of 1 arcminute was comfortably achieved. For example, of those sources which had 1 Jy (0.5 Jy) counterparts in the Texas survey, 68% were within ~ 20 (~ 30) arcseconds of their Texas positions.
The Galactic Longitude of the 38-MHz radio source.
The Galactic Latitude of the 38-MHz radio source.
This flag parameter characterizes the source morphology as follows:
P = Simple source with only one local maximum within the source region (defined by the contour which encircles the local maximum and is 2.5 times the local noise level). The position is that of the peak flux brightness. C = Component or source associated with a single local maximum within an integrated complex. The peak and integrated flux for each such component represent values for that component only, and the position is that of the peak brightness. The components of a complex are not necessarily immediately adjacent to each other in the revised list, when it is ordered in right ascension.
The peak brightness of the 38-MHz radio source or component, in mJy/beam. (These values were converted by the HEASARC from the Jy/beam units used in the original table). The beam is not of constant size, the resolution being 4.5 x 4.5 cosec(Dec) arcmin2. The point of quoting the peak brightness in mJy/beam is that, for a source which is not significantly resolved or distorted by ionospheric effects, the peak brightness in those units will give a reasonable estimate of the flux density of the source (and be numerically comparable to the integrated flux density in mJy). The provided source extent parameter also ties in with this idea by comparing the integration area of a source to the area of a synthesised beam.
The original paper by Rees contains much discussion about the relative merits of peak brightness and integrated flux density as estimates of a source flux density, including consideration of the behaviour of this ratio; all this hinges on the idea of flux being smeared out with respect to the theoretical synthesised beam, so that the concept of a beam area is crucial to the discussion.
The integrated flux density of the 38-MHz radio source or component, in mJy. (These values were converted by the HEASARC from the Jy units used in the original table).
This parameter is an indicator of the extent of the source and is the ratio of the integration area of the source to the area of a synthesised beam, calculated using the same integration level. Thus, size = 1 indicates a point source, size < 1 indicates some over-resolution due to noise effects, and size > 1 an apparently extended source. Most sources appear slightly extended because of distortions created by the ionosphere. Remember that the survey is confusion limited!
The signal-to-noise, i.e., the ratio of the peak brightness to the local noise level calculated at the position of the source. The revised list contains only sources or components with signal-to-noise >= 5.0. It excludes the components with signal-to-noise < 5.0 listed in Rees (1990) for some complexes.
The number of the contour plot on which the source appears in the atlas provided in Rees (1990), provided so as to enable the user to check the appearance and environment of the source