The procedures described in the previous section yielded a preliminary list
of sources (or source components) for further investigation. In order to
minimize the incompleteness effects
present at fluxes approaching the source extraction threshold
(see Fig. 1) we decided to insert in the
final catalogue only the sources with
,
where
is the mosaic rms flux density.
This threshold has been chosen after inspection of the local noise
distribution. The local noise (
)
has been defined
as the average noise value in a box of about
size
around a source.
Usually the local noise does not show significant systematic
departures from the mosaic average rms value: the
distribution can be
described fairly well by a Gaussian with
FWHM = 0.14 and peak value
equal to 1.01 (see Fig. 2).
This can be seen also in Fig. 3, where we show, for each source,
the signal-to-noise
ratio defined using both
and
.
The two signal-to-noise ratios
mostly agree with each other, although
a number of significant departures are evident for the
faintest sources.
This is due to the presence of some residual areas
where the noise is not random due to
systematic effects (noise peaks and stripes). This is caused by the
limited dynamical range in presence of very strong sources
(stronger than 50-100 mJy, see also Paper I).
It is worth noting that also the systematic departures from the expected
behavior at the brightest end of the plot (
)
are a consequence of the same problem.
In mosaic regions where local noise is significantly larger,
we applied a
cut-off if
(assuming a normal distribution for
the noise, the probability to get a local to average noise value
is
).
This resulted in the rejection of 32 sources (see the region in
Fig. 3 defined by
,
and
).
The criteria discussed above proved to be very effective in selecting out noise artifacts from the catalogue. Nevertheless a few (6) sources, which satisfy both the average and the local noise constraints are, however, evident noise artifacts at visual inspection. Such objects have been rejected from the final catalogue.
The adopted criteria for the final catalogue definition also
allowed us to significantly reduce the number of poor
Gaussian fits (see Sect. 2.3) since a large fraction of them
()
have fainter
:
we are left with
50 poor Gaussian fits (flagged "S*'', see Sect. 3.4)
in the final catalogue.
A total number of 3172 source components entered the final catalogue. Some of them have to be considered different components of a unique source and, as discussed later in Sect. 3.2, the number of distinct sources in the ATESP catalogue is 2960.
The ratio of the integrated flux to the peak flux is a direct measure of the
extension of a radio source:
![]() |
(1) |
In Fig. 4 we have plotted the flux
ratio as a function of the signal-to-noise for all the sources
(or source components) in the ATESP catalogue.
The flux density ratio has a skew distribution, with a tail towards high flux
ratios due to extended sources. Values for
are due to the influence of the image noise
on the measure of source sizes (see Sect. 4).
To establish a criterion
for extension, such errors have to be taken into account.
We have determined the lower envelope of the flux ratio distribution (the curve
containing 90% of the
sources) and we have
mirrored it on the
side (upper envelope in
Fig. 4). We have considered as unresolved all
sources
laying below the upper envelope. The upper envelope can be characterized
by the equation:
![]() |
(2) |
It is worth noting that the envelope does not converge to 1 going to large
signal-to-noise values. This is due to the radial smearing effect. It
systematically reduces the source peak fluxes, yielding larger
ratios (see discussion in Sect. 4.2).
From
Fig. 4 we can quantify the smearing effect in
on average.
Deconvolved angular sizes are given in the catalogue only for sources above the upper curve (filled circles in Fig. 4). For unresolved sources (dots in Fig. 4) deconvolved angular sizes are set to zero. Note that no bandwidth correction to deconvolved sizes has been applied. Correcting for such effect would be somewhat complicated by the fact that each source in the radio mosaics is a sum of contributions from several single pointings.
In Fig. 5 the (nearest neighbor) pair
density distribution is shown as a function
of distance (histogram). Also indicated is the expected distribution if all
the sample sources
(components) were randomly distributed in the sky.
The expected distribution
has been scaled so as to have the same area below the curve and the observed
histogram. The excess at small
distances is clearly due to physical associations and, because of the
normalization chosen, is compensated by a
deficiency at larger distances (between
and
).
All the components closer than
(i.e. about three times the
beam size) have been considered as possibly belonging to a unique double
source. Triple sources are defined whenever one additional component is closer
than
to (at least) one of the pair components. For multiple
sources the same criterion is applied iteratively.
Applying this distance constraint we expect that
of the pairs
are random superpositions.
The flux ratio distribution between the pair components has a large spread at all distances (see Fig. 6). To reduce the contamination we have discarded all the pairs with flux ratio larger than a factor 10. For triples and multiple sources the probable core is not considered when computing the flux ratios.
A few departures from the adopted criteria are present in the catalogue.
For example the triple
source ATESP J005620-394145 and the double source ATESP J011029-393253 have
but do not satisfy the flux ratio constraint.
All exceptions are
based on source geometry considerations and/or the analysis of the source
field.
In order to increase the multiple sources' sub-sample completeness, we added
31 sources with distances
,
which show
clear signs of physical associations between their components (see
Fig. 7 for some examples). No flux
ratio constraints have been applied to such sources.
In Fig. 6
are shown the flux ratios for all the pairs in the final sample of
multiple sources (filled circles).
As a final result we have 189 multiple sources: 168 doubles, 19 triples and 2 sources with four components. As a consequence, the initial list of 3172 radio components results in a catalogue of 2960 distinct radio sources.
In the final catalogue we have 23 non-Gaussian sources
whose parameters have been defined as discussed in Sect. 2.3.
In particular we notice that
positions refer to peak positions,
which, for non-Gaussian sources does not
necessarily correspond to the position of the core. We also notice that we can
have non-Gaussian components in multiple sources. Some examples of single
and multiple non Gaussian sources are shown in Fig. 7.
The electronic version of the full radio catalog is available through the ATESP page at http://www.ira.bo.cnr.it. Its first page is shown as an example in Table 1. The source catalogue is sorted on right ascension. The format is the following:
Column (1) - Source IAU name. Different
components of multiple sources are labeled "A'', "B'', etc.
Columns (2) and (3) - Source position: Right Ascension and
Declination (J2000).
Columns (4) and (5) - Source peak (
)
and
integrated (
)
flux densities in mJy (Baars
et al. 1977 scale). The flux densities are not corrected
for the systematic effects discussed in Sect. 4.2.
Columns (6) and (7) - Intrinsic (deconvolved from the beam)
source angular size. Full width half maximum
of the major (
)
and minor (
)
axes in
arcsec.
Zero values
refer to unresolved sources (see Sect. 3.1 for more
details).
Column (8) - Source position angle (PA, measured N through E)
for the major axis
in degrees.
Column (9) - Flag indicating the fitting procedure and
parameterization adopted for the source or source component (see
Sects. 2.3 and 3.2).
"S'' refers to Gaussian
fits. "S*'' refers to poor Gaussian fits.
"E'' refers to non-Gaussian sources. "M'' refers to multiple
sources (see below).
IAU Name | RA | DEC |
![]() |
![]() |
![]() |
![]() |
PA | |
(J2000) | mJy | arcsec | degr. | |||||
ATESP J223235-402642 | 22:32:35.62 | -40:26:42.1 | 1.26 | 6.07 | 27.13 | 13.55 | 28.9 | S |
ATESP J223237-393113 | 22:32:37.71 | -39:31:13.2 | 0.69 | 0.71 | 0.00 | 0.00 | 0.0 | S |
ATESP J223238-394102 | 22:32:38.54 | -39:41:02.9 | 0.48 | 0.58 | 0.00 | 0.00 | 0.0 | S |
ATESP J223242-393054 | 22:32:42.10 | -39:30:54.3 | 2.33 | 2.46 | 0.00 | 0.00 | 0.0 | S |
ATESP J223248-401345 | 22:32:48.24 | -40:13:45.9 | 0.95 | 0.83 | 0.00 | 0.00 | 0.0 | S |
ATESP J223250-394059 | 22:32:50.79 | -39:40:59.7 | 0.57 | 0.93 | 10.47 | 0.00 | -88.4 | S |
ATESP J223252-401925 | 22:32:52.45 | -40:19:25.1 | 0.66 | 0.46 | 0.00 | 0.00 | 0.0 | S |
ATESP J223254-393652 | 22:32:54.54 | -39:36:52.0 | 1.03 | 1.70 | 9.89 | 5.39 | 48.3 | S |
ATESP J223255-395717 | 22:32:55.51 | -39:57:17.3 | 0.51 | 0.45 | 0.00 | 0.00 | 0.0 | S |
ATESP J223256-402010 | 22:32:56.10 | -40:20:10.3 | 1.13 | 1.08 | 0.00 | 0.00 | 0.0 | S |
ATESP J223301-393017 | 22:33:01.55 | -39:30:17.1 | 7.83 | 8.67 | 3.39 | 2.66 | -57.0 | S |
ATESP J223302-402817 | 22:33:02.31 | -40:28:17.5 | 0.66 | 0.71 | 0.00 | 0.00 | 0.0 | S |
ATESP J223303-401629 | 22:33:03.07 | -40:16:29.2 | 0.99 | 1.27 | 5.30 | 4.74 | 62.9 | S |
ATESP J223304-395639 | 22:33:04.92 | -39:56:39.0 | 1.85 | 2.94 | 23.51 | - | - | M |
ATESP J223304-395639A | 22:33:04.43 | -39:56:41.4 | 1.85 | 2.18 | 6.66 | 1.43 | -24.2 | S |
ATESP J223304-395639B | 22:33:06.31 | -39:56:32.2 | 0.80 | 0.76 | 0.00 | 0.00 | 0.0 | S |
ATESP J223313-400216 | 22:33:13.42 | -40:02:16.1 | 7.60 | 9.18 | 4.94 | 3.65 | -45.7 | S |
ATESP J223314-394942 | 22:33:14.42 | -39:49:42.8 | 1.28 | 1.33 | 0.00 | 0.00 | 0.0 | S |
ATESP J223316-393124 | 22:33:16.90 | -39:31:24.4 | 0.52 | 0.68 | 0.00 | 0.00 | 0.0 | S |
ATESP J223317-393235 | 22:33:17.19 | -39:32:35.0 | 2.40 | 3.37 | 9.29 | 4.22 | 9.4 | S |
ATESP J223320-394713 | 22:33:20.14 | -39:47:13.8 | 0.96 | 1.08 | 0.00 | 0.00 | 0.0 | S |
ATESP J223322-401710 | 22:33:22.93 | -40:17:10.7 | 4.92 | 6.26 | 7.56 | 3.34 | 14.7 | S |
ATESP J223327-395836 | 22:33:27.45 | -39:58:36.9 | 3.24 | 5.16 | 13.60 | 3.39 | -5.9 | S |
ATESP J223327-394541 | 22:33:27.73 | -39:45:41.7 | 2.74 | 5.70 | 21.21 | - | - | M |
ATESP J223327-394541A | 22:33:27.08 | -39:45:40.2 | 2.74 | 3.65 | 5.98 | 4.83 | 60.7 | S |
ATESP J223327-394541B | 22:33:28.89 | -39:45:44.4 | 1.29 | 2.05 | 10.04 | 0.00 | -73.8 | S |
ATESP J223329-402019 | 22:33:29.10 | -40:20:19.6 | 1.41 | 1.82 | 6.85 | 3.75 | -32.1 | S |
ATESP J223330-395233 | 22:33:30.97 | -39:52:33.4 | 0.50 | 0.53 | 0.00 | 0.00 | 0.0 | S |
ATESP J223335-401337 | 22:33:35.21 | -40:13:37.7 | 0.63 | 0.71 | 0.00 | 0.00 | 0.0 | S |
ATESP J223337-394253 | 22:33:37.01 | -39:42:53.8 | 2.58 | 2.79 | 0.00 | 0.00 | 0.0 | S |
ATESP J223338-392919 | 22:33:38.49 | -39:29:19.6 | 5.26 | 5.62 | 0.00 | 0.00 | 0.0 | S |
ATESP J223339-393131 | 22:33:39.86 | -39:31:31.0 | 1.37 | 1.32 | 0.00 | 0.00 | 0.0 | S |
ATESP J223343-393811 | 22:33:43.21 | -39:38:11.2 | 1.00 | 1.05 | 0.00 | 0.00 | 0.0 | S |
ATESP J223343-402307 | 22:33:43.93 | -40:23:07.4 | 0.90 | 1.10 | 0.00 | 0.00 | 0.0 | S |
ATESP J223345-402815 | 22:33:45.23 | -40:28:15.6 | 0.56 | 0.65 | 0.00 | 0.00 | 0.0 | S |
ATESP J223346-393322 | 22:33:46.35 | -39:33:22.9 | 1.26 | 1.23 | 0.00 | 0.00 | 0.0 | S |
ATESP J223351-394040 | 22:33:51.19 | -39:40:40.9 | 1.12 | 1.17 | 0.00 | 0.00 | 0.0 | S |
ATESP J223356-401949 | 22:33:56.57 | -40:19:49.7 | 1.71 | 2.28 | 36.37 | - | - | M |
ATESP J223356-401949A | 22:33:55.33 | -40:20:11.8 | 0.52 | 0.63 | 0.00 | 0.00 | 0.0 | S |
ATESP J223356-401949B | 22:33:57.05 | -40:19:41.2 | 1.71 | 1.65 | 0.00 | 0.00 | 0.0 | S |
ATESP J223358-400642 | 22:33:58.77 | -40:06:42.4 | 1.29 | 1.20 | 0.00 | 0.00 | 0.0 | S |
ATESP J223401-402310 | 22:34:01.25 | -40:23:10.8 | 0.58 | 1.18 | 10.98 | 9.14 | 32.8 | S |
ATESP J223401-393448 | 22:34:01.87 | -39:34:48.9 | 1.69 | 2.09 | 5.28 | 3.10 | -72.8 | S |
ATESP J223402-402357 | 22:34:02.36 | -40:23:57.7 | 0.59 | 0.57 | 0.00 | 0.00 | 0.0 | S |
ATESP J223402-400017 | 22:34:02.64 | -40:00:17.3 | 1.70 | 1.99 | 5.37 | 2.86 | -28.2 | S |
ATESP J223404-395831 | 22:34:04.00 | -39:58:31.5 | 6.16 | 7.45 | 5.53 | 3.43 | 29.7 | S |
ATESP J223404-393358 | 22:34:04.08 | -39:33:58.9 | 0.85 | 0.90 | 0.00 | 0.00 | 0.0 | S |
ATESP J223407-393721 | 22:34:07.34 | -39:37:21.9 | 3.14 | 6.41 | 25.71 | - | - | M |
ATESP J223407-393721A | 22:34:06.35 | -39:37:27.4 | 2.03 | 3.23 | 8.90 | 6.08 | 38.9 | S |
ATESP J223407-393721B | 22:34:08.36 | -39:37:16.3 | 3.14 | 3.19 | 0.00 | 0.00 | 0.0 | S |
ATESP J223409-394258 | 22:34:09.58 | -39:42:58.2 | 0.71 | 1.11 | 10.16 | 5.23 | -15.4 | S |
ATESP J223410-394427 | 22:34:10.82 | -39:44:27.6 | 1.54 | 1.59 | 0.00 | 0.00 | 0.0 | S |
ATESP J223412-400254 | 22:34:12.80 | -40:02:54.6 | 0.66 | 0.69 | 0.00 | 0.00 | 0.0 | S |
ATESP J223413-393242 | 22:34:13.28 | -39:32:42.4 | 1.58 | 1.88 | 6.21 | 0.00 | 59.9 | S |
ATESP J223413-393650 | 22:34:13.74 | -39:36:50.2 | 0.48 | 1.71 | 25.27 | 8.28 | 38.4 | S |
ATESP J223413-395651 | 22:34:13.80 | -39:56:51.7 | 0.52 | 0.56 | 0.00 | 0.00 | 0.0 | S |
ATESP J223420-393150 | 22:34:20.47 | -39:31:50.5 | 0.55 | 0.73 | 0.00 | 0.00 | 0.0 | S |
The parameters listed for non-Gaussian sources are defined as discussed in Sect. 2.3.
For multiple sources we list all the components (labeled "A'', "B'', etc.) preceded by a line (flagged "M'') giving the position of the radio centroid, total flux density and overall angular size of the source. Source positions have been defined as the flux-weighted average position of all the components (source centroid). For sources with more than two components the centroid position has been replaced with the core position whenever the core is clearly recognizable.
Integrated total source flux densities are computed by summing all the component integrated fluxes.
The total source angular size is defined as las (see Sect. 2.3) and it is computed as the maximum distance between the source components.
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