Abstract

The Simultaneous Medicina-Planck Experiment (SiMPlE) is aimed at observing a selected sample of 263 extragalactic and Galactic sources with the Medicina 32-m single-dish radio telescope in the same epoch as the Planck satellite observations.

The data, acquired with a frequency coverage down to 5 GHz and combined with Planck at frequencies above 30 GHz, will constitute a useful reference catalogue of bright sources over the whole Northern hemisphere. Furthermore, source observations performed in different epochs and comparisons with other catalogues will allow the investigation of source variabilities on different time-scales.

In this work, we describe the sample selection, the ongoing data acquisition campaign, the data reduction procedures, the developed tools and the comparison with other data sets.

We present 5 and 8.3 GHz data for the SiMPlE Northern sample, consisting of 79 sources with δ≥ 45° selected from our catalogue and observed during the first 6 months of the project. A first analysis of their spectral behaviour and long-term variability is also presented.

1 INTRODUCTION

Microwave band observations with satellites, mainly aimed at the study of the cosmic microwave background (CMB), also offer a unique opportunity to investigate the spectral properties of radio sources in a poorly explored frequency range, partially inaccessible from ground.

The study of the spectral energy distribution (SED) and variability of sources from radio to far-infrared (FIR) wavelengths is crucial to probe the physics of the innermost regions of active galactic nuclei (AGN), radio galaxies and some classes of variable Galactic radio sources (i.e. microquasars and binary active systems). These objects show remarkable outbursts. Studying their SED simultaneously from radio to FIR in several epochs helps in constraining the outburst mechanisms and the processes which activate their radio emission.

The project described in this paper aims at accumulating multifrequency radio observations of northern sources at 5, 8.3 and 22 GHz almost simultaneously to their observations performed – from 30 to 857 GHz – by the European Space Agency (ESA) Planck satellite (Tauber et al. 2010a). This will allow the construction of the SED of a significant sample of sources on a wide frequency range, exploiting almost coeval data. The simultaneity of the observations is crucial to evaluate the contribution from variability and spectral effects in affecting the physical interpretation of source observational properties.

Catalogues based on the Wilkinson Microwave Anisotropy Probe (WMAP) satellite maps have been produced using several source extraction techniques (Bennett et al. 2003a,b; López-Caniego et al. 2006; Hinshaw et al. 2007; Chen & Wright 2009; Gold et al. 2011). Their completeness limit (i.e. the flux density level above which all the sources in the observed area are listed in the catalogue) is typically ∼1 Jy at 23 GHz. Massardi et al. (2009) have combined blind and non-blind approaches (see López-Caniego et al. 2007; González-Nuevo et al. 2008), exploiting the Mexican hat wavelets 2 (MHW2) filter (González-Nuevo et al. 2006) to extract an all-sky catalogue of 516 sources with |b| > 5°. It is almost 91 per cent complete above 1 Jy and constitutes the New Extragalactic WMAP Point Sources (NEWPS) catalogue. Almost all (484) sources in the sample were previously catalogued as extragalactic (457) or Galactic (27) objects. The remaining 32 candidate sources do not have counterparts in lower frequency all-sky surveys with comparable flux densities and may therefore be just high peaks in the distribution of other components present in the maps. If they are all spurious, the reliability of the sample (i.e. the probability that a source listed in the sample is a genuine radio source) is 93.8 per cent.

To date, the Australia Telescope 20-GHz (AT20G; Massardi et al. 2011a; Murphy et al. 2010) survey provides the deepest complete ground-based sample of the high-frequency southern sky. It is a blind survey performed with the Australia Telescope Compact Array (ATCA) in the years 2004–2008. Its final catalogue consists of 5890 sources above a flux limit of 40 mJy and is an order of magnitude larger than any previous catalogue of high-frequency radio sources. No analogous sample, deeper than the NEWPS catalogue, has been observed at frequencies above 8.4 GHz in the Northern hemisphere.

The ESA Planck satellite (Tauber et al. 2010a) is providing a blind survey of the entire sky in nine frequency bands (30, 44, 70, 100, 143, 217, 353, 545 and 857 GHz), with full width at half-maximum (FWHM) resolution ranging from 33 to 5 arcmin (Mennella et al. 2011; HFI Core Team et al. 2011) and at several epochs. Leach et al. (2008) estimated the possibilities of the MHW2-filter-based detection techniques applied to the Planck satellite maps, considering two all-sky surveys. They found that the expected detection limits range from ≃0.4 Jy at 30 GHz to ≃0.22 Jy at 100 GHz, which implies that all the NEWPS sources should be detectable also in the Planck maps up to ∼100 GHz.

The Planck Early Release Compact Source Catalogue (ERCSC) has been recently released (The Collaboration 2011a) on the basis of more than one full coverage of the entire sky. The catalogue refers, in fact, to a stage when a first full-sky map plus a second run on 60 per cent of the sky were available. A Monte Carlo algorithm was implemented to select reliable sources among all the extracted candidates, making the catalogue reach a cumulative reliability ≥90 per cent. There is no requirement on completeness for the ERCSC. The 10σ photometric flux density limit of the catalogue at |b| > 30° is 0.49, 1.0, 0.67, 0.5, 0.33, 0.28, 0.25, 0.47 and 0.82 Jy at each of the nine frequencies between 30 and 857 GHz. The Planck ERCSC ‘provides a robust list of stars with dust shells, stellar cores, radio galaxies, blazars, infrared luminous galaxies, Galactic interstellar medium features, 915 cold molecular cloud core candidates, 189 Sunyaev–Zel’dovich cluster candidates as well as unclassified sources’ (The Collaboration 2011a). Many of them are object of dedicated papers about Galactic science, extragalactic sources, Sunyaev–Zel’dovich effects and cluster properties.1 The source list, with more than 15 000 unique sources, is ripe for follow-up characterization with Herschel and several ground-based observing facilities.

The first version of the Planck Legacy Catalog, together with other Planck products and a first set of cosmological papers, will be released in the first months of 2013, i.e. at the end of the proprietary period of the data acquired during the first two surveys (namely, 15 months of observation).

Planck observations help in identifying the properties of the SED in the high-frequency radio and FIR bands (The collaboration 2011b, c). The spectral behaviour of the various radio populations can be more fully studied adding ground-based observations at longer wavelengths, in order to reconstruct the properties of the different emission components.

An analysis of the variability on the five-year WMAP point sources shows that a high fraction of the sources – in general the brightest ones (Wright et al. 2009a,b) – are variable at more than 99 per cent confidence. Most AGN are variable at these radio frequencies. Their long-term variability has been well studied over the years at similar or higher frequencies (see for example Hughes et al. 1992; Hovatta et al. 2007). Also, the comparison between the WMAP catalogue and the Planck ERCSC in the corresponding bands, performed in a general, statistical sense due to variability, reveals no systematic differences between WMAP and ERCSC flux densities, while the presence of a significant scatter confirms that variability is an issue (The collaboration 2011a). Variability enhances the scattering of flux density comparisons. It also results in a bias in favour of sources being in a bright phase at the selection epoch. This makes some of the variable – and mostly bright, flat-spectrum – sources appear with a gigahertz-peaked-spectrum-like distorted spectrum during their flaring phases (Tornikoski et al. 2001; Torniainen et al. 2005).

Sadler et al. (2006) estimated a median debiased variability of 6.9 per cent at 20 GHz, on time-scales of 1 yr for a 100-mJy flux-density-limited sample of extragalactic radio sources, with only a few cases for which variability exceeded 30 per cent. Most recently, Massardi et al. (2011b) estimated at 18 GHz a median debiased variability on 9 months of 9 per cent for a sample of AT20G sources with S20 GHz > 500 mJy. The flux density levels reached during outbursts by the above-mentioned classes of Galactic radio sources are high enough to be observed with good signal-to-noise ratio (S/N) by Planck.

Driven by all the above reasons, several projects are carrying out observations at various frequency bands simultaneously to the Planck satellite surveys. The Planck ATCA Coeval Observations (PACO; Massardi et al. 2011b) project is the largest one. It consisted in the follow-up of a sample of 482 AT20G extragalactic sources, carried out in the frequency range between 4.5 and 40 GHz in the period between 2009 July and 2010 August. Several sources were observed more than once to study their variability.

We present here the Simultaneous Medicina-Planck Experiment (SiMPlE), designed to complement the PACO project in the Northern hemisphere. Its goal is to observe a sample of 263 sources at 5, 8.3 and 22 GHz almost simultaneously to the Planck observations, using the Medicina 32-m antenna and its new facilities, optimized for single-dish activities.

The SiMPlE low-frequency data, alone or combined with Planck for frequencies above 30 GHz, constitute a useful reference catalogue of bright sources over the whole Northern hemisphere. The sample selection criteria are described in Section 2, the observing strategy is given in Section 3, and data reduction techniques are discussed in Section 4. Data and spectral analysis for the 79 NEWPS sources with δ≥ 45° at 5 and 8.3 GHz are presented and discussed in Section 5. Finally, the description of the present status of the project, our main findings and some future perspectives are summarized in Section 6.

2 SAMPLE SELECTION

The selection of our sources largely exploits the NEWPS sample (Massardi et al. 2009). When observations were being planned, it constituted a unique opportunity to select high-frequency samples of bright sources in the Northern hemisphere, as it includes 253 sources with declination δ > 0°.

Cross-matches of the northern NEWPS sources with low-frequency wide-area surveys like the GB6 catalogue (Gregory et al. 1996) at 4.85 GHz or the NRAO VLA Sky Survey (NVSS; Condon et al. 1998) at 1.4 GHz have identified the candidate counterparts for 234 sources, 11 of which show multiple associations. Identifications based on the NASA Extragalactic Database (available from http://ned.ipac.caltech.edu) classified 225 of them as extragalactic objects and the remaining nine as Galactic. 18 sources do not have counterparts in lower frequency all-sky surveys with comparable flux densities and may be spurious sources.

Because of the large WMAP beam and, as a consequence, the positional uncertainty of the NEWPS detections, we used the coordinates of the low-frequency counterpart, where available, as target positions when planning follow-up observations. In case of spurious sources or multiple associations, we produced small maps at 5 GHz centred on the WMAP positions, in order to identify the possible compact sources existing as low-frequency counterparts of the WMAP detections (see Section 3.3 for further details). SiMPlE observations will therefore help us to accurately assess the reliability of the detection techniques applied to WMAP maps.

Comparisons of the NEWPS sample detections with the AT20G Bright Source Sample (Massardi et al. 2008) data indicate that the NEWPS sample is almost 91 per cent complete down to 1 Jy. The completeness of the sample is determined by the flux density scales at the epoch of the WMAP observations, and variability can alter it. However, the comparison with the coeval 30-GHz Planck observations that are reaching deeper flux densities will allow us to quantify the completeness of our sample at least at 22 GHz, once we properly account for the difference in frequency. The 22-GHz data and the comparisons with the Planck results will be presented in future papers from our group.

In addition to the Galactic sources in the NEWPS catalogue at δ > 0°, the SiMPlE project includes a sample of 10 sources representative of various classes of highly variable objects, which are being monitored in the light of the strong outbursts they might show during the Planck mission. Massive X-ray binary systems, in fact, alternate quiescent periods and strong outbursts: about 10 per cent of the more than 200 known binary systems are radio-loud (Mirabel & Rodríguez 1999). Some of them (e.g. Cyg X-3) are expected to reach flux densities up to 20 Jy (Szostek, Zdziarski & McCollough 2008; Trushkin, Bursov & Nizhelski 2008) at 8.4 GHz. Luminous blue variable stars (e.g. Eta Carinae) show sudden outbursts during which the flux density can increase to several Jy at centimetre wavelengths and tens of Jy in the millimetre band. Finally, active binary stars (e.g. RS CVn and Algol) alternate periods of quiescence, with flux densities of a few tens of mJy, and active periods characterized by flares, lasting several weeks, every 2–3 months, reaching from several hundred mJy up to some Jy at centimetre wavelengths (Umana et al. 1995). Their radio spectra show the maximum of emission at frequencies higher than 10 GHz and, during the impulsive phases, this moves up to about 100 GHz.

Pre-emptive observations of these objects began in 2009 with the Noto telescope at 43 GHz and continued at lower frequencies in Medicina, starting from 2010 June, in the framework of the SiMPlE experiment. These observations are ongoing and will cover at least one year of Planck data acquisition.

In summary, the SiMPlE sample contains 263 targets of which 253 are extracted from the NEWPS sample. 29 of these were observed by mapping the surrounding region, while On-the-fly (OTF) cross-scans were used to observe the others. Fig. 1 shows the distribution of the observed sample on the Northern hemisphere. 79 objects have declination ≥45° and constitute the so-called ‘Northern sample’, which was observed between 2010 June and November. Section 5 presents the results achieved in these epochs. Later observations, covering the full sample, will be discussed in future papers.

Figure 1

The SiMPlE sample: the Northern sample (cyan diamonds) covers the area with δ≥ 45°; asterisks show the Southern sample; green squares indicate the central positions of the mapped sky patches. The dotted lines represent a 10° masked band centred on the Galactic plane (middle dotted line).

Figure 1

The SiMPlE sample: the Northern sample (cyan diamonds) covers the area with δ≥ 45°; asterisks show the Southern sample; green squares indicate the central positions of the mapped sky patches. The dotted lines represent a 10° masked band centred on the Galactic plane (middle dotted line).

3 OBSERVING STRATEGY WITH THE MEDICINA RADIO TELESCOPE

3.1 Simultaneity with Planck

The Planck satellite scans the sky in circles passing close to the ecliptic poles and covers the whole celestial sphere in about 7 months (Dupac & Tauber 2005; see also section 1 of Mandolesi et al. 2010, and references therein). All the beams (Tauber et al. 2010b) of the entire Planck field of view cross the same sky position in a few days at low and intermediate ecliptic latitudes, in weeks or few months at high ecliptic latitudes, and then pass again on it at the subsequent survey, thereby allowing to recover source flux density variations on different time-scales (Burigana 2000; Terenzi et al. 2002, 2004). The extraction of the source flux density from Planck frequency channels is based on the analysis of frequency maps, produced by optimally weighting the time-ordered data (TOD) in pixel space. Therefore, these maps cannot be exploited to achieve information on very short-term variability, a study that necessarily requires to make use of the TOD, even if they are less sensitive than the channel maps. We then consider observations to be ‘simultaneous’ with the satellite if performed within 10 d from the satellite observations at any of its frequencies. This constituted a reasonable compromise with the scheduled observational days available to the project. This typical time sampling does not prevent the extraction of relevant variability information at least for the large majority of extragalactic sources, whose flux densities change appreciably on significantly longer time-scales. The possibility to carry out observations, possibly simultaneously with Planck, of bright sources (in particular of objects expected to show faster variability) with a finer time-scale at the Medicina radio telescope is under investigation for the next SiMPlE campaigns. In general, the Planck On-Flight Forecaster (Massardi & Burigana 2010) was applied to predict when our target sources were being observed by the satellite, according to its publicly available pre-programmed pointing list.2

The SiMPlE project obtained 21 epochs of allocated time in the period between 2010 June and December. Each epoch was scheduled for up to 24 h. Only one epoch was completely lost because of adverse weather conditions, which also affected 8.3- and 5-GHz observations. In the first 6 months of the SiMPlE project, no 22-GHz acquisitions could be performed because of the insufficient sensitivity of the available K-band receiver. The temporary installation – for commissioning purposes – of a multifeed 18–26-GHz receiver, whose final destination is the new Sardinia Radio Telescope, allowed us to carry out 22-GHz observations, together with new lower frequency ones, during the first semester of 2011.

When scheduling the observations, higher priority was assigned to the sources that were being observed by Planck, then to the sources that – in previous runs – had been flagged out because of poor data quality and, finally, to all the remaining sources, in order to observe each source as many times as possible.

3.2 OTF cross-scans and scheduling criteria at the Medicina radio telescope

Observations were carried out with the 32-m single dish of the Medicina radio telescope in the OTF scan mode (Mangum, Emerson & Greisen 2007), exploiting both hardware devices and software tools recently developed, at present still under commissioning. On the hardware side, a new analogue back-end was employed, the first one to be fully dedicated to continuum single-dish activities with the Medicina very long baseline interferometry antenna. Besides permitting the execution of high-speed scans, the OTF technique is very helpful to avoid system instabilities and to better trace atmospheric variations. Fast scans were made possible as the antenna was provided with a new control system, the Enhanced Single-dish Control System, specifically designed to perform single-dish observations exploiting the full potential of the telescope. Tests have demonstrated that scans can be carried out up to 20° min−1 without compromising the pointing accuracy. The optimized set-up for the cross-scans required acquisitions at much lower speeds, with a sampling rate of 25 Hz and a resulting spatial resolution of 60 samples per beam. Table 1 lists the main scan set-up parameters employed.

Table 1

Observational details used to plan the cross-scans; in each scan the time on-source is of about 2.5 s. The high system temperature of the 8.3-GHz receiver was due to malfunctions in the receiver cryogenic system.

Frequency Beam size Scan length Scan speed Usable bandwidth Tsys Instant rms 
(GHz) (arcmin) (HPBW) (arcmin min−1(MHz) (K) (mJy) 
5.0 7.5 180 2 × 80 30 74.1 
8.3 4.8 120 2 × 230 80 132.7 
Frequency Beam size Scan length Scan speed Usable bandwidth Tsys Instant rms 
(GHz) (arcmin) (HPBW) (arcmin min−1(MHz) (K) (mJy) 
5.0 7.5 180 2 × 80 30 74.1 
8.3 4.8 120 2 × 230 80 132.7 

The number of cross-scans to be performed on each source was adjusted in real time during the observations, according to the actual system performance and weather conditions, in order to reach an S/N of at least 10 in the final integrated scans. This dynamical scheduling was possible, thanks to an on-purpose-developed tool: the Positional On-the-flight-scan Planner (POP). As run-time execution of this tool completes in few seconds, POP allowed us to quickly produce new schedules whenever the weather and/or system conditions changed during an observing session. The only input required to the observer consists in the target coordinate list, the Local Sidereal Time (LST) which the schedule is supposed to be executed, the observing frequency and, optionally, the estimated flux density of the sources. POP schedules the sources after checking for their visibility, taking into account the telescope movement limits and duration in azimuth and elevation, sorting them in ascending RA, to minimize the slewing time between targets and maximize the number of observed targets during the allocated time.

For each source, POP calculates the minimum number of scans required to reach a noise level 10 times smaller than the 23-GHz WMAP flux density, provided in the input position list. If no flux density is provided, POP schedules for each target a number of scans equal to a user-defined value indicated in the software configuration settings: this is of use in case of bad weather conditions or instrumental failures, when a longer integration time is needed.

Table 2 shows some examples of the cross-scans required to obtain S/N = 10 for different flux density limits.

Table 2

Number of cross-scans performed to achieve S/N = 10 on sources of the given flux density limit, considering average weather conditions and the actual system set-up exploited during the observing session. A minimum of two cross-scans was carried out even on the brightest sources, even though a single scan would have been more than sufficient from the sensitivity point of view, to cross-check for possible artefacts in the data.

Flux density limit (mJy) 5 GHz cross-scans 8.3 GHz cross-scans 
200 22 
500 
1000 
Flux density limit (mJy) 5 GHz cross-scans 8.3 GHz cross-scans 
200 22 
500 
1000 

Each subscan on the sample sources is 5 half-power beam width (HPBW) long, both at 5 and 8.3 GHz, in order to always have enough off-source samples and thus to better evaluate the background. The scan speed was adjusted to keep the same sampling rate (60 samples per beam) at both frequencies, according to the different HPBW. Such a dense sampling allowed us to better fit the Gaussian curve produced by the source, as it is described by numerous points. Scans on calibrators were set slightly larger (7 HPBW): because of their crucial role in the sources flux densities recovery, the larger number of off-source samples provides a more precise identification of the baseline, translating into a more reliable measurement of the parameters which will subsequently be employed in the calibration phase (details in Section 4).

3.3 Region mapping

Some sources in the NEWPS five-years 5σ catalogue are classified as undefined because of the lack of counterpart in low-frequency catalogues. Some other objects have multiple associations, within the beam size, with low-frequency wide-area surveys (NVSS and/or GB6). These samples might include spurious detections on WMAP maps, as well as extended sources or peaks of Galactic foreground emission erroneously identified as sources by the detection procedures.

In order to identify or resolve the candidate sources, we scanned patches of the sky around the source positions. We selected a sample of 29 undefined targets using coordinates of the most likely counterpart in the GB6 or NVSS catalogues when possible, otherwise we used the coordinates of the NEWPS detection. For each of these sources, we pointed and mapped patches in the sky of about 50 × 50 arcmin2, centred on the estimated position of the sources. The scanning strategy consists of 21 equally spaced scans in each direction (RA, Dec.). Furthermore, consecutive scans are performed with opposite movement directions. To get a visual display of the mapped regions, we built a grid based on the RA and Dec. coordinates of the considered source and we associated the average value of a scan lying in each grid step to the corresponding RA, Dec. position. The resolution of the grid could be changed, but in general, for a good visualization of the sky patch, we decided for values ranging from 20 to 25 grid steps. This is practically equivalent to rebin the scans in steps ranging from 1.75 to 1.4 arcmin.

4 DATA REDUCTION

4.1 Data quality inspection and flagging

In optimal conditions for observations, each scan has the shape of the beam transfer function, i.e. a Gaussian with an FWHM corresponding to the beam size,3 overlapped to a baseline that corresponds to the off-source zero level of the signal. Along the scans, amplitude fluctuations are given by a Gaussian noise. However, cloudy weather, the presence of random contributions by radio frequency interference (RFI) or digital noise heavily affected portions of the data, appearing as bumpy baselines or spike-like features.

Hence, the quality of each scan can be assessed by fitting a Gaussian function plus a linear baseline to the data and comparing the fitted parameters to the expected values. The overall goodness of the fit is also checked through a χ2 analysis. A similar test allows one to draw considerations about the Gaussian FWHM, the length of the baselines, the S/N and the differences between the slopes of the two parts of the baseline (i.e. left and right with respect to the Gaussian). The broad variety of possible scan behaviours and the large number of parameters to be considered did not allow us to easily limit the parameter space. Furthermore, as our observations were carried out within a commissioning phase, we considered it would have been useful to inspect and classify the various problems affecting the data. For these reasons we decided to manually inspect the whole data set and categorize the scans according to their quality and the features affecting them, if any. Hence, we developed a tool that displays the individual scans overlaying the result of the Gaussian plus linear fit as a reference (see Fig. 2). Users are then asked to express their evaluation on the scan; the visualization of the fit improves the homogeneity in the flagging criteria.

Figure 2

A subscan of a source (solid grey line) displayed by the flagging procedure. Here the Gaussian fit of the scan (solid black line) and the linear fit of the left- and right-hand baseline (dashed lines) are also plotted.

Figure 2

A subscan of a source (solid grey line) displayed by the flagging procedure. Here the Gaussian fit of the scan (solid black line) and the linear fit of the left- and right-hand baseline (dashed lines) are also plotted.

We pay particular attention to the contributions affecting the linearity of the baseline: bumps, RFI and different slopes of the left and right baseline arms. These features heavily affect the linear and the Gaussian fit of each scan, and thus scans presenting any of these contributions are rejected. Of course, any scan characterized by an odd shape of the beam transfer function is rejected as well.

Bad weather conditions also reduce the S/N, so that in the worst cases (i.e. faint sources with high noise level) the sources were completely embedded in the noise fluctuations. Averaging over several scans reduces the noise and amplifies the S/N; thus, for these critical sources the flagging was performed also on the integrated scans.

In future phases we plan to automatize the flagging process on the basis of a statistical analysis of the flagging done so far, to minimize the subjectivity introduced in the flagging procedure by visual inspection.

4.2 OTF scan processing

We have developed the OTF Scan Calibration-Reduction (OSCaR) pipeline for the data reduction of calibrators and target sources. It constitutes an easily customizable ensemble of idl routines capable of handling up to huge amounts of data, operating at all the SiMPlE frequencies.

A run of the entire pipeline does not require a large amount of memory as well as a huge computational power: for about 10 days of flagged data the complete process requires less than 10 min.4 The entire software package can be easily modified to be used for projects involving OTF cross-scan observations.

The main steps of OSCaR (see Fig. 3) are described in the following sections and can be summarized as follows: (i) the estimation of the factor to convert the raw data to flux density units by rescaling the arbitrary counts measured on calibrators to their known flux densities; (ii) the reconstruction of the variation with time of the counts-to-Jy factor and of the component of the flux density error due to calibration and (iii) the calculation of the source flux densities and their errors, by applying the correct counts-to-Jy factor, integrating the scans for each source, and fitting them with a Gaussian that reproduces the receiver response function.

Figure 3

Scheme of the main operations in OSCaR. See Section 4.2 for a detailed description of the procedures.

Figure 3

Scheme of the main operations in OSCaR. See Section 4.2 for a detailed description of the procedures.

4.2.1 Recovering of the counts-to-Jy conversion factor

The first task of OSCaR consists in recovering the conversion factors to transform the raw signal intensity, given in arbitrary counts, to a calibrated flux density (Jy). This is done by fitting the scans with a Gaussian fit, plus a linear fit, according to the following:  

1
formula
with  
2
formula

In these equations, A0 is the height of the Gaussian, A1 is the centre of the Gaussian, A2 is the width of the Gaussian, A3 is the constant normalization term and A4 is the slope of the baseline. In this way, we measure the Gaussian curve amplitude and compare it with the source absolute flux density. The flux density/amplitude ratio is the counts-to-Jy factor valid for the observed elevation position.

We consider as primary calibrators 3C286 and 3C295, the only two sources reporting negligible variability by Ott (1993) with respect to the original scale of Baars et al. (1977). This flux density stability has been confirmed by recent Effelsberg observations (Kraus & Bach, private communication). Then, whenever it is possible, we measure the flux density of other calibrators (3C147, 3C48, 3C123, NGC 7027, DR 21) against the primary ones, exploiting the counts-to-Jy factors recovered on the primary calibrators. This allowed us the possibility of at least one calibrator observation per time interval of few hours (typically 2–3 h in good observing conditions).

A timeline of the conversion factors is recovered along all the days of acquisitions. In particular, once we collected all the conversion factors on an entire session of observation (see Fig. 4), we interpolated them in time, obtaining a continuous projection of these factors in the interval between two contiguous calibrator observations. We chose this strategy in order to have a time-dependent conversion factor, reflecting in a smoother way the oscillations of each computed factor during the day. These factors vary whenever a change happens in the weather conditions – implying a different atmospheric absorption affecting the source flux density – and when the system gain, for intrinsic reasons or user-defined choices, changes as well. Higher frequency observations are more sensitive to these contributions, and thus need a more frequent and accurate evaluation of the counts-to-Jy factors.

Figure 4

Conversion factor timeline recovered from an entire observing session. The cross and square symbols represent left and right channel, respectively.

Figure 4

Conversion factor timeline recovered from an entire observing session. The cross and square symbols represent left and right channel, respectively.

4.2.2 Flux densities

The flux density measurements on the observed sources are performed through an algorithm which is very similar to the one used in recovering the counts-to-Jy conversion factors. The equation for the Gaussian fit is also the same. The accepted scans are selected and integrated according to the tags provided during the flagging phase. The integration is performed through a precise positional alignment, in turn allowed by the very reliable antenna pointing system. It is also possible to define the time interval within which more scans on the same source must be considered consecutive and thus integrated. Otherwise they are considered as separated measurements, each processed with the proper calibration factor.

Before proceeding with the flux density computation, a further check on the HPBW of the scan is performed. We accepted scans with values of the HPBW within 20 per cent variation from the nominal value. This criterion not only selects the scans for which the instrument behaved properly, but also can remove from our analysis sources which are extended by more than 1.2 × HPBW, for which our flux density estimates constitute only a lower limit.

We obtain separate flux density estimates for the two acquisition channels and for each scan direction. We first compute the flux density from the cross created by the integration of the RA, Dec. scans in each channel, then through a weighted average we achieve a unique flux density for the considered source. The application of the counts-to-Jy factor takes into account that the source and the calibrator had been observed at different elevations. The conversion factor is properly rescaled by means of the standard gain–elevation curve provided for the Medicina dish. The equations are the following:  

3
formula
at 5 GHz, while at 8.3 GHz it becomes  
4
formula
G represents the elevation-dependent normalized gain, while e is the elevation of the considered source/calibrator. A flux density compensation related to a possible offset in the pointing of the sources is also taken into account according to the following equation:  
5
formula

In this equation j = RA, Dec., k=L, R indicate the left and right channels, x represents the positional offset according to the direction considered, and HPBW is the nominal value of the beam at the considered frequency. We calculate the positional offset by comparing the position of the peak detection – resulting from the fitting function – to the input coordinates values. The positional offset of about 200 individual pointings is shown in Fig. 5.

Figure 5

The difference between the input and the recovered RA and Dec. position of the Northern sample sources for about 200 individual pointings at 5 GHz (for comparison, the beam FWHM is 7.5 arcmin).

Figure 5

The difference between the input and the recovered RA and Dec. position of the Northern sample sources for about 200 individual pointings at 5 GHz (for comparison, the beam FWHM is 7.5 arcmin).

Finally, each source is calibrated using the proper conversion factor. This is recovered by matching the acquisition epoch to the calibration timeline. In this way we ensure an acceptable time distance between the observed source and the calibration factor, in order to minimize the possibility of weather or system variations.

The set-up of the run is interactively performed after launching the main program. Among the available options, there is the possibility to call each procedure independently, to provide a list of sources to be analysed or to work on an entire observing session.

Through the tags provided during the flagging phase, we analyse each channel of each subscan independently. While this procedure would be standard for a polarization analysis, for the total intensity study we have the possibility to choose one or both channels of each subscan. Particular attention was dedicated to the handling of the time tag of each scan. We aimed at collecting as many observations as possible, of each source, at different times. These time intervals can span from hours to weeks or months. Thus, we implemented the pipeline in order to have a coherent integration of the scans concatenated in time. The automatization of this strategy of integration permits to easily handle multiple observations of calibrators in a single day and consequently the creation of the detailed calibration timeline we use to calculate the flux densities. The possibility to recover the flux densities of selected sources in more observing sessions at once makes OSCaR well suited to evaluate variability as well.

We could have relied on the telescope pointing/acquisition system for an immediate, sample-by-sample integration of the scans. Through a dedicated test, we confirmed that the maximum misalignment encountered, comparing the initial positions of the scans, corresponds to one sample of data (7.2 arcsec for 3° min−1 scans, i.e. less than 2 per cent of the HPBW). However, for a more precise estimation of counts-to-Jy conversion factors and flux densities, it is important to avoid any possible offset; thus, any misalignment, even of such entity, is corrected during the integration of the scans.

4.2.3 Flux density error estimation

The error budget in the final flux density results from two main components: the calibration error Scal and the noise error SN:  

6
formula

The two terms have identical physical causes, although with different weights, and can be treated using a common formalism. The contribution to each component is given by  

7
formula
with i = cal, N.

The baseline error (δbaseline) is mainly due to the white instrumental and background noise, and the varying influence of the ground radiation while the antenna is scanning at different angles. It has two spectral components: one showing white spectrum (background, atmosphere, statistic uncertainty) and the other characterized by 1/f behaviour (long-time drift of detectors and slow atmospheric changes between the telescope and the target). The confusion limit, the asymptotic limit of the white component in the case of a large number of samples, represents only a part of the baseline error.

In order to compute this contribution we subtract the linear fit, performed on the scan neglecting the Gaussian bell, from the baseline. This reduces the long-time drift effect. Then we calculate the standard deviation of the subtracted data. In this way, we take into account both the white noise contribution and the spurious residual effects on time-scale of a single-source observation. As a general rule, we decided to keep margins, when fitting the linear baselines, neglecting the first 10 points on the left-hand and right-hand sides of the Gaussian fit, whose width was calculated from the beam size.

The Gauss error (δGauss) estimates the goodness of the Gaussian fit. It represents the error committed in calculating the coefficient A0 (amplitude of the Gaussian) of the exponential term, and can be ascribed either to white scatter effects affecting the whole scan or to local drops and spikes of signal, mostly in correspondence of the tip. However, in most cases, the preliminary operation of data flagging is expected to have already prevented the Gaussian shape from evident anomalies. Operatively, the Gaussian fit is calculated over the integrated scans and the associated error is provided by the fitting routine itself. The final error in the flux density, indicated in equation (7), comes out as the amplitude uncertainty of the height of the bell estimated through the Gaussian fit.

Because of the flagging strategy adopted, acting individually on each subscan, the number of good data was different for RA and Dec. scans as well as for the two polarization channels, for each source observed. For this reason, equation (7) was calculated also for right-hand channel (RHC) and left-hand channel (LHC) when scanning in RA and Dec.

In accordance with the observing strategy, about 20 sources were observed in the time window between two calibrators.5 In a few cases the primary calibrators were not available during the whole observing session: consequently, we were forced to calculate the calibration constants using secondary calibrators. Through dedicated tests, we found out that this strategy could affect the calibration error by less than 5 per cent in a day with good observing conditions. Therefore, we decided to calculate a weighted calibration error for each source, relating the calibration error to the time window considered instead of calculating an average error over the whole run.

The calibration error on each observed source comes out from weighting the errors committed on the two nearest calibrators by the distance in time of each source from the calibrators. Hence, given τ1 and τ2, the distance in time of the ith source from calibrators 1 and 2 (characterized, respectively, by errors forumlaand forumla), the weighted error is  

8
formula

Similar to ΔSi, ΣCAL was calculated for channels RHC and LHC both in RA and Dec.; when combining these error terms with equation (6) we get the following four-term array:  

9
formula
 
10
formula
 
11
formula
 
12
formula

The calibration errors, calculated following the above procedure, were hence compared with the error calculated just considering the whole error bar obtained when displaying the calibration constants referring to all the calibrators available during the observing day considered. This comparison is displayed in Fig. 6.

Figure 6

A typical conversion factor timeline. The black solid line represents the effective conversion factor applied to the data, while the grey zone represents the error associated with the factors themselves. The dashed lines represent a rough estimate of the error that can be considered for the whole day of year.

Figure 6

A typical conversion factor timeline. The black solid line represents the effective conversion factor applied to the data, while the grey zone represents the error associated with the factors themselves. The dashed lines represent a rough estimate of the error that can be considered for the whole day of year.

The final error ΣFX in the flux density of each source comes out as the square root of the sum of the squares:  

13
formula

The error contribution can be mapped through a plot, showing how it varies (in percentage) with the source intensity (Fig. 7), at 5 and 8.3 GHz.

Figure 7

The flux densities from 100 measurements of the Northern sample sources (crosses) versus their percentage error are plotted. The upper panel shows the 5-GHz measurements, while the lower those at 8.3 GHz. The black lines represent the fits of the plotted data and the same quantity for the other frequency is overplotted for comparison (dashed lines). Multiple observations of the same sources are also considered.

Figure 7

The flux densities from 100 measurements of the Northern sample sources (crosses) versus their percentage error are plotted. The upper panel shows the 5-GHz measurements, while the lower those at 8.3 GHz. The black lines represent the fits of the plotted data and the same quantity for the other frequency is overplotted for comparison (dashed lines). Multiple observations of the same sources are also considered.

4.3 Simultaneous ATCA–Medicina observations

In addition to the NEWPS Northern hemisphere sample, we observed 12 sources with δ < 0° extracted from the targets list of the PACO project. We observed almost all these targets simultaneously with the two facilities, i.e. the Medicina antenna and the ATCA interferometer. In any case, observations were performed within 10 d from the Planck satellite ones. The PACO project observed them in 24 × 512 MHz-wide frequency subbands between 4.5 and 40 GHz, including data at 5.244 and 8.232 GHz. Since the two projects exploit completely different telescopes, data-reduction pipelines, calibration schemes and sources, this sample, although small, was used as a meaningful test to verify whether our procedures gave consistent results.

The SEDs of the equatorial targets including the Medicina and ATCA radio telescopes, and the Planck satellite data are presented in Fig. 8, showing a fairly good agreement.

Figure 8

SEDs for a sample of equatorial targets observed simultaneously with the Medicina radio telescope (filled diamonds), the ATCA (cross; in the framework of the PACO project) and the Planck satellite (empty diamonds; data from ERCSC, The Collaboration 2011a). The target 0238−084 was observed from Medicina with some days of delay. The displacement in its SED could be due to variability of the source itself.

Figure 8

SEDs for a sample of equatorial targets observed simultaneously with the Medicina radio telescope (filled diamonds), the ATCA (cross; in the framework of the PACO project) and the Planck satellite (empty diamonds; data from ERCSC, The Collaboration 2011a). The target 0238−084 was observed from Medicina with some days of delay. The displacement in its SED could be due to variability of the source itself.

The comparison is unbiased by source variability and depends only on the instrumental properties. The Planck satellite lower frequency channel is too high to transfer its CMB dipole-based flux density calibration to the low-frequency Medicina telescope channels, but we can compare the two ground-based facilities flux density scales. The flux density calibration for the ATCA data is based on the observation of one single very stable source, PKS B1934−638. Fig. 9 shows the flux density comparisons at 5 and 8.3 GHz. The best-fitting line at 5 GHz has a slope equal to 1.03 ± 0.09 and crosses the y-axis at (−0.39 ± 0.36) Jy. At 8 GHz it has slope equal to 1.02 ± 0.15 and crosses the y-axis at (−0.62 ± 0.65) Jy: the flux density is consistent within the error bars between the two instruments. A small bias in calibration is probably present, but the small sample does not allow to quantify it. Further observations of a larger equatorial sample are ongoing to more accurately quantify the calibration discrepancies. This will lead us to obtain a common calibration scale between several facilities, including – at mm frequencies – also the Planck satellite.

Figure 9

Flux density comparison between SiMPlE (black) and PACO (cyan) data at 5 and 5.244 GHz (filled symbols) and at 8.3 and 8.232 GHz (empty symbols), respectively. No corrections for the small difference in frequency have been applied. The best-fitting lines at 5 and 8 GHz are, respectively, the solid and dashed lines. The dotted line represents unity.

Figure 9

Flux density comparison between SiMPlE (black) and PACO (cyan) data at 5 and 5.244 GHz (filled symbols) and at 8.3 and 8.232 GHz (empty symbols), respectively. No corrections for the small difference in frequency have been applied. The best-fitting lines at 5 and 8 GHz are, respectively, the solid and dashed lines. The dotted line represents unity.

5 THE δ≥45° SAMPLE

After the flagging and the removal of data points with S/N lower than 5, 67 of the 69 NEWPS-selected sources with δ≥ 45° observed with OTF cross-scans showed reliable data at 5 GHz. The exceptions are the 179th and the 245th sources in the NEWPS catalogue: all their data were plagued by bad weather conditions. 59 sources have valid data also at 8 GHz in at least one epoch in the June–December runs. Table 4 lists the data at 5 and 8.3 GHz for one observing epoch for each source per row. The columns are as follows.

Table 4

The SiMPlE Northern sample.

ID RA (h m sDec. (° ‴) Date Sim S5 GHz (mJy) σ5 GHz (mJy) S8.3 GHz (mJy) σ8.3 GHz (mJy) ID 
n513 23:56:56.609 67:51:37.705 2010-07-25  – 478 – 145.2 87GB235426.3+673455 
n513 23:56:56.609 67:51:37.705 2010-09-04 371 – 92.9 – 87GB235426.3+673455 
n512 23:54:21.724 45:53:04.401 2010-07-18 1369 – 146.8 – GB6 J2354+4553 
n512 23:54:21.724 45:53:04.401 2010-07-24 1304 – 102.0 – GB6 J2354+4553 
n512 23:54:21.724 45:53:04.401 2010-07-25 – 1925 – 226.3 GB6 J2354+4553 
n512 23:54:21.724 45:53:04.401 2010-08-08 – 1143 – 101.4 GB6 J2354+4553 
n511 23:56:22.822 81:52:52.604 2010-07-18  877 – 152.1 – NVSS J235622+815252 
n511 23:56:22.822 81:52:52.604 2010-07-24  1112 – 112.6 – NVSS J235622+815252 
n511 23:56:22.822 81:52:52.604 2010-08-08  – 757 – 121.2 NVSS J235622+815252 
n511 23:56:22.822 81:52:52.604 2010-10-08 – 666 – 107.5 NVSS J235622+815252 
n497 23:22:26.001 50:57:51.996 2010-07-24 1467 – 106.3 – NVSS J232226+505752 
n497 23:22:26.001 50:57:51.996 2010-07-25 – 1216 – 224.3 NVSS J232226+505752 
n497 23:22:26.001 50:57:51.996 2010-10-08  – 1252 – 102.9 NVSS J232226+505752 
n461 21:53:28.704 47:16:03.007 2010-07-25  – 1054 – 300.2 GB6 J2153+4716 
n461 21:53:28.704 47:16:03.007 2010-10-10  1321 – 73.8 – GB6 J2153+4716 
n437 20:38:37.009 51:19:13.098 2010-07-18  – 2664 – 240.9 GB6 J2038+5119 
n437 20:38:37.009 51:19:13.098 2010-07-25  – 2805 – 247.4 GB6 J2038+5119 
n437 20:38:37.009 51:19:13.098 2010-08-02  – 2640 – 251.3 GB6 J2038+5119 
n437 20:38:37.009 51:19:13.098 2010-08-08  – 2703 – 86.3 GB6 J2038+5119 
n437 20:38:37.009 51:19:13.098 2010-09-30  2423 – 218.2 – GB6 J2038+5119 
n433 20:22:06.702 61:36:58.895 2010-07-18 3197 3057 181.9 216.1 GB6 J2022+6137 
n433 20:22:06.702 61:36:58.895 2010-07-25 – 3492 – 275.6 GB6 J2022+6137 
n433 20:22:06.702 61:36:58.895 2010-08-02 – 3113 – 259.8 GB6 J2022+6137 
n433 20:22:06.702 61:36:58.895 2010-08-08 – 3164 – 90.5 GB6 J2022+6137 
n433 20:22:06.702 61:36:58.895 2010-08-25 – 3030 – 321.3 GB6 J2022+6137 
n433 20:22:06.702 61:36:58.895 2010-09-30  3421 – 228.7 – GB6 J2022+6137 
n430 20:09:52.507 72:29:19.488 2010-07-18  889 – 186.8 – GB6 J2009+7229 
n430 20:09:52.507 72:29:19.488 2010-07-24  811 – 114.8 – GB6 J2009+7229 
n430 20:09:52.507 72:29:19.488 2010-07-25  – 953 – 253.4 GB6 J2009+7229 
n430 20:09:52.507 72:29:19.488 2010-09-30 1205 – 243.8 – GB6 J2009+7229 
n429 20:05:31.289 77:52:43.898 2010-07-18  1458 1193 180.6 240.9 NVSS J200531+775243 
n429 20:05:31.289 77:52:43.898 2010-07-25  – 951 – 172.1 NVSS J200531+775243 
n429 20:05:31.289 77:52:43.898 2010-08-02  – 1016 – 223.5 NVSS J200531+775243 
n429 20:05:31.289 77:52:43.898 2010-08-08  – 1477 – 123.5 NVSS J200531+775243 
n429 20:05:31.289 77:52:43.898 2010-09-30 1172 – 215.8 – NVSS J200531+775243 
n417 19:27:30.447 61:17:32.902 2010-07-18  807 – 177.2 – GB6 J1927+6117 
n417 19:27:30.447 61:17:32.902 2010-09-04  679 – 89.6 – GB6 J1927+6117 
n417 19:27:30.447 61:17:32.902 2010-10-09  – 843 – 118.5 GB6 J1927+6117 
n416 19:27:48.530 73:58:02.089 2010-07-18  3606 3729 134.0 206.2 GB6 J1927+7357 
n416 19:27:48.530 73:58:02.089 2010-07-24  3333 – 123.6 – GB6 J1927+7357 
n416 19:27:48.530 73:58:02.089 2010-07-25  – 3958 – 240.9 GB6 J1927+7357 
n416 19:27:48.530 73:58:02.089 2010-08-02  – 4050 – 232.9 GB6 J1927+7357 
n416 19:27:48.530 73:58:02.089 2010-08-08  – 3925 – 82.0 GB6 J1927+7357 
n409 18:49:15.901 67:05:40.906 2010-07-18 1598 2201 169.0 245.8 GB6 J1849+6705 
n409 18:49:15.901 67:05:40.906 2010-08-08 – 2108 – 87.6 GB6 J1849+6705 
n409 18:49:15.901 67:05:40.906 2010-08-25  – 1957 – 324.0 GB6 J1849+6705 
n407 18:42:33.640 68:09:24.999 2010-07-18 767 528 136.5 236.6 GB6 J1842+6809 
n406 18:42:26.931 79:45:17.303 2010-07-18  4092 2436 181.8 222.1 3C390.3 
n406 18:42:26.931 79:45:17.303 2010-07-24  3839 2770 116.0 311.5 3C390.3 
n401 18:29:31.802 48:44:46.707 2010-07-18  5333 3842 127.1 220.0 GB6 J1829+4844 
n401 18:29:31.802 48:44:46.707 2010-08-02  – 3778 – 201.1 GB6 J1829+4844 
n401 18:29:31.802 48:44:46.707 2010-08-08  – 3896 – 89.2 GB6 J1829+4844 
n401 18:29:31.802 48:44:46.707 2010-08-25 – 3555 – 235.7 GB6 J1829+4844 
n401 18:29:31.802 48:44:46.707 2010-09-03 – 3686 – 123.8 GB6 J1829+4844 
n401 18:29:31.802 48:44:46.707 2010-09-07 4834 – 56.0 – GB6 J1829+4844 
n399 18:24:07.083 56:51:01.203 2010-07-18  1555 1535 170.3 244.2 GB6 J1824+5650 
n399 18:24:07.083 56:51:01.203 2010-08-02 – 1536 – 271.8 GB6 J1824+5650 
n399 18:24:07.083 56:51:01.203 2010-08-08 – 1504 – 88.4 GB6 J1824+5650 
n399 18:24:07.083 56:51:01.203 2010-08-25 – 1487 – 269.8 GB6 J1824+5650 
n394 18:06:50.457 69:49:28.094 2010-07-18 1734 – 167.5 – GB6 J1806+6949 
n394 18:06:50.457 69:49:28.094 2010-07-18 1734 – 167.5 – GB6 J1806+6949 
n394 18:06:50.457 69:49:28.094 2010-08-02  – 1686 – 230.8 GB6 J1806+6949 
n394 18:06:50.457 69:49:28.094 2010-08-08  – 1736 – 81.5 GB6 J1806+6949 
n394 18:06:50.457 69:49:28.094 2010-09-07  1731 – 56.8 – GB6 J1806+6949 
n389 18:00:45.762 78:28:05.001 2010-07-18  2600 2889 171.0 217.8 NVSS J180045+782804 
n389 18:00:45.762 78:28:05.001 2010-07-24  2938 2948 205.6 245.4 NVSS J180045+782804 
n389 18:00:45.762 78:28:05.001 2010-08-02  – 2761 – 202.9 NVSS J180045+782804 
n389 18:00:45.762 78:28:05.001 2010-08-08  – 3062 – 97.5 NVSS J180045+782804 
n389 18:00:45.762 78:28:05.001 2010-09-03  – 2446 – 120.0 NVSS J180045+782804 
n389 18:00:45.762 78:28:05.001 2010-09-07  2459 – 63.4 – NVSS J180045+782804 
n385 17:48:32.878 70:05:51.590 2010-07-18 – 916 – 224.1 GB6 J1748+7005 
n385 17:48:32.878 70:05:51.590 2010-09-07  757 – 62.5 – GB6 J1748+7005 
n382 17:40:36.987 52:11:43.606 2010-07-18  1496 1555 155.3 244.3 GB6 J1740+5211 
n382 17:40:36.987 52:11:43.606 2010-08-02 – 1574 – 208.5 GB6 J1740+5211 
n382 17:40:36.987 52:11:43.606 2010-08-08 – 1623 – 84.3 GB6 J1740+5211 
n382 17:40:36.987 52:11:43.606 2010-09-03  – 1564 – 116.4 GB6 J1740+5211 
n382 17:40:36.987 52:11:43.606 2010-09-07  1491 – 54.3 – GB6 J1740+5211 
n381 17:39:57.129 47:37:58.304 2010-09-07  723 – 58.0 – GB6 J1739+4738 
n373 17:27:27.649 45:30:40.004 2010-07-18  – 917 – 224.9 GB6 J1727+4530 
n373 17:27:27.649 45:30:40.004 2010-09-03 – 955 – 100.2 GB6 J1727+4530 
n373 17:27:27.649 45:30:40.004 2010-09-07  998 – 79.3 – GB6 J1727+4530 
n364 16:57:20.760 57:05:54.501 2010-09-03  – 538 – 96.3 GB6 J1657+5705 
n364 16:57:20.760 57:05:54.501 2010-09-07  533 – 53.2 – GB6 J1657+5705 
n358 16:42:07.800 68:56:38.895 2010-07-02 – 2924 – 278.9 GB6 J1642+6856 
n358 16:42:07.800 68:56:38.895 2010-07-18  – 2526 – 191.3 GB6 J1642+6856 
n358 16:42:07.800 68:56:38.895 2010-08-02  – 2443 – 198.7 GB6 J1642+6856 
n358 16:42:07.800 68:56:38.895 2010-08-08  – 2412 – 78.3 GB6 J1642+6856 
n358 16:42:07.800 68:56:38.895 2010-08-25  – 2286 – 174.6 GB6 J1642+6856 
n358 16:42:07.800 68:56:38.895 2010-09-03  – 2290 – 108.7 GB6 J1642+6856 
n358 16:42:07.800 68:56:38.895 2010-09-07  2230 – 60.7 – GB6 J1642+6856 
n355 16:38:13.411 57:20:24.207 2010-07-18 – 1471 – 210.5 GB6 J1638+5720 
n355 16:38:13.411 57:20:24.207 2010-09-03  – 1618 – 114.3 GB6 J1638+5720 
n355 16:38:13.411 57:20:24.207 2010-09-07  1507 – 61.6 – GB6 J1638+5720 
n354 16:37:45.330 47:17:41.197 2010-09-07  1023 – 137.1 – GB6 J1637+4717 
n354 16:37:45.330 47:17:41.197 2010-10-10  894 – 90.6 – GB6 J1637+4717 
n352 16:30:51.130 82:33:45.604 2010-07-18  – 494 – 247.1 NVSS J163226+823220 
n352 16:30:51.130 82:33:45.604 2010-09-07  1108 – 79.8 – NVSS J163226+823220 
n338 15:49:17.468 50:38:06.200 2010-07-18 – 1088 – 245.8 GB6 J1549+5038 
n338 15:49:17.468 50:38:06.200 2010-09-03  – 924 – 93.0 GB6 J1549+5038 
n338 15:49:17.468 50:38:06.200 2010-09-07  992 – 55.5 – GB6 J1549+5038 
n323 14:59:07.628 71:40:19.904 2010-07-18  – 2114 – 238.8 GB6 J1459+7140 
n323 14:59:07.628 71:40:19.904 2010-09-03  – 2026 – 94.9 GB6 J1459+7140 
n323 14:59:07.628 71:40:19.904 2010-09-07  3000 – 53.7 – GB6 J1459+7140 
n318 14:43:01.450 52:01:38.204 2010-07-18 1291 1038 114.7 216.7 GB6 J1443+5201 
n318 14:43:01.450 52:01:38.204 2010-10-10  1247 – 81.9 – GB6 J1443+5201 
n316 14:36:45.681 63:36:37.499 2010-07-18  – 1781 – 244.7 GB6 J1436+6336 
n316 14:36:45.681 63:36:37.499 2010-09-03  – 1702 – 118.1 GB6 J1436+6336 
n316 14:36:45.681 63:36:37.499 2010-09-07  1626 – 63.0 – GB6 J1436+6336 
n309 14:19:46.501 54:23:15.099 2010-07-18  1066 1062 133.3 268.1 GB6 J1419+5423 
n307 14:11:20.629 52:12:08.998 2010-07-18  6152 3396 134.0 213.1 GB6 J1411+5212 
n303 13:57:55.441 76:43:20.903 2010-07-18  598 – 122.8 – NVSS J135755+764320 
n303 13:57:55.441 76:43:20.903 2010-09-03  – 801 – 139.8 NVSS J135755+764320 
n300 13:44:08.621 66:06:11.503 2010-07-18  823 – 131.5 – 87GB134217.7+661742 
n300 13:44:08.621 66:06:11.503 2010-09-03  – 524 – 88.9 87GB134217.7+661742 
n300 13:44:08.621 66:06:11.503 2010-09-07  737 – 51.0 – 87GB134217.7+661742 
n283 13:02:52.482 57:48:37.598 2010-10-09  – 430 – 121.0 87GB130049.5+580435 
n283 13:02:52.482 57:48:37.598 2010-10-10  722 – 88.9 – 87GB130049.5+580435 
n268 12:19:06.500 48:29:57.006 2010-07-18  – 548 – 213.3 GB6 J1219+4830 
n268 12:19:06.500 48:29:57.006 2010-10-10  637 – 85.1 – GB6 J1219+4830 
n264 12:00:19.211 73:00:45.703 2010-07-18  2626 1778 137.2 237.9 GB6 J1200+7300 
n264 12:00:19.211 73:00:45.703 2010-07-18  2626 1778 137.2 237.9 GB6 J1200+7300 
n261 11:53:12.792 80:58:29.802 2010-07-18  1535 1186 145.2 218.8 NVSS J115312+805829 
n261 11:53:12.792 80:58:29.802 2010-08-02  – 1093 – 179.7 NVSS J115312+805829 
n261 11:53:12.792 80:58:29.802 2010-08-08  – 1448 – 113.8 NVSS J115312+805829 
n261 11:53:12.792 80:58:29.802 2010-08-25  1169 1466 84.1 179.4 NVSS J115312+805829 
n260 11:53:24.510 49:31:09.502 2010-08-02  – 1055 – 176.1 GB6 J1153+4931 
n260 11:53:24.510 49:31:09.502 2010-08-25  914 3064 70.2 310.2 GB6 J1153+4931 
n244 10:48:27.568 71:43:35.295 2010-07-02  – 1117 – 256.3 GB6 J1048+7143 
n244 10:48:27.568 71:43:35.295 2010-07-18  – 896 – 242.6 GB6 J1048+7143 
n244 10:48:27.568 71:43:35.295 2010-08-02  5947 – 705.2 – GB6 J1048+7143 
n230 09:58:47.219 65:33:54.311 2010-07-18  1522 1404 110.7 281.7 GB6 J0958+6534 
n230 09:58:47.219 65:33:54.311 2010-08-02  1405 – 78.2 – GB6 J0958+6534 
n230 09:58:47.219 65:33:54.311 2010-08-25  1083 – 69.6 – GB6 J0958+6534 
n230 09:58:47.219 65:33:54.311 2010-10-09  1381 – 102.6 – GB6 J0958+6534 
n230 09:58:47.219 65:33:54.311 2010-10-10  1394 – 103.8 – GB6 J0958+6534 
n229 09:58:19.698 47:25:06.995 2010-10-09  907 – 89.2 – GB6 J0958+4725 
n229 09:58:19.698 47:25:06.995 2010-10-10  916 – 90.9 – GB6 J0958+4725 
n228 09:57:38.181 55:22:57.397 2010-07-02  – 1592 – 235.6 GB6 J0957+5522 
n228 09:57:38.181 55:22:57.397 2010-07-18  1906 1584 105.5 252.4 GB6 J0957+5522 
n228 09:57:38.181 55:22:57.397 2010-10-09  1930 1435 81.8 132.9 GB6 J0957+5522 
n228 09:57:38.181 55:22:57.397 2010-10-10  1945 – 82.8 – GB6 J0957+5522 
n226 09:55:51.881 69:40:46.106 2010-07-18  3476 2530 107.0 230.5 GB6 J0955+6940 
n226 09:55:51.881 69:40:46.106 2010-10-09 – 2347 – 144.6 GB6 J0955+6940 
n221 09:21:36.229 62:15:51.402 2010-07-18  1527 1520 100.6 263.6 GB6 J0921+6215 
n221 09:21:36.229 62:15:51.402 2010-10-09 1496 1267 85.0 138.3 GB6 J0921+6215 
n221 09:21:36.229 62:15:51.402 2010-10-10 1504 – 85.3 – GB6 J0921+6215 
n211 09:03:04.039 46:51:04.705 2010-07-18  1601 – 103.0 – GB6 J0903+4650 
n211 09:03:04.039 46:51:04.705 2010-10-09  – 1250 – 137.5 GB6 J0903+4650 
n206 08:41:24.459 70:53:41.411 2010-07-18  1756 – 99.3 – GB6 J0841+7053 
n206 08:41:24.459 70:53:41.411 2010-08-02  1793 1675 56.2 286.5 GB6 J0841+7053 
n206 08:41:24.459 70:53:41.411 2010-08-08  – 1572 – 136.9 GB6 J0841+7053 
n206 08:41:24.459 70:53:41.411 2010-08-25  1451 7177 66.6 275.4 GB6 J0841+7053 
n204 08:37:22.441 58:25:01.295 2010-10-09 1034 908 90.7 143.9 GB6 J0837+5825 
n204 08:37:22.441 58:25:01.295 2010-10-10 1037 – 91.0 – GB6 J0837+5825 
n202 08:34:54.910 55:34:20.994 2010-07-18  5291 – 94.8 – GB6 J0834+5534 
n202 08:34:54.910 55:34:20.994 2010-10-09 5227 2886 99.7 131.6 GB6 J0834+5534 
n202 08:34:54.910 55:34:20.994 2010-10-10 5281 – 101.1 – GB6 J0834+5534 
n194 08:13:36.070 48:13:01.897 2010-07-02  4799 – 614.3 – GB6 J0813+4813 
n194 08:13:36.070 48:13:01.897 2010-07-18  4195 – 124.8 – GB6 J0813+4813 
n194 08:13:36.070 48:13:01.897 2010-10-09 4028 – 153.2 – GB6 J0813+4813 
n194 08:13:36.070 48:13:01.897 2010-10-10 4066 – 154.9 – GB6 J0813+4813 
n193 08:08:39.739 49:50:36.099 2010-08-02  377 600 87.8 234.6 GB6 J0808+4950 
n193 08:08:39.739 49:50:36.099 2010-08-25  353 880 70.0 293.8 GB6 J0808+4950 
n191 08:05:18.221 61:44:23.196 2010-07-18  1016 – 105.7 – GB6 J0805+6144 
n189 07:53:01.450 53:52:59.402 2010-07-18  626 – 88.7 – GB6 J0753+5353 
n177 07:28:11.299 67:48:47.087 2010-07-18  971 – 88.4 – GB6 J0728+6748 
n174 07:21:53.101 71:20:36.703 2010-07-18  1760 2080 94.1 253.8 GB6 J0721+7120 
n174 07:21:53.101 71:20:36.703 2010-08-25  1051 – 73.2 – GB6 J0721+7120 
n164 06:39:21.890 73:24:58.288 2010-07-18  983 – 106.8 – GB6 J0639+7324 
n164 06:39:21.890 73:24:58.288 2010-07-24  815 973 124.0 240.6 GB6 J0639+7324 
n152 06:07:52.679 67:20:55.600 2010-07-02  – 1089 – 329.1 GB6 J0607+6720 
n152 06:07:52.679 67:20:55.600 2010-07-18  670 – 89.8 – GB6 J0607+6720 
n152 06:07:52.679 67:20:55.600 2010-07-24  715 – 112.2 – GB6 J0607+6720 
n146 05:42:36.151 49:51:07.699 2010-07-24  7534 4776 132.3 250.3 GB6 J0542+4951 
n146 05:42:36.151 49:51:07.699 2010-09-04  7662 – 238.7 – GB6 J0542+4951 
n146 05:42:36.151 49:51:07.699 2010-10-08  – 4679 – 100.2 GB6 J0542+4951 
n146 05:42:36.151 49:51:07.699 2010-10-09  7692 – 88.7 – GB6 J0542+4951 
n146 05:42:36.151 49:51:07.699 2010-10-10  7751 – 90.2 – GB6 J0542+4951 
n139 05:33:15.881 48:22:52.906 2010-07-24  – 803 – 288.1 GB6 J0533+4822 
n139 05:33:15.881 48:22:52.906 2010-10-08  – 1016 – 104.9 GB6 J0533+4822 
n139 05:33:15.881 48:22:52.906 2010-07-24  – 803 – 288.1 GB6 J0533+4822 
n139 05:33:15.881 48:22:52.906 2010-10-08  – 1016 – 104.9 GB6 J0533+4822 
n139 05:33:15.881 48:22:52.906 2010-10-09  839 – 69.3 – GB6 J0533+4822 
n139 05:33:15.881 48:22:52.906 2010-10-10  845 – 71.0 – GB6 J0533+4822 
n95 04:10:45.630 76:56:45.212 2010-07-18  2812 1984 82.5 252.9 NVSS J041045+765645 
n95 04:10:45.630 76:56:45.212 2010-07-24  2664 2380 119.6 292.2 NVSS J041045+765645 
n95 04:10:45.630 76:56:45.212 2010-08-02  4125 – 91.7 – NVSS J041045+765645 
n95 04:10:45.630 76:56:45.212 2010-09-03  2268 – 143.2 – NVSS J041045+765645 
n95 04:10:45.630 76:56:45.212 2010-09-30 2706 – 219.0 – NVSS J041045+765645 
n66 03:03:35.280 47:16:16.300 2010-09-04 1757 – 84.8 – GB6 J0303+4716 
n66 03:03:35.280 47:16:16.300 2010-09-07 – 1851 – 120.7 GB6 J0303+4716 
n51 02:17:30.880 73:49:32.296 2010-07-02  4233 – 238.3 – GB6 J0217+7349 
n51 02:17:30.880 73:49:32.296 2010-07-18  – 3895 – 305.2 GB6 J0217+7349 
n51 02:17:30.880 73:49:32.296 2010-08-02  4006 3735 60.5 202.2 GB6 J0217+7349 
n51 02:17:30.880 73:49:32.296 2010-08-08  – 3904 – 88.4 GB6 J0217+7349 
n51 02:17:30.880 73:49:32.296 2010-08-25  – 4472 – 186.6 GB6 J0217+7349 
n51 02:17:30.880 73:49:32.296 2010-09-04 3845 – 91.1 – GB6 J0217+7349 
n51 02:17:30.880 73:49:32.296 2010-09-07 – 3707 – 89.6 GB6 J0217+7349 
n41 01:36:58.580 47:51:29.301 2010-08-02  3199 173.0 – GB6 J0136+4751 
n41 01:36:58.580 47:51:29.301 2010-08-08 – 2926 – 76.9 GB6 J0136+4751 
n41 01:36:58.580 47:51:29.301 2010-09-04  2829 – 99.5 – GB6 J0136+4751 
n41 01:36:58.580 47:51:29.301 2010-10-08  – 4324 – 109.2 GB6 J0136+4751 
n41 01:36:58.580 47:51:29.301 2010-10-09  2359 – 67.7 – GB6 J0136+4751 
n41 01:36:58.580 47:51:29.301 2010-10-10  2379 – 69.5 – GB6 J0136+4751 
n15 00:43:08.790 52:03:34.398 2010-07-24  3769 – 126.8 – GB6 J0043+5203 
n15 00:43:08.790 52:03:34.398 2010-07-25  – 2421 – 203.7 GB6 J0043+5203 
n15 00:43:08.790 52:03:34.398 2010-09-04  3656 – 93.6 – GB6 J0043+5203 
n15 00:43:08.790 52:03:34.398 2010-10-08  – 2376 – 108.7 GB6 J0043+5203 
n14 00:42:19.430 57:08:36.701 2010-07-24  716 – 92.4 – GB6 J0042+5708 
n14 00:42:19.430 57:08:36.701 2010-07-25  – 955 – 197.1 GB6 J0042+5708 
n14 00:42:19.430 57:08:36.701 2010-09-04  732 – 84.3 – GB6 J0042+5708 
n14 00:42:19.430 57:08:36.701 2010-10-08  – 754 – 106.0 GB6 J0042+5708 
n8 00:19:45.800 73:27:29.707 2010-07-02  944 – 255.4 – GB6 J0019+7327 
n8 00:19:45.800 73:27:29.707 2010-07-18  – 1195 – 237.0 GB6 J0019+7327 
n8 00:19:45.800 73:27:29.707 2010-07-25  – 1095 – 231.3 GB6 J0019+7327 
n8 00:19:45.800 73:27:29.707 2010-08-02  1054 – 44.3 – GB6 J0019+7327 
n8 00:19:45.800 73:27:29.707 2010-09-04 935 – 87.3 – GB6 J0019+7327 
ID RA (h m sDec. (° ‴) Date Sim S5 GHz (mJy) σ5 GHz (mJy) S8.3 GHz (mJy) σ8.3 GHz (mJy) ID 
n513 23:56:56.609 67:51:37.705 2010-07-25  – 478 – 145.2 87GB235426.3+673455 
n513 23:56:56.609 67:51:37.705 2010-09-04 371 – 92.9 – 87GB235426.3+673455 
n512 23:54:21.724 45:53:04.401 2010-07-18 1369 – 146.8 – GB6 J2354+4553 
n512 23:54:21.724 45:53:04.401 2010-07-24 1304 – 102.0 – GB6 J2354+4553 
n512 23:54:21.724 45:53:04.401 2010-07-25 – 1925 – 226.3 GB6 J2354+4553 
n512 23:54:21.724 45:53:04.401 2010-08-08 – 1143 – 101.4 GB6 J2354+4553 
n511 23:56:22.822 81:52:52.604 2010-07-18  877 – 152.1 – NVSS J235622+815252 
n511 23:56:22.822 81:52:52.604 2010-07-24  1112 – 112.6 – NVSS J235622+815252 
n511 23:56:22.822 81:52:52.604 2010-08-08  – 757 – 121.2 NVSS J235622+815252 
n511 23:56:22.822 81:52:52.604 2010-10-08 – 666 – 107.5 NVSS J235622+815252 
n497 23:22:26.001 50:57:51.996 2010-07-24 1467 – 106.3 – NVSS J232226+505752 
n497 23:22:26.001 50:57:51.996 2010-07-25 – 1216 – 224.3 NVSS J232226+505752 
n497 23:22:26.001 50:57:51.996 2010-10-08  – 1252 – 102.9 NVSS J232226+505752 
n461 21:53:28.704 47:16:03.007 2010-07-25  – 1054 – 300.2 GB6 J2153+4716 
n461 21:53:28.704 47:16:03.007 2010-10-10  1321 – 73.8 – GB6 J2153+4716 
n437 20:38:37.009 51:19:13.098 2010-07-18  – 2664 – 240.9 GB6 J2038+5119 
n437 20:38:37.009 51:19:13.098 2010-07-25  – 2805 – 247.4 GB6 J2038+5119 
n437 20:38:37.009 51:19:13.098 2010-08-02  – 2640 – 251.3 GB6 J2038+5119 
n437 20:38:37.009 51:19:13.098 2010-08-08  – 2703 – 86.3 GB6 J2038+5119 
n437 20:38:37.009 51:19:13.098 2010-09-30  2423 – 218.2 – GB6 J2038+5119 
n433 20:22:06.702 61:36:58.895 2010-07-18 3197 3057 181.9 216.1 GB6 J2022+6137 
n433 20:22:06.702 61:36:58.895 2010-07-25 – 3492 – 275.6 GB6 J2022+6137 
n433 20:22:06.702 61:36:58.895 2010-08-02 – 3113 – 259.8 GB6 J2022+6137 
n433 20:22:06.702 61:36:58.895 2010-08-08 – 3164 – 90.5 GB6 J2022+6137 
n433 20:22:06.702 61:36:58.895 2010-08-25 – 3030 – 321.3 GB6 J2022+6137 
n433 20:22:06.702 61:36:58.895 2010-09-30  3421 – 228.7 – GB6 J2022+6137 
n430 20:09:52.507 72:29:19.488 2010-07-18  889 – 186.8 – GB6 J2009+7229 
n430 20:09:52.507 72:29:19.488 2010-07-24  811 – 114.8 – GB6 J2009+7229 
n430 20:09:52.507 72:29:19.488 2010-07-25  – 953 – 253.4 GB6 J2009+7229 
n430 20:09:52.507 72:29:19.488 2010-09-30 1205 – 243.8 – GB6 J2009+7229 
n429 20:05:31.289 77:52:43.898 2010-07-18  1458 1193 180.6 240.9 NVSS J200531+775243 
n429 20:05:31.289 77:52:43.898 2010-07-25  – 951 – 172.1 NVSS J200531+775243 
n429 20:05:31.289 77:52:43.898 2010-08-02  – 1016 – 223.5 NVSS J200531+775243 
n429 20:05:31.289 77:52:43.898 2010-08-08  – 1477 – 123.5 NVSS J200531+775243 
n429 20:05:31.289 77:52:43.898 2010-09-30 1172 – 215.8 – NVSS J200531+775243 
n417 19:27:30.447 61:17:32.902 2010-07-18  807 – 177.2 – GB6 J1927+6117 
n417 19:27:30.447 61:17:32.902 2010-09-04  679 – 89.6 – GB6 J1927+6117 
n417 19:27:30.447 61:17:32.902 2010-10-09  – 843 – 118.5 GB6 J1927+6117 
n416 19:27:48.530 73:58:02.089 2010-07-18  3606 3729 134.0 206.2 GB6 J1927+7357 
n416 19:27:48.530 73:58:02.089 2010-07-24  3333 – 123.6 – GB6 J1927+7357 
n416 19:27:48.530 73:58:02.089 2010-07-25  – 3958 – 240.9 GB6 J1927+7357 
n416 19:27:48.530 73:58:02.089 2010-08-02  – 4050 – 232.9 GB6 J1927+7357 
n416 19:27:48.530 73:58:02.089 2010-08-08  – 3925 – 82.0 GB6 J1927+7357 
n409 18:49:15.901 67:05:40.906 2010-07-18 1598 2201 169.0 245.8 GB6 J1849+6705 
n409 18:49:15.901 67:05:40.906 2010-08-08 – 2108 – 87.6 GB6 J1849+6705 
n409 18:49:15.901 67:05:40.906 2010-08-25  – 1957 – 324.0 GB6 J1849+6705 
n407 18:42:33.640 68:09:24.999 2010-07-18 767 528 136.5 236.6 GB6 J1842+6809 
n406 18:42:26.931 79:45:17.303 2010-07-18  4092 2436 181.8 222.1 3C390.3 
n406 18:42:26.931 79:45:17.303 2010-07-24  3839 2770 116.0 311.5 3C390.3 
n401 18:29:31.802 48:44:46.707 2010-07-18  5333 3842 127.1 220.0 GB6 J1829+4844 
n401 18:29:31.802 48:44:46.707 2010-08-02  – 3778 – 201.1 GB6 J1829+4844 
n401 18:29:31.802 48:44:46.707 2010-08-08  – 3896 – 89.2 GB6 J1829+4844 
n401 18:29:31.802 48:44:46.707 2010-08-25 – 3555 – 235.7 GB6 J1829+4844 
n401 18:29:31.802 48:44:46.707 2010-09-03 – 3686 – 123.8 GB6 J1829+4844 
n401 18:29:31.802 48:44:46.707 2010-09-07 4834 – 56.0 – GB6 J1829+4844 
n399 18:24:07.083 56:51:01.203 2010-07-18  1555 1535 170.3 244.2 GB6 J1824+5650 
n399 18:24:07.083 56:51:01.203 2010-08-02 – 1536 – 271.8 GB6 J1824+5650 
n399 18:24:07.083 56:51:01.203 2010-08-08 – 1504 – 88.4 GB6 J1824+5650 
n399 18:24:07.083 56:51:01.203 2010-08-25 – 1487 – 269.8 GB6 J1824+5650 
n394 18:06:50.457 69:49:28.094 2010-07-18 1734 – 167.5 – GB6 J1806+6949 
n394 18:06:50.457 69:49:28.094 2010-07-18 1734 – 167.5 – GB6 J1806+6949 
n394 18:06:50.457 69:49:28.094 2010-08-02  – 1686 – 230.8 GB6 J1806+6949 
n394 18:06:50.457 69:49:28.094 2010-08-08  – 1736 – 81.5 GB6 J1806+6949 
n394 18:06:50.457 69:49:28.094 2010-09-07  1731 – 56.8 – GB6 J1806+6949 
n389 18:00:45.762 78:28:05.001 2010-07-18  2600 2889 171.0 217.8 NVSS J180045+782804 
n389 18:00:45.762 78:28:05.001 2010-07-24  2938 2948 205.6 245.4 NVSS J180045+782804 
n389 18:00:45.762 78:28:05.001 2010-08-02  – 2761 – 202.9 NVSS J180045+782804 
n389 18:00:45.762 78:28:05.001 2010-08-08  – 3062 – 97.5 NVSS J180045+782804 
n389 18:00:45.762 78:28:05.001 2010-09-03  – 2446 – 120.0 NVSS J180045+782804 
n389 18:00:45.762 78:28:05.001 2010-09-07  2459 – 63.4 – NVSS J180045+782804 
n385 17:48:32.878 70:05:51.590 2010-07-18 – 916 – 224.1 GB6 J1748+7005 
n385 17:48:32.878 70:05:51.590 2010-09-07  757 – 62.5 – GB6 J1748+7005 
n382 17:40:36.987 52:11:43.606 2010-07-18  1496 1555 155.3 244.3 GB6 J1740+5211 
n382 17:40:36.987 52:11:43.606 2010-08-02 – 1574 – 208.5 GB6 J1740+5211 
n382 17:40:36.987 52:11:43.606 2010-08-08 – 1623 – 84.3 GB6 J1740+5211 
n382 17:40:36.987 52:11:43.606 2010-09-03  – 1564 – 116.4 GB6 J1740+5211 
n382 17:40:36.987 52:11:43.606 2010-09-07  1491 – 54.3 – GB6 J1740+5211 
n381 17:39:57.129 47:37:58.304 2010-09-07  723 – 58.0 – GB6 J1739+4738 
n373 17:27:27.649 45:30:40.004 2010-07-18  – 917 – 224.9 GB6 J1727+4530 
n373 17:27:27.649 45:30:40.004 2010-09-03 – 955 – 100.2 GB6 J1727+4530 
n373 17:27:27.649 45:30:40.004 2010-09-07  998 – 79.3 – GB6 J1727+4530 
n364 16:57:20.760 57:05:54.501 2010-09-03  – 538 – 96.3 GB6 J1657+5705 
n364 16:57:20.760 57:05:54.501 2010-09-07  533 – 53.2 – GB6 J1657+5705 
n358 16:42:07.800 68:56:38.895 2010-07-02 – 2924 – 278.9 GB6 J1642+6856 
n358 16:42:07.800 68:56:38.895 2010-07-18  – 2526 – 191.3 GB6 J1642+6856 
n358 16:42:07.800 68:56:38.895 2010-08-02  – 2443 – 198.7 GB6 J1642+6856 
n358 16:42:07.800 68:56:38.895 2010-08-08  – 2412 – 78.3 GB6 J1642+6856 
n358 16:42:07.800 68:56:38.895 2010-08-25  – 2286 – 174.6 GB6 J1642+6856 
n358 16:42:07.800 68:56:38.895 2010-09-03  – 2290 – 108.7 GB6 J1642+6856 
n358 16:42:07.800 68:56:38.895 2010-09-07  2230 – 60.7 – GB6 J1642+6856 
n355 16:38:13.411 57:20:24.207 2010-07-18 – 1471 – 210.5 GB6 J1638+5720 
n355 16:38:13.411 57:20:24.207 2010-09-03  – 1618 – 114.3 GB6 J1638+5720 
n355 16:38:13.411 57:20:24.207 2010-09-07  1507 – 61.6 – GB6 J1638+5720 
n354 16:37:45.330 47:17:41.197 2010-09-07  1023 – 137.1 – GB6 J1637+4717 
n354 16:37:45.330 47:17:41.197 2010-10-10  894 – 90.6 – GB6 J1637+4717 
n352 16:30:51.130 82:33:45.604 2010-07-18  – 494 – 247.1 NVSS J163226+823220 
n352 16:30:51.130 82:33:45.604 2010-09-07  1108 – 79.8 – NVSS J163226+823220 
n338 15:49:17.468 50:38:06.200 2010-07-18 – 1088 – 245.8 GB6 J1549+5038 
n338 15:49:17.468 50:38:06.200 2010-09-03  – 924 – 93.0 GB6 J1549+5038 
n338 15:49:17.468 50:38:06.200 2010-09-07  992 – 55.5 – GB6 J1549+5038 
n323 14:59:07.628 71:40:19.904 2010-07-18  – 2114 – 238.8 GB6 J1459+7140 
n323 14:59:07.628 71:40:19.904 2010-09-03  – 2026 – 94.9 GB6 J1459+7140 
n323 14:59:07.628 71:40:19.904 2010-09-07  3000 – 53.7 – GB6 J1459+7140 
n318 14:43:01.450 52:01:38.204 2010-07-18 1291 1038 114.7 216.7 GB6 J1443+5201 
n318 14:43:01.450 52:01:38.204 2010-10-10  1247 – 81.9 – GB6 J1443+5201 
n316 14:36:45.681 63:36:37.499 2010-07-18  – 1781 – 244.7 GB6 J1436+6336 
n316 14:36:45.681 63:36:37.499 2010-09-03  – 1702 – 118.1 GB6 J1436+6336 
n316 14:36:45.681 63:36:37.499 2010-09-07  1626 – 63.0 – GB6 J1436+6336 
n309 14:19:46.501 54:23:15.099 2010-07-18  1066 1062 133.3 268.1 GB6 J1419+5423 
n307 14:11:20.629 52:12:08.998 2010-07-18  6152 3396 134.0 213.1 GB6 J1411+5212 
n303 13:57:55.441 76:43:20.903 2010-07-18  598 – 122.8 – NVSS J135755+764320 
n303 13:57:55.441 76:43:20.903 2010-09-03  – 801 – 139.8 NVSS J135755+764320 
n300 13:44:08.621 66:06:11.503 2010-07-18  823 – 131.5 – 87GB134217.7+661742 
n300 13:44:08.621 66:06:11.503 2010-09-03  – 524 – 88.9 87GB134217.7+661742 
n300 13:44:08.621 66:06:11.503 2010-09-07  737 – 51.0 – 87GB134217.7+661742 
n283 13:02:52.482 57:48:37.598 2010-10-09  – 430 – 121.0 87GB130049.5+580435 
n283 13:02:52.482 57:48:37.598 2010-10-10  722 – 88.9 – 87GB130049.5+580435 
n268 12:19:06.500 48:29:57.006 2010-07-18  – 548 – 213.3 GB6 J1219+4830 
n268 12:19:06.500 48:29:57.006 2010-10-10  637 – 85.1 – GB6 J1219+4830 
n264 12:00:19.211 73:00:45.703 2010-07-18  2626 1778 137.2 237.9 GB6 J1200+7300 
n264 12:00:19.211 73:00:45.703 2010-07-18  2626 1778 137.2 237.9 GB6 J1200+7300 
n261 11:53:12.792 80:58:29.802 2010-07-18  1535 1186 145.2 218.8 NVSS J115312+805829 
n261 11:53:12.792 80:58:29.802 2010-08-02  – 1093 – 179.7 NVSS J115312+805829 
n261 11:53:12.792 80:58:29.802 2010-08-08  – 1448 – 113.8 NVSS J115312+805829 
n261 11:53:12.792 80:58:29.802 2010-08-25  1169 1466 84.1 179.4 NVSS J115312+805829 
n260 11:53:24.510 49:31:09.502 2010-08-02  – 1055 – 176.1 GB6 J1153+4931 
n260 11:53:24.510 49:31:09.502 2010-08-25  914 3064 70.2 310.2 GB6 J1153+4931 
n244 10:48:27.568 71:43:35.295 2010-07-02  – 1117 – 256.3 GB6 J1048+7143 
n244 10:48:27.568 71:43:35.295 2010-07-18  – 896 – 242.6 GB6 J1048+7143 
n244 10:48:27.568 71:43:35.295 2010-08-02  5947 – 705.2 – GB6 J1048+7143 
n230 09:58:47.219 65:33:54.311 2010-07-18  1522 1404 110.7 281.7 GB6 J0958+6534 
n230 09:58:47.219 65:33:54.311 2010-08-02  1405 – 78.2 – GB6 J0958+6534 
n230 09:58:47.219 65:33:54.311 2010-08-25  1083 – 69.6 – GB6 J0958+6534 
n230 09:58:47.219 65:33:54.311 2010-10-09  1381 – 102.6 – GB6 J0958+6534 
n230 09:58:47.219 65:33:54.311 2010-10-10  1394 – 103.8 – GB6 J0958+6534 
n229 09:58:19.698 47:25:06.995 2010-10-09  907 – 89.2 – GB6 J0958+4725 
n229 09:58:19.698 47:25:06.995 2010-10-10  916 – 90.9 – GB6 J0958+4725 
n228 09:57:38.181 55:22:57.397 2010-07-02  – 1592 – 235.6 GB6 J0957+5522 
n228 09:57:38.181 55:22:57.397 2010-07-18  1906 1584 105.5 252.4 GB6 J0957+5522 
n228 09:57:38.181 55:22:57.397 2010-10-09  1930 1435 81.8 132.9 GB6 J0957+5522 
n228 09:57:38.181 55:22:57.397 2010-10-10  1945 – 82.8 – GB6 J0957+5522 
n226 09:55:51.881 69:40:46.106 2010-07-18  3476 2530 107.0 230.5 GB6 J0955+6940 
n226 09:55:51.881 69:40:46.106 2010-10-09 – 2347 – 144.6 GB6 J0955+6940 
n221 09:21:36.229 62:15:51.402 2010-07-18  1527 1520 100.6 263.6 GB6 J0921+6215 
n221 09:21:36.229 62:15:51.402 2010-10-09 1496 1267 85.0 138.3 GB6 J0921+6215 
n221 09:21:36.229 62:15:51.402 2010-10-10 1504 – 85.3 – GB6 J0921+6215 
n211 09:03:04.039 46:51:04.705 2010-07-18  1601 – 103.0 – GB6 J0903+4650 
n211 09:03:04.039 46:51:04.705 2010-10-09  – 1250 – 137.5 GB6 J0903+4650 
n206 08:41:24.459 70:53:41.411 2010-07-18  1756 – 99.3 – GB6 J0841+7053 
n206 08:41:24.459 70:53:41.411 2010-08-02  1793 1675 56.2 286.5 GB6 J0841+7053 
n206 08:41:24.459 70:53:41.411 2010-08-08  – 1572 – 136.9 GB6 J0841+7053 
n206 08:41:24.459 70:53:41.411 2010-08-25  1451 7177 66.6 275.4 GB6 J0841+7053 
n204 08:37:22.441 58:25:01.295 2010-10-09 1034 908 90.7 143.9 GB6 J0837+5825 
n204 08:37:22.441 58:25:01.295 2010-10-10 1037 – 91.0 – GB6 J0837+5825 
n202 08:34:54.910 55:34:20.994 2010-07-18  5291 – 94.8 – GB6 J0834+5534 
n202 08:34:54.910 55:34:20.994 2010-10-09 5227 2886 99.7 131.6 GB6 J0834+5534 
n202 08:34:54.910 55:34:20.994 2010-10-10 5281 – 101.1 – GB6 J0834+5534 
n194 08:13:36.070 48:13:01.897 2010-07-02  4799 – 614.3 – GB6 J0813+4813 
n194 08:13:36.070 48:13:01.897 2010-07-18  4195 – 124.8 – GB6 J0813+4813 
n194 08:13:36.070 48:13:01.897 2010-10-09 4028 – 153.2 – GB6 J0813+4813 
n194 08:13:36.070 48:13:01.897 2010-10-10 4066 – 154.9 – GB6 J0813+4813 
n193 08:08:39.739 49:50:36.099 2010-08-02  377 600 87.8 234.6 GB6 J0808+4950 
n193 08:08:39.739 49:50:36.099 2010-08-25  353 880 70.0 293.8 GB6 J0808+4950 
n191 08:05:18.221 61:44:23.196 2010-07-18  1016 – 105.7 – GB6 J0805+6144 
n189 07:53:01.450 53:52:59.402 2010-07-18  626 – 88.7 – GB6 J0753+5353 
n177 07:28:11.299 67:48:47.087 2010-07-18  971 – 88.4 – GB6 J0728+6748 
n174 07:21:53.101 71:20:36.703 2010-07-18  1760 2080 94.1 253.8 GB6 J0721+7120 
n174 07:21:53.101 71:20:36.703 2010-08-25  1051 – 73.2 – GB6 J0721+7120 
n164 06:39:21.890 73:24:58.288 2010-07-18  983 – 106.8 – GB6 J0639+7324 
n164 06:39:21.890 73:24:58.288 2010-07-24  815 973 124.0 240.6 GB6 J0639+7324 
n152 06:07:52.679 67:20:55.600 2010-07-02  – 1089 – 329.1 GB6 J0607+6720 
n152 06:07:52.679 67:20:55.600 2010-07-18  670 – 89.8 – GB6 J0607+6720 
n152 06:07:52.679 67:20:55.600 2010-07-24  715 – 112.2 – GB6 J0607+6720 
n146 05:42:36.151 49:51:07.699 2010-07-24  7534 4776 132.3 250.3 GB6 J0542+4951 
n146 05:42:36.151 49:51:07.699 2010-09-04  7662 – 238.7 – GB6 J0542+4951 
n146 05:42:36.151 49:51:07.699 2010-10-08  – 4679 – 100.2 GB6 J0542+4951 
n146 05:42:36.151 49:51:07.699 2010-10-09  7692 – 88.7 – GB6 J0542+4951 
n146 05:42:36.151 49:51:07.699 2010-10-10  7751 – 90.2 – GB6 J0542+4951 
n139 05:33:15.881 48:22:52.906 2010-07-24  – 803 – 288.1 GB6 J0533+4822 
n139 05:33:15.881 48:22:52.906 2010-10-08  – 1016 – 104.9 GB6 J0533+4822 
n139 05:33:15.881 48:22:52.906 2010-07-24  – 803 – 288.1 GB6 J0533+4822 
n139 05:33:15.881 48:22:52.906 2010-10-08  – 1016 – 104.9 GB6 J0533+4822 
n139 05:33:15.881 48:22:52.906 2010-10-09  839 – 69.3 – GB6 J0533+4822 
n139 05:33:15.881 48:22:52.906 2010-10-10  845 – 71.0 – GB6 J0533+4822 
n95 04:10:45.630 76:56:45.212 2010-07-18  2812 1984 82.5 252.9 NVSS J041045+765645 
n95 04:10:45.630 76:56:45.212 2010-07-24  2664 2380 119.6 292.2 NVSS J041045+765645 
n95 04:10:45.630 76:56:45.212 2010-08-02  4125 – 91.7 – NVSS J041045+765645 
n95 04:10:45.630 76:56:45.212 2010-09-03  2268 – 143.2 – NVSS J041045+765645 
n95 04:10:45.630 76:56:45.212 2010-09-30 2706 – 219.0 – NVSS J041045+765645 
n66 03:03:35.280 47:16:16.300 2010-09-04 1757 – 84.8 – GB6 J0303+4716 
n66 03:03:35.280 47:16:16.300 2010-09-07 – 1851 – 120.7 GB6 J0303+4716 
n51 02:17:30.880 73:49:32.296 2010-07-02  4233 – 238.3 – GB6 J0217+7349 
n51 02:17:30.880 73:49:32.296 2010-07-18  – 3895 – 305.2 GB6 J0217+7349 
n51 02:17:30.880 73:49:32.296 2010-08-02  4006 3735 60.5 202.2 GB6 J0217+7349 
n51 02:17:30.880 73:49:32.296 2010-08-08  – 3904 – 88.4 GB6 J0217+7349 
n51 02:17:30.880 73:49:32.296 2010-08-25  – 4472 – 186.6 GB6 J0217+7349 
n51 02:17:30.880 73:49:32.296 2010-09-04 3845 – 91.1 – GB6 J0217+7349 
n51 02:17:30.880 73:49:32.296 2010-09-07 – 3707 – 89.6 GB6 J0217+7349 
n41 01:36:58.580 47:51:29.301 2010-08-02  3199 173.0 – GB6 J0136+4751 
n41 01:36:58.580 47:51:29.301 2010-08-08 – 2926 – 76.9 GB6 J0136+4751 
n41 01:36:58.580 47:51:29.301 2010-09-04  2829 – 99.5 – GB6 J0136+4751 
n41 01:36:58.580 47:51:29.301 2010-10-08  – 4324 – 109.2 GB6 J0136+4751 
n41 01:36:58.580 47:51:29.301 2010-10-09  2359 – 67.7 – GB6 J0136+4751 
n41 01:36:58.580 47:51:29.301 2010-10-10  2379 – 69.5 – GB6 J0136+4751 
n15 00:43:08.790 52:03:34.398 2010-07-24  3769 – 126.8 – GB6 J0043+5203 
n15 00:43:08.790 52:03:34.398 2010-07-25  – 2421 – 203.7 GB6 J0043+5203 
n15 00:43:08.790 52:03:34.398 2010-09-04  3656 – 93.6 – GB6 J0043+5203 
n15 00:43:08.790 52:03:34.398 2010-10-08  – 2376 – 108.7 GB6 J0043+5203 
n14 00:42:19.430 57:08:36.701 2010-07-24  716 – 92.4 – GB6 J0042+5708 
n14 00:42:19.430 57:08:36.701 2010-07-25  – 955 – 197.1 GB6 J0042+5708 
n14 00:42:19.430 57:08:36.701 2010-09-04  732 – 84.3 – GB6 J0042+5708 
n14 00:42:19.430 57:08:36.701 2010-10-08  – 754 – 106.0 GB6 J0042+5708 
n8 00:19:45.800 73:27:29.707 2010-07-02  944 – 255.4 – GB6 J0019+7327 
n8 00:19:45.800 73:27:29.707 2010-07-18  – 1195 – 237.0 GB6 J0019+7327 
n8 00:19:45.800 73:27:29.707 2010-07-25  – 1095 – 231.3 GB6 J0019+7327 
n8 00:19:45.800 73:27:29.707 2010-08-02  1054 – 44.3 – GB6 J0019+7327 
n8 00:19:45.800 73:27:29.707 2010-09-04 935 – 87.3 – GB6 J0019+7327 

  • Column 1. Source identification. For sources in the NEWPS catalogue the id corresponds to the sequential number in the Massardi et al. (2009) catalogue.

  • Column 2 and 3. Right ascension in hour and declination in degrees.

  • Column 4. Epoch of observation in YYYY-MM-DD.

  • Column 5. Flag asterisks for simultaneity with the Planck observations.

  • Column 6 and 7. Flux density at 5 and 8.3 GHz in mJy.

  • Column 8 and 9. Flux density error at 5 and 8.3 GHz in mJy.

10 more targets were observed by mapping the surrounding sky region and will be discussed in the following section.

5.1 Region maps with δ≥ 45°

Among the regions that we mapped at 5 GHz, 10 have declination δ≥ 45°. The maps are shown in Fig. 11.

Figure 11

The 10 regions of sky mapped around the undefined sources described in Section 3.3. The flux density scale is expressed in Jy beam−1.

Figure 11

The 10 regions of sky mapped around the undefined sources described in Section 3.3. The flux density scale is expressed in Jy beam−1.

For each map, we perform a two-dimensional Gaussian fit, in order to identify the candidate source and estimate a lower limit to the source flux densities. This procedure fits an elliptical Gaussian equation to gridded data. The fitting function is  

14
formula
with the elliptical function described by U = (x′/a)2+ (y′/b)2, while A0 and A1 are the constant term and the scale factor, respectively. The rotated coordinate system is defined as  
15
formula
 
16
formula
In our case, x and y are the scan directions RA and Dec., (h, k) is the centre of the ellipse, and T is the rotation angle from the x-axis in clockwise direction. Furthermore, it is possible to recover the width of the Gaussian in the two directions, the location of the centre on the two axes, and the rotation of the ellipse with respect to the x-axis. Once the peak position was identified we estimated the peak flux density, which is a lower limit to the source flux density. As the profile of an extended source could be far from a Gaussian, this approach was used only to identify a peak and estimate a peak flux density. As the peak flux density is only a lower limit of the integrated flux density, we confirm the candidate source detection only in case the peak flux density is at least three times larger than the noise estimated on the map. Another requirement is that the source must be univocally identified in the map, i.e. there is only one peak and the scans passing across it survived the visual flagging procedure. Table 3 lists the fit details for the 10 maps in the Northern sample region.

Table 3

Peak flux densities extracted for the 10 mapped regions with δ≥ 45°. The last column indicates as 1 the sources that have Speak 5 GHz/σ > 3 and the scans across the peak position passed the visual flagging procedure.

NEWPS ID RA (°) δ (°) Speak 5GHz (Jy) σ (Jy) Candidate flag 
n1 00:03:38 68:28:50 1.24 0.11 
n22 00:52:56 56:35:22 2.59 0.26 
n157 06:14:21 61:28:32 1.17 0.35 
n365 16:57:46 48:08:32 0.71 0.35 
n432 20:19:36 46:03:05 21.82 0.34 
n440 20:52:47 55:11:44 2.05 0.78 
n448 21:13:23 59:21:51 0.79 0.32 
n449 21:17:36 60:02:45 1.22 0.36 
n474 22:19:56 63:33:41 3.08 0.14 
n479 22:36:05 65:44:21 65.66 0.46 
NEWPS ID RA (°) δ (°) Speak 5GHz (Jy) σ (Jy) Candidate flag 
n1 00:03:38 68:28:50 1.24 0.11 
n22 00:52:56 56:35:22 2.59 0.26 
n157 06:14:21 61:28:32 1.17 0.35 
n365 16:57:46 48:08:32 0.71 0.35 
n432 20:19:36 46:03:05 21.82 0.34 
n440 20:52:47 55:11:44 2.05 0.78 
n448 21:13:23 59:21:51 0.79 0.32 
n449 21:17:36 60:02:45 1.22 0.36 
n474 22:19:56 63:33:41 3.08 0.14 
n479 22:36:05 65:44:21 65.66 0.46 

Five of the 10 mapped regions with δ≥ 45° were identified as candidate sources, but only three of them have (peak) S/N larger than 5. Fig. 10 shows a graphical elaboration of the map of n22, one of the five source detections. This object was identified with the H ii region NGC 0281. The recovered peak position of the five detected sources was then compared with that provided by WMAP: in all the cases the displacement does not exceed 10 arcmin.

Figure 10

Surface projection of the sky region centred on NEWPS source n22 identified with the H ii region NGC 0281.

Figure 10

Surface projection of the sky region centred on NEWPS source n22 identified with the H ii region NGC 0281.

Hence, among the 79 sources identified in the NEWPS sample with δ≥ 45°, about 95 per cent have been confirmed as genuine/candidate sources. A proper analysis of the comparison with the selection flux densities will be done in future works where we will present the 22-GHz data for our objects, for which the observing campaign is ongoing.

5.2 Spectral behaviour and comparisons with other catalogues

For each source, we have identified the best epoch of observation as the one with both 5- and 8.3-GHz observations. In case of multiple epochs with both frequencies we chose the one having higher S/N at both frequencies. We thus have a sample of 61 sources for which we estimated the spectral indices α8.35 (defined according to the flux density being ∝να). The median spectral index is −0.09 with a standard deviation of the distribution equal to 0.62 (see Fig. 12). This is compatible with the 5–10 GHz spectral index found for the PACO bright sample (the selection was based on 20-GHz flux densities >500 mJy).

Figure 12

Distribution of spectral indices in the 5-8 GHz frequency ranges.

Figure 12

Distribution of spectral indices in the 5-8 GHz frequency ranges.

33 sources have counterparts within the Planck ERCSC (The Collaboration 2011a). The median of the 5–30 GHz spectral index is −0.07 (see Fig. 13). As elsewhere stated (Massardi et al. 2008, 2009, Massardi et al. 2011b) the bright high-frequency-selected-samples are mostly constituted by flat spectrum sources in this frequency range (see also The Collaboration 2011c, d).

Figure 13

Distribution of spectral indices in the 5–30 (shaded area) and 30–70 GHz (hatched area) frequency ranges. The bin size is fixed at 0.5 for both the histograms. The displacement is due to the different ranges characterizing the two spectral indexes.

Figure 13

Distribution of spectral indices in the 5–30 (shaded area) and 30–70 GHz (hatched area) frequency ranges. The bin size is fixed at 0.5 for both the histograms. The displacement is due to the different ranges characterizing the two spectral indexes.

For this sample in the ERCSC, the 30–70 GHz spectral index is −0.16. As compared with the 100-GHz flux-density-limited sample in Sadler et al. (2008), the steepening is more pronounced for brighter samples.

We compared our sample flux densities with the 4.85 GHz GB6 catalogue (Gregory et al. 1996). 60 objects in the Northern sample have a counterpart in the GB6 catalogue (the remaining objects include the 10 sources for which we performed maps of the surrounding region and the objects in the region with δ > 75° that is not covered by the GB6 survey). The flux density comparison is shown in Fig. 14. Performing a linear fit of these data we found the following relation between the flux densities from SiMPlE and GB6:  

17
formula

Figure 14

Comparison of SiMPlE and GB6 5-GHz flux densities. The solid line shows the best linear fit and the dot–dashed lines enclose the area between the best fit plus and minus one standard deviation of the flux density ratio.

Figure 14

Comparison of SiMPlE and GB6 5-GHz flux densities. The solid line shows the best linear fit and the dot–dashed lines enclose the area between the best fit plus and minus one standard deviation of the flux density ratio.

For this wide subsample the rms of the fractional displacement is 43 per cent: since more than 14 years divide the two catalogues, this effect is probably entirely due to source variability. This is comparable with the 38 per cent variability found, at the same frequency on few years time-scales, on the PACO sample, confirming earlier indications that the variability increases with the time lag, for lags of up to several years. Our results seem to indicate that the asymptotical value for the source variability at 5 GHz is ∼43 per cent.

6 SUMMARY

In this work, we have described the sample selection, the observing strategy, the data reduction procedures and the software tools developed for the SiMPlE project. The selected sample includes 253 sources in the NEWPS sample and 10 candidate variable Galactic sources.

We have presented some tools that we developed to analyse data collected with the Medicina 32-m single dish. The tools allow us to efficiently schedule source lists, to visually inspect the scan quality, to compose and analyse maps of sky patches, and to calibrate and estimate the source flux densities.

The developed pipeline allowed us a fast and detailed automated analysis of our entire data set, and the whole software package can be easily adapted for analogous OTF-scan-based experiments.

As a result we have shown the results obtained for a subsample of 79 sources with δ≥ 45° observed in 22 runs in the 2010 June–December epoch, at 5 and 8.3 GHz. Data for two of them were flagged for bad weather conditions. For 10 targets we performed maps of the surrounding sky area confirming the detection in the WMAP maps for four of them. These results confirm that the NEWPS catalogue could be considered 95 per cent reliable.

The comparison with the ERCSC and the analysis of the spectral behaviour confirmed that bright sample sources are mostly composed by flat-spectrum objects up to 30 GHz, but show an overall steepening in the spectrum in the frequency range 30–70 GHz. The comparison of the 60 sources in common with the GB6 catalogue show an rms fractional displacement due to source variability of 43 per cent that is an indication of the long-term variability for bright sources on time-scales of more than 10 years.

In addition to the SiMPlE Northern sample, we also reported the observations for a list of 10 sources with δ < 0° chosen from the targets of the PACO project. The comparison of the flux densities obtained with the two instruments and the SEDs of these targets showed that the ATCA and the Medicina radio telescopes have a consistent flux density scale, despite the fact that the calibration and the data reduction follow independent methods. Larger samples are being observed simultaneously with the two telescopes to confirm this finding.

Observations for the SiMPlE experiment are continuing for the first semester of 2011 in order to overlap with at least two full surveys of the Planck satellite, in particular exploiting the commissioning phase of the 22-GHz multifeed receiver at the Medicina radio telescope. The SiMPlE sample might constitute a reference sample for this telescope and for ongoing Northern hemisphere surveys.

1
The Planck Early Results papers are publicly available at the following web address: http://www.sciops.esa.int/index.php?project=PLANCK&page=Planck_Published_Papers. The ERCSC Explanatory Supplement is also available at the same URL.
2
Information on the Planck scanning strategy and pointing are publicly available for external observers at http://www.sciops.esa.int/index.php?project=PLANCK\&page=Pointing.
3
The measured deviations of the beam shape from a circular Gaussian beam are less than 2 per cent, including the measured errors.
4
On a machine equipped with a 2.0-GHz Intel Core 2 Duo and 3 GB of RAM memory.
5
Performing an OTF cross-scan on a source takes approximately 30 s, including pre- and post-scan operations.

We acknowledge financial support for this research by ASI (ASI/INAF Agreement I/072/09/0 for the Planck LFI activity of Phase E2 and contract I/016/07/0 ‘COFIS’). Based on observations with the Medicina telescope operated by INAF – Istituto di Radioastronomia. We gratefully thank the staff at the Medicina radio telescope for the valuable support they provide. A particular acknowledgment goes to Andrea Orlati and Alessandro Orfei. We warmly thank Uwe Bach and Alex Kraus of the 100-m Effelsberg telescope of the Max Planck Institut für Radioastronomie who have provided important feedback on calibrator flux densities prior to publication. It is a pleasure to thank Gianfranco De Zotti, Luigina Feretti and Nazzareno Mandolesi for constructive and stimulating conversations.

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