The LBA Calibrator Survey of southern compact extragalactic radio sources - LCS1

Abstract

We present a catalogue of accurate positions and correlated flux densities for 410 flat‐spectrum, compact extragalactic radio sources previously detected in the Australia Telescope 20 GHz (AT20G) survey. The catalogue spans the declination range [−90°, −40°] and was constructed from four 24‐h very long baseline interferometry (VLBI) observing sessions with the Australian Long Baseline Array at 8.3 GHz. The VLBI detection rate in these experiments is 97 per cent, the median uncertainty of the source positions is 2.6 mas and the median correlated flux density on projected baselines longer than 1000 km is 0.14 Jy. The goals of this work are (1) to provide a pool of southern sources with positions accurate to a few milliarcsec, which can be used for phase‐referencing observations, geodetic VLBI and space navigation; (2) to extend the complete flux‐limited sample of compact extragalactic sources to the Southern hemisphere; and (3) to investigate the parsec‐scale properties of high‐frequency selected sources from the AT20G survey. As a result of this VLBI campaign, the number of compact radio sources south of declination −40° which have measured VLBI correlated flux densities and positions known to milliarcsec accuracy has increased by a factor of 3.5. The catalogue and supporting material is available at http://astrogeo.org/lcs1.

First Geodetic Observations Using New VLBI Stations ASKAP-29 and WARK12M

“…Our attempt to use maps of the total electron content (TEC) from GPS using the data product from the analysis center CODE did not improve the fit and shifted estimates of station coordinates at a fraction of the formal uncertainty (0.2s). Analysis of dual-band VLBI experiments showed that global TEC maps above Australia and New Zealand provided by the International Global Navigation Satellite System Service are not reliable, and the path delay computed from this model poorly represents the true delay in the ionosphere, at least during solar minimum (Petrov et al 2011a).…”

“…The experiment was scheduled using sur_sked software in the VLBI geodetic mode. A pool of 113 sources with correlated flux densities at X-band greater than 700 mJy based on results of the ongoing LBA Calibrator Survey (Petrov et al 2011a) observing campaign was …”

FIRST PARALLAX MEASUREMENTS TOWARD A 6.7 GHz METHANOL MASER WITH THE AUSTRALIAN LONG BASELINE ARRAY—DISTANCE TO G 339.884−1.259.

“…J 1654-4812 was observed in all epochs except 2012 March and showed variable source structure which made it unsuitable for parallax determination. J 1706-4600 has a positional accuracy of 2.10 mas (Petrov et al 2011) and shows deviation from point-like structure at levels <10% of the peak flux density (Figure 3). J 1654-4812 had an estimated positional accuracy of 0″ .…”

“…In order to achieve accurate phase referenced astrometry, suitable background quasars had to fulfill the criteria that they have little or no extended structure, their coordinates be known to an uncertainty of <1 mas and that they are in close angular proximity to the associated maser of ∼1° (Reid et al 2009a). The primary databases that were used in our search for quasars were the AT20G (Hancock et al 2011), Astrogeo (Petrov et al 2011);and ATPMN (McConnell et al 2012) catalogues. A list of potential background quasars which were observed in conjunction with G 339.884-1.259 is given in Table 2.…”

Vlbi Measurement of Weak Sources With Improved Sensitivity

“…These sources are used as reference or calibrating sources in differential astrometry, space geodesy and deep space navigation. The cumulative all-sky catalogue of calibrator sources 1 called rfc2014a has 6867 objects with X band information obtained from numerous VLBI surveys (Beasley et al, 2002;Petrov et al, 2008;Petrov et al, 2011).…”