Distant star forming galaxies, next generation radio telescopes and the radio universe before re-ionisation

I present the various capabilities of upgraded and next generation radio telescopes, in particular their ability to detect and image distant star forming galaxies. I demonstrate that e-MERLIN, EVLA and LOFAR can detect systems similar to Arp 220 out to cosmological distances. The SKA can detect such systems out to any reasonable redshift that they might be expected to exist. Employing very long integration times on the multiple-beam SKA will require the array to be extended beyond the current specification - simply to avoid confusion noise limitations at 1.4 GHz. Other arguements for extending the SKA baseline length are also presented. As well as going ``deeper'' all these instruments (especially LOFAR and the SKA) will also go ``wider'' - detecting many tens of thousands of galaxies in a single day's observing. I briefly comment on the prospects of detecting radio emission at much earlier epochs, just before the epoch of re-ionisation.Comment: Proceedings of the 6th European VLBI Network Symposium, Ros, E., Porcas, R.W., Lobanov, A.P., & Zensus, J.A. (eds.), MPIfR, Bonn, Germany (2002). 4 pages, 5 figure

Radio Astronomy Transformed: Aperture Arrays - Past, Present & Future

I review the early development of Aperture Arrays and their role in radio astronomy. The demise of this technology at the end of the 1960's, and the reasons for the rise of parabolic dishes is also considered. The parallels with the Antikythera mechanism (see these proceedings) as a lost technology are briefly presented. Aperture Arrays re-entered the world of radio astronomy as the idea to build a huge radio telescope with a collecting area of one square kilometre (the Square Kilometre Array, SKA) arose. Huge ICT technology advances had transformed Aperture Arrays in terms of their capability, flexibility and reliability. In the mid-1990s, ASTRON started to develop and experiment with the first high frequency aperture array tiles for radio astronomy - AAD, OSMA, THEA & EMBRACE. In the slipstream of these efforts, Phased Array Feeds (PAFs) for radio astronomy were invented and LOFAR itself emerged as a next generation telescope and a major pathfinder for the SKA. Meanwhile, the same advantages that aperture arrays offered to radio astronomy had already made dishes obsolete in many different civilian and military applications. The first commissioning results from LOFAR and other Aperture Arrays (MWA, LWA and PAPER) currently demonstrate that this kind of technology can transform radio astronomy over 2 decades of the radio spectrum, and at frequencies up to at least 1.5 GHz. This "reinvention of radio astronomy" has important implications for the design and form of the full SKA. Building a SKA that is simply the "VLA on steroids" is simply not good enough. Like the Antikythera mechanism itself, we must amaze future generations of astronomers - they and the current generation deserve nothing less.Comment: 9 pages, Paper presented at "From Antikythera to the Square Kilometre Array: Lessons from the Ancients, Kerastari, Greece 12-15 June 2012" eds. A.K. Tzioumis et al; Proceedings of Science, 2012, http://pos.sissa.it/cgi-bin/reader/conf.cgi?confid=17

Deep Fields: The Faint sub-mJy and microJy Radio Sky - A VLBI Perspective

Until recently, VLBI targets have been drawn almost exclusively from the brightest and most compact radio sources in the sky, with typical flux densities well in excess of a few tens of mJy. These sources are predominantly identified with Active Galactic Nuclei (AGN), located at cosmological distances. In this lecture I will attempt to summarise what is currently known about the general properties of the faint sub-mJy and microJy radio source population, as determined from deep multi-wavelength studies of the HDF-N. In particular, I will try to provide a VLBI perspective, describing the first deep, wide-field, VLBI pilot observations of the HDF, together with a summary of the main results. The role VLBI can play in future high resolution studies of faint radio sources is also addressed.Comment: 11 pages, 8 figures. To appear in "The Role of VLBI in Astrophysics, Astrometry and Geodesy", NATO ASI VLBI 2001 School, editor: F. Mantovan

Clifford Geometrodynamics

Classical anti-commuting spinor fields and their dynamics are derived from the geometry of the Clifford bundle over spacetime via the BRST formulation. In conjunction with Kaluza-Klein theory, this results in a geometric description of all the fields and dynamics of the standard model coupled to gravity and provides the starting point for a new approach to quantum gravity.Comment: 4 pages, no figures. Corrected and included |e| suggested by a reade

Hanny's Voorwerp and the Antikythera Mechanism - similarities, differences and insights

I present some insights into Hanny's Voorwerp and the Antikythera mechanism - contrasting their similarities and differences. They are both excellent examples of serendipitous discoveries in which human curiosity and perseverance have played an important role. Both objects have captured the imagination of the general public, and their discovery was only made possible via the introduction of new technologies. One major difference is that there is only one Antikythera device but there are now many Voorwerpen or "voorwerpjes", as they are more commonly known. The study of a collection of objects, as is common in astronomy, greatly aids our understanding of cosmic phenomena. In the case of the voorwepjes, we now know that such systems are to be identified with obscured galaxies or Active Galactic Nuclei (AGN) that appear to have recently and indeed rapidly turned off. Clearly, the discovery of more examples of devices similar to the Antikythera mechanism would have a significant affect in advancing our understanding of this object and the people that constructed it. Thus far, surveys of the site of the Antikythera wreck are incomplete and non-systematic. Like radio astronomy and other progressive fields, technological advances proceed exponentially in terms of capacity and capability. Recent advances in diving technology are no exception to this rule. It is almost 40 years ago that Jacques Cousteau led the last adhoc survey of the Antikythera wreck - the time has surely come to revisit the site and conduct a proper scientific and systematic survey. The deepest areas of the site are so far completely unexplored while it is known that some artefacts did fall into this area during the original excavation. During this workshop, I called for a return to the site using the most modern diving technologies.Comment: 8 pages, 5 figures. Paper presented at "From Antikythera to the Square Kilometre Array: Lessons from the Ancients, Kerastari, Greece 12-15 June 2012" eds. A.K. Tzioumis et al; Proceedings of Science, 2012, http://pos.sissa.it/cgi-bin/reader/conf.cgi?confid=17

SETI surveys of the nearby and distant universe employing wide-field radio interferometry techniques

Long baseline radio interferometers can provide some interesting opportunities for future SETI searches. Known advantages (compared to single dishes or beam-formed arrays), include the large reduction in false-positives due to the interferometer's natural suppression of RFI. This paper presents other advantages - the presence of multiple interferometer baselines in an array provide an important level of redundancy and additional confidence (verification) in the detection of faint and potentially transient signals. The SETI requirement for high time and frequency resolution is well matched to wide-field VLBI techniques that permits the simultaneous analysis of thousands of potential SETI targets within the field-of-view. Searching for a SETI signal in the image plane has the important advantage that the signal location on the sky is likely to be invariant on short timescales - this is a useful constraint when potentially almost everything else could be changing (eg frequency drift due to Doppler accelerations). Using archive data, we demonstrate how VLBI can be used to conduct SETI searches. We target two targets within the field of view - a galactic star and a galaxy at a redshift of 0.14. We place coarse upper limits on any SETI signals from the two SETI targets, and note that while the EIRP associated with the galaxy is comparable to the energy resources of a Kardashev Type 2 civilisation, a distributed array of coherent transmitters with excellent forward gain, could reduce this to more modest levels. We therefore argue that targeted observations of extragalactic sources may also be merited by interferometer surveys. Using VLBI to study the precise location and motion of confirmed SETI signals is also discussed.Comment: 5 pages, 5 figures. Presentation presented at IAC 2018 Session SETI 1 and EVN Symposium 201

e-VLBI... a Wide-field Imaging Instrument with milliarcsecond Resolution & microJy Sensitivity

The European VLBI Network (EVN) is in the process of establishing an e-VLBI array in which the radio telescopes and the EVN correlator at JIVE are connected in real-time, via high-speed national fibre optic networks and the pan-European research network, GEANT. This paper reports on recent test results, including the production of the first real-time e-VLBI astronomical image. In a parallel and related development, the field-of-view of VLBI is also expanding by many orders of magnitude, and the first results of deep, wide-field surveys capable of detecting many sources simultaneously are summarised. The detection of sources as faint as 10 microJy should soon be possible in the era of ``Mk5'' and e-VLBI.Comment: 4 pages, 3 figures. Paper presented in a conference held in Berlin "Exploring the Cosmic Frontier: Astrophysical Instruments for the 21st Century", May 2004 proceedings to be published in the Springer-Verlag series "ESO Astrophysics Symposia

The FIR/Radio correlation of high redshift glaxies in the region of the HDF-N

The correlation between the far-infrared (FIR) and radio emission is well established for nearby star forming galaxies. Many applications, in particular the radio-to-submm spectral index redshift indicator, tacitly assume that the relation holds well beyond our local neighbourhood, to systems located at cosmological distances. In order to test this assumption I have constructed a sample of 22 HDF-N galaxies, all with measured spectroscopic redshifts, and all detected by both ISO and the WSRT at 15 micron and 1.4 GHz respectively. The galaxies span a wide range of redshift with a median value of z ~ 0.7. The ISO 15 micron data were k-corrected and extrapolated to the FIR (60 and 100 micron) by assuming a starburst (M82) spectral energy distribution (SED) for the entire sample. An initial analysis of the data suggests that the correlation between the FIR and the radio emission continues to apply at high redshift with no obvious indication that it fails to apply beyond z ~ 1.3. The sample is ``contaminated'' by at least 1 distant (z=4.4), radio-loud AGN, VLA J123642+621331. This source has recently been detected by the first deep field VLBI observations of the HDF-N and is clearly identified as an ``outlier'' in the FIR/radio correlation. I briefly comment on the impact upgraded and next generation radio instruments (such as e-MERLIN and the Square Km Array) can have in studies of star formation in the early Universe.Comment: 6 pages, 4 figures (better figures at http://www.jive.nl/~mag/fir-radio.html) To appear in "The central kpc of starbursts and AGN: the La Palma connection", Eds. J.H. Knapen, J.E. Beckman, I. Shlosman and T.J. Mahoney, ASP conf. series, in press (2001

A New Strategy for the Routine Detection & Imaging of Faint Radio Sources with VLBI

In this paper I outline a new strategy for the routine detection and imaging of faint (sub-mJy and microJy) radio sources with VLBI and SVLBI. The strategy relies on a combination of in-beam phase-referencing, wide-field VLBI imaging and simultaneous correlation of multiple field centres. A combination of these techniques, together with the steeply rising radio source counts observed at cm wavelengths, permit routine high resolution observations of radio sources previously considered too faint for conventional VLBI.Comment: 4 pages, 1 figure. VSOP Symposium (ISAS, Tokyo 2000) proceedings will be published as "Astrophysical Phenomena Revealed by Space VLBI" eds. H. Hirabayashi, P.G. Edwards and D.W. Murphy. See http://www.jive.nl/~mag/deep.html for more details and better figur

When you wish upon a star: Future developments in astronomical VLBI

In this paper, I present the likely technological development of VLBI, and its impact on the astronomical community over the next 1-5 years. VLBI is currently poised to take advantage of the rapid development in commercial off-the-shelf (COTS) PC-based products. The imminent deployment of disk-based recording systems will enable Gbps data rates to be achieved routinely by both cm and mm-VLBI networks. This, together with anticipated improvements in collecting area, receiver systems and coherence time is set to transform the performance of VLBI in terms of both baseline and image noise sensitivity. At the same time the feasibility of using fibre based communication networks as the basis for production, real-time VLBI networks will begin. Fantastic new correlator output data rates, and the ability to deal with these via powerful PC clusters promises to expand the typical VLBI field-of-view to scales previously reserved for connected, short baseline interferometers. By simultaneously sampling the summed response of all compact radio sources within (and indeed beyond) the half-power point of the VLBI telescope primary beam, simple self-calibration of the target field will ALWAYS be possible at frequencies below a few GHz. Unbiased, broad-band continuum surveys will be conducted over huge areas of sky, and (redshifted) spectral-features will be detected too. By the end of the decade the microJy radio sky will be accessible to VLBI: dozens of sources will be simultaneosuly observed, correlated, detected and fully analysed all within the same day.Comment: 17 pages, 9 figures, To appear in ASP Conf. series - "New Technologies for VLBI", ed. Y.C. Minh (Korean VLBI Network