Driftscan methods are highly efficient, stable techniques for conducting extragalactic surveys in the 21 cm line of neutral hydrogen. Holding the telescope still while the beam scans the sky at the sidereal rate produces exceptionally stable spectral baselines, increased stability for RFI signals, and excellent diagnostic information about system performance. Data can be processed naturally and efficiently by grouping long sequences of spectra into an image format, thereby allowing thousands of individual spectra to be calibrated, inspected and manipulated as a single data structure with standard tools that already exist in astronomical software. The behaviour of spectral standing waves (multi-path effects) can be appraised and excised in this environment, making observations possible while the Sun is up. The method is illustrated with survey data from Arecibo and Nançay.

The NGVS is mapping the Virgo Cluster with a depth making possible to detect very low surface brightness (LSB) structures, such as faint dwarf galaxies. To extract these from just above the sky noise and make statistical studies of their properties, we use the software MARSIAA (MARkovian Software for Image Analysis in Astronomy). This segmentation software uses a Markovian approach to classify pixels and identify low-surface brightness structures.

By means of N-body simulations, we have investigated the impact of minor mergers on theangular momentum content and kinematical properties of a disc galaxy. Our simulationscover a range of initial orbital characteristics and the system consists of a massivegalaxy with a bulge and a stellar disc merging with a much less massive gasless companion.Our results show that: (1) during the process of merging, the disc of the primary galaxybecomes kinematically hotter and thicker; (2) its specific angular momentum alwaysdecreases, independent of the orbit or morphology of the satellite galaxy; (3) thedecrease in the rotation velocity of the primary galaxy is accompanied by a change in theanisotropy of the stellar orbits, which becomes increasingly radially dominated as themerger advances; (4) the radial velocity dispersion increases at all radii, but inparticular in the outermost regions; (5) at the same time, the transverse velocitydecreases throughout the whole disc, except in the inner region, where the constributionof bulge stars leads to an increase ofσt.

In this study we use numerical N-body/SPH simulations to investigate the vertical stellar distribution of thick disks formed in minor mergers. These disks have a sech-shape vertical surface density profile which needs two sech functions with different scale heights to fit due to an additional stellar excesses at large heights (z ≳ 4 − 5 kpc). The scale heights of merger-induced thick disks increase with radius but the details of this thickening are sensitive to orbital configurations and gas fraction of the galaxies. The scale height of the stellar excess is constant with radius and largely independent of the initial conditions. The effects of minor mergers is cumulative in the sense that several minor mergers have the same impact of a single minor merger of the same total mass. Scattering by self-gravitating masses (clumps) in unstable gaseous disks can produce thick disks with constant scale height, however, there is not a stellar excess at large scale heights. Most of these results are found to be in good agreement with observations and thus we conclude that minor mergers remains a viable mechanism for the creation of galactic thick disks.

The radio spectrum is a finite and increasingly precious resource for astronomical research, as well as for other spectrum users. Keeping the frequency bands used for radio astronomy as free as possible of unwanted Radio Frequency Interference (RFI) is crucial. The aim of spectrum management, one of the tools used towards achieving this goal, includes setting regulatory limits on RFI levels emitted by other spectrum users into the radio astronomy frequency bands. This involves discussions with regulatory bodies and other spectrum users at several levels – national, regional and worldwide. The global framework for spectrum management is set by the Radio Regulations of the International Telecommunication Union, which has defined that interference is detrimental to radio astronomy if it increases the uncertainty of a measurement by 10%. The Radio Regulations are revised every three to four years, a process in which four organisations representing the interests of the radio astronomical community in matters of spectrum management (IUCAF, CORF, CRAF and RAFCAP) participate actively. The current interests and activities of these four organisations range from preserving what has been achieved through regulatory measures, to looking far into the future of high frequency use and giant radio telescope use.

Nançay radio astronomy station teams are involved in several aspects of the Research and Development (R&D) for radio astronomy detectors and systems: i) Microelectronics: Low Noise Amplifiers (LNA), receiver on chip and system in package. The long-term goal is to provide sub-systems for the future Square Kilometer Array and its Pathfinders. A beamformer chip has been integrated in the FP6 SKADS dense aperture array technology demonstrator EMBRACE. Wide band SiGe LNAs are developed, beamformers with in-chip control are studied and more complex integrated receivers are designed for the european Aperture Array Verification Programme demonstrator. ii) Digital signal processing: EMBRACE beamforming has been implementedin the digital backend and RFI-mitigation oriented signal processing has been designed for realtime systems,including work for FP6 SKADS and FP7 PrepSKA. iii) A study of Phased Array Feeds has started in 2008, in order to study the radio electric properties of PAFs at the focus of large F/D telescopes, such as the Nançay Radio Telescope, as well as to test PAFsystems in collaboration with the SPP/IRFU and LAL/IN2P3 laboratories.

Reproduction errors have occured in figures 1–4 of this paper, published in these proceedings, pages 112–119. The complete corrected paper is reproduced here for clarity.

Cambridge University Press apologise to the authors and readers for these errors.

The Arecibo Galaxy Environment Survey is a blind neutral hydrogen survey using the ALFA multibeam receiver at Arecibo Observatory to reach unprecedented sensitivities in a number of selected fields in the local Universe. When completed the survey will cover 200 square degrees out to a distance of at least 270 Mpc. If a population of gas-rich dark galaxies exists, then this survey is in a prime position to uncover that population.

So far 20 square degrees have been covered in the regions of Abell 1367, the Virgo Cluster, the NGC 7332/9 galaxy pair and the isolated galaxy NGC 1156. Over 200 sources have been found, including a number that have no obvious optical counterparts. We discuss here the potential of AGES for uncovering more such objects and the characteristics of the dark sources identified to date.

The Arecibo Galaxy Environments Survey (AGES) is a 2000-hour neutral hydrogen (H I) survey using the new Arecibo L-band Feed Array (ALFA) multibeam instrument at Arecibo Observatory. It will cover 200 square degrees of sky, sampling a range of environments from the Local Void through to the Virgo Cluster with higher sensitivity, spatial resolution and velocity resolution than previous neutral hydrogen surveys.

We present Hα emission line velocity fields of two Low Surface Brightness galaxies (LSBs) - UGC 628 and UGC 5005 - obtained using Fabry-Perot (FP) interferometry observations at the Canada-France-Hawaii telescope. Our goal is to study the dynamics of LSBs.

A candidate Tidal Dwarf Galaxy, ce-61, was identified in the merger system IC 1182 in the Hercules supercluster. The multi-wavelength data we obtained so far do not prove, however, that it is kinematically detached from the IC 1182 system and gravitationally bound.

For astronomers, monitoring of the radio spectrum is an obvious necessity in order to do observations which are free of interfering signals. Recent practice has shown that the installation of dedicated RFI surveillance antennas at radio astronomy sites has virtually become a necessity. Data obtained with such antennas have carried significant weight in discussions with other radio spectrum users. Furthermore, the growing number of dedicated antennas for RFI surveillance at radio observatories has opened the possibility for the establishment of common RFI databases. Such databases can provide objective numbers showing the degradation of the effective use of protected frequencies due to interference, to be used by astronomers as well as by their partners in frequency protection. As it is all too easy to drown in such a sea of data, discussions between astronomers themselves and with their partners are clearly necessary to define the form, implementation and use of such databases.

We have observed a total of 74 polar ring galaxies (PRGs), PRG candidates and related objects at 3 radio observatories: Green Bank (Richter et al. 1994, AJ, 107, 1), Effelsberg (Huchtmeier 1997, A&A, 319, 401) and Nançay (van Driel et al. 1997, A&AS, in press; van Driel et al. 1998, A&A, in prep.). Our main aim is to identify systems suitable for HI synthesis mapping, crucial for an understanding of their dynamical state. Most objects were selected using one or more of the following 3 (<8000 km/s), or blue magnitude brighter than 15.5 mag, or kinematically confirmed PRG or good PRG candidate. A total of 62 objects were detected, 39 of which with more than one telescope.

The M81 group has great advantages for dwarf galaxy studies: it has about three times the dwarf content of the Local Group but is at only about a quarter of the Virgo cluster distance. We searched for HI in 23 optically selected dwarf members and possible members of the M81 group with the Nançay decimetric radio telescope in the velocity range of −529 to 1826 km s−1 with considerably better sensitivity (2–4 mJy rms.) than previous surveys. Half the objects observed are irregular dwarfs, expected to be HI-rich and detectable at Nançay if at the distance of the M81 group (4 Mpc).

UGC 7321 is an edge-on low surface brightness (LSB) spiral galaxy with a number of extraordinary properties. Its vertical scale height (~70 pc) is one of the smallest ever measured for a galaxy disk. Its disk also exhibits strong vertical and radial color gradients. UGC 7321 appears to be an extremely unevolved galaxy in both a dynamical and in a star-formation sense.

NGC 660 is a gas-rich, peculiar polar ring RSBa-type starburst galaxy with two distinct morphological and kinematic components: an inner disc, seen almost edge-on, with a major axis position angle of 45° and a diameter of ~11 kpc [D=13 Mpc, Ho=75 kms−1 Mpc−1], and an outer polar ring (p.a. 170°) with a diameter of 31 kpc, inclined on average about 55° with respect to the major axis of the inner disc.

We obtained deep, 30 min. exposure CCD images of NGC 660 with the 105 cm Schmidt telescope of Kiso Observatory in the B, V, R, and I bands. A preliminary reduction shows that the inner disc is clearly redder than the polar ring and the nucleus.

Optical spectra indicate that the galaxy has a LINER-type spectrum, suggesting intense massive star formation in the nucleus. We obtained a long-slit Ha spectrum along the major axis of the inner disc at ESO, which shows a very steep gradient near the nucleus. Assuming an inclination of 80°, it implies a rotational velocity of about 150 km s−1 for the inner disc.