bluuebunny/crossref_metadata_2025_split huggingface dataset:
Variable Red Giants in the LMC: Pulsating Stars and Binaries?
Authors: Wood P. R. 
Published: March 2011

AbstractInfrared J and K photometry has been obtained of all red giants in the half square degree region of the LMC bar searched for variables using the MACHO database byWood et al. (1999). The K–log P diagram shows the five distinct period–luminositysequences which are also evident in the MACHO photometry. The K–log P plot allowsidentification of the Mira sequence from among the five observed sequences. As shown in Wood et al. (1999), comparison of observed periods, luminosities and period ratios with theoretical models identifies Miras unambiguously as radial fundamental mode pulsators, while semi-regular variables can be pulsating in the first, second or third overtone, or even the fundamental mode. All these variables lie on just three of the five distinct sequences, and they all appear to be on the AGB. The nature of the variability of stars on the other two sequences is currently unknown. Possibilities include contact and semi-detached binaries, rotating stars with giant star spots, episodic dust formation, rotationally stabilised non-radial g− modes and strange pulsation modes caused by convection–pulsation interaction. These possibilities are discussed.
Compact Stellar Systems in the Fornax Cluster: Super-massive Star Clusters or Extremely Compact Dwarf Galaxies?
Authors: Drinkwater M. J. , Jones J. B. , Gregg M. D. , Phillipps S. 
Published: March 2011

AbstractWe describe a population of compact objects in the centre of the Fornax Cluster which were discovered as part of our 2dF Fornax Spectroscopic Survey. These objects have spectra typical of old stellar systems, but are unresolved on photographic sky survey plates. They have absolute magnitudes −13 < MB < −11, so they are 10 times more luminous than any Galactic globular clusters, but fainter than any known compact dwarf galaxies. These objects are all within 30 arcminutes of the central galaxy of the cluster, NGC 1399, but are distributed over larger radii than the globular cluster system of that galaxy. We suggest that these objects are either super-massive star clusters (intra-cluster globular clusters or tidally stripped nuclei of dwarf galaxies) or a new type of low-luminosity, compact elliptical dwarf (‘M32-type”) galaxy. The best way to test these hypotheses will be to obtain high-resolution imaging and high-dispersion spectroscopy to determine their structures and mass-to-light ratios. This will allow us to compare them to known compact objects and establish whether they represent a new class of hitherto unknown stellar system.
The Variable Ca II Absorption in β Pictoris during 1998
Authors: Barnes S. I. , Tobin William , Pollard K. R. 
Published: March 2011

AbstractVariable absorption features were observed in the visible and ultraviolet spectrum of β Pictoris soon after this star gained attention in the early 1980s due to its large IRAS infrared excess and the discovery, from optical imaging, of an edge-on dust disk. The absorption has been attributed to the evaporation of infalling planetesimals or comet-like bodies (the falling evaporating bodies, or FEB, hypothesis). With a view to confronting this hypothesis with fuller observations, we monitored the Ca II H and K lines in β Pictoris simultaneously during 1998, obtaining sequences of spectra on 50 nights. Variable absorption was usually present. The different oscillator strengths of the H and K lines permit the determination of covering factors, but detailed modelling is required to test whether all features can be explained by the FEB hypothesis. The blend of Ca II H with Balmer H ε means that the H and K photospheric profiles are different, and that the variable absorption features do not evolve in parallel. The behaviour of the variable absorption on November 27 is evocative of a body passing in front of the stellar disk in a prograde equatorial orbit.
Two-point Angular Autocorrelation Function and the Origin of the Highest-energy Cosmic Rays
Authors: Clay R. W. , Dawson B. R. , Kewley L. , Johnston-Hollitt M. 
Published: March 2011

AbstractConstruction of the Pierre Auger Observatory for the study of the highest-energy cosmic rays is about to begin. Prior to the availability of data from that experiment, decisions should be made on techniques for the analysis of the directional properties of those data. We examine here one possible analysis tool, the two-point angular autocorrelation function. As a concrete example, data from the SUGAR array are examined in this way. Possible clustering of the data is observed, and the identification of such clustering with candidate astronomical objects in a purpose-developed catalogue is investigated.
Infrared Astronomy: In the Heat of the Night The 1999 Ellery Lecture
Authors: Storey John W. V. 
Published: March 2011

AbstractInfrared astronomy has made remarkable progress over the past quarter century. This paper, which is a brief summary of the 1999 Ellery Lecture, outlines the importance of the infrared, traces some of the key Australian developments in the field, and looks ahead to the challenges facing infrared astronomers in the immediate future.
Comptonisation and Time-lags in Multi-temperature Plasmas Surrounding Compact Objects
Authors: Cullen Jason 
Published: March 2011

AbstractThis paper investigates a recent model proposed by Moskalenko, Collmar & Schönfelder (1998) for the plasma surrounding galactic black hole candidates. Using a linear Monte Carlo code, the spectral and temporal behaviour of the model is found for the case where the plasma geometry consists of a hot shell surrounding a cooler spherical core. The spectrum produced by this model at X-ray and gamma-ray energies is obtained numerically. Also found for the first time in this geometry are the photon time-lags between two energy bands due to rapid aperiodic variability. It is argued that the time-lag information may be able to determine whether this particular geometry is a realistic model for the material surrounding galactic black hole candidates.
The Optical/Near-IR Colours of Red Quasars
Authors: Francis Paul J. , Whiting Matthew T. , Webster Rachel L. 
Published: March 2011

AbstractWe present quasi-simultaneous multi-colour optical/near-IR photometry for 157 radio selected quasars, forming an unbiassed sub-sample of the Parkes Flat-Spectrum Sample. Data are also presented for 12 optically selected QSOs, drawn from the Large Bright QSO Survey. The spectral energy distributions of the radio- and optically-selected sources are quite different. The optically selected QSOs are all very similar: they have blue spectral energy distributions curving downwards at shorter wavelengths. Roughly 90% of the radio-selected quasars have roughly power-law spectral energy distributions, with slopes ranging from Fv∝v0 to Fv∝v−2. The remaining 10% have spectral energy distributions showing sharp peaks: these are radio galaxies and highly reddened quasars. Four radio sources were not detected down to magnitude limits of H ∼ 19·6. These are probably high redshift (z > 3) galaxies or quasars. We show that the colours of our red quasars lie close to the stellar locus in the optical: they will be hard to identify in surveys such as the Sloan Digital Sky Survey. If near-IR photometry is added, however, the red power-law sources can be clearly separated from the stellar locus: IR surveys such as 2MASS should be capable of finding these sources on the basis of their excess flux in the K-band.
Supernova Remnants, Pulsars and the Interstellar Medium
Authors: Dwarkadas Vikram , Ball Lewis , Caswell James , Green Anne , Johnston Simon , Schmidt Brian , Wardle Mark 
Published: March 2011

AbstractWe summarise the proceedings of a workshop on ‘Supernova Remnants, Pulsars and the Interstellar Medium’ which was held at the Special Research Centre for Theoretical Astrophysics at the University of Sydney on 18 and 19 March 1999.
Catalogue of J = 1−0 CO Emission towards Southern Dark Clouds
Authors: Otrupcek R. E. , Hartley M. , Wang J.-S. 
Published: March 2011

AbstractUsing the 22-m ‘Mopra’ antenna (near Coonabarabran, NSW) of the Australia Telescope National Facility (ATNF), we have observed emission from the 115-GHz J = 1−0 transition of CO towards the centre of each of the 1101 clouds listed in the Catalogue of Southern Dark Clouds (SDC) of Hartley et al. (1986). The velocity range covered was −96 to +70 km s−1, with a velocity resolution of 0· 120 km s−1. CO was detected at 1049 of the positions, with 367 spectra showing emission at more than one radial velocity. Here we present the most comprehensive general survey of the SDC catalogue, with the intensity, velocity and half-width of the CO detection and a code describing the profile shape. The presence of blue- or red-shifted wings in many observations can provide a starting point in searches for star-forming regions.
The Future of Robotic Telescopes for Education
Authors: Baruch J. E. F. 
Published: March 2011

AbstractThe development of robotic telescopes for education is reviewed. The problems associated with providing a service for students at different levels of education are discussed. Consideration is made of the hardware requirements in the students' institution and the compromises that are made to allow the maximum number of students to use facilities. The demands on teachers are considered along with the available methods of delivering educational projects related to curricular demands at the various stages. The likely developments in the technology are considered and estimates made of the probable timescales. Proposals are made to optimise student access to observing facilities that would involve the development of a linux-like collaboration around astronomy software and the development of low cost telescope systems. Proposals are made to realise such systems with the objective of providing universal access for students with Internet access.
The Universe on a Desktop: Observational Astronomy Simulations in the Instructional Laboratory
Authors: Marschall Laurence A. 
Published: March 2011

AbstractThough the value of hands-on learning has long been recognised by educators, it is difficult to design laboratories in astronomy classes that present realistic astrophysical techniques to undergraduate students. Unlike most other sciences, astronomy is largely observational, not experimental, and making useful observations involves expensive equipment over time scales inconvenient for pedagogy. In recent years, however, astronomy has gone almost completely digital, and the advent of large on-line databases and fast personal computers has made it possible to realistically simulate the experience of research astrophysics in the laboratory. Since 1992, Project CLEA (Contemporary Laboratory Experiences in Astronomy) has been developing computer-based exercises aimed primarily at the introductory astronomy laboratory. These exercises simulate important techniques of astronomical research using digital data and Windows-based software. Each of the nine exercises developed to date consists of software, technical guides for teachers, and student manuals for the exercises. CLEA software is used at many institutions in all the United States and over 60 countries worldwide, in a variety of settings from middle school to upper-class astronomy classes. The current design philosophy and goals of Project CLEA are discussed along with plans for future development.
Cosmology on the Internet: Distance Education for the Gifted and Talented
Authors: McKinnon David H. , Nolan C. J. Patrick 
Published: March 2011

AbstractIn 1994, the New South Wales Board of Studies, Australia, introduced three high level Distinction Courses for gifted and talented students: Comparative Literature, Cosmology, and Philosophy. All are offered by distance education but the cosmology course employs an interactive design model and an extensive communication system that differentiates it from the other two. This paper explains the model and the way it is used in practice to organise, sequence and deliver the course. A discussion addresses ways in which the model might be used to design a wider range of courses in science for gifted and talented students.
The Student as Scientist: Secondary Student Research Projects in Astronomy
Authors: Hollow R. P. 
Published: March 2011

AbstractStudent research projects are becoming either integral or optional components of Science curricula in several countries. They provide a valuable opportunity for high school students to experience many of the joys and frustrations that make up the intellectual challenge of Science. Astronomy is one branch of Science that lends itself to student projects. Student Research Projects (SRPs) can be individual, group or collaborative between groups in other schools or countries and may involve professional mentors. Use of the Internet and remote access telescopes allow students to undertake challenging research and make worthwhile contributions to professional programs. This paper presents case studies of student projects in optical and radio astronomy from Australian and overseas schools and details both the benefits and problems faced in conducting such projects. Student responses to involvement in projects are discussed. Potential areas for future collaboration and development are highlighted together with the need for more research as to the most effective ways to implement projects and develop student skills.
Campbelltown Rotary Observatory
Authors: Bhathal R. 
Published: March 2011

AbstractDonations (in cash and kind) amounting to $200,000 from companies in the south-western Sydney region have allowed the construction of a teaching, research and public access Observatory at the University of Western Sydney in Campbelltown. The Observatory will also serve as the home of the Australian Optical SETI Project (OZ OSETI for short). Two fibre-glass domes will be installed at the site. The main 4.5 m fibre-glass dome will house a 0.4 m telescope while the smaller 2.9 m dome will house a 0.3 m telescope. Both telescopes are fork-mounted Schmidt-Cassegrains working at f/10. An outside observation area will be used for tripod-mounted telescopes for public use and teaching purposes. The expected completion date for the project is July 2000.
Dark Matter and Galaxy Formation
Authors: Freeman K. C. 
Published: March 2011

AbstractIn addition to large numbers of normal galaxies, the multibeam HI Parkes all-sky survey will probably discover intergalactic HI clouds, very low-surface-brightness, gas-rich galaxies, and small HI clouds in nearby groups of galaxies. I will briefly discuss some aspects of why these classes of objects are interesting in the context of dark matter and galaxy formation.
The Galactic Halo Ionising Field
Authors: Bland-Hawthorn J. , Maloney P. R. 
Published: March 2011

AbstractThere has been much debate in recent decades as to what fraction of ionising photons from star-forming regions in the Galactic disk escape into the halo. The recent detection of the Magellanic Stream in optical line emission at the CTIO 4 m and the AAT 3·9 m telescopes may now provide the strongest evidence that at least some of the radiation escapes the disk completely. We present a simple model to demonstrate that, while the distance to the Magellanic Stream is uncertain, the observed emission measures (εm ≈ 0·5 – 1 cm−6 pc) are most plausibly explained by photoionisation due to hot, young stars. This model requires that the mean Lyman-limit opacity perpendicular to the disk is τLL ≈ 3, and the covering fraction of the resolved clouds is close to unity. Alternative sources (e.g. shock, halo, LMC or metagalactic radiation) contribute negligible ionising flux.
Ionised Hydrogen at Large Galactocentric Distances
Authors: Bland-Hawthorn J. 
Published: March 2011

AbstractWe summarise recent attempts to detect warm ionised gas at large galactocentric distances. This includes searches for gas at the edges of spirals, in between cluster galaxies, towards extragalactic HI clouds, and towards high-velocity clouds and the Magellanic Stream in the Galaxy. With the exception of extragalactic HI clouds, all of these experiments have proved successful. Within each class, we have only observed a handful of objects. It is premature to assess what fraction of the missing baryonic mass fraction might be in the form of ionised gas. But, in most cases, the detections provide a useful constraint on the ambient ionising flux, and, in the case of spiral edges, can even trace dark matter haloes out to radii beyond the reach of radio telescopes.
NGC 7421: Surfing the Intracluster Medium?
Authors: Ryder Stuart D. , Purcell G. , Davis D. , Andersen V. 
Published: March 2011

AbstractNGC 7421 is a barred spiral that is displaced from the centre of its optical envelope, and has a ‘bow-shock’-like western boundary, both suggestive of interaction with an intracluster medium. We have used five configurations of the ATCA to map the distribution and kinematics of HI in NGC 7421, and find supportive evidence for this scenario in the form of an HI ‘wake’. When compared with ROSAT PSPC observations of the diffuse hot gas in the surrounding group of galaxies, these new ATCA results will allow us to place new constraints on the density and dynamics of the intracluster medium.
New HI Observations of the prototype Polar Ring Galaxy NGC 4650A
Authors: Arnaboldi Magda 
Published: March 2011

AbstractNew, high-resolution observations of the HI emission line and 20 cm continuum at the Australia Telescope Compact Array (ATCA) for the prototype polar ring galaxy NGC 4650A are presented. They show the presence of a far more extended HI distribution than previously observed with the VLA, and a very regular velocity field out to a distance of ∼50 kpc. The combined analysis of the HI data with optical and near-infrared (NIR) images argues against previous warp models used to describe the dynamics of this object. Further analysis of the new B-band image obtained at the European Southern Observatories New Technology Telescope (NTT) indicates clearly that the polar structure extends continuously to within about 200 pc of the nucleus of the central host galaxy, ruling out the presence of a ‘hole’ in the central region of this component. The presence of two spiral arms stretching out in the polar disk seems to represent the most likely explanation for the observed morphology and kinematics.
Hazards and Future Improvements to HI Surveys
Authors: Fisher J. Richard 
Published: March 2011

AbstractMost radio astronomical observations are affected to some degree by man-made and natural interference. There are a few avoidance techniques that can reduce the impact of interference on the survey, but we must make quite significant advances in the understanding of our antennas and receivers and the interference itself before a substantial improvement can be expected. A major increase in the efficiency of future surveys will likely come from phased-array feeds, which have the potential for much closer beam spacings, greater antenna efficiency, and wider fields of view than current independent-feed arrays.
Grasping the Wispy Tendrils
Authors: Gooch Richard E. 
Published: March 2011

AbstractThe vast quantities of data produced by modern radio telescopes require advanced visualisation tools to explore them. The quantitative nature of astronomy requires more than just representing data visually. This paper discusses research in displaying, and using, a three-dimensional ‘cursor’ in amorphous, noisy data which often resemble wispy tendrils.
Blind HI Survey in the Centaurus and Fornax Clusters
Authors: Barnes David 
Published: March 2011

AbstractThe results of 21 cm HI survey observations are presented for two fields, centred on the Centaurus and Fornax southern galaxy clusters. One previously uncatalogued dwarf galaxy was detected near the southern edge of the Fornax cluster, and is visible on UKST survey plates. Implications for the Parkes Multibeam All Sky Survey are discussed.
An HI Selected Sample of Galaxies: The HI Mass Function and the Surface Brightness Distribution
Authors: Zwaan Martin , Briggs Frank , Sprayberry David 
Published: March 2011

AbstractResults from the Arecibo HI Strip Survey, an unbiased extragalactic HI survey, combined with optical and 21 cm follow-up observations, determine the HI mass function and the cosmological mass density of HI at the present epoch. Both are consistent with earlier estimates, computed for the population of optically selected galaxies. This consistency occurs because, although the distribution of optical central surface brightnesses among galaxies is flat, we fail to find a population of galaxies with central surface brightnesses fainter than 24 B-mag arcsec−2, even though there is no observational selection against them.
A Search for Radio-loud Supernovae
Authors: Sadler Elaine M. , Campbell-Wilson Duncan 
Published: March 2011

AbstractSome extragalactic supernovae, such as SN 1986J in NGC 891 (Rupen et al. 1987), are unusually strong radio sources. Their radio emission typically peaks a few years after the supernova explodes, and appears to arise from the interaction of the supernova shock with a dense stellar wind shed by the progenitor star. Since two radio-loud and possibly optically faint supernovae have recently been found serendipitously in nearby spiral galaxies, it is possible that such objects are common. If so, this would have important consequences for our understanding of both the chemical enrichment history of galaxies and the radio emission from starburst galaxies. Preliminary results from a survey of nearby spiral galaxies with the Molonglo Observatory Synthesis Telescope (MOST) allow us to make a first estimate of the radio supernova rate. A larger study now in progress will provide a much more sensitive measurement.
Alfvén Waves in Dusty Interstellar Clouds
Authors: Cramer N. F. , Vladimirov S. V. 
Published: March 2011

AbstractDust particles in a plasma can be higWy charged, and can carry a proportion of the negative charge of the plasma. Even if this proportion is quite small, as in interstellar dusty clouds, it can have a large effect on hydromagnetic Alfvén waves propagating at frequencies well below the ion–cyclotron frequency. In particular, the right-hand circularly polarised mode experiences a cutoff due to the presence of the dust. We generalise previous work on Alfvén waves in dusty interstellar plasmas by considering the general dispersion relation for waves propagating at an arbitrary angle with respect to the magnetic field. Wave energy propagating at oblique angles to the magnetic field in an increasing density gradient can be very efficiently damped by the Alfvén resonance absorption process in a dusty plasma, and we consider this damping mechanism for waves in interstellar clouds.
NIMPOL: An Imaging Polarimeter for the Mid-infrared
Authors: Smith Craig H. , Moore Toby J. T. , Aitken David K. , Fujiyoshi Takuya 
Published: March 2011

AbstractWe have built an imaging polarimeter for use at mid-infrared wavelengths (i.e. N band or 8–13 μm). The detecting element is a 128 × 128 element Si:Ga Focal Plane Array, supplied by Amber Engineering, USA. The polarimeter itself provides diffraction limited images on a 4-m class telescope and has a field of view of about 32 arcsec of sky with 0·25 arcsec pixels. We describe the optical design, control electronics, observing modes and detector sensitivities. Also presented are some observational results to demonstrate the power of this new imaging polarimetric system.