bluuebunny/crossref_metadata_2025 huggingface dataset:
How Children Observe the Universe
Authors: Dunlop John
Published: March 2011

Children who visited Auckland Observatory and Stardome Planetarium in 1998 were surveyed on their ideas about the Earth, the Moon and the Sun. Widespread misconceptions similar to those found in other studies were revealed, however the single teaching session had an impact on children's ideas comparable to that of much longer interventions. Several ideas not reported previously were expressed. For example, two children drew a figure eight orbit for the Earth; circling the Sun during the day, and the Moon at night. Only one child of the 67 surveyed proposed the notion of day and night being caused by the Sun orbiting the Earth. This is in contrast to many other studies. A drawing based pre-post survey proved to be a convenient and powerful tool for revealing changing patterns in children's thinking. The literature surveyed indicated levels of misconceptions about astronomy among teachers and other adults that were nearly as great as those of the children being taught. It would seem a strategic move to provide teachers with sufficient training if they are required to teach astronomy at every level, as has happened with the New Zealand science curriculum. A comparison between different question types suggests that multiple-choice questions may underestimate the knowledge of younger children by over 300% when compared with interview responses. A drawing based question in this study generated up to 41% more correct responses than a multiple-choice question on the same topic.
TTF Survey of Galaxy Populations
Authors: Jones Heath , Bland-Hawthorn Joss
Published: March 2011

The TAURUS Tunable Filter (TTF) affords a new approach to observational cosmology, allowing a wide field (10 arcmin) to be imaged monochromatically in contiguous wavelength intervals (6–60 Å bandpass) over the R and I bands. In a 200 s exposure with the AAT, the TTF can detect Hα emission powered by star formation rates as low as 0·1 M⊙ yr−1 at z = 0·08 and 1 M⊙ yr−1 at z = 0·24 in 2 arcsec seeing (cf. 0·26 M⊙ yr−1 for the LMC). In this paper we describe an emission-line survey currently under way using the TTF on the AAT to detect redshifted Hα over the ranges z = 0·06–0·1 and z = 0·22–0·26. Such detections will be of timely interest to the Southern HI Sky Survey which is motivated along similar lines.
Structure of Dark Halos: Model-independent Information from HI Rotation Curves
Authors: Sackett Penny D.
Published: March 2011

Although the approximately flat rotation curves of gas in the outskirts of spirals are generally taken as strong evidence for spherical, isothermal dark matter halos, this conclusion is often incorrect and always model-dependent. A re-examination of the old and (nearly) model-independent inversion technique for determining the surface mass density of galaxies from their kinematics is presented. The method is shown to be relatively insensitive to noise in the kinematics. Due to incomplete kinematical knowledge at large radius, however, the surface mass density is reliable only in the inner half of the galaxy, a result that also applies to traditional rotation curve fitting techniques.
Driftscan Surveys in the 21 cm Line with the Arecibo and Nançay Telescopes
Authors: Briggs F. H. , Sorar E. , Kraan-Korteweg R. C. , van Driel W.
Published: March 2011

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.
HI in Elliptical Galaxies
Authors: Sadler Elaine M.
Published: March 2011

Traditional HI surveys of optically selected elliptical galaxies are time-consuming, and have a low detection rate. The forthcoming Parkes HI multibeam survey offers the exciting possibility of surveying more than 10,000 nearby elliptical galaxies for HI. I argue that this is likely to result in the detection of a large population of small, HI-rich elliptical galaxies which have not previously been studied in any systematic way.
HI Observations of Compact Groups of Galaxies
Authors: Oosterloo Tom , Iovino Angela
Published: March 2011

We present preliminary results from HI observations of a new sample of compact groups done with the Parkes telescope, as well as from images made with the Australia Telescope Compact Array (ATCA). These observations confirm earlier claims that a significant fraction of compact groups are deficient in HI, and hence that a significant fraction of groups of galaxies that appear compact on the sky are indeed compact systems. The ATCA observations of a very HI-poor group suggest that this group is a true compact system in an advanced stage of evolution. However, the ATCA observations also show that HI-rich groups exist that are genuinely compact.
21 cm Searches for Dim Galaxies
Authors: Disney Mike , Banks Gareth
Published: March 2011

We review very strong selection effects which operate against the detection of dim (i.e. low surface brightness) galaxies. The Parkes multibeam instrument offers a wonderful opportunity to turn up new populations of such galaxies. However, to explore the newly accessible parameter space, it will be necessary to survey both a very deep patch (105 s/pointing, limiting Nhi ∼ 1018 cm−2) and a deep patch (104 s/pointing, limiting Nhi ∼ 3 × 1018 cm−2) in carefully selected areas, and we outline the case to do this.
The Dark Blue Compact Dwarf Galaxy NGC 2915
Authors: Meurer Gerhardt R.
Published: March 2011

Recent results on NGC 2915, the first blue compact dwarf galaxy to have its mass distribution modelled, are summarised. NGC 2915 is shown to have HI well beyond its detected optical extent. Its rotation curve is well determined and fit with maximum disk mass models. The dark matter halo dominates the mass distribution at nearly all radii, and has a very dense core compared to those of normal galaxies. High-mass star formation energises the HI in the centre of the galaxy, but appears to be maintained in viriai equilibrium with the dark matter halo. The implications of these results are briefly discussed.
The HI-rich Elliptical Galaxy NGC 5266: An Old Merger Remnant?
Authors: Morganti R. , Sadler E. M. , Oosterloo T. A. , Pizzella A. , Bertola F.
Published: March 2011

We present HI images for the dust-lane elliptical galaxy NGC 5266. This galaxy contains more than 1010M☉ of HI and our data show that the neutral hydrogen extends to ∼8 arcmin each side of the nucleus, or eight times the optical half-light radius Re. Surprisingly, the outer HI gas extends almost orthogonally to the optical dust lane. The overall HI kinematics can be successfully modelled by assuming that the gas hes in two orthogonal planes—in the plane of the dust lane in the central parts and perpendicular to this in the outer regions. The large amount of neutral gas observed and the HI morphology suggest that this object may have formed from the merger of two gas rich spiral galaxies. If so, it probably represents a relatively old merger remnant since most of the HI appears settled. The mass-to-light ratio has also been derived, with evidence for a dark matter halo around this galaxy.
The HI Luminosity Function from ‘Blind’ Surveys
Authors: Schneider Stephen E.
Published: March 2011

Recent neutral hydrogen (HI) surveys have detected enough sources to make initial predictions of the extragalactic HI luminosity function. These surveys provide useful pointers for the Parkes Multibeam Survey, highlighting various advantages and disadvantages of different observing and analysis procedures. The newest surveys are also large enough to permit some statistical tests of their completeness. The detection rates clearly fall short of what would be expected based on a simple propagation of errors, suggesting the need for further development of detection software. I suggest several procedures for determining the effective sensitivity of HI surveys. Applied to two recent Arecibo surveys, these suggest that the HI luminosity function may be much steeper than its optical counterpart, and that the Parkes surveys may detect a large number of low-mass sources.
Galactic HI Mapping and Optical–IR Studies
Authors: Davies R. D.
Published: March 2011

HI structure is seen at every scale down to the angular resolution limit of all survey telescopes. I present several examples of the structures at high Galactic latitudes with the 12 arcmin beam of the Loveli Telescope, the 2 arcmin resolution of the DRAO synthesis, as well as other indicators of finer scale structure in the interstellar medium (ISM).
An HI Mosaic of the Large Magellanic Cloud
Authors: Kim Sungeun , Freeman K. C. , Staveley-Smith L. , Sault R. J. , Kesteven M. J. , McConnell D.
Published: March 2011

The parameters of a new Australia Telescope Compact Array (ATCA) mosaic of the Large Magellanic Cloud (LMC) in the 21-cm line of neutral hydrogen are described. A preliminary peak-brightness-temperature image of the whole of the LMC, and a detailed image of the region around the supergiant shells LMC 4 and 5 is shown.
Star Formation and Gas Distribution in the Magellanic Spiral NGC 4214
Authors: McIntyre V. J.
Published: March 2011

I present new high-resolution observations of the HI in NGC 4214 made as part of a study of the small-scale kinematics and star formation regions of the galaxy.
The FLAIR–DENIS Redshift Survey
Authors: Parker Q. A. , Colless M. , Mamon G.
Published: March 2011

The DEep Near-Infrared Survey of the southern sky (DENIS) will produce an important by-product: a clean, complete view of the local Universe to z ∼ 0·07 for 105 galaxies. We identify the FLAIR multi-fibre system on the UKST as an extremely competitive facility to undertake follow-up spectroscopy for this sample due to the need to cover wide areas of sky and observe thousands of objects to a relatively bright (B < 17·5) magnitude.
12CO J = 1 → 0 Observations of the Circinus Galaxy using the Mopra 22 m Radio Telescope
Authors: Elmouttie M. , Haynes R. F. , Jones K. L.
Published: March 2011

The J = 1–0 rotational transition of carbon monoxide has been used to trace the molecular gas at five different positions in the Circinus galaxy using the Australia Telescope National Facility's 22 m radio telescope at Mopra. The intensity profile of the central CO emission has a full width at half maximum of 550 pc. The 12CO (1–0) spectrum at the centre of the galaxy has an integrated temperature of 145 K km S−1, with components peaking at 0·62 K and ranging in velocity from 200–600 km S−1. The total mass of molecular gas in the Circinus galaxy, assuming that the CO intensity profile of the galaxy is similar to the radio continuum, is at least 7·5±4·1 × 108 M⊙. This estimate, combined with previously published far infrared data, yields a value for the star-forming efficiency, SFE = 16±9 L⊙ M⊙‒1.
The Nature of Boxy/Peanut Spiral Galaxies: Overview and New Results
Authors: Bureau M. , Freeman K. C.
Published: March 2011

The formation mechanism of boxy/peanut-shaped bulges in spiral galaxies has been a problem for many years. We briefly review here the possible formation scenarios for boxy/peanut bulges, concentrating on both the bar-buckling and accretion hypotheses, and then describe an observational program aimed at testing those various theories and studying the vertical structure of edge-on bars. Our program includes optical long-slit spectroscopy, Hiline-imaging, near-infrared imaging, and multi-band optical imaging. New spectroscopic results (both optical and Hi) are presented on seven galaxies, including five boxy/peanut-bulge spirals. Based on Kuijken & Merrifield's (1995) idea for detecting edge-on bars, we argue that these observations constitute a strong case in favour of the bar-buckling mechanism for the formation of boxy/peanut-shaped bulges, but they also raise many questions and prompt for more detailed modelling to be made. The implications of the observations concerning the determination of rotation curves and of the physical conditions in bulges are also discussed.
Optical Identification Strategies for the Molonglo Cluster Survey
Authors: Haigh A. J. , Robertson J. G. , Hunstead R. W.
Published: March 2011

We describe a newly refined procedure for making optical identifications of radio sources in Abell cluster fields observed with the Molonglo Observatory Synthesis Telescope (MOST). The method is based on past experience but uses a range of new tools to improve the reliability and production rate of identification lists. The COSMOS/UKST Southern Sky Object Catalogue was used to make preliminary identifications which were then inspected visually with the assistance of computer generated overlays of the MOST images and the Digitized Sky Survey (DSS). The overlaid images were essential for securing identifications for the extended sources prevalent among nearby clusters.

We find 21±1·5% of the radio sources are identified with galaxies and 4·6±0·7% with QSO candidates in a sample of 927 radio sources in 27 cluster fields. We make a preliminary attempt to separate cluster radio galaxies from interlopers on the basis of absolute magnitudes. A strong concentration of radio galaxies was found at projected distances less than 100 kpc from the cluster centres and a weaker concentration for projected distances of 100–500 kpc.
Effect of Synchrotron Losses on Multiple Diffusive Shock Acceleration
Authors: Melrose Don , Crouch Ashley
Published: March 2011

The effect of synchrotron losses on diffusive shock acceleration (DSA) at many shocks is treated numerically. Synchrotron losses determine a maximum energy to which electrons can be accelerated through DSA, and this is referred to as the synchrotron cutoff, pc. The distribution of accelerated electrons after many shocks is found (a) for a distribution injected at the initial shock, to tend to a plateau [f(p) independent of p ≲ 0·1pc], and (b) for the cumulative distribution from injection at each shock to tend to f(p) ∝ p–b with b ≈ 3 well below the synchrotron cutoff with a peak in the slope (bmin ≈ 2) at p ≲ 0·1pc. It is suggested that the latter result might account for the flat synchrotron spectra observed in some Galactic Centre sources.
Response of the Molonglo Observatory Synthesis Telescope to Terrestrial Interference
Authors: Campbell-Wilson D. , Davidson G. , Large M. I.
Published: March 2011

In conjunction with the Australian Government's Spectrum Management Agency, experimental tests have been carried out to determine the susceptibility of the Molonglo Observatory Synthesis Telescope (MOST) to interference from terrestrial transmitters. The motivation for the tests was to reconcile the conflicting requirements of the MOST, which is committed to an extensive survey of the southern sky at 843 MHz, with the commercial use of the 825–845 MHz band, which is being prepared for sale. The tests show that the far sidelobe gain of the MOST, relative to an isotropic antenna is generally less than 1, and that an appropriate interference criterion would be that in-band interference irradiance should not exceed −173 dBWm−2. This value is similar to that considered by the International Telecommunications Union to be detrimental to radio astronomy continuum observations at nearby frequencies.
Scientific Background to the UKST Hα Survey
Authors: Masheder M. R. W. , Phillipps S. , Parker Q. A.
Published: March 2011

The dominant process in the evolution of spiral galaxies like our own is clearly the formation of new stars, and the leading optical indicator of this is Hα emission. Considering the tremendous importance of star formation and its variation within and between galaxies, it is surprising just how little survey work has been carried out at Hα. After the successful development of Tech Pan films for deep photographic imaging with the UKST, and given the particular sensitivity of Tech Pan at wavelengths near Hα, it was natural to consider the possibilities for a narrowband Hα imaging survey of large angular extent. This idea quickly developed into a full-blown survey of the whole of the Southern Milky Way, of the Magellanic Clouds, and of selected extragalactic regions of interest such as that around the Virgo Cluster. This special issue is devoted to the discussion of the details of making and using this survey.
Technical Aspects of the New AAO/UKST Hα Interference Filter
Authors: Parker Quentin A. , Bland-Hawthorn Joss
Published: March 2011

We briefly describe technical aspects and specifications of the new UKST Hα interference filter, which is probably the largest of its kind available in astronomy. Preliminary exposures show that the filter gives excellent imaging with high overall transmission and uniformity at Hα wavelengths. This is achieved over a circular area of about 305 mm diameter or about 5·7 degrees (the so called ‘clear aperture’). The prospects for the new UKST Hα survey of the southern Milky Way with this new filter are excellent.
Taurus Tunable Filter: A Flexible Approach to Narrowband Imaging
Authors: Bland-Hawthorn Joss , Jones D. Heath
Published: March 2011

The Taurus Tunable Filter (TTF) is a tunable narrowband interference filter covering wavelengths from 6300 Å to the sensitivity drop-off of conventional CCDs (∼9600 Å), although a blue ‘arm’ (4000–6500 Å) is to be added by the end of 1997. The TTF offers monochromatic imaging at the Cassegrain foci of both the Anglo-Australian and William Herschel Telescopes, with an adjustable passband of between 6 and 60 Å. In addition, frequency switching with the TTF can be synchronised with movement of charge (charge shuffling) on the CCD, which has important applications to many astrophysical problems. Here we review the different modes of TTF and suggest their use for follow-up narrowband imaging to the AAO/UKST Galactic Plane Hα Survey.
Relationships between Galactic Radio Continuum and HαEmission
Authors: Cram L. E. , Green A. J. , Bock D. C.-J.
Published: March 2011

Radio continuum emission due to thermal bremsstrahlung and optical Hαspectral line emission arise from processes involving similar atomic entities and physical conditions. The relationship between the flux density of the emission from the two processes is mainly a function of the electron temperature of the emitting region, modified by other factors such as the mode of radiation transfer in the hydrogen spectrum. On the other hand, radio continuum radiation due to non-thermal synchrotron emission is formed by species and processes not involved in thermal emission. As a consequence, differences between the observed radio continuum emission and Hαemission from cosmic sources can provide reliable information on a variety of important physical aspects of the sources, including the relative importance of thermal and non-thermal radio emission and the degree of optical obscuration. This paper reviews the theory of the formation of Hαand the radio continuum in the interstellar medium (ISM), discusses some of the factors that must be considered in comparing observations made in the two frequency regimes, and summarises the properties of some classes of galactic object that emit both optical and radio radiation.
CO Observations of the λ-Orionis Ring
Authors: Lang W. J. , Masheder M. R. W.
Published: March 2011

We present results from a new 12CO (J =1→ 0) survey of theλ-Orionis region. The observations cover 110 square degrees uniformly on a Nyquist-sampled grid. We discover CO emission at levels far lower than possible in previous surveys, revealing a structure similar to that seen in IRAS 100μ maps. We derive a total molecular mass of 1·1×104 M☉. A possible explanation for the isolated and localised outbreak of star formation in the region is discussed.
Searching for Supernova Remnants
Authors: Walker A. , Zealey W. J.
Published: March 2011

The UKST/AAO Galactic Plane Hα Survey has the potential to discover many new objects not visible on red plates taken in past surveys. Recent radio surveys have identified large numbers of new supernova remnants, very few of which have been optically identified. Here we will discuss our plans to use this survey to search for optical emission from both new and known supernova remnants. Observations of these objects in the optical and radio wavelengths will reveal important information about the physical and chemical properties of supernova remnants, and their role in the evolution of the galaxy. We also present a composite image of a newly discovered Hα shell around the Coalsack, named the Coalsack Loop. This object has been detected in radio emission and may represent the remains of an old supernova remnant.
Surface Brightness Measurements of Extended Galactic Nebulae
Authors: Stark Ronald , Reif Klaus
Published: March 2011

We discuss the importance of digitised sky-limited Schmidt B- and R-band, and Hα images of extended translucent (AB ≃ 1–5 mag) and dark (AB > 5 mag) clouds. In translucent clouds (e.g. high-latitude cirrus) photons can penetrate through the whole cloud and control the physical and chemical processes. Comparison of the B images with far-infrared/submillimetre CO, CI, and CII emission provides important information on the non-homogeneous cloud structure, carbon chemistry and energy balance. In dark clouds the interior is completely shielded from the interstellar radiation field. L1204 is a dark cloud with at its edge the well-known HII rim S140. The R-band image shows S140 as well as the diffuse extended HII region around the exciting B-type star. However, the sensitivity for Hα in the R-band is rather low and there is contamination with diffusely scattered red light from dust. Deep Hα and R-band imaging of an ∼20′×20′ field has recently been done with the 1 m Hoher List telescope of Bonn University. A wealth of small-scale structures can been seen on continuum-subtracted images which provide new insight on the geometry of this cloud.
Remnant Molecular Clouds in the Ori OB 1 Association
Authors: Ogura Katsuo , Sugitani Koji
Published: March 2011

We suggest and give some evidence that as an HII region expands and the O stars evolve into B giants, remains of the molecular clouds first appear as bright-rimmed clouds, then as cometary globules and finally as small clouds which are visible by the reflected light from the B giants. We propose to call the last of these ‘reflection clouds’ and all three categories collectively ‘remnant clouds’. A list is presented of about 80 objects of these remnant clouds in the Ori OB 1 association. In the Belt region there is a beautiful spatial sequence from bright-rimmed clouds through cometary globules to reflection clouds. We suspect that retarded star formation in remnant clouds can explain the presence of so-called dispersed T Tau stars in the peripheries of OB associations.
Hα Emission from Point Sources in the Magellanic Clouds
Authors: Morgan D. H.
Published: March 2011

Large numbers of the many types of emission-line object that are found in the Magellanic Clouds were first identified through Hα surveys of one kind or another. This paper looks at what has been achieved through such surveys and considers how the planned UKST Hα/TechPan Survey can further this kind of work.
Comparison of Discrete Sources in Radio and Hα Surveys of the Magellanic Clouds and the Potential for the New Hα Survey
Authors: Filipović Miroslav D. , Jones Paul A. , White Graeme L. , Haynes Raymond F.
Published: March 2011

We present a comparison between the latest Parkes radio surveys (Filipović et al. 1995, 1996, 1997) and Hα surveys of the Magellanic Clouds (Kennicutt & Hodge 1986). We have found 180 discrete sources in common for the Large Magellanic Cloud (LMC) and 40 in the field of the Small Magellanic Cloud (SMC). Most of these sources (95%) are HII regions and supernova remnants (SNRs). A comparison of the radio and Hα flux densities shows a very good correlation and we note that many of the Magellanic Clouds SNRs are embedded in HII regions.
Multi-wavelength View of the Interstellar Medium in the Large Magellanic Cloud
Authors: Chu You-Hua
Published: March 2011

The Large Magellanic Cloud (LMC) has been surveyed in optical emission lines, X-rays, radio continuum, HI, and CO lines. These surveys provide views of the interstellar medium (ISM) in the LMC of unprecedented clarity, allowing us to study astrophysical processes and to examine the relationship among the different phases of the ISM. Multi-wavelength images are used to illustrate the physical structures of supernova remnants, superbubbles, and supergiant shells, as well as the global interstellar structure of the LMC.
Star Formation at High Galactic Latitude: A Case for Extensions to the Hα Survey
Authors: Larson Kristen A.
Published: March 2011

The AAO/UKST Hα Survey should be extended to high Galactic latitude (∣b∣ > 25°) to search for T Tauri stars. The Hα Survey can contribute to a complete inventory of young stellar objects in high-latitude clouds, which will help define the limits of conditions and processes that lead to star formation.
Internal Kinematics of the most Luminous HII Regions in M100
Authors: Sabalisck N. S. P. , Rozas M. , Beckman J. E. , Knapen J. H.
Published: March 2011

We have used the TAURUS Fabry–Perot mapping spectrometer on the William Herschel telescope (WHT) to produce a complete kinematic map of the disk of M100 in Hα. Here we show how the internal velocity dispersion (σ) of the principal emission components of the brightest regions varies with their Hα luminosity. The plot shows ample scatter, but an upper envelope in σ is clearly linear (in the log–log plane) with a slope of 2·6, a result which agrees precisely with an earlier graph by Arsenault et al., who selected instead the regions of highest surface brightness. We show that this result, which differs from the conventional prediction from the virial theorem, is consistent with virialisation if the H II regions are density bounded, and thus offers evidence in support of the density bounding hypothesis for the most luminous regions in disk galaxies.
The UM/CTIO Magellanic Cloud Emission-line Survey
Authors: Smith R. Chris ,   MCELS Team
Published: March 2011

The Magellanic Clouds are unique in providing us with sites to study the interstellar medium (ISM) and its components at all scales. To promote the pursuit of such studies, we have begun the Magellanic Cloud Emission-line Survey (MCELS), a deep imaging survey of both of these nearby galaxies in the emission of Hα, [S II], and [O III]. The emission-line images will be used in detailed optical and multiwavelength studies of H II regions, supernova remnants, planetary nebulae, superbubbles, and supergiant shells. Together with parallel surveys at other wavelengths, this survey will provide the foundation upon which to build a deeper understanding of the ISM in the Clouds and other galaxies, from small scales (∼1 pc) all the way up to global scales.
Orientation and Evolutionary Effects in Active Galactic Nuclei
Authors: Heisler Charlene A.
Published: March 2011

In this review I present observational results of active galactic nuclei that my colleagues and I have recently obtained. I discuss their significance in terms of unification schemes and evolutionary scenarios.
A Search for Bright Kuiper Belt Objects
Authors: Brown Michael J. I. , Webster R. L.
Published: March 2011

Since 1992, 60 large Kuiper Belt objects have been detected by ground-based telescopes. Previous surveys which have detected objects have searched approximately 60□° and detected objects with magnitudes 20·6 < mR < 25·0. However, the luminosity function of brighter Kuiper Belt objects is not well determined. The detection of brighter objects would improve our ability to determine the Kuiper Belt objects' surface composition and provide constraints on the population statistics of different formation mechanisms. This paper describes a survey of 12·0□° of sky near the ecliptic to a limiting magnitude of mR ∼ 21. A slow moving candidate was detected near the magnitude limit of the survey.
Further Discussion of Binary Star Radio Survey Data
Authors: Budding E. , Slee O. B. , Jones K.
Published: March 2011

Statistical information on 8280 individual radio observations of binary stars, predominantly at 8·4 GHz using the Parkes 64 m antenna, is presented. Three main groups are distinguished: (i) RS CVn stars, (ii) classical Algol binaries (EA2s), and (iii) detached pairs of generally early type (ETBs).

The RS CVn stars more frequently gave rise to detectable fluxes, while the ETBs, in these data, are a small and rather heterogeneous class. The Algols' emission appears to increase near conjunction phases, though we cannot clearly distinguish any special property of the Algols' phase-dependent behaviour that is not also shared by the RS CVn binaries. Both these categories' data show a bimodal, phase-dependent pattern to the distribution of detections, suggesting that these binary types share similar underlying physical properties, though there could also be other factors at play. The sample sizes of the Algols and particularly the ETB detections are too small for effective, discriminatory statistics, however.
An Investigation of the Molecular Clouds of the Carina HII Region/Molecular Cloud Complex—First Results
Authors: Brooks K. J. , Whiteoak J. B. , Storey J. W. V.
Published: March 2011

The Carina Nebula is an extremely bright southern HII region embedded in a giant molecular cloud and contains some of the most massive stars known in our Galaxy. We are undertaking a multi-wavelength study of the Carina Nebula in order to examine the detailed kinematics and distribution of the molecular and ionised gas, and to look for further evidence of ongoing star formation. Here we present the results of the initial molecular cloud observations which were made by observing the 12CO(1−0) emission with the Mopra antenna. The observations reveal the clumpy morphology of the molecular gas, and allow us to identify many interesting regions for follow-up observations.
Anisotropies and the Power Requirements for Galactic Cosmic Rays
Authors: Clay R. W. , McDonough M.-A. , Smith A. G. K. , Dawson B. R.
Published: March 2011

Measurements of cosmic ray directional properties at about 1015 eV in both northern and southern hemispheres confirm that those particles have a unidirectional anisotropy and are flowing along the direction of our spiral arm from the inner Galactic regions. On the basis of diffusive cosmic ray flow along the Galactic arms, the power required for the Galaxy to maintain this flow is below 1030 W.
Investigating Pulse Morphology in GX 1+4
Authors: Storey Michelle C. , Greenhill J. G. , Kotani T.
Published: March 2011

Observational and theoretical evidence points to the existence of an unusually high magnetic field on GX 1+4. The pulsar is thus an ideal laboratory for studying two-photon cyclotron emission, an important source of photons of frequency significantly less than the cyclotron frequency in X-ray pulsars. Low-frequency approximations to the two-photon cyclotron emission transition probabilities are derived. These are used to calculate the theoretical opening angle of the double-humped pulse shape predicted by the two-photon cyclotron emission model. The theoretical pulse shape, incorporating the effects of gravitational light bending, is compared with observations of GX 1+4. Observed light curves have opening angles consistent with the theoretically predicted maximum value.
An Analytic Flow Solution for YSO Jets
Authors: Liffman Kurt
Published: March 2011

We present an analytic solution for a jet flow from a young stellar object (YSO). This solution allows us to compute the speed, density, and magnetic field strength of the flow, but it is only true if YSO jet flows are powered by toroidal magnetic fields. We illustrate how the balance between centrifugal force and magnetic pressure provides the converging/diverging nozzle shape required to accelerate the flow.
Identification of Two z ~ 3·8 QSOs in a Deep CCD Survey
Authors: Smail Ian , Edge Alastair C. , Ellis Richard S.
Published: March 2011

We present the identifications of two z ~ 3·8 quasars from a deep UBI imaging survey with the Palomar 5·1 m Telescope. The survey covers an area of 0·25 degree2 around a sample of ten z =0·2–0·3 luminous X-ray clusters. The QSOs were identified on the basis of their stellar morphologies, relatively blue optical and very red UV–optical colours. The two objects are Q 1322+5034, with total magnitudes of B =20·8, I =18·3 and (U–B) > 4·7, and Q 1722+3211, which has total magnitudes of B =21·8, I =19·7 and (U–B) > 3·2. Subsequent spectroscopic observations with the 4·2 m William Herschel Telescope have confirmed the identity of these two sources as QSOs at z =3·82 and z =3·73 respectively. Our spectroscopic observations identify a damped Lyman-α absorber in the spectrum of Q 1322+5034 at z =3·439, as well as a second absorption system at z =2·700, which may be either a single very high column density, damped Lyman-α system, or more likely a blend of a number of high column-density absorbers spread over a distance of ~10 Mpc.
Obscuration by Diffuse Cosmic Dust
Authors: Masci Frank J.
Published: March 2011

If the background universe is observed through a significant amount of diffusely distributed foreground dust, then studies at optical wavelengths may be severely biased. Previous studies investigating the effects of foreground dust on background sources assumed dust to be ‘compactly’ distributed, i.e. on scales comparable to the visible extent of normal galaxies. We show, however, that diffuse dust is more effective at obscuring background sources. Galaxy clusters are a likely location for ‘large-scale’ diffusely distributed dust, and its effect on the counts of background sources is explored. We also explore the implications of a hypothesised diffuse intergalactic dust component uniformly distributed to high redshift with comoving mass density equal to that associated with local galaxies. In this case, we predict a deficit in background sources about three times greater than that found in previous studies.
Singularities in a Relativistic Pulsar Wind
Authors: Li Jianke
Published: March 2011

The nature of a singularity in a cool, gravitation-free axisymmetrical, relativistic, steady pulsar wind is further investigated, in line with the recent counter-argument of Ardavan (1995, hereafter A95) that the pure Alfvén ‘singularity’ has an equal importance to the Alfvén singularity if one defines the singularity via a quadratic form rather than using the ratio as adopted by Li & Melrose (1994). The pure Alfvénic point in A95 coincides with the proposed characteristic point through which a continuous wind will meet the star and infinity. However, we find that the critical point as implied in the quadratic form is in fact the intermediate point (Ardavan 1979), but not the pure Alfvénic point. Thus the analysis of A95 does not indicate any significance of the pure Alfvénic point. We also demonstrate that the intermediate point which appears in the quadratic form of A95 is not genuine.
Simulating AXAF Grating Spectra of Accreting White Dwarfs
Authors: Tennant Allyn F. , Wu Kinwah , O'Dell Stephen L. , Weisskopf Martin C.
Published: March 2011

We present simulated AXAF spectra of accreting white dwarfs, using parameters appropriate for magnetic cataclysmic variables. The very high spectral resolution that can be obtained with the High-Energy Transmission Grating of AXAF can resolve the keV X-ray emission lines that characterise the temperature, density and velocity profiles of the shock-heated emission regions of these systems. These simulations demonstrate that actual spectra will allow us to place constraints on the white-dwarf mass and the accretion rate of the systems. The high-resolution spectra also allow the measurement of the velocity of the accretion flow in regions close to the white-dwarf surface.
HI in Early-type Galaxies
Authors: Oosterloo Tom , Morganti Raffaella , Sadler Elaine
Published: March 2011

We summarise the HI properties of early-type galaxies, in particular the differences in HI morphologies observed in early-type galaxies of different luminosities. We find that in low-luminosity early-type galaxies the HI is almost always in a disk-like structure, with central surface densities high enough for star formation to occur. In a few luminous early-type galaxies the HI is also in a disk or in a ring-like structure, but in most luminous early-type galaxies the HI has a relatively irregular morphology. The surface densities in the HI disks in luminous early-type galaxies are lower than in the HI disks in low-luminosity early-type galaxies and no large-scale star formation should occur in these disks. We discuss these different HI characteristics in the context of other properties of early-type galaxies that correlate with luminosity.
First Results from the Parkes Multibeam High-velocity Cloud Survey
Authors: Putman M. E. , Gibson B. K.
Published: March 2011

With the onset of the HI Parkes All-Sky Survey (HIPASS), a new view of the high-velocity cloud (HVC) distribution in the southern sky is being revealed. The dense spatial sampling and unbiased coverage of HIPASS gives it multiple advantages over previous surveys of the southern sky. Detailed views of the clouds' structure and large mosaics of the HI sky allow us to link individual concentrations to larger structures (such as the Magellanic Clouds and the Galaxy), providing pictorial clues as to the origins of HVCs. It is clear that HVCs cannot be uniformly assigned a single origin scenario, and must be categorised appropriately.
The Low-redshift Intergalactic Medium
Authors: Shull J. Michael , Penton Steven V. , Stocke John T.
Published: March 2011

The low-redshift Lyα forest of absorption lines provides a probe of large-scale baryonic structures in the intergalactic medium, some of which may be remnants of physical conditions set up during the epoch of galaxy formation. We discuss our recent Hubble Space Telescope (HST) observations and interpretation of low-z Lyα clouds toward nearby Seyferts and QSOs, including their frequency, space density, estimated mass, association with galaxies, and contribution to Ωb. Our HST/GHRS detections of ∼ 70 Lyα absorbers with Nhi ≥ 1012·6 cm−2 along 11 sightlines covering pathlength Δ(cz) = 114,000 km s−1 show f (>Nhi) α Nhi−0·63±0·04 and a line frequency dN/dz = 200 ± 40 for Nhi > 1012·6 cm−2 (one every 1500 km s−1 of redshift). A group of strong absorbers toward PKS 2155–304 may be associated with gas (400–800) kpc from four large galaxies, with low metallicity (≤0·003 solar) and D/H ≤ 2 × 10−4. At low-z, we derive a metagalactic ionising radiation field from AGN of J0 = × 10−23 erg cm−2 s−1 Hz−1 sr−1 and a Lyα-forest baryon density Ωb =(0·008 ± 0·004)[J−23N14b100]½ for clouds of characteristic size b = (100 kpc)b100.
HI Column Density Distribution Function at z = 0: Connection to Damped Lyα Statistics
Authors: Zwaan Martin A. , Verheijen Marc A. W. , Briggs Frank H.
Published: March 2011

We present a measurement of the HI column density distribution function f(Nhi) at the present epoch for column densities > 1020 cm−2. These high column densities compare to those measured in damped Lyα lines seen in absorption against background quasars. Although observationally rare, it appears that the bulk of the neutral gas in the Universe is associated with these damped Lyα systems. In order to obtain a good anchor point at z = 0 we determine f(Nhi) in the local Universe by using 21 cm synthesis observations of a complete sample of spiral galaxies. We show that f(Nhi) for damped Lyα systems has changed significantly from high z to the present and that change is greatest for the highest column densities. The measurements indicate that low surface brightness galaxies make a minor contribution to the cross section for HI, especially for NHI > 1021 cm−2.
The Violent Interstellar Medium of Nearby Dwarf Galaxies
Authors: Walter Fabian
Published: March 2011

High resolution HI observations of nearby dwarf galaxies (most of which are situated in the M81 group at a distance of about 3·2 Mpc) reveal that their neutral interstellar medium (ISM) is dominated by hole-like features most of which are expanding. A comparison of the physical properties of these holes with the ones found in more massive spiral galaxies (such as M31 and M33) shows that they tend to reach much larger sizes in dwarf galaxies. This can be understood in terms of the galaxy's gravitational potential. The origin of these features is still a matter of debate. In general, young star forming regions (OB-associations) are held responsible for their formation. This picture, however, is not without its critics and other mechanisms such as the infall of high velocity clouds, turbulent motions or even gamma ray bursters have been recently proposed. Here I will present one example of a supergiant shell in IC 2574 which corroborates the picture that OB associations are indeed creating these structures. This particular supergiant shell is currently the most promising case to study the effects of the combined effects of stellar winds and supernova explosions which shape the neutral interstellar medium of (dwarf) galaxies.
A Constraint on the Standard Beaming Model for Superluminal Sources
Authors: Ubachukwu A.
Published: March 2011

We have used two subsamples of superluminal quasars to test the relativistic beaming model, and to place useful constraints on the radio source orientation hypothesis and cosmology. Based on the variation of the observed ratio R of the core-to-lobe radio luminosities with proper motion μ for the subsample of lobe-selected quasars, we show that the observed R–μ data can be explained in terms of a bulk relativistic motion with Lorentz factor γ≈4. Also, from the observed proper motion versus redshift (μ–z) plot for this subsample, we show that γ≈4 implies a high density universe with deceleration parameter q0 = 0·5. Furthermore, from the observed (μ–z) plot for the two subsamples taken separately, we show that both γ and μ for the core-selected subsample exceed those of the lobe-selected subsample by a factor of 2 for the q0 = 0·5 world model. This result is demonstrated to be consistent with an orientation-based unified scheme in which lobe-selected quasars lie, on the average, at an angle which is a factor of ∼2–3 larger than that of their core-selected counterparts.
Two New Planetary Nebulae and an AGN in the Galactic Plane
Authors: Beer S. H. , Vaughan A. E.
Published: March 2011

A search for planetary nebulae was carried out using candidates selected by their infrared colours and 5 GHz radio emission. One new planetary nebula was identified on the basis of its small angular size, strong [O iii] emission and infrared colours. Another object, known as the possible planetary nebula Wray 16–28, is similarly identified as a planetary nebula. An undiscovered AGN was also found, and is classed as a Seyfert 2 galaxy on the basis of its strong O iii emission, linewidths of ∼500 km s−1, and 5 GHz radio flux. Low-resolution optical spectra are presented and distance estimates discussed.
Summary of the ‘Sub-microJansky Radio Sky’ Workshop
Authors: Hopkins Andrew , Ekers Ron , Jackson Carole , Cram Lawrence , Green Anne , Manchester Dick , Staveley-Smith Lister , Norris Ray
Published: March 2011

The Square Kilometre Array Radio Telescope is the next generation radio telescope. An international project is currently under way to design and build an instrument having an effective collecting area two orders of magnitude greater than that of any existing telescope. A number of separate studies are presently investigating how to design the Square Kilometre Array to best carry out the kinds of observations desired by the astronomical community. We present a summary of one of these studies, a workshop called The ‘Sub-microJansky Radio Sky’ held at the ATNF, Sydney, on 17 June 1998. This workshop addressed the nature of the radio sky at the very faint flux densities likely to be attainable by the Square Kilometre Array. In particular, each speaker investigated a separate population of radio sources and how the expected appearance of that population at such faint flux densities would dictate how to refine some of the design constraints for the Square Kilometre Array.
Photohadronic Processes in Astrophysical Environments
Authors: Mücke A. , Rachen J. P. , Engel Ralph , Protheroe R. J. , Stanev Todor
Published: March 2011

We discuss the first applications of our newly developed Monte Carlo event generator SOPHIA to multiparticle photoproduction of relativistic protons with thermal and power-law radiation fields. The measured total cross section is reproduced in terms of excitation and decay of baryon resonances, direct pion production, diffractive scattering, and non-diffractive multiparticle production. Non-diffractive multiparticle production is described using a string fragmentation model. We demonstrate that the widely used ‘Δ-approximation’ for the photoproduction cross section is reasonable only for a restricted set of astrophysical applications. The relevance of this result for cosmic ray propagation through the microwave background and hadronic models of active galactic nuclei and gamma-ray bursts is briefly discussed.
Comets and Communication: Amateur–Professional Tension in Australian Astronomy
Authors: Orchiston Wayne
Published: March 2011

Australasian amateur astronomers, Grigg and Ross, discovered four different comets between 1902 and 1907. Controversy surrounding these discoveries led to a deterioration in relations between Australia's leading amateur astronomers and Baracchi at Melbourne Observatory, and to the eventual transfer of the ‘Australian Central Bureau’ to Sydney Observatory.
Magnetic Fields in Accretion Disks
Authors: de Kool Marthijn , Bicknell Geoffrey V. , Kuncic Zdenka
Published: March 2011

This paper summarises our work on the role of magnetic fields in accretion disks presented in two papers elsewhere. In the first part (a summary of part of Kuncic & Bicknell 1999), we present a formal development of the equations governing the structure of an accretion disk containing magnetohydrodynamic turbulence. The importance of the different terms in the energy and momentum equations is discussed, and a parametrisation of the unresolved processes is suggested that could be used to make further progress. We briefly explore whether an MHD accretion disk can transport a significant part of the gravitational power into a corona by buoyancy. In the second part, we present some exploratory calculations of the vertical structure of accretion disks, in which non-local dissipation of energy due to the buoyant transport of magnetic field energy is taken into account. It is argued that the efficiency of buoyant magnetic transport depends very strongly on the size of the coherent magnetic regions. If the size of the buoyant cells is not very close to the disk thickness, magnetic energy generated by dynamo action inside the disk will be dissipated locally, and will not be available to transport a significant part of the accretion luminosity into a corona.