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Papers by Anne Green

Proceedings of the International Astronomical Union, 2005

There have been important advances in radio astronomy in the last three years. New discoveries bo... more There have been important advances in radio astronomy in the last three years. New discoveries both at the galactic and extragalactic scale have been reported over this period and we highlight here several of them. The outstanding results of the Wilkinson Microwave Anisotropy Probe satellite, allowing an accurate determination of the main cosmological constants, are certainly among the most important. At the international level, the consolidation of the Atacama Large Millimeter Array project, with participation of the USA, Europe, and Japan and an estimated cost of around one billion US dollars, takes the construction of radio telescopes to a new level of complexity and potential. We also include the Progress Report of the Working Group on Historic Radio Astronomy, that includes a description of the duties and activities of this recently created working group.

The Astronomical Journal, 1999

We have carried out a study of the interaction of the supernova remnant (SNR) G18.8]0.3 with the ... more We have carried out a study of the interaction of the supernova remnant (SNR) G18.8]0.3 with the surrounding interstellar medium. Observations of the H I, 12CO, 13CO, and OH (1720 MHz) lines were performed toward a large Ðeld around G18.8]0.3 using the Parkes (Australia) 64 m single-dish telescope, the 4 m NANTEN millimetric telescope (Las Campanas Observatory, Chile), and the Very Large Array (NRAO). The present survey has revealed the existence of an elongated molecular cloud (about 21@ ] 6@ in size) adjacent to the more Ñattened borders of the SNR and to the far side of the remnant. The overall CO and H I morphology and kinematics allow us to conclude that the explosion occurred near the border of a preexisting molecular cloud, driving a slow shock into the cloud. The presence of di †use shock-heated dust with a color temperature of about 30 K was shown in coincidence with the molecular feature using IRAS data. The shocked CO and H I gas was detected between ]10 and ]27 km s~1 (LSR). The systemic velocity of this complex, about ]19 km s~1, yields a kinematic distance of about 1.9 kpc for G18.8]0.3. The shock is presently expanding into the cloud at D10 km s~1. Masses of the order of 7300, 1100, and 55 are estimated for the associated molecular hydrogen, M _ atomic hydrogen, and heated dust, respectively. The total kinetic energy transferred by the supernova shock to the surrounding interstellar medium is of the order of 1049 ergs. An age of D16,000 yr is calculated for G18.8]0.3. The extended molecular feature with a density of D600 cm~3 has denser clumps immersed in it, with densities ranging from D2500 to D6000 cm~3. Three out of Ðve of these clumps were found to contain luminous IRAS pointlike sources compatible with protostellar candidates, suggesting a causal relationship with the supernova explosion that deserves further investigation. The interferometric search for OH (1720 MHz) masers gave negative results. These OH masers can be short-lived occurrences and dissipate quickly in the cooling postshock gas because of the very restrictive conditions under which masers form. Therefore, their absence does not preclude the hypothesis of shock-cloud interaction.

The Astronomical Journal, 2004

We present the HIPASS Bright Galaxy Catalog (BGC) which contains the 1000 H i-brightest galaxies ... more We present the HIPASS Bright Galaxy Catalog (BGC) which contains the 1000 H i-brightest galaxies in the southern sky as obtained from the H i Parkes All-Sky Survey (HIPASS). The selection of the brightest sources is based on their H i peak flux density (S peak 116 mJy) as measured from the spatially integrated HIPASS spectrum. The derived H i masses range from ∼ 10 7 to 4 × 10 10 M ⊙. While the BGC (z < 0.03) is complete in S peak , only a subset of ∼500 sources can be considered complete in integrated H i flux density (F HI 25 Jy km s −1). The HIPASS BGC contains a total of 158 new redshifts. These belong to 91 new sources for which no optical or infrared counterparts have previously been cataloged, an additional 51 galaxies for which no redshifts were previously known, and 16 galaxies for which the cataloged optical velocities disagree. Of the 91 newly catalogued BGC sources, only four are definite H i clouds: while three are likely Magellanic debris with velocities around 400 km s −1 , one is a tidal cloud associated with the NGC 2442 galaxy group. The remaining 87 new BGC sources, the majority of which lie in the Zone of Avoidance, appear to be galaxies. We identified optical counterparts to all but one of the 30 new galaxies at Galactic latitudes |b| > 10 •. Therefore, the BGC yields no evidence for a population of "free-floating" intergalactic H i clouds without associated optical counterparts. HIPASS provides a clear view of the local large-scale structure. The dominant features in the sky distribution of the BGC are the Supergalactic Plane and the Local Void. In addition, one can clearly see the Centaurus Wall which connects via the Hydra and Antlia clusters to the Puppis filament. Some previously hardly noticed galaxy groups stand out quite distinctively in the H i sky distribution. Several new structures are seen for the first time, not only behind the Milky Way.

The Astronomical Journal, 2003

We present a new, accurate measurement of the H i mass function of galaxies from the HIPASS Brigh... more We present a new, accurate measurement of the H i mass function of galaxies from the HIPASS Bright Galaxy Catalog, a sample of 1000 galaxies with the highest H i peak flux densities in the southern (< 0) hemisphere. This sample spans nearly 4 orders of magnitude in H i mass [log (M H i /M) + 2 log h 75 = 6.8-10.6] and is the largest sample of H i-selected galaxies to date. We develop a bivariate maximum likelihood technique to measure the space density of galaxies and show that this is a robust method, insensitive to the effects of large-scale structure. The resulting H i mass function can be fitted satisfactorily with a Schechter function with faint-end slope ¼ À1:30. This slope is found to be dependent on morphological type, with late-type galaxies giving steeper slopes. We extensively test various effects that potentially bias the determination of the H i mass function, including peculiar motions of galaxies, large-scale structure, selection bias, and inclination effects, and we quantify these biases. The large sample of galaxies enables an accurate measurement of the cosmological mass density of neutral gas: H i = (3.8 AE 0.6) Â 10 À4 h À1 75. Low surface brightness galaxies contribute only $15% to this value, consistent with previous findings.

Monthly Notices of the Royal Astronomical Society, 2018

Using the Mopra telescope, we have targeted 61 regions in the Carina Nebula, covering an area of ... more Using the Mopra telescope, we have targeted 61 regions in the Carina Nebula, covering an area of 1.5 deg 2 , of bright and compact 870 μm dust continuum emission for molecular line emission from a host of 16 spectral lines at 3 mm, including several dense gas tracers. We found that the clumps detected in Carina in general have in average higher temperatures (27 K compared to 21 K), and lower masses (214 M compared to 508 M) than clumps located at a similar distance to us in the Galactic plane. We compare the properties of the molecular line emission of these clumps with the MALT90 survey, finding that the detection rates of the molecular lines are similar to MALT90 clumps that are classified as photodissociation regions. However, most of the clumps located within 10 arcmin of η Carina have little molecular line emission detected in our observations. Given the lack of maser detection in the Carina region, we also compared the properties of the clumps in Carina to those of Galactic clumps associated with 6.7-GHz methanol masers. We found that the clumps in Carina are warmer, less massive, and show less emission from the four most commonly detected molecules, HCO + , N 2 H + , HCN, and HNC, compared to clumps associated with masers in the Galactic Plane. Overall our results are consistent with the scenario in which the high radiation field of η Carina is dramatically affecting its local environment, and therefore the chemical composition of the dense clumps.

The first epoch Molonglo Galactic Plane Survey (MGPS1) is a radio continuum survey made using the... more The first epoch Molonglo Galactic Plane Survey (MGPS1) is a radio continuum survey made using the Molonglo Observatory Synthesis Telescope (MOST) at 843 MHz with a resolution of 43" X 43" cosec |delta|. The region surveyed is 245 deg < l < 355 deg, |b| < 1.5 deg. The thirteen 9 deg X 3 deg mosaic images presented here are the superposition of over 450 complete synthesis observations, each taking 12 h and covering 70' X 70' cosec |delta|. The root-mean-square sensitivity over much of the mosaiced survey is 1-2 mJy/beam (1 sigma), and the positional accuracy is approximately 1" X 1" cosec |delta| for sources brighter than 20 mJy. The dynamic range is no better than 250:1, and this also constrains the sensitivity in some parts of the images. The survey area of 330 sq deg contains well over 12,000 unresolved or barely resolved objects, almost all of which are extra-galactic sources lying in the Zone of Avoidance. In addition a significant fraction of...

In this paper we study 21-cm absorption spectra and the corresponding emission spectra toward bri... more In this paper we study 21-cm absorption spectra and the corresponding emission spectra toward bright continuum sources in the test region (326 • < l < 333 •) of the Southern Galactic Plane Survey. This survey combines the high resolution of the Australia Telescope Compact Array with the full brightness temperature information of the Parkes single dish telescope. In particular, we focus on the abundance and temperature of the cool atomic clouds in the inner galaxy. The resulting mean opacity of the HI, < κ >, is measured as a function of Galactic radius; it increases going in from the solar circle, to a peak in the molecular ring of about four times its local value. This suggests that the cool phase is more abundant there, and colder, than it is locally. The distribution of cool phase temperatures is derived in three different ways. The naive, "spin temperature" technique overestimates the cloud temperatures, as expected. Using two alternative approaches we get good agreement on a histogram of the cloud temperatures, T cool , corrected for blending with warm phase gas. The median temperature is about 65 K, but there is a long tail reaching down to temperatures below 20 K. Clouds with temperatures below 40 K are common, though not as common as warmer clouds (40 to 100 K).

We report the first detection of a glitch in the radio pulsar PSR J0908$-$4913 (PSR B0906$-$49) d... more We report the first detection of a glitch in the radio pulsar PSR J0908$-$4913 (PSR B0906$-$49) during regular timing observations by the Molonglo Observatory Synthesis Telescope (MOST) as part of the UTMOST project.

The Astrophysical Journal, 2021

We report the most detailed 1–3 GHz radio continuum emission map of the nearest region of massive... more We report the most detailed 1–3 GHz radio continuum emission map of the nearest region of massive-star formation, the Carina Nebula. As part of a large program with the Australia Telescope Compact Array, we have covered ∼12 deg2, achieving an angular resolution of ∼16″, representing the largest and most complete map of the radio continuum to date. Our continuum map shows a spectacular and complex distribution of emission across the nebula, with multiple structures such as filaments, shells, and fronts across a wide range of size scales. The ionization fronts have advanced far into the southern and northern region of the Galactic plane, as fronts are clearly detected at distances of ∼80 pc from the stellar clusters in the center. We estimated an ionization photon luminosity Q H = (7. 8 ± 0.8) × 1050 s−1, which corresponds to ∼85% of the total value obtained from stellar population studies. Thus, approximately 15% of the ionizing flux has escaped from the nebula into the diffuse Galac...

The Astrophysical Journal, 2020

Carbon-bearing molecules, particularly CO, have been widely used as tracers of molecular gas in t... more Carbon-bearing molecules, particularly CO, have been widely used as tracers of molecular gas in the interstellar medium (ISM). In this work, we aim to study the properties of molecules in diffuse, cold environments, where CO tends to be under-abundant and/or sub-thermally excited. We performed one of the most sensitive (down to τ CO rms ∼ 0.002 and τ HCO + rms ∼ 0.0008) sub-millimeter molecular absorption line observations towards 13 continuum sources with the ALMA. CO absorption was detected in diffuse ISM down to A v < 0.32 mag and HCO + was down to A v < 0.2 mag, where atomic gas and dark molecular gas (DMG) starts to dominate. Multiple transitions measured in absorption toward 3C454.3 allow for a direct determination of excitation temperatures T ex of 4.1 K and 2.7 K, for CO and for HCO + , respectively, which are close to the cosmic microwave background (CMB) and provide explanation for their being undercounted in emission surveys. A stronger linear correlation was found between N HCO + and N H2 (Pearson correlation coefficient P ∼ 0.93) than that of N CO and N H2 (P ∼ 0.33), suggesting HCO + being a better tracer of H 2 than CO in diffuse gas. The derived CO-to-H 2 conversion factor (the CO X-factor) of (14 ± 3) × 10 20 cm −2 (K km s −1) −1 is approximately 6 times larger than the average value found in the Milky Way.

Research Notes of the AAS, 2018

Monthly Notices of the Royal Astronomical Society, 2017

We present the first interferometric detections of fast radio bursts (FRBs), an enigmatic new cla... more We present the first interferometric detections of fast radio bursts (FRBs), an enigmatic new class of astrophysical transient. In a 180-d survey of the Southern sky, we discovered three FRBs at 843 MHz with the UTMOST array, as a part of commissioning science during a major ongoing upgrade. The wide field of view of UTMOST (≈9 deg 2) is well suited to FRB searches. The primary beam is covered by 352 partially overlapping fan-beams, each of which is searched for FRBs in real time with pulse widths in the range 0.655-42 ms, and dispersion measures ≤2000 pc cm −3. Detections of FRBs with the UTMOST array place a lower limit on their distances of ≈10 4 km (limit of the telescope near-field) supporting the case for an astronomical origin. Repeating FRBs at UTMOST or an FRB detected simultaneously with the Parkes radio telescope and UTMOST would allow a few arcsec localization, thereby providing an excellent means of identifying FRB host galaxies, if present. Up to 100 h of followup for each FRB has been carried out with the UTMOST, with no repeating bursts seen. From the detected position, we present 3σ error ellipses of 15 arcsec × 8. • 4 on the sky for the point of origin for the FRBs. We estimate an all-sky FRB rate at 843 MHz above a fluence F lim of 11 Jy ms of ∼78 events sky −1 d −1 at the 95 per cent confidence level. The measured rate of FRBs at 843 MHz is two times higher than we had expected, scaling from the FRB rate at the Parkes radio telescope, assuming that FRBs have a flat spectral index and a uniform distribution in Euclidean space. We examine how this can be explained by FRBs having a steeper spectral index and/or a flatter logN-logF distribution than expected for a Euclidean Universe.

Monthly Notices of the Royal Astronomical Society, 2001

The acquisition of H i Parkes All Sky Survey (HIPASS) southern sky data commenced at the Australi... more The acquisition of H i Parkes All Sky Survey (HIPASS) southern sky data commenced at the Australia Telescope National Facility's Parkes 64-m telescope in 1997 February, and was completed in 2000 March. HIPASS is the deepest H i survey yet of the sky south of declination 128, and is sensitive to emission out to 170 h 21 75 MpcX The characteristic root mean square noise in the survey images is 13.3 mJy. This paper describes the survey observations, which comprise 23 020 eight-degree scans of 9-min duration, and details the techniques used to calibrate and image the data. The processing algorithms are successfully designed to be statistically robust to the presence of interference signals, and are particular to imaging point (or nearly point) sources. Specifically, a major improvement in image quality is obtained by designing a median-gridding algorithm which uses the median estimator in place of the mean estimator.

Monthly Notices of the Royal Astronomical Society, 2012

We demonstrate a newly developed mid-infrared (MIR) planetary nebula (PN) selection technique. It... more We demonstrate a newly developed mid-infrared (MIR) planetary nebula (PN) selection technique. It is designed to enable efficient searches for obscured, previously unknown, PN candidates present in the photometric source catalogues of Galactic plane MIR sky surveys. Such selection is now possible via new, sensitive, high-to-medium resolution, MIR satellite surveys such as those from the Spitzer Space Telescope and the all-sky Wide-Field Infrared Survey Explorer (WISE) satellite missions. MIR selection is based on how different colour-colour planes isolate zones (sometimes overlapping) that are predominately occupied by different astrophysical object types. These techniques depend on the reliability of the available MIR source photometry. In this pilot study we concentrate on MIR point source detections and show that it is dangerous to take the MIR GLIMPSE (Galactic Legacy Infrared Mid-Plane Survey Extraordinaire) photometry from Spitzer for each candidate at face value without examining the actual MIR image data. About half of our selected sources are spurious detections due to the applied source detection algorithms being affected by complex MIR backgrounds and the de-blending of diffraction spikes around bright MIR point sources into point sources themselves. Nevertheless, once this additional visual diagnostic checking is performed, valuable MIR selected PN candidates are uncovered. Four turned out to have faint, compact, optical counterparts in our Hα survey data missed in previous optical searches. We confirm all of these as true PNe via our follow-up optical spectroscopy. This lends weight to the veracity of our MIR technique. It demonstrates sufficient robustness that high-confidence samples of new Galactic PN candidates can be extracted from these MIR surveys without confirmatory optical spectroscopy and imaging. This is problematic or impossible when the extinction is large.

Publications of the Astronomical Society of Australia, 2013

The Australian Square Kilometre Array Pathfinder (ASKAP) will give us an unprecedented opportunit... more The Australian Square Kilometre Array Pathfinder (ASKAP) will give us an unprecedented opportunity to investigate the transient sky at radio wavelengths. In this paper we present VAST, an ASKAP survey for Variables and Slow Transients. VAST will exploit the wide-field survey capabilities of ASKAP to enable the discovery and investigation of variable and transient phenomena from the local to the cosmological, including flare stars, intermittent pulsars, X-ray binaries, magnetars, extreme scattering events, interstellar scintillation, radio supernovae, and orphan afterglows of gamma-ray bursts. In addition, it will allow us to probe unexplored regions of parameter space where new classes of transient sources may be detected. In this paper we review the known radio transient and variable populations and the current results from blind radio surveys. We outline a comprehensive program based on a multi-tiered survey strategy to characterise the radio transient sky through detection and mo...

We present a new planetary nebula, first identified in images from the Australia Telescope Compac... more We present a new planetary nebula, first identified in images from the Australia Telescope Compact Array, although not recognized at that time. Recent observations with the Spitzer Space Telescope during the GLIMPSE Legacy program have rediscovered the object. The highresolution radio and infrared images enable the identification of the central star or its wind, the recognition of the radio emission as thermal, and the probable presence of polycylic aromatic hydrocarbons in and around the source. These lead to the conclusion that G313.3+00.3 is a planetary nebula. This object is of particular interest because it was discovered solely through radio and mid-infrared imaging, without any optical (or near-infrared) confirmation, and acts as a proof of concept for the discovery of many more highly extinguished planetary nebulae. G313.3+00.3 is well-resolved by both the instruments with which it was identified, and suffers extreme reddening due to its location in the Scutum-Crux spiral arm.

All in-text references underlined in blue are linked to publications on ResearchGate, letting you... more All in-text references underlined in blue are linked to publications on ResearchGate, letting you access and read them immediately.

Using data from the Southern Galactic Plane Survey (SGPS) we analyze an HI self-absorption cloud ... more Using data from the Southern Galactic Plane Survey (SGPS) we analyze an HI self-absorption cloud centered on l = 318.0 ◦ , b =-0.5 ◦ , and velocity, v =-1.1 km s −1. The cloud was observed with the Australia Telescope Compact Array (ATCA) and the Parkes Radio Telescope, and is at a near kinematic distance of � 400 pc with derived dimensions of � 5 × 11 pc. We apply two different methods to find the optical depth and spin temperature. In both methods we find upper limit spin temperatures ranging from 20 K to 25 K and lower limit optical depths ∼ 1. We look into the nature of the HI emission and find that 60-70 % originates behind the cloud. We analyze a second cloud at the same velocity centered on l = 319 ◦ and b = 0.4 ◦ with an upper limit spin temperature of 20 K and a lower limit optical depth of 1.6. The similarities in spin temperature, optical depth, velocity, and spatial location are evidence the clouds are associated, possibly as one large cloud consisting of smaller clumps ...

We have mapped the radio emission in the error ellipse of GeV J1417-6100 (2EGS J1418-6049) at 13c... more We have mapped the radio emission in the error ellipse of GeV J1417-6100 (2EGS J1418-6049) at 13cm and 20cm using the Australia Telescope Compact Array. We find a large shell with extended wings, at the edge of which is a non-thermal, polarized structure with a center filled morphology (the ‘Rabbit’), coincident with an extended, hard X-ray source. We discuss the various sources seen within the ellipse as potential counterparts of the γ−ray source. We conclude that the most likely scenario is that the Rabbit is a wind nebula surrounding a radio-quiet γ−ray pulsar. Subject headings: Gamma rays: observations — radio continuum: ISM — pulsars: general — supernova remnants 1.