Search

ABSTRACT We present first results of the H2O Southern Galactic Plane Survey (HOPS), using the Mopra Radio Telescope with a broad-band backend and a beam size of about 2 arcmin. We have observed 100 deg2 of the southern Galactic plane at 12 mm (19.5-27.5 GHz), including spectral line emission from H2O masers, multiple metastable transitions of ammonia, cyanoacetylene, methanol and radio recombination lines. In this paper, we report on the characteristics of the survey and H2O maser emission. We find 540 H2O masers, of which 334 are new detections. The strongest maser is 3933 Jy and the weakest is 0.7 Jy, with 62 masers over 100 Jy. In 14 maser sites, the spread in the velocity of the H2O maser emission exceeds 100 km s−1. In one region, the H2O maser velocities are separated by 351.3 km s−1. The rms noise levels are typically between 1 and 2 Jy, with 95 per cent of the survey under 2 Jy. We estimate completeness limits of 98 per cent at around 8.4 Jy and 50 per cent at around 5.5 Jy. We estimate that there are between 800 and 1500 H2O masers in the Galaxy that are detectable in a survey with similar completeness limits to HOPS. We report possible masers in NH3 (11,9) and (8,6) emission towards G19.61−0.23 and in the NH3 (3,3) line towards G23.33−0.30. [ABSTRACT FROM AUTHOR]

Over the past 3 years, we have conducted a survey of 100 square degrees of the southern Galactic plane with the Mopra radiotelescope (HOPS). The survey includes observations of multiple spectral lines in the 12 mm band, with the most important being the water maser transition at 22.2 GHz and the non-metastable inversion transitions of ammonia. We report on initial results from HOPS, including the detection of 540 water masers, about two-thirds of which appear to be new detections. We also find widespread emission in the NH3 (1,1) line, as well as detec tions in the NH3 (2,2), (3,3), (6,6) and (9,9) lines. [ABSTRACT FROM AUTHOR]

ABSTRACT We have used the Australia Telescope Compact Array to survey the Galactic Centre for the 22-GHz transition of water. The survey provides an unbiased search for water masers within a 0.5 deg2 region about the Centre, and the small synthesized beam directly yields positions to arcsecond accuracy. The detected sources were re-observed 4 months later and showed considerable changes in their spectra, with two sources found in the follow-up that were not seen in the original survey, yielding a total of 27 maser detections. Comparison with methanol and OH surveys shows that, at current sensitivity levels, water masers greatly outnumber the other species. 12 of our maser detections had previously been reported, discovered during searches towards interesting targets in the survey area. The majority of our sources are quite weak, consistent with excitation by young massive stars mostly near the Galactic Centre. Our spectra reveal high-velocity outflows at one-quarter of the water maser sites, a statistic similar to sites in the remainder of the Galaxy. [ABSTRACT FROM AUTHOR]

Observations of H2O masers towards the post-asymptotic-giant-branch star and water fountain source OH 009.1−0.4 were made as part of The H2O southern galactic Plane Survey, with the Mopra radiotelescope. Together with followup observations using the Australia Telescope Compact Array (ATCA), we have identified H2O maser emission over a velocity spread of nearly 400 km s 109 to +289 km s−1). This velocity spread appears to be the largest of any known maser source in our Galaxy. High-resolution observations with the ATCA indicate that the maser emission is confined to a region arcsec and shows weak evidence for a separation of the red- and blueshifted maser spots. We are unable to determine if the water fountain is projected along the line of sight, or is inclined, but either way OH 009.1−0.4 is an interesting source, worthy of followup observations. [ABSTRACT FROM AUTHOR]

This study uses archival high-frequency continuum data to expand the search for Hypercompact H  ii regions and determine the conditions at which they appear, as this stage high mass star formation is short-lived and rare. We use 23 GHz continuum data taken towards methanol masers, which are an excellent signpost for very young embedded high-mass protostars. We have searched for high-frequency, optically thick radio sources to identify HC H  ii region candidates. The data cover 128 fields that include 141 methanol masers identified by the Methanol Multibeam (MMB) survey. We have detected 68 high-frequency radio sources and conducted a multiwavelength analysis to determine their nature. This has identified 49 H  ii regions, 47 of which are embedded in dense clumps fourteen of which do not have a 5 GHz radio counterpart. We have identified 13 methanol maser sites that are coincident with radio sources that have a steep positive spectral index. The majority of these are not detected in the mid-infrared and have been classified as protostellar or young stellar objects in the literature and we therefore consider to be good HC H  ii region candidates, however, further work and higher resolution data are needed to confirm these candidates. [ABSTRACT FROM AUTHOR]

A two-component model of an osteoblastic metastatic lesion has been developed to determine the absorbed dose delivered to soft tissue during systemic radiotherapy of osseous metastases. Doses to soft tissue from radioisotopes distributed in bone were calculated using Burlin's general cavity theory. A correction term was used to account for the absence of charged particle equilibrium within the metastatic lesion. Radiation doses for 153Sm, 186Re, 89Sr and 32P were calculated for several physiologically realistic lesion structures. Burlin's cavity weighting factor was greatest for higher energy isotopes and it decreased as the soft tissue cavity size increased. The correction for the absence of charged particle equilibrium also decreased with soft tissue pathlength, but increased with average bone pathlengths. Doses to soft tissue cavities ranged from 0.1 to 0.2 Gy MBq(-1) d(-1) for 153Sm to 0.5 to 0.6 Gy MBq(-1) d(-1) for 32P. Using the factors calculated in this work, the dose to soft tissue cavities within bone metastases can be calculated when the dose to adjacent bone has been determined, perhaps by autoradiography or electron paramagnetic resonance dosimetry. The doses calculated with this more accurate model of bone metastases demonstrate errors of 20% to 50% in previous calculations of the average dose to homogeneous metastatic lesions.

Strontium-89 radiotherapy is becoming an important treatment in the palliation of bone pain from osteoblastic metastases. The absorbed dose delivered to bone metastases during 89Sr radiotherapy has been estimated in four patients with metastatic prostatic carcinoma. Patients were injected with a tracer dose of 85Sr-chloride. Blood and urine samples were obtained during the week following injection. Strontium-85 scintigrams of metastases and normal bone were obtained up to 8 wk postinjection. Half of the patients showed elevated whole-body retention; plasma-strontium concentrations were decreased from normal values. Uptake of strontium in metastases was 2-25 times that in normal bone but rates of washout of strontium from metastases were similar to those from normal bone. Absorbed doses delivered in infinite time to the metastases by 89Sr ranged from 21 +/- 4 to 231 +/- 56 cGy/MBq with a median value of 68 cGy/MBq. Doses to red marrow were less by a factor of 2 to 50. These absorbed doses are sufficiently large to be expected to produce a therapeutic benefit.