Showing papers by "Elaine M. Sadler published in 2001"
Swinburne University of Technology1, Australia Telescope National Facility2, ASTRON3, University of Leicester4, Cardiff University5, University of Western Sydney6, University of Bristol7, University of Melbourne8, Australian National University9, University of Sydney10, University of New Mexico11, Space Telescope Science Institute12, Universidad de Guanajuato13
TL;DR: The HIPASS data was acquired at the Australia Telescope National Facility's Parkes 64m telescope in 1997 February, and was completed in 2000 March as mentioned in this paper, and the characteristic root mean square noise in the survey images is 13.3 mJy.
Abstract: The acquisition of HI Parkes All Shy 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 HI survey yet of the sky south of declination +2 degrees, and is sensitive to emission out to 170 h(75)(-1) Mpc. 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.
603 citations
TL;DR: In this article, the first 210 fields observed in the 2dF Galaxy Redshift Survey (2dFGRS), covering an effective area of 325 square degrees (about 20% of the final 2DFGRS area).
Abstract: We have cross-matched the 1.4 GHz NRAO VLA Sky Survey (NVSS) with the first 210 fields observed in the 2dF Galaxy Redshift Survey (2dFGRS), covering an effective area of 325 square degrees (about 20% of the final 2dFGRS area). This yields a set of optical spectra of 912 candidate NVSS counterparts, of which we identify 757 as genuine radio IDs - the largest and most homogeneous set of radio-source spectra ever obtained. The 2dFGRS radio sources span the redshift range z=0.005 to 0.438, and are a mixture of active galaxies (60%) and star-forming galaxies (40%). About 25% of the 2dFGRS radio sources are spatially resolved by NVSS, and the sample includes three giant radio galaxies with projected linear size greater than 1 Mpc. The high quality of the 2dF spectra means we can usually distinguish unambiguously between AGN and star-forming galaxies. We have made a new determination of the local radio luminosity function at 1.4 GHz for both active and star-forming galaxies, and derive a local star-formation density of 0.022+/-0.004 solar masses per year per cubic Mpc. (Ho=50 km/s/Mpc).
246 citations
Australia Telescope National Facility1, University of Melbourne2, University of Wales3, Swinburne University of Technology4, University of Western Sydney5, Mount Stromlo Observatory6, University of New Mexico7, Space Telescope Science Institute8, ASTRON9, University of Sydney10, University of Leicester11
TL;DR: In this article, a gas cloud associated with the asymmetric spiral galaxy NGC 2442 was discovered from the H I Parkes All-Sky Survey (HIPASS) data.
Abstract: We report the discovery from the H I Parkes All-Sky Survey (HIPASS) of a gas cloud associated with the asymmetric spiral galaxy NGC 2442. This object, designated HIPASS J0731-69, contains similar to 10(9) M-. of H I, or nearly one-third as much atomic gas as NGC 2442 itself. No optical counterpart to any part of HIPASS J0731-69 has yet been identified, consistent with the gas being diffuse and its streamlike kinematics. If the gas in HIPASS J0731-69 was once part of NGC 2442, then it was most likely a fairly recent tidal encounter with a moderately massive companion that tore it loose, although the possibility of ram-pressure stripping cannot be ruled out. This discovery highlights the potential of the HIPASS data for yielding new clues to the nature of some of the best-known galaxies in the local universe.
70 citations
TL;DR: In this article, the results of HI observations of five dust-lane elliptical galaxies with the Australia Telescope Compact Array are presented, and sensitive upper limits are obtained for the other three.
Abstract: We present the results of HI observations of five dust-lane ellipticals with the Australia Telescope Compact Array. Two galaxies (NGC 3108 and NGC 1947) are detected, and sensitive upper limits are obtained for the other three. In the two detected galaxies, the HI is distributed in a regular, extended and warped disk-like structure of low surface brightness. Adding data from the literature, we find that several more dust-lane ellipticals have regular HI structures. This HI is likely to be a remnant of accretions/mergers which took place a considerable time ago, and in which a significant fraction of the gas survived to form a disk. The presence of regular HI structures suggests that some mergers lead to galaxies with extended low surface brightness density gas disks. These gas disk will evolve very slowly and these elliptical galaxies will remain gas rich for a long period of time. (abridged)
62 citations
TL;DR: The first results of a survey of blue horizontal-branch (BHB) stars in the Galactic bulge were presented in this article. But the results were limited to stars with strong Balmer lines.
Abstract: We present the first results of a survey of blue horizontal-branch (BHB) stars in the Galactic bulge. In this exploratory study, candidates with 15 ≤ V ≤ 17.5 covering a wide range in B-V color were selected from Cerro Tololo Inter-American Observatory (CTIO) Schmidt UBV photometry. Blue spectra were recorded at 2.4 A FWHM resolution for 164 stars in a 1.3 deg2 field, ~75 from the Galactic center. Radial velocities were measured for all stars. For stars with strong Balmer lines, we devised and applied a spectroscopic technique to determine stellar temperature Teff, gravity log g, and metallicity [Fe/H] independent of reddening. The reddening and distance to each star were then found from UBV photometry. Reddening proved highly variable, with E(B-V) ranging from 0.0 to 0.55, around a mean of 0.28. The B-V colors of cool HB stars of solar metallicity reddened by E(B-V) ≥ 0.3 overlap those of foreground main-sequence stars, but the U-B versus B-V diagram distinguishes these groups until E(B-V) > 0.5. Forty-seven BHB candidates were identified with Teff ≥ 7250 K. Seven have the gravities of Population I stars, three are ambiguous, and 37 are HB stars, including perhaps a dozen RR Lyrae stars. The unambiguous BHB stars are all cooler than 9000 K. They span a wide metallicity range, from solar to 1/300 solar. The warmer BHB stars are more metal-poor and loosely concentrated toward the Galactic center, while the cooler ones are of somewhat higher metallicity and are situated closer to the center. We detect two cool solar-metallicity HB stars in the bulge of our own Galaxy, the first such stars known. Still elusive are their fainter hot counterparts, the metal-rich sdB/O stars strong in ultraviolet light.
10 citations
01 Jan 2001
TL;DR: In this paper, a class of low-luminosity E/S0 galaxies which have both HI disks and (in contrast to more luminous E /S0s with HI) ongoing star formation is discussed.
Abstract: We discuss a class of low-luminosity E/S0 galaxies which have both HI disks and (in contrast to more luminous E/S0s with HI) ongoing star formation. We suggest that such objects are common, but that only a few are known at present because optical magnitude-limited galaxy catalogues are biased against them. The HI Parkes All-Sky Survey (HIPASS) should eventually detect many more. We suggest that `boxy' and `disky' ellipticals are distinct not only in their structure and kinematics, but in their star-formation history.
1 citations