J. R. Dawson, P. A. Jones, C. Purcell, A. J. Walsh, S. L. Breen, C. Brown, E. Carretti, M. R. Cunningham, J. M. Dickey, S. P. Ellingsen, S. J. Gibson, J. F. Gomez, J. A. Green, H. Imai, V. Krishnan, N. Lo, V. Lowe, M. Marquarding, N. M. McClure-Griffiths . We present the full data release for the Southern Parkes Large-Area Survey in Hydroxyl (SPLASH), a sensitive, unbiased single-dish survey of the Southern Galactic Plane in all four ground-state transitions of the OH radical at 1612, 1665, 1667 and 1720 MHz. The survey covers the inner Galactic Plane, Central Molecular Zone and Galactic Centre over the range $|b|<$ 2$^{\circ}$, 332$^{\circ}$ $< l <$ 10$^{\circ}$, with a small extension between 2$^{\circ}$ $< b <$ 6$^{\circ}$, 358$^{\circ}$ $< l <$ 4$^{\circ}$. SPLASH is the most sensitive large-scale survey of OH to-date, reaching a characteristic root-mean-square sensitivity of $\sim15$ mK for an effective velocity resolution of $\sim0.9$ km/s. The spectral line datacubes are optimised for the analysis of extended, quasi-thermal OH, but also contain numerous maser sources, which have been confirmed interferometrically and published elsewhere. We also present radio continuum images at 1612, 1666 and 1720 MHz. Based on initial comparisons with $^{12}$CO(J=1-0), we find that OH rarely extends outside CO cloud boundaries in our data, but suggest that large variations in CO-to-OH brightness temperature ratios may reflect differences in the total gas column density traced by each. Column density estimation in the complex, continuum-bright Inner Galaxy is a challenge, and we demonstrate how failure to appropriately model sub-beam structure and the line-of-sight source distribution can lead to order-of-magnitude errors. Anomalous excitation of the 1612 and 1720 MHz satellite lines is ubiquitous in the inner Galaxy, but is disabled by line overlap in and around the Central Molecular Zone.
G. Hobbs, R. N. Manchester, A. Dunning, A. Jameson, P. Roberts, D. George, J. A. Green, J. Tuthill, L. Toomey, J. F. Kaczmarek, S. Mader, M. Marquarding, A. Ahmed, S. W. Amy, M. Bailes, R. Beresford, N. D. R. Bhat, D. C.-J. Bock, M. Bourne, M. Bowen, et al (52) We describe an ultra-wide-bandwidth, low-frequency receiver ("UWL") recently installed on the Parkes radio telescope. The receiver system provides continuous frequency coverage from 704 to 4032 MHz. For much of the band (~60%) the system temperature is approximately 22K and the receiver system remains in a linear regime even in the presence of strong mobile phone transmissions. We discuss the scientific and technical aspects of the new receiver including its astronomical objectives, as well as the feed, receiver, digitiser and signal-processor design. We describe the pipeline routines that form the archive-ready data products and how those data files can be accessed from the archives. The system performance is quantified including the system noise and linearity, beam shape, antenna efficiency, polarisation calibration and timing stability.
D. McConnell, J.R. Allison, K. Bannister, M.E. Bell, H.E. Bignall, A.P. Chippendale, P.G. Edwards, L. Harvey-Smith, S. Hegarty, I. Heywood, A.W. Hotan, B.T. Indermuehle, E. Lenc, J. Marvil, A. Popping, W. Raja, J.E. Reynolds, R.J. Sault, P. Serra, M.A. Voronkov, et al (54) We describe the performance of the Boolardy Engineering Test Array (BETA), the prototype for the Australian Square Kilometre Array Pathfinder telescope ASKAP. BETA is the first aperture synthesis radio telescope to use phased array feed technology, giving it the ability to electronically form up to nine dual-polarization beams. We report the methods developed for forming and measuring the beams, and the adaptations that have been made to the traditional calibration and imaging procedures in order to allow BETA to function as a multi-beam aperture synthesis telescope. We describe the commissioning of the instrument and present details of BETA's performance: sensitivity, beam characteristics, polarimetric properties and image quality. We summarise the astronomical science that it has produced and draw lessons from operating BETA that will be relevant to the commissioning and operation of the final ASKAP telescope.
G. Hobbs, I. Heywood, M. E. Bell, M. Kerr, A. Rowlinson, S. Johnston, R. M. Shannon, M. A. Voronkov, C. Ward, J. Banyer, P. J. Hancock, Tara Murphy, J. R. Allison, S. W. Amy, L. Ball, K. Bannister, D. C.-J. Bock, D. Brodrick, M. Brothers, A. J. Brown, et al (58) We use observations from the Boolardy Engineering Test Array (BETA) of the Australian Square Kilometre Array Pathfinder (ASKAP) telescope to search for transient radio sources in the field around the intermittent pulsar PSR J1107-5907. The pulsar is thought to switch between an "off" state in which no emission is detectable, a weak state and a strong state. We ran three independent transient detection pipelines on two-minute snapshot images from a 13 hour BETA observation in order to 1) study the emission from the pulsar, 2) search for other transient emission from elsewhere in the image and 3) to compare the results from the different transient detection pipelines. The pulsar was easily detected as a transient source and, over the course of the observations, it switched into the strong state three times giving a typical timescale between the strong emission states of 3.7 hours. After the first switch it remained in the strong state for almost 40 minutes. The other strong states lasted less than 4 minutes. The second state change was confirmed using observations with the Parkes radio telescope. No other transient events were found and we place constraints on the surface density of such events on these timescales. The high sensitivity Parkes observations enabled us to detect individual bright pulses during the weak state and to study the strong state over a wide observing band. We conclude by showing that future transient surveys with ASKAP will have the potential to probe the intermittent pulsar population.
P. Serra, B. Koribalski, V. Kilborn, J. R. Allison, S. W. Amy, L. Ball, K. Bannister, M. E. Bell, D. C.-J. Bock, R. Bolton, M. Bowen, B. Boyle, S. Broadhurst, D. Brodrick, M. Brothers, J. D. Bunton, J. Chapman, W. Cheng, A. P. Chippendale, Y. Chung, et al (59) We present HI imaging of the galaxy group IC 1459 carried out with six antennas of the Australian SKA Pathfinder equipped with phased-array feeds. We detect and resolve HI in eleven galaxies down to a column density of $\sim10^{20}$ cm$^{-2}$ inside a ~6 deg$^2$ field and with a resolution of ~1 arcmin on the sky and ~8 km/s in velocity. We present HI images, velocity fields and integrated spectra of all detections, and highlight the discovery of three HI clouds -- two in the proximity of the galaxy IC 5270 and one close to NGC 7418. Each cloud has an HI mass of $10^9$ M$_\odot$ and accounts for ~15% of the HI associated with its host galaxy. Available images at ultraviolet, optical and infrared wavelengths do not reveal any clear stellar counterpart of any of the clouds, suggesting that they are not gas-rich dwarf neighbours of IC 5270 and NGC 7418. Using Parkes data we find evidence of additional extended, low-column-density HI emission around IC 5270, indicating that the clouds are the tip of the iceberg of a larger system of gas surrounding this galaxy. This result adds to the body of evidence on the presence of intra-group gas within the IC 1459 group. Altogether, the HI found outside galaxies in this group amounts to several times $10^9$ M$_\odot$, at least 10% of the HI contained inside galaxies. This suggests a substantial flow of gas in and out of galaxies during the several billion years of the group's evolution.
J. R. Allison, E. M. Sadler, V. A. Moss, M. T. Whiting, R. W. Hunstead, M. B. Pracy, S. J. Curran, S. M. Croom, M. Glowacki, R. Morganti, S. S. Shabala, M. A. Zwaan, G. Allen, S. W. Amy, P. Axtens, L. Ball, K. W. Bannister, S. Barker, M. E. Bell, D. C.-J. Bock, et al (83) We report the discovery of a new 21-cm HI absorption system using commissioning data from the Boolardy Engineering Test Array of the Australian Square Kilometre Array Pathfinder (ASKAP). Using the 711.5 - 1015.5 MHz band of ASKAP we were able to conduct a blind search for the 21-cm line in a continuous redshift range between $z = 0.4$ and 1.0, which has, until now, remained largely unexplored. The absorption line is detected at $z = 0.44$ towards the GHz-peaked spectrum radio source PKS B1740$-$517 and demonstrates ASKAP's excellent capability for performing a future wide-field survey for HI absorption at these redshifts. Optical spectroscopy and imaging using the Gemini-South telescope indicates that the HI gas is intrinsic to the host galaxy of the radio source. The narrow OIII emission lines show clear double-peaked structure, indicating either large-scale outflow or rotation of the ionized gas. Archival data from the \emphXMM-Newton satellite exhibit an absorbed X-ray spectrum that is consistent with a high column density obscuring medium around the active galactic nucleus. The HI absorption profile is complex, with four distinct components ranging in width from 5 to 300 km s$^{-1}$ and fractional depths from 0.2 to 20 per cent. In addition to systemic HI gas, in a circumnuclear disc or ring structure aligned with the radio jet, we find evidence for a possible broad outflow of neutral gas moving at a radial velocity of $v \sim 300$ km s$^{-1}$. We infer that the expanding young radio source ($t_{\rm age} \approx 2500$ yr) is cocooned within a dense medium and may be driving circumnuclear neutral gas in an outflow of $\sim$ 1 $\mathrm{M}_{\odot}$ yr$^{-1}$.
A. W. Hotan, J. D. Bunton, L. Harvey-Smith, B. Humphreys, B. D. Jeffs, T. Shimwell, J. Tuthill, M. Voronkov, G. Allen, S. Amy, K. Ardern, P. Axtens, L. Ball, K. Bannister, S. Barker, T. Bateman, R. Beresford, D. Bock, R. Bolton, M. Bowen, et al (81) This paper describes the system architecture of a newly constructed radio telescope - the Boolardy Engineering Test Array, which is a prototype of the Australian Square Kilometre Array Pathfinder telescope. Phased array feed technology is used to form multiple simultaneous beams per antenna, providing astronomers with unprecedented survey speed. The test array described here is a 6-antenna interferometer, fitted with prototype signal processing hardware capable of forming at least 9 dual-polarisation beams simultaneously, allowing several square degrees to be imaged in a single pointed observation. The main purpose of the test array is to develop beamforming and wide-field calibration methods for use with the full telescope, but it will also be capable of limited early science demonstrations.
O. I. Wong, E. V. Ryan-Weber, D. A. Garcia-Appadoo, R. L. Webster, L. Staveley-Smith, M. A. Zwaan, M. J. Meyer, D. G. Barnes, V. A. Kilborn, R. Bhathal, W. J. G. de Blok, M. J. Disney, M. T. Doyle, M. J. Drinkwater, R. D. Ekers, K. C. Freeman, B. K. Gibson, S. Gurovich, J. Harnett, P. A. Henning, et al (15) Jul 24 2006
astro-ph arXiv:astro-ph/0607491v1
The Northern HIPASS catalogue (NHICAT) is the northern extension of the HIPASS catalogue, HICAT (Meyer et al. 2004). This extension adds the sky area between the declination range of +2 deg < dec. < +25.5 deg to HICAT's declination range of -90 deg < dec. < +2 deg. HIPASS is a blind HI survey using the Parkes Radio Telescope covering 71% of the sky (including this northern extension) and a heliocentric velocity range of -1,280 km/s to 12,700 km/s . The entire Virgo Cluster region has been observed in the Northern HIPASS. The galaxy catalogue, NHICAT, contains 1002 sources with v_hel > 300 km/s . Sources with -300 km/s < v_hel < 300 km/s were excluded to avoid contamination by Galactic emission. In total, the entire HIPASS survey has found 5317 galaxies identified purely by their HI content. The full galaxy catalogue is publicly-available at <http://hipass.aus-vo.org>.
Jan 18 2006
astro-ph arXiv:astro-ph/0601354v1
We present three Virtual Observatory tools developed at the ATNF for the storage, processing and visualisation of ATCA data. These are the Australia Telescope Online Archive, a prototype data reduction pipeline, and the Remote Visualisation System. These tools were developed in the context of the Virtual Observatory and were intended to be both useful for astronomers and technology demonstrators. We discuss the design and implementation of these tools, as well as issues that should be considered when developing similar systems for future telescopes.
Marianne T. Doyle, M. J. Drinkwater, D. J. Rohde, K. A. Pimbblet, M. Read, M. J. Meyer, M. A. Zwaan, E. Ryan-Weber, J. Stevens, B. S. Koribalski, R. L. Webster, L. Staveley-Smith, D. G. Barnes, M. Howlett, V. A. Kilborn, M. Waugh, M. J. Pierce, R. Bhathal, W. J. G. de Blok, M. J. Disney, et al (21) May 31 2005
astro-ph arXiv:astro-ph/0505591v1
We present the largest catalogue to date of optical counterparts for HI radio-selected galaxies, Hopcat. Of the 4315 HI radio-detected sources from the HI Parkes All Sky Survey (Hipass) catalogue, we find optical counterparts for 3618 (84%) galaxies. Of these, 1798 (42%) have confirmed optical velocities and 848 (20%) are single matches without confirmed velocities. Some galaxy matches are members of galaxy groups. From these multiple galaxy matches, 714 (16%) have confirmed optical velocities and a further 258 (6%) galaxies are without confirmed velocities. For 481 (11%), multiple galaxies are present but no single optical counterpart can be chosen and 216 (5%) have no obvious optical galaxy present. Most of these 'blank fields' are in crowded fields along the Galactic plane or have high extinctions. Isolated 'Dark galaxy' candidates are investigated using an extinction cut of ABj < 1 mag and the blank fields category. Of the 3692 galaxies with an ABj extinction < 1 mag, only 13 are also blank fields. Of these, 12 are eliminated either with follow-up Parkes observations or are in crowded fields. The remaining one has a low surface brightness optical counterpart. Hence, no isolated optically dark galaxies have been found within the limits of the Hipass survey.
M. A. Zwaan, L. Staveley-Smith, B. S. Koribalski, P. A. Henning, V. A. Kilborn, S. D. Ryder, D. G. Barnes, R. Bhathal, P. J. Boyce, W. J. G. de Blok, M. J. Disney, M. J. Drinkwater, R. D. Ekers, K. C. Freeman, B. K. Gibson, A. J. Green, R. F. Haynes, H. Jerjen, S. Juraszek, M. J. Kesteven, et al (20) Feb 22 2003
astro-ph arXiv:astro-ph/0302440v2
We present a new accurate measurement of the HI mass function of galaxies from the HIPASS Bright Galaxy Catalog, a sample of 1000 galaxies with the highest HI peak flux densities in the southern hemisphere (Koribalski et al. 2003). This sample spans nearly four orders of magnitude in HI mass (from log M_HI/M_sun=6.8 to 10.6, H0=75) and is the largest sample of HI 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 HI mass function can be fitted satisfactorily with a Schechter function with faint-end slope alpha=-1.30. This slope is found to be dependent on morphological type, with later type galaxies giving steeper slopes. We extensively test various effects that potentially bias the determination of the HI mass function, including peculiar motions of galaxies, large scale structure, selection bias, and inclination effects, and quantify these biases. The large sample of galaxies enables an accurate measurement of the cosmological mass density of neutral gas: Omega_HI=(3.8 +/- 0.6) x 10^-4. Low surface brightness galaxies contribute only 15% to this value, consistent with previous findings.
Meryl Waugh, M. J. Drinkwater, R. L. Webster, L. Staveley-Smith, V. A. Kilborn, D. G. Barnes, R. Bhathal, W. J. G. de Blok, P. J. Boyce, M. J. Disney, R. D. Ekers, K. C. Freeman, B. K. Gibson, P. A. Henning, H. Jerjen, P. M. Knezek, B. Koribalski, M. Marquarding, R. F. Minchin, R. M. Price, et al (5) Oct 09 2002
astro-ph arXiv:astro-ph/0210170v1
Using HIPASS data, we have searched for HI in a ~25x25 sq.deg. region centred on the Fornax cluster. Within a velocity search range of 300 - 3700 km/s and a lower flux limit of ~40 mJy, 110 galaxies with HI emission were detected, one of which is previously uncatalogued. None of the detections has early-type morphology. Previously unknown velocities for 14 galaxies have been determined, with a further 4 velocity measurements being significantly dissimilar to published values. Identification of an optical counterpart is relatively unambiguous for more than ~90% of our HI galaxies. The galaxies appear to be embedded in a sheet at the cluster velocity which extends for more than 30 deg across the search area. At the nominal cluster distance of ~20 Mpc, this corresponds to an elongated structure more than 10 Mpc in extent. A velocity gradient across the structure is detected, with radial velocities increasing by \~500 km/s from SE to NW. The clustering of galaxies evident in optical surveys is only weakly suggested in the spatial distribution of our HI detections. Our results suggest a considerable deficit of HI-rich galaxies in the centre of the cluster. However, relative to the field, there is a 3(+/-1)-fold excess of HI-rich galaxies in the outer parts of the cluster where galaxies may be infalling towards the cluster for the first time.
S. D. Ryder, B. Koribalski, L. Staveley-Smith, V. Kilborn, D. Malin, G. Banks, D. Barnes, R. Bhatal, W. de Blok, P. Boyce, M. Disney, M. Drinkwater, R. Ekers, K. Freeman, B. Gibson, P. Henning, H. Jerjen, P. Knezek, M. Marquarding, R. Minchin, et al (9) Mar 08 2001
astro-ph arXiv:astro-ph/0103099v1
We report the discovery, from the HI Parkes All-Sky Survey (HIPASS), of a gas cloud associated with the asymmetric spiral galaxy NGC 2442. This object, designated HIPASS J0731-69, contains ~10^9 M_sun of HI, 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 with its stream-like 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 which 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.
V. A. Kilborn, L. Staveley-Smith, M. Marquarding, R. L. Webster, D. F. Malin, G. D. Banks, R. Bhathal, W. J. G. de Blok, P. J. Boyce, M. J. Disney, M. J. Drinkwater, R. D. Ekers, K. C. Freeman, B. K. Gibson, P. A. Henning, H. Jerjen, P. M. Knezek, B. Koribalski, R. F. Minchin, J. R. Mould, et al (8) May 15 2000
astro-ph arXiv:astro-ph/0005267v1
We report the discovery, from the HI Parkes All-Sky Survey (HIPASS), of an isolated cloud of neutral hydrogen which we believe to be extragalactic. The HI mass of the cloud (HIPASS J1712-64) is very low, 1.7 x 10^7 Msun, using an estimated distance of ~3.2 Mpc. Most significantly, we have found no optical companion to this object to very faint limits (mu(B)~ 27 mag arcsec^-2). HIPASS J1712-64 appears to be a binary system similar to, but much less massive than, HI 1225+01 (the Virgo HI Cloud) and has a size of at least 15 kpc. The mean velocity dispersion, measured with the Australia Telescope Compact Array (ATCA), is only 4 km/s for the main component and because of the weak or non-existent star-formation, possibly reflects the thermal linewidth (T<2000 K) rather than bulk motion or turbulence. The peak column density for HIPASS J1712-64, from the combined Parkes and ATCA data, is only 3.5 x 10^19 cm^-2, which is estimated to be a factor of two below the critical threshold for star formation. Apart from its significantly higher velocity, the properties of HIPASS J1712-64 are similar to the recently recognised class of Compact High Velocity Clouds. We therefore consider the evidence for a Local Group or Galactic origin, although a more plausible alternative is that HIPASS J1712-64 was ejected from the interacting Magellanic Cloud/Galaxy system at perigalacticon ~ 2 x 10^8 yr ago.