Patricia Henning

The Long Wavelength Array (LWA) will be a new multi-purpose radio telescope operating in the frequency range 10-88 MHz. Upon completion, LWA will consist of 53 phased array "stations" distributed over a region about 400 km in diameter in the state of New Mexico. Each station will consist of 256 pairs of dipole-type antennas whose signals are formed into beams, with outputs transported to a central location for high-resolution aperture synthesis imaging. The resulting image sensitivity is estimated to be a few mJy (5 sigma, 8 MHz, 2 polarizations, 1 hr, zenith) in 20-80 MHz; with resolution and field of view of (8", 8 deg) and (2",2 deg) at 20 MHz and 80 MHz, respectively. All 256 dipole antennas are in place for the first station of the LWA (called LWA-1), and commissioning activities are well underway. The station is located near the core of the EVLA, and is expected to be fully operational in early 2011.

We present the results of the northern extension of the H I Parkes Zone of Avoidance Survey, a blind H I survey utilizing the multibeam receiver on the Parkes 64 m telescope. In the two regions studied here, l = 36°–52° and l = 196°–212°, |b| ≤ 5°, we have detected 77 H I galaxies, 20 of which have been previously detected in H I. The survey has a median rms noise of 6.0 mJy beam^-1 and is complete to a mean flux density of 22 mJy. We have searched for multiwavelength counterparts to the 77 galaxies detected here: 19, 27, and 11 have a likely optical, 2MASS, and IRAS cataloged counterpart, respectively. A further 16 galaxies have likely visible counterparts on the Digitized Sky Survey. The detection of these 77 galaxies allows a closer inspection of the large-scale structures in these regions. We see several filaments crossing the Galactic plane, one of which appears to be the continuation of a sine-wave–like feature that can be traced across the whole southern sky. An analysis of the H I mass function suggests that the regions studied here may be underdense. One particularly noteworthy galaxy is HIZOA J0630+08 (l, b = 203°, - 09) with a velocity of 367 ± 1 km s^-1. We suggest that it belongs to the nearby Orion Group, which includes a small number of dwarf galaxies. The newly detected galaxies improve our understanding of the properties of several voids, such as the Orion, Gemini, and Canis Major voids.

The first deep catalog of the H I Parkes All Sky Survey (HIPASS) is presented, covering the south celestial cap (SCC) region. The SCC area is ~2400 deg² and covers δ < -62°. The average rms noise for the survey is 13 mJy beam^-1. Five hundred thirty-six galaxies have been cataloged according to their neutral hydrogen content, including 114 galaxies that have no previous cataloged optical counterpart. This is the largest sample of galaxies from a blind H I survey to date. Most galaxies in optically unobscured regions of sky have a visible optical counterpart; however, there is a small population of low-velocity H I clouds without visible optical counterparts whose origins and significance are unclear. The rms accuracy of the HIPASS positions is found to be 19. The H I mass range of galaxies detected is from ~10⁶ to ~10¹¹ M_⊙. There are a large number of late-type spiral galaxies in the SCC sample (66%), compared with 30% for optically selected galaxies from the same region in the NASA Extragalactic Database. The average ratio of H I mass to B luminosity of the sample increases according to optical type, from 1.8 M_⊙/L_⊙ for early types to 3.2 M_⊙/L_⊙ for late-type galaxies. The H I–detected galaxies tend to follow the large-scale structure traced by galaxies found in optical surveys. From the number of galaxies detected in this region of sky, we predict the full HIPASS catalog will contain ~5000 galaxies, to a peak flux density limit of ~39 mJy (3 σ), although this may be a conservative estimate as two large voids are present in the region. The H I mass function for this catalog is presented in a subsequent paper.

A catalog of southern anomalous-velocity H I clouds at decl. < +2° is presented. This catalog is based on data from the H I Parkes All-Sky Survey (HIPASS) reprocessed with the MINMED5 procedure and searched with a new high-velocity cloud-finding algorithm. The improved sensitivity (5 σ: ΔT_B = 0.04 K), resolution (155), and velocity range (-500 km s^-1 < V_LSR < +500 km s^-1) of the HIPASS data result in a substantial increase in the number of individual clouds (1956, as well as 41 galaxies) compared with what was known from earlier southern data. The method of cataloging the anomalous-velocity objects is described, and a catalog of key cloud parameters, including velocity, angular size, peak column density, total flux, position angle, and degree of isolation, is presented. The data are characterized into several classes of anomalous-velocity H I emission. Most high-velocity emission features are HVCs and have a filamentary morphology and are loosely organized into large complexes extending over tens of degrees. In addition, 179 compact and isolated anomalous-velocity objects, CHVCs, are identified based on their size and degree of isolation. Of the CHVCs originally classified by Braun & Burton, 25% are reclassified based on the HIPASS data. The properties of all the high-velocity emission features and only the CHVCs are investigated, and distinct similarities and differences are found. Both populations have typical H I masses of ~4.5D²_kpc M_⊙ and have similar slopes for their column density and flux distributions. On the other hand, the CHVCs appear to be clustered and the population can be broken up into three spatially distinct groups, while the entire population of clouds is more uniformly distributed with a significant percentage aligned with the Magellanic Stream. The median velocities are V_GSR = -38 km s^-1 for the CHVCs and -30 km s^-1 for all the anomalous-velocity clouds. Based on the catalog sizes, high-velocity features cover 19% of the southern sky, and CHVCs cover 1%.

A blind survey for H I–bright galaxies in the southern zone of avoidance (212° ≤ l ≤ 36°, |b| ≤ 5°) has been made with the 21 cm multibeam receiver on the Parkes 64 m radio telescope. The survey, sensitive to normal spiral galaxies to a distance of ~40 Mpc and more nearby dwarfs, detected 110 galaxies. Of these, 67 have no counterparts cataloged in the NASA/IPAC Extragalactic Database. In general, the uncataloged galaxies lie behind thicker obscuration than do the cataloged objects. All the newly discovered galaxies have H I flux integrals that are more than an order of magnitude lower than those of the Circinus galaxy. The survey recovers the Puppis Cluster and foreground group, and the Local Void remains empty. The H I mass function derived for the sample is satisfactorily fitted by a Schechter function with parameters α = 1.51 ± 0.12, Φ* = 0.006 ± 0.003, and log M* = 9.7 ± 0.10.

We present the first results of a blind H I survey for galaxies in the southern zone of avoidance with a multibeam receiver on the Parkes telescope. This survey is expected to eventually catalog several thousand galaxies within Galactic latitude |b| < 5°, mostly unrecognized before because of Galactic extinction and confusion. We present here the results of the first three detections to have been imaged with the Australia Telescope Compact Array. All the galaxies lie near Galactic longitude 325° and were selected because of their large angular sizes, up to 13. Linear sizes range from 53 to 108 kpc. The first galaxy is a massive 5.7 × 10¹¹ M_⊙ disk galaxy with a faint optical counterpart, SGC 1511.1-5249. The second is probably an interacting group of galaxies straddling the Galactic equator. No optical identification is possible. The third object appears to be an interacting pair of low column density galaxies, possibly belonging to an extended Circinus or Centaurus A galaxy group. No optical counterpart has been seen despite the predicted extinction (A_B = 2.7–4.4 mag) not being excessive. We discuss the implications of the results, in particular, the low H I column densities (~10¹⁹ atoms cm^-2) found for two of the three galaxies.