The H I Parkes All Sky Survey (HIPASS) is a large survey for neutral atomic hydrogen (H I). Most of the data was taken between 1997 and 2002 using CSIRO's 64 m

Parkes Telescope Parkes Observatory is a radio astronomy observatory, located north of the town of Parkes, New South Wales, Australia. It hosts Murriyang, the 64 m CSIRO Parkes Radio Telescope also known as "The Dish", along with two smaller radio telescopes. T ...

. HIPASS covered 71% of the sky and identified more than 5000 galaxies; the major galaxy catalogs are: the "HIPASS Bright Galaxy Catalog" (HIPASS BGC), the southern HIPASS catalog (HICAT), and the northern HIPASS catalog (NHICAT) Discoveries include over 5000 galaxies (incl. several new galaxies), the Leading Arm of the Magellanic Stream and a few gas clouds devoid of

star A star is a luminous spheroid of plasma (physics), plasma held together by Self-gravitation, self-gravity. The List of nearest stars and brown dwarfs, nearest star to Earth is the Sun. Many other stars are visible to the naked eye at night sk ...

Survey

HIPASS covers a

velocity Velocity is a measurement of speed in a certain direction of motion. It is a fundamental concept in kinematics, the branch of classical mechanics that describes the motion of physical objects. Velocity is a vector (geometry), vector Physical q ...

range of −1,280 to 12,700 km/s. It was the first blind HI survey to cover the entire

southern sky The southern celestial hemisphere, also called the Southern Sky, is the southern half of the celestial sphere; that is, it lies south of the celestial equator. This arbitrary sphere, on which seemingly fixed stars form constellations, appears ...

and the northern sky up to +25°. Technical overview, calibration and imaging (Barnes et al. 2001).

Southern Sky observations

Observations of the southern sky started in February 1997, and were completed in March 2000, consisting of 23,020 eight-degree scans of each of 9 minutes duration. HIPASS scanned the entire southern sky five times. The southern HIPASS galaxy catalog (HICAT) contains 4315 HI sources.

Northern Sky observations

Northern HIPASS extended the survey into the

northern sky The northern celestial hemisphere, also called the Northern Sky, is the northern half of the celestial sphere; that is, it lies north of the celestial equator. This arbitrary sphere appears to rotate westward around a polar axis due to Earth' ...

. The entire

Virgo Cluster The Virgo Cluster is a cluster of galaxies whose center is 53.8 ± 0.3 Mly (16.5 ± 0.1 Mpc) away in the Virgo constellation. Comprising approximately 1,300 (and possibly up to 2,000) member galaxies, the cluster forms the heart of the larger ...

region was observed in Northern HIPASS. NHICAT, the catalogue of the northern extension of HIPASS contains 1,002 H I sources.

CHIPASS

Archival data from HIPASS and the HI Zone of Avoidance (HIZOA) survey were reprocessed to make a new 20cm confusion-limited continuum map of the sky south of

declination In astronomy, declination (abbreviated dec; symbol ''δ'') is one of the two angles that locate a point on the celestial sphere in the equatorial coordinate system, the other being hour angle. The declination angle is measured north (positive) or ...

+25°. Its relatively high sensitivity and resolution (compared to other single-dish surveys) and low level of artefacts has made this survey invaluable, particularly for merging with interferometric data such as

WALLABY A wallaby () is a small or middle-sized Macropodidae, macropod native to Australia and New Guinea, with introduced populations in New Zealand, Hawaii, the United Kingdom and other countries. They belong to the same Taxonomy (biology), taxon ...

to improve the coverage of extended structure.

Multibeam Receiver

Observations for HIPASS were taken using the Parkes 21-cm Multibeam Receiver. The instrument consists of a

focal-plane array A staring array, also known as staring-plane array or focal-plane array (FPA), is an image sensor consisting of an array (typically rectangular) of light-sensing pixels at the focal plane of a lens. FPAs are used most commonly for imaging purpos ...

of 13 individual receivers arranged in a hexagonal pattern. Built in a collaboration between numerous institutions, it was funded by the

Australian Research Council The Australian Research Council (ARC) is the primary non-medical research funding agency of the Australian Government, distributing more than in grants each year. The Council was established by the ''Australian Research Council Act 2001'', ...

(ARC) and the

Australia Telescope National Facility The Commonwealth Scientific and Industrial Research Organisation (CSIRO)'s radio astronomy observatories are collectively known as the Australia Telescope National Facility (ATNF), with the facility supporting Australia's research in radio astrono ...

(ATNF) to undertake the HIPASS and ZOA surveys.

Discoveries

Leading arm of Magellanic Stream

HIPASS discovered the Leading Arm of the Magellanic Stream. This is an extension of the Magellanic Stream beyond the

Magellanic clouds The Magellanic Clouds (''Magellanic system'' or ''Nubeculae Magellani'') are two irregular dwarf galaxies in the southern celestial hemisphere. Orbiting the Milky Way galaxy, these satellite galaxies are members of the Local Group. Because both ...

. The existence of the Leading Arm is predicted by models of a tidal interaction between the Magellanic Clouds and the Milky Way.

HIPASS J0731-69

HIPASS J0731-69 is a cloud of gas devoid of any stars. It is associated with the asymmetric spiral galaxy

NGC 2442 In contemporary history, the third millennium is the current millennium in the ''Anno Domini'' or Common Era, under the Gregorian calendar. It began on 1 January 2001 ( MMI) and will end on 31 December 3000 ( MMM), spanning the 21st to 30th ...

. It is likely that HIPASS J0731-69 was torn loose from NGC 2442 by a companion.

HIPASS J1712-64

HIPASS J1712-64 is an isolated extragalactic cloud of neutral hydrogen with no associated stars. The cloud is a binary system and is not dense enough to form stars. HIPASS J1712-64 was probably ejected during an interaction between the Magellanic clouds and the Milky way.

New galaxies in the Centaurus A/M83 Group

Ten new galaxies were identified in the

Centaurus A/M83 Group The Centaurus A/M83 Group is a complex group of galaxies in the constellations Hydra, Centaurus, and Virgo. The group may be roughly divided into two subgroups. The Cen A Subgroup, at a distance of 11.9 Mly (3.66 Mpc), is centered on Centaur ...

, bringing the total (at the time) to 31 galaxies.

References

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