HIPASS
Encyclopedia
The HI Parkes All Sky Survey (HIPASS) was an astronomical survey for neutral atomic hydrogen (HI)
. Data was taken between 1997 and 2002 using the Parkes Observatory
. HIPASS covered 71% of the sky and identified 5317 sources emitting HI's signature wavelength. Discoveries include the Leading Arm of the Magellanic Stream
and gas clouds devoid of star
s.
range of -1,280 to 12,700 km s-1. HIPASS was the first blind HI survey to cover the entire southern sky
.
. The entire Virgo Cluster
region was observed in Northern HIPASS. NHICAT, the catalogue of the northern extension of HIPASS contains 1002 HI sources.
of 13 individual receivers arranged in a hexagonal pattern. Built in a collaboration between numerous institutions, it was funded by the Australian Research Council
(ARC) and the Australia Telescope National Facility
(ATNF) to undertake the HIPASS and ZOA surveys.
. The existence of the Leading Arm is predicted by models of a tidal interaction
between the Magellanic Clouds and the Milky Way.
. It is likely that HIPASS J0731-69 was torn loose from NGC 2442 by a companion.
Hydrogen line
The hydrogen line, 21 centimeter line or HI line refers to the electromagnetic radiation spectral line that is created by a change in the energy state of neutral hydrogen atoms. This electromagnetic radiation is at the precise frequency of 1420.40575177 MHz, which is equivalent to the vacuum...
. Data was taken between 1997 and 2002 using the Parkes Observatory
Parkes Observatory
The Parkes Observatory is a radio telescope observatory, 20 kilometres north of the town of Parkes, New South Wales, Australia. It was one of several radio antennas used to receive live, televised images of the Apollo 11 moon landing on 20 July 1969....
. HIPASS covered 71% of the sky and identified 5317 sources emitting HI's signature wavelength. Discoveries include the Leading Arm of the Magellanic Stream
Magellanic Stream
The Magellanic Stream is a high-velocity cloud of gas connecting the Large and the Small Magellanic Clouds. It came into existence by a near-collision of both galaxies some 2.5 billion years ago.-Discovery and early observations:...
and gas clouds devoid of star
Star
A star is a massive, luminous sphere of plasma held together by gravity. At the end of its lifetime, a star can also contain a proportion of degenerate matter. The nearest star to Earth is the Sun, which is the source of most of the energy on Earth...
s.
Survey
HIPASS observations had a redshiftRedshift
In physics , redshift happens when light seen coming from an object is proportionally increased in wavelength, or shifted to the red end of the spectrum...
range of -1,280 to 12,700 km s-1. HIPASS was the first blind HI survey to cover the entire southern sky
Celestial sphere
In astronomy and navigation, the celestial sphere is an imaginary sphere of arbitrarily large radius, concentric with the Earth and rotating upon the same axis. All objects in the sky can be thought of as projected upon the celestial sphere. Projected upward from Earth's equator and poles are the...
.
Southern Sky observations
Observations of the southern sky started in February 1997, and were completed in March 2000, consisting of 23020 eight-degree scans of each of 9 minutes duration. HICAT, the catalogue of HIPASS, contains 4315 HI sources. HIPASS scanned the entire southern sky five times.Northern Sky observations
Northern HIPASS extended the survey into the northern skyCelestial sphere
In astronomy and navigation, the celestial sphere is an imaginary sphere of arbitrarily large radius, concentric with the Earth and rotating upon the same axis. All objects in the sky can be thought of as projected upon the celestial sphere. Projected upward from Earth's equator and poles are the...
. The entire Virgo Cluster
Virgo Cluster
The Virgo Cluster is a cluster of galaxies whose center is 53.8 ± 0.3 Mly away in the constellation Virgo. Comprising approximately 1300 member galaxies, the cluster forms the heart of the larger Local Supercluster, of which the Local Group is an outlying member...
region was observed in Northern HIPASS. NHICAT, the catalogue of the northern extension of HIPASS contains 1002 HI sources.
Multibeam Receiver
Observations for HIPASS were taken using the Parkes 21 cm Multibeam Receiver. The instrument consists of a Focal Plane ArrayFocal Plane Arrays
Focal Plane Arrays are arrays of receivers placed at the focus of a radio-telescope. Traditional radio-telescopes have only one receiver at the focus of the telescope, but radio-telescopes are now starting to be equipped with focal plane arrays, which are of three different types: multi-beam feed...
of 13 individual receivers arranged in a hexagonal pattern. Built in a collaboration between numerous institutions, it was funded by the Australian Research Council
Australian Research Council
The Australian Research Council is the Australian Government’s main agency for allocating research funding to academics and researchers in Australian universities. Its mission is to advance Australia’s capacity to undertake research that brings economic, social and cultural benefit to the...
(ARC) and the Australia Telescope National Facility
Australia Telescope National Facility
The Commonwealth Scientific and Industrial Research Organisation 's radio astronomy observatories are collectively known as the Australia Telescope National Facility , with the facility supporting Australia's research in radio astronomy....
(ATNF) to undertake the HIPASS and ZOA surveys.
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 cloudsMagellanic Clouds
The two Magellanic Clouds are irregular dwarf galaxies visible in the southern hemisphere, which are members of our Local Group and are orbiting our Milky Way galaxy...
. The existence of the Leading Arm is predicted by models of a tidal interaction
Galactic tide
A galactic tide is a tidal force experienced by objects subject to the gravitational field of a galaxy such as the Milky Way. Particular areas of interest concerning galactic tides include galactic collisions, the disruption of dwarf or satellite galaxies, and the Milky Way's tidal effect on the...
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 2442NGC 2442
NGC 2442 / 2443 is an intermediate spiral galaxy about 50 million light-years away in the constellation Volans. It was discovered by Sir John Herschel. Associated with this galaxy is HIPASS J0731-69, a cloud of gas devoid of any stars...
. It is likely that HIPASS J0731-69 was torn loose from NGC 2442 by a companion.