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Hipass On Board Unit
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. 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 stars. Survey HIPASS covers a velocity range of −1,280 to 12,700 km/s. It was the first blind HI survey to cover the entire southern sky 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 durat ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Astronomical Survey
An astronomical survey is a general map or image of a region of the sky (or of the whole sky) that lacks a specific observational target. Alternatively, an astronomical survey may comprise a set of images, spectra, or other observations of objects that share a common type or feature. Surveys are often restricted to one band of the electromagnetic spectrum due to instrumental limitations, although multiwavelength surveys can be made by using multiple detectors, each sensitive to a different bandwidth. Surveys have generally been performed as part of the production of an astronomical catalog. They may also search for transient astronomical events. They often use wide-field astrographs. Scientific value Sky surveys, unlike targeted observation of a specific object, allow astronomers to catalog celestial objects and perform statistical analyses on them without complex corrections for selection effects. In some cases, an astronomer interested in a particular object will find tha ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Widefield ASKAP L-Band Legacy All-Sky Blind Survey
The Widefield ASKAP L-band Legacy All-sky Blind surveY (WALLABY) is a next-generation survey of the 21 cm radio emission from neutral hydrogen (HI) in the Local Universe. It is hosted by the Australian Square Kilometer Array Pathfinder (ASKAP) telescope, WALLABY will survey three-quarters of the sky over a Declination range −90° to +30° to a redshift of 0.26. It will have a angular resolution of 30 arcsec and a sensitivity of 1.6 mJy/beam in each 4 km/s channel. WALLABY is expected to detect about 500,000 galaxies with a mean redshift of 0.05, at a mean distance of about 200 Mpc. The scientific goals of WALLABY include: * a census of gas-rich galaxies in the vicinity of the Local Group; * a study of the HI properties of galaxies, groups and clusters, including the influence of the environment on galaxy evolution; History The WALLABY project was proposed in 2009 by a team led by B. S. Koribalski and L. Staveley-Smith. It was ranked by ASKAP in the top two of t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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 Centaurus A, a nearby radio galaxy. The M83 Subgroup, at a distance of 14.9 Mly (4.56 Mpc), is centered on the Messier 83 (M83), a face-on spiral galaxy. This group is sometimes identified as one group and sometimes identified as two groups. Hence, some references will refer to two objects named the ''Centaurus A Group'' and the ''M83 Group''. However, the galaxies around Centaurus A and the galaxies around M83 are physically close to each other, and both subgroups appear not to be moving relative to each other. The Centaurus A/M83 Group is part of the Virgo Supercluster, the local supercluster of which the Local Group is an outlying member. Members Member identification The brightest group members were frequently identified in early gala ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
NGC 2442
In contemporary history, the third millennium of the anno Domini or Common Era in the Gregorian calendar is the current millennium spanning the years 2001 to 3000 ( 21st to 30th centuries). Ongoing futures studies seek to understand what is likely to continue and what could plausibly change in the course of this period and beyond. Predictions and forecasts not included on this timeline * List of future astronomical events ** List of lunar eclipses in the 21st century ** List of solar eclipses in the 21st century * Projections of population growth * Climate change ** Representative Concentration Pathway ** Shared Socioeconomic Pathways * Extinction * List of dates predicted for apocalyptic events * Predictions and claims for the Second Coming * Near future in fiction * Works falling into the public domain in the United States 21st century 2000s * See: 2001 * 2002 * 2003 * 2004 * 2005 * 2006 * 2007 * 2008 * 2009 2010s * See: 2010 * 2011 * 2012 * 2013 * 2014 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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 Oort cloud of the Solar System. Effects on external galaxies Galaxy collisions Tidal forces are dependent on the gradient of a gravitational field, rather than its strength, and so tidal effects are usually limited to the immediate surroundings of a galaxy. Two large galaxies undergoing collisions or passing nearby each other will be subjected to very large tidal forces, often producing the most visually striking demonstrations of galactic tides in action. Two interacting galaxies will rarely (if ever) collide head-on, and the tidal forces will distort each galaxy along an axis pointing roughly towards and away from its perturber. As the two galaxies briefly orbit each other, thes ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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 show signs of a bar structure, they are often reclassified as Magellanic spiral galaxies. The two galaxies are: * Large Magellanic Cloud (LMC), approximately 163,000 light-years away * Small Magellanic Cloud (SMC), approximately 206,000 light years away Magellanic clouds are visible to the unaided eye in the Southern Hemisphere but they cannot be observed from the most northern latitudes. History The Magellanic Clouds have been known since ancient times to indigenous peoples across South America and Africa, and from the first millennium in Western Asia. The first preserved mention of the Large Magellanic Cloud is believed to be in petroglyphs and rock drawings found in Chile. They may be the objects mentioned by the polymath Ibn Qutay ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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 astronomy. It is part of CSIRO's business unit known as CSIRO Space and Astronomy.. CSIRO currently operates four observatories as part of the ATNF. Three are in New South Wales near the towns of Parkes, Coonabarabran and Narrabri.The fourth telescope, the next generation Australian Square Kilometre Array Pathfinder (ASKAP) is located at the Murchison Radio-astronomy Observatory in Western Australia. These telescopes can be used together as a long baseline array for use in Very Long Baseline Interferometry. Radio telescopes included in the ATNF: * The Australia Telescope Compact Array * The Parkes Observatory * The Mopra Observatory * The Australian Square Kilometre Array Pathfinder See also * Australian Space Agency * List of radio telescope ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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'', and provides competitive research funding to academics and researchers at Australian universities. Most health and medical research in Australia is funded by the more specialised National Health and Medical Research Council (NHMRC), which operates under a separate budget. ARC does not directly fund researchers, but however allocates funds to individual schemes with specialised scopes, such as Discover (fundamental and empirical research) and Linkage (domestic and international collaborative projects). Most of these schemes fall under the National Competitive Grants Program (NCGP), whereby institutions must compete amongst each other for funding. ARC also administers the Excellence in Research for Australia framework (ERA), which provides ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Focal-plane Array (radio Astronomy)
Focal-plane arrays (FPAs) are widely used in radio astronomy. FPAs are arrays of receivers placed at the focus of the optical system in a radio-telescope. The optical system may be a reflector or a lens. 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 arrays, bolometer arrays, and the experimental phased-array feeds. Multi-beam feed arrays Multi-beam feed arrays consist of a small array of feed horns at the focus of a radio-telescope. Each feed horn is connected to a receiver to measure the received power and each horn and receiver pair is sensitive to radio waves from a slightly different direction in the sky. A feed array with receivers will increase the survey speed of the telescope by a factor of , making them very powerful survey instruments. Because radio wavelengths are large, the resulting feed arrays are among ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Angular Resolution
Angular resolution describes the ability of any image-forming device such as an optical or radio telescope, a microscope, a camera, or an eye, to distinguish small details of an object, thereby making it a major determinant of image resolution. It is used in optics applied to light waves, in antenna theory applied to radio waves, and in acoustics applied to sound waves. The colloquial use of the term "resolution" sometimes causes confusion; when an optical system is said to have a high resolution or high angular resolution, it means that the perceived distance, or actual angular distance, between resolved neighboring objects is small. The value that quantifies this property, ''θ,'' which is given by the Rayleigh criterion, is low for a system with a high resolution. The closely related term spatial resolution refers to the precision of a measurement with respect to space, which is directly connected to angular resolution in imaging instruments. The Rayleigh criterion shows th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hydrogen Line
The hydrogen line, 21 centimeter line, or H I line is the electromagnetic radiation spectral line that is created by a change in the energy state of neutral hydrogen atoms. This electromagnetic radiation has a precise frequency of , which is equivalent to the vacuum wavelength of in free space. This frequency falls below the microwave region of the electromagnetic spectrum, which begins at 3.0 GHz (10 cm wavelength), and it is observed frequently in radio astronomy because those radio waves can penetrate the large clouds of interstellar cosmic dust that are opaque to visible light. This line is also the theoretical basis of the hydrogen maser. The microwaves of the hydrogen line come from the atomic transition of an electron between the two hyperfine levels of the hydrogen 1 s ground state that have an energy difference of []. It is called the ''spin-flip transition''. The frequency, , of the quantum, quanta that are emitted by this transition between tw ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
