Where results make sense

About us   |   Why use us?   |   Reviews   |   PR   |   Contact us

Radio astronomy - Wikipedia, the free encyclopedia Radio astronomy is the study of celestial phenomena through measurement of the characteristics of radio waves emitted by physical processes occurring in space. A 151 MHz map of the region: 140° to 180° galactic longitude; -5° to 5° galactic latitude from the CLFST at the Mullard Radio Astronomy Observatory. Radio astronomy is also partly responsible for the idea that dark matter is an important component of our universe; radio measurements of the rotation of galaxies suggest that there is much more mass in galaxies than has been directly observed (see Vera Rubin). en.wikipedia.org /wiki/Radio_astronomy   (917 words)

Most distant group of galaxies known in the universe The radio galaxies are amongst the most massive objects in the early Universe and there has long been circumstantial evidence that they are located at the heart of young clusters of galaxies, still in the process of formation. Radio galaxies are therefore potential beacons for pinpointing regions of the Universe in which large galaxies and clusters of galaxies are being formed. To search for galaxies at the same distance as the radio galaxy, the pictures were optimised in sensitivity for the sharp colour emitted by glowing hydrogen gas at the distance of the radio galaxy [2]. www.eurekalert.org /pub_releases/2002-04/eso-mdg040902.php   (1181 words)

Radio Astronomy   (Site not responding. Last check: 2007-10-25) Radio Astronomy is the study of the Universe and astrophysical phenomena, by examining their emission of electromagnetic radiation in the radio portion of the spectrum. Radio astronomy has greatly improved our understanding of the evolution of stars, the structure of galaxies, and the origin of the universe. The low-frequency limit of the radio band is determined by the opacity of the ionosphere, while the high-frequency limit is due to strong absorption from oxygen and water bands in the lower atmosphere. www.kosmoi.com /Science/Astronomy/Radio   (895 words)

Bibliography for "Energy Transport in Radio Galaxies and Quasars" Evidence for a quasar in the radio galaxy Cygnus A from observation of broad-line emission. The head-tail and wide-angle-tail radio galaxies in cluster A 3627. VLBI observations of the nucleus of the radio galaxy Cygnus A. ApJ www.cv.nrao.edu /~azensus/jetwks/alabib.html   (4762 words)

ScienceDaily: Astronomy   (Site not responding. Last check: 2007-10-25) Galaxy formation and evolution: the study of the formation of the galaxies, and their evolution. The existence of Earth's galaxy, the Milky Way, as a separate group of stars was only proven in the 20th century, along with the existence of "external" galaxies, and soon after, the expansion of the universe, seen in the recession of most galaxies from us. Galaxy formation and evolution -- The formation of galaxies is still one of the most active research areas in astrophysics; and, to some extent, this is also true for galaxy... www.sciencedaily.com /encyclopedia/astronomy   (3209 words)

Dott. Daniele Dallacasa   (Site not responding. Last check: 2007-10-25) It is well known that radio galaxies is clusters have quite distinctive properties reflecting the motion of the galaxy across the cluster itself, characterized by a relatively high particle density. Cluster radio galaxies have bent jets and tails where the relativistic electrons flow as the galaxy moves. Radio BL Lac Objects are believed to be low power Fanaroff-Riley I type radio galaxy with the jet aligned to the line of sight. urania.bo.astro.it /dallacasa.htm   (667 words)

STRI the Science and Technology Research Institute at UH   (Site not responding. Last check: 2007-10-25) Radio observations give insight into their complex and disparate structure but cannot on their own tell us much about quantities that interest us as physicists (energetics, internal physical conditions, dynamics and so on). Radio sources can emit X-rays (and optical light) via the synchrotron process, and observations of this process, pioneered by us, have given us new insights into particle acceleration in the jets in low-power radio galaxies: the electrons emitting X-rays have very short radiative lifetimes, so that X-ray emission is a diagnostic of truly As radio lobes are collections of highly energetic particles, it has been clear for many years that there must be a medium outside them that prevents them from expanding rapidly and disappearing. strc.herts.ac.uk /astro/progs/prog_radio.html   (976 words)

Astronomy News & Links: An extremly distant cluster of galaxies at redshift 4.1 An extremly distant cluster of galaxies at redshift 4.1 Following up this conjecture, the Leiden astronomers and their colleagues in the USA and Germany proposed a large observing programme with the ESO VLT at Paranal (Chile) to search for groupings of galaxies in the vicinity of distant radio galaxies that might be the ancestors of rich clusters. To search for galaxies at the same distance as the radio galaxy, the pictures were optimised in sensitivity for the sharp colour emitted by glowing hydrogen gas at the distance of the radio galaxy. www.astrophys.org /news/2002/020409_eso_galaxygroup_mostdistant.html   (1078 words)

A brief description of properties of radio galaxies Ross is asking about unified models for radio galaxies and quasars (though he doesn't realise it.) The number of objects with observed superluminal motion is pretty small, actually, and this is because the measurements are difficult to make; you need more than one epoch of VLBI measurement. When observed on kiloparsec scales in the radio, the first two classes look similar; they both have radio lobes, jets, and a central core or nucleus centred on the host object (an elliptical galaxy in the case of radio galaxies and a quasar in an elliptical in the case of radio-loud quasars). In this case the radio galaxies lie in or near the plane of the sky, and the lobe-dominated quasars lie at a smaller angle to the line of sight. stupendous.rit.edu /richmond/answers/radiogalaxies.html   (465 words)

StarDate Online | Astroglossary | R Radio telescopes show that some radio galaxies, called extended radio galaxies, have lobes of radio emission extending millions of light-years from their nuclei. Radio waves are not harmful to life because they are not strong enough to ionize atoms or destroy cells. Astronomers have used radio telescopes to map the hydrogen content of our galaxy and to discover structures and processes in other galaxies that are invisible to optical telescopes. www.stardate.org /resources/astroglossary/glossary_R.html   (1273 words)

Active Galaxies and Quasars - High-redshift Radio Galaxies   (Site not responding. Last check: 2007-10-25) Among these galaxies, the lowest-redshift examples of 3C 247 an d 3C 337 are the most "normal", much like ellipticals in nearby cluster environments, while the higher-redshift objects such as 3C 368 and 3C68.2 are the strangest by our present-epoch standards. The radio sources all have elongated structures with the brightest parts being twin lobes or "hot spots" of radio emission. It is a remarkable correlation for high-redshift radio galaxies that when the optical galaxy is elongated, it preferentially aligns with the radio source (the "alignment effect"), while there is no such tendency for nearby, lower-power radio galaxies. www.astr.ua.edu /keel/agn/highz.html   (453 words)

Spaceflight Now | Breaking News | Probe proves astronomers fooled by an 'optical illusion' ISO home pageIn their description, radio galaxies and quasars would both be powered by a supermassive fl hole at their centres, surrounded by a wall of dust. Having studied powerful radio sources for more than half a century, astronomers are now certain that a strong radio source is related to the existence of a super-massive fl hole in the centre of a galaxy. But Seyfert 1 galaxies are observed face-on, while Seyfert 2 galaxies are seen at a certain inclination; the internal edge of the doughnut, where the dust is hot and emits strongly in the mid-infrared, is revealed in the Seyfert 1 galaxies, but that same part of the ring is hidden in Seyfert 2 galaxies. www.spaceflightnow.com /news/n0105/23isofooled   (1167 words)

HubbleSite - Release Text about "Hubble Uncovers Surprisingly Complex Structures in Radio Galaxies" The radio galaxies observed are so far away they existed when the universe was half its present age, and the light is only now reaching us. The team is analyzing a sample of 28 radio galaxies that have been imaged by Hubble in visible light, by the Very Large Array Radio Interferometer at radio wavelengths, and by the United Kingdom Infrared Telescope. Previous ground-based observations since 1987 have shown that, in visible light, distant radio galaxies have an unusual elongated structure — unlike the classic spiral and elliptical shapes in normal galaxies — that align to the twin lobes of radio emissions that are the trademark of such active galaxies. www.hubblesite.org /newscenter/archive/1995/30/text   (651 words)

Astrophysicists discover massive forming galaxies The galaxies were grouped around high-red shift radio galaxies, the most massive systems known, suggesting that they all formed at approximately the same time. In the present universe, the most massive galaxies are elliptical galaxies, which are found in the centers of rich galaxy clusters. Earlier sub-millimeter studies of high-red shift radio galaxies have shown that their star-formation rates are large enough to build a massive galaxy. www.eurekalert.org /pub_releases/2003-09/uoc--adm091703.php   (431 words)

Prof. Gabriele Giovannini The study of the parsec scale properties of radio galaxies is crucial to obtain information on the nature of their central engine, and provides the basis ofthe current unified theories, which suggest that the appearance of active galactic nuclei strongly depends on orientation. In some clusters of Galaxies diffuse radio sources, which cannot be obviously associated with the individual galaxies, are present, thus demonstrating the existence of non-thermal processes in the ICM. The formationand evolution of these sources is however still under debate: radio emitting electrons could be reaccelerated cosmic rays, or accelerated from the thermal population, or could be produced as a result of the interaction between cosmic-ray protons and the ICM (secondary electrons models). urania.bo.astro.it /giovannini.htm   (715 words)

Galaxies: Radio Galaxies   (Site not responding. Last check: 2007-10-25) Though the two interacting galaxies are obvious in the optical, one can also see that the southern galaxy is itself interacting, optical filaments being visible to the west, enveloping a nearby companion. The radio observations show what appears to be a bipolar, fairly assymetrical, twin jet radio galaxy, associated with the southern system. The fact that the northern tip of the radio feature appears coincident (though not exactly) with the northern galaxy, may indicate the presence of a one-sided jet from the northen system, or may just be a remarkable coincidence. www.sr.bham.ac.uk /~amr/radiogalaxies.html   (257 words)

The Picture Gallery   (Site not responding. Last check: 2007-10-25) The big radio galaxy on the left is Hydra A. Continuing clockwise are PKS1246-410, 4C26.42, 3C129, PKS0745-191, 3C129.1, 3C84 and 3C295. All of these radio galaxies live in relatively rich clusters of galaxies which partly explains the wide range of morphologies. In fact, all of them are associated with a central dominant elliptical galaxy except for 3C129 which is associated with a more ordinary elliptical galaxy at the periphery of the cluster. www.aoc.nrao.edu /~gtaylor/gallery.html   (312 words)

Curtis Saxton: Research: Extragalactic Jets & AGN In all radio galaxies whose morphology may be the result of jet interactions with an inhomogeneous interstellar medium we expect that the dense clouds will be optically observable as a result of radiative shocks driven by the pressure of the radio cocoon. The results of the simulation are also consistent with other features found in the radio image of Pictor A. This filament arises from the surging behaviour of the jet near the hot-spot; the surging is provoked by alternate compression and decompression of the jet by the turbulent backflow in the cocoon. The “large-scale jet” appearing in the radio images of Morganti and coworkers may be the result of the same pressure gradients that cause the uplift of the thermal gas, acting on much lighter plasma, or may represent a jet that did not turn off completely when the northern middle lobe started to buoyantly rise. www.mssl.ucl.ac.uk /~cjs2/res_jets.html   (1459 words)

Radio Galaxies in VLBI The two-sided parsec-scale emission of the FRII radio galaxy 3C452. To test this hypothesis we need parsec-scale maps of FRI radio galaxies, in order to derive estimates of the intrinsic Lorentz factors for the relativistic plasma, and plausible values for the orientation of the radio emission with respect to the line of sight. If FRI radio galaxies are the parent population of BL Lacertae objects, then we expect relativistic intrinsic speed on the parsec scale. www.ira.cnr.it /~tventuri/vlbi1.html   (545 words)

:: LOFAR - Astronomy Since distant radio galaxies pinpoint proto-clusters, studying the environments of these distant galaxies will constrain the formation of clusters at the earliest epochs. Clusters often contain diffuse radio sources that are shaped by the dynamics of the gas in which they are embedded. Radio images of 4 diffuse radio sources in nearby clusters showing the filamentary structure of the synchrotron emitting plasma shaped by shocks in the cluster gas (Slee et al 2001). www.lofar.org /p/ast_sc_extra.htm   (758 words)

NOAO Scientific Staff He has recently demonstrated that the UV continuum emission from high-redshift radio galaxies is largely non-stellar in origin, and that these radio galaxies harbor hidden quasar nuclei. In addition, he and his collaborators are studying the stellar content and ages of high-redshift galaxies; they have recently discovered a 3.5 Gyr old galaxy at a redshift of z=1.55, which provides a strong constraint on the cosmological parameters. Although the observed optical emission from radio galaxies is non-stellar, the infrared radiation is most likely dominated by starlight, and Dey will investigate the infrared properties of high redshift radio galaxies with the aim of utilizing these luminous galaxies as cosmological probes. www.noao.edu /noao/scistaff/dey.html   (302 words)

ScienceDaily: Astrophysicists Discover Massive Forming Galaxies Galaxy Formation Not Random, Says Astronomer (February 28, 2001) -- Gaze into the vastness of the universe this evening and in all likelihood those galaxies look just as they did five billion years ago, and they didn't get to their locations by random chance, says U... Barred spiral galaxy -- A barred spiral galaxy is a spiral galaxy with a band of bright stars emerging from the center and running across the middle of the... Galaxy -- A galaxy is a huge gravitationally bound system of stars, interstellar gas and dust, plasma, and (possibly) unseen dark matter. www.sciencedaily.com /releases/2003/09/030918092156.htm   (1591 words)

Galaxies The radio emission comes from the core AND from very large regions on either side of the optical part of the galaxy called ``radio lobes''. The radio emission from normal galaxies is thousands to millions of times less intense and is from the gas between the stars. A third type of active galaxy called BL Lacertae objects (BL Lac objects for short) are probably radio galaxies with their jets pointed right at us. www.astronomynotes.com /galaxy/s13.htm   (499 words)

Shocks in powerful radio galaxies   (Site not responding. Last check: 2007-10-25) To investigate the cause of the alignment effect and the ionization mechanism in powerful radio galaxies, we have made a detailed study of a sample of low--intermediate redshift radio galaxies [1] [2] [3] [4]. in all cases the spatial extent of the optical line emission is defined by the boundaries of the expanding radio source. power-law photoionization model (solid line) is in agreement with the observations in the nuclear regions, and also successfully reproduces the line ratios measured in low-redshift radio galaxies. www.shef.ac.uk /~phys/research/astro/papers/shocks   (479 words)

Jodrell Bank - Microquasars, Quasars & Radio Galaxies   (Site not responding. Last check: 2007-10-25) Super-massive fl holes at the heart of galaxies with a mass of up to a billion suns appear to be the cause of the most energetic sources of emission in the Universe. The centres of such galaxies are called Active Galactic Nuclei and when they emit a beam of radiation that points towards us, the intense, often point like objects that we observe are called Quasars. Micro-quasars are objects in our own galaxy which also contain fl holes, but here the fl hole results from the collapse of the core of a massive star at the end of its life. www.jb.man.ac.uk /booklet/Quasars.html   (432 words)

HubbleSite - Hubble Sees Detailed New Structures in Three Radio Galaxies - Image - 8/7/1995   (Site not responding. Last check: 2007-10-25) These Hubble Space Telescope images, combined with radio maps produced by the Very Large Array Radio Interferometer (blue contour lines), show surprisingly varied and intricate structures of gas and stars that suggest the mechanisms powering radio galaxies are more complex than thought previously. The line corresponds to the axis of the galaxy's radio emissions, which unlike other radio galaxies, is in a different direction from the optical region. One of the best studied radio galaxies, this image is composed of a very smooth cigar-shaped emission region closely aligned with the radio axis, upon which is superimposed a string of bright knots that might be stars or dust. www.hubblesite.org /newscenter/newsdesk/archive/releases/1995/30/image/a   (469 words)

Try your search on: Qwika (all wikis)

About us   |   Why use us?   |   Reviews   |   Press   |   Contact us   Copyright © 2005-2007 www.factbites.com Usage implies agreement with terms.