Data Archive. Observational Status Movies. RM Maps. Radio Reference Frame Database. X-Ray Jet Page. A list covering Jan June can be found below.
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Lister have developed an Adobe flash applet that illustrates the concept of superluminal motion in relativistic jets. The user can set the viewing angle, intrinsic speed Lorentz factor , and distance to the jet, and then watch how a luminous relativistic object effectively chases its own light signals to give the illusion of superluminal transverse motion. You will need a copy of Adobe Flash player to run the simulation.
Phys , M. Aller Feb. Savolainen Feb - continues: Seminar series is being organized by Y. Homan Feb Valencia Univ. Lister Jan Classroom visit to Mrs. Homan Nov. Kadler Jan Erlangen Univ. Homan Feb. Their lengths can reach several thousand  or even hundreds of thousands of light years.
If the jet is oriented along the line of sight to Earth, relativistic beaming will change its apparent brightness. The mechanics behind both the creation of the jets   and the composition of the jets  are still a matter of much debate in the scientific community; it is hypothesized that the jets are composed of an electrically neutral mixture of electrons , positrons , and protons in some proportion. A relativistic jet emitted from the AGN of M87 is traveling at speeds between four and six times the speed of light.
While it accurately describes the speeds measured, scientists still believe the actual speed falls just below the speed of light. At these speeds the clouds nearly keep pace with the light they emit as they move towards Earth, so when the light finally reaches us, the motion appears much more rapid than the speed of light. Since the moving clouds travel slightly slower than the speed of light, they do not actually violate Einstein's theory of relativity which sets light as the speed limit.
At right is an image indicating the range of cosmic-ray energies. The flux for the lowest energies yellow zone is mainly attributed to solar cosmic rays, intermediate energies blue to galactic cosmic rays, and highest energies purple to extragalactic cosmic rays. In March it was announced that active galactic nuclei are not responsible for most gamma-ray background radiation. Possibilities include star forming galaxies, galactic mergers, and yet-to-be explained dark matter interactions. Most gamma-ray emitting sources are actually gamma-ray bursts, objects which only produce gamma radiation for a few milliseconds to thousands of seconds before fading away.
These steady gamma-ray emitters include pulsars, neutron stars , and black hole candidates such as active galactic nuclei. For active galactic nuclei AGNs "bright jet features typically exhibit apparent superluminal speeds and accelerated motions. AGN "jets with the fastest superluminal speeds all tend to have high Doppler boosted radio luminosities. The AGN showing superluminal motion in B are . The second image at right is of apparent superluminal motion in NGC In both of these images the apparent motion is rectilinear or close to it.
NGC is a low-luminosity radio galaxy. The third image at right shows the approximate radial motion of the jet component versus the core. The small velocities and core separations of these moving components may indicate that the core is not a stable reference point in these two jets. The "the apparent inward motion [ The picture shows the variable parsec-scale structure of the jet in this active galactic nucleus.
The features observed correspond to ejected plasma regions traveling at relativistic speeds. Those appear to be larger than the speed of light due to projection effects. The sixteen images are spaced by their relative time intervals. The images show that a major radio flux-density outburst in was followed by a particularly bright plasma ejection associated with a superluminal jet component.
This major event was followed by trailing features in its evolution. A similar event is seen after mid The jet dynamics in this source is revealed: a plasma injection into the jet beam leads to the formation of multiple shocks that travel at different speeds downstream ranging from 3c to 6c and interact with each other and with the ambient medium. This is in agreement with numerical relativistic magnetohydrodynamic structural and emission simulations of jets.
The observing runs usually last 8 hr and the total observing time on source is approximately 50 minutes. The images are convolved with a common restoring beam of 0. The image alignment is arbitrary to the brightness peak. The superluminal speeds of the features in the jet were determined from a detailed analysis of multiple Gaussian model fits to the observed visibilities. The warm—hot intergalactic medium WHIM refers to a sparse, warm-to-hot 10 5 to 10 7 K plasma that [may] exist in the spaces between galaxies and This was detected in the 0. Within the WHIM, gas shocks are created as a result of active galactic nuclei , along with the gravitationally-driven processes of merging and accretion.
Part of the gravitational energy supplied by these effects is converted into thermal emissions of the matter by collisionless shock heating. Some of the dark-matter concentrations are massive enough to spark star formation. Thousands of clumps of dark matter coexist with our Milky Way galaxy, shown in the center of the top panel.
The green blobs in the middle panel are those dark-matter chunks massive enough to obtain gas from the intergalactic medium and trigger ongoing star formation, eventually creating dwarf galaxies. In the bottom panel, the red blobs are ultra-faint dwarf galaxies that stopped forming stars long ago. Shown here are VLT observations from , and , coloured blue, green and red respectively. Due to its distance, and the fact that we see the orbit at a steep angle as the cloud falls towards the black hole, only the position, not the shape, of the cloud can be discerned in this image.
The stretching of the cloud is seen in observations of its velocity, which allow astronomers to work out where on its orbit the different parts of the cloud are now located. These observations show how a gas cloud [in the left image] now passing close to the supermassive black hole at the centre of the galaxy is being ripped apart. The horizontal axis shows the extent of the cloud along its orbit and the vertical axis shows the velocities of different parts of the cloud. The horizontal axis shows the extent of the cloud along its orbit and the vertical axis shows the velocities of different parts of the cloud during the last ten years.
By studying the inner regions of the galaxy with Chandra, scientists estimated the rate at which gas is falling toward the galaxy's supermassive black hole. These data also allowed an estimate of the power required to produce the bubbles, which are each about 10, light years in diameter. Surprisingly, the analysis indicates that most of the energy released by the infalling gas goes into producing jets of high-energy particles that create the huge bubbles, rather than into an outpouring of light as observed in many active galactic nuclei.
At right is a "[c]olour-composite image of the central 5, light-years wide region of the spiral galaxy NGC [45 million light years away], obtained with the NACO adaptive optics on the VLT. More than star forming regions - white spots in the image - are distributed along a ring of dust and gas in the image. At the centre of the ring there is a bright central source where the active galactic nucleus and its super-massive black hole are located.
The image was constructed by stacking J- blue , H- green , and Ks-band red [infrared] images. North is up and East is to the left. The field of view is 24 x 29 arcsec2, i. NGC is an elliptical galaxy of the Hubble type E4 pec in the constellation Eridanus south of the ecliptic. The galaxy has an angular extent of 3. It is about million light years away from the solar system and has a diameter of about , light years.
I had the usual trouble with this one trying to balance the colors while making the illuminated filaments easy to discern. In many galaxies, the details near the nucleus are not so important to convey, and it is therefore ok if it's all a bright ball. Here, the image is quite dark to accommodate the details in the core. Such nuances are picked out relatively easily by comparing spectroscopic results from many different galaxies.
- Are You Listening?;
- Acceleration and Collimation Mechanisms in Jets - R. Blandford?
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Spectroscopy is kind of like a fingerprint in light, and whatever spikes and dips in the graph appear tell a story about how far the light traveled, what elements are present, and what's happening to those elements. Would you believe that spectroscopy can also tell us this? This is moving into the realm of things I don't understand well enough to explain, but here are a number of papers specifically on the case of this galaxy.
With that in mind, colors are as follows:" . It is To begin with, it is a pure-disc galaxy. Like other spirals, it has a flat disc permeated by dark lanes of material and with prominent spiral arms where young stars are forming in clusters the blue dots seen in the image. In this image, it is clear that there is simply a brightening to the centre, but no actual bulge like the one in NGC eso , for example.
NGC is also interesting as it is believed to have an active supermassive black hole at its centre that is engulfing matter and producing radiation. This is somewhat unusual because most of these so-called active galactic nuclei exist in galaxies with prominent bulges. In this particular case, the supermassive black hole is thought to have a relatively small mass, of around 20 times that of the Sun.
Another interesting feature is that there are also thought to be two smaller black holes, with masses of a few thousand times that of the Sun, near the nucleus of the galaxy.
Therefore, NGC is an extremely interesting object which, despite not having a central bulge, has a system of three black holes in its central region. This galaxy is located in the constellation of Hydra The Sea Snake and can be seen with a moderate-sized telescope. A number of bright foreground stars that belong to our own Milky Way are also visible. Image on the right is just a cool looking lenticular galaxy in the archive. It was shaped something like a TIE fighter but it turns out the ring goes all the way around. This is only the central part.
Another ring of matter encircles the galaxy further out of the frame. Here is a complete image and interesting accompanying arguments about the actual shape of the galaxy. Can you tell just from looking at it what its three dimensional shape is? Is it a oblique disk, an oblate sphere, or a combination of the two? Since this is an infrared image, the spiral structures visible in image at the link in the above paragraph are not visible in this image. Data is from proposal StSci. ID Active Galactic Nuclei in nearby galaxies: a new view of the origin of the radio-loud radio-quiet dichotomy?
This image, like all high resolution channel images, has a relatively small field of view: only around 25 by 25 arcseconds. Studies of the galaxy by the Spitzer Space Telescope revealed a relatively young million years stellar population within the galaxy's nucleus, which may have originated through the interaction with NGC compressing gas and dust in that region, triggering a starburst. By the galaxy morphological classification, this is an unbarred lenticular galaxy with tightly-wound spiral arms, while shell and tidal tail features suggest that it has undergone a cosmologically-recent merger or interaction event.
Observation of NGC during the s with radio telescopes showed an enhanced level of radio emission. There is "a clumpy gas stream flowing quickly outwards and blocking 90 percent of the X-rays emitted by the black hole. This activity could provide insights into how supermassive black holes interact with their host galaxies. An AGN is a compact region at the centre of a galaxy that has a much higher than normal luminosity. The high level of radiation, sometimes across the whole of the electromagnetic spectrum, is thought to be a result the supermassive black hole at the centre pulling in mass from the surroundings.
It tells us more about the powerful ionised winds that allow supermassive black holes in the nuclei of active galaxies to expel large amounts of matter. In larger quasars than NGC , these winds can regulate the growth of both the black hole and its host galaxy. The disc is heated so much that it emits X-rays, near to the black hole, and less energetic ultraviolet radiation further out.
The ultraviolet radiation can create winds strong enough to blow gas away from the black hole, which otherwise would have fallen into it. But, the winds only come into existence if their starting point is shielded from X-rays. The newly discovered gas stream in the archetypal Seyfert galaxy NGC — one of the best-studied sources of this type over the past half-century — absorbs most of the X-ray radiation before it reaches the original cloud, shielding it from X-rays and leaving only the ultraviolet radiation. The same stream shields gas closer to the accretion disc.
Geometry transition detected in nearby active galactic nuclei jets
This makes the strong winds possible, and it appears that the shielding has been going on for at least three years. We saw signatures of much colder gas than was present before, indicating that the wind had cooled down, due to a strong decrease in the ionising X-ray radiation from the nucleus. But, a new wind has arisen which is much stronger and faster than the persistent wind.
The new gas outflow blocks 90 percent of the low-energy X-rays that come from very close to the black hole, and it obscures up to a third of the region that emits the ultraviolet radiation at a distance of a few light-days from the black hole. UGC is classified as an active galaxy, which means that it hosts an active galactic nucleus.
As this black hole devours the surrounding matter it emits intense radiation, causing it to shine brightly. The galaxy essentially acts as a giant astronomical laser that spews out light at microwave, not visible, wavelengths — this type of object is dubbed a megamaser maser being the term for a microwave laser. Megamasers such as UGC can be some million times brighter than masers found in galaxies like the Milky Way.
It has two channels that detect and process different light, allowing astronomers to study a remarkable range of astrophysical phenomena; for example, the UV-visible channel can study galaxies undergoing massive star formation, while the near-infrared channel can study redshifted light from galaxies in the distant Universe. Such multi-band imaging makes Hubble invaluable in studying megamaser galaxies, as it is able to untangle their intriguing complexity. Not only do the galaxies and black holes seem to co-exist, they are apparently inextricably linked in their evolution.
To better understand this symbiotic relationship, scientists have turned to rapidly growing black holes -- so-called active galactic nucleus AGN -- to study how they are affected by their galactic environments. This means in optical light telescopes, like the VLT, there is little to see. X-rays and infrared light, however, can penetrate this veil of material and reveal the light show that is generated as material heats up before falling onto the black hole seen as a bright point-like source. Where, then, does the food supply for this black hole come from? The answer lies with its partner galaxy, NGC These two galaxies are in the process of undergoing a collision, and the gravitational attraction from IC has likely pulled over some of NGC 's deep reservoir of cold gas seen prominently in the Spitzer data , providing a new fuel supply to power the giant black hole.
Apparent superluminal motion was detected during observations first made in in a jet of material departing from the quasar. Broderick from simulated data. Especially intense and luminous galactic centers are known as active galactic nuclei.
They are in turn thought to be driven by the presence of supermassive black holes, which drag surrounding material inwards and spit out bright jets and radiation as they do so. This constant is named after the astronomer whose observations were responsible for the discovery of the expanding universe and after whom the Hubble Space Telescope was named, Edwin Hubble.
The galaxy lies 13 million light-years away in the southern constellation Circinus. AGN have the ability to remove gas from the centers of their galaxies by blowing it out into space at phenomenal speeds. Astronomers studying the Circinus galaxy are seeing evidence of a powerful AGN at the center of this galaxy as well. The larger outer ring extends off the image and is in the plane of the galaxy's disk. Both rings are home to large amounts of gas and dust as well as areas of major "starburst" activity, where new stars are rapidly forming on timescales of 40 - million years, much shorter than the age of the entire galaxy.
The black hole and its accretion disk are expelling gas out of the galaxy's disk and into its halo the region above and below the disk. The detailed structure of this gas is seen as magenta-colored streamers extending towards the top of the image. The structure appears whitish-pink in this composite image, made up of four filters. Two filters capture the narrow lines from atomic transitions in oxygen and hydrogen; two wider filters detect green and near-infrared light.
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In the narrow-band filters, the V-shaped structure is very pronounced. This region, which is the projection of a three-dimensional cone extending from the nucleus to the galaxy's halo, contains gas that has been heated by radiation emitted by the accreting black hole. A "counter-cone," believed to be present, is obscured from view by dust in the galaxy's disk.
Ultraviolet radiation emerging from the central source excites nearby gas causing it to glow. The excited gas is beamed into the oppositely directed cones like two giant searchlights. As a result, the galaxy went unnoticed until about 25 years ago. Named by astronomer Paul Hickson in , this is the 59th such collection of galaxies in his catalogue of unusually close groups.
What makes this image interesting is the variety on display. There are two large spiral galaxies, one face-on with smooth arms and delicate dust tendrils, and one highly inclined, as well as a strangely disorderly galaxy featuring clumps of blue young stars. We can also see many apparently smaller, probably more distant, galaxies visible in the background. Hickson groups display many peculiarities, often emitting in the radio and infrared and featuring active star-forming regions.
In addition their galaxies frequently contain Active Galactic Nuclei powered by supermassive black holes, as well large quantities of dark matter. The total exposure times per filter were 57 minutes, 41 minutes and 35 minutes respectively. The field of view is about 3. In order to make this a blind test, the team modelled and removed the active nucleus which normally appears as a bright spot from each galaxy, and then cosmetically added a similar mark to the galaxies without an AGN, to make them visually indistinguishable. This explains the black dot visible near the centre of each of these images.
This means that processes other than galactic mergers must trigger AGN activity. At the moment, more than astronomers around the world actively contribute to the project. The project's primary goal is to study the relationship between large scale structure LSS in the universe and dark matter, the formation of galaxies, and nuclear activity in galaxies.
This includes careful analysis of the dependence of galaxy evolution on environment. In the upper part of the frame, the light from distant galaxies has been smeared and twisted into odd shapes, arcs, and streaks. This phenomenon indicates the presence of a giant galaxy cluster, which is bending the light coming from the galaxies behind it with its monstrous gravitational influence. The SDSS uses a 2.
This particular cluster was part of the Sloan Giant Arcs Survey SGAS , which detected galaxy clusters with strong lensing properties; their gravity stretches and warps the light of more distant galaxies sitting behind them, creating weird and spectacular arcs such as those seen here. This study found the star formation rate in these galaxies to be low, which is consistent with models that suggest that most stars in such galaxies form very early on. These BCGs also emit strong radio signals thought to be from active galactic nuclei AGN at their centers, suggesting that the activity from both the AGN and any ongoing star formation is fuelled by cold gas found within the host galaxies.
The enormous gravitational influence of the cluster warps the very shape and fabric of its environment the spacetime around it creating an effect known as strong gravitational lensing. Through this the light from background galaxies in the line of sight to the observer are bent into fantastic arcs. This effect is very useful for studying distant background galaxies. Typically located in the centres of their clusters, BCGs are among the most massive and luminous galaxies in the Universe.
They are generally huge elliptical galaxies and are likely to host active galactic nuclei AGN in their cores. The study found evidence to suggest that BCGs are fueled by cold gas from the galaxy. Violent, gas-rich major mergers can trigger intense bursts of star formation in their aftermath. Scientists believe these two outflows of material are the result of the black hole burping out material after two different feeding events. The first outburst created the fading southern relic: a cone of gas measuring 33 light-years across.
Around years later, a second burst spawned the more compact and radiant outflow emanating from the top of the galaxy: a cone of shocked gas some light-years across. The view covers a portion of the southern field of a large galaxy census called the Great Observatories Origins Deep Survey GOODS , a deep-sky study by several observatories to trace the formation and evolution of galaxies.
Such a detailed multi-color view of the universe has never before been assembled in such a combination of color, clarity, accuracy, and depth. The image reveals galaxy shapes that appear increasingly chaotic at each earlier epoch, as galaxies grew through accretion, collisions, and mergers. The galaxies range from the mature spirals and ellipticals in the foreground, to smaller, fainter, irregularly shaped galaxies, most of which are farther away, and therefore existed farther back in time. These smaller galaxies are considered the building blocks of the larger galaxies we see today.
The closest galaxies seen in the foreground emitted their observed light about a billion years ago. The farthest galaxies, a few of the very faint red specks, are seen as they appeared more than 13 billion years ago, or roughly million years after the Big Bang. This mosaic spans a slice of space that is equal to about a third of the diameter of the full Moon 10 arcminutes. Ultraviolet light taken by WFC3 shows the blue glow of hot, young stars in galaxies teeming with star birth.
The orange light reveals the final buildup of massive galaxies about 8 billion to 10 billion years ago. The near-infrared light displays the red glow of very distant galaxies — in a few cases as far as 12 billion to 13 billion light-years away — whose light has been stretched, like a toy Slinky, from ultraviolet light to longer-wavelength infrared light due to the expansion of the universe.
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WFC3 peered deeper into the universe in this study than comparable near-infrared observations from ground-based telescopes. This set of unique new Hubble observations reveals galaxies to about 27th magnitude in brightness over a factor of 10 in wavelength. That's over million times fainter than the unaided eye can see in visual light from a dark ground-based site.
Wisconsinian glacial began at 80, yr BP. The "emission phenomena observed in active galactic nuclei [includes] the production of compact radio sources separating at superluminal speeds". Outbursts "of cosmic ray electrons from the Galactic Center [may] penetrate the Galaxy relatively undamped and [may be able] to have a major impact on the Solar System through their ability to vaporize and inject cometary material into the interplanetary environment.
Validation and potential of polarimetric MEM imaging  is shown in the image at right. MEM and CLEAN images reconstructed at the optimum beam sizes for each technique and the nominal beam size demonstrate that polarimetric MEM achieves superior resolution and image fidelity. Baselines to ALMA are shown in red. ALMA baselines extend north-south coverage and are especially important for southern sources, where they fill in a large gap in the u, v plane between the intra—northern hemisphere baselines and the very long baselines to the South Pole Telescope.
CHIRP is more robust as the signal-to-noise ratio of the simulated data is lowered. For the second image down on the left, "EHT 1. Image stacking is a procedure used to detect emission from objects that is too faint to be detected in single images.