Black Hole Mass Related to Globular Cluster Numbers

A photo of the jet emitted by the black hole in galaxy M87

The mass a supermassive black hole at the center of a large galaxy has appears to be related to the number of globular cluster that particular galaxy contains, a new report suggests.

The data has been derived from a new investigation of the stars, which indicates that the two are somehow linked. The exact mechanisms underlying this connection are still unclear.

There are many such correlations in astronomy, experts say, even if some are arguably clearer than others. Given that the new connection was observed in several cases, scientists will continue to analyze it until they get to the bottom of it.

One interesting aspect of the new discovery is that it holds more value for some galaxies than for others. Astronomers say that finding out precisely why this happens is yet another mystery that needs solving.

In past studies, astrophysicists demonstrated that supermassive black holes exert numerous influences on their host galaxies, including regulating their growth.

In addition, these SMBH can also influence the total amount of dark matter massive galaxies contain, change the brightness of the bulges spiral galaxies have, and influence the masses of these bulges.

But astronomers also know that the luminosity of a galaxy and the amount of dark matter its halo contains are also influenced by the number of globular clusters the cosmic structure contains.

Researchers wanted to learn whether they could eliminate the intermediaries, and still maintain a direct correlation, between the SMBH and the number of clusters.

According to team leaders Andreas Burkert of the Max Planck Institute for Extraterrestrial Physics, in Germany, and Scott Tremaine, at the Princeton University, this is entirely possible.

The discovery hints at a previously-unknown regulation mechanism. It was confirmed in 13 different instances, the research team says.

Details of the investigation will be published in an upcoming issue of the esteemed scientific journal Monthly Notices of the Royal Astronomical Society.

The journal entry also features a follow-up on the original study, which includes case studies of 33 galaxies. Even with these increased number of instances, the correlation holds true.

Interestingly, it was found that the connection is especially true for elliptical galaxies. For lenticular galaxies, the team failed to uncover any correlation.

No reasons as to why that happens have yet been discovered, Universe Today reports.

Galaxies Caught in Massive Display of 'Cannibalism'

Stellar streams around the spiral galaxy M63

Astronomers have recently observed a series of large galaxies as they were consuming smaller versions of themselves, in order to increase their bulk and mass.

The fact that galaxies tend to collide and merge with each other is nothing new, and experts have been observing some of these cosmic events for many years.

One of them, the Antennae Galaxies, are even renowned around the world. They were imaged with Hubble a few years back, and have since become the unofficial symbol of galactic mergers.

At this point, astrophysicists believe that even the Milky Way engaged in such behavior in the past, when it started to gobble up smaller, dwarf galaxies in its surroundings.

Traces of those bodies can still be seen today, in the anomalous behavior and number of star clusters located throughout the galaxy, as well as in the properties of the supermassive black hole at its core.

But the new observations show for the first time galactic cannibalism taking place outside of the Milky Way's local neighborhood.

The research group, led by expert David Martinez-Delgado, found that dwarf galaxies appear to be heavily influenced by these collisions, especially as far as their shapes go.

Massive distortions appear, and some of the most common side effects of mergers include the development of tidal tails and tendrils, that completely surround and grasp the larger galaxy.

Martinez-Delgado, who holds a joint appointment at the Max Planck Institute for Astronomy, in Germany, and the Instituto de Astrofísica de Canarias, in the Spanish Canary Islands, also collaborated with amateur astronomers for the research.

The expert says that the recent investigation proved the existence of galactic mergers in galaxies up to 50 million light-years,Space reports.

According to the research team, it would appear that the tidal tails are produced under the incredibly strong gravitational pull that the larger galaxies exert on the near side of smaller ones.

Their appearance is determined by the fact that stars are more distant from the larger galaxy lag behind those who are closer. The latter travel at much higher speeds.

The new scientific research will be published in the October issue of the esteemed Astronomical Journal.

NGC 300 Imaged in Exquisite Detail

Following an observations campaign that lasted several years, astronomers at ESO finally managed to produce the most accurate and detailed image of the superb spiral galaxy NGC 300.

The formation is located relatively close by, in the Sculptor Group of galaxies, and it is widely considered to be one of the most easy-to-observe structures in the Southern Hemisphere.

The recent image was pieced together from a multitude of different observations, taken over a period of a few years, by experts using numerous color filters.

In total, it took about 50 hours of exposure time to collect the data necessary to create this view. The Wide Field Imager (WFI) at the ESO La Silla Observatory, in Chile, was the main instrument used for the job.

The European Southern Observatory has numerous facilities in Chile, a country that houses parts of the Atacama Desert. This is the most arid desert on the face of the planet, and also one of the driest.

Precipitations here are scarce, and clouds are almost unheard of, and this sets the perfect stage for astronomical observations.

This allowed the WFI to observe NGC 300 in exquisite detail, experts say. Other galaxies in the Sculptor Group that have been imaged using ESO telescopes include NGC 55, NGC 253, and NGC 7793.

Generally, the Group inconspicuous, but it is actually the home of numerous interesting galaxies. NGC 300 is no exception in this regard.

In fact, the thing that makes this galaxy is interesting is not some extreme characteristic, but rather the fact that it's perfectly normal.

Given its similarities to our own Milky Way, experts are analyzing it as a means of deriving more data on our home galaxy as well. We can't get out of the Milky Way yet, but we can observe it from a distance.

“The data was acquired over many observing nights, spanning several years,” the ESO experts say.

“The main purpose of this extensive observational campaign was to take an unusually thorough census of the stars in the galaxy, counting both the number and varieties of the stars, and marking regions, or even individual stars, that warrant deeper and more focused investigation,” they add.

“By observing the galaxy with filters that isolate the light coming specifically from hydrogen and oxygen, the many star-forming regions along NGC 300’s spiral arms are shown with particular clarity in this image as red and pink clouds,” the ESO team concludes.

New Hubble pictures suggest Milky Way fell together

New infrared images of the Milky Way globular cluster 47 Tucanae (this one recorded at a wavelength of 1.6 micrometers), reveal that both the cluster and the Milky Way's central bulge are 11 billion to 12 billion years old and may have formed simultaneously with the Milky Way’s halo.

BALTIMORE — A preliminary analysis of elderly stars in the Milky Way appears to strike a blow against the prevailing theory of galaxy formation. The study suggests that several large and seemingly disparate chunks of the Milky Way galaxy formed at the same time from the collapse of a single blob of gas and dust.

That’s in direct contrast to the leading galaxy-formation scenario, which holds that the Milky Way and other galaxies began small and grew bit by bit for the most part, gravitationally acquiring intergalactic gas and dust and merging with galaxies in their immediate neighborhood.

The new evidence, which astronomers emphasize is only tentative, comes from a new, ongoing study of a familiar globular cluster — a dense, elderly grouping of more than a million Milky Way stars collectively known as 47 Tucanae. Earlier this year, Harvey Richer of the University of British Columbia in Canada and his colleagues began examining 47 Tucanae with two Hubble Space Telescope cameras — the newly installed Wide Field Camera 3 and the Advanced Camera for Surveys, which stopped working early in 2007 but was revived by astronauts during the servicing mission last year.

The cluster lies near but not inside the Milky Way’s bulge, a massive concentration of stars that surrounds the galaxy’s core. But because the cluster shares several properties with the bulge, such as chemical composition and orbital motion, astronomers consider the age of 47 Tucanae a good proxy for that of the bulge.

An analysis of the Hubble portrait, which includes one of the deepest infrared views ever recorded, reveals that 47 Tucanae, and therefore the Milky Way’s bulge, formed between 11 billion and 12 billion years ago, Richer reported May 4 at a symposium on stellar evolution at the Space Telescope Science Institute in Baltimore. He said previous age estimates that did not use the new Hubble camera and put the cluster at a more youthful 9 billion years old are simply not correct.

“This is not a young cluster. That’s definitive,” Richer said. But he cautioned that both the analysis and observations of 47 Tucanae are ongoing, so the precise age determination is still “very preliminary.”

The new age determination places the bulge at roughly the same vintage as the halo of the Milky Way, a vast spherical region that extends to the outskirts of the galaxy and envelops the flattened disk containing the Milky Way’s signature spiral arms,.

Researchers had previously determined the halo’s age by studying several globular clusters that lie within it. The similarity in age of 47 Tucanae and the galactic halo suggests that the two structures may have formed simultaneously, in one giant monolithic gravitational collapse of material, Richer said. “It may have been that major components of the galaxy pretty much formed everywhere at the same time very early on and other bits and pieces came along later,” he noted.

A younger age for the bulge would have indicated that the galaxy grew more gradually and from the outside in, with the halo forming first and the central bulge arising a few billion years later.

But if the age estimate holds up, it would appear to be in conflict with the prescription for galaxy formation dictated by the cold dark matter theory, which holds that galaxies began as small fry that built themselves up by stealing gas and stars from their neighbors.

Evidence that the halo and the bulge of the Milky Way formed together could be seen either as a cosmic coincidence or a finding that suggests some previously unknown episode of violence early in the galaxy’s history, commented Rosie Wyse of Johns Hopkins University in Baltimore, who was not a collaborator on the study.

One possibility, she notes, is that the Milky Way suffered a major collision not long after its birth that drove material from the halo into the central part of the galaxy, forming the bulge. That could also explain why the mass of stars in the bulge is about 10 times heavier than that in the halo, she said.

The finding does not rule out the possibility that parts of the Milky Way grew by accreting, or gravitationally accumulating material, from neighbors, Richer said. Indeed, the Milky Way today continues to grow by pulling in small neighboring galaxies, such as the Sagittarius dwarf galaxy.

New ESO Image Shows Thousands of Galaxies

Astronomers at the European Southern Observatory (ESO) have just released a new spectacular, wide-field image of a very crowded portion of the sky. The photograph covered several thousands of very distant galaxies, according to the team behind the study, as well as a significant group of such structures that are included in the massive Abell 315 galaxy cluster. But the scientists warn that the visible portion of this particular cluster is only the tip of the iceberg. The entire structure is several times more massive, given that much of its content is made up of dark matter.

This is visible when looking at the shape of the galaxies behind it, which appear to be slightly bent. The ESO team also adds that the most of the stars we see in this new image are almost never visible from Earth with the unaided eye. Most of the bright dots we see in the evening sky are actually stars from our own galaxy, the Milky Way, plus a few extra-bright ones from neighboring galaxies such as Andromeda. Other star “collections” emit very small amounts of visible light, and are therefore too dim to be perceived by the human eye.

One interesting thing to note is that, if we were to become capable of seeing this dim light, the radiation coming from distant galaxies would basically cover the sky. Since we don't have that ability, astronomers rely on devices such as the Wide Field Imager instrument. This is located on the MPG/ESO 2.2-meter telescope facility, which is based at the ESO La Silla Observatory, high in the Chilean Andes. For the new image, scientists used three different filters and long exposure times. The composite photography that resulted from this is of both the wide-field and long-exposure kind. The WFI covered an area of the sky about 34x33 arcminutes across.

“Beginning in the center of the image and extending below and to the left, a concentration of about a hundred yellowish galaxies identifies a massive galaxy cluster, designated with the number 315 in the catalog compiled by the American astronomer George Abell in 1958. The cluster is located between the faint, red and blue galaxies and the Earth, about two billion light-years away from us. It lies in the constellation of Cetus (the Whale),” ESO scientists explain in a press release.

“The presence of dark matter is revealed through its gravitational effect: the enormous mass of a galaxy cluster acts on the light from galaxies behind the cluster like a cosmic magnifying glass, bending the trajectory of the light and thus making the galaxies appear slightly distorted. By observing and analyzing the twisted shapes of these background galaxies, astronomers can infer the total mass of the cluster responsible for the distortion, even when this mass is mostly invisible. However, this effect is usually tiny, and it is necessary to measure it over a huge number of galaxies to obtain significant results,” the astronomers add.

Largest Atlas Of Nuclear Galactic Rings Unveiled

An international team of astrophysicists has just unveiled the most complete atlas of nuclear rings, enormous star-forming ring-shaped regions that circle certain galactic nuclei. The catalogue, published in the Monthly Notices of the Royal Astronomical Society, includes 113 such rings in 107 galaxies.

"AINUR (the Atlas of Images of Nuclear Rings) is the most complete atlas of nuclear rings created to date", Sebastien Comeron, a researcher at the Institute of Astrophysics of the Canary Islands (IAC), and co-author of the joint study with other scientists from the universities of La Laguna, Oulu (Finland) and Alabama (United States), tells SINC.

The atlas has just been published in the journal Monthly Notices of the Royal Astronomical Society, and covers 113 nuclear rings in 107 different galaxies. Six are dust rings in elliptical galaxies, while the rest (the majority) are star-forming rings in disc galaxies.

The nuclear rings are ring-shaped, star-forming configurations located around galactic nuclei. They range in size on average from between 500 to 3,000 light years, and they are very bright because they contain an abundance of young stars, including some extremely massive ones. This kind of star has a short lifetime but shines very brightly before exploding as a supernova.

To find the rings, the astrophysicists used images from around 500 galaxies observed by the Hubble space telescope, which belongs to NASA and the European Space Agency, as well as using other references. The images were processed using filters, generating various kinds of maps to help identify the rings more easily.

Rings and Lindblad resonances
"The AINUR atlas has also looked for relationships between the properties of the nuclear rings and those of the galaxies in which they are found", says Comeron, "and we have been able to statistically prove that most rings are associated with Lindblad resonances (gravitational shoves that push objects out of certain orbits and into others)".

The astrophysicists have shown that when the rings are in a barred galaxy (within disc galaxies, which have a central cylinder or 'cigar' of stars), the maximum radius that a nuclear ring can attain is 25% of the length of the bar, and that the maximum radius is inversely proportional to the strength of the bar.

This is the behaviour that was predicted for the internal Lindblad resonances, which are determined by the size of the bar and their strength (how elliptical this is). If the bar is small or very elliptical, the resonance orbit becomes small, but if it is large or not very elliptical, the orbits become bigger.

The researchers also found that, contrary to what had been believed until now, a significant proportion of nuclear rings are to be found in non-barred galaxies (around 20%). The resonances needed to form the rings in these galaxies "are probably created by strong spiral arms, weak oval distortions of the disc and some lesser interaction with neighbouring galaxies", the scientists say.

CSIRO Telescope Spots Mega-Star Cradle

Mid-infrared image of BYF 73 from NASA's Spitzer Space Telescope. The yellowish wisps to the right are remnants of gas that have been heated and are being driven off by the massive young stars within them (seen in blue). The large-scale collapse of colder gas to form a massive cluster is centred around the bright stars just to the left of the heated wisps. Image credit - NASA/JPL-Caltech

Using a CSIRO radio telescope, an international team of researchers has caught an enormous cloud of cosmic gas and dust in the process of collapsing in on itself - a discovery which could help solve one of astronomy's enduring conundrums: 'How do massive stars form?'

Dr Peter Barnes from the University of Florida says astronomers have a good grasp of how stars such as our Sun form from clouds of gas and dust, but for heavier stars - ten times the mass of the Sun or more - they are still largely in the dark, despite years of work.

"Astronomers are still debating the physical processes that can generate these big stars," Dr Barnes says.

"Massive stars are rare, making up only a few per cent of all stars, and they will only form in significant numbers when really massive clouds of gas collapse, creating hundreds of stars of different masses. Smaller gas clouds are not likely to make big stars."

Accordingly, regions in space where massive stars seem to be forming are also rare. Most are well over 1000 light-years away, making them hard to observe.

Using CSIRO's 'Mopra' radio telescope - a 22m dish near Coonabarabran, NSW - the research team discovered a massive cloud of mostly hydrogen gas and dust, three or more light-years across, that is collapsing in on itself and will probably form a huge cluster of stars.

Dr Stuart Ryder of the Anglo-Australian Observatory said the discovery was made during a survey of more than 200 gas clouds.

"With clouds like this we can test theories of massive star cluster formation in great detail."

The gas cloud, called BYF73, is about 8,000 light years away, in the constellation of Carina ("the keel") in the Southern sky.

Evidence for 'infalling' gas came from the radio telescope's detection of two kinds of molecules in the cloud - HCO+ and H13CO+. The spectral lines from the HCO+ molecules in particular showed the gas had a velocity and temperature pattern that indicated collapse.

Mopra Research Scientist at CSIRO Astronomy and Space Science, Dr Kate Brooks, said the Mopra telescope excels at giving a picture of the complex chemistry of cosmic gas clouds.

"Much of its time is used for large projects like this, and almost all Mopra projects are international collaborations."

The CSIRO telescope observations were confirmed by observations with the Atacama Submillimeter Telescope Experiment (ATSE) telescope in Chile.

The research team calculates that the gas is falling in at the rate of about three per cent of the Sun's mass every year - one of the highest rates known.

Follow-up infrared observations made with the 3.9-m Anglo-Australian Telescope (also near Coonabarabran, NSW) showed signs of massive young stars that have already formed right at the centre of the gas clump, and new stars forming.

Star-formation in the cloud was also evident in archival data from the Spitzer and MSX spacecraft, which observe in the mid-infrared.

Gas cloud BYF73 was found during a large-scale search for massive star-forming regions - the Census of High- and Medium-mass Protostars, or CHaMP. This is one of the largest, most uniform and least biased surveys to date of massive star-forming regions in our Galaxy.

NASA To Probe First Moments Of The Universe

This graphic shows the universe as it evolved from the big bang to now. Goddard scientists believe that the universe expanded from subatomic scales to the astronomical in a fraction of a second after its birth. They now building, along with their university partner, an instrument that searches for clues that the inflation did, in fact, occur. Credit: NASA/WMAP Science Team

Sophisticated new technologies created by NASA and university scientists are enabling them to build an instrument designed to probe the first moments of the universe's existence.

Former NASA scientist Chuck Bennett, now an astrophysicist at Johns Hopkins University (JHU) in Baltimore, Md., won a $5-million National Science Foundation grant to build a new ground-based instrument, the Cosmology Large Angular Scale Surveyor (CLASS). Bennett is building CLASS with his collaborators at the NASA Goddard Space Flight Center in Greenbelt, Md.

Goddard will provide most of the instrument's sophisticated detectors and other state-of-the-art technologies that will allow the scientists to test the "inflation theory" of the universe's origin.

Staggering Idea
Considered a staggering idea just 30 years ago, the inflation theory postulates that the universe expanded far faster than the speed of light and grew exponentially almost instantaneously after the big bang, the moment the universe sprang into existence 13.7 billion years ago.

In particular, the telescope will search for a unique polarization pattern in the cosmic background radiation - the remnant light from the first moment of the universe's creation that bathes the sky in all directions. Because of the size and expansion of the universe, scientists can study this ancient light only if their instruments are tuned to microwave frequencies.

If the cosmic growth spurt from inflation really happened, scientists say the event could have created gravitational waves, which are ripples in the fabric of space. The theory also predicts that these gravitational waves would have caused the background light to be polarized in a particular pattern. The telescope, therefore, will look for this signature pattern.

"Miraculously enough, it is within our ability to probe back into the first moments of the universe and learn what happened then," Bennett said.

The CLASS team, which also includes other partner institutions, will complete the instrument in 2014, equipping it with detectors sensitive to microwave light. The team then will ship the instrument to the Atacama Desert in northern Chile where it will observe large swaths of the microwave sky in search of the polarized signature.

Tantalizing Clues
Although scientists have yet to find the polarization pattern, they have uncovered tantalizing clues that inflation did, in fact, happen. Scientific results from the Goddard-developed Cosmic Background Explorer (COBE) found tiny temperature differences in the cosmic background radiation. These differences varied by only a few millionths of a degree and pointed to density differences that eventually gave rise to the stars and galaxies seen today.

COBE's successor, the Goddard-led Wilkinson Microwave Anisotropy Probe (WMAP), examined the tiny temperature differences in more detail and discovered new evidence for inflation. Among other things, WMAP showed that the geometry of the universe is close to flat - a physical dimension attributable to inflation. However, other theories explain these dynamics. What the scientific community needs is definitive proof of the primordial gravity waves - phenomena that could have been produced only by inflation.

Another Goddard Mission Complements CLASS
CLASS is not the only effort aimed at finding the same telltale evidence. Another Goddard team is now building a balloon-based instrument, the Primordial Inflation Polarization Exploration (PIPER) that Principal Investigator Al Kogut hopes to launch in 2012. "CLASS and PIPER are perfect partners," said Goddard scientist Ed Wollack, who is involved in the CLASS project. "They share many technologies while spanning a wide frequency range. They will do great science while demonstrating the technologies for a space mission."

Although both CLASS and PIPER are looking for the same polarization signature, they will approach the challenge using different detector technologies to study different microwave frequencies. Both detector technologies were developed at Goddard.

"The more frequencies you study, the better your chance of detecting the pattern of inflation," said David Chuss, a Goddard scientist working on CLASS.

The ultimate goal for the Goddard-JHU team is leveraging its expertise with CLASS and PIPER and winning a possible follow-on space observatory that would examine the primordial background light with even greater precision. "What we're doing is very much what we need to do to be competitive for an observatory if NASA decides to launch one," Chuss said.

Galaxy Clusters Enveloped by Cigar-Shaped Dark Matter Halos

Image comment: A photo of the Bullet Cluster, one of the 20 such structures that was analyzed for the new investigation
Image credits: NASA / STScI / Magellan / U.Arizona / D.Clowe et al

A series of recent experiments has revealed that, more often than not, the halos of dark matter surrounding massive galaxy clusters are flattened and shaped like a cigar. Until now, astrophysicists believed that the mysterious stuff, which is believed to be five times more abundant than regular matter around the Universe, would clump up in rounded spheres. However, observations appear to paint a different picture, and experts are currently working on models that would help explain that. The discovery could finally lead to studies that would result in the direct detection of the peculiar type of matter, whose existence can only be inferred from the gravitational pull it exerts on normal matter around it. “There are clear theoretical predictions that we expect dark mater halos to be flattened like this. It's a very beautiful, very clean and direct measurement of that,” explains expert Graham P. Smith, who is based at the University of Birmingham, in the United Kingdom. He is also a coauthor of the new study, which will appear in an upcoming issue of the esteemed scientific publication Monthly Notices of the Royal Astronomical Society. In the new studies, the investigators looked at about 20 galaxy clusters, which are massive collections of galaxies, held together by strong gravitational interactions. In order to see the effect dark matter has on the largest organized structures in the Universe, the researchers used gravitational lensing. This observations technique analyzes how much light is bent when mass wraps time-space in order to determine the mass of celestial objects beyond. The Mauna Kea, Hawaii-based Subaru Telescope was used for the study, and the team took advantage of the Prime Focus Camera above all other instruments. “What we're probing with these gravitational lensing observations is the dark matter distribution, because the dark matter dominates the mass on these large scales,” Smith says. The research team in charge of the study was led by National Astronomical Observatory of Japan expert Masamune Oguri and University of Tokyo scientist Masahiro Takada. The cigar-like shapes of these dark matter halos have been predicted in computer models of the cold dark matter theory, but thus far they have not been evidenced in practice in such a large number of galaxy clusters, Space reports.

NRL Researchers Study Galaxy Mergers

The University of Hawaii 2.2-meter telescope.

Scientists at the Naval Research Laboratory have solved a long-standing dilemma about the mass of infrared bright merging galaxies. Because galaxies are the largest directly observable objects in the universe, learning more about their formation is key to understanding how the universe works.

Dr. Barry Rothberg and Dr. Jacqueline Fischer, both of the Infrared-Submillimeter Astrophysics & Techniques Section in the Remote Sensing Division, used new data from the 8-meter Gemini-South telescope in Chile along with earlier results from the W. M. Keck-2 10-meter and University of Hawaii 2.2-meter telescopes in Hawaii and archival data from the Hubble Space Telescope, to solve the problem. They have published a paper on their research findings on galaxy evolution in the Astrophysical Journal (March 20, 2010 Volume 712).

Galaxies in the Universe generally come in two shapes, spiral, like our own Milky Way, and elliptical, in which the stars move in random orbits, Rothberg explains. The largest galaxies in the Universe are elliptical in shape and how they formed is central to our understanding how the Universe has evolved over the last 15 billion years. The long-standing theory has been that spiral galaxies merge with each other forming most of the elliptical galaxies in the Universe. Spiral galaxies contain significant amounts of cold hydrogen gas. When they merge, the beautiful spiral patterns are destroyed and the gas is converted into new stars. The more gas present in the spiral galaxies, the more stars are formed and with it, large amounts of dust. The dust is heated by the young stars and radiates energy at infrared wavelengths.

Until recently scientists thought that these infrared bright merging galaxies were not massive enough to be the precursors of most elliptical galaxies in the Universe. The problem lay in the method of measuring their mass. The conventional method of measuring mass in dusty IR-bright galaxies uses near-infrared light to measure the random motions of old-stars. The larger the random motions, the more mass is present. Using near-infrared light makes it possible to penetrate the dust and see as many of the old stars as possible. However, a complication occurs when spiral galaxies merge, because most of their gas is funneled to the gravitational center of the system and forms a rotating disk. This rotating disk of gas is transformed into a rotating disk of young stars that is also very bright at near-infrared wavelengths. The rotating disk of young stars both outshines the old stars and makes it appear as if the old stars have significantly less random motion. In contrast to this conventional method, Rothberg and Fischer instead observed the random motions of old stars at shorter wavelengths effectively using the dust to their advantage to block the light from the young stars. Their new results showed that the old stars in merging galaxies have large random motions, which means they will eventually become very massive elliptical galaxies.

The next step for NRL researches is to directly observe the stellar disks in IR luminous mergers using three-dimensional spectroscopy. Each pixel is a spectrum, and from this the researchers can make two-dimensional maps of stellar motion and stellar age. This will allow them to measure the size, rotation, luminosity, mass and age of the central disk.

Source:- NRL

M81's 'Halo' Sheds Light on Galaxy Formation

Visible light image of spiral galaxy M81 taken by Suprime-Cam.

Observations with Subaru Telescope's Prime Focus Camera (Suprime-Cam) have revealed an extended structure of the spiral galaxy Messier 81 (M81) that may hold a key to understanding the formation of galaxies. This structure could be M81's halo. Until now, ground-based telescopes have only observed individual stars in the haloes around the Milky Way and Andromeda Galaxies. Differences in M81's extended structure from the Milky Way's halo may point to variations in the formation histories of spiral galaxies.

M81 is one of the largest galaxies in the M81 Group, a group of 34 galaxies located toward the constellation Ursa Major. At 11.7 million light years from Earth, it is one of the closest groups to the Local group, the group of galaxies that includes our own Milky Way. Thanks to its proximity and similarity to the Milky Way, M81 provides an excellent laboratory for testing galaxy formation models.

The most prominent of these models predicts that galaxies are built up from the merging and accretion of many smaller galaxies that orbit within their gravitational sphere of influence. This chaotic, bottom-up growth leaves behind a halo of stars around massive spirals like the Milky Way. Do the findings about M81's extended structure, possibly its halo, support this view?

True to its promise as an effective tool for the study of galaxy evolution, Subaru's telescope has provided data to address this question. The enormous light-gathering power of Subaru Telescopes's 8.2 meter primary mirror and the wide field-of-view of its Suprime-Cam enabled the telescope to provide evidence for a faint, extended structural component beyond M81's bright optical disk. It probed into space over one-hundred times darker than the night sky and imperceptible to the naked eye. The telescope spotted individual stars and gathered enough of them to identify M81's extended component and analyze its physical properties.

The results defy exact classification of the extended structure as a halo. Although the spatial distribution of its stars resembles the Milky Way's halo, M81's "halo" differs from the Milky Way's in other respects. Measurements of the total light from all of its stars and analysis of their colors point to estimates that M81's "halo" could be several times brighter and contain more processed materials, nearly twice as much mass in the form of metals (all elements heavier than helium), than the Milky Way's halo.

These differences prompt some fascinating questions. Do we need to expand our definition of a halo? Does this structure have a very different formation history than the Milky Way's halo? Did these differences arise because M81 cannibalized more or different kinds of small galaxies in the past than the Milky Way did? Regardless of the answers to these queries, the results of this research contribute to the growing body of evidence that the outer structures of apparently similar galaxies are much more important and complex than astronomers have previously thought.

Provided by Subaru Telescope

Hubble snaps heavyweight of the Leo Triplet

Hubble has snapped a spectacular view of M 66, the largest "player" of the Leo Triplet, and a galaxy with an unusual anatomy: it displays asymmetric spiral arms and an apparently displaced core. The peculiar anatomy is most likely caused by the gravitational pull of the other two members of the trio.

The unusual spiral galaxy, Messier 66, is located at a distance of about 35 million light-years in the constellation of Leo. Together with Messier 65 and NGC 3628, Messier 66 is the member of the Leo Triplet, a trio of interacting spiral galaxies, part of the larger Messier 66 group. Messier 66 wins in size over its fellow triplets — it is about 100 000 light-years across.

This is a composite of images obtained through the following filters: 814W (near infrared), 555W (green) and H-alpha (showing the glowing of the hydrogen gas). They have been combined so to represent the real colours of the galaxy.

Source:- http://www.spacetelescope.org/images/html/heic1006a.html

WISE Snaps Image of 'Leggy' Galactic Creature

Image comment: The new WISE image of the hidden galaxy IC 342
Image credits: NASA / JPL-Caltech / UCLA

The Milky Way is only one structure in a sea of galaxies permeating the Universe. Astronomers can peer through it at various wavelengths in order to look deep in the Cosmos, back to the time when it was only a few millions of years old. However, there are structures in our vicinity that cannot be observed in certain wavelengths, given that they are obscured by the dust and gas inside our own galaxy, or by the brightness of the stars in our galactic core. But some types of light can go through this “shield” and look immediately beyond our galaxy.

This is precisely what NASA's newly-launched Wide-field Infrared Survey Explorer (WISE) telescope did, when it used its infrared detectors to peer through the Milky Way's central regions. Its target is a spiral galaxy called IC 342, which astronomers know about, but that cannot be observed in visible light wavelengths. The structure is in fact oftentimes referred to by experts as the “hidden galaxy.” It is obscured by the thick clouds of dust in our galaxy's central regions, but this veil can easily be pierced by sensitive infrared telescopes such as WISE and Spitzer.

“This galaxy has been of great interest to astronomers because it is relatively close. However, determining its distance from Earth has proven difficult due to the intervening Milky Way. This image was made from observations by all four infrared detectors aboard WISE. Blue and cyan represent infrared light at wavelengths of 3.4 and 4.6 microns, which is primarily light from stars. Green and red represent light at 12 and 22 microns, which is primarily emission from warm dust,” experts at the NASA Jet Propulsion Laboratory (JPL) in Pasadena, California write of the new images on their official website.

Edwin Hubble, the world-famous astronomer after whom the orbital telescope is named, first proposed some time ago that the hidden galaxy was a part of our Local Group of galaxies. However, more recent observations, using advanced telescopes, determined that IC 342 is most likely located much farther away than Hubble calculated. New estimates place it a distance of between 6.6 and 11 million light-years away from the Milky Way. For comparison, our closest neighbor, the Andromeda galaxy, is some 2.5 million light-years away.

Experts Find What Influences the Growth of Galaxy Clusters

Image comment: Illustration showing the ICM region of Abell 1689, which is heated at around 60 million degrees
Image credits: RIKEN Advanced Science Institute

Without a doubt, galaxy clusters are the largest coherent structures in the known Universe. They are made up of hundreds of thousands of galaxies, all held together through the force of gravity. While it may be difficult to observe clusters at first, careful analysis of how seemingly-unrelated galaxies move soon hints at their presence. For many years, astronomers and astrophysicists have been wondering how is it that these giant structures are held together, and also what factors govern their growth. Now, for the first time, an international collaboration of scientists proposes an answer to this mystery.

Scientists from the Japan-based RIKEN institution, working together with colleagues from the Academia Sinica Institute of Astronomy and Astrophysics, managed to identify details pertaining to cluster growth and development. While doing so, they may have also gained new insight into how our Universe developed a short time after the Big Bang exploded everything into being. Their work was prompted by the fact that the actual mass of galaxies in a cluster only accounts for a fraction of the gravitational pull that exists in these regions.

There are only two other possible sources for this force, physicists hypothesize. One is the elusive dark matter, which, for now, remains invisible to detectors, but which is believed to interact with normal matter only through gravity. The other one is the intracluster medium (ICM), the stuff that resides within the cluster itself. Using telescopes capable of measuring the Universe in X-ray wavelengths, researchers found in previous studies that the ICM is made up of superheated plasma, which exits at temperatures of millions of degrees.

Using Japan's sensitive Suzaku X-ray satellite, the group looked at the ICM in the galaxy cluster Abell 1689, in order to understand its influence better. It was discovered that the medium there has a temperature of no less than 23 million degrees, on average. However, areas that are heated beyond this value exist. The warmest spot, the team reports, was found to be heated at about 60 million degrees. This hot region had a weird filamentary structures protruding from it, which researchers determined was made up of many galaxies.

The group writes in the April 9 issue of The Astrophysical Journal that this structure is most likely nothing more than a shock wave. They hypothesize that it was produced after the galaxy cluster that provides the heat for the ICM collided with the cold gas clouds the filament contains. Hence, the science team was able to determine that the large-scale structure of the surrounding Universe influenced the growth of the cluster itself. Gravitational lensing data supplied by the Japanese Subaru observatory, and the Hubble Space Telescope, confirmed the initial readings Suzaku gathered.

Fermi Maps An Active Galactic Smokestack Plumes

The gamma-ray output from Cen A's lobes exceeds their radio output by more than ten times. High-energy gamma rays detected by Fermi's Large Area Telescope are depicted as purple in this gamma ray/optical composite of the galaxy. Credit: NASA/DOE/Fermi LAT Collaboration, Capella Observatory

If our eyes could see radio waves, the nearby galaxy Centaurus A (Cen A) would be one of the biggest and brightest objects in the sky, nearly 20 times the apparent size of a full moon. What we can't see when looking at the galaxy in visible light is that it lies nestled between a pair of giant radio-emitting gas plumes ejected by its supersized black hole. Each plume is nearly a million light-years long.

NASA's Fermi Gamma-Ray Space Telescope maps gamma rays, radiation that typically packs 100 billion times the energy of radio waves. Nevertheless, and to the surprise of many astrophysicists, Cen A's plumes show up clearly in the satellite's first 10 months of data. The study appears in Thursday's edition of Science Express.

"This is something we've never seen before in gamma rays," said Teddy Cheung, a Fermi team member at the Naval Research Laboratory in Washington. "Not only do we see the extended radio lobes, but their gamma-ray output is more than ten times greater than their radio output." If gamma-ray telescopes had matured before their radio counterparts, astronomers would have instead classified Cen A as a "gamma-ray galaxy."

Also known as NGC 5128, Cen A is located about 12 million light-years away in the constellation Centaurus and is one of the first celestial radio sources identified with a galaxy.

"A hallmark of radio galaxies is the presence of huge, double-lobed radio-emitting structures around otherwise normal-looking elliptical galaxies," said Jurgen Knodlseder, a Fermi collaborator at the Center for the Study of Space Radiation in Toulouse, France. "Cen A is a textbook example."

Astronomers classify Cen A as an "active galaxy," a term applied to any galaxy whose central region exhibits strong emissions at many different wavelengths. "What powers these emissions is a well-fed black hole millions of times more massive than our sun," said Yasushi Fukazawa, a co-author of the study at Hiroshima University in Japan. "The black hole somehow diverts some of the matter falling toward it into two oppositely directed jets that stream away from the center."

Fueled by a black hole estimated at hundreds of millions of times the sun's mass, Cen A ejects magnetized particle jets moving near the speed of light. Over the course of tens of millions of years, these jets puffed out two giant bubbles filled with magnetic fields and energetic particles - the radio lobes we now see. The radio waves arise as high-speed electrons spiral through the lobes' tangled magnetic fields.

But where do gamma rays - the highest-energy form of light - come from?

The entire universe is filled with low-energy radiation - radio photons from the all-pervasive cosmic microwave background, as well as infrared and visible light from stars and galaxies. The presence of this radiation is the key to understanding Cen A's gamma rays.

"When one of these photons collides with a super-fast particle in the radio lobes, the photon receives such an energy boost, it becomes a gamma ray," explained co-author Lukasz Stawarz at the Japan Aerospace Exploration Agency in Sagamihara, Japan.

Although it sounds more like billiards than astrophysics, this process, called inverse Compton scattering, is a common way of making cosmic gamma rays. For Cen A, an especially important aspect is the case where photons from the cosmic microwave background ricochet off of the highest-energy particles in the radio lobes.

In dozens of active galaxies, this process has been shown to produce X-rays. But the Cen A study marks the first case where astronomers have solid evidence that microwave photons can be kicked up to gamma-ray energies.

Fermi cataloged hundreds of blazars and other types of active galaxies in its first year. Before its mission ends, that number may reach several thousand. But because Cen A is so close, so large and so vigorous, it may be the only active galaxy Fermi will view this way.

With Centaurus A, Fermi hit the jackpot.

Centaurus A Emits in Both Radio and Gamma-ray Wavelengths

In orbit only since June 2008, the Fermi Gamma-ray Space Telescope has already produced some remarkable science. One of the most remarkable findings it made so far was the fact that the closest active galaxy to the Milky Way, called Centaurus A, is capable of emitting both gamma-rays and radio radiation. In previous studies, it was proposed that a galaxy could either emit one or the other, but the new data seems to indicate that both types of emissions are possible at the same time.

An active galaxy is a space structure whose central region emits radiation across a very wide portion of the electromagnetic spectrum. Generally, the core is occupied by a supermassive black hole, which gobbles up matter, and then releases vast amounts of radiation in exchange. In the case of Centaurus A, which has for a long time been determined to be one of the most potent and bright sources of radio wavelengths in the sky, the core produced vast amounts of extremely high-energy gamma-rays as well, Space reports.

“This is something we've never seen before in gamma-rays,” explains of the new Fermi findings expert Teddy Cheung. He is a member of the team managing the observatory, and is based in Washington DC, at the Naval Research Laboratory (NRL). As far as physicists go, gamma-rays represent the most energetic form of light possible in the Universe. But, inside Centaurus A, these photons are ramped up to even higher energies than usual. The huge lobes of the active galaxy contain super-strong magnetic fields, in which a wide variety of particles get accelerated. The gamma-rays entering these highly-active regions also get a massive energy boost.

This results in what can perhaps be best described as the most energetic photons in the known Universe. Astrophysicists suspect that the situation is not unique and say that many of the active, massive galaxies out there may be producing the same amplification effect on their own gamma-ray sources. “Not only do we see the extended radio lobes, but their gamma-ray output is more than 10 times greater than their radio output,” Cheung adds. More details of the study appear in the April 2 issue of the esteemed publication Science.

The Origins of Galactic Magnetic Fields Identified

For a long time, astronomers have wondered how is it that galaxies get to be so heavily magnetized. These space structures feature strong magnetic fields that play a huge role in the way they are set up, organized, and so on. Following a new series of investigations, experts now believe they may have finally found out where these fields originate from. While looking deep into space, they noticed very strange magnetic fields simply floating about. Now, they propose that these phenomena are responsible for creating the magnetism average galaxies exhibit at this point, Space reports.

“Basically we have found some magnetic fields which are in the middle of nowhere, outside galaxies and galaxy clusters and all other known structures. People have suggested that such fields should exist on theoretical grounds, but they have never been detected before,” says Geneva Observatory in Switzerland astronomer and researcher Andrii Neronov. But the experts may have just traded one mystery for another. The origins of these precursor magnetic fields is also unknown, although their role in promoting galactic magnetism appears to have been confirmed.

According to one of two widely circulated theories on their origins, these magnetic fields may have been formed a very short period of time after the Big Bang exploded the Universe into being. Granted, when they first appeared, they were very small and weak, but over time they grew to the intensity that is currently visible to observers. The other theory states that these fields were produced by the earliest forms of galaxies, structures known as protogalaxies. Inside them, matter collided randomly, on its way to organizing itself into the shape we now usually attribute to galaxies.

According to Neronov, the second idea may actually have more merit, based on the observations he and his group conducted. The expert reveals that the magnetic fields were not observed directly. Rather, their existence was inferred from the absence of certain wavelengths of light in the areas of the sky that the group investigated. They analyzed the intergalactic medium, using the NASA Fermi Gamma-Ray Space Telescope. In some areas of the sky, much less radiation than anticipated actually exists.

It could be that the hypothesized magnetic fields are the factors deterring these particular wavelengths from being noticed from our vantage point. “At the moment we have seen some negative effects. We have seen some features which are due to the absorption of gamma-rays from distant sources,” the expert concludes. Details of the investigation are published in the April 2 issue of the esteemed publication Science.

Quasars Form When Galaxies Collide

Image comment: According to a new study, quasars can form when two galaxies collide

Image credits: NASA / ESA / Hubble Heritage (STScI/AURA) / Hubble Collaboration / A. Evans (University of Virginia / NRAO / Stony Brook University) / E. Treister and K. Teramura (IfA / University of Hawaii)

There are many peculiar types of objects in the Universe, but a quasar tends to overcome most of them in terms of weirdness. Scientists describe it as the highly-active area around a supermassive black hole that is capable of gobbling up matter from its surroundings at a frantic rate, while at the same time emitting large amounts of light. This is all well and good, but for many years researchers had no idea as to how these impressive structures formed. Now, new studies appear to suggest that they are the direct result of galactic mergers, when two galaxies “cannibalize” each other, Space reports.

Naturally, there is no way of knowing this for sure, given the fact that we could never observe a galactic collision from start to finish. These processes take millions of years to happen, and observing them is impractical. But we do have supercomputers, capable of simulating the past and the future of a system in which two galaxies are colliding based only on minimal amounts of data. It's through this type of methods that astronomers were finally able to hypothesize that mergers may be directly responsible for the formation of quasars – some of the brightest structures in the Cosmos.

Small- and average-sized black holes never become quasars. Only the largest of the behemoths develop the impressive disk of matter around them, allowing them to grow very fast, while releasing vast amounts of radiation in nearly all wavelength ranges of the electromagnetic spectrum. These emissions are caused by the large amount of heat that is caused by the friction of matter before it falls through the event horizon. Because they are always “hungry,” quasars only develop within galaxies that have a sufficiently-bulky core to allow for the structure to feed for a long time.

A new study proposes that the quasars may have found a way around this limitation, by developing at the core of a galactic merger, between two gas-rich galaxies. This idea was first proposed in 1988, by astronomer David Sanders, from the University of Hawaii. It was only now that, together with UH colleagues led by expert Ezequiel Treister, he had a chance to test the idea. Data from the Chandra, Spitzer and Hubble space telescopes were used to look at various quasars in several wavelength ranges, including optical light, X-ray and infrared.

“We made a simple model in which every galaxy merger generates a quasar that is first obscured and then un-obscured. The agreement is just remarkable. That does indicate that pretty much every galaxy merger generates a quasar. When the Milky Way collides with Andromeda, if at that time there's enough gas available, that gas will probably end up in the center around the black hole, making a quasar,” says Treister.

How Dark Matter Behaves Around Black Holes

The standard explanation of how our Universe is set up states that roughly one quarter (23 percent) of everything is made out of dark matter, a form of matter that cannot be readily observed through conventional means. In fact, it has never been observed at all, although scientists tried out a wide variety of methods for detecting it. But now, two experts advance a new role for dark matter that proposes the stuff altered the amounts of galaxies in the Universe, and that it did so to a significant margin, AlphaGalileo reports.

Astronomers Dr Xavier Hernandez and Dr William Lee, both of whom are based at the National Autonomous University of Mexico (UNAM), say that their study was prompted by their curiosity in learning how dark matter would interact with the supermassive black holes that form at the cores of impressively-large galaxies. The team says that its models provided them with a new basis for calculating both these interactions and the rate at which dark matter would get sucked in through the event horizon.

The group determined the existence of a threshold in these rates. If the immediate surroundings of the black hole are laden with dark matter in amounts higher than 7 Sun masses per cubic light-year, then the initial black hole was found to be capable of growing at extremely fast rates. Their investigation also revealed that, if such a growth spur was activated, then the black hole would be fueled even further by dark matter, eventually consuming the galaxy around it. If the galaxy would survive this ordeal, the group says, then it would be altered beyond any possible recognition when compared to its original shape.

“Over the billions of years since galaxies formed, such runaway absorption of dark matter in black holes would have altered the population of galaxies away from what we actually observe,” Hernandez says. The greatest implication of their analysis is the fact that the amounts of dark matter present at the cores of galaxies needs must tend for a constant value, if the entire structure is to remain stable. An additional implication is that dark matter may be behaving in ways previously not thought-of. This means that current models aimed at explaining its behavior – and which therefore underline efforts to find the stuff – may have to be thought over.

Astronomers Get Sharpest View Ever of Star Factories in Distant Universe

Arp 220 is a nearby example of a merged starburst galaxy similar to SMM J2135-0102. Located 250 million light-years from Earth, Arp 220 is the aftermath of a collision between two spiral galaxies. The collision, which began about 700 million years ago, has sparked a crackling burst of star formation, resulting in about 200 huge star clusters in a packed, dusty region about 5,000 light-years across (about 5 percent of the Milky Way's diameter). The star clusters are the bluish-white bright knots visible in the Hubble image.

Credit: NASA, ESA, the Hubble Heritage-ESA/Hubble Collaboration, and A. Evans (UVa/NRAO/Stony Brook)

The distant galaxy SMM J2135-0102, shown here in 870-micron observations by the Submillimeter Array, has been gravitationally lensed by a foreground galaxy cluster. The galaxy's light is magnified and bent by gravity to produce mirror images of each of four star-forming regions (labeled A through D). If the galaxy were seen undistorted, it would appear like the inset at upper left. Regions A and D are separated by less than 6,000 light-years. The inset at lower right shows the resolution of the SMA image.

Credit: Mark Swinbank (Durham) and Steve Longmore (SAO)

Astronomers have combined a natural gravitational lens and a sophisticated telescope array to get the sharpest view ever of "star factories" in a galaxy over 10 billion light-years from Earth. They found that the distant galaxy, known as SMM J2135-0102, is making new stars 250 times faster than our Galaxy, the Milky Way. They also pinpointed four discrete star-forming regions within the galaxy, each over 100 times brighter than locations (like the Orion Nebula) where stars form in our Galaxy. This is the first time that astronomers have been able to study properties of individual star-forming regions within a galaxy so far from Earth.

"To a layperson, our images appear fuzzy, but to us, they show the exquisite detail of a Faberge egg," said Steven Longmore of the Harvard-Smithsonian Center for Astrophysics (CfA). Longmore is an author of the paper describing these findings, which was published in the March 21st Nature online.

Due to the time it takes light to travel to us, we see the galaxy as it existed just 3 billion years after the Big Bang. It was Milky Way-sized at the time. If we could see it today, 10 billion years later, it would have grown into a giant elliptical galaxy much more massive than our own.

"This galaxy is like a teenager going through a growth spurt," said Mark Swinbank of Durham University, lead author on the paper. "If you could see it today as an 'adult,' you'd find the galactic equivalent of Yao Ming the basketball player."

Sharpest View

From our point of view, SMM J2135-0102 is located behind a massive cluster of nearby galaxies. The cluster's gravity acts as a lens to magnify the more distant galaxy by a factor of 16 in both apparent size and brightness, bringing otherwise imperceptible details to light.

The galaxy, while heavily obscured by dust at visible wavelengths, emits prodigious amounts of light at submillimeter wavelengths (close to the radio region of the spectrum). Indeed, it is the brightest known submillimeter galaxy, making it a natural target for the Submillimeter Array (SMA).

The SMA is an 8-element interferometer operating in the wavelength range of 0.3 to 2 millimeters, located atop Mauna Kea in Hawaii. Combined with the natural magnification of the gravitational lens, the array provided extremely high resolution observations - equivalent to using a telescope in Boston to spot a dime in Washington DC. This yielded a level of detail for a galaxy 10 billion light-years away comparable to the best observations of nearby starburst galaxies (which also show high rates of star formation).

Because of the obscuring dust, the galaxy's distance could not be determined by observations of visible light. For that task, the astronomers turned to a unique instrument, called the "Zpectrometer," on the National Science Foundation's Robert C. Byrd Green Bank Telescope. This instrument was able to determine the galaxy's distance by measuring radio emission from carbon monoxide molecules. The precise distance measurement allowed the scientists to determine "the exact effect that gravitational lensing would have on the galaxy, and therefore exactly how the galaxy would look in the absence of lensing," according to Andrew Baker, of Rutgers University.

Star Factories

The SMA data revealed four extremely bright star-forming regions. The large luminosities, 100 times greater than typical for nearby galaxies, imply a very high rate of star formation.

"We don't fully understand why the stars are forming so rapidly, but our result suggests that stars formed much more efficiently in the early universe than they do today," said Swinbank.

Their results provide new insight into a critical time during the Universe's history. SMM J2135-0102 is seen at the epoch when the majority of all stars were born, and therefore when many of the properties of nearby galaxies were defined. By studying it and other distant galaxies in the young Universe, astronomers hope to learn about the history of the Milky Way and other nearby galaxies.

Future surveys should identify more targets for study by the SMA and next-generation telescopes such as the Atacama Large Millimeter Array.

"That will allow us to test exactly how generic our results are: Is the star formation occurring within galaxies in the early Universe always so vigorous? Or are we catching this particular galaxy at a very special time?" said Longmore.

Source: Harvard-Smithsonian Center for Astrophysics