Posted on by Jon Voisey

Globular Clusters on a Plane

Smaller satellite galaxies caught by a spiral galaxy are distorted into elongated structures consisting of stars, which are known as tidal streams, as shown in this artist's impression. Credit: Jon Lomberg

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Globular clusters are generally some of the oldest structures in our galaxy. Many of the most famous ones formed around the same time as our galaxy, some 13 billion years ago. However, some are distinctly younger. While many classification schemes are used, one breaks globular clusters into three groups: an old halo group which includes the oldest of the clusters, those in the disk and bulge of the galaxy which tend to have higher metallicity, and a younger population of halo clusters. The latter of these provides a bit of a problem since the galaxy should have settled into a disk by the time they formed, depriving them of the necessary materials to form in the first place. But a new study suggests a solution that’s not of this galaxy.

The new study looked at the distribution of these younger clusters around our Milky Way. Of the three classifications for globular clusters discussed, the young halo clusters are scattered well beyond the range of the other populations. The young halo extends to as much as 120 kiloparsecs (400 thousand light years) while the old halo clusters tend to lie within 30 kiloparsecs (100 thousand light years). Additionally, the young clusters don’t appear to be rotating with the disk of the galaxy whereas the old halo slowly orbits in the same direction as the disk.

In looking more carefully at the positions of these satellites, the team, led by Stefan Keller at the Australian National University, found that the younger population tends to lie in a wide plane that is tilted from the rotational axis of our galaxy by a mere 8°.

This plane is strikingly similar to another recognized grouping of objects: Many of the known dwarf galaxies lie in a nearly identical plane, known as the Plane of Satellites (PoS). This finding suggests that this population of globular clusters is a relic of cannibalized galaxies. Even more interesting is that, while these objects are younger than the distinctly “old” population, there is still a large variation in their ages. This implies that this plane wasn’t created by the accretion of one, or even a few minor galaxies, but a consistent feeding of small galaxies onto the Milky Way for much of the history of the universe, and all from the same direction. Studies of the distribution of satellites around our nearest major neighbor, M31, the Andromeda galaxy, has turned up a similar preferred plane, tilted some 59° from its disk.

One explanation for this is that this is a preferred direction that traces invisible filaments of dark matter. While dark matter distributions are difficult to predict, models haven’t accounted for such strong filamentary structure on such small scales. Rather, in the neighborhood of our galaxy, the overall distribution is described as an oblate spheroid. One of the reasons astronomers believe our own dark matter halo is so nicely shaped is the way it is affecting the Sagittarius dwarf galaxy which is slowly being accreted onto our own. If the dark matter were more wispy, it should be stretched out in different manners.

Another possibility the authors consider is that the objects were created in a preferred plane “from the break up of a large progenitor at early times”. In other words, the filament could be a fossil of larger structure before our galaxy formed along which these dwarf galaxies formed and from which these galaxies could have been slowly accreting over the history of the galaxy.

Posted on by Nancy Atkinson

Gas, Not Galaxy Collisions Responsible for Star Formation in Early Universe

Artist concept of how a galaxy might accrete mass from rapid, narrow streams of cold gas. These filaments provide the galaxy with continuous flows of raw material to feed its star-forming at a rather leisurely pace. Credit: ESA–AOES Medialab

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Was the universe a kinder, gentler place in the past that we have thought? The Herschel space observatory has looked back across time with its infrared eyes and has seen that galaxy collisions played only a minor role in triggering star births in the past, even though today the birth of stars always seem to be generated by galaxies crashing into each other. So what was the fuel for star formation in the past?

Simple. Gas.

The more gas a galaxy contained, the more stars were born.

Scientists say this finding overturns a long-held assumption and paints a nobler picture of how galaxies evolve.

Astronomers have known that the rate of star formation peaked in the early Universe, about 10 billion years ago. Back then, some galaxies were forming stars ten or even a hundred times more vigorously than is happening in our Galaxy today.

In the nearby, present-day Universe, such high birth rates are very rare and always seem to be triggered by galaxies colliding with each other. So, astronomers had assumed that this was true throughout history.

GOODS-North is a patch of sky in the northern hemisphere that covers an area of about a third the size of the Full Moon. Credit: ESA/GOODS-Herschel consortium/David Elbaz

But Herschel’s observations of two patches of sky show a different story.

Looking at these regions of the sky, each about a third of the size of the full Moon, Herschel has seen more than a thousand galaxies at a variety of distances from the Earth, spanning 80% of the age of the cosmos.

In analyzing the Herschel data, David Elbaz, from CEA Saclay in France, and his team found that even though some galaxies in the past were creating stars at incredible rates, galaxy collisions played only a minor role in triggering star births. The astronomers were able to compare the amount of infrared light released at different wavelengths by these galaxies, the team has shown that the star birth rate depends on the quantity of gas they contain, not whether they are colliding.

They say these observations are unique because Herschel can study a wide range of infrared light and reveal a more complete picture of star birth than ever seen before.

However, their work compliments other recent studies from data from the Spitzer Space Telescope and the Very Large Telescope which found ancient galaxies fed on gas,not collisions

“It’s only in those galaxies that do not already have a lot of gas that collisions are needed to provide the gas and trigger high rates of star formation,” said Elbaz.

Today’s galaxies have used up most of their gaseous raw material after forming stars for more than 10 billion years, so they do rely on collisions to jump-start star formation, but in the past galaxies grew slowly and gently from the gas that they attracted from their surroundings.

This study was part of the GOODS observations with Herschel, the Great Observatories Origins Deep Survey.

Read the team’s paper in Astronomy & Astrophysics: GOODS–Herschel: an infrared main sequence for star-forming galaxies’ by D. Elbaz et al.

Source: ESA

Posted on by Tammy Plotner

The Genesis of Galaxy Eris…

This image of the Eris simulation shows the stars in the galaxy as observers would see it. Blue colors are regions of recent star formation, while redder regions are associated with older stars. The spiral arms are typically star-forming, and the central bulge is basically "red and dead." Credit: J. Guedes and P. Madau.

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In as much time as it takes to give birth to human life, a supercomputer and a team of researchers at the University of California, Santa Cruz, and the Institute for Theoretical Physics in Zurich have given rise to the first simulation of the physics involved in galaxy formation that produced the Milky Way. They named their child Eris…

“Previous efforts to form a massive disk galaxy like the Milky Way had failed, because the simulated galaxies ended up with huge central bulges compared to the size of the disk,” said Javiera Guedes, who recently earned her Ph.D. in astronomy and astrophysics at UC Santa Cruz and is first author of a paper which has been accepted for publication in the Astrophysical Journal.

This comparison shows the Eris simulation (top) and the Milky Way (bottom). Credit: S. Callegari, J. Guedes, and the 2MASS collaboration.
Like the Milky Way, Eris is a lovely barred spiral galaxy – her figure and star content as identical as modeling can make it. By studying our own galaxy and others like it, this simulation fits the mold from every angle. “We dissected the galaxy in many different ways to confirm that it fits with observations,” Guedes said.

And “seven sisters” were involved in the project, too. NASA’s state-of-the-art Pleiades supercomputer took on the task of 1.4 million processor-hours. But the calculations didn’t stop there. Simulations on supercomputers at UCSC and the Swiss National Supercomputing Center were involved, too. “We took some risk spending a huge amount of supercomputer time to simulate a single galaxy with extra-high resolution,” Madau said.

For over two decades, attempts at creating the evolution of a Milky Way type galaxy have been just outside the grasp of researchers. They just weren’t able to produce the proper shape, size and population to fit known properties. Thanks to this new breakthrough, support for the “cold dark matter” theory has predominated and the Big Bang theory supported. What gave Eris the edge? Try our now better understanding star formation.

“Star formation in real galaxies occurs in a clustered fashion, and to reproduce that out of a cosmological simulation is hard,” Madau said. “This is the first simulation that is able to resolve the high-density clouds of gas where star formation occurs, and the result is a Milky Way type of galaxy with a small bulge and a big disk. It shows that the cold dark matter scenario, where dark matter provides the scaffolding for galaxy formation, is able to generate realistic disk-dominated galaxies.”

Giving birth to Eris wasn’t an easy task. Through low-resolution simulations, researchers began assembling clumps of dark matter – shaping them into galactic halos. From there they selected information on a halo with similar mass and merger history to our own and “rewound the tape” to its infancy. By focusing on a small area, they were able to add additional particle information and step up the resolution.

“The simulation follows the interactions of more than 60 million particles of dark matter and gas. A lot of physics goes into the code–gravity and hydrodynamics, star formation and supernova explosions–and this is the highest resolution cosmological simulation ever done this way,” said Guedes, who is currently a postdoctoral researcher at the Swiss Federal Institute of Technology in Zurich (ETH Zurich).

What sets Eris apart from its predecessors is the ability to “see” in high resolution / high density. This allows for a more pragmatic approach to star formation and placement. It’s an important consideration, because supernova occur in high density regions and high resolution allows them to be taken into account.

“Supernovae produce outflows of gas from the inner part of the galaxy where it would otherwise form more stars and make a large bulge,” Madau said. “Clustered star formation and energy injection from supernovae are making the difference in this simulation.”

Arise, Eris… Your time has come!

Original Story Source: University of Santa Cruz News. For Further Reading: Forming Realistic Late-Type Spirals in a LCDM Universe: The Eris Simulation.

Posted on by Tammy Plotner

Rare New Galaxy Reveals Black Hole Jet Secrets

Composite image of Speca: Optical SDSS image of the galaxies in yellow, low resolution radio image from NVSS in blue, high resolution radio image from GMRT in red. CREDIT: Hota et al., SDSS, NCRA-TIFR, NRAO/AUI/NSF.

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A newly discovered galaxy is aiding astronomers in the research into the early evolution of individual galaxies and galaxy clusters. Named Speca, this unique finding is only the second spiral galaxy known to produce “jets” – streams of subatomic particles emitted from the nucleus. What’s more, it’s also one of two which shows this activity happened in separate intervals.

As astronomers know, galaxy jets are formed at the heart of activity where a supermassive black hole is present. While both elliptical and spiral galaxies have known supermassive black holes, only one had been known to produce copious amounts of material from its poles – Messier 87. Now Speca is changing the way researchers look for recurring activity.

“This is probably the most exotic galaxy with a black hole ever seen. It has the potential to teach us new lessons about how galaxies and clusters of galaxies formed and developed into what we see today,” said Ananda Hota, of the Academia Sinica Institute of Astronomy and Astrophysics (ASIAA), in Taiwan.

Located in a galaxy cluster about 1.7 billion light-years, Speca (an acronym for Spiral-host Episodic radio galaxy tracing Cluster Accretion) made its presence known to Ananda’s researches via an image which joined data from the visible-light Sloan Digital Sky Survey and the FIRST survey done with the National Science Foundation’s Very Large Array (VLA) radio telescope. Subsequent observations with the Lulin optical telescope in Taiwan and ultraviolet data from NASA’s GALEX satellite verified the lobes of material were part of an active, star-forming galaxy. Ananda’s team further refined their studies with information from the NRAO VLA Sky Survey (NVSS), then made new observations with the Giant Meterwave Radio Telescope (GMRT) in India. Each telescope set provided more and more clues to solving the puzzle.

“By using these multiple sets of data, we found clear evidence for three distinct epochs of jet activity,” Ananda explained. But the real excitement began when the low-frequency nature of the oldest, outermost lobes was examined. It was an artifact which should have disappeared with time.

“We think these old, relic lobes have been ‘re-lighted’ by shock waves from rapidly moving material falling into the cluster of galaxies as the cluster continues to accrete matter,” said Ananda. “All these phenomena combined in one galaxy make Speca and its neighbors a valuable laboratory for studying how galaxies and clusters evolved billions of years ago.”

Sandeep K. Sirothia of India’s National Centre for Radio Astrophysics, Tata Institute of Fundamental Research (NCRA-TIFR) said, “The ongoing low-frequency TIFR GMRT Sky Survey will find many more relic radio lobes of past black hole activity and energetic phenomena in clusters of galaxies like those we found in Speca.” Also, Govind Swarup of NCRA-TIFR, who is not part of the team, described the finding as “an outstanding discovery that is very important for cluster formation models and highlights the importance of sensitive observations at meter wavelengths provided by the GMRT.”

Stay close to your radio, folks… Who knows what we’ll hear in the future!

Original Story Source: National Radio Astronomy Observatory News.

Posted on by Nancy Atkinson

Looking Into a Pair of Cosmic Eyes

A beautiful yet peculiar pair of galaxies, NGC 4438 and NGC 4435, nicknamed The Eyes. Credit: ESO/Gems project

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Have you ever looked through your telescope and felt like you were being watched? These two galaxies in the Virgo cluster form a pair of cosmic eyes that stare right back at you! These two oval-shaped galaxies, NGC 4438 (left) and NGC 4435, are nicknamed “The Eyes” since they resemble a pair of eyes glowing in the dark when seen in a moderate-sized telescope. This image was taken by the Very Large Telescope at Paranal in Chile, using the FORS2, a visual and near ultraviolet FOcal Reducer and low dispersion Spectrograph for the VLT.

These eyes have likely changed in shape over time, and astronomers can see evidence that the pair probably both were spiral galaxies in the past. The contents of NGC 4438 have been stripped out by a violent process: a collision with another galaxy. This clash has distorted the galaxy’s spiral shape, much as could happen to the Milky Way when it collides with its neighboring galaxy Andromeda in three or four billion years.

Although the two eyes look similar at their centers, their outskirts could not be more different. NGC 4435 is compact and seems to be almost devoid of gas and dust. In contrast, NGC 4438 has a lane of obscuring dust just below its nucleus, with young stars visible just left of its center, and gas extends at least up to the edges of the image.

ESO, the European Southern Observatory, is a collaboration between 15 countries: Austria, Belgium, Brazil, the Czech Republic, Denmark, France, Finland, Germany, Italy, the Netherlands, Portugal, Spain, Sweden, Switzerland and the United Kingdom. ESO carries out an ambitious program focused on the design, construction and operation of powerful ground-based observing facilities enabling astronomers to make important scientific discoveries. ESO also plays a leading role in promoting and organizing cooperation in astronomical research.

See more about this image at the ESO website.

Posted on by Tammy Plotner

The Lyman-Alpha Blob That Ate The Universe…

Observations from ESO’s Very Large Telescope have shed light on the power source of a rare vast cloud of glowing gas in the early Universe. The observations show for the first time that this giant “Lyman-alpha blob” — one of the largest single objects known — must be powered by galaxies embedded within it. The results appear in the 18 August issue of the journal Nature. Credit: ESO

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It’s called a Lyman-alpha blob and it’s one of the largest known single objects in the Universe. It first made its presence known in the year 2000 and we know it’s located some 11.5 billion light years away. What will really get your attention is the size. LAB-1 has a diameter of about 300,000 light-years across!

Utilizing ESO’s Very Large Telescope (VLT), a team of astronomers were checking out areas of the early Universe where matter was the most dense – home to huge and very luminous rare structures called Lyman-alpha blobs. While there wasn’t anything in particular they were looking for, what they captured was something unique… evidence of polarization.

“We have shown for the first time that the glow of this enigmatic object is scattered light from brilliant galaxies hidden within, rather than the gas throughout the cloud itself shining.” explains Matthew Hayes (University of Toulouse, France), lead author of the paper.

These super-sized clouds of hydrogen gas stagger the imagination with their sheer dimensions. Some reach diameters of a few hundred thousand light-years – large enough to enfold the Milky Way three times over – and are as luminous as the most powerful galaxy we can observe. Since Lyman-alpha blobs are located so far away, we can only see them as they were when the Universe was a few billion years old, but they have a lot to teach us about their origins. Some theories suggest they shine when cool gas is pulled in by the blob’s powerful gravity and heated. Other conjectures are they are illuminated from within – lit by extreme star-forming events, supernovae or hungry black holes swallowing matter.

Thanks to these recent studies, the latest idea is the illumination comes from embedded galaxies. How do astronomers know this? By measuring whether the light from the blob was polarized. By measuring the physical processes that produced the light with sensitive equipment, researchers can gain insight from scattering or reflecting properties. However, the task hasn’t been easy considering the great distance of Lyman-alpha blobs.

“These observations couldn’t have been done without the VLT and its FORS instrument. We clearly needed two things: a telescope with at least an eight-metre mirror to collect enough light, and a camera capable of measuring the polarisation of light. Not many observatories in the world offer this combination.” adds Claudia Scarlata (University of Minnesota, USA), co-author of the paper.

According to ESO, the team observed their target for about 15 hours with the Very Large Telescope, and the light from the Lyman-alpha blob LAB-1 showed a centralized ring of polarization – but no central polarized spot. “This effect is almost impossible to produce if light simply comes from the gas falling into the blob under gravity, but it is just what is expected if the light originally comes from galaxies embedded in the central region, before being scattered by the gas. The astronomers now plan to look at more of these objects to see if the results obtained for LAB-1 are true of other blobs.”

Before they find us…

Original Story Source: ESO Science News Release.

Posted on by Tammy Plotner

Red-Burning Galaxies… Let’s Get The Party Started!

An image illustrating the number density of galaxies estimated to be four billion light years from the Earth. Bright areas indicate high-density regions. The brightest region in the center corresponds to the main body of the CL0939 cluster. Red squares show the positions of the red -burning galaxies while the greenish-blue dots show the blue H? emitting galaxies. Evidently, the red burning galaxies avoid the central region of the cluster and concentrate in small groups located far away from it.

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Utilizing the Subaru Telescope, a research team of astronomers from the University of Tokyo and the National Astronomical Society of Japan (NAOJ) used a wide-field image to take a look four billion years back in time. The object of their interest was a galaxy cluster, but what really took their fancy wasn’t the old matrons – it was the red star-forming galaxies hanging around the edges.

Just exactly what is a “red-burning galaxy”? Astronomers hypothesize they might be the transitional key between the young and old… and present at a party that shows dramatic evolution. It’s not the fact that such galaxies exist within galactic clusters, but why they seem to appear along the outskirts.

When galaxies first began forming under the weight of their own gravity some ten billion years ago, they either became part of big clusters or small groups. As they came together, they took on properties of their environment – just as party goers tend to group together where interests are similar. At a galactic get-together with high density, galaxies form into lenticular or elliptical, while the solitary wall flowers tend toward spiral structure. But exactly how they form and evolve is one of astronomy’s greatest enigmas.

A panoramic view of the CL0939+4713 cluster located 4 billion light years away from Earth. Images were captured with the Subaru Prime Focus Camera (Suprime-Cam), all of which are a composite of a B-band image (blue), a R-band image (green), and a z'-band image (red). Left 27 arcmin x 27 arcmin field of view. Top-right: Close-up view of the central cluster region, 2.5 arcmin x 2.5 arcmin field of view. Bottom-right: Example of the concentration of red-burning galaxies, which are marked with red squares.

To help solve the mystery, researchers are looking further back into the past. A research team led by Dr. Yusei Koyama used the Subaru Prime Focus Camera (Suprime-Cam) to carry out a panoramic observation targeting a relatively well-known rich cluster, CL0939+4713. By using a special filter that separates the hydrogen-alpha emission lline Koyama’s team members identified more than 400 galaxies showing a narrowband excess which could denote the star formation process. Strangely enough, it was these very galaxies that showed an impressive amount of red and were located in groups well away from the main body.

Needless to say, this opened the door to even more questions. Where did they come from and why are they concentrated in groups and not clusters? At this point, who knows? Astronomers are positive the “red-burning galaxies” get their properties from starbirth – not elderly populations. They also anticipate the main galaxy cluster will one day absorb these strays into the main body as well. How can they tell? Just like the party, the red-burning galaxies are already changing in relationship to their environment. Older galaxies that no longer have active star-forming regions seem to be increasing in the groups, exactly where the red-burners are most frequently found.

“This suggests that the red-burning galaxies are related to the increase in old galaxies, and that they are likely to be in a transitional phase from a younger to an older generation. The finding that such transitional galaxies are located most frequently within group environments shows that galaxy groups are the key environments for understanding how environment shapes the evolution of galaxies.” says the Subaru research team. “This should be an important and exciting step toward a more complete understanding of the environments shaping the galaxies in the present-day Universe.”

Party on, dudes…

Original Story Source: Subaru Telescope Press Release.

Posted on by Jon Voisey

The Hidden Galaxy in the Zone of Avoidance

The Fornax dwarf galaxy is one of our Milky Way’s neighbouring dwarf galaxies and a good example of what an early dwarf galaxy might have been like. This image was composed from data from the Digitized Sky Survey 2. Credit: ESO
The Fornax dwarf galaxy is one of our Milky Way’s neighbouring dwarf galaxies and a good example of what an early dwarf galaxy might have been like. This image was composed from data from the Digitized Sky Survey 2. Credit: ESO

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There are some places astronomers dare not tread. One of the prime places is beyond the disk of our own galaxy where the numerous stars and clouds of dust along the line of sight make observations messy to say the least. This obscured portion of the sky is known as the Zone of Avoidance. But despite the challenges, one team of astronomers has searched through it and found a previously undiscovered galaxy lurking not too far from our own.

To discover this galaxy, the team, lead by graduate student Travis McIntyre at the University of New Mexico, used the gigantic Arecibo radio telescope. This telescope is adept at finding emission at the 21 centimeter wavelength emitted by cool, atomic hydrogen. This long wavelength is relatively immune to the diminishing effects of gas and dust within our galaxy.

After the initial discovery, the team followed up with further observation using the Expanded Very Large Array, which also operates in the radio, as well as the 0.9 meter Southeastern Association for Research in Astronomy telescope, which is an optical telescope, in hopes of peering through some of the muck.

While the galaxy was easily recovered in the second radio search, and the optical images showed a faint clump, the centers of the two did not appear to line up. The visual and radio components seemed not to overlap almost at all. A portion of the reason for this is that the team was unable to image the faint galaxy out to its full extent before the contamination from our own galaxy overwhelmed the signal. As such, the two likely overlap more than is indicated by the study, but this would still indicate that the distribution of hydrogen gas within it is severely lopsided.

Another possibility is that the object detected isn’t really a galaxy at all and is a coincidence of an alignment between a high velocity cloud and an independent cluster of stars. However, such clouds of gas tend to travel in packs and no others are known in the area, making this possibility unlikely.

If the object is a galaxy, it is likely a blue dwarf galaxy with some 10 million solar masses. The team expects that, while the galaxy is relatively nearby, this galaxy is not likely to bea member of the local group because, were it that close, it would be unprecedentedly small. As such, they applied Hubble’s Law to give a rough distance of 22 million light years but caution that at such distances, there is a large velocity dispersion and this estimate may be unreliable.

Searching for galaxies like this one in the Zone of Avoidance are important to astronomers because the mass of such undiscovered galaxies may help to resolve the unexpected “discrepancy between the cosmic microwave background dipole and what is expected from gravitational acceleration imparted on the Local Group by matter in the local universe.”

Posted on by Tammy Plotner

Alone In The Dark?

This is the portion of sky in which astronomers found the Segue 1 dwarf galaxy. Can you see it? Credit: Marla Geha

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Two years ago, Marla Geha, a Yale University astronomer, Joshua Simon from the Carnegie Institution of Washington, and their colleagues discovered something unusual while studying with the Keck II telescope and information for the Sloan Digital Sky Survey. Their observations turned up a contrasting group of stars which all appeared to be moving in unison – not just a moving cluster of similar stars which could have been torn away from the nearby Sagittarius dwarf galaxy. The team knew they were on to something, but a competing group of astronomers at Cambridge University was skeptical. Too bad… there was a dark treasure right there before their eyes.

Not to be dissuaded, Simon, Geha and their group returned to Keck and turned the photographic eye of the telescope’s Deep Extragalactic Imaging Multi-Object Spectrograph (DEIMOS) towards their target area. Even though it was only about 1,000 small, dim stars, they wanted to know how they migrated both in respect to the Milky Way and to each other. Named Segue 1, the target the team was looking at could possibly have 3,400 times more mass than can be accounted for by its visible stars… a galaxy dominated by dark matter and salted with a handful of ancient suns. If the 1,000 or so stars were all there was to Segue 1, with just a touch of dark matter, the stars would all move at about the same speed, said Simon. But the Keck data show they do not. Instead of moving at a steady 209 km/sec relative to the Milky Way, some of the Segue 1 stars are moving at rates as slow as 194 kilometers per second while others are going as fast as 224 kilometers per second.

Using the DEIMOS instrument on the Keck II telescope, astronomers could identify which stars were moving together as a group. They are circled here in green Credit: Marla Geha

“That tells you Segue 1 must have much more mass to accelerate the stars to those velocities,” Geha explained. The paper confirming Segue 1’s dark nature appeared in the May 2011 issue of The Astrophysical Journal. “The mass required to cause the different star velocities seen in Segue 1 has been calculated at 600,000 solar masses. But there are only about 1,000 stars in Segue 1, and they are all close to the mass of our Sun,” Simon said. “Virtually all of the remainder of the mass must be dark matter.”

But the information from DEIMOS didn’t stop there… It also revealed an eclectic collection of nearly primordial metal-poor stars. The researchers managed to gather iron data on six stars in Segue 1 with the Keck II telescope, and a seventh Segue 1 star was measured by an Australian team using the Very Large Telescope. Of those seven, three proved to have less than one 2,500th as much iron as the Sun. “That suggests these are some of the oldest and least evolved stars that are known,” said Simon. This is fascinating data considering investigations for stars of this type out of the Milky Way’s billions have produced less than 30. “In Segue 1 we already have 10 percent of the total in the Milky Way,” Geha said. “For studying these most primitive stars, dwarf galaxies are going to be very important.”

By subtracting out all the other objects in the image and leaving the Segue I member stars, the “darkest galaxy” emerges. Credit: Marla Geha

By confirming Segue 1’s massive concentration of dark matter, other types of research into this dark galaxy’s lifestyle now become more dedicated. The space-based Fermi Gamma Ray Telescope has also been looking its way in hopes of catching a gamma-ray event created by the collision and annihilation of pairs of dark matter particles. So far the Fermi telescope has not detected anything of the sort, which isn’t entirely surprising and doesn’t mean the dark matter isn’t there, said Simon.

“The current predictions are that the Fermi telescope is just barely strong enough or perhaps not quite strong enough to see these gamma rays from Segue 1,” Simon explained. So there are hopes that Fermi will detect at least the hint of a collision. “A detection would be spectacular,” said Simon. “People have been trying to learn about dark matter for 35 years and not made much progress. Even a faint glow of the predicted gamma rays would be a powerful confirmation of theoretical predictions about the nature of dark matter.”

Let’s hope Segue 1 isn’t alone in the dark.

Original News Source: Keck Observatory Science News.

Posted on by Tammy Plotner

Voorwerpje… And Away!

UGC 7342 in H-Alpha - Credit: Galaxy Zoo

[/caption]It’s 28 pages long and it has been submitted to the Monthly Notices of the Royal Astronomical Society. It’s filled with exciting new discoveries. What is it? Try the Galaxy Zoo’s latest findings… the Great Voorwerpje Round-up!

“Eighteen thousand candidate active galactic nuclei. One hundred ninety-nine Zooites. A hundred fifty-four possible galaxies with clouds, of which 49 became targets for spectra. And finally, nineteen certified Voorwerpjes – giant clouds of gas ionized by a central active nucleus, like Hanny’s Voorwerp but smaller (and sometimes not all that much smaller) and dimmer.” says Bill Keel. “Of these clouds, many (including the largest) are new discoveries.”

The Galaxy Zoo has been on the hunt and what they’ve found has proved to be very exciting to the team. Says Keel: “About half of these have gas too highly ionized too far from the nucleus to account for by the nucleus we see (even including far-infrared results to tell how much radiation is being absorbed by dust), so they may be additional, less dramatic instances of the AGN fading over time spans of 100,000 years or so. This large fraction suggests that at least Seyfert nuclei may constantly be brightening and fading over times of a few hundred thousands years (a time span about which we’ve previously had almost no information).”

Their images include those taken with filters that isolate [O III] or Ha emission – even subtracting ordinary starlight. In one such image of UGC 7342, they could trace gas out to twice the estimated size of the Milky Way! This could mean the presence of an AGN. “Starlight doesn’t have enough far-ultraviolet or X-rays to make gas that highly ionized, but an active galactic nucleus does. Furthermore, the ratios of these lines let us estimate how intense this radiation is when it reaches a cloud.” comments Keel. “Even though UGC 7342 is pretty chewed up because of an interaction with at least one companion, the gas motions aren’t as chaotic as they might be – the gas isn’t orbiting retrograde or anything.”

Their research is shedding new light on Voorwerpje mysteries – giving consistencies to ionized clouds located in galaxies which are interacting or merging – and accounting for tidal disturbances. Preliminary findings also show a symmetry as well, where around 50% of the galaxies studied show two ionized clouds on opposite sides.

“Of course, we want to know more. Answers tend to multiply questions. Hubble observations are scheduled, and (with a little luck) X-ray measurements with ESA’s XMM-Newton observatory. We’ve managed to interest some of the people at ASTRON in the Netherlands in using the Westerbork array to examine the cold hydrogen around these galaxies.” says Keel. “In addition, we’re doing new observations of various samples of active and “nonactive” galaxies to look for fainter, and maybe older, gas clouds. Special thanks to everyone who participated in this project, either through the targeted hunt or the complementary forum search for clouds in galaxies not listed as AGN. Stay tuned!”

You can bet we will…

Original Story Source: Zooniverse Blog.