Mar 27, 2017

The electric sands of Titan

This composite image shows an infrared view of Saturn's moon Titan from NASA's Cassini spacecraft, acquired during the mission's "T-114" flyby on Nov. 13, 2015.
Experiments led by researchers at the Georgia Institute of Technology suggest the particles that cover the surface of Saturn's largest moon, Titan, are "electrically charged." When the wind blows hard enough (approximately 15 mph), Titan's non-silicate granules get kicked up and start to hop in a motion referred to as saltation. As they collide, they become frictionally charged, like a balloon rubbing against your hair, and clump together in a way not observed for sand dune grains on Earth -- they become resistant to further motion. They maintain that charge for days or months at a time and attach to other hydrocarbon substances, much like packing peanuts used in shipping boxes here on Earth.

The findings have just been published in the journal Nature Geoscience.

"If you grabbed piles of grains and built a sand castle on Titan, it would perhaps stay together for weeks due to their electrostatic properties," said Josef Dufek, the Georgia Tech professor who co-led the study. "Any spacecraft that lands in regions of granular material on Titan is going to have a tough time staying clean. Think of putting a cat in a box of packing peanuts."

The electrification findings may help explain an odd phenomenon. Prevailing winds on Titan blow from east to west across the moon's surface, but sandy dunes nearly 300 feet tall seem to form in the opposite direction.

"These electrostatic forces increase frictional thresholds," said Josh Méndez Harper, a Georgia Tech geophysics and electrical engineering doctoral student who is the paper's lead author. "This makes the grains so sticky and cohesive that only heavy winds can move them. The prevailing winds aren't strong enough to shape the dunes."

To test particle flow under Titan-like conditions, the researchers built a small experiment in a modified pressure vessel in their Georgia Tech lab. They inserted grains of naphthalene and biphenyl -- two toxic, carbon and hydrogen bearing compounds believed to exist on Titan's surface -- into a small cylinder. Then they rotated the tube for 20 minutes in a dry, pure nitrogen environment (Titan's atmosphere is composed of 98 percent nitrogen). Afterwards, they measured the electric properties of each grain as it tumbled out of the tube.

"All of the particles charged well, and about 2 to 5 percent didn't come out of the tumbler," said Méndez Harper. "They clung to the inside and stuck together. When we did the same experiment with sand and volcanic ash using Earth-like conditions, all of it came out. Nothing stuck."

Earth sand does pick up electrical charge when it's moved, but the charges are smaller and dissipate quickly. That's one reason why you need water to keep sand together when building a sand castle. Not so with Titan.

"These non-silicate, granular materials can hold their electrostatic charges for days, weeks or months at a time under low-gravity conditions," said George McDonald, a graduate student in the School of Earth and Atmospheric Sciences who also co-authored the paper.

Visually, Titan is the object in the solar system most like Earth. Data gathered from multiple flybys by Cassini since 2005 have revealed large liquid lakes at the poles, as well as mountains, rivers and potentially volcanoes. However, instead of water-filled oceans and seas, they're composed of methane and ethane and are replenished by precipitation from hydrocarbon-filled clouds. Titan's surface pressure is a bit higher than our planet -- standing on the moon would feel similar to standing 15 feet underwater here on Earth.

Read more at Science Daily

Stars born in winds from supermassive black holes

Artist's impression of stars born in winds from supermassive black holes.
Observations using ESO's Very Large Telescope have revealed stars forming within powerful outflows of material blasted out from supermassive black holes at the cores of galaxies. These are the first confirmed observations of stars forming in this kind of extreme environment. The discovery has many consequences for understanding galaxy properties and evolution. The results are published in the journal Nature.

A UK-led group of European astronomers used the MUSE and X-shooter instruments on the Very Large Telescope (VLT) at ESO's Paranal Observatory in Chile to study an ongoing collision between two galaxies, known collectively as IRAS F23128-5919, that lie around 600 million light-years from Earth. The group observed the colossal winds of material -- or outflows -- that originate near the supermassive black hole at the heart of the pair's southern galaxy, and have found the first clear evidence that stars are being born within them.

Such galactic outflows are driven by the huge energy output from the active and turbulent centres of galaxies. Supermassive black holes lurk in the cores of most galaxies, and when they gobble up matter they also heat the surrounding gas and expel it from the host galaxy in powerful, dense winds.

"Astronomers have thought for a while that conditions within these outflows could be right for star formation, but no one has seen it actually happening as it's a very difficult observation," comments team leader Roberto Maiolino from the University of Cambridge. "Our results are exciting because they show unambiguously that stars are being created inside these outflows."

The group set out to study stars in the outflow directly, as well as the gas that surrounds them. By using two of the world-leading VLT spectroscopic instruments, MUSE and X-shooter, they could carry out a very detailed study of the properties of the emitted light to determine its source.

Radiation from young stars is known to cause nearby gas clouds to glow in a particular way. The extreme sensitivity of X-shooter allowed the team to rule out other possible causes of this illumination, including gas shocks or the active nucleus of the galaxy.

The group then made an unmistakable direct detection of an infant stellar population in the outflow. These stars are thought to be less than a few tens of millions of years old, and preliminary analysis suggests that they are hotter and brighter than stars formed in less extreme environments such as the galactic disc.

As further evidence, the astronomers also determined the motion and velocity of these stars. The light from most of the region's stars indicates that they are travelling at very large velocities away from the galaxy centre -- as would make sense for objects caught in a stream of fast-moving material.

Co-author Helen Russell (Institute of Astronomy, Cambridge, UK) expands: "The stars that form in the wind close to the galaxy centre might slow down and even start heading back inwards, but the stars that form further out in the flow experience less deceleration and can even fly off out of the galaxy altogether."

Read more at Science Daily

Planetary waves, first found on Earth, are discovered on sun

The Sun.
The same kind of large-scale planetary waves that meander through the atmosphere high above Earth's surface may also exist on the Sun, according to a new study led by a scientist at the National Center for Atmospheric Research (NCAR).

Just as the large-scale waves that form on Earth, known as Rossby waves, influence local weather patterns, the waves discovered on the Sun may be intimately tied to solar activity, including the formation of sunspots, active regions, and the eruption of solar flares.

"The discovery of magnetized Rossby waves on the Sun offers the tantalizing possibility that we can predict space weather much further in advance," said NCAR scientist Scott McIntosh, lead author of the paper.

The study will be published March 27 in the journal Nature Astronomy. Co-authors are William Cramer of Yale University, Manuel Pichardo Marcano of Texas Tech University, and Robert Leamon of the University of Maryland, College Park.

The research was funded by the National Science Foundation (NSF), which is NCAR's sponsor, and by NASA.

An unprecedented view of the Sun

On Earth, Rossby waves are associated with the path of the jet stream and the formation of low- and high-pressure systems, which in turn influence local weather events.

The waves form in rotating fluids -- in the atmosphere and in the oceans. Because the Sun is also rotating, and because it's made largely of plasma that acts, in some ways, like a vast magnetized ocean, the existence of Rossby-like waves should not come as a surprise, said McIntosh, who directs NCAR's High Altitude Observatory.

And yet scientists have lacked the tools to distinguish this wave pattern until recently. Unlike Earth, which is scrutinized at numerous angles by satellites in space, scientists historically have been able to study the Sun from only one viewpoint: as seen from the direction of Earth.

But for a brief period, from 2011 to 2014, scientists had the unprecedented opportunity to see the Sun's entire atmosphere at once. During that time, observations from NASA's Solar Dynamics Observatory (SDO), which sits between the Sun and the Earth, were supplemented by measurements from NASA's Solar TErrestrial RElations Observatory (STEREO) mission, which included two spacecraft orbiting the Sun. Collectively, the three observatories provided a 360-degree view of the Sun until contact was lost with one of the STEREO spacecraft in 2014. McIntosh and his co-authors mined the data collected during the window of full solar coverage to see if the large-scale wave patterns might emerge.

"By combining the data from all three satellites we can see the entire sun and that's important for studies like this because you want the measurements to all be at the same time," said Dean Pesnell, SDO project scientist at NASA's Goddard Space Flight Center in Greenbelt, Maryland. "They're pushing the boundary of how we use solar data to understand the interior of the sun and where the magnetic field of the sun comes from."

Finding waves in the data

The team used images taken by instruments on SDO and STEREO to identify and track coronal bright points. These small bright features dot the entire face of the Sun and have been used to track motions deeper in the solar atmosphere.

The scientists plotted the combined data on Hovmöller diagrams, a diagnostic tool developed by meteorologists to highlight the role of waves in Earth's atmosphere. What emerged from the analysis were bands of magnetized activity that propagate slowly across the Sun -- just like the Rossby waves found on Earth.

The discovery could link a range of solar phenomena that are also related to the Sun's magnetic field, including the formation of sunspots, their lifetimes, and the origin of the Sun's 11-year solar cycle. "It's possible that it's all tied together, but we needed to have a global perspective to see that," McIntosh said. "We believe that people have been observing the impacts of these Rossby-like waves for decades, but haven't been able to put the whole picture together."

With a new understanding of what the big picture might really look like, scientists could take a step closer to predicting the Sun's behavior.

"The discovery of Rossby-like waves on the Sun could be important for the prediction of solar storms, the main drivers of space weather effects on Earth," said Ilia Roussev, program director in NSF's Division of Atmospheric and Geospace Sciences. "Bad weather in space can hinder or damage satellite operations, and communication and navigation systems, as well as cause power-grid outages leading to tremendous socioeconomic losses. Estimates put the cost of space weather hazards at $10 billion per year."

Read more at Science Daily

Using Latin to analyse other languages

The Latin translation next to the Arabic text helps represent the grammar and contents structure of the original better than a direct German translation would have done.
Bochum-based philologist Prof Dr Reinhold Glei has figured out why Latin still turned up in many documents in the 17th to 19th centuries, even though it had not been a spoken language for a long time. During that period, Latin served as an instrument for translating languages that had hitherto been little known in Western culture.

Scholars recreated the foreign-language sentences with the aid of Latin, thus crafting a text upon which further analyses could be based. In doing so, translators didn't have to conform to specific linguistic rules of the Latin language, because native speakers no longer existed who might have taken exception to an unusual syntax in Latin.

Arabic, Chinese, Sanskrit: novel sentence structures in those languages posed a challenge to scholars in the Early Modern Period. "Had the foreign-language texts been translated into, for example, German, the translator would have been restricted by the respective grammatical structures. Using Latin, the translators had more freedom," elaborates Glei.

Representing linguistic structures

The philologist refers to this method as epilanguage; the Greek word epi translates as "on" or "above." Latin was superimposed over the foreign language. Thus, translators were able to represent the unfamiliar structures.

Reinhold Glei compiled his results by studying Arabic, Chinese and Persian texts and their respective translations from the period between the 17th and 19th centuries. He analysed, for example, various Quran translations. By comparing excerpts from the Latin translations with the originals, Glei identified to what extent the Latin versions reflected the structure of the original language.

An advantage of using the epilanguage was that it enabled translators to draw up neutral texts, before translating them into their respective vernacular language. "When Christians initially translated the Quran, the texts they created were for the most part ideologically charged. This resulted in corrupted translations," he says. Using Latin as epilanguage did not wholly eradicate the problem, but it was possible to represent the structure of the Arabic language in a more neutral manner.

Future perspectives

Research into epilanguage is still in its early stages. Reinhold Glei intends to analyse additional Latin translations from various languages, in order to gain a better grasp of the function of epilanguage. Glei also wishes to study another world language, namely Ancient Greek, in greater detail. His first impression is: "Ancient Greek appears to occur less frequently as epilanguage. This might be because the language is not dead; it lives on in Modern Greek."

From Science Daily

'Australia's Jurassic Park' the world's most diverse

Dinosaur tracks in the Walmadany area are shown.
An unprecedented 21 different types of dinosaur tracks have been identified on a 25-kilometre stretch of the Dampier Peninsula coastline dubbed "Australia's Jurassic Park."

A team of palaeontologists from The University of Queensland's School of Biological Sciences and James Cook University's School of Earth and Environmental Sciences braved sharks, crocodiles, massive tides and the threat of development to unveil the most diverse assemblage of dinosaur tracks in the world in 127 to 140 million-year-old rocks in the remote Kimberley region of Western Australia.

Lead author Dr Steve Salisbury said the diversity of the tracks around Walmadany (James Price Point) was globally unparalleled and made the area the "Cretaceous equivalent of the Serengeti."

"It is extremely significant, forming the primary record of non-avian dinosaurs in the western half the continent and providing the only glimpse of Australia's dinosaur fauna during the first half of the Early Cretaceous Period," Dr Salisbury said.

"It's such a magical place -- Australia's own Jurassic Park, in a spectacular wilderness setting."

In 2008, the Western Australian Government selected Walmadany as the preferred site for a $40 billion liquid natural gas processing precinct.

The area's Traditional Custodians, the Goolarabooloo people, contacted Dr Salisbury and his team, who dedicated more than 400 hours to investigating and documenting the dinosaur tracks.

"We needed the world to see what was at stake," Goolarabooloo Law Boss Phillip Roe said.

The dinosaur tracks form part of a song cycle that extends along the coast and then inland for 450 km, tracing the journey of a Dreamtime creator being called Marala, the Emu man.

"Marala was the Lawgiver. He gave country the rules we need to follow. How to behave, to keep things in balance," Mr Roe said said.

"It's great to work with UQ researchers. We learnt a lot from them and they learnt a lot from us."

Dr Salisbury said the surrounding political issues made the project "particularly intense," and he was relieved when National Heritage listing was granted to the area in 2011 and the gas project collapsed in 2013.

"There are thousands of tracks around Walmadany. Of these, 150 can confidently be assigned to 21 specific track types, representing four main groups of dinosaurs, " Dr Salisbury said.

"There were five different types of predatory dinosaur tracks, at least six types of tracks from long-necked herbivorous sauropods, four types of tracks from two-legged herbivorous ornithopods, and six types of tracks from armoured dinosaurs.

"Among the tracks is the only confirmed evidence for stegosaurs in Australia. There are also some of the largest dinosaur tracks ever recorded. Some of the sauropod tracks are around 1.7 m long."

Read more at Science Daily

Mar 26, 2017

How chewing like a cow helped early mammals thrive

UChicago graduate student David Grossnickle explains key features that evolved to facilitate jaw yaw, or side-to-side movement that cows do, that allowed early mammals to expand their diet.
You probably haven't given much thought to how you chew, but the jaw structure and mechanics of almost all modern mammals may have something to do with why we're here today. In a new paper published this week in Scientific Reports, David Grossnickle, a graduate student in the Committee on Evolutionary Biology at the University of Chicago, proposes that mammal teeth, jaw bones and muscles evolved to produce side-to-side motions of the jaw, or yaw, that allowed our earliest ancestors to grind food with their molars and eat a more diversified diet. These changes may have been a contributing factor to their survival of the mass extinction at the end of the Cretaceous Period 66 million years ago.

The terms "pitch" and "yaw" usually describe movements of airplanes, but biologists also use them to describe basic movements of body parts such as the jaw. Pitch rotation results in basic up and down movement, and yaw rotation results in side-to-side, crosswise motion (think of a cow munching away on some grass). Almost all modern mammals, including placental mammals, like humans and deer, and marsupials, like kangaroos and opossums, share similarities in their jaw structures and musculature that allow for both pitch and yaw movements. This allows mammals to have especially diverse diets today, from cutting pieces of meat to grinding tough plants and vegetables. For early mammals, these characteristics meant they could be more resourceful during tough times.

"If you have a very specialized diet you're more likely to perish during a mass extinction because you're only eating one thing," Grossnickle said. "But if you can eat just about anything and 90 percent of your food goes away, you can still live on scraps."

Using 2D images of early mammal fossils from previous publications and 3D data collected from modern specimens at the Field Museum, Grossnickle analyzed the structure of teeth, jaw bones, and how the muscles that control them were attached to the skull. He saw that as species began to develop a projection on the upper molars that fit into a corresponding cup or basin on their lower counterparts, the musculature of the jaw also changed to provide greater torque for side-to-side yaw movements. This way the animal could grind its food between the molars like a mortar and pestle, as opposed to cutting it with simple up and down pitch movements.

Grossnickle, who works in the lab of Zhe-Xi Luo, PhD, professor of organismal biology and anatomy, studies the early origins of mammals, and is interested in broader questions about why certain mammal groups have diversified through time and survived extinction events. He says the adaptations of the jaws and teeth may have been key.

Read more at Science Daily

How cheetahs stay fit and healthy

Handling cheetahs an farmland in Namibia.
Cheetahs are categorized as vulnerable species, partly because they have been considered to be prone to diseases due to their supposed weak immune system. However, they are hardly ever sick in the wild. A research team from the German Leibniz Institute for Zoo and Wildlife Research (IZW) recently discovered that cheetahs have developed a very efficient innate "first line of defense" immunity to compensate potential deficiencies in other components of their immune system. The scientists have published their results in the open access journal Scientific Reports of the Nature Publishing Group.

Cheetahs have a relatively low genetic variability which means that, within a population, the individuals have a similar genetic makeup. This is also true for the major histocompatibility complex (MHC), a genome region that regulates the so-called "adaptive" immune system and is typically highly variable in animal species. The adaptive immune system provides a rapid and specific defense against pathogens, if they have been encountered previously. A low MHC variability should therefore result in a weak adaptive immune system and thus a high vulnerability to diseases. This is often the case in species with low MHC variability, but there are some exceptions, the cheetah indeed being one of them. "During our long-term study that begun in 2002, we investigated more than 300 free-ranging cheetahs that live on farmland in Namibia. We did not encounter any cheetah with symptoms of acute infections, nor did we detect lesions in the examined dead animals," explains Bettina Wachter, head of the cheetah research project.

How can cheetahs cope so well with pathogens despite their supposedly weak adaptive immunity? The immune system is divided into three components:(1) the constitutive innate immune system, which provides a rapid first line of defense against intruders, (2) the induced innate immune system such as the local and systemic inflammatory response, which enhances recovery and decreases pathogen growth, and (3) the adaptive immune system.

"We decided to investigate all three components simultaneously, an approach that is rarely done although it is very promising. For every animal, a well-functioning immune system is associated with certain energetic costs. However, this does not imply that all immune components are equally strongly developed. If a species is not vulnerable to diseases, a good immune response must have evolved by strengthening other parts of the immune system," says Gábor Czirják, wildlife immunologist at the Leibniz-IZW.

To compare the results with another species, the scientists included leopards in the study. "Leopards live in the same habitat as cheetahs in Namibia, but they have a high variability in their MHC. Thus, leopards should have a strong adaptive immune system and might not invest that much energy in the other parts of the immune system," explains Wachter.

"We first needed to adapt six immunological tests from the toolbox of the wildlife immunology for the cheetah and leopard," explains Sonja Heinrich, first author of the study. "We conducted these tests at the laboratory of the Leibniz IZW, thus needed to transport the samples we collected in Namibia all the way to Germany, keeping the cooling chain uninterrupted from the captured animal in the field to the Leibniz IZW." The immunological tests confirmed that leopards have a stronger adaptive immune system than cheetahs, consistent with the differences in the MHC variability of both species. As expected, cheetahs had a stronger innate "first line of defense" immune system than leopards, thereby probably compensating their weak adaptive immune system.

The induced innate immune system reacts to pathogen intruders as well as to temporary stress. Therefore, the scientists also determined the concentration of the hormone cortisol, which activates catabolic processes and is increasingly released during stress. Although both species were exposed to the same capture and handling procedures leopards had significantly higher cortisol concentration in their blood than cheetahs, indicating that leopards reacted stronger to the examination methods. Thus, short-term stress might have stimulated the induced innate immune system, making it difficult to assess whether this immune part also helps to compensate the weak adaptive immune system of cheetahs, if the stress effect is not considered.

Read more at Science Daily

Mar 25, 2017

Scientists make new discovery about bird evolution

Chinese countryside (stock image). The new specimen from the rich Early Cretaceous Jehol Biota comes only from the 130.7 Ma Huajiying Formation deposits in Hebei, which preserves the second oldest known fossil birds. Birds from this layer are very rare.
In a new paper published in National Science Review, a team of scientists from the Institute of Vertebrate Paleontology and Paleoanthropology, the Shandong Tianyu Museum of Nature, and the Nanjing Institute of Geology and Paleontology (all in China) described the most exceptionally preserved fossil bird discovered to date.

The new specimen from the rich Early Cretaceous Jehol Biota (approximately 131 to 120 million years old) is referred to as Eoconfuciusornis, the oldest and most primitive member of the Confuciusornithiformes, a group of early birds characterized by the first occurrence of an avian beak. Its younger relative Confuciusornis is known from thousands of specimens but this is only the second specimen of Eoconfuciusornis found. This species comes only from the 130.7 Ma Huajiying Formation deposits in Hebei, which preserves the second oldest known fossil birds. Birds from this layer are very rare.

This new specimen of Eoconfuciusornis, housed in the Shandong Tianyu Museum of Nature, in Eastern China, is a female. The ovary reveals developing yolks that vary in size, similar to living birds. This suggests that confuciusornithiforms evolved a period of rapid yolk deposition prior to egg-laying (crocodilians, which are archosaurs like birds, deposit yolks slowly in all eggs for months with no period of rapid yolk formation), which is indicative of complex energetic profiles similar to those observed in birds.

This means Eoconfuciusornis and its kin, like living birds, was able to cope with extremely high metabolic demands during early growth and reproduction (whereas energetic demands in crocodiles are even, lacking complexity). In contrast, other Cretaceous birds including the more advanced group the Enantiornithes appear to have lower metabolic rates and have required less energy similar to crocodilians and non-avian dinosaurs (their developing yolks show little size disparity indicating no strong peak in energy associated with reproduction, and much simpler energetic profiles, limited by simpler physiologies).

Traces of skin indicate that the wing was supplemented by flaps of skin called patagia. Living birds have numerous wing patagia that help the bird to fly. This fossil helps show how bird wings evolved. The propatagium (the flap of skin that connects the shoulder and wrist) and postpatagium (the flap of skin that extends off the back of the hand and ulna) evolved before the alular patagium (the flap of skin connecting the first digit to the rest of the hand), which is absent in Eoconfuciusornis. Even more unique is the preservation of the internal structure of the propatagium which reveal a collagenous network identical to that in living birds. This internal network gives the skin flap its shape, allowing it to generate aerodynamic lift and aid the bird in flight.

The nearly complete plumage preserves remnants of the original plumage pattern, revealing the presence of spots on the wings and the earliest documentation of sexual differences in plumage within birds. This new specimen suggests that female Eoconfuciusornis were smaller than males and lacked tail feathers, similar to many sexually dimorphic living birds and the younger Confuciusornis in which the plumage of the males and females are different from each other. Samples of the feathers viewed under a microscope reveal differences in color characteristics, allowing scientists to reconstruct the plumage. Female Eoconfuciusornis had black spotted wings and gray body with a red throat patch.

Researchers have not found fossils from any other bird from the Jehol period that reveal so many types of soft tissue (feathers, skin, collagen, ovarian follicles). These remains allow researchers to create the most accurate reconstruction of a primitive early bird (or dinosaur) to date. This information provides better understanding of flight function in the primitive confuciusornithiforms and of the evolution of advanced flight features within birds.

Read more at Science Daily

Ravens: Non-breeders live in highly dynamic social groups

Ravens have impressive cognitive skills when interacting with conspecifics.
Several recent studies have revealed that ravens are among the most intelligent species of birds and even species in general. But which factors caused the evolution of intelligence? According to a common hypothesis life in social groups can drive brain evolution especially when individuals benefit from remembering the identity of conspecifics and the interactions with them. With such knowledge, animals can avoid conflicts with higher ranking group members or develop alliances to gain better access to resources.

Researchers around Thomas Bugnyar in Austria and colleagues in France outfitted around 30 ravens with little "backpacks," which measured with GPS the position of the animal every hour. The devices were charged with solar power and the data were transmitted using the GSM network for mobile phones. During the last four years of data collection movements up to 160 kilometers per day were observed. In addition in Austria and Italy a total number of 332 ravens have been marked individually with colored rings and wing-tags and their presence patterns in two study sites were monitored over years.

Conclusion of the biologists: While some non-breeding ravens seem to stay only in relatively small areas, others may move thousands of kilometers per year. Still many ravens meet repeatedly in different locations usually at rich food sources (e.g. landfills, compost stations) and adjacent common night roosts. "We were surprised about the similarity to humans: Some people prefer to spend their entire life in a single city or even a small village, while others want to travel and explore the world. We find exactly the same in non-breeding ravens," says lead-author Matthias Loretto.

When ravens form groups they make friends but also fight heavily with other group members for access to resources. "Every time a raven joins a group of conspecifics at food sources, it can benefit from remembering previous interactions to decide who is friend or foe. The combination of social bonds within non-breeders and such a highly dynamic system might have driven brain evolution in ravens," ends Loretto.

From Science Daily

Mar 24, 2017

Milky Way-like galaxies in early universe embedded in 'super halos'

Artist impression of a progenitor of Milky Way-like galaxy in the early universe with a background quasar shinning through a 'super halo' of hydrogen gas surrounding the galaxy. New ALMA observations of two such galaxies reveal that these vast halos extend well beyond the galaxies' dusty, star-forming disks. The galaxies were initially found by the absorption of background quasar light passing through the galaxies. ALMA was able to image the ionized carbon in the galaxies' disks, revealing crucial details about their structures.
By harnessing the extreme sensitivity of the Atacama Large Millimeter/submillimeter Array (ALMA), astronomers have directly observed a pair of Milky Way-like galaxies seen when the universe was only eight percent of its current age. These progenitors of today's giant spiral galaxies are surrounded by "super halos" of hydrogen gas that extend many tens-of-thousands of light-years beyond their dusty, star-filled disks.

Astronomers initially detected these galaxies by studying the intense light from even-more-distant quasars. As this light travels through an intervening galaxy on its way to Earth, it can pick up the unique spectral signature from the galaxy's gas. This technique, however, normally prevents astronomers from seeing the actual light emitted by the galaxy, which is overwhelmed by the much brighter emission from the background quasar.

"Imagine a tiny firefly next to a high-power search light. That's what astronomers are up against when it comes to observing these youthful versions of our home galaxy," said Marcel Neeleman a postdoctoral fellow at the University of California, Santa Cruz, and lead author on a paper appearing in the journal Science. "We can now see the galaxies themselves, which gives us an amazing opportunity to learn about the earliest history of our own galaxy and others like it."

With ALMA, the astronomers were finally able to observe the natural millimeter-wavelength "glow" emitted by ionized carbon in the dense and dusty star-forming regions of the galaxies. This carbon signature, however, is considerably offset from the gas first detected by quasar absorption. This extreme separation indicates that the galaxies' gas content extends well beyond their star-filled disks, suggesting that each galaxy is embedded in a monstrous halo of hydrogen gas.

"We had expected we would see faint emissions right on top of the quasar, and instead we saw strong bright carbon emission from the galaxies at large separations from their background quasars," said J. Xavier Prochaska, professor of astronomy and astrophysics at UC Santa Cruz and coauthor of the paper. The separation from the quasar to the observed galaxy is about 137,000 light-years for one galaxy and about 59,000 light-years for the other.

According to the researchers, the neutral hydrogen gas revealed by its absorption of quasar light is most likely part of a large halo or perhaps an extended disk of gas around the galaxy. "It's not where the star formation is, and to see so much gas that far from the star-forming region means there is a large amount of neutral hydrogen around the galaxy," Neeleman said.

The new ALMA data show that these young galaxies are already rotating, which is one of the hallmarks of the massive spiral galaxies we see in the universe today. The ALMA observations further reveal that both galaxies are forming stars at moderately high rates: more than 100 solar masses per year in one galaxy and about 25 solar masses per year in the other.

"These galaxies appear to be massive, dusty, and rapidly star-forming systems, with large, extended layers of gas," Prochaska said.

"ALMA has solved a decades-old question on galaxy formation," said Chris Carilli, an astronomer with the National Radio Astronomy Observatory in Socorro, N.M., and co-author on the paper. "We now know that at least some very early galaxies have halos that are much more extended that previously considered, which may represent the future material for galaxy growth."

Read more at Science Daily