Floyd inflatable pig goes missing

By the BBC

The inflatable appeared at the Coachella festival in California

Enlarge Image

A reward has been offered for a giant inflatable pig which floated into the Californian desert during a concert by ex-Pink Floyd star Roger Waters.

Organisers of the Coachella Festival have put up a $10,000 (£5,090) bounty, plus tickets for life, for its return.

The pig, which is the width of two buses, has a checked ballot box for US presidential hopeful Barack Obama painted on its underbelly.

Waters said "that's my pig" as it drifted away during Sunday's gig.

The animal's flanks bear the slogans "fear builds walls" and "don't be led to the slaughter", with a cartoon of Uncle Sam holding two meat cleavers.

Prototype pig

Coachella spokeswoman Marcee Rondan said: "It wasn't really supposed to happen that way.

"People are putting search teams together to find this pig.

"But it may never be seen again," she added, saying the inflatable was likely to lose air as its journey continued.

The pig was tethered to the ground with ropes and floated away as Waters was playing one of the versions of Pink Floyd song Pigs.

The group have used inflatable pigs during their concerts in the past, and the lost animal was the same prototype as all the others, according to Ms Rondan.

The festival are asking for anyone with any information about the pig to contact them on lostpig@coachella.com.

'Free Tibet' flags made in China

From the BBC

Police in southern China have discovered a factory manufacturing Free Tibet flags, media reports say.

The factory in Guangdong had been completing overseas orders for the flag of the Tibetan government-in-exile.

Workers said they thought they were just making colourful flags and did not realise their meaning.

But then some of them saw TV images of protesters holding the emblem and they alerted the authorities, according to Hong Kong's Ming Pao newspaper.

Tibet independence

The factory owner reportedly told police the emblems had been ordered from outside China, and he did not know that they stood for an independent Tibet.

Workers who had grown suspicious checked the meaning of the flag by going online.

Thousands of flags had already been packed for shipping.

Police believe that some may already have been sent overseas, and could appear in Hong Kong during the Olympic torch relay there this week.

Known as the Snow Lion Flag Introduced in 1912 Banned in mainland China Inside Tibet: Clickable guide

The authorities have now stepped up the inspection of cars heading to the Shenzhen Special Economic Zone and onwards to Hong Kong.

The Olympic torch is due to tour Hong Kong on Friday. It will then travel to a series of cities in mainland China before reaching Beijing for the start of the Olympic Games in August.

Its progress around the world has been marked by pro-Tibet demonstrations in several cities - including Paris, London and San Francisco.

Rallies began in the main Tibetan city of Lhasa on 10 March, led by Buddhist monks.

Over the following week protests spread and became violent - particularly in Lhasa, where ethnic Chinese were targeted and shops were burnt down.

Beijing cracked down on the protesters with force, sending in hundreds of troops to regain control of the restive areas.

But it has since agreed to resume talks with representatives of the Dalai Lama.

A Brain Cell is the Same as the Universe

by Cliff Pickover, Reality Carnival

Ancient Praying Mantis Found in Amber

Julian Ryall in Tokyo

for National Geographic News

An 87-million-year-old praying mantis found encased in amber in Japan may be a "missing link" between mantises from the Cretaceous period and modern-day insects.

The fossil mantis measures 0.5 inch (1.4 centimeters) from its antennae to the tip of its abdomen.

Although the forelegs, head, and antennae appear to be well preserved, the wings and abdomen have been badly crushed.

Kazuhisa Sasaki, director of the Kuji Amber Museum, found the fossil creature in January buried 6.5 feet (2 meters) below the surface in an amber mine in Japan's northeastern Iwate Prefecture.

"This part of Japan is famous for producing large amounts of amber, but it was very fortunate for me to find this specimen," Sasaki said.

"I found it in a deposit that had lots of other insects—ancient flies, bees, and cockroaches—but this was the only praying mantis."

(See a photo of a bee trapped in amber that died carrying the oldest known orchid fossil.)

Spiny Legs

The mantis is the oldest ever found in Japan and one of only seven in the world from the Cretaceous period, according to Kyoichiro Ueda, executive curator of the Kitakyushu Museum of Natural History and Human History.

Previous mantis specimens have been found in New Jersey, northern Myanmar (Burma), Siberia, and Lebanon, he said.

But Sasaki's discovery appears to be different from any of those mantises.

"Modern mantises have a series of spines—maybe five or six—on their forelegs, to help them catch prey," Ueda said.

"The American Museum of Natural History has told us that no mantis from the Cretaceous period has ever been found with spines"—but the new specimen has two such spines protruding from its femur.

"That makes this fossil very unusual and interesting to science," Ueda said.

Another difference is that unlike previous finds, the newfound mantis has tiny hairs on its forelegs.

The block of amber is being polished to give researchers a better view of different parts of the fossil, which may reveal other differences between ancient and modern mantises, Ueda said.

"The years of the late Cretaceous period were a kind of transition phase between the ancient and modern worlds, and this fossil displays many intermediate elements between the two eras," he said.

"It is an excellent example of the transformation of morphological structures."

The mantis fossil will be on display at the Kuji museum through June, and Ueda hopes to be able to show the specimen at his museum in Kitakyushu starting this summer.

Giant Undersea Volcano Found Off Iceland

Richard A. Lovett
for National Geographic News

A giant and unusual underwater volcano lies just offshore of Iceland on the Reykjanes Ridge, volcanologists have announced. The Reykjanes formation is a section of the Mid-Atlantic Ridge, which bisects the Atlantic Ocean where the North American and Eurasian tectonic plates are pulling apart.

As magma wells up from the rift between the plates, it cools to form ridges.

But it doesn't generally form giant volcanoes, said Ármann Höskuldsson, a University of Iceland volcanologist who was part of the international team that discovered the volcano last summer.

That's because mid-ocean ridges are constantly pulling apart, making it harder for large volcanoes to form without being torn asunder.

"We were doing a normal oceangoing mission, and we found a big edifice" about 90 miles (150 kilometers) south of Iceland, Höskuldsson said.

The structure turned out to be an active volcano that rises about 3,300 feet (1,000 meters) above the surrounding sections of the ridge, coming within 1,300 feet (400 meters) of the surface.

At its base the volcano is approximately 30 miles (50 kilometers) across. The peak contains a depression known as a caldera that is 6 miles (10 kilometers) wide.

That indicates that the mountain is being fed by its own magma chamber, Höskuldsson said.

"It's a higher magma production that generates the edifice."

Seafloor Mapping

The underwater mountain resembles Krafla, an active aboveground volcano in northeastern Iceland that contains a similar-size caldera, according to Höskuldsson.

Krafla has erupted 29 times in recorded history, most recently in 1984. Nobody knows when the undersea volcano might next erupt, but Höskuldsson thinks it is only a matter of time.

Still, the people of Iceland are in no danger, he said, because the volcano is so deep under water.

"We wouldn't expect much to happen on the surface."

Mostly, the find indicates how little is known about the seafloor, Höskuldsson said.

"We are getting better techniques, but the oceans of the world are huge."

In the United States, for example, ocean scientists studying a swarm of earthquakes off the Oregon coast are having a hard time pinning down the temblors' source, because much of the seabed is poorly mapped.

"There are all kinds of things on the seafloor we don't know about," said Robert Embley, a National Oceanic and Atmospheric Administration scientist involved in the Oregon project.

Embley, who was not part of Höskuldsson's team, noted that satellite maps of Earth's gravitational field can be used to map out undersea structures.

But these maps don't provide the type of detail found by Höskuldsson. "Even though … you can see big features, you can't really tell what they are. All you can say is its a big feature," Embley said.

Höskuldsson will present his results this summer at the annual conference of the International Association of Volcanologists, to be held in Iceland.

Next year, he told the Icelandic press, his team plans to dive to the mountain with a small submarine to gather more clues as to why such a large volcano exists along the ridge.

Priest on party-balloons flight goes missing

SAO PAULO, Brazil (AP) -- A Roman Catholic priest who floated off under hundreds of helium party balloons was missing Monday off the southern coast of Brazil.

The Rev. Adelir Antonio de Carli lifts off Sunday under hundreds of helium party balloons.

Rescuers in helicopters and small fishing boats were searching off the coast of Santa Catarina state, where pieces of balloons were found.

The Rev. Adelir Antonio de Carli lifted off from the port city of Paranagua on Sunday afternoon, wearing a helmet, thermal suit and a parachute.

He was reported missing about eight hours later after losing contact with port authority officials, according to the treasurer of his Sao Cristovao parish, Denise Gallas.

Gallas said by telephone that the priest wanted to break a 19-hour record for the most hours flying with balloons to raise money for a spiritual rest-stop for truckers in Paranagua, Brazil's second-largest port for agricultural products. Watch priest lift off with hundreds of balloons »

Some American adventurers have used helium balloons to emulate Larry Walters -- who in 1982 rose three miles above Los Angeles in a lawn chair lifted by balloons.

A video of Carli posted on the G1 Web site of Globo TV showed the smiling 41-year-old priest slipping into a flight suit, being strapped to a seat attached to a huge column green, red, white and yellow balloons, and soaring into the air to the cheers of a crowd.

According to Gallas, the priest soared to an altitude of 20,000 feet (6,000 meters) then descended to about 8,200 feet (2,500 meters) for his planned flight to the city of Dourados, 465 miles (750 kilometers) northwest of his parish.

But winds pushed him in another direction, and Carli was some 30 miles (50 kilometers) off the coast when he last contacted Paranagua's port authority, Gallas said.

Carli had a GPS device, a satellite phone, a buoyant chair and is an experienced skydiver, Gallas said.

"We are absolutely confident he will be found alive and well, floating somewhere in the ocean," she said.

"He knew what he was doing and was fully prepared for any kind of mishap."

Could Welsh scientist end our universe?

by Robin Turner, Western Mail

COULD a Welshman be responsible for ending the world, then the entire universe?

As bizarre as it sounds, that is what a federal court in the US will have to decide in June.

Two American citizens say the £2bn giant particle accelerator which will begin smashing protons together at Cern (The European Centre for Nuclear Research) near Geneva this summer could end the world and everything outside it.

Former nuclear safety officer Walter Wagner and botanist Luis Sancho claim in a law suit filed in Hawaii the giant accelerator could spit out something called a Strangelet which could convert our planet to a lump of dense, shrunken “strange matter”.

Or, they claim, it could create a kind of black hole which would start sucking in matter, grow bigger and bigger and never stop.

But 63-year-old Dr Lyn Evans, from Aberdare, in charge of designing and building Cern’s expensive accelerator, known to the experts as a Large Hadron Collider (LHC), said yesterday the doomsday scenarios won’t happen.

He said the colliding protons at Cern will recreate energies and conditions last seen a trillionth of a second after the Big Bang.

His researchers will sift the debris from these primordial recreations for clues to unknown forces and symmetries of nature.

Swansea University physics graduate Dr Evans, a Welsh rugby fan and former Aberdare Grammar School pupil, said “micro black holes” could only be created with the energies of the colliding particles, which were equivalent to the energies of mosquitoes.

The Earth had been bombarded with invisible cosmic rays travelling at huge speeds for millions of years and particles within the cosmic rays were constantly colliding, he said.

“If the LHC can produce microscopic black holes, cosmic rays of much higher energies would already have produced many more.

“Since the Earth is still here, there is no reason to believe that collisions inside the LHC at Cern will be harmful.”

Dr Evans said Mr Wagner had previously filed a law suit objecting to another huge atom smasher, the Relativistic Heavy Ion Collider in Brooklyn, US, but the claim was dismissed.

The collider has been operating without incident since 2000.

However, the latest lawsuit touches on an issue which has bothered scholars and scientists for decades, namely how to estimate the risk of new groundbreaking experiments and who gets to decide whether or not to go ahead.

The suit, filed on March 21 in the Federal District Court, in Honolulu, seeks a temporary restraining order prohibiting Cern from proceeding with the accelerator until it can prove safety.

A spokesman for the Justice Department, which is representing the Department of Energy, said a scheduling meeting had been set for June 16.

But Cern, an organisation of European nations based in Switzerland, is only co-operating on a voluntary basis. Dr Evans said officials at Cern would explain its safety reasoning to Mr Wagner and Mr Sancho in the coming weeks.

Dr Evans, who has been based at Cern since shortly after graduating from Swansea University in 1969, will give the go-ahead for the 28-mile circumference LHC to begin experiments next month.

Its unique technology will make it 100 times more powerful than Cern’s existing accelerator, thanks to immense magnetic fields produced by superconducting magnets.

The LHC will generate data at a rate equal to the entire human population each making 10 telephone calls – simultaneously.

Dr Evans said of his 14-year work on the LHC: “I’ve been around a long time and seen big projects, but when I go into that tunnel I feel really overawed. Day to day I run a lab with 2,500 staff – which is huge.

“I also oversee the co-ordination between all the other organisations building components for the accelerator and engineers worldwide.

“My job involves quite a bit of travel.

“Recently, I met the President of China and thought to myself, ‘Not bad for a bloke from Aberdare!’”

Evolution: 24 myths and misconceptions

• NewScientist.com news service
• Michael Le Page

If you think you understand it, you don't know nearly enough about it

It will soon be 200 years since the birth of Charles Darwin and 150 years since the publication of On the Origin of Species, arguably the most important book ever written. In it, Darwin outlined an idea that many still find shocking – that all life on Earth, including human life, evolved through natural selection.

Darwin presented compelling evidence for evolution in On the Origin and, since his time, the case has become overwhelming. Countless fossil discoveries allow us to trace the evolution of today's organisms from earlier forms. DNA sequencing has confirmed beyond any doubt that all living creatures share a common origin. Innumerable examples of evolution in action can be seen all around us, from the pollution-matching pepper moth to fast-changing viruses such as HIV and H5N1 bird flu. Evolution is as firmly established a scientific fact as the roundness of the Earth.

And yet despite an ever-growing mountain of evidence, most people around the world are not taught the truth about evolution, if they are taught about it at all. Even in the UK, the birthplace of Darwin with an educated and increasingly secular population, one recent poll suggests less than half the population accepts evolution.

For those who have never had the opportunity to find out about biology or science, claims made by those who believe in supernatural alternatives to evolutionary theory can appear convincing. Meanwhile, even among those who accept evolution, misconceptions abound.

Most of us are happy to admit that we do not understand, say, the string theory in physics, yet we are all convinced we understand evolution. In fact, as biologists are discovering, its consequences can be stranger than we ever imagined. Evolution must be the best-known yet worst-understood of all scientific theories.

So here is New Scientist's guide to some of the most common myths and misconceptions about evolution.

There are already several good and comprehensive guides out there. But there can't be too many.

Shared misconceptions:

Everything is an adaptation produced by natural selection

Natural selection is the only means of evolution

Natural selection leads to ever-greater complexity

Evolution produces creatures perfectly adapted to their environment

Evolution always promotes the survival of species

It doesn't matter if people do not understand evolution

"Survival of the fittest" justifies "everyone for themselves"

Evolution is limitlessly creative

Evolution cannot explain traits such as homosexuality

Creationism provides a coherent alternative to evolution

Creationist myths:

Evolution must be wrong because the Bible is inerrant

Accepting evolution undermines morality

Evolutionary theory leads to racism and genocide

Religion and evolution are incompatible

Half a wing is no use to anyone

Evolutionary science is not predictive

Evolution cannot be disproved so is not science

Evolution is just so unlikely to produce complex life forms

Evolution is an entirely random process

Mutations can only destroy information, not create it

Darwin is the ultimate authority on evolution

The bacterial flagellum is irreducibly complex

Yet more creationist misconceptions

Evolution violates the second law of thermodynamics

Masturbation 'cuts cancer risk'

From the BBC News.

Men could reduce their risk of developing prostate cancer through regular masturbation, researchers suggest.

They say cancer-causing chemicals could build up in the prostate if men do not ejaculate regularly.

And they say sexual intercourse may not have the same protective effect because of the possibility of contracting a sexually transmitted infection, which could increase men's cancer risk.

Australian researchers questioned over 1,000 men who had developed prostate cancer and 1,250 who had not about their sexual habits.

This is a plausible theory Dr Chris Hiley, Prostate Cancer Charity

They found those who had ejaculated the most between the ages of 20 and 50 were the least likely to develop the cancer.

The protective effect was greatest while the men were in their 20s.

Men who ejaculated more than five times a week were a third less likely to develop prostate cancer later in life.

Fluid

Previous research has suggested that a high number of sexual partners or a high level of sexual activity increased a man's risk of developing prostate cancer by up to 40%.

But the Australian researchers who carried out this study suggest the early work missed the protective effect of ejaculation because it focussed on sexual intercourse, with its associated risk of STIs.

Graham Giles, of the Cancer Council Victoria in Melbourne, who led the research team, told New Scientist: "Had we been able to remove ejaculations associated with sexual intercourse, there should have been an even stronger protective effect of ejaculations."

The researchers suggest that ejaculating may prevent carcinogens accumulating in the prostate gland.

The prostate provides a fluid into semen during ejaculation that activates sperm and prevents them sticking together.

The fluid has high concentrations of substances including potassium, zinc, fructose and citric acid, which are drawn from the bloodstream.

But animal studies have shown carcinogens such as 3-methylchloranthrene, found in cigarette smoke, are also concentrated in the prostate.

'Flushing out'

Dr Giles said fewer ejaculations may mean the carcinogens build up.

"It's a prostatic stagnation hypothesis. The more you flush the ducts out, the less there is to hang around and damage the cells that line them."

A similar connection has been found between breast cancer and breastfeeding, where lactating appeared to "flush out" carcinogens, reduce a woman's risk of the disease, New Scientist reports.

Another theory put forward by the researchers is that ejaculation may induce prostate glands to mature fully, making them less susceptible to carcinogens.

Dr Chris Hiley, head of policy and research at the UK's Prostate Cancer Charity, told BBC News Online: "This is a plausible theory."

She added: "In the same way the human papillomavirus has been linked to cervical cancer, there is a suggestion that bits of prostate cancer may be related to a sexually transmitted infection earlier in life."

Anthony Smith, deputy director of the Australian Research Centre in Sex, Health and Society at La Trobe University in Melbourne, said the research could affect the kind of lifestyle advice doctors give to patients.

"Masturbation is part of people's sexual repertoire.

"If these findings hold up, then it's perfectly reasonable that men should be encouraged to masturbate," he said.

Clues to ancestral origin of placenta emerge in Stanford study

By AMY ADAMS

STANFORD, Calif. — Researchers at the Stanford University School of Medicine have uncovered the first clues about the ancient origins of a mother’s intricate lifeline to her unborn baby, the placenta, which delivers oxygen and nutrients critical to the baby’s health.

The evidence suggests the placenta of humans and other mammals evolved from the much simpler tissue that attached to the inside of eggshells and enabled the embryos of our distant ancestors, the birds and reptiles, to get oxygen.

“The placenta is this amazing, complex structure and it’s unique to mammals, but we’ve had no idea what its evolutionary origins are,” said Julie Baker, PhD, assistant professor of genetics. Baker is senior author of the study, published in the May issue of Genome Research.

The placenta grows inside the mother’s uterus and serves as a way of exchanging gas and nutrients between mother and fetus; it is expelled from the mother’s body after the birth of a baby. It is the only organ to develop in adulthood and is the only one with a defined end date, Baker said, making the placenta of interest to people curious about how tissues and organs develop.

Beyond being a biological curiosity, the placenta also plays a role in the health of both the mother and the baby. Some recent research also suggests that the placenta could be a key barrier in preventing or allowing molecules to pass to the unborn baby that influence the baby’s disease risk well into adulthood.

“The placenta seems to be critical for fetal health and maternal heath,” Baker said. Despite its major impact, almost nothing was known about how the placenta evolved or how it functions.
Baker and Kirstin Knox, graduate student and the study’s first author, began addressing the question of the placenta’s evolution by determining which genes are active in cells of the placenta throughout pregnancy in mice.

They found that the placenta develops in two distinct stages. In the first stage, which runs from the beginning of pregnancy through mid-gestation, the placental cells primarily activate genes that mammals have in common with birds and reptiles. This suggests that the placenta initially evolved through repurposing genes the early mammals inherited from their immediate ancestors when they arose more than 120 million years ago.

In the second stage, cells of the mammalian placenta switch to a new wave of species-specific genes. Mice activate newly evolved mouse genes and humans activate human genes.

It makes sense that each animal would need a different set of genes, Baker said. “A pregnant orca has different needs than a mouse and so they had to come up with different hormonal solutions to solve their problems,” she said. For example, an elephant’s placenta nourishes a single animal for 660 days. A pregnant mouse gestates an average of 12 offspring for 20 days. Clearly, those two pregnancies would require very different placentas.

Baker said these findings are particularly interesting given that cloned mice are at high risk of dying soon after the placenta’s genetic transition takes place. “There’s obviously a huge regulatory change that takes place,” she said. What’s surprising is that despite the dramatic shift taking place in the placenta, the tissue doesn’t change in appearance.

Understanding the placenta’s origins and function could prove useful. Previous studies suggest the placenta may contribute to triggering the onset of maternal labor, and is suspected to be involved in a maternal condition called pre-eclampsia, which is a leading cause of premature births.

Baker intends to follow up on this work by collaborating with Theo Palmer, PhD, associate professor of neurosurgery; Gill Bejerano, PhD, assistant professor of developmental biology, and Anna Penn, MD, PhD, assistant professor of pediatrics. Together, the group hopes to learn how the placenta protects the growing brain of the unborn baby, a protection that seems to extend into adulthood.

The work was funded by the National Institutes of Health, the March of Dimes and Stanford’s Medical Scientist Training Program.

What Came Before the Big Bang Might Have Been Eerily Similar

By Joshua Hill Monday, April 14, 2008

The Big Bang has long been the realm of religious contention. However of late, there has been a rising group of Christian’s (amongst others) who have allowed for the possibility that God used the Big Bang as his creation tool.

However, with that being said, there is still another contention about what came before.

Science has long failed to provide anything stable that could suggest what came before the Big Bang. General Relativity curls up in to the fetal position and demands to be left alone whenever anyone brings the idea of “what came before” to it.

However, physicists Alejandro Corichi from Universidad Nacional Autónoma de México and Parampreet Singh from the Perimeter Institute for Theoretical Physics in Ontario, may have created an answer.

In fact, they haven’t created anything, but only built upon previous work. A new theory called Loop Quantum Gravity (LQG) has cropped up in recent years, and while there is a lot of math and science to this theory, one of its assumptions is that instead of a Big Bang spacetime singularity, there was a Big Bounce.

“The significance of this concept is that it answers what happened to the universe before the Big Bang,” Singh told PhysOrg.com. “It has remained a mystery, for models that could resolve the Big Bang singularity, whether it is a quantum foam or a classical space-time on the other side. For instance, if it were a quantum foam, we could not speak about a space-time, a notion of time, etc. Our study shows that the universe on the other side is very classical as ours.”

Previous work on the LQG showed that there had been a universe on the other side, but while it showed valid math, there was no chance to observe in our current universe the state of the pre-bounce universe. This is because, under the previous theory – worked upon by Penn State physicist Martin Bojowald – there was nothing preserved across the bounce. Bojowald described this as a sort of “cosmic amnesia.”

However Corichi and Singh have modified the LQG by approximating a key equation called the quantum constraint. Their version is called the sLQG, and it shows that the relative fluctuations of volume and momentum in the pre-bounce universe are conserved across the bounce.

“This means that the twin universe will have the same laws of physics and, in particular, the same notion of time as in ours,” Singh said. “The laws of physics will not change because the evolution is always unitary, which is the nicest way a quantum system can evolve. In our analogy, it will look identical to its twin when seen from afar; one could not distinguish them.”

“In the universe before the bounce, all the general features will be the same,” said Singh. “It will follow the same dynamical equations, the Einstein’s equations when the universe is large. Our model predicts that this happens when the universe becomes of the order 100 times larger than the Planck size. Further, the matter content will be the same, and it will have the same evolution. Since the pre-bounce universe is contracting, it will look as if we were looking at ours backward in time.”

But the researchers are quick to point out that this second universe is not full of duplicates of us. It does not suggest that every particle on the other side is exactly the same, and that there is someone who has lived your life. It is pretty much as if the “evil Spock” from the old Star Trek episodes had been from the previous world, not a parallel dimension.

A non-Star Trek description would be; “If one were able to look at certain microscopic properties with a very strong microscope – a very high-energy experiment probing the Planck scale – one might see differences in some quantities, just as one might see that twins have different fingerprints or one has a mole and the other does not, or a different DNA,” Singh said.

In the end, Corichi and Singh’s model may even be able to show us what our own future universe will look like. Depending on how fast our own universe is accelerating, there’s a possibility that – through generalizing their model – a re-collapse of our own universe is possible.

Antartica without the ice

Quasars Quash Star Formation In Active Galactic Nuclei

ScienceDaily (Apr. 4, 2008) — An ambitious study of active and inactive galaxies has given new insights into the complex interaction between super-massive black holes at the heart of Active Galactic Nuclei (AGN) and star formation in the surrounding galaxy. Results will be presented in a talk by Paul Westoby on 4th April at the RAS National Astronomy Meeting in Belfast.

Along with colleagues, Carole Mundell and Ivan Baldry from the Astrophysics Research Institute of Liverpool John Moores University, Westoby studied the properties of light from 360,000 galaxies in the local Universe to understand the relationship between accreting black holes, the birth of stars in galaxy centres and the evolution of the galaxies as a whole.

The study finds that gas ejected during the quasar stage of AGN snuffs out star formation, leaving the host galaxies to evolve passively. The study also reveals a strong link between galaxy mergers and the formation of super-massive black holes in AGN, but shows that if the environment becomes too crowded with galaxies, then the likelihood of firing up a supermassive black hole becomes suppressed.

Scientists believe that all AGN go through a quasar phase, where the radiation emitted from the growing accretion disc around the central black hole becomes so bright that it outshines its entire host galaxy. Today, most massive galaxies are thought to contain a dormant super-massive black hole at their heart, a legacy of this earlier phase of powerful quasar activity, but for reasons unknown, some of these local black holes have been reignited.

The Liverpool team concentrated on these local AGN, which can be studied in more detail than their more distant quasar cousins, and, by comparing the properties of a large number of galaxies, the team addressed a key question – do galaxies that host AGN represent an adolescent or transition phase of galaxy evolution?

“The starlight from the host galaxy can tell us much about how the galaxy has evolved,” said Westoby. “Galaxies can be grouped into two simple colour families: the blue sequence, which are young, hotbeds of star-formation and the red sequence, which are massive, cool and passively evolving.” Westoby continued “Scientists have thought for some time that AGN host galaxies might be a stepping stone between the two families and therefore represent a critical point in the lifetime of a galaxy, but our study has been able to rule this out.”

Instead the AGNs identified by the team lay in galaxies that showed a clear overlap with red sequence galaxies. This suggests that the star-forming days for AGN host galaxies have a distinct cut-off point and that the post-quasar local AGNs are no longer generating new stars. This conclusion is reinforced by the team’s findings that the majority of local AGNs are linked with “classical bulges”, round balls of stars formed during violent mergers of gas-rich galaxies early on in the Universe’s history, rather than “pseudo bulges”, disc-only galaxies that have not undergone a major merger since their formation. This implies that the formation of the super-massive black hole that drives the AGN is linked to the evolution of the bulge, rather than the galaxy as a whole.

Finally, the team identified an intriguing population of galaxies that have an active population of young stars together with an actively accreting black hole, so-called composite galaxies. These masquerade as a transition population, and lie in the region predicted for galaxies experiencing AGN feedback – the process by which material ejected by the AGN has a direct impact on the evolution of the surrounding galaxy. However, Westoby and colleagues find feedback an unlikely explanation for the observed properties of these galaxies and suggest that feedback may only be important during the quasar phase and not in weaker, nearby AGN.

Adapted from materials provided by Royal Astronomical Society.