ALMA Explores the Hubble Ultra Deep Field: Deepest Ever Millimeter Observations Of Early Universe

International teams of astronomers have used the Atacama Large Millimeter/submillimeter Array (ALMA) to explore the distant corner of the Universe first revealed in the iconic images of the Hubble Ultra Deep Field (HUDF). These new ALMA observations are significantly deeper and sharper than previous surveys at millimetre wavelengths. They clearly show how the rate of star formation in young galaxies is closely related to their total mass in stars. They also trace the previously unknown abundance of star-forming gas at different points in time, providing new insights into the “Golden Age” of galaxy formation approximately 10 billion years ago.

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The new ALMA results will be published in a series of papers appearing in the Astrophysical Journal and Monthly Notices of the Royal Astronomical Society. These results are also among those being presented this week at the Half a Decade of ALMA conference in Palm Springs, California, USA.

In 2004 the Hubble Ultra Deep Field images, pioneering deep-field observations with the NASA/ESA Hubble Space Telescope, were published. These spectacular pictures probed more deeply than ever before and revealed a menagerie of galaxies stretching back to less than a billion years after the Big Bang. The area was observed several times by Hubble and many other telescopes, resulting in the deepest view of the Universe to date.

Astronomers using ALMA have now surveyed this seemingly unremarkable, but heavily studied, window into the distant Universe for the first time both deeply and sharply in the millimetre range of wavelengths. This allows them to see the faint glow from gas clouds and also the emission from warm dust in galaxies in the early Universe.

ALMA has observed the HUDF for a total of around 50 hours up to now. This is the largest amount of ALMA observing time spent on one area of the sky so far.

One team led by Jim Dunlop (University of Edinburgh, United Kingdom) used ALMA to obtain the first deep, homogeneous ALMA image of a region as large as the HUDF. This data allowed them to clearly match up the galaxies that they detected with objects already seen with Hubble and other facilities.

This study showed clearly for the first time that the stellar mass of a galaxy is the best predictor of star formation rate in the high redshift Universe. They detected essentially all of the high-mass galaxies and virtually nothing else.

Jim Dunlop, lead author on the deep imaging paper sums up its importance: “This is a breakthrough result. For the first time we are properly connecting the visible and ultraviolet light view of the distant Universe from Hubble and far-infrared/millimetre views of the Universe from ALMA.”

The second team, led by Manuel Aravena of the Núcleo de Astronomía, Universidad Diego Portales, Santiago, Chile, and Fabian Walter of the Max Planck Institute for Astronomy in Heidelberg, Germany, conducted a deeper search across about one sixth of the total HUDF.

“We conducted the first fully blind, three-dimensional search for cool gas in the early Universe,” said Chris Carilli, an astronomer with the National Radio Astronomy Observatory (NRAO) in Socorro, New Mexico, USA and member of the research team. “Through this, we discovered a population of galaxies that is not clearly evident in any other deep surveys of the sky.” [4]

Some of the new ALMA observations were specifically tailored to detect galaxies that are rich in carbon monoxide, indicating regions primed for star formation. Even though these molecular gas reservoirs give rise to the star formation activity in galaxies, they are often very hard to see with Hubble. ALMA can therefore reveal the “missing half” of the galaxy formation and evolution process.

“The new ALMA results imply a rapidly rising gas content in galaxies as we look back further in time,” adds lead author of two of the papers, Manuel Aravena (Núcleo de Astronomía, Universidad Diego Portales, Santiago, Chile). “This increasing gas content is likely the root cause for the remarkable increase in star formation rates during the peak epoch of galaxy formation, some 10 billion years ago.”

The results presented today are just the start of a series of future observations to probe the distant Universe with ALMA. For example, a planned 150-hour observing campaign of the HUDF will further illuminate the star-forming potential history of the Universe.

“By supplementing our understanding of this missing star-forming material, the forthcoming ALMA Large Program will complete our view of the galaxies in the iconic Hubble Ultra Deep Field,” concludes Fabian Walter.

Astronomers specifically selected the area of study in the HUDF, a region of space in the faint southern constellation of Fornax (The Furnace), so ground-based telescopes in the southern hemisphere, like ALMA, could probe the region, expanding our knowledge about the very distant Universe. Probing the deep, but optically invisible, Universe was one of the primary science goals for ALMA.

In this context “high mass” means galaxies with stellarmasses greater than 20 billion times that of the Sun ( 2 × 10^10 solar masses). For comparison, the Milky Way is a large galaxy and has a mass of around 100 billion solar masses.

This region of sky is about seven hundred times smaller than the area of the disc of the full Moon as seen from Earth. One of the most startling aspects of the HUDF was the vast number of galaxies found in such a tiny fraction of the sky.

ALMA’s ability to see a completely different portion of the electromagnetic spectrum from Hubble allows astronomers to study a different class of astronomical objects, such as massive star-forming clouds, as well as objects that are otherwise too faint to observe in visible light, but visible at millimetre wavelengths.

The search is referred to as “blind” as it was not focussed on any particular object.

Cosmology Safe As Universe Has No Sense Of Direction

The universe is expanding uniformly according to research led by UCL which reports that space isn’t stretching in a preferred direction or spinning.

The new study, published today in Physical Review Letters, studied the cosmic microwave background (CMB) which is the remnant radiation from the Big Bang. It shows the universe expands the same way in all directions, supporting the assumptions made in cosmologists’ standard model of the universe.

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First author, Daniela Saadeh (UCL Physics & Astronomy), said: “The finding is the best evidence yet that the universe is the same in all directions. Our current understanding of the universe is built on the assumption that it doesn’t prefer one direction over another, but there are actually a huge number of ways that Einstein’s theory of relativity would allow for space to be imbalanced. Universes that spin and stretch are entirely possible, so it’s important that we’ve shown ours is fair to all its directions.”

The team from UCL and Imperial College London used measurements of the CMB taken between 2009 and 2013 by the European Space Agency’s Planck satellite. The spacecraft recently released information about the polarisation of CMB across the whole sky for the first time, providing a complementary view of the early universe that the team was able to exploit.

The researchers modelled a comprehensive variety of spinning and stretching scenarios and how these might manifest in the CMB, including its polarisation. They then compared their findings with the real map of the cosmos from Planck, searching for specific signs in the data.

Daniela Saadeh, explained: “We calculated the different patterns that would be seen in the cosmic microwave background if space has different properties in different directions. Signs might include hot and cold spots from stretching along a particular axis, or even spiral distortions.”

Collaborating author Dr Stephen Feeney (Imperial College London) added: “We then compare these predictions to reality. This is a serious challenge, as we found an enormous number of ways the Universe can be anisotropic. It’s extremely easy to become lost in this myriad of possible universes — we need to tune 32 dials to find the correct one.”

Previous studies only looked at how the universe might rotate, whereas this study is the first to test the widest possible range of geometries of space. Additionally, using the wealth of new data collected from Planck allowed the team to achieve vastly tighter bounds than the previous study. “You can never rule it out completely, but we now calculate the odds that the universe prefers one direction over another at just one in 121,000,” said Daniela Saadeh.

Most current cosmological studies assume that the Universe behaves identically in every direction. If this assumption were to fail, a large number of analyses of the cosmos and its content would be flawed.

Daniela Saadeh, added: “We’re very glad that our work vindicates what most cosmologists assume. For now, cosmology is safe.”

The work was kindly supported by the Perren Fund, IMPACT fund, Royal Astronomical Society, Science and Technology Facilities Council, Royal Society, European Research Council, and Engineering and Physical Sciences Research Council.

Stalled Front And Tropical Storm Deluge Roads, Close Schools

NORFOLK, Va. – Flooding in coastal Virginia and North Carolina blocked roads and forced school closings Wednesday that affected for more than 100,000 students.

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A stalled weather system and the remnants of Tropical Storm Julia have brought days of rain and localized flooding to the region. The rain is expected to continue into Thursday.

National Weather Service Meteorologist Tim Gingrich said anywhere from 5 inches to 12 inches of rain have fallen “and it’s still raining.” He added that the rainfall has broken records for individual dates on Monday and Tuesday.

“We still have a flash flood watch for at least Norfolk, Chesapeake and Virginia Beach,” Gingrich added.

Gingrich said the worst should be over by Wednesday evening. But he said rain will still fall for much of Thursday before Julia’s remnants are expected to drift out to sea by the following day.

“Right now it’s sitting over a corner of northeast North Carolina and spinning,” he said of the storm.

Major school districts in Virginia’s south Hampton Roads region have canceled classes. So have two North Carolina counties, Currituck and Gates. Local media are reporting impassable roadways and highway ramps throughout the region.

Officials in Chowan County, North Carolina, reported on a website that at least two roads were washed out along with water lines serving 150 customers. Several others roads are impassable. Between five to 10 inches of rain has fallen there. The county remained under a flood warning until the late afternoon.

In Virginia Beach, resident Todd Solomon said he’s never seen rainstorms close schools without a hurricane bearing down.

Solomon lives in a flood-prone neighborhood. He said water flooded his backyard up to his house’s foundation but failed to enter the home. He said his neighborhood has fared pretty well, considering.

“A lot of parents were pretty surprised,” said Solomon who has a child in middle school. “The kids are pretty happy. They were texting, saying hey what are we going to do today? It was like summer or the weekend.”

Galactic Fireworks Illuminate Monster Hydrogen Blob In Space

An international team of researchers using the Atacama Large Millimeter/submillimeter Array (ALMA) and other telescopes has discovered the power source illuminating a so-called Lyman-alpha Blob — a rare, brightly glowing, and enormous concentration of gas in the distant universe.

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Until now, astronomers wondered why these huge clouds of gas shined so brightly. The answer, in this example at least, appears to be two galaxies at the heart of the blob undergoing furious star formation and lighting up their surroundings. These large galaxies, which are destined to eventually merge into a single elliptical galaxy, are in the midst of a swarm of smaller galaxies. This appears to be an early phase in the formation of a massive cluster of galaxies.

Lyman-alpha Blobs (LABs) are gigantic clouds of hydrogen gas that can span hundreds of thousands of light-years and are found at very large cosmic distances. The name reflects the characteristic wavelength of ultraviolet light that they emit, known as Lyman-alpha radiation. Since their discovery, the processes that give rise to LABs have been an astronomical puzzle. New observations with ALMA have now cleared up the mystery.

One of the largest Lyman-alpha Blobs known, and the most thoroughly studied, is SSA22-Lyman-alpha blob 1, or LAB-1. Embedded in the core of a huge cluster of galaxies in the early stages of formation, it was the very first such object to be discovered — in 2000 — and is located so far away that its light has taken about 11.5 billion years to reach us.

A team of astronomers, led by Jim Geach, from the Center for Astrophysics Research of the University of Hertfordshire, UK, has now used ALMA’s unparalleled ability to observe light from cool dust clouds in distant galaxies to peer deeply into LAB-1. This allowed them to pinpoint and resolve several sources of submillimeter emission.

The astronomers then combined the ALMA images with observations from the Multi Unit Spectroscopic Explorer (MUSE) instrument mounted on ESO’s Very Large Telescope (VLT), which map the Lyman-alpha light. This showed that the ALMA sources are located in the very heart of the Lyman-alpha Blob, where they are forming stars at a rate over 100 times that of the Milky Way.

Deep imaging with the NASA/ESA Hubble Space Telescope and spectroscopy at the W. M. Keck Observatory also revealed that the ALMA sources are surrounded by numerous faint companion galaxies that could be bombarding the central ALMA sources with material, helping to drive their high star formation rates.

The team then turned to a sophisticated simulation of galaxy formation, known as the Feedback in Realistic Environments (FIRE), to demonstrate that the giant glowing cloud of Lyman-alpha emission can be explained if ultraviolet light produced by star formation in the ALMA sources scatters off the surrounding hydrogen gas. This would give rise to the Lyman-alpha Blob we see.

Jim Geach, lead author of the new study accepted for publication in the Astrophysical Journal, explains: “Think of a streetlight on a foggy night — you see the diffuse glow because light is scattering off the tiny water droplets. A similar thing is happening here, except the streetlight is an intensely star-forming galaxy and the fog is a huge cloud of intergalactic gas. The galaxies are illuminating their surroundings.”

Understanding how galaxies form and evolve is a massive challenge. Astronomers think Lyman-alpha Blobs are important because they seem to be the places where the most massive galaxies in the universe form. In particular, the extended Lyman-alpha glow provides information on what is happening in the primordial gas clouds surrounding young galaxies, a region that is very difficult to study, but critical to understand.

“Unveiling the galaxies shrouded in LAB-1 did more than just put to bed the longstanding issue of the gas cloud’s glow,” said Desika Narayanan of Haverford College in Pennsylvania and coauthor of the paper. “It provided a rare opportunity to see how young, growing galaxies behaved when the universe was quite young.”

Jim Geach concludes, “What’s exciting about these blobs is that we are getting a rare glimpse of what’s happening around these young, growing galaxies. For a long time, the origin of the extended Lyman-alpha light has been controversial. But with the combination of new observations and cutting-edge simulations, we think we have solved a 15-year-old mystery: Lyman-alpha Blob-1 is the site of formation of a massive elliptical galaxy that will one day be the heart of a giant cluster. We are seeing a snapshot of the assembly of that galaxy 11.5 billion years ago.”

Twin Jets Pinpoint The Heart Of An Active Galaxy

Two particle jets shoot out from the heart of active galaxy NGC 1052 at the speed of light, apparently originating in the vicinity of a massive black hole. A team of researchers headed by Anne-Kathrin Baczko from the Max Planck Institute for Radio Astronomy Bonn have now measured the magnetic fields in this area. They observed the bright, very compact structure of just two light days in size using a global ensemble of millimetre-wavelength telescopes. The magnetic field value recorded at the event horizon of the black hole was between 0.02 and 8.3 tesla. The team concludes that the magnetic fields provide enough magnetic energy to power the twin jets.

jets

The technique used to investigate details at the centre of galaxy NGC 1052 is known as very-long-baseline interferometry (VLBI), and has the potential to locate the bases of jets at tiny length scales. In fact, these latest observations extend right up close to the event horizon of the central power source — a supermassive black hole. The event horizon marks the boundary between free space and the gravitational pull of the black hole, beyond which no radiation can escape.

The black hole itself remains invisible, however, so its exact position can only be inferred indirectly by tracking the jet positions depending on their wavelengths. The unknown offset distance of the jet base from the black hole makes it difficult to determine fundamental physical properties such as magnetic field values and particle density.

However, the striking symmetry in these latest observations of the twin jets in NGC 1052 allows astronomers to pinpoint the true centre of activity inside the central structure. Only one jet is observed in most other galaxies, but the symmetrical jets of NGC 1052 allow great precision in determining the “centre” and thus also the location of the power source.

With the exception of our own Milky Way, this is the most precisely known location of a supermassive black hole in the universe. “NGC 1052 is truly a key source, since it pinpoints directly and unambiguously the position of a black hole,” says Anne-Kathrin Baczko, who carried out this research at the Universities of Erlangen-Nuremberg and Wurzburg, and at the Max Planck Institute for Radio Astronomy.

NGC 1052 is an elliptical galaxy at a distance of about 60 million light years in the direction of the constellation Cetus (the Whale). The magnetic field at the supermassive black hole was determined by measuring the compactness and brightness of the central region of NGC 1052, yielding values between 0.02 and 8.3 tesla. (By way of comparison, Earth’s magnetic field is only about 50 microtesla.) The central region appears as a strong radio source with a diameter of just 57 microarcseconds: equivalent in size to a DVD on the surface of the moon.

This astonishing resolution was obtained by the Global mm VLBI Array, a network of radio telescopes in Europe, the USA and East Asia, managed by the Max Planck Institute for Radio Astronomy in Bonn. “It yields unprecedented image sharpness and is soon to be applied to reach event-horizon scales in nearby objects,” says Eduardo Ros, a Max Planck researcher who collaborated in the project.

How are powerful relativistic jets formed in the centres of numerous active galaxies? The telescope array observations may help solve this long-standing mystery, as they show that it is possible for jets to be driven by the magnetic energy released by a very rapidly rotating supermassive black hole.

Turrialba Volcano (Costa Rica): Intense Activity And Ash Emissions

After a day of relative calm, a new pulse of ash emissions occurred from the volcano this morning.

volcano

The current phase of activity at the volcano began around 13 Sep with renewed, but sporadic and weak ash emissions, but intensified drastically on 19 Sep reaching a new peak of activity (so far).

Between 02:53 and 15:30 local time, the volcano produced several phases of near-continuous explosive activity with strong ash emissions, generating several ash plumes that rose more than 1000 m, drifted west into the Central Valley, causing moderate to heavy ash falls and forcing a temporary closure of the capital’s Juan Santamaria International Airport.

Some of the explosions were strong enough that part of the dense eruption columns collapsed into small pyroclastic flows that spread onto the crater floor. There are no reports of damage or injuries.

Black Hole Hidden Within Its Own Exhaust

Supermassive black holes, millions to billions of times the mass of our Sun, are found at the centers of galaxies. Many of these galactic behemoths are hidden within a thick doughnut-shape ring of dust and gas known as a torus. Previous observations suggest these cloaking, tire-like structures are formed from the native material found near the center of a galaxy.

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New data from the Atacama Large Millimeter/submillimeter Array (ALMA), however, reveal that the black hole at the center of a galaxy named NGC 1068 is actually the source of its own dusty torus of dust and gas, forged from material flung out of the black hole’s accretion disk.

This newly discovered cosmic fountain of cold gas and dust could reshape our understanding of how black holes impact their host galaxy and potentially the intergalactic medium.

“Think of a black hole as an engine. It’s fueled by material falling in on it from a flattened disk of dust and gas,” said Jack Gallimore, an astronomer at Bucknell University in Lewisburg, Pennsylvania, and lead author on a paper published in Astrophysical Journal Letters. “But like any engine, a black hole can also emit exhaust.” That exhaust, astronomers discovered, is the likely source of the torus of material that effectively obscures the region around the galaxy’s supermassive black hole from optical telescopes.

NGC 1068 (also known as Messier 77) is a barred spiral galaxy approximately 47 million light-years from Earth in the direction of the constellation Cetus. At its center is an active galactic nucleus, a supermassive black hole that is being fed by a thin, rotating disk of gas and dust known as an accretion disk. As material in the disk spirals toward the central black hole, it becomes superheated and blazes bright with ultraviolet radiation. The outer reaches of the disk, however, are considerably cooler and glow more appreciably in infrared light and the millimeter-wavelength light that ALMA can detect.

Using ALMA, an international team of astronomers peered deep into this region and discovered a sprinkling of cool clouds of carbon monoxide lifting off the outer portion of the accretion disk. The energy from the hot inner disk partially ionizes these clouds, enabling them to adhere to powerful magnetic field lines that wrap around the disk.

Like water being flung out of a rapidly rotating garden sprinkler, the clouds rising above the accretion disk get accelerated centrifugally along the magnetic field lines to very high speeds — approximately 400 to 800 kilometers per second (nearly 2 million miles per hour). This is up to nearly three times faster than the rotational speed of the outer accretion disk, fast enough to send the clouds hurtling further out into the galaxy.

“These clouds are traveling so fast that they reach ‘escape velocity’ and are jettisoned in a cone-like spray from both sides of the disk,” said Gallimore. “With ALMA, we can for the first time see that it is the gas that is thrown out that hides the black hole, not the gas falling in.” This suggests that the general theory of an active black hole is oversimplified, he concludes.

With future ALMA observations, the astronomers hope to work out a fuel budget for this black hole engine: how much mass per year goes into the black hole and how much is ejected as exhaust.

“These are fundamental quantities for understanding black holes that we really don’t have a good handle on at this time,” concludes Gallimore.

The National Radio Astronomy Observatory is a facility of the National Science Foundation, operated under cooperative agreement by Associated Universities, Inc.