̽��ֱ�� of Cambridge - Atacama Large Millimeter-submillimeter Array (ALMA)

Astronomers detect ‘whirlpool’ movement in earliest galaxies

sc604 — Wed, 10 Jan 2018 18:00:00 +0000

An international team led by Dr Renske Smit from the Kavli Institute of Cosmology at the ̽��ֱ�� of Cambridge used the Atacama Large Millimeter/submillimeter Array (ALMA) in Chile to open a new window onto the distant Universe, and have for the first time been able to identify normal star-forming galaxies at a very early stage in cosmic history with this telescope. ̽��ֱ��results are reported in the journal Nature, and will be presented at the 231^st meeting of the American Astronomical Society.

Light from distant objects takes time to reach Earth, so observing objects that are billions of light years away enables us to look back in time and directly observe the formation of the earliest galaxies. ̽��ֱ��Universe at that time, however, was filled with an obscuring ‘haze’ of neutral hydrogen gas, which makes it difficult to see the formation of the very first galaxies with optical telescopes.

Smit and her colleagues used ALMA to observe two small newborn galaxies, as they existed just 800 million years after the Big Bang. By analysing the spectral ‘fingerprint’ of the far-infrared light collected by ALMA, they were able to establish the distance to the galaxies and, for the first time, see the internal motion of the gas that fuelled their growth.

“Until ALMA, we’ve never been able to see the formation of galaxies in such detail, and we’ve never been able to measure the movement of gas in galaxies so early in the Universe’s history,” said co-author Dr Stefano Carniani, from Cambridge’s Cavendish Laboratory and Kavli Institute of Cosmology.

̽��ֱ��researchers found that the gas in these newborn galaxies swirled and rotated in a whirlpool motion, similar to our own galaxy and other, more mature galaxies much later in the Universe’s history. Despite their relatively small size – about five times smaller than the Milky Way – these galaxies were forming stars at a higher rate than other young galaxies, but the researchers were surprised to discover that the galaxies were not as chaotic as expected.

“In the early Universe, gravity caused gas to flow rapidly into the galaxies, stirring them up and forming lots of new stars – violent supernova explosions from these stars also made the gas turbulent,” said Smit, who is a Rubicon Fellow at Cambridge, sponsored by the Netherlands Organisation for Scientific Research. “We expected that young galaxies would be dynamically ‘messy’, due to the havoc caused by exploding young stars, but these mini-galaxies show the ability to retain order and appear well regulated. Despite their small size, they are already rapidly growing to become one of the ‘adult’ galaxies like we live in today.”

̽��ֱ��data from this project on small galaxies paves the way for larger studies of galaxies during the first billion years of cosmic time. ̽��ֱ��research was funded in part by the European Research Council and the UK Science and Technology Facilities Council (STFC).

Reference:
Renske Smit et al. ‘Rotation in [C II]-emitting gas in two galaxies at a redshift of 6.8.’ Nature (2018). DOI: 10.1038/nature24631

Astronomers have looked back to a time soon after the Big Bang, and have discovered swirling gas in some of the earliest galaxies to have formed in the Universe. These ‘newborns’ – observed as they appeared nearly 13 billion years ago – spun like a whirlpool, similar to our own Milky Way. This is the first time that it has been possible to detect movement in galaxies at such an early point in the Universe’s history.

We’ve never been able to see the formation of galaxies in such detail, and we’ve never been able to measure the movement of gas in galaxies so early in the Universe’s history.

Stefano Carniani

Amanda Smith, ̽��ֱ�� of Cambridge

Artist's impression of spinning galaxy

Researcher profile: Renske Smit

Dr Renske Smit is a postdoctoral researcher and Rubicon Fellow at the Kavli Institute of Cosmology and is supported by the Netherlands Organisation for Scientific Research. Prior to arriving in Cambridge in 2016, she was a postdoctoral researcher at Durham ̽��ֱ�� and a PhD student at Leiden ̽��ֱ�� in the Netherlands.

Her research aims to understand how the first sources of light in the Universe came to be. In her daily work, she studies images of deep space, taken by telescopes such as the Hubble Space Telescope. To gather data, she sometimes travels to places such as Chile or Hawaii to work on big telescopes.

“In Cambridge, I have joined a team working on the James Webb Space Telescope, the most ambitious and expensive telescope ever built,” she says. “With this telescope, we might be able to see the very first stars for the first time. To have this kind of privileged access to world-leading data is truly a dream come true.

“I would like to contribute to changing the perception of what a science professor looks like. Women in the UK and worldwide are terribly underrepresented in science and engineering and as a result, people may feel women either don’t have the inclination or the talent to do science. I hope that one day I will teach students that don’t feel they represent the professor stereotype and make them believe in their own talent.”

̽��ֱ��text in this work is licensed under a Creative Commons Attribution 4.0 International License. For image use please see separate credits above.

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Icy ring around young planetary system has similar chemical fingerprint to our solar system

sc604 — Thu, 18 May 2017 15:00:00 +0000

Earlier observations of the star, known as Fomalhaut and located 25 light years from Earth, were taken in 2012 by astronomers using the Atacama Large Millimetre/submillimetre Array (ALMA), located in Chile. ̽��ֱ��2012 results were gathered when the telescope was still under construction, and while they only revealed about half of the debris disc, the observations provided hints about the nature and possible origin of the disc.

̽��ֱ��new observations offer a far more complete view of this glowing band of debris, a band of rubble resulting from comets smashing together near the outer edges of the planetary system. ̽��ֱ��gases observed within the ring by the team suggest that there are chemical similarities between its icy contents and comets in our own solar system.

“We can finally see the well-defined shape of the disc, which may tell us a great deal about the underlying planetary system responsible for its highly distinctive appearance,” said Meredith MacGregor, an astronomer at the Harvard-Smithsonian Center for Astrophysics, and lead author on one of two papers accepted for publication in the Astrophysical Journal describing these observations.

Fomalhaut is a relatively nearby star system and one of only about 20 in which planets have been imaged directly. ̽��ֱ��entire system is approximately 440 million years old, or about one-tenth the age of our solar system. As revealed in the new ALMA image, a brilliant band of icy dust about two billion kilometres wide has formed approximately 20 billion kilometres from the star.

Debris discs are common features around young stars and represent a dynamic and chaotic period in the history of a solar system. Astronomers believe they are formed by the ongoing collisions of comets and other solid objects, known as planetesimals, in the outer reaches of a recently formed planetary system. ̽��ֱ��leftover debris from these collisions absorbs light from its central star and re-radiates that energy as a faint glow that can be studied with ALMA.

Using the new ALMA data and detailed computer modelling, the researchers could calculate the precise location, width, and geometry of the disc. These parameters confirm that such a narrow ring is likely produced through the gravitational influence of planets in the system.

̽��ֱ��new observations are also the first to definitively show “apocenter glow,” a phenomenon predicted in a 2016 paper by Margaret Pan, a scientist at the Massachusetts Institute of Technology and co-author on the new papers. Like all objects with elongated orbits, the dusty material in the Fomalhaut disc travels more slowly when it is farthest from the star. As the dust slows down, it piles up, forming denser concentrations in the more distant portions of the disc. These dense regions can be seen by ALMA as brighter millimetre-wavelength emission.

Using the same dataset, but focusing on distinct millimetre-wavelength signals naturally emitted by molecules in space, the researchers also detected vast stores of carbon monoxide gas in precisely the same location as the debris disc.

“These data allowed us to determine that the abundance of carbon monoxide plus carbon dioxide around Fomalhaut is about the same as found in comets in our own solar system,” said Dr Luca Matrà of Cambridge’s Institute of Astronomy, and lead author of the team’s second paper. “This chemical kinship may indicate a similarity in comet formation conditions between the outer reaches of this planetary system and our own.” Matrà and his colleagues believe this gas is either released from continuous comet collisions or the result of a single, large impact between ‘supercomets’ hundreds of times more massive than Hale-Bopp.

̽��ֱ��presence of this well-defined debris disc around Fomalhaut, along with its curiously familiar chemistry, may indicate that this system is undergoing its own version of the Late Heavy Bombardment, a period approximately four billion years ago when the Earth and other planets were routinely struck by swarms of asteroids and comets left over from the formation of our solar system.

“Twenty years ago, the best millimetre-wavelength telescopes gave the first fuzzy maps of sand grains orbiting Fomalhaut. Now with ALMA’s full capabilities the entire ring of material has been imaged,” said Paul Kalas, an astronomer at the ̽��ֱ�� of California at Berkeley and principal investigator on these observations. “One day we hope to detect the planets that influence the orbits of these grains.”

Adapted from a National Radio Astronomy Observatory press release.

References:
Meredith A. MacGregor et al. 'A Complete ALMA Map of the Fomalhaut Debris Disk.' arXiv:1705.05867
L. Matrà et al. 'Detection of exocometary CO within the 440 Myr-old Fomalhaut belt: a similar CO+CO2 ice abundance in exocomets and Solar System comets.' arXiv:1705.05868

An international team of astronomers, including researchers from the ̽��ֱ�� of Cambridge, has made the most detailed image of the ring of dusty debris surrounding a young star and found that the ice content of colliding comets within it is similar to comets in our own solar system.

̽��ֱ��chemical kinship may indicate a similarity in comet formation conditions between the outer reaches of this planetary system and our own.

Luca Matra

ALMA (ESO/NAOJ/NRAO), M. MacGregor; NASA/ESA Hubble, P. Kalas; B. Saxton (NRAO/AUI/NSF)

Composite image of the Fomalhaut star system. ̽��ֱ��ALMA data, shown in orange, reveal the distant and eccentric debris disk in never-before-seen detail. ̽��ֱ��central dot is the unresolved emission from the star, which is about twice the mass of our sun.

̽��ֱ��text in this work is licensed under a Creative Commons Attribution 4.0 International License. For image use please see separate credits above.

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