A greedy giant

NGC 1222

 Credit: ESA/Hubble & NASA

NGC 1222, seen in this image taken with the Wide Field Camera 3 on board the NASA/ESA Hubble Space Telescope (HST), is a galaxy with a rather eventful story to tell. NGC 1222 has been described as a peculiar example of a type of galaxy known as a lenticular galaxy. Typically, this kind of galaxy would present a rather smooth appearance on the sky and would consist mostly of old, reddish stars. A bit dull, perhaps.

But NGC 1222 is certainly not a typical member of its class — and it’s anything but dull.

Observations show the characteristic features of very recent star formation on a huge scale — an event known as a starburst. The reason for all this violent activity is caused by the fact that NGC 1222 is not alone. It actually contains three compact regions, each of which appears to be the central nucleus of a galaxy. Astronomers think that NGC 1222 is in the process of swallowing up two much smaller dwarf galaxies that strayed too close to it. It is likely that the encounter was the trigger for the starburst in NGC 1222, bringing in fresh supplies of gas that are now fuelling the burst of star formation.

Although its peculiarities were first seen in photographic images, these were not able to reveal the level of fine detail that can be recovered by Hubble. The image taken by Hubble allows us to see an astonishing amount of structure in this galaxy, emphasising its colourful history. Against the smooth background of old stars that was the original lenticular galaxy, we can clearly see dark filaments of dust and bright filaments of gas, both associated with the powerful star formation process.

Source: ESA/Hubble - Space Telescope/Images

Markarian 1018: Starvation Diet for Black Hole Dims Brilliant Galaxy

Markarian 1018

Credit X-ray: NASA/CXC/Univ of Sydney/R.McElroy et al, Optical: ESO/CARS Survey

 JPEG (259.8 kb) - Large JPEG (1.9 MB) - Tiff (5.2 MB) - More Images

Astronomers may have solved the mystery of the peculiar volatile behavior of a supermassive black hole at the center of a galaxy. Combined data from NASA's Chandra X-ray Observatory and other observatories suggest that the black hole is no longer being fed enough fuel to make its surroundings shine brightly.

Many galaxies have an extremely bright core, or nucleus, powered by material falling toward a supermassive black hole. These so-called "active galactic nuclei" or AGN, are some of the brightest objects in the Universe.

Astronomers classify AGN into two main types based on the properties of the light they emit. One type of AGN tends to be brighter than the other. The brightness is generally thought to depend on either or both of two factors: the AGN could be obscured by surrounding gas and dust, or it could be intrinsically dim because the rate of feeding of the supermassive black hole is low.

Some AGN have been observed to change once between these two types over the course of only 10 years, a blink of an eye in astronomical terms. However, the AGN associated with the galaxy Markarian 1018 stands out by changing type twice, from a faint to a bright AGN in the 1980s and then changing back to a faint AGN within the last five years. A handful of AGN have been observed to make this full-cycle change, but never before has one been studied in such detail. During the second change in type the Markarian 1018 AGN became eight times fainter in X-rays between 2010 and 2016.

After discovering the AGN's fickle nature during a survey project using ESO's Very Large Telescope (VLT), astronomers requested and received time to observe it with both NASA's Chandra X-ray Observatory and Hubble Space Telescope. The accompanying graphic shows the AGN in optical light from the VLT (left) with a Chandra image of the galaxy's central region in X-rays showing the point source for the AGN (right).

Data from ground-based telescopes including the VLT allowed the researchers to rule out a scenario in which the increase in the brightness of the AGN was caused by the black hole disrupting and consuming a single star. The VLT data also cast doubt on the possibility that changes in obscuration by intervening gas cause changes in the brightness of the AGN.

However, the true mechanism responsible for the AGN's surprising variation remained a mystery until Chandra and Hubble data was analyzed. Chandra observations in 2010 and 2016 conclusively showed that obscuration by intervening gas was not responsible for the decline in brightness. Instead, models of the optical and ultraviolet light detected by Hubble, NASA's Galaxy Evolution Explorer (GALEX) and the Sloan Digital Sky Survey in the bright and faint states showed that the AGN had faded because the black hole was being starved of infalling material. This starvation also explains the fading of the AGN in X-rays.

One possible explanation for this starvation is that the inflow of fuel is being disrupted. This disruption could be caused by interactions with a second supermassive black hole in the system. A black hole binary is possible as the galaxy is the product of a collision and merger between two large galaxies, each of which likely contained a supermassive black hole in its center.

The list observatories used in this finding also include NASA's Nuclear Spectroscopic Telescope Array (NuSTAR) mission and Swift spacecraft.

Two papers, one with the first author of Bernd Husemann (previously at ESO and currently at the Max Planck Institute for Astronomy) and the other with Rebecca McElroy (University of Sydney), describing these results appeared in the September 2016 issue of Astronomy & Astrophysics journal.

NASA's Marshall Space Flight Center in Huntsville, Alabama, manages the Chandra program for NASA's Science Mission Directorate in Washington. The Smithsonian Astrophysical Observatory in Cambridge, Massachusetts, controls Chandra's science and flight operations.

Fast Facts for Markarian 1018:

Scale: Main image is 2.64 arcmin across (about 440,000 light years)
Category: Quasars & Active Galaxies
Coordinates (J2000): RA 02h 06m 15.99s | Dec 00° 17' 29.20"
Constellation: Cetus
Observation Date: 27 Nov 2010, 25 Feb 2016
Observation Time: 13 hours 53 min.
Obs. ID: 12868, 18789
Instrument: ACIS
References: McElroy, R. et al, 2016, A&A 593, L8; arXiv:1609.04423; Husemann, B. et al, 2016, A&A 593, L9; arXiv:1609.04425
Color Code: X-ray (Purple); Optical (Red, Green, Blue)
Distance Estimate: About 590 million light years (z=0.043)

Source: NASA’s Chandra X-ray Observatory

Astrophysicists map the Milky Way

MULTIMEDIA

HI4PI Animation from ICRAR on Vimeo

Using real data, this animation shows radio emission from neutral hydrogen atoms located in our galaxy, the Milky Way, and our neighbouring dwarf galaxies, the Large and Small Magellanic Clouds. It has been produced using observations made with the 100 metre Max-Planck radio telescope in Effelsberg, Germany and the 64 metre CSIRO radio telescope in Parkes, Australia. The colours reflect the approaching (purple/blue) and receding (orange/green)hydrogen gas motion while the brightness traces its amount. Credit: Lister Staveley-Smith, Benjamin Winkel and the HI4PI collaboration.

This animation shows the HI 21-cm line emission of neutral atomic hydrogen of the Milky Way galaxy and the neighbouring galaxies, like the Andromeda galaxy and the Magellanic Clouds, both visible in the lower half of the panel. It has been derived from observational data of the 100-m Effelsberg radio telescope operated by the Max-Planck-Institut für Radioastronomie/Germany and the CSIRO’s 64-m radio telescope at Parkes/Australia. The animation starts at the most negative velocities (blue shifted infalling gas) and subsequently evolves to positive radial velocities (red shifted, receding gas). Credit: Benjamin Winkel for the HI4PI collaboration

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This HI4PI map was produced using data from the 100 metre Max-Planck radio telescope in Effelsberg, Germany and the 64 metre CSIRO radio telescope in Parkes, Australia. The image colours reflect gas at differing velocities. The plane of the Milky Way runs horizontally across the middle of the image. The Magellanic Clouds can be seen at the lower right. Image credit: Benjamin Winkel and the HI4PI collaboration. Hi-res image

This HI4PI map was produced using data from the 100 metre Max-Planck radio telescope in Effelsberg, Germany and the 64 metre CSIRO radio telescope in Parkes, Australia. The image intensity reflects the total hydrogen content. The plane of the Milky Way runs horizontally across the middle of the image. Image credit: Benjamin Winkel and the HI4PI collaboration. Hi-res image

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Astrophysicists map the Milky Way

Scientists have created a detailed map of the Milky Way using two of the world’s largest fully steerable radio telescopes in Germany and Australia.

The research looked at neutral atomic hydrogen—the most abundant element in space and the main component of stars and galaxies—across the whole sky in a survey known as HI4PI.

The project required more than a million individual observations and about ten billion individual data points.

University of Bonn astronomer Dr Juergen Kerp said although neutral hydrogen is fairly easy to detect with modern radio telescopes, mapping the whole sky is a significant achievement.

“Radio ‘noise’ caused by mobile phones and broadcast stations pollute the faint emissions coming from stars and galaxies in the Universe,” he said.

“So sophisticated computer algorithms have to be developed to clean each individual data point of this unwanted human interference.

“Next to the thousands of observing hours an even larger amount of time has been spent creating the final scientific data product released today.”

The HI4PI survey used CSIRO’s Parkes Observatory and the Effelsberg 100m Radio Telescope operated by the Max-Planck Institute for Radio Astronomy.

It improves the previous neutral hydrogen study, the Leiden-Argentine-Bonn (LAB) survey, by a factor of two in sensitivity and a factor of four in angular resolution.

Professor Lister Staveley-Smith, from the International Centre for Radio Astronomy Research, said the study reveals fine details of structures between stars in the Milky Way for the first time.

“These structures had been smeared out by the coarse sampling of the sky in the LAB survey,” he said.

“Pilot studies of the HI4PI data show a wealth of filamentary structures never seen before.

“Tiny clouds become visible that appear to have fuelled star formation in the Milky Way for billions of years.

“These objects are too dim and too small to be detected even in the other galaxies closest to us.”

Dr Benjamin Winkel, from the Max Planck Institute for Radio Astronomy, said having a clearer picture of the hydrogen in the Milky Way would also help astronomers to explore galaxies even at cosmological distances.

“Like the clouds at the sky, all observations we receive from the distant Universe have to pass through hydrogen in our own Milky Way,” he said.

“The HI4PI data allows us to correct accurately for all these hydrogen clouds and clean the window we are watching through.”

The research has been published today in the journal Astronomy and Astrophysics.

HI4PI data will be freely available to scientists around the world through the Strasbourg astronomical data centre.

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Publication Details

‘HI4PI: A full-sky Hi survey based on EBHIS and GASS’, published in the Astronomy and Astrophysics Journal October 20th, 2016. 
Click here for the research paper

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More Information

The name ‘HI4PI’ is drawn from the fact that this study measures radio wavelength radiation emitted from neutral atomic hydrogen atoms (HI) across the entire sky. Observing in all directions for an ‘all-sky’ survey in this way creates a sphere of data, and because the solid angle (a two-dimensional analogue of an angle) of a sphere is equal to 4π ’steradians’ (or square radians), we chose the name HI4PI for this work.

The International Centre for Radio Astronomy Research (ICRAR) is a joint venture between Curtin University and The University of Western Australia with support and funding from the State Government of Western Australia.

The Argelander Institut fuer Astronomy (AIfA) is an academic, research and educational institute and a part of the Department of Physics and Astronomy at the University of Bonn, Germany. The institute conducts cutting-edge research over a broad range of theoretical and observational topics from stars to cosmology.

The Max-Planck-Institut fuer Radioastronomie main area of research is radio astronomy but the activities of the institute encompass the whole area of astronomical observations throughout the electromagnetic spectrum.

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Contact Information

Professor Lister Staveley-Smith (University of Western Australia, ICRAR)
E: Lister.Staveley-Smith@icrar.org
M: +61 425 212 592

Dr Juergen Kerp (Argelander Institute for Astronomy, University of Bonn, Germany)
E: jkerp@astro.uni-bonn.de
M: +49 228 73 3667

Dr. Benjamin Winkel (Max Planck Institute for Radio Astronomy)
E: bwinkel@mpifr.de
M: +49 225 73 01167

Pete Wheeler, Media Contact, ICRAR
 E: pete.wheeler@icrar.org
M: +61 423 982 018

Source: International Centre for Radio Astronomy Research (ICRAR)

Sculpting Solar Systems

PR Image eso1640a

Protoplanetary discs observed with SPHERE

PR Image eso1640b

Disc around the young star RX J1615

PR Image eso1640c

Disc around the star HD 97048

PR Image eso1640d

Disc around the star HD 135344B

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ESO’s SPHERE instrument reveals protoplanetary discs being shaped by newborn planets

Sharp new observations have revealed striking features in planet-forming discs around young stars. The SPHERE instrument, mounted on ESO’s Very Large Telescope, has made it possible to observe the complex dynamics of young solar systems — including one seen developing in real-time. The recently published results from three teams of astronomers showcase SPHERE’s impressive capability to capture the way planets sculpt the discs that form them — exposing the complexities of the environment in which new worlds are formed.

Three teams of astronomers have made use of SPHERE, an advanced exoplanet-hunting instrument on the Very Large Telescope (VLT) at ESO’s Paranal Observatory, in order to shed light on the enigmatic evolution of fledgling planetary systems. The explosion in the number of known exoplanets in recent years has made the study of them one of the most dynamic fields in modern astronomy.

Today it is known that planets form from vast discs of gas and dust encircling newborn stars, known as protoplanetary discs. These can extend for thousands of millions of kilometres. Over time, the particles in these protoplanetary discs collide, combine and eventually build up into planet-sized bodies. However, the finer details of the evolution of these planet-forming discs remain mysterious.

SPHERE is a recent addition to the VLT’s array of instruments and with its combination of novel technologies, it provides a powerful method to directly image the fine details of protoplanetary discs [1]. The interaction between protoplanetary discs and growing planets can shape the discs into various forms: vast rings, spiral arms or shadowed voids. These are of special interest as an unambiguous link between these structures and the sculpting planets is yet to be found; a mystery astronomers are keen to solve. Fortunately, SPHERE’s specialised capabilities make it possible for research teams to observe these striking features of protoplanetary discs directly.

For example, RX J1615 is a young star, which lies in the constellation of Scorpius, 600 light-years from Earth. A team led by the Jos de Boer, of Leiden Observatory in the Netherlands, found a complex system of concentric rings surrounding the young star, forming a shape resembling a titanic version of the rings that encircle Saturn. Such an intricate sculpting of rings in a protoplanetary disc has only been imaged a handful of times before, and even more excitingly, the entire system seems to be only 1.8 million years old. The disc shows hints of being shaped by planets still in the process of formation.

The age of the newly detected protoplanetary disc makes RX J1615 an outstanding system, as most other examples of protoplanetary discs detected so far are relatively old or evolved. De Boer’s unexpected result was quickly echoed by the findings of a team led by Christian Ginski, also of Leiden Observatory. They observed the young star HD 97048, located in the constellation of Chamaeleon, about 500 light-years from Earth. Through painstaking analysis, they found that the juvenile disc around this star has also formed into concentric rings. The symmetry of these two systems is a surprising result, as most protoplanetary systems contain a multitude of asymmetrical spiral arms, voids and vortexes. These discoveries significantly raise the number of known systems with multiple highly symmetrical rings.

A particularly spectacular example of the more common asymmetric disc was captured by a group of astronomers led by Tomas Stolker of the Anton Pannekoek Institute for Astronomy, the Netherlands. This disc surrounds the star HD 135344B, about 450 light-years away. Although this star has been well-studied in the past, SPHERE allowed the team to see the star’s protoplanetary disc in more detail than ever before. The large central cavity and two prominent spiral arm-like structures are thought to have been created by one or multiple massive protoplanets, destined to become Jupiter-like worlds.

In addition, four dark streaks, apparently shadows thrown by the movement of material within HD 135344B's disc, were observed. Remarkably, one of the streaks noticeably changed in the months between observing periods: a rare example of observing planetary evolution occur in real time, hinting at changes occurring in the inner disc regions that can not be directly detected by SPHERE. As well as producing beautiful images, these flickering shadows provide a unique way of probing the  dynamics of innermost disc regions.

As with the concentric rings found by de Boer and Ginski, these observations by Stolker’s team prove that the complex and changing environment of the discs surrounding young stars are still capable of producing surprising new discoveries. By building an impressive body of knowledge about these protoplanetary discs, these teams are stepping closer to understanding how planets shape the discs that form them — and therefore understanding planet formation itself.

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Notes

[1] SPHERE had first light in June 2014. The instrument uses advanced adaptive optics to remove atmospheric distortion, a coronagraph to block most of the light from the central star and a combination of differential imaging and polarimetry to isolate the light from features in the disc.

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More Information

The research of de Boer, Ginski and Stolker and their colleagues in the SPHERE consortium is now accepted for publication in the journal Astronomy and Astrophysics. Their papers are entitled: "Direct detection of scattered light gaps in the transitional disk around HD 97048 with VLT/SPHERE"; "Shadows cast on the transition disk of HD 135344B: Multi-wavelength VLT/SPHERE polarimetric differential imaging", and "Multiple rings in the transition disk and companion candidates around RX J1615.3-3255: High contrast imaging with VLT/SPHERE". All three of papers have been created in the framework of the SPHERE GTO program, led by Carsten Dominik, University of Amsterdam.

ESO is the foremost intergovernmental astronomy organisation in Europe and the world’s most productive ground-based astronomical observatory by far. It is supported by 16 countries: Austria, Belgium, Brazil, the Czech Republic, Denmark, France, Finland, Germany, Italy, the Netherlands, Poland, Portugal, Spain, Sweden, Switzerland and the United Kingdom, along with the host state of Chile. ESO carries out an ambitious programme focused on the design, construction and operation of powerful ground-based observing facilities enabling astronomers to make important scientific discoveries. ESO also plays a leading role in promoting and organising cooperation in astronomical research. ESO operates three unique world-class observing sites in Chile: La Silla, Paranal and Chajnantor. At Paranal, ESO operates the Very Large Telescope, the world’s most advanced visible-light astronomical observatory and two survey telescopes. VISTA works in the infrared and is the world’s largest survey telescope and the VLT Survey Telescope is the largest telescope designed to exclusively survey the skies in visible light. ESO is a major partner in ALMA, the largest astronomical project in existence. And on Cerro Armazones, close to Paranal, ESO is building the 39-metre European Extremely Large Telescope, the E-ELT, which will become “the world’s biggest eye on the sky”.

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Links

• Research paper by Jos de Boer et al.
• Research paper by Christian Ginski et al.
• Research paper by Tomas Stolker et al.

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Contacts

Tomas Stolker
Anton Pannekoek Institute for Astronomy
Amsterdam, the Netherlands
Tel: +3120525 8152
Email: T.Stolker@uva.nl

Jos de Boer
Leiden University
Leiden, the Netherlands
Tel: +31715278139
Email: deboer@strw.leidenuniv.nl

Christian Ginski
Leiden University
Leiden, the Netherlands
Tel: +31715278139
Email: ginski@strw.leidenuniv.nl

Richard Hook
ESO Public Information Officer
Garching bei München, Germany
Tel: +49 89 3200 6655
Cell: +49 151 1537 3591
Email: rhook@eso.org

Source: ESO

Tsunami of Stars and Gas Produces Dazzling Eye-shaped Feature in Galaxy

Dazzling eyelid-like features bursting with stars in galaxy IC 2163 formed from a tsunami of stars and gas triggered by a glancing collision with galaxy NGC 2207 (a portion of its spiral arm is shown on right side of image). ALMA image of carbon monoxide (orange), which revealed motion of the gas in these features, is shown on top of Hubble image (blue) of the galaxy. Credit: M. Kaufman; B. Saxton (NRAO/AUI/NSF); ALMA (ESO/NAOJ/NRAO); NASA/ESA Hubble Space Telescope

Annotated image showing dazzling eyelid-like features bursting with stars in galaxy IC 2163 formed from a tsunami of stars and gas triggered by a glancing collision with galaxy NGC 2207 (a portion of its spiral arm is shown on right side of image). ALMA image of carbon monoxide (orange), which revealed motion of the gas in these features, is shown on top of Hubble image (blue) of the galaxy. Credit: M. Kaufman; B. Saxton (NRAO/AUI/NSF); ALMA (ESO/NAOJ/NRAO); NASA/ESA Hubble Space Telescope

Galaxies IC 2163 (left) and NGC 2207 (right) recently grazed past each other, triggering a tsunami of stars and gas in IC 2163 and producing the dazzling eyelid-like features there. ALMA image of carbon monoxide (orange), which revealed motion of the gas in these features, is shown on top of Hubble image (blue) of the galaxy pair. Credit: M. Kaufman; B. Saxton (NRAO/AUI/NSF); ALMA (ESO/NAOJ/NRAO); NASA/ESA Hubble Space Telescope

Astronomers using the Atacama Large Millimeter/submillimeter Array (ALMA) have discovered a tsunami of stars and gas that is crashing midway through the disk of a spiral galaxy known as IC 2163. This colossal wave of material – which was triggered when IC 2163 recently sideswiped another spiral galaxy dubbed NGC 2207 – produced dazzling arcs of intense star formation that resemble a pair of eyelids.

“Although galaxy collisions of this type are not uncommon, only a few galaxies with eye-like, or ocular, structures are known to exist,” said Michele Kaufman, an astronomer formerly with The Ohio State University in Columbus and lead author on a paper published in the Astrophysical Journal.

Kaufman and her colleagues note that the paucity of similar features in the observable universe is likely due to their ephemeral nature. “Galactic eyelids last only a few tens of millions of years, which is incredibly brief in the lifespan of a galaxy. Finding one in such a newly formed state gives us an exceptional opportunity to study what happens when one galaxy grazes another,” said Kaufman.

The interacting pair of galaxies resides approximately 114 million light-years from Earth in the direction of the constellation Canis Major. These galaxies brushed past each other – scraping the edges of their outer spiral arms – in what is likely the first encounter of an eventual merger.

Using ALMA’s remarkable sensitivity and resolution, the astronomers made the most detailed measurements ever of the motion of carbon monoxide gas in the galaxy’s narrow eyelid features. Carbon monoxide is a tracer of molecular gas, which is the fuel for star formation.

The data reveal that the gas in the outer portion of IC 2163’s eyelids is racing inward at speeds in excess of 100 kilometers a second. This gas, however, quickly decelerates and its motion becomes more chaotic, eventually changing trajectory and aligning itself with the rotation of the galaxy rather than continuing its pell-mell rush toward the center.

“What we observe in this galaxy is very much like a massive ocean wave barreling toward shore until it interacts with the shallows, causing it to lose momentum and dump all of its water and sand on the beach,” said Bruce Elmegreen, a scientist with IBM’s T.J. Watson Research Center in Yorktown Heights, New York, and co-author on the paper.

“Not only do we find a rapid deceleration of the gas as it moves from the outer to the inner edge of the eyelids, but we also measure that the more rapidly it decelerates, the denser the molecular gas becomes,” said Kaufman. “This direct measurement of compression shows how the encounter between the two galaxies drives gas to pile up, spawn new star clusters and form these dazzling eyelid features.”

Computer models predict that such eyelid-like features could evolve if galaxies interacted in a very specific manner. "This evidence for a strong shock in the eyelids is terrific. It's all very well to have a theory and simulations suggesting it should be true, but real observational evidence is great," said Curtis Struck, a professor of astrophysics at Iowa State University in Ames and co-author on the paper.

“ALMA showed us that the velocities of the molecular gas in the eyelids are on the right track with the predictions we get from computer models,” said Kaufman. “This critical test of encounter simulations was not possible before.”

Astronomers believe that such collisions between galaxies were common in the early universe when galaxies were closer together. At that time, however, galactic disks were generally clumpy and irregular, so other processes likely overwhelmed the formation of similar eyelid features.

The authors continue to study this galaxy pair and currently are comparing the properties (e.g., locations, ages, and masses) of the star clusters previously observed with NASA’s Hubble Space Telescope with the properties of the molecular clouds observed with ALMA. They hope to better understand the differences between molecular clouds and star clusters in the eyelids and those elsewhere in the galaxy pair.

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

# # #

This research is presented in a paper titled “Ocular Shock Front in the Colliding Galaxy IC 2163” by M. Kaufman et al., published in Astrophysical Journal. [Preprint: https://arxiv.org/abs/1608.02130].

The Atacama Large Millimeter/submillimeter Array (ALMA), an international astronomy facility, is a partnership of ESO, the U.S. National Science Foundation (NSF) and the National Institutes of Natural Sciences (NINS) of Japan in cooperation with the Republic of Chile. ALMA is funded by ESO on behalf of its Member States, by NSF in cooperation with the National Research Council of Canada (NRC) and the National Science Council of Taiwan (NSC) and by NINS in cooperation with the Academia Sinica (AS) in Taiwan and the Korea Astronomy and Space Science Institute (KASI).

ALMA construction and operations are led by ESO on behalf of its Member States; by the National Radio Astronomy Observatory (NRAO), managed by Associated Universities, Inc. (AUI), on behalf of North America; and by the National Astronomical Observatory of Japan (NAOJ) on behalf of East Asia. The Joint ALMA Observatory (JAO) provides the unified leadership and management of the construction, commissioning and operation of ALMA.

Contact: 

Charles Blue
NRAO Public Information Officer
+1 434.296.0314; cblue@nrao.edu

Source: National Radio Astronomy Observatory (NRAO)

Study confirms that novae, a type of explosive phenomenon in stars, are main source of lithium in the universe

Nova Sagittarii 2015 N.2

Copyright  Ajai Talwar

Large amounts of beryllium-7, an element that decays into lithium, have been found inside nova Sagittarii 2015 N.2

Lithium, the lightest solid element in existence, plays an important role in our lives, both at the biological and the technological level. Like the majority of chemical elements, its origins stem back to astrophysical phenomena, but its point of genesis was so far unclear. Recently, a group of researchers detected enormous quantities of beryllium-7 –an unstable element which decays into lithium in 53.2 days– inside nova Sagittarii 2015 N.2, which suggests that novae are the main source of lithium in the galaxy.

Practically every chemical element has an astronomical origin.  A first genesis took place in what is known as primordial nucleosynthesis, shortly after the Big Bang (between ten seconds and twenty minutes after). Light elements were then formed: hydrogen (75%), helium (25%) and a very small amount of lithium and beryllium.

The remaining chemical elements were formed in stars, either through fusion of other elements inside the nucleus –which begins with the fusion of hydrogen into helium and produces increasingly heavy elements until iron is reached- or through other processes such as supernovae explosions or reactions in the atmosphere of giant stars where, among others, gold, lead and copper are produced. Those elements in turn were then recycled into new stars and planets until the present day.

"But lithium posed a problem: we knew that 25% of existing lithium comes from primordial nucleosynthesis, but we were not able to trace the origins of the remaining 75%", says Luca Izzo, researcher at the Institute of Astrophysics of Andalusia (IAA-CSIC) involved in the study.

Solution to the lithium enigma

The solution to the enigma of the origin of lithium lies, according to this study, in the novae, explosive phenomena occurring in binary star systems in which one of the stars is a white dwarf. The white dwarf can nab material from its twin star and form a superficial layer of hydrogen which, when it reaches a certain density, will trigger an explosion –a nova– which can increase the brightness of a star up to one hundred thousand times. After a few weeks the system stabilizes and the process starts again.

Artist concept of a binary system similar to the one that originated the nova Sagittarii 2015 N.2

Credit: David A. Hardy y PPARC.

The researchers studied nova Sagittarii 1015 N.2 (also known as V5668 Sgr), which was detected on March 15^th, 2015, and remained visible for more than eighty days. The observation, made with the UVES instrument of the Very Large Telescope (ESO) in the course of twenty four days, made it possible for the first time to follow the evolution of the beryllium-7 signal inside a nova and even to calculate the amount of it present. "Beryllium-7 is an unstable element which decays into lithium in 53.2 days, so its presence is an unequivocal sign of the existence of lithium", says Christina Thöne, researcher at the Institute of Astrophysics of Andalusia (IAA-CSIC).

The existence of beryllium-7 had been previously documented in another nova, but the measure of the amount of lithium which would be ultimately produced from it on nova Sagittarii 1015 N.2 came as a surprise. "We’re talking about an amount of lithium ten times greater than that in the Sun," says Luca Izzo (IAA-CSIC). "With these amounts in mind, two similar novae a year would suffice to account for all the lithium in our galaxy, the Milky Way. Novae seem to be the predominant source of lithium in the universe," he concludes.

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Reference: 

P. Molaro, L. Izzo et al. "Highly Enriched ⁷Be in the ejecta of Nova Sagittarii 2015 No. 2 (V5668 Sgr) and the Galactic ⁷Li origin". Monthly Notices of the Royal Astronomical Society, Vol. 463 

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  Contact:

Instituto de Astrofísica de Andalucía (IAA-CSIC)
Unidad de Divulgación y Comunicación
Silbia López de Lacalle - sll[arroba]iaa.es - 958230532

Source:  Instituto de Astrofísica de Andalucía (IAA-CSIC)

Close Galactic Encounter Leaves "Nearly Naked" Supermassive Black Hole

Artist's conception of how the "nearly naked" supermassive black hole originated

Credit: Bill Saxton, NRAO/AUI/NSF

Hi-res image

Astronomer Jim Condon explains the discovery and significance of B3 1715+425, a "nearly naked" supermassive black hole.

Astronomers using the super-sharp radio vision of the National Science Foundation's Very Long Baseline Array (VLBA) have found the shredded remains of a galaxy that passed through a larger galaxy, leaving only the smaller galaxy's nearly-naked supermassive black hole to emerge and speed away at more than 2,000 miles per second.

The galaxies are part of a cluster of galaxies more than 2 billion light-years from Earth. The close encounter, millions of years ago, stripped the smaller galaxy of nearly all its stars and gas. What remains is its black hole and a small galactic remnant only about 3,000 light-years across. For comparison, our Milky Way Galaxy is approximately 100,000 light-years across.

The discovery was made as part of a program to detect supermassive black holes, millions or billions of times more massive than the Sun, that are not at the centers of galaxies. Supermassive black holes reside at the centers of most galaxies. Large galaxies are thought to grow by devouring smaller companions. In such cases, the black holes of both are expected to orbit each other, eventually merging.

"We were looking for orbiting pairs of supermassive black holes, with one offset from the center of a galaxy, as telltale evidence of a previous galaxy merger," said James Condon, of the National Radio Astronomy Observatory. "Instead, we found this black hole fleeing from the larger galaxy and leaving a trail of debris behind it," he added.

"We've not seen anything like this before," Condon said.

The astronomers began their quest by using the VLBA to make very high resolution images of more than 1,200 galaxies, previously identified by large-scale sky surveys done with infrared and radio telescopes. Their VLBA observations showed that the supermassive black holes of nearly all these galaxies were at the centers of the galaxies.

However, one object, in a cluster of galaxies called ZwCl 8193, did not fit that pattern. Further studies showed that this object, called B3 1715+425, is a supermassive black hole surrounded by a galaxy much smaller and fainter than would be expected. In addition, this object is speeding away from the core of a much larger galaxy, leaving a wake of ionized gas behind it.

The scientists concluded that B3 1715+425 is what has remained of a galaxy that passed through the larger galaxy and had most of its stars and gas stripped away by the encounter -- a "nearly naked" supermassive black hole.

The speeding remnant, the scientists said, probably will lose more mass and cease forming new stars.

"In a billion years or so, it probably will be invisible," Condon said. That means, he pointed out, that there could be many more such objects left over from earlier galactic encounters that astronomers can't detect.

The scientists will keep looking, however. They're observing more objects, in a long-term project with the VLBA. Since their project is not time-critical, Condon explained, they use "filler time" when the telescope is not in use for other observations.

"The data we get from the VLBA is very high quality. We get the positions of the supermassive black holes to extremely good precision. Our limiting factor is the precision of the galaxy positions seen at other wavelengths that we use for comparison," Condon said. With new optical telescopes that will come on line in future years, such as the Large Synoptic Survey Telescope (LSST), he said, they will then have improved images that can be compared with the VLBA images. They hope that this will allow them to discover more objects like B3 1714+425.

"And also maybe some of the binary supermassive black holes we originally sought," he said.

Condon worked with Jeremy Darling of the University of Colorado, Yuri Kovalev of the Astro Space Center of the Lebedev Physical Institute in Moscow, and Leonid Petrov of the Astrogeo Center in Falls Church, Virginia. The scientists are reporting their findings in the Astrophysical Journal.

The VLBA, dedicated in 1993, now is part of the Long Baseline Observatory. It uses ten, 25-meter-diameter dish antennas distributed from Hawaii to St. Croix in the Caribbean. It is operated from the NRAO's Domenici Science Operations Center in Socorro, NM. All ten antennas work together as a single telescope with the greatest resolving power available to astronomy. This unique capability has produced landmark contributions to numerous scientific fields, ranging from Earth tectonics, climate research, and spacecraft navigation, to cosmology.

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

Media Contact:
 
Dave Finley, Public Information Officer
(575) 835-7302
dfinley@nrao.edu

Source: National Radio Astronomy Observatory

Pillars of Destruction

 PR Image eso1639a

Region R44 in the Carina Nebula 

PR Image eso1639b

Pillars of destruction

 

PR Image eso1639c

Region R18 in the Carina Nebula

 

PR Image eso1639d

Region R37 in the Carina Nebula

 

PR Image eso1639e

Region R45 in the Carina Nebula

 

PR Image eso1639f

Star cluster Trumpler 14

 

PR Image eso1639g

Bok Globule in the Carina Nebula

 

PR Image eso1639h

Mystic Mountain 

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Videos

PR Video eso1639b

3D Animation of the Carina Nebula

PR Video eso1639a

Zooming in on the Carina Nebula

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Colourful Carina Nebula blasted by brilliant nearby stars

Spectacular new observations of vast pillar-like structures within the Carina Nebula have been made using the MUSE instrument on ESO’s Very Large Telescope. The different pillars analysed by an international team seem to be pillars of destruction — in contrast to the name of the iconic Pillars of Creation in the Eagle Nebula, which are of similar nature.

The spires and pillars in the new images of the Carina Nebula are vast clouds of dust and gas within a hub of star formation about 7500 light-years away. The pillars in the nebula were observed by a team led by Anna McLeod, a PhD student at ESO, using the MUSE instrument on ESO’s Very Large Telescope.

The great power of MUSE is that it creates thousands of images of the nebula at the same time, each at a different wavelength of light. This allows astronomers to map out the chemical and physical properties of the material at different points in the nebula.

Images of similar structures, the famous Pillars of Creation [1] in the Eagle Nebula and formations in NGC 3603, were combined with the ones displayed here. In total ten pillars have been observed, and in so doing a clear link was observed between the radiation emitted by nearby massive stars and the features of the pillars themselves.

In an ironic twist, one of the first consequences of the formation of a massive star is that it starts to destroy the cloud from which it was born. The idea that massive stars will have a considerable effect on their surroundings is not new: such stars are known to blast out vast quantities of powerful, ionising radiation — emission with enough energy to strip atoms of their orbiting electrons. However, it is very difficult to obtain observational evidence of the interplay between such stars and their surroundings. <

The team analysed the effect of this energetic radiation on the pillars: a process known as photoevaporation, when gas is ionised and then disperses away. By observing the results of photoevaporation — which included the loss of mass from the pillars — they were able to deduce the culprits. There was a clear correlation between the amount of ionising radiation being emitted by nearby stars, and the dissipation of the pillars.

This might seem like a cosmic calamity, with massive stars turning on their own creators. However the complexities of the feedback mechanisms between the stars and the pillars are poorly understood. These pillars might look dense, but the clouds of dust and gas which make up nebulae are actually very diffuse. It is possible that the radiation and stellar winds from massive stars actually help create denser spots within the pillars, which can then form stars.

These breathtaking celestial structures have more to tell us, and MUSE is an ideal instrument to probe them with. 

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Notes

[1] The Pillars of Creation are an iconic image, taken with the NASA/ESA Hubble Space Telescope, making them the most famous of these structures. Also known as elephant trunks, they can be several light-years in length.

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More Information

This research was presented in a paper entitled “Connecting the dots: a correlation between ionising radiation and cloud mass-loss rate traced by optical integral field spectroscopy“, by A. F. McLeod et al., published in the Monthly Notices of the Royal Astronomical Society.

The team is composed of A. F. McLeod (ESO, Garching, Germany), M. Gritschneder (Universitäts-Sternwarte, Ludwig-Maximilians-Universität, Munich, Germany), J. E. Dale (Universitäts-Sternwarte, Ludwig-Maximilians-Universität, Munich, Germany), A. Ginsburg (ESO, Garching, Germany), P. D.Klaassen (UK Astronomy Technology Centre, Royal Observatory Edinburgh, UK), J. C. Mottram (Max Planck Institute for Astronomy, Heidelberg, Germany), T. Preibisch (Universitäts-Sternwarte, Ludwig-Maximilians-Universität, Munich, Germany), S. Ramsay (ESO, Garching, Germany), M. Reiter (University of Michigan Department of Astronomy, Ann Arbor, Michigan, USA) and L. Testi (ESO, Garching, Germany).

ESO is the foremost intergovernmental astronomy organisation in Europe and the world’s most productive ground-based astronomical observatory by far. It is supported by 16 countries: Austria, Belgium, Brazil, the Czech Republic, Denmark, France, Finland, Germany, Italy, the Netherlands, Poland, Portugal, Spain, Sweden, Switzerland and the United Kingdom, along with the host state of Chile. ESO carries out an ambitious programme focused on the design, construction and operation of powerful ground-based observing facilities enabling astronomers to make important scientific discoveries. ESO also plays a leading role in promoting and organising cooperation in astronomical research. ESO operates three unique world-class observing sites in Chile: La Silla, Paranal and Chajnantor. At Paranal, ESO operates the Very Large Telescope, the world’s most advanced visible-light astronomical observatory and two survey telescopes. VISTA works in the infrared and is the world’s largest survey telescope and the VLT Survey Telescope is the largest telescope designed to exclusively survey the skies in visible light. ESO is a major partner in ALMA, the largest astronomical project in existence. And on Cerro Armazones, close to Paranal, ESO is building the 39-metre European Extremely Large Telescope, the E-ELT, which will become “the world’s biggest eye on the sky”.

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Link

• Research paper 
• Photos of the VLT

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Contacts

Anna Faye McLeod
ESO
Garching bei München, Germany
Tel: +49 89 3200 6321
Email: amcleod@eso.org

Mathias Jäger

Public Information Officer

Garching bei München, Germany

Tel: +49 176 62397500

Email: mjaeger@partner.eso.org

Source: ESO

Studying diffuse, warm gas in the outskirts of galaxies

An optical image of galaxy M82 with the ionized gas of hydrogen (Hα) shown in pink flowing out of the galaxy. 

Image Credit: NASA, ESA, The Hubble Heritage Team, (STScI/AURA)

The diffuse gas around galaxies is hard to detect, but shows properties which are quite different to the star-forming gas inside a galaxy. Scientists at MPA have used observations from the recent MaNGA survey to study how the ionized gas changes with distance from the center of the galaxy. They have demonstrated the usefulness of adding spectra from multiple galaxies in order to analyze the gas in the outskirts of galaxies. Their study shows that the brightness of the gas decreases, while its temperature increases the further the gas is located from the center of the galaxy. The differences between star-forming and circumgalactic gas also seem to correlate with the star-formation rate and stellar mass of the galaxies.

Understanding gas in and around galaxies is crucial to understanding star formation. The gas within a galaxy is the main ingredient for forming stars, and these stars, in turn, enrich the gas with heavy elements, or “metals”. Continuous star formation needs a constant supply of gas, and most likely this comes from a reservoir of gas surrounding the galaxy in its outskirts, or halo, called the circum-galactic medium (CGM). Additionally, enriched gas flows out of the galaxies through supernova explosions, galactic winds, active galactic nuclei, etc. (see Fig 1 for an example of gas outflows). By studying the gas in the CGM and near the disk-halo boundary we can better understand these regulatory processes, gas properties and flows. 

Gas in the halo is difficult to study because it is very faint and diffuse. Cold neutral gas can be seen by looking for neutral hydrogen (HI), and through HI surveys it is known that most galaxies have large reservoirs of gas surrounding the galaxies. Warm ionized gas with temperatures around 1000 K can be detected with optical emission lines and in the outskirts of galaxies this is called extra-planar, diffuse ionized gas (eDIG). Most previous work has been done with long exposures of individual nearby galaxies, including our own Milky Way. 

With optical spectroscopy, only a few handfuls of galaxies have been studied, as it is difficult to obtain exposures deep enough to detect and analyze the diffuse gas. These studies find that the eDIG has different properties compared to gas in star-forming regions. Both the eDIG and star-forming gas are ionized mostly by energy from massive OB stars. As these stars are located in the disk of the galaxy, many of the differences arise because the eDIG is farther away from the OB stars than the gas in star-forming regions. Some other differences are not so easy to explain and vary from galaxy to galaxy. In some galaxies an additional source of energy may be needed to explain the properties of the eDIG, such as turbulence or shocks in the gas, or hot evolved stars in the outskirts of galaxies. 

An example of one of the MaNGA galaxies. The left panel is an SDSS image with the MaNGA field of view overlaid.The middle panel shows a map of the brightness of the galaxy seen with MaNGA and the right panel shows a map of the ionized gas of hydrogen (Hα). The color bars are in logarithmic units. For an individual galaxy, the gas can barely be detected in the outskirts. Thus, for scientific analysis, spectra from many galaxies have to be added to increase the signal far enough above the noise level. © MPA. Hi-res image

With a new dataset from the survey Mapping Nearby Galaxies at APO (MaNGA), which is part of the Sloan Digital Sky Survey (SDSS) IV, a group of MPA scientists addressed these differences and questions about the eDIG. As an Integral Field Unit survey, MaNGA takes spectra at multiple spatial locations. The eDIG is faint and diffuse and in Fig 2 we show an example for the MaNGA observations of one particular galaxy. Adding multiple spectra taken at similar locations from similar edge-on, late-type galaxies, we can study the faint diffuse gas. 

The first year of MaNGA data includes a sample of 49 galaxies that are suitable for this study. We add the spectra from these 49 galaxies from 7 different locations off the disk of the galaxies to find how the eDIG varies with distance from the center of the galaxy. Our analysis shows that the brightness of the eDIG decreases logarithmically with distance and that most likely the temperature of the gas increases with distance from the center of the galaxies. 

For a more detailed analysis, e.g. to figure out which type of galaxies need an additional energy source and what type of source, we to split the sample by different properties of the galaxies, such as stellar mass or star formation. With the first year of data we split the full sample in half and find that in galaxies with a higher star formation rate, the eDIG is more similar to the star-forming gas inside the galaxies compared to low star-forming galaxies where the eDIG is markedly different. Moreover, galaxies with higher stellar mass have a steeper temperature gradient compared to those with lower stellar mass. In the future, with more data, we will be able to split the sample even further to better understand these questions.

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Author:

Jones, Amy

Postdoc

Phone: 2215

Email: ymamay@mpa-garching.mpg.de

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Original Publication

1. A. Jones, G. Kauffmann, R. D'Souza, D. Bizyaev, D. Law, L. Haffner, Y. Bahe, B. Andrews, M. Bershady, J. Brownstein, B. Cherinka, A.Diamond-Stanic, N. Drory, R. A. Riffel, S. F. Sanchez, D. Thomas, D. Wake, R. Yan, K. Zhang.    

SDSS IV MaNGA: Deep observations of extra-planar, diffuse ionized gas around late-type galaxies from stacked IFU spectra

2016, submitted to A&A

Source: Max Planck Institute for Astrophysics

Young Stellar System Caught in Act of Forming Close Multiples

ALMA image of the L1448 IRS3B system, with two young stars at the center and a third distant from them. Spiral structure in the dusty disk surrounding them indicates instability in the disk, astronomers said.  Credit: Bill Saxton, ALMA (ESO/NAOJ/NRAO), NRAO/AUI/NSF.

Combined ALMA and VLA image of L1448 IRS3B system.

Credit: Bill Saxton, ALMA (ESO/NAOJ/NRAO), NRAO/AUI/NSF.

Artist's conception of how the triple-star system develops.

Left, disk of material fragments into separate protostars.

Right, the resulting stellar system.

Credit: Bill Saxton, NRAO/AUI/NSF.

For the first time, astronomers have seen a dusty disk of material around a young star fragmenting into a multiple-star system. Scientists had suspected such a process, caused by gravitational instability, was at work, but new observations with the Atacama Large Millimeter/submillimeter Array (ALMA) and the Karl G. Jansky Very Large Array (VLA) revealed the process in action.

"This new work directly supports the conclusion that there are two mechanisms that produce multiple star systems -- fragmentation of circumstellar disks, such as we see here, and fragmentation of the larger cloud of gas and dust from which young stars are formed," said John Tobin, of the University of Oklahoma and Leiden Observatory in the Netherlands.

Stars form in giant clouds of gas and dust, when the tenuous material in the clouds collapses gravitationally into denser cores that begin to draw additional material inward. The infalling material forms a rotating disk around the young star. Eventually, the young star gathers enough mass to create the temperatures and pressures at its center that will trigger thermonuclear reactions.

Previous studies had indicated that multiple star systems tend to have companion stars either relatively close, within about 500 times the Earth-Sun distance, or significantly farther apart, more than 1,000 times that distance. Astronomers concluded that the differences in distance result from different formation mechanisms. The more widely-separated systems, they said, are formed when the larger cloud fragments through turbulence, and recent observations have supported that idea.

The closer systems were thought to result from fragmentation of the smaller disk surrounding a young protostar, but that conclusion was based principally on the relative proximity of the companion stars.

"Now, we've seen this disk fragmentation at work," Tobin said.

Tobin, Kaitlin Kratter of the University of Arizona, and their colleagues used ALMA and the VLA to study a young triple-star system called L1448 IRS3B, located in a cloud of gas in the constellation Perseus, some 750 light-years from Earth. The most central of the young stars is separated from the other two by 61 and 183 times the Earth-Sun distance. All three are surrounded by a disk of material that ALMA revealed to have spiral structure, a feature that, the astronomers said, indicates instability in the disk.

"This whole system probably is less than 150,000 years old." Kratter said. "Our analysis indicates that the disk is unstable, and the most widely separated of the three protostars may have formed only in the past 10,000 to 20,000 years," she added.

The L1448 IRS3B system, the astronomers conclude, provides direct observational evidence that fragmentation in the disk can produce young multiple-star systems very early in their development.

"We now expect to find other examples of this process and hope to learn just how much it contributes to the population of multiple stars," Tobin said.

The scientists presented their findings in the October 27 edition of the journal Nature.

ALMA is a partnership of ESO (representing its member states), NSF (USA) and NINS (Japan), together with NRC (Canada), NSC and ASIAA (Taiwan), and KASI (Republic of South Korea), in cooperation with the Republic of Chile. The Joint ALMA Observatory is operated by ESO, AUI/NRAO and NAOJ.

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

Media Contact: 

Dave Finley, Public Information Officer
(575) 835-7302
dfinley@nrao.edu

Source: National Radio Astronomy Observatory (NRAO)