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Cosmic Beacons Reveal the Milky Way's Ancient Core

The plane of our Galaxy as seen in infrared light from the WISE satellite. (Credit: NOAO/AURA/NSF/AIP/A. Kunder)

Cosmic Beacons Reveal the Milky Way's Ancient Core

22 April 2016. An international team of astronomers led by Dr. Andrea Kunder of the Leibniz Institute for Astrophysics Potsdam (AIP) in Germany and Dr. R. Michael Rich of UCLA has discovered that t...

For the first time the team kinematically disentangled this ancient component from the stellar population that currently dominates the mass of the central Galaxy. The astronomers used the AAOmega spectrograph on the Anglo Australian Telescope near Siding Spring, Australia, and focussed on a well-known and ancient class of stars, called RR Lyrae variables. These stars pulsate in brightness roughly once a day, which make them more challenging to study than their static counterparts, but they have the advantage of being "standard candles". RR Lyrae stars allow exact distance estimations and are found only in stellar populations more than 10 billion years old, for example, in ancient halo globular clusters. The velocities of hundreds of stars were simultaneously recorded toward the constellation of Sagittarius over an area of the sky larger than the full moon. The team therefore was able to use the age stamp on the stars to explore the conditions in the central part of our Milky Way when it was formed.

Just as London and Paris are built on more ancient Roman or even older remains, our Milky Way galaxy also has multiple generations of stars that span the time from its formation to the present.  Since heavy elements, referred to by astronomers as “metals”, are brewed in stars, subsequent stellar generations become more and more metal-rich.  Therefore, the most ancient components of our Milky Way are expected to be metal-poor stars. Most of our Galaxy's central regions are dominated by metal-rich stars, meaning that they have approximately the same metal content as our Sun, and are arrayed in an American football-shaped structure called the "bar". These stars in the bar were found to orbit in roughly the same direction around the Galactic Centre. Hydrogen gas in the Milky Way also follows this rotation. Hence it was widely believed that all stars in the centre would rotate in this way. But to the astronomers’ astonishment, the RR Lyrae stars do not follow football-shaped orbits, but have large random motions more consistent with their having formed at a great distance from the centre of the Milky Way. "We expected to find that these stars rotate just like the rest of the bar" states lead investigator Kunder. Coauthor Juntai Shen of the Shanghai Astronomical Observatory adds, "They account for only one percent of the total mass of the bar, but this even more ancient population of stars appears to have a completely different origin than other stars there, consistent with having been one of the first parts of the Milky Way to form."

The RR Lyrae stars are moving targets - their pulsations result in changes in their apparent velocity over the course of a day. The team accounted for this, and was able to show that the velocity dispersion or random motion of the RR Lyrae star population was very high relative to the other stars in the Milky Way's center. The next steps will be to measure the exact metal content of the RR Lyrae population, which gives additional clues to the history of the stars, and enhance by three or four times the number of stars studied, that presently stands at almost 1000.

 

Scientific publication: Andrea Kunder et al.: Before the Bar: Kinematic Detection of A Spheroidal Metal-Poor Bulge Component, The Astrophysical Journal Letters, Volume 821, Number 2.
http://iopscience.iop.org/article/10.3847/2041-8205/821/2/L25/meta

 

Figure caption: The plane of our Galaxy as seen in infrared light from the WISE satellite.  The bulge is a distinct component in the central part of the Galaxy, and rotates cylindrically.  An ancient population, which does not exhibit cylindrical rotation, has been detected in the inner Milky Way. This population is estimated to be 1% of the mass of the bulge, and is likely to have been one of the first parts of the Milky Way to form. (Credit: NOAO/AURA/NSF/AIP/A. Kunder)

 

Science Contact: Dr. Andrea Kunder, +49 331 7499-646, akunder@aip.de
Media Contact: Kerstin Mork, +49 331 7499-803, presse@aip.de

The key topics of the Leibniz Institute for Astrophysics Potsdam (AIP) are cosmic magnetic fields and extragalactic astrophysics. A considerable part of the institute's efforts aim at the development of research technology in the fields of spectroscopy, robotic telescopes, and e-science. The AIP is the successor of the Berlin Observatory founded in 1700 and of the Astrophysical Observatory of Potsdam founded in 1874. The latter was the world's first observatory to emphasize explicitly the research area of astrophysics. Since 1992 the AIP is a member of the Leibniz Association.

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Third CALIFA data release: an inspiration to be curious about galaxies

11 April 2016. The Calar Alto Legacy Integral Field Area Survey (CALIFA) has released all of the data assembled over six years of work. The data of more than 600 galaxies are accessible for anyone ...

CALIFA provides a unique way to learn about the evolution of galaxies. While we ourselves live in a specific galaxy, there are many more siblings of the Milky Way out there. A favourite analogy of the project Principal Investigator, Dr. Sebastian Sanchez (UNAM, Mexiko): “A social scientist would naturally learn much more about a specific human by studying her environment, her family and other social relations. Exactly in the same way can we astronomers support the understanding of our cosmic home, the Milky Way, by studying its siblings in the skies. Studying galaxies to learn about their evolution is a fascinating subject, because - just as humans - they come in a wide variety of appearances shaped by their specific evolutionary histories.”

CALIFA is the first project to apply the technique of integral field spectroscopy to a sample that represents all galaxies in the Local Universe, providing a panoramic view of galaxy evolution. Integral field spectroscopy is a technique that allows to determine the properties of galaxies at many different places of each galaxy, i.e. in a spatially resolved way. The CALIFA sample on the other hand was specifically selected to be representative of galaxies in the Local Universe. “We knew that some galaxy properties change systematically. But seeing this in such detail and for so many properties for which this was previously not possible is new and exciting. It provides new avenues to study galaxies and understand why exactly they turn out to be as they are” says Dr. Jakob Walcher from the Leibniz Institute for Astrophysics Potsdam (AIP), the Project Scientist of CALIFA. Data were obtained with the AIP-built integral-field spectrograph PMAS/PPak at the Calar Alto Observatory.

“As a publicly funded project we see it as our duty to make the data available to the public. This also allows anyone interested to reproduce and work with our results” adds Dr. Stefano Zibetti (INAF Arcetri, Italy), Quality Control responsible of CALIFA, and therefore fundamentally involved in making sure that the data meet all quality criteria and will be truly useful to the international community of scientists. Ruben Garcia-Benito (IAA, Spain), responsible for running many of the fundamental software pieces that turned observations from the telescope into ready-to-release data adds: "We hope that the nice images we produce can inspire even more people to be curious about the Universe in general and galaxies in particular.”

Caption: The figure shows how galaxy properties vary systematically with their stellar mass (i.e. the number of stars they contain) and the star formation rate (i.e. the number of stars they are newly making every year at the present time). It illustrates the power of CALIFA data to help understand the evolution of galaxies.

Find the 3rd CALIFA data release online.

 

Science contact: Dr. Jakob Walcher, jwalcher@aip.de

Media contact: Kerstin Mork, +49 331 7499-803, presse@aip.de

 

The key topics of the Leibniz Institute for Astrophysics Potsdam (AIP) are cosmic magnetic fields and extragalactic astrophysics. A considerable part of the institute's efforts aim at the development of research technology in the fields of spectroscopy, robotic telescopes, and e-science. The AIP is the successor of the Berlin Observatory founded in 1700 and of the Astrophysical Observatory of Potsdam founded in 1874. The latter was the world's first observatory to emphasize explicitly the research area of astrophysics. Since 1992 the AIP is a member of the Leibniz Association.

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The Missing Brown Dwarfs

8 April 2016. When re-analysing catalogued and updated observational data of brown dwarfs in the solar neighbourhood, astronomers from Potsdam have found that a significant number of nearby brown d...

Brown dwarfs are objects that are too large to be called planets, yet too small to be stars. Having a mass of only less than seven per cent of the mass of the Sun, they are unable to create sufficient pressure and heat in their interiors to ignite hydrogen-to-helium fusion, a fundamental physical mechanism by which stars generate radiation. In this sense brown dwarf are “failed stars”. It is therefore important to know how many brown dwarfs really exist in different regions of the sky in order to achieve a better understanding of star formation and of the motion of stars in the Milky Way.

Gabriel Bihain and Ralf-Dieter Scholz have taken a careful look at the distribution of nearby known brown dwarfs from a point of view that was not looked at before. To their surprise they discovered a significant asymmetry in the spatial configuration, strongly deviating from the known distribution of stars.

„I projected the nearby brown dwarfs onto the galactic plane and suddenly realized: half of the sky is practically empty! We absolutely didn’t expect this, as we have been looking at an environment that should be homogeneous.“, Gabriel Bihain explained. Seen from Earth, the empty region overlaps with a large part of the northern sky.

The scientists concluded that there should be many more brown dwarfs in the solar neighbourhood that are yet to be discovered and that will fill the observed gap. If they are right, this would mean that star formation fails significantly more often than previously thought, producing one brown dwarf for every four stars. In any case, it appears, the established picture of the solar neighbourhood and of its brown dwarf population will have to be rethought.

„It is quite possible that not only brown dwarfs are still hiding in the observational data, but also other objects with even smaller, planetary-like masses. So it is definitely worth it to take another deep look at both existing and future data.”, Ralf-Dieter Scholz concluded.

Picture top left: Possible manifestations of brown dwarfs (artist’s impression). As brown dwarfs are nearly invisible in the optical light and mostly emit radiation in the IR regime, they exhibit different colors in that range. (Credit: AIP/J. Fohlmeister)

Additional illustration

 

Scientific publication: G. Bihain and R.-D. Scholz, A non-uniform distribution of the nearest brown dwarfs, Astronomy and Astrophysics, 589, A26 (2016).

 

Science Contact: Dr. Gabriel Bihain, +49 331 7499-452, gbihain@aip.de

Press Contact: Kerstin Mork, +49 331 7499-803, presse@aip.de

 

The key topics of the Leibniz Institute for Astrophysics Potsdam (AIP) are cosmic magnetic fields and extragalactic astrophysics. A considerable part of the institute's efforts aim at the development of research technology in the fields of spectroscopy, robotic telescopes, and e-science. The AIP is the successor of the Berlin Observatory founded in 1700 and of the Astrophysical Observatory of Potsdam founded in 1874. The latter was the world's first observatory to emphasize explicitly the research area of astrophysics. Since 1992 the AIP is a member of the Leibniz Association.

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The 13th AIP Thinkshop on Cosmology

Cosmic Flows (Credit: AIP)

The 13th AIP Thinkshop on Cosmology

29 March 2016. The Leibniz Institute for Astrophysics Potsdam (AIP) organizes in collaboration with the University of Innsbruck the 13th Thinkshop under the title "Near Field Cosmology". From March...

Observational cosmology has traditionally focused on the outskirts of the visible universe, with an ever increasing appetite to reach deeper into space and backwards in time. Recently, cosmologists have realized that some treasures are buried much closer to home. In the last decade, cosmologists have become archaeologists as they search for "fossils" and clues in present-day observations of nearby objects in order to better understand the cosmological formation history, establishing the new research area of Near Field Cosmology.

The better we know our cosmic vicinity the better we understand the universe as a whole. Brent Tully (Hawaii), Helene Courtois (Lyon) and Jenny Sorce (AIP) will for the first time present at this meeting the CosmicFlows3 catalogue with exact positions and velocities of almost 20,000 galaxies in the cosmic neighbourhood of our Milky Way. These new data are a milestone in the understanding of our cosmic "neighbourhood" up to a distance of several 100 million light years.

 

Science Contact: Dr. Stefan Gottloeber, +49 151 58323983, sgottloeber@aip.de

Media Contact: Kerstin Mork , +49 331 7499 803, presse@aip.de

 

For further information and a detailed schedule see:  http://transidee-conference.uibk.ac.at/NFCosmology2016

 

The key topics of the Leibniz Institute for Astrophysics Potsdam (AIP) are cosmic magnetic fields and extragalactic astrophysics. A considerable part of the institute's efforts aim at the development of research technology in the fields of spectroscopy, robotic telescopes, and e-science. The AIP is the successor of the Berlin Observatory founded in 1700 and of the Astrophysical Observatory of Potsdam founded in 1874. The latter was the world's first observatory to emphasize explicitly the research area of astrophysics. Since 1992 the AIP is a member of the Leibniz Association.

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HIRES: The world’s biggest telescope gets the world’s best instrumentation

Illustration of the HIRES instrument and its adressed scientific goals. (Credit: HIRES consortium)

HIRES: The world’s biggest telescope gets the world’s best instrumentation

23 March 2016. Scientists and engineers have begun mapping out the detailed specifications for the High Resolution Spectrograph HIRES that will be part of the instrument suite on ESO’s forthcomin...

High resolution spectroscopy simultaneously covering ultraviolet, optical and infrared wavelengths is new in astronomical research and will open new windows in our understanding of several hot topics of modern stellar and extragalactic astrophysics. With a spectral resolution of R=100,000 and a wavelength coverage from 350nm to 2500nm, E-ELT HIRES will be an instrument capable of providing unique breakthroughs in the fields of habitable exoplanets, star and planet formation, physics and evolution of stars and galaxies, and cosmology and fundamental physics. Among the prime science goals of HIRES will be the detection of biosignatures from planets around other Suns and contribute to the search for extraterrestrial life. E-ELT HIRES also offers the possibility of paradigm-changing contributions to fundamental physics due to the precision afforded by Laser Frequency Comb calibrated high-fidelity spectroscopy.

The HIRES-consortium is among the largest ever to collaborate in the production of astronomical instruments, illustrating the multinational efforts involved in making these spectrographs. Instruments like HIRES or MOS type feature in the essential toolbox of every modern telescope — these world-leading examples will make the most of the enormous light-gathering power of the E-ELT’s 39-metre main mirror, giving them a performance second to none.

The HIRES Consortium consists of 12 countries (Brazil, Chile, Denmark, France, Germany, Italy, Poland, Portugal, Spain, Sweden, Switzerland, United Kingdom).  The Italian National Institute for Astrophysics (INAF) will be the lead technical Institute within the Consortium. Germany is represented by the Leibniz-Institute for Astrophysics Potsdam (AIP) and Prof. Klaus G. Strassmeier is the coordinator and Co-I of HIRES and a member of its Board, Michael Weber is deputy instrument scientist. The German contributions to HIRES will include the entire Stokes polarimeter and its focal station (Potsdam), the blue-ultraviolet component of the visible spectrograph (Potsdam, Heidelberg, Göttingen), the calibration environment (Göttingen, Tautenburg), and the fibre link (Potsdam, Heidelberg).

The German contributions to HIRES are supported by the BMBF-program „Erdgebundene Astrophysik und Astroteilchenphysik“.

Science contacts: Prof. Dr. Klaus G. Strassmeier, kstrassmeier@aip.de and Dr. Michael Weber, mweber@aip.de

Media contact: Dr. Janine Fohlmeister, presse@aip.de, +49 331-7499 802

The key topics of the Leibniz Institute for Astrophysics Potsdam (AIP) are cosmic magnetic fields and extragalactic astrophysics. A considerable part of the institute's efforts aim at the development of research technology in the fields of spectroscopy, robotic telescopes, and e-science. The AIP is the successor of the Berlin Observatory founded in 1700 and of the Astrophysical Observatory of Potsdam founded in 1874. The latter was the world's first observatory to emphasize explicitly the research area of astrophysics. Since 1992 the AIP is a member of the Leibniz Association.

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