News

To flare or not to flare: The riddle of galactic thin–thick disk solved

24 April 2015. A long-standing puzzle regarding the nature of disk galaxies has finally been solved by a team of astronomers led by Ivan Minchev from the Leibniz Institute for Astrophysics Potsdam ...

We were able to show for the first time that galactic thick disks are not composed only of old stars but must also contain young stars at larger distances from the galactic centre”, explains Minchev. “The flaring seen in groups of stars with the same age is caused mostly by the bombardment of small satellite galaxies. These cosmological car crashes pummel the young disk and cause it to swell and flare.“

To arrive at this new result, the team ran numerical simulations on massive super computers and examined the structure of their simulated galaxies. The scientists grouped stars by common age and looked at where they were located. What they found was that stars of a given age group constituted a disk with flared edges, much like the mouth of a trumpet. This flaring is unavoidable, being caused when the main galaxy collides with smaller galaxies – a generic feature of how scientists believe galaxies form. Since the oldest stars formed in the inner region of the galaxy, for them this flaring occurs closer to the centre, while for the younger stars it occurs at the periphery of the galaxy. When put together, the combination of flaring from all the stars produces the elusive thick disk, as observed.

One of the most fascinating aspects of galaxies is that their stars can be separated into two components: a fluffy thick disk that enshrouds a thin disk. Until now the understanding has been that stars in the thick disk were the oldest. In observations of the Milky Way the oldest stars are found to be closer to the centre, while younger stars are more extended. Scientists agree that this separation is likely due to an “inside-out” formation scenario, wherein the Milky Way forms stars first in its center and later in its outer region, much like how cities grow radially from a medieval center to modern suburbs. Observing the structure of the Milky Way is tricky, since we are located within its disk, roughly half way from the centre. Instead, astronomers have to rely on the stars that surround us and build a model from this limited perspective. Nevertheless, if the Milky Way were similar to other galaxies and its thick disk were composed only of old, centrally concentrated stars, then one would naively expect its thick disk to be short. But in other galaxies the thick disks are observed to be as extended as the galaxies themselves. Minchev’s results resolve this contradiction by requiring that thick disk stars become younger in the disk outskirts.

“With our new understanding of the formation of, and interplay between, galactic thin and thick disks, we have moved much closer to solving one of the most fundamental problems of Galactic astrophysics.”, concludes Ivan Minchev. “Our predictions will soon be tested with data from the Gaia space mission and using high precision instruments, such as MUSE on the Very Large Telescope.”

On the formation of galactic thick disks, Minchev et al. 2015, ApJL, 804, 1.

 

Science contact: Dr. Ivan Minchev,+49 331 7499-454, iminchev@aip.de

Media contact: Dr. Janine Fohlmeister, +49 331 7499-383, 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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First Light for PEPSI

Spectrum of HD 82106 in comparison to other AIP observatories.

First Light for PEPSI

22 April 2015. The Potsdam Echelle Polarimetric and Spectroscopic Instrument (PEPSI) has received its first celestial light through the Large Binocular Telescope (LBT). Astronomers from the Leibniz...

On April 1st, the 2 x 8.4m mirrors of LBT, effectively an 11.8m telescope, were turned to the K3 dwarf star HD 82106, and PEPSI received its first celestial photons through the world’s largest telescope. The instrument splits the stellar light into a spectrum with a wavelength resolution otherwise only obtainable in solar physics. The commissioning team of four AIP astronomers on the 3200m Mt. Graham in Arizona was preceded by a team of five who prepared the instrument for this event.

The star was only the first in a series of commissioning targets that test the instrument’s resolving powers at different wavelengths. Switching between resolution modes or between wavelength settings takes less than a minute and can be done any time. PEPSI is the only instrument that enables astronomers to point to bright stars as well as to faint quasars during the same night.

 

 

 

Caption: Star spectrum of HD 82106 compared to the Sun and Arcturus (detail).


Science Contact and Principal Investigator: Prof. Dr. Klaus G. Strassmeier

Project scientists: Dr. Ilya Ilyin and Dr. Michael Weber

Media contact: Dr. Janine Fohlmeister, +49 331 7499 383

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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Stars with the chemical clock on hold

Artist impression of red giant stars in the Milky Way. (credit: AIP/ J. Fohlmeister)

Stars with the chemical clock on hold

10 April 2015. An international team of astrophysicists, led by Cristina Chiappini from the Leibniz Institute for Astrophysics Potsdam, has discovered a group of red giant stars for which the ‘ch...

The term ‘Galactic Archaeology’ was coined to describe the fact that the Milky Way’s history is encoded not only in the quantities of various chemical elements seen in the spectra of stellar atmospheres (abundances), but also in stellar motions. One of the pillars of Galactic Archaeology is the use of stellar abundance ratios as an indirect estimator of age. While massive stars that explode as core-collapse supernovae mainly enrich the interstellar medium with oxygen and other ‘alpha elements’ on short timescales, Type Ia supernovae produce the bulk of iron and die after a longer time. The time delay between interstellar medium enrichment in alpha elements and iron can then be used as a chemical clock. Indeed, the chemical clock has been shown to work for many stars.

However, the authors of the new study demonstrate that alpha/iron enhancement is no guarantee that a star is in fact old. It has only recently become possible to determine precise ages for these stars, thanks to asteroseismology. This method measures pulsation frequencies, providing additional information about the age of stars. The group of stars studied appears to be relatively young, despite being enriched with alpha elements with respect to the Sun. Interestingly, these stars were found to be more abundant towards the inner Galactic disc regions where the interplay between the bar and spiral arms may lead to a more complex chemical enrichment scenario.

“Although there were similar stars in previous surveys, they were not identified as such and only very few of them. This may explain why these stars have received little attention so far,” mused Friedrich Anders, Chiappini’s co-author.

“Future observations will provide more clues as to the origin of these stars and the complex chemical evolution of the Milky Way,” concluded Cristina Chiappini.

The new CoRoT-APOGEE (CoRoGEE) sample is the result of collaboration between APOGEE (a high-resolution infrared survey) ‒ part of the Sloan Digital Sky Survey III (SDSSIII) ‒ and the CoRoT red giant working group. This collaboration enabled hundreds of red giant stars to be followed up spectroscopically, providing seismic information in the CoRoT fields. At present, only CoRoGEE can explore the inner-disc regions and determine the age of its field stars.

Publication: Young [ α /Fe]-enhanced stars discovered by CoRoT and APOGEE: What is their origin?, Chiappini et al. 2015, A&A, 576, L12

 

Caption: Location of the red giants studied by CoRoGEE in the Milky Way. The red stars show the ones for which the chemical clock does not work. (Credit: F. Anders)

Science contact: Dr. Cristina Chiappini, cristina.chiappini@aip.de, +49 331 7499-454

Media contact: Dr. Janine Fohlmeister, presse@aip.de, +49 331 7499-383

 

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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Funding success for innoFSPEC

27 March 2015 The Federal Ministry of Education and Research will fund the Centre for Innovation Competence innoFSPEC for another five years. Federal Minister Johanna Wanka praises the scientific...

innoFSPEC is a collaborative project between the Leibniz Institute for Astrophysics Potsdam (AIP) and the chair of Physical Chemistry at the University of Potsdam. The centre engages in basic research and develops innovative solutions for fibre-based sensors and multichannel spectroscopy.

In doing so, innoFSPEC combines the skills of new chemical analysis methods with high-performance multi-object and multi-channel spectroscopy. The centre's scientific and innovative approach follows the fast-paced developments in photonics. innoFSPEC received its first grant as a ZIK in 2008 through the BMBF funding programme "Zentrum für Innovationskompetenz: Exzellenz schaffen - Talente sichern".

The BMBF supports the establishment of outstanding international research at universities and research institutions located in the states of former East Germany. Key aspects in all ZIKs are excellent research on a highly international and competitive level as well as their ability to successfully transfer the results into the industry sector. The centres are also expected to exert a strong force of attraction upon young researchers.

Scientific contact AIP: Prof. Dr. Martin M. Roth, mmroth@aip.de, 0331 7499 313

Press contact: Dr. Janine Fohlmeister, presse@aip.de, 0331 7499 383

Further information: www.innofspec.de

Press release BMBF

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Solar eclipse seen by the LOFAR RadioTelescope

23 March 2015. The European radio interferometer LOFAR succeeded in taking unique pictures of the solar eclipse on March 20th as it is not possible by eye.

In the movie the path of the Moon’s shadow over the Sun is seen. The video shows the Sun at a frequency range of 115-175 MHz, which corresponds to a wavelength of about two meters. The radio emission originates from the Sun's outer atmosphere, the corona. This radiation is enhanced over active regions, where Sunspots are seen and strong magnetic
fields dominate. These regions can be the source of solar eruptions. The eye-catching bright spot in the upper left of the picture marks such a region of high activity and is visible as a dark Sunspot at optical wavelengths.

 

Gottfried Mann from the Leibniz Institute for Astrophysics Potsdam (AIP) coordinates the solar observations with the LOw Frequency ARray (LOFAR). The solar eclipse was observed to gain specific information on the structure of the solar atmosphere. Christian Vocks, PI of the observations on March 20,  explains: „Radio waves pass without problem through clouds in the Earth’s atmosphere, so that observations do not depend on weather.“ Still, the image of the Sun appears nebulous because: „Observations of the Sun through the Earth’s atmosphere with a radio telescope suffer from the same effect like if you try to take pictures from the bottom of a swimming pool.“


Click on picture above to start video.

The now published movie is based on data gathered with the International LOFAR telescope (ILT). The Leibniz Institute for Astrophysics Potsdam (AIP) operates one of LOFAR's stations in Potsdam Bornim.

 

LOFAR is the Low Frequency Array designed and constructed by ASTRON. It has facilities in several countries, that are owned by various parties (each with their own funding sources), and that are collectively operated by the ILT foundation under a joint scientific policy. LOFAR is well suited for a wide variety of scientific topics, from the early universe to Earth's space environment

 

LINK LOFAR

 

Science contact:

Apl. Prof. Dr. Gottfried Mann, gmann@aip.de, +49 331 7499 292

Dr. Christian Vocks, cvocks@aip.de, +49 331 7499 327

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