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Spinning rugby balls: The rotation of the most massive galaxies

Map of the measured mean stellar velocity of a galaxy: Blue colour means that stars in this part of the galaxy move towards us and red colours away from us. Credit: MUSE/D. Krajnovic

Spinning rugby balls: The rotation of the most massive galaxies

By targeting the most massive galaxies in our universe, astronomers have studied how their stars move. The results are surprising: while half of them spin around their short axis as expected, the o...

Surveying the extremes of the galaxy population

Measuring the way stars move within galaxies is a very powerful way of learning about the internal structure of galaxies, especially properties such as their three-dimensional shape and, ultimately, what their gravitational potential is like.

To study the largest and most massive galaxies, a science team led by Davor Krajnovic from the Leibniz Institute for Astrophysics Potsdam (AIP) selected a sample of some of the brightest galaxies up to a distance of 800 million light years. These live in large ensembles of galaxies, within some of the most densely populated regions of our Universe, such as the Shapley Supercluster. They are also very bright and rare. The most massive galaxies are about one hundred times more massive than our own galaxy the Milky Way, which itself already has a stellar mass of 60 billion suns. They also have almost no gas, most of their stars are very old (at least 10 billion years) and do not form stars anymore.

Unfortunately, these galaxies are too far from us to be resolved into individual stars and their motions. One can only look at the average motions of stars within certain regions. “This is what integral-field spectrographs are good at”, explains Davor Krajnović. „We observed these galaxies with MUSE, the wonderful integral-field spectrograph on the ESO's Very Large Telescope on Cerro Paranal in Chile. Massive galaxies can have all sorts of kinematics, some spin like frisbees, but most have no specific sense of rotation. We observed the most massive galaxies and found them to be different from other galaxies.”

From discs to rugby balls

The majority of intermediate-mass galaxies shows very regular stellar motions, as one would expect from discs like our Milky Way. In such galaxies, the sense of rotation is well defined around the shortaxis of the object; the angular momentum is aligned with the minor axis of an oblate spheroid.

“We knew that about only 15% of the intermediate mass galaxies have irregular kinematics or even don’t show much rotation at all”, says Krajnović.“For such galaxies, the sense of rotation is often not aligned with any of the symmetry axes of the galaxy, and these galaxies are of nearly spherical shape, or are elongated resembling rugby balls. Some of them have an interesting alignment and rotate around the long axis of the galaxy. Only a few cases of these were known.”

In the new study published in the Monthly Notices of the Royal Astronomical Society, the authors showed that these galactic “spinning rugby balls” are much more common than thought previously if one looks at the extremely massive galaxies, the high-mass end of the galaxy population.

The result is interesting as it points to a very specific formation scenario for these galactic giants. Numerical simulations indicate that rotation along the long axis is indicative for a merger of two massive galaxies with similar size (and mass) when they are on special trajectories: sort of a head-on collision in space.

Such galaxy collisions are violent events that completely reshape the internal structures of the progenitor galaxies. The remnant galaxies resemble spinning rugby balls. Stellar orbits also become much more complex, resulting in kinematics where the simple ordered motion is substituted with complex streaming around any of the three axes of a spheroid. The most massive galaxies are the end points of galaxy formation, and deservedly turn out to be the most complex stellar systems. This study helps us unveil the mystery of how the most massive galactic systems in the Universe come into existence.

 

The upper panels show maps of the measured mean stellar velocity of two example galaxies: Blue colour means that stars in this part of the galaxy move towards us and red colours away from us. The type of rotation for the galaxy on the left is typical for galaxies. The majority of galaxies rotate like this. The rotation around the long axes of the galaxy on the right is unusual, and applies only to a small fraction of galaxies. This fraction increases as galaxies become more massive. Credit: MUSE/D. Krajnovic

 

Publication

Davor Krajnović et al. Climbing to the top of the galactic mass ladder: evidence for frequent prolate-like rotation among the most massive galaxies, Monthly Notices of the Royal Astronomical Society (2018).  MNRAS Publication

arXiv: https://arxiv.org/abs/1802.02591

Scientific contact at AIP

Dr. Davor Krajnović, 0331-7499 237, dkrajnovic@aip.de

Media contact

Franziska Gräfe, 0331-7499 803, presse@aip.de

 

The key areas of research at 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. The AIP has been a member of the Leibniz Association since 1992.

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Sun in sight: Tailored solution for collaborative research

Three-dimensional flow field on the sun on September 26, 2016, reconstructed from GREGOR data. Credit: Carsten Denker/AIP

Sun in sight: Tailored solution for collaborative research

Since 2014, Europe's largest solar telescope GREGOR has been used for scientific measurements and has collected large amounts of very complex, multidimensional data during this time. To make these ...

With the GREGOR telescope astronomers of the AIP study active dynamic processes on the Sun with high spatial, temporal and spectral resolution. In terms of observations and data acquisition, they face particular challenges arising from various factors: Turbulence in the Earth's atmosphere affects the image quality, small solar structures develop on short time scales of a few seconds to minutes, and large-format detectors generate very large amounts of data.

"With the powerful instruments of the GREGOR telescope we are able to detect even the smallest structures on the sun's surface and provide time series of high-resolution images every 10 to 20 seconds," says Prof. Carsten Denker, head of the working group Optical Solar Physics at the AIP. "A reconstructed image every 20 seconds is based on a few hundred individual image frames. That's about 200,000 images or 4 terabytes per observation day."

The large number and high-resolution of images and spectra as well as the required computational effort in the post-processing require extensive and efficient structures for storage and archiving. In order to make the GREGOR data optimally usable and accessible, a dedicated CRE has now been implemented at AIP. This infrastructure served initially as a central data hub within the GREGOR consortium, but is now open to all interested scientists. It provides data space and access, computational resources and customized tools for analysis and processing. Collaborators have also the option to publish selected and curated data for the solar community via the CRE.

In order to make research data available to as many scientists as possible or even to the interested general public, the open access paradigm has gained increased importance in recent years. The newly developed CRE for GREGOR data also builds on this concept and is specifically tailored toward the requirements of the high-resolution solar physics community. In the now published article, AIP scientists around Prof. Carsten Denker give an overview of the GREGOR data –from the photons arriving at the detector to the final data products. In addition, they describe the developed approach for the systematic processing, analysis, management and archiving of these data.

The development of research technology and e-infrastructure is a strategic goal of AIP. In close collaboration between the two research areas of E-Science and Solar Physics, a tailor-made solution was developed for the data-specific challenges of high-resolution solar observations obtained with ground-based solar telescopes such as GREGOR.

 

GREGOR consortium

Kiepenheuer Institute for Solar Physics, Freiburg

Leibniz Institute for Astrophysics Potsdam (AIP)

Max Planck Institute for Solar System Research, Göttingen

Instituto de Astrofísica de Canarias, Canary Islands

 

Further information

Publication: https://doi.org/10.3847/1538-4365/aab773

Solar telescope GREGOR: GREGOR

Collaborative Research Environment (CRE): gregor.aip.de

 

Scientific contact at AIP

Apl. Prof. Dr. Carsten Denker, +49 331-7499 297, cdenker@aip.de

 

Media contact

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

 

The key areas of research at 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. The AIP has been a member of the Leibniz Association since 1992.

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May 17 | Starry Night

Artistic representation of high speed jets from supermassive black holes. Credit: ESA/Hubble, L. Calçada (ESO)

May 17 | Starry Night

The Leibniz Institute for Astrophysics Potsdam (AIP) invites to the next Starry Night in Babelsberg on Thursday, May 17, 2018, starting at 7:15 pm with a public lecture of Sabine Thater on "Superma...

Milky Way, Andromeda galaxy, magellanic clouds: If you ask about galaxies, most people think of galaxies similar to our Milky Way with beautiful spiral arms. In fact, galaxies have a variety of appearances and properties: There are elliptical galaxies, spiral galaxies, massive galaxies, dwarf galaxies - just to name a few.

But they have one thing in common: most galaxies harbor a so-called "supermassive black hole" in their center. Black holes are among the most mysterious entities in our universe. It is not surprising that they often play a major role in science fiction novels: objects that are so massive that even light can no longer escape their attraction. Until very recently, the world doubted its very existence. Meanwhile, however, black holes and their big brothers, the "supermassive" black holes, are firmly integrated into research.

In this talk, we'll take you on a journey to the nearest galaxies and learn how to find a ‚dark‘ supermassive black hole, how it interacts with its parent galaxy, and what we can learn from exploring supermassive black holes.

 

After the talk, we offer a tour over the AIP campus and – if the sight is clear – an observation with one of our historical reflecting telescopes.

We look forward to your visit!

Free entry, no previous registration necessary.

Location: AIP, An der Sternwarte 16, 14482 Potsdam

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Off to space: Potsdam Science Day on May 5th

Under the motto "Research. Discover. Participate." the Potsdam Science Day will take place for the sixth time on Saturday, May 5. More than 40 universities and research institutions in the region p...

From 1 to 8 pm, the participating institutions will give exciting insights into their daily work, show spectacular experiments and present innovative projects that will change the world of tomorrow. The AIP is also represented with two program items: At the information booth (Haus 28, Nordfoyer), visitors of all ages can, among other things, make star maps, travel virtually to space or to observatories around the world and discover the prototype of the STIX X-ray telescope.

At 3 pm, Alexander Warmuth speaks about the instrument and the mission for which it was developed. In the lecture titled "Solar Orbiter - The Sun close up" the listeners will learn more about our home star and how we examine it.

Admission is free for all visitors.

From 1 to 8 pm the participating institutions will give exciting insights into their daily work, show spectacular experiments and present innovative projects that will change the world of tomorrow. The AIP is also represented with two program items: At the information booth (Haus 28, Nordfoyer), visitors can, among other things, make star maps, travel virtually to space or to observatories around the world and observe the prototype of the STIX X-ray telescope up close.The instrument and mission for which it was developed speaks at 3:00 pm Alexander Warmuth. In the lecture with the title "Solar Orbiter - The Sun close up" the listeners will learn more about our home star and how we examine it.

Admission is free for all visitors.

The website of the Potsdam Science Day with the complete program:
www.ptdw.de

 

The key areas of research at 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. The AIP has been a member of the Leibniz Association since 1992.

Read more ...
1.69 billion stars

Gaia’s all-sky view of our Milky Way Galaxy and neighbouring galaxies, based on measurements of nearly 1.7 billion stars. Credit: ESA/Gaia/DPAC

1.69 billion stars

Derived from 22 months of observations, the much awaited second data release of the Gaia mission is now public. The Leibniz Institute for Astrophysics Potsdam (AIP) contributed to the common effort...

The second data release contains the position and brightness of 1 692 919 135 stars, as well as measurements of the parallax and proper motion of 1 331 909 727 stars. Parallax is a small motion in the apparent position of a star caused by the Earth's yearly orbit around the Sun and depends on its distance from us. Proper motion is caused by the movement of a star through the Galaxy.

The now published data release contains more astrometric information than any other catalogue and represents a huge leap forward with respect to the mission's first data release. For the first time, the Gaia catalogue also includes high accuracy three-band photometry, radial velocities and stellar atmospheric parameters. With this observational data the Gaia mission produces a precise 3D map of the Milky Way with positions and velocities.

“The AIP contributes to the Gaia data analysis with two software modules for the radial velocity spectrometer on board Gaia: a first look module for data verification and a module taking care of the background correction for the spectra” explains Katja Weingrill, Co-I of Gaia at AIP.“The first look software performs a daily data validation check. The background correction cleans the observed spectra from 'false' light arising from point sources and the diffuse background.”

The full Gaia data release 2 is available at https://gaia.aip.de. “Gaia will be a major leap forward in our understanding of the cosmos. There is hardly any field in astronomy that will not fundamentally change owing to this new Galactic census” says Matthias Steinmetz, PI of Gaia at the AIP. ”The Gaia data will also be correlated with the results by one of AIP's core projects, the RAVE Survey, which will allow an even more thorough determination of the properties and chemical compositions of the stars in this catalogue. RAVE will release its full data set in summer 2018”.

Gaia is a cornerstone mission in the science programme of the European Space Agency (ESA). Gaia was launched in December 2013 and arrived at its operating point, the second Lagrange point of the Sun-Earth-Moon system, a few weeks later. Gaia is measuring stars in our Milky Way and neighbouring galaxies at a level of accuracy never before achieved. The first data release was based on 14 months of  data and listed positions of 1.1 billion stars, but only two million parallaxes and proper motions, and no photometry, radial velocities or stellar parameters.

 

More information

Pressemitteilung der ESA: https://bit.ly/2vIIKIJ

Gaia Media Kit: https://bit.ly/2qZhlwJ

Gaia Data Center am AIP:  https://gaia.aip.de

 

 

Scientific contact at AIP

Prof. Dr. Matthias Steinmetz, 0331-7499 801, msteinmetz@aip.de
Dr. Katja Weingrill, 0331-7499 671, kweingrill@aip.de

 

Media contact

Franziska Gräfe, 0331-7499 803, presse@aip.de

 

The key areas of research at 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. The AIP has been a member of the Leibniz Association since 1992.

Read more ...