Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Dusty substructure in a galaxy far far away

31.03.2015

Scientists at the Max Planck Institute for Astrophysics (MPA) have combined high-resolution images from the ALMA telescopes with a new scheme for undoing the distorting effects of a powerful gravitational lens in order to provide the first detailed picture of a young and distant galaxy, over 11 billion light-years from Earth. The reconstructed images show that star formation is heating interstellar dust and making it glow strongly in three distinct clumps embedded in a broader distribution, suggesting that object may be a rotating disk galaxy seen nearly edge-on.

Galaxies are constantly forming new stars within dense clouds of interstellar material. The star formation rate in today's galaxies is, however, much lower than it used to be. When the universe was about a quarter its current age, star formation was at its peak, and so astronomers are keen to learn about this period.


Fig. 1 The ALMA image of the continuum emission at 236 GHz of the lensed galaxy SDP.81 at two angular resolutions. The lensed system consists of four images with an extended, low-surface brightness Einstein ring.


Fig. 2 The modelled sky-brightness distribution for the image in Fig. 1 (left) and the reconstructed surface brightness distribution (right) of the background galaxy. There are three areas with enhanced emission, which could indicate a disk galaxy seen edge-on.


Fig. 3 This map shows the reconstructed star formation rate of the distant galaxy, which is actually quite small (as indicated by the length scale in light-years). The colour coding shows the amount of dust heated by radiation from the young stars.

Looking back in time is possible because of the finite speed of light, but only by looking out to great distances, which in turn means that young galaxies appear very small and very faint. In addition, most of their new-born stars cannot be seen directly, because their radiation is absorbed by dust in the surrounding gas cloud and is re-emitted at far-infrared wavelengths.

As a result, star-forming regions in distant galaxies are one of the prime targets for the Atacama Large Millimetre/submillimetre Array. ALMA will consist of 66 high precision antennas, located on the Chajnantor plateau at 5000 meters altitude in northern Chile.

The data from the individual antennas can be combined interferometrically, and the 15 kilometre span of the telescope provides resolution of better than a tenth of an arc-second. On its own, however, even this capability is not sufficient to make detailed pictures of young galaxies at the peak of their star formation.

"At a recent conference, ALMA scientists presented data they had used to verify the scientific capabilities of their array, among them an image of a strongly gravitationally lensed system, which immediately raised our interest", remembers Simona Vegetti, postdoctoral scientist at MPA.

"Because of the lensing, the background galaxy is strongly magnified, by 17 times actually, which is why we can see it at all. Together with ALMA's unique angular resolution, this gave us the chance to try and see details in the distribution of dust in such a far-away galaxy for the first time."

Strong gravitational lensing happens when a background galaxy is closely aligned with a foreground mass concentration such as a cluster of galaxies, which bends light-rays from the source on their way to the observer. The foreground lens is, however, an imperfect optical system, leading to very large distortions (see Fig. 1).

Nevertheless, from the properties of the lensed images, the mass distribution of the lensing system can be determined and a "true" (i.e. undistorted) image of the distant galaxy can be reconstructed. "Previous attempts to do this had assumed the background galaxies to be smooth and regular", explains Matus Rybak, who carried out the computer modelling at MPA. "This seems likely to be a very poor approximation to the structure of a strongly star-forming galaxy, and the raw ALMA images gave clear hints that this background source is complex. The new, more general approach we have developed is much better suited to irregular systems."

This intuition is borne out by the reconstructed image of the galaxy SDP.81 which shows star formation to be concentrated in three distinct regions (see Fig. 2). "This is the first time, that we can see structure in the dust emission of a z=3 galaxy on scales smaller than 150 light-years", points out Simona Vegetti. At this cosmic time, typical galaxies were forming stars at their peak rate, and indeed SDP.81 is forming about 300 solar masses of stars every year. (In our Milky Way, the star formation rate is about 3 solar masses per year.)

The complex structure of the galaxy may indicate that it is a rotating disk with a central bulge that is seen (and lensed) edge-on; alternatively it may be a system which is undergoing a merger in which the separate components are still visible. To distinguish between these possibilities, data on the motions of gas within the galaxy are needed, so the next step for the MPA team together with their colleagues Paola Andreani at ESO and John McKean at the University of Groningen and the Netherlands Institute for Radio Astronomy (ASTRON) will be to analyse the molecular line observations of this system which ALMA has also obtained.

Links:
Original publication
ALMA imaging of SDP.81 I. A pixelated reconstruction of the far-infrared continuum emission, M. Rybak, J. P. McKean, S. Vegetti, P. Andreani and S. D. M. White, linkPfeilExtern.gifsubmitted to MNRAS

Contact:
Simona Vegetti
Max-Planck-Institut für Astrophysik
Phone: 089 30000-2285
Email: svegettimpa-garching.mpg.de

Hannelore Hämmerle
Press Officer
Max-Planck-Institut für Astrophysik
Tel. +49 89 30000-3980
E-mail: prmpa-garching.mpg.de

Hannelore Hämmerle | Max-Planck-Institut für Astrophysik
Further information:
http://www.mpa-garching.mpg.de/mpa/institute/news_archives/news1504_aaa/news1504_aaa-en.html

More articles from Physics and Astronomy:

nachricht Hope to discover sure signs of life on Mars? New research says look for the element vanadium
22.09.2017 | University of Kansas

nachricht Calculating quietness
22.09.2017 | Forschungszentrum MATHEON ECMath

All articles from Physics and Astronomy >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: The pyrenoid is a carbon-fixing liquid droplet

Plants and algae use the enzyme Rubisco to fix carbon dioxide, removing it from the atmosphere and converting it into biomass. Algae have figured out a way to increase the efficiency of carbon fixation. They gather most of their Rubisco into a ball-shaped microcompartment called the pyrenoid, which they flood with a high local concentration of carbon dioxide. A team of scientists at Princeton University, the Carnegie Institution for Science, Stanford University and the Max Plank Institute of Biochemistry have unravelled the mysteries of how the pyrenoid is assembled. These insights can help to engineer crops that remove more carbon dioxide from the atmosphere while producing more food.

A warming planet

Im Focus: Highly precise wiring in the Cerebral Cortex

Our brains house extremely complex neuronal circuits, whose detailed structures are still largely unknown. This is especially true for the so-called cerebral cortex of mammals, where among other things vision, thoughts or spatial orientation are being computed. Here the rules by which nerve cells are connected to each other are only partly understood. A team of scientists around Moritz Helmstaedter at the Frankfiurt Max Planck Institute for Brain Research and Helene Schmidt (Humboldt University in Berlin) have now discovered a surprisingly precise nerve cell connectivity pattern in the part of the cerebral cortex that is responsible for orienting the individual animal or human in space.

The researchers report online in Nature (Schmidt et al., 2017. Axonal synapse sorting in medial entorhinal cortex, DOI: 10.1038/nature24005) that synapses in...

Im Focus: Tiny lasers from a gallery of whispers

New technique promises tunable laser devices

Whispering gallery mode (WGM) resonators are used to make tiny micro-lasers, sensors, switches, routers and other devices. These tiny structures rely on a...

Im Focus: Ultrafast snapshots of relaxing electrons in solids

Using ultrafast flashes of laser and x-ray radiation, scientists at the Max Planck Institute of Quantum Optics (Garching, Germany) took snapshots of the briefest electron motion inside a solid material to date. The electron motion lasted only 750 billionths of the billionth of a second before it fainted, setting a new record of human capability to capture ultrafast processes inside solids!

When x-rays shine onto solid materials or large molecules, an electron is pushed away from its original place near the nucleus of the atom, leaving a hole...

Im Focus: Quantum Sensors Decipher Magnetic Ordering in a New Semiconducting Material

For the first time, physicists have successfully imaged spiral magnetic ordering in a multiferroic material. These materials are considered highly promising candidates for future data storage media. The researchers were able to prove their findings using unique quantum sensors that were developed at Basel University and that can analyze electromagnetic fields on the nanometer scale. The results – obtained by scientists from the University of Basel’s Department of Physics, the Swiss Nanoscience Institute, the University of Montpellier and several laboratories from University Paris-Saclay – were recently published in the journal Nature.

Multiferroics are materials that simultaneously react to electric and magnetic fields. These two properties are rarely found together, and their combined...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

“Lasers in Composites Symposium” in Aachen – from Science to Application

19.09.2017 | Event News

I-ESA 2018 – Call for Papers

12.09.2017 | Event News

EMBO at Basel Life, a new conference on current and emerging life science research

06.09.2017 | Event News

 
Latest News

Rainbow colors reveal cell history: Uncovering β-cell heterogeneity

22.09.2017 | Life Sciences

Penn first in world to treat patient with new radiation technology

22.09.2017 | Medical Engineering

Calculating quietness

22.09.2017 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>