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ESO 26/07 - Associated Images

13 June 2007
For Immediate Release

Free from the Atmosphere

Laser Guide Star System on ESO's VLT Starts Regular Science Operations

IRAS 06035-7102 was formed as two spiral galaxies swung past each other on their first close encounter, throwing off huge streamers of gas and stars. At the same time, multiple bursts of vigorous star formation were ignited. The detail in the image allows these compact star clusters to be easily seen, both around the progenitor nuclei and also in the tidal tails. This is a K-band image obtained with NACO and the LGS. The colour-code corresponds to intensity.

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This comparison between the seeing-limited image (from the UKIRT archive; left) and the LGS-AO image of the pair of interacting galaxies IRAS 09061-1248 shows the vast amount more detail the Adaptive Optics technique with laser guide star can reveal. The right image is a K-band image obtained with NACO and the LGS. The colour-code corresponds to intensity.

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In this galaxy the nuclei are much closer and cannot be distinguished without high spatial resolution. This was a challenging galaxy to observe because it is very difficult to perform the corrections. Nevertheless, a resolution comparable to the Hubble Space Telescope was achieved, i.e. 0.2 second of arc. It reveals for the first time the motion of the stars in this system, showing that there are two counter-rotating discs of stars. These are the nuclei of the progenitor galaxies. In contrast, the motion of the gas is dominated by a larger scale disc, formed from the leftover gas in the discs of the progenitors. The rotation of this gas is governed by the geometry of the interaction, and so is different to that of the stars in the progenitor nuclei. The four images show (from left to right and from top to bottom): the distribution of the molecular gas, the stellar light, the velocity of the gas, and the velocity of the stars. For the velocity maps, the blue and red colours indicate motion towards us and away from us respectively.

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This galaxy is located more than 10.5 billion light years away, at which distance high spatial resolution is needed to trace the different locations of the stars and gas. This near infrared image taken with NACO shows that the stars in this galaxy lie within a quite compact region. In contrast, the gas, which was observed with SINFONI, is very extended. This is not always the case: in another galaxy at a similar redshift, NACO and SINFONI observations (see ESO 31/06) show that the gas and stars lie in the same large disc. Observations like these are both remarkable and exciting. They yield important insights into the evolution of massive galaxies at early cosmological epochs, allowing us to distinguish between outflowing gas, rotating disk galaxies, and chaotic galaxy mergers.

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K-band image obtained with NACO and the LGS of the active galaxy NGC 4945. The colour-code corresponds to intensity. Lurking in the very heart of this spiral galaxy is a supermassive black hole that is obscured at optical and infrared wavelengths, but which is one of the brightest in the local universe when observed in hard X-rays. The new LGS observations with NACO resolved the continuum in the central thousand light-years into a multitude of individual stars. The exquisite detail meant that it was possible to measure the magnitudes of the brightest of these stars. It suggests that they are red supergiant stars, which would have been born about 10 million years ago. Closer to the nucleus, the stars group into clusters, and become ever more closely packed. The huge luminosity of the central few clusters suggests that there are 10 to 100 such supergiant stars in each of these, packed into regions just a few parsecs across.