* Astronomy

Blobrana · L

RE: HDF850.1

Blobrana · L

On the edge of time and space
Galaxy HDF850.1 can be seen as it was 12.5 billion years ago

In observations with optical light telescopes, such as the Hubble Space Telescope, HDF850.1 is completely invisible. From other surveys, however, scientists knew that the object is one of the most productive star-forming galaxies in the observable universe - a Milky Way system with the extremely high stellar birth rate of 1,000 suns per year. A team of astronomers led by Fabian Walter of the Max Planck Institute for Astronomy has now managed for the first time to determine the distance of the galaxy HDF850.1. The light reaching us from it today started its voyage when the universe was less than 10% of its current age, i.e. 12.5 billion years ago. The galaxy appears to be part of a proto-galaxy cluster that formed within the first billion years of cosmic history after Big Bang.
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Blobrana · L

Le mystère de la galaxie HDF850.1 enfin résolu

Une équipe internationale d'astronomes impliquant en France des chercheurs de l'Institut de radioastronomie millimétrique (CNRS/MPG/IGN), du CNRS et du CEA a réussi à déterminer la distance à la galaxie HDF850.1, l'une des galaxies les plus actives en formation d'étoiles connue dans l'univers. La galaxie HDF850.1 est éloignée de 26 milliards d'années-lumière, bien plus loin que ce que l'on croyait, et était active lorsque l'univers avait moins de 10% de son âge actuel. Il apparaît aussi que HDF850.1 fait partie d'un amas d'une douzaine de proto-galaxies qui s'est formé lors du premier milliard d'années-lumière de l'histoire cosmique et qui est le deuxième proto-amas révélé à ce jour. Ces résultats seront publiés dans le dernier numéro de Nature.

Blobrana · L

Title: Discovery of the host galaxy of HDF850.1, the brightest sub-mm source in the Hubble Deep Field
Authors: J.S. Dunlop (University of Edinburgh), R.J. McLure, T. Yamada, M. Kajisawa, J.A. Peacóck, R.G. Mann, D.H. Hughes, I. Aretxaga, T.W.B. Muxlow, A.M.S. Richards, M. Dickinson, R.J. Ivison, G.P. Smith, I. Smail, S. Serjeant, O. Almaini, A. Lawrence

Despite extensive observational efforts, the brightest sub--mm source in the Hubble Deep Field, HDF850.1, has failed to yield a convincing optical/infrared identification almost 4 years after its discovery. This failure is all the more notable given the availability of supporting multi-frequency data of unparalleled depth, and sub-arcsec positional accuracy for the sub-mm/mm source. Consequently, HDF850.1 has become a test case of the possibility that the most violently star-forming objects in the universe are too red and/or distant to be seen in the deepest optical images. Here we report the discovery of the host galaxy of HDF850.1. This object has been revealed by careful analysis of a new, deep K-prime image of the HDF obtained with the Subaru 8.2-m telescope. Its reality is confirmed by a similar analysis of the HST NICMOS F160W image of the same region. This object is extremely faint (K=23.5), clumpy (on sub-arcsec scales) and very red (I-K > 5.2; H-K = 1.4 ±0.35). The likelihood that it is the correct identification is strongly reinforced by a reanalysis of the combined MERLIN+VLA 1.4-GHz map of the field which yields a new radio detection of HDF850.1 only 0.1 arcsec from the new near-ir counterpart, and with sufficient positional accuracy to exclude all previously considered alternative optical candidates. We have calculated new confidence limits on the estimated redshift of HDF850.1 and find z = 4.1 ±0.5. We also calculate that the flux density of HDF850.1 has been boosted by a factor of ~3 through lensing by the intervening elliptical 3-586.0, consistent with predictions that a small but significant fraction of blank-field sub-mm sources are lensed by foreground galaxies. We discuss the wider implications of these results for the sub-mm population and cosmic star-formation history.