European Large Area ISO Survey
European Large Area ISO Survey
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European Large Area ISO Survey

Overview of the ELAIS survey

  • Summary
  • Scientific Aims
  • Collaboration



    ELAIS is a collaborative effort between 19 European institutions that has carried out a deep wide angle survey with ISO at four wavebands (6.7 and 15µm using CAM and 90 and 175µm with PHOT) over a area of about 12 square degrees of high latitude sky. The areas surveyed are sumarized in next table.

    Area Rasters Coordinates
    N1 3 x 3 16 08 44 +56 26 30
    N2 4 x 2 16 39 44 +41 15 34
    N3 3 x 3 14 28 26 +32 25 13
    S1 4 x 3 00 38 24 -43 32 02
    Lock 3 1 13 35 36 +37 54 36
    Sculptor 1 00 22 48 -30 54 36
    TX1436 1 14 36 43 +15 44 13
    4C24.28 1 13 48 15 +24 15 50
    VLA 8 1 17 14 14 +50 15 24
    Phoenix 1 01 13 13 -45 14 07

    The four main areas were selected on the basis of:

    The smaller regions have been selected on the basis of the existence of deep ground based material or the presence of known high redshift objects.


    Scientific Aims

    While it is impossible to predict all the scientific benefits of such a large project, below is outlined some of the key issues that we hope to address. A major theme is the detection of high redshift galaxies, the derivation of the star formation history of the Universe between now and a redshift 1 and the compilation of unbiased samples of active galaxies.

    Epoch of Galaxy Formation

    Ly-alpha searches have failed to find the epoch of galaxy formation. If elliptical galaxies underwent an intense period of star formation accompanied by prodigious quantities of dust they may be undetectable in the optical but detectable in the far infrared.

    Star Formation in Spiral Galaxies at High Redshift

    The main extra-galactic population detected by IRAS was galaxies with high rates of star formation. The far infrared emission arises from dust heated by young stellar populations. The sesitivity of ISO will allow us to detect these objects at much higher redshifts and thus abtain greater understanding of the cosmological evolution of star formation.

    Ultra and Hyper-Luminous IR Galaxies at high redshift

    IRAS uncovered a population with enormous far infrared luminosities. Exploration of these objects at higher redshift will have particular significance for models of AGN/galaxy evolution.

    Emission from dusty tori around AGN

    Unified models of AGN suggest that the central engine is surrounded by a dusty torus. Optical properties are then dependent on the inclination angle of this torus. The far infrared emission from the torus will be less sensitive to the viewing angle. The far infrared properties of these will place important constraints on unification schemes.

    Dust in normal Galaxies to Cosmological Distances

    Faint optical redshift surveys find surprisingly few galaxies beyond z=1. One possible explanation for this is a dust fraction that increases with z. Emission from the cool interstellar 'cirrus' dust in normal galaxies will be detectable in our survey to much grater distances than were accesible with IRAS, so we will be able to examine the dust content to higher z.

    Circumstellar Dust Emission from Galactic Halo Stars

    The deep stellar number counts provided by this survey will be relatively unaffected by Galactic extinction and may provide improved estimates of the halo/disk population ratios.

    New classes of objects

    F10214 was discovered at the limit of the IRAS capability and it is reasonable to hope that equally unexpected and exciting objects will be discovered at the limits of this survey.

    Clustering Properties

    The volume of this survey is comparable to that surveyed by the entire IRAS Point Source Catalog. The median redshift will be much higher. We will thus be in a position to examine the evolution of clustering strength, giving perhaps the most direct test of gravitational instability picture of structure formation.



    These are the european institutes involved in the ELAIS collaboration:

    A full list of the members of the ELAIS consortium can be found at Imperial College ELAIS pages..

    These are the members of ELAIS consortium at IAC:

    and at IFCA:

    and at IAA: