IAU00865
Presentation type requested: POSTER
EROS IN MID-IR: DUSTY STARBURSTS AND OBSCURED AGN
Petri Väisänen
European Southern Observatory, Chile
We present results of a search of EROs, ie. extremely red galaxies with R-K>5, in ELAIS fields. In our wider/shallower 1 sq.deg. survey we find densities consistent with the bright end of other ERO surveys, 0.01 per sq.arcmin to K<17.5 mag. To separate the EROs into different types (ellipticals, dusty starbursts, disks) we attempt to use for the first time mid-IR fluxes from ISO, in addition to conventional optical and NIR colour characteristics and morphology. A negligible part is detected in the MIR, implying ellipticals (or quiescent disks) as the parent population of the brighter EROs. The ISO-data is too shallow to fully probe the fainter ERO-sample. However, we find that a significant fraction of the ISOCAM sources are EROs themselves, some with very high 15 micron to K-band flux ratios. We show this to indicate that these sources are powered by obscured AGN, rather than pure starbursts. We present expected fractions of AGN in the ERO population. Moreover, the ERO surface density around ISO MIR-sources in general is several times higher than the field ERO-density. We discuss the implications of this strong clustering on the nature of EROs and galaxy formation scenarios.
Johansson Peter
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