The following document lists the file abstract/PVDWERF_6C1909.abs
from catalogue VI/111.
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This is a discretionary time proposal to follow up on our open time project of CAM and PHOT imaging of high-z radio galaxies. These objects are the progenitors of present-day massive ellipticals, and their stellar populations are believed to have formed in a strong burst at high z. We have been very succesful with one object, the z=3.5 radio galaxy 6C1909+722, detecting it with PHOT at 160 micron and with CAM at 12 micron. As a confirmation, we have also detected it with SCUBA at the JCMT at 850 micron. The rest-frame far-IR emission has a total luminosity of about 5e13 Lsun, corresponding to a star formation rate of 5000 Msun/yr if powered by star formation. Perhaps even more exciting is our detection of the source with CAM at 12 microns. This corresponds to rest frame 2.6 micron and thus measures a combination of hot dust emission and photospheric emission from an evolved stellar population, that can only be disentagled with further data ISOCAM data, at shorter wavelengths. This is the purpose of the present request. We request 3 hours of CAM time to observe this object with LW2 (7 micron), to a 5 sigma limit of 0.07 mJy. This corresponds to rest frame 1.6 micron and thus samples ONLY an evolved stellar population (if present), NOT any hot dust. Non-detection at this sensitivity level is HIGHLY significant and will show the ABSENCE of an evolved underlying population, confirming that the object is a truly primeval galaxy, cuurently forming its stellar population in an immense burst. On the other hand, a detection will allow us to measure the mass of an evolved population, and if a significant old population is present, will push its formation redshift back to very high z. Either way this project will have fundamental implications fro the formation of massive galaxies, and will be a unique contribution of ISO to this field.