Astron. Astrophys. 324, 27-31 (1997)

4. Observational aspects

Let us consider for example that the low limit of LiH abundance could be reached by an appropriate radiotelescope. From (16) and Fig.2 one can see that now if , =30 km/s, . This value of corresponds to the proto-objects at z=200 which can be seen now at =13cm. In order to estimate the observational time for level one should use the standard equation

where is a noise temperature . The IRAM observation (de Bernardis at al.,1993) has the =1000 K. At =13cm one can has =100 K. Taking into account 100 times' less here one could see that absolute value of measured in both cases are equal. But the which is predicted at =13 cm is about three order of magnitude more than at = 1.3 mm. There is another problem for observations at low frequency - it is that we need to have a full aperture radiotelescope with an appropriate angular resolution. For proto-objects with size it must be about 600 m diameter. For this case MHz and from (24) is

© European Southern Observatory (ESO) 1997

Online publication: May 26, 1998

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