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

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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 [FORMULA] if [FORMULA], [FORMULA] =30 km/s, [FORMULA]. This value of [FORMULA] corresponds to the proto-objects at z=200 which can be seen now at [FORMULA] =13cm. In order to estimate the observational time [FORMULA] for [FORMULA] level one should use the standard equation

[EQUATION]

where [FORMULA] is a noise temperature . The IRAM observation (de Bernardis at al.,1993) has the [FORMULA] =1000 K. At [FORMULA] =13cm one can has [FORMULA] =100 K. Taking into account 100 times' less [FORMULA] here one could see that absolute value of [FORMULA] measured in both cases are equal. But the [FORMULA] which is predicted at [FORMULA] =13 cm is about three order of magnitude more than at [FORMULA] = 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 [FORMULA] size it must be about 600 m diameter. For this case [FORMULA] MHz and [FORMULA] from (24) is

[EQUATION]

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© European Southern Observatory (ESO) 1997

Online publication: May 26, 1998

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