Monique Signore

Molecular Signals from Primordial Clouds at High Redshift

The possibility to detect cosmological signals from the post-recombination Universe is one of the main aims of modern cosmology. In a previous paper we emphasized the role that elastic resonant scattering through LiH molecules can have in dumping primary CBR anisotropies and raising secondary signals. Here we extend our analysis to all the evolutionary stages of a primordial cloud, starting with the linear phase, through the turn-around and to the non linear collapse. We have done calculations for proto-clouds in a CDM scenario and, more generally, for a set of clouds with various masses and various turn-around redshifts, in this case without referring to any particular structure formation scenario. We found that the first phase of collapse, for

Molecular cooling of a collapsing protocloud

t/t_{free-fall}=0.05\div 0.2

Primordial LiH: the chemistry in a collapsing protocloud

is the best one for simultaneous detection of the first two LiH rotational lines. The observational frequency falls between 30 and 250 GHz and the line width

Cooling balance and thermal instability of a collapsing molecular protocloud

{\Delta \nu\over \nu}

The cosmological microwave background radiation, cosmic and superconducting strings

is between

The first spectral line surveys searching for signals from the dark ages

10^{-5}

From nuclei to atoms and molecules: the chemical history of the early Universe

and

The absence of distortion in the cosmic microwave background spectrum and superconducting cosmic strings

10^{-4}

String theories and millisecond pulsars

. As far as we know this is the most favourable process to detect primordial clouds before they start star formation processes.

The dipole anisotropy of the cosmic microwave background radiation

Abstract We analyse the physics at the beginning stage of the early cloud formation using an updated primordial lithium chemistry. As in Puy & Signore (1996)[A&A, 305, 371] we consider a simple model of a collapsing protocloud after the recombination epoch but paying special attention to the evolution of thermal molecular functions. We find a new cooling mechanism for collapsing protoclouds (10 9 M ⊙ , M 10 M ⊙ ). The HD molecule is the main cooling agent when the collapsing protostructure has a temperature of about 200 K .