Evidence from the 21 cm Line Relating to Intergalactic Gas [and Discussion]

R. D. Davies, C. J. Hogan
1980 Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences  
No evidence has been found for distributed H i a t red shifts 2 , alth o u g h clum ped H i is found in the absorption spectra o f quasars. O bservations o f n earb y groups o f gal axies in d icate th e presence o f substantial am ounts o f H i lying outside the optical con fines o f the galaxies. Some o f this m aterial is in th e form o f tid al bridges an d tails an d some is condensed in to discrete in terg alactic clouds. H i observations have also been used to investigate w ith higher
more » ... ate w ith higher precision th a n h ith erto the virial mass o f groups o f galaxies. T w o such groups have a low er mass an d a low er mass lig h t ratio th a n o b tain ed from eq u iv alen t optical studies. T h e origin o f this difference is n o t fully understood, b u t it m ay have consequences for the conventional m ethods o f determ in in g th e mass density o f th e U niverse. Finally, searches for H i in th e epoch o f galaxy for m atio n (z -3-10) are described. Lim its have been set on the masses an d th e volum e density o f protoclusters a t z -3.3 an d 4.9 . T his appears to be an im p o rta n t area for fu rth er observational an d theoretical study.
doi:10.1098/rsta.1980.0185 fatcat:ddcewe5asfhfznjdv35lheqohy