Other
Scientific paper
Sep 1981
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1981apj...248..460w&link_type=abstract
Astrophysical Journal, Vol.248, P. 460, 1981
Other
50
Scientific paper
We report the detection of 21 cm absorption by neutral hydrogen in front of PKS 1157+014, a QSO with emission redshift Zem = 1.978 ± 0.008. The absorption line arises at 482.537 ± 0.002 MHz, corresponding to a redshift Zabs = 1.94362 ± 0.00001 that is identical, within observational errors, to the previously detected optical redshift of absorption system d. The coincidence between radio and optical redshifts reinforces the case for uniformity of physical laws throughout most of spacetime. The presence of several other absorption systems, along with this one, spanning a range in Zabs corresponding to velocities from +1000 to -8500 km s-1 suggests that this system, along with the others, is ejected from QSO. However, the determination of the spin temperature Ts from a comparison of Lyα and 21 cm absorption spectra argues against this interpretation. Our upper limit of Ts < 470 K places system d farther than 10 kpc from the QSO to avoid excitation effects of the 21 cm continuum. At this distance the absorption system requires 100 times more radiative momentum than the QSO can offer. Instead, we suggest that system d is part of an H I disk of a galaxy gravitationally bound to a cluster containing the QSO.
Briggs Frank H.
Jauncey David L.
Wolfe Arthur M.
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