Radio galaxies characteristically have strong Ly \alpha emission lines .
However , a few have Ly \alpha equivalent widths that are substantially weaker in relation to other emission lines .
One in particular was studied by Dey et al .
( 10 ) , MG 1019+0535 ( z = 2.765 ) .
We report on our reduction of Infrared Space Observatory ( ISO ) data in the 160 \mu m-band for this galaxy .
We also compile information on two other high redshift active galaxies with weak Ly \alpha lines , the radio galaxy TXS 0211–122 , and the AGN–starburst galaxy F 10214+4724 , to provide a small weak-Ly \alpha line sample .
IRAS plus ISO data show that F 10214+4724 has a temperature 89 \pm 12 K. TXS 0211–122 was not detected in either the submillimeter or microwave .
Submillimeter measurements of MG 1019+0535 ( 8 ) were suggestive of a dust temperature in the range 35 { K } \leq T _ { d } \leq 80 K. However our 2- \sigma upper limit on the flux at 160 \mu m shows that T _ { d } \lesssim 32 { K } .
An energy argument based on observations which constrain the total optical extinction strongly suggests that the dust temperature must be even lower ; T _ { d } \lesssim 20 K. We find the contrast between the high-temperature dust in the active starburst galaxy and the low-temperature dust in the evolved , albeit active galaxy , is consistent with an expanding cloud of dust .
We find that the temperature range can be reconciled if we are seeing MG 1019+0535 at a post-starburst age of \approx 500 - 700 Myr , with the bulk of its dust cloud at a galactocentric distance R _ { d } \gtrsim 300 kpc .