The dust temperature of the "dusty" radio galaxy MG 1019+0535: Evidence for an outflow

Radio galaxies characteristically have strong Ly alpha emission lines. Howe ver, a few have Ly alpha equivalent widths that are substantially weaker in relation to other emission lines. One in particular, MG 1019+0535 (z = 2.7 65), was studied by Dey, Spinrad, & Dickinson in 1995. We report on our red uction of Infrared Space Observatory (ISO) data in the 160 km band for this galaxy. We also compile information on two other high-redshift active gala xies with weak Ly alpha lines, the radio galaxy TXS 0211-122 and the AGN-st arburst galaxy F10214+4724, to provide a small weak-Ly alpha line sample. I RAS plus ISO data show that F10214+4724 has a temperature 89 +/- 12 K. TXS 0211-122 was not detected in either the submillimeter or microwave. Submill imeter measurements of MG 1019+0535 by Cimatti et al. were suggestive of a dust temperature in the range 35 K less than or equal to T-d less than or e qual to 80 K. However, our 2 sigma upper limit on the flux at 160 km shows that T-d less than or similar to 32 K. An energy argument based on observat ions which constrain the total optical extinction strongly suggests that th e dust temperature must be even lower: T(d)less than or similar to 20 K. We find the contrast between the high-temperature dust in the active starburs t galaxy and the low-temperature dust in the evolved, albeit active galaxy, is consistent with an expanding cloud of dust. We find that the temperatur e range can be reconciled if we are seeing MG 1019+0535 at a poststarburst age of approximate to 500-700 Myr, with the bulk of its dust cloud at a gal actocentric distance R-d greater than or similar to 300 kpc.