We have observed 104 gravitationally-lensed quasars at z \sim 1 –4 with Herschel /SPIRE , the largest such sample ever studied .
By targeting gravitational lenses , we probe intrinsic far-infrared ( FIR ) luminosities and star formation rates ( SFRs ) more typical of the population than the extremely luminous sources that are otherwise accessible .
We detect 72 objects with Herschel /SPIRE and find 66 percent ( 69 sources ) of the sample have spectral energy distributions ( SEDs ) characteristic of dust emission .
For 53 objects with sufficiently constrained SEDs , we find a median effective dust temperature of 38 ^ { +12 } _ { -5 } K. By applying the radio-infrared correlation , we find no evidence for an FIR excess which is consistent with star-formation-heated dust .
We derive a median magnification-corrected FIR luminosity of 3.6 ^ { +4.8 } _ { -2.4 } \times 10 ^ { 11 } { L _ { \odot } } and median SFR of 120 ^ { +160 } _ { -80 } { M _ { \odot } yr ^ { -1 } } for 94 quasars with redshifts .
We find \sim 10 percent of our sample have FIR properties similar to typical dusty star-forming galaxies at z \sim 2 –3 and a range of SFRs < 20–10000 { M _ { \odot } yr ^ { -1 } } for our sample as a whole .
These results are in line with current models of quasar evolution and suggests a coexistence of dust-obscured star formation and AGN activity is typical of most quasars .
We do not find a statistically-significant difference in the FIR luminosities of quasars in our sample with a radio excess relative to the radio-infrared correlation .
Synchrotron emission is found to dominate at FIR wavelengths for < 15 percent of those sources classified as powerful radio galaxies .