We describe the far-infrared ( far-IR ; rest-frame 8–1000 \mu m ) properties of a sample of 443 H \alpha -selected star-forming galaxies in the COSMOS and UDS fields detected by the HiZELS imaging survey .
Sources are identified using narrow-band filters in combination with broad-band photometry to uniformly select H \alpha ( and [ O ii ] if available ) emitters in a narrow redshift slice at z = 1.47 \pm 0.02 .
We use a stacking approach in Spitzer -MIPS mid-IR , Herschel -PACS/SPIRE far-IR ( from the PACS Evolutionary Probe ( PEP ) and Herschel Multi-tiered Extragalactic Surveys ( HerMES ) surveys ) and AzTEC mm-wave images to describe their typical far-IR properties .
We find that HiZELS galaxies with observed H \alpha luminosities of L ( { H \alpha } ) _ { obs } \approx 10 ^ { 8.1 - 9.1 } L _ { \odot } ( \approx 10 ^ { 41.7 - 42.7 } erg s ^ { -1 } ) have bolometric far-IR luminosities of typical luminous IR galaxies , L ( 8 - 1000 \mu { m } ) \approx 10 ^ { 11.48 ^ { +0.04 } _ { -0.05 } } L _ { \odot } .
Combining the H \alpha and far-IR luminosities , we derive median star-formation rates of SFR _ { H \alpha,FIR } = 32 \pm 5 M _ { \odot } yr ^ { -1 } and H \alpha extinctions of A _ { H \alpha } = 1.0 \pm 0.2 mag .
Perhaps surprisingly , little difference is seen in typical HiZELS extinction levels compared to local star-forming galaxies .
We confirm previous empirical M _ { \star } - A _ { H \alpha } relations and the little or no evolution up to z = 1.47 .
For HiZELS galaxies ( or similar samples ) we provide an empirical parametrisation of the SFR as a function of rest-frame ( u - z ) colours and 3.6 \mu m photometry – a useful proxy to aid in the absence of far-IR detections in high- z galaxies .
We find that the observed H \alpha luminosity is a dominant SFR tracer when rest-frame ( u - z ) colours are \lesssim 0.9 mag or when Spitzer -3.6 \mu m photometry is fainter than 22 mag ( Vega ) or stellar masses are lower than 10 ^ { 9.7 } M _ { \odot } .
We do not find any correlation between the [ O ii ] /H \alpha and far-IR luminosity , suggesting that this emission line ratio does not trace the extinction of the most obscured star-forming regions , especially in massive galaxies where these dominate .
The luminosity-limited HiZELS sample tends to lie above of the so-called ‘ main sequence ’ for star-forming galaxies , especially at low stellar masses , indicating high star-formation efficiencies in these galaxies .
This work has implications for SFR indicators and suggests that obscured star formation is linked to the assembly of stellar mass , with deeper potential wells in massive galaxies providing dense , heavily obscured environments in which stars can form rapidly .