Definition of L_FIR in pdrtpy

[Andrew Mizener]

Hi all,

I'm a grad student in Alex Pope's lab at UMass Amherst using pdrtpy to understand the gas conditions in an interesting z~4 lensed galaxy. I have C[II] and CO measurements, as well as an estimate of the dust continuum emission via observed-frame 1.1mm data. I want to estimate the L_FIR by integrating under an appropriately scaled template SED. I'm left with one question - under which wavelength range should I integrate? I can't find a clear definition of that quantity in the literature or the pdrtpy documentation - I've seen it variously defined as 40-500um, 42.5-122.5um, and 50-300um. Which of these, if any, is an appropriate choice for use with the wk2020 model set?

Many thanks,

Andrew Mizener

[Mark Wolfire]

Hi Andrew

    I agree that it is defined in various ways throughout the literature. I tried to straighten it out

in my recent review article (Wolfire, Vallini, & Chevance, ARAA, 2022). The models estimate the L_FIR

by taking 2 x G_0, with the physical interpretation that all of the FUV is absorbed and converted to

dust emission. But there is also optical radiation with an energy comparable to the FUV radiation 

that is also absorbed and converted to dust emission. So then in going from observations to models 

one should include all of the dust emission (including that from PAHs) so the integral would go from 8 um to 1 mm. 

This is sometimes called the TIR rather than the FIR, and it is really the TIR that should be used. 

Mark