Correcting Galaxy Luminosities for Absorption ?

[Widdekind]

Correcting Galaxy Luminosities for Absorption ??

As light from distant galaxies traverses deep space towards Earth, some amount of that light is absorbed by various features lying between that emitting galaxy, and Earth receivers. Those features imprint those galaxies' observed Spectra, with Absorption Troughs. (Perhaps there are Emission Peaks as well ??)


QUESTION: When calculating galaxies' Luminosities -- to estimate their M-to-L ratio's (say) -- do Astronomers correct for all those "missing photons" from the Absorption Troughs ? To wit, do calculations of galaxies' Luminosities give credit for all of the light actually emitted at the source... or only those photons that actually reach our receivers ?? Is this effect important, or is only a tiny fraction of the photons actually absorbed ??

 

[Wallace]

The short answer is yes, astronomers attempt to take all of these issues into account. The key part though is 'attempt' and the art is not yet fully developed. For instance there has been a recent suggestion (look for papers by Simon Driver) that the dust extinction models used in interpretating galactic spectra a quite wrong, and much may have been misinterpreted. This is still a suggestion though, and there are many people looking at these and other issues.

So it is a live area of research. I can't give too many details because I'm not an expert in this area. I'd point out that the uncertainties in this area are small enough that some major change in methodology wouldn't drastically alter our overall view of the Universe (i.e. remove the expansion/Big Bang from the model) but could give us a quite different picture about galaxy formation and evolution. We still have a lot of unanswered questions in terms of exactly how galaxies form, evolve, merge and possibly in some cases die.

 

[Widdekind]

Thanks for the info & refs !