Impact of Galactic Interactions on the Evolution of the Far-Infrared-Radio Correlation

A strong correlation has been known to exist between the far-infrared (FIR) and radio emission of the star-forming galaxies. Observations have shown that although scatter is present, this correlation holds over a range of redshifts and does not evolve. However, there has been a number of more recent observations, especially in higher redshift surveys, indicating the opposite. The question that then presents itself is - what is driving this evolution? In this work we explore the possibility that the answer might be hiding in galactic interactions and revealed by morphology. We present a number of models based on the evolving number of galaxies of different morphological types, some of which could potentially explain observed trends and scatter in general. Furthermore, we analyze a small sample of 34 submillimeter galaxies whose observations have been published and morphology classified. In this sample we look at the FIR-radio correlation separately in galaxies of different morphological types. We find that, while for both disk and irregular star-forming galaxies there are hints of evolution of this correlation with redshift, where this evolution appears to be stronger in irregular galaxies, due to low number statistics, both samples are also consistent with no evolution, making it at this point, difficult to discriminate between models. However, when analysis was performed on the combined sample, evolving and decreasing trend was indeed found, indicating, that evolution should be expected in at least one of the morphological types.

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