Affiliation:
1. Mathematical Institute of the Serbian Academy of Sciences and Arts, Belgrade, Serbia + Faculty of Mathematics, Department of Astronomy, University of Belgrade, Belgrade, Serbia
Abstract
It was confirmed that there is a strong linear correlation between the thermal
far-infrared (FIR) and non-thermal radio emission of the star-forming
galaxies. Recent works based on this correlation over large redshifts have
shown that the correlation is evolving towards higher redshifts. In this
paper, possible physical causes that lead to the evolution of this
correlation are explored. One possible cause is that the interaction between
galaxies is responsible for this behavior. We used the morphology of
galaxies, as an indicator of past or present interactions, because it is
generally known that the irregular morphology of galaxies is a consequence
of collisions or close approaches. To test this hypothesis, a sample of
dusty star-forming galaxies up to a redshift z = 3:5 from the COSMOS field
has been selected. The sample has been divided, according to the
morphological type, into two subsamples (disk and irregular galaxies), and
the evolution of the correlation with redshift has been analyzed separately
for both of them. It was found that in both subsamples there is no
indication for the redshift evolution of the FIR-radio correlation. However,
it was also found that the mean correlation parameter, qFIR, is lower in
irregular galaxies, which may indicate that they can still affect the
evolution of the correlation if their abundance in the sample increases
towards higher redshifts. Disk galaxies, which statistically dominate the
sample, may be responsible for the lack of this evolution. On the other
hand, a fundamental problem with optically determined morphology is the dust
obscuration in massive galaxies at z > 2. To test the idea that interacting
galaxies are responsible for redshift evolution of the FIR-radio
correlation, it is, necessary to analyze a much larger sample for which the
morphology has been determined, taking into account the VLA and ALMA imaging
in addition to optical images, and which contains a higher fraction of
irregular galaxies. Finally, it was also found that the qFIR parameter and
its evolution are very sensitive to the radio spectral index above z > 1 and
that its misinterpretation and taking a constant value of ? = 0:7 may be
responsible for the observed evolution of the correlation.
Publisher
National Library of Serbia
Subject
Astronomy and Astrophysics
Cited by
2 articles.
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