Comparative Study of Asymmetry Origin of Galaxies in Different
  Environments. II. Near-Infrared observations
  In this second paper of two analyses, we present near-infrared (NIR)
morphological and asymmetry studies performed in sample of 92 galaxies found in
different density environments: galaxies in Compact Groups (HCGs), Isolated
Pairs of Galaxies (KPGs), and Isolated Galaxies (KIGs). Both studies have
proved useful for identifying the effect of interactions on galaxies. In the
NIR, the properties of the galaxies in HCGs, KPGs, and KIGs are more similar
than they are in the optical. This is because the NIR band traces the older
stellar populations, which formed earlier and are more relaxed than the younger
populations. However, we found asymmetries related to interactions in both KPG
and HCG samples. In HCGs, the fraction of asymmetric galaxies is even higher
than what we found in the optical. In the KPGs the interactions look like very
recent events, while in the HCGs galaxies are more morphologically evolved and
show properties suggesting they suffered more frequent interactions. The key
difference seems to be the absence of star formation in the HCGs; while
interactions produce intense star formation in the KPGs, we do not see this
effect in the HCGs. This is consistent with the dry merger hypothesis (Coziol &
Plauchu-Frayn 2007); the interaction between galaxies in compact groups, (CGs),
is happening without the presence of gas. If the gas was spent in stellar
formation (to build the bulge of the numerous early-type galaxies), then the
HCGs possibly started interacting sometime before the KPGs. On the other hand,
the dry interaction condition in CGs suggests that the galaxies are on merging
orbits, and consequently such system cannot be that much older either.
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