Optically Selected Compact Stellar Regions and Tidal Dwarf Galaxies in
  (Ultra)-Luminous Infrared Galaxies
  This thesis work is devoted to the analysis of compact star forming regions
(knots) in a representative sample of 32 (U)LIRGs. The project is based mainly
on optical high angular resolution images taken with the ACS and WFPC2 cameras
on board the HST telescope, data from a high spatial resolution simulation of a
major galaxy encounter, and with the combination of optical integral field
spectroscopy (IFS) taken with the INTEGRAL (WHT) and VIMOS (VLT) instruments. A
few thousand knots -a factor of more than one order of magnitude higher than in
previous studies- are identified and their photometric properties are
characterized as a function of the infrared luminosity of the system and of the
interaction phase. These properties are compared with those of compact objects
identified in simulations of galaxy encounters. Finally, and with the
additional use of IFS data, we search for suitable candidates to tidal dwarf
galaxies, setting up constraints on the formation of these objects for the
(U)LIRG class. Knots in (U)LIRGs are likely to contain sub-strucutre. Evidence
is found that in ULIRGs they are intrinsically more luminous than in less
luminous interacting systems due to size-of-sample effects. Furthermore, their
sizes and masses are similar to stellar complexes or clumps detected in
galaxies at z > 1, unlike local stellar complexes. The star formation in
(U)LIRGs is charaterized by a luminosity function with a slope consistent with
\alpha = 2, independent of the luminosity of the system. However, it may
flatten slightly due to, as simulations suggest, higher knot formation rates at
early phases of the interaction. Candidates to tidal dwarf galaxies are
identified in the sample. With a production rate of 0.1 candidates per (U)LIRG
system, only a few fraction (< 10%) of the general dwarf satellite population
could be of tidal origin.
