Abstract
We present the detailed Optical to Mid Infrared (MIR) analysis on the compact group of galaxies RSCG44. The optical analysis comprehends both photometric andspectroscopic studies for six galaxies in this group. The overall Optical to MIR data provide maps, spectra, profiles and images to analyse galaxy properties (structure, line-strength features, etc.) of each member searching for signatures of star formation and nucleus activity. In the photometric analysis, we study $BVR$ surface brightness and colors calculated for regions such as galaxy centers, possible bridges, tails and optical knots. Optical direct image also presents residual images (after subtracting isophotal models) and unsharp masked images in order to uncover any hidden structure in the system. The inclusion of maps, profiles and images from the Spitzer Space Telescope (SST) was made in order to provide a complementary outlook for the optical colors and the environment in which the group evolves, hence, a better explanation of the photospheric component and possible photdissociation regimes in polycyclic aromatic hydrocarbon (PAH) emission at 5.8 and 8 μm have provide a disentangled view of dust properties in the interstellar medium (ISM) at MIR. Optical spectra for the group are also provided to establish a more fond comparison between optical to mid infrared properties. The color gradients were compared with the optical spectra of both galaxies, showing in general similar trends for star formation. Globally, color maps, color tables and optical spectra indicate predominant stellar populations from classes I, III and V corresponding to spectral types of K-M stars with ages of at least in theorder of 10 Gyr for models using metallicity ranges with solar and non solar abundances. These results lead us to the conclusion of a moderate star formation rate and a tranquil evolving state of the system.
Highlights
Among the investigation for the global picture of the star formation history in the local Universe, one of the key questions on the subject arises when asking the question: what drives the changes in the star formation rates (SFR’s) in individual galaxies? Diversal causes, such as interactions and environment dependency, point the SFR as a function of different variables
The study of compact groups in the local universe is of great interest within the context of galaxy evolution, where good examples of candidates for fossil groups have been found at low redshifts [6], these kind of empirical studies contribute to the recent interest in trying to identify the mechanisms driving galaxy evolution on different environments [7]
Recent similar analysis than ours have appeared with Walker et al [19] who used this compact group as part of a larger sample to compare Hickson compact groups properties as well as environment properties of RSCG’s with Mid Infrared (MIR) colors, this paper provides a more indetailed analysis of the RSCG 44 group using a different approach than that made by Walker et al [19]
Summary
Among the investigation for the global picture of the star formation history in the local Universe, one of the key questions on the subject arises when asking the question: what drives the changes in the star formation rates (SFR’s) in individual galaxies? Diversal causes, such as interactions and environment dependency, point the SFR as a function of different variables (like mass, time, lumnosity, chemical composition, etc.). The rate of star formation was not as high as predicted by the first models in some group samples [4], while others, like the study made by Severgnini & Saracco [5] with a sample of 95 galaxies in 31 HCG’s, suggested that higher levels of star formation (measured by Hα emission) are associated with slower interactions between the group members. The study of compact groups in the local universe is of great interest within the context of galaxy evolution, where good examples of candidates for fossil groups have been found at low redshifts [6], these kind of empirical studies contribute to the recent interest in trying to identify the mechanisms driving galaxy evolution on different environments [7]
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