| Abstract |
We present an investigation of the stellar content of nearby galaxies, focusing on: (a) a
census of the stellar mass in star-forming galaxies in the Local Universe, and its relation
with their star-forming activity; (b) a case study of the effects of galaxy interaction on the
globular cluster (GC) population of an elliptical galaxy.
First, we present the study of the stellar content and morphological parameters of a
sample of FIR-selected galaxies representative of the star-formation activity in the Local
Universe: the Star Formation Reference Survey (SFRS; Ashby et al., 2011). We perform a
detailed two-dimensional fit of the galaxian surface brightness by using a combination of
Sersic, exponential disk, and PSF models, intended to account for the different bulge,
disk, and AGN components. We use the light profiles of the models to obtain integrated
stellar luminosities and masses for the galaxies, as well as disentangle their bulge and
disk sub-components. Based on these results we derive the luminosity and mass
functions of nearby star-forming galaxies, and we explore the relations between starformation
activity and galaxian stellar mass, morphology, and AGN content. From the
morphological analysis, we find that: (1) the sample consists of ~62% disk-dominated
galaxies, and ~38% bulge-dominated galaxies; (2) 25% of the non-AGN SFRS galaxies
require a PSF component in their morphological decomposition, which could represent
either a weak or unresolved bulge, or a yet-unknown AGN; (3) there is no clear correlation
between the specific star-formation rate (sSFR) and morphological parameters as
represented by the the bulge-to-total luminosity ratio and/or the Sersic index. Our stellar
mass function (MF), which covers the whole range of galaxy masses from dwarf galaxies
to large spirals, is in general agreement with the previously derived MF of FIR-selected
galaxies, while its faint end appears to be flatter than that of MFs of optically-selected
samples. We also introduce a ``specific SFR function'' (the volume density of galaxies at a
given specific SFR), which spans 4 orders of magnitude, and is characterized by a sharp
peak at sSFR ~ 5 x 10-10 M⊙ yr -1 / M⊙.
As a case study of a post-merger galaxy in the Local Universe, we present an analysis of
the GC population of the elliptical galaxy NGC 4261 based on HST WFPC2 data in the B, V
and I bands. We study the spatial distribution of the GCs in order to probe the anisotropy
in the azimuthal distribution of the discrete X-ray sources in the galaxy revealed by
Chandra images (Zezas et al., 2003). The luminosity function of our GC sample (complete
at the 90% level for mV = 23.8 mag) peaks at mV= 25.1−0.6+1.0 mag, which corresponds to a
distance consistent with previous measurements. The colour distribution can be
interpreted as being the superposition of a blue and red GC component with average
colours V-I = 1.01−0.06+0.06 mag and 1.27−0.08+0.06 mag respectively. This is consistent with a
bimodal colour distribution typical of elliptical galaxies. The red GC's radial profile is
steeper than that of the galaxy surface brightness, while the profile of the blue subpopulation
looks more consistent with it. The most striking finding is the significant
asymmetry in the azimuthal distribution of the GC population about a NE-SW direction.
The lack of any obvious feature in the morphology of the galaxy suggests that the
asymmetry could be the result of a past interaction or a dry merger.
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A multi-wavelength study of the stellar content of nearby galaxies
