Coelho,Yasmin
Brazil Valongo Observatory, UFRJ
Stellar mass distribution in barred galaxies through multi-band decomposition in the mid-IR
Observing galaxies in the Local Universe, we frequently identify an elongated central structure composed of gas and stars, called a bar – present in ∼ 65% of spirals. This structure strongly transforms its host galaxy, causing intense movement of gas and stars, breaking the axisymmetric disk dynamics and affecting its evolution. We choose the mid-infrared to focus on lower mass stars – which are the majority – and avoid obscuration caused by dust. We aim to study the amount of stellar mass involved in this structure, and how it might influence the galaxy as a whole. For this we use data for 371 barred galaxies
from the Spitzer Survey of Stellar Structure in Galaxies (S4G). S4G consists of imaging in the 3.6 and 4.5 μm bands for more than 2300 nearby, large and bright galaxies obtained by the Spitzer Space Telescope. The S4G team made a publicly available GALFIT-based decomposition in the 3.6 μm band. This 2D image decomposition fits different stellar components — including bulge, disk, bar, nuclear point source and/or secondary disk — resulting in a final decomposition model with 1-4 components for each galaxy. Knowing the flux contained in each component from the decomposition, we can estimate the stellar mass of such structures. We compared samples of galaxies with different global masses and found that there seems to be a trend towards more massive galaxies, and with a bulge in the galaxy model, with bars with a higher relative mass. We found that bars are less present in lower mass galaxies (M∗ < 10^9 M⊙, about 38%). This is consistent with bar fraction studies that suggest that lower-mass galaxies are still acquiring and growing their bars. We are working to include the 4.5 μm band, with a multi-band decomposition of the bands 3.6 and 4.5 μm using GALFITM – GALFIT’s version that allows simultaneous multi-band decomposition – to build a model for our galaxies. As we advance in our multi-band decomposition, we will be able to draw more accurate conclusions on how the stellar mass contained in the bar influences other global properties of the host galaxy.