TY  - GEN
CY  - Heidelberg
AV  - public
Y1  - 2019///
TI  - Probing the cold phase of the interstellar medium and star formation in nearby galaxies
ID  - heidok26881
A1  - Tomi?i?, Neven
UR  - https://archiv.ub.uni-heidelberg.de/volltextserver/26881/
N2  - Properly measuring the spatial distribution of the star formation rate (SFR) in galaxies helps us to understand the driving forces for the star formation in galaxies, effects on their interstellar media (ISM), and their evolution. However, this is hindered by the uncertainties in estimating SFRs and calibrating the SFR prescriptions. These uncertainties are caused by not properly measuring the attenuation of light, probing large spatial scales, or averaging over large sample of galaxies. Additionally, the physical factors that set the efficiency whith which galaxies convert gas into stars (star formation efficiency; SFE), and their role in galactic evolution, are not yet fully understood. Variations in the SFE are difficult to disentangle from  uncertainties of estimated SFRs. The main goal of this thesis is to use optical integral field unit (IFU) observations of nearby galaxies, in order to probe the cold phase of their ISM at sub-kpc scales. We aim to measure the attenuation, thus to properly estimate the SFRs and calibrate the SFR prescriptions. We also estimate variations of SFE across the disk of an interacting galaxy. Using IFU observations of the outskirts of the Andromeda galaxy (M31) at sub-kpc scales (from 10 pc to kpc), we derive the Balmer line attenuation. By comparing attenuation with the dust mass surface density, we derive the 3-dimensional spatial distribution of dust and ionized gas in M31. Our results indicate that the vertical dust/gas distribution from the central areas of nearby galaxies differs from the outskirts of M31. From this evidence, we hypothesize that the vertical dust/gas distribution in galactic disks varies as a function of the galactocentric distance. Following that, we use extinction corrected Balmer line emission as a reference SFR tracer in a combination with ultraviolet and near-infrared images, to calibrate  hybrid SFR prescriptions. We find  that the hybrid SFR prescriptions do not change with spatial scale or with the subtraction of a diffuse component. However, our SFR prescriptions observed in M31 differ from the prescriptions in the literature. This indicates that the SFR prescriptions are not universal and that they may vary with the inclination and the galactocentric radius, due to varying dust/gas distributions. Our IFU observations of the interacting galaxy NGC 2276 are used to investigate how the  early phase of galactic  interaction affects  the ISM, and SFE across its disk. Although NGC 2276 shows a significant asymmetrically elevated SFR surface density, and asymmetric stellar distribution, it does not show an unusual gas phase metallicity gradient or shock ionization. On the other hand, we probed the SFE at sub-kpc scales (0.5 kpc) across NGC 2276's disk to trace the origin of its elevated and asymmetric SFR and found more than two orders of magnitude variation in SFE. This is significantly larger than what is seen in nearby galaxies. We speculate that this is caused by both tidal forces exerted from a neighboring galaxy and ram pressure affecting NGC 2276.
ER  -