|
Abstract:
|
The subject of this thesis is a precise determination of the Baryonic Mass Func-
tion (BMF) for a representative sample of nearby galaxies, where BMF stands for
the distribution of the galaxies’ baryonic masses. Detailed dynamical models were
derived for a sample of galaxies based on the publicly available THINGS (The HI
Nearby Galaxy Survey) survey, based on the the 21 cm emission line of atomic
hydrogen hi.
THINGS rotation curves, that reflect dynamical mass, were fitted by the sum of
the contributions from the stellar component, neutral atomic gas, and dark matter
for 20 THINGS galaxies. The mass of stellar components is measured from the
Spitzer photometry in the 3.6 μm band, while the amount of atomic gas is derived
directly from the radio observations in THINGS. For the assumed dark matter dis-
tribution we used the observationally motivated pseudo-isothermal profile (ISO) and
the Navarro-Frenk-White (NFW) profile based on the ΛCDM cosmological model.
Dynamical modeling of the total mass was performed with free scaling of the
stellar component contribution (mass-to-light ratio, M/L), and also with the same
parameter fixed on a value consistent with stellar evolution population models. Con-
vergence of the fitting procedure was reached for all the dynamical models with the
free mass-to-light ratio, while the modeling with the fixed ratio was successful for 16
objects. The mass of the stellar component, gas, dark matter, baryonic, and total
mass, were derived for the sample of galaxies and the aforementioned four sets of
dynamical models (two dark matter models with both free and fixed M/L values).
The total BMF is constructed by summing the masses of the baryonic compo-
nents (stars and gas) for galaxies in the given range of galactic masses.
Furthermore, we discuss how typical our Galactic neighborhood and our Galaxy,
the Milky Way, as a giant spiral, are in terms of component masses and their place
on the global (and local) BMF. |