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The early part of the project was dominated by trying to understand the data that would be used.
The data used for distant galaxies was presented in \cite{Tomczak_2014}. This paper contains a table of mass vs number density (number of galaxies per unit volume) for $0.2 < z <
3$. 3$ which we use to construct the stellar mass function (SMF). However, while we plotted this data and various subsets of it (only star forming or quiescent galaxies) we do not use the raw data. Instead, we use a paramaterised double Schechter function
from \cite{Leja_2015} which smooths the data and ensures the number density at each mass is monotonically increasing as $z
\leftarrow 0$
We do not use the raw data
We made various graphs to better understand how the growth rate was affected by whether the galaxy was quiescent or star forming. We checked their use of Schechter and Double Schechter functions, before paramaterising the Schechter function to smooth the relationship and ensure that the number density at a specific mass increased monotonically as z approached 0 \cite{Leja_2015}. \rightarrow 0$. With this done, graphs showing the
change in mass over
time between Z = 3 and Z = 0 were constructed $0.2 < z < 3$ for various start
masses. masses were constructed.
A second distant The local group dwarf galaxy data
set was
also introduced later in the project. This data, taken from
\cite{Whitaker_2014} was used to confirm that \cite{Weisz_2014}. This paper determines the
results were reasonable and backed up mass of a subset of the known dwarf galaxies between $0 < z < 2.6$ by calculating the star formation history (sfh). As with the distant galaxies, graphs showing the percentage of mass over time for various groups of the galaxies (grouped by
other galaxy shape or location) were plotted to better understand the data.
Again, a paramaterisation rather that raw data was used.
The local group dwarf A second distant galaxy data
set was
introduced later in the project. This data, taken from
\cite{Weisz_2014}. As with \cite{Whitaker_2014} was used to confirm that the
other data sets, comparison between the
first uses of this two main data
sets were
reasonable and conformed to
help my understanding. Graphs showing the percentage of mass over time of the galaxies were plotted. other data. Again, a paramaterisation rather than raw data was used.
\textbf{Analysis}
The major correction so far A number of corrections must be applied to
this distant galaxy data concerns mergers. The local group data is based on galaxies that have not undergone mergers \textbf{is this true} and so to compare these data
sets, the effects of mergers must sets before they can be
removed from this data set. To do this, the method described in \cite{Gomez_2015} has been used. Supporting material consisting of graphs showing expected merger rates at various mass ratios and redshifts has also been prepared. compared.
The
main analysis of the first correction is for mergers. The local group data
was is based on galaxies that have not undergone mergers \textbf{is this true?}, while some of the distant galaxies will have. We make the merger correction to
do with the
error bars reported by \cite{Weisz_2014}. These errors follow SMF using the
conventions specified method shown in
\cite{Dolphin_2012} for systematic uncertainties and \cite{Dolphin_2013} for random. However, these uncertainties are extremely conservative and so instead we use the same convention \cite{Gomez_2015}. Supporting material such as
in \cite{Weisz_2014} which conservatively a relative uncertainty plots of
50\%. expected merger rates at various mass ratios and redshifts were also constructed to ensure that we were applying this correction correctly.
We also apply a correction
for mass loss to both the local group and \cite{Whitaker_2014}
data to account for mass loss. Both of data. As these
methods measure both determine mass by integrating the star formation rate over time, the data shows the total
stellar mass
of stars formed
in by a certain time, rather than the
galaxy and do not account for total stellar
death. mass present at that time. Much of this
death mass loss is
a result caused by the death of high mass, short lifespan
($ < 100Myr$) stars and so
we approximate this loss can be approximated as
instantanious with instantaneous using a multiplicative
factor of 0.64. As the factor. The \cite{Tomczak_2014}
data observes the determines mass
of the galaxy rather than calculating it by from observed luminosity and not star formation rates,
and so this
factor is not
needed applied there.
Finally, a morphological correction is applied to the local group data. Approximately 50\% of the known galaxies in the local group appear in this data set. However, if we divide these galaxies into those attached to the milky way, those attached to M31 (Andromeda) and those in the field, we find that we do not sample from these groups evenly. This correction weights each galaxy to account for this sub
sampling. sampling
The main analysis of the local group data was to do with the error bars reported by \cite{Weisz_2014}. These errors follow the conventions specified in \cite{Dolphin_2012} for systematic uncertainties and \cite{Dolphin_2013} for random. However, these uncertainties are extremely conservative and so instead we use the same convention as in \cite{Weisz_2014} which conservatively a relative uncertainty of 50\%.