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STS426 Tanuka C.

Study on star formation history of nearby
galaxies
Tanuka Chattopadhyay
Department of Applied Mathematics, University of Calcutta.

Abstract
Star formation scenario in galaxies of various morphological types is
significant in a sense that it characterizes the structure formation in the
Universe. Star formation Rate (SFR) is an important index to study the above
phenomenon. But direct measurement of (i.e., True values of SFR) is
not at all possible as one has to count stars formed per year in a galaxy
accurately. In this paper the star formation is investigated by Gaussian Mixture
Model Based Clustering technique (GMMBC) to form the clusters of the
galaxies (using a large data set of galaxies in the Local Volume (LV)) and the
groups are discussed.

Keywords
SFR; Bayesian Analysis; Bayesian LASSO; GMMBC

1. Introduction
During the past few decades, cosmology has progressed a lot, though
galaxy formation is far from completeness. It is the great unsolved problem in
modern astrophysics. Galaxy formation can be properly delineated if the
corresponding star formation history can be explored in greater detail. From
current observations it is speculated that galaxy formation and evolution is
strongly influenced by environment e.g., star formation activity is reduced in
high density environment (?; ?; ?; ?). In addition gas density plays an important
role. In fact a quantitative measurement of the relation between SFR and gas
density evolution. It gives the clue that how efficiently gas is turned into stars
and hence an essential input to simulations models of galaxy formation (?; ?;
?). Another important parameter driving galaxy evolution is the stellar mass of
galaxies. There is correlation between SFR and stellar mass in local (?; ?) as well
as distant Universe (?; ?; ?). ? have analyzed specific star formation rate (sSFR)
for SDSS galaxies of different masses and redshift and they differ in massive
and dwarf galaxies. ? have studied the star formation history of dwarf galaxies
and traced out SFH as a function of galactocentric radius. He found contrast
in SFH for dSph from dwarf transition types (dTr).
Now SFR is the number of stars formed per year. This is not possible to
measure SFR directly by counting stars in a galaxy (i.e., SFRtrue). Hence another
aspect is to properly quantify SFR of a representative galaxy. It is important to

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