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Stellar Pop in Galax, Other - Coggle Diagram
Stellar Pop in Galax
Single stellar population
single age
single Z
initial mass function (IMF)
lead us from gas to stars
should analyze that inversely to understand
process
make a count - mass diagram by obs
Fromation
\( \phi(m) = \frac{dn}{dlog m} \sim m^{\Gamma}\)
there slopes
Salpeter = 1.35
Botom heavy = more slope salpeter
Lots of low mass stars
Massive galax indicative
top heavy = less slope Salpeter
More massive stars
In other Galax
only MW directly possible
Spectral features
Dynamical studies
dynamical model
get stellar mass from stellar populations
compare to M/L and M/L*
Cosmic IMF
By UV and IR analysis
total mass
can convert all the gas into stars
Spectral energy dist (SED)
temp
surface gravity
chemical composition
Spectral Lib
empirical
Synthesis
need them to build SED
Build SED -SSP
\(F_{\lambda} (t) = \int_0^{t'} \psi(t')S_\lambda(X_i,t-t')dt\)
Isochrones
IMF
spectral lib
Estimate stellar mass
our final intention
total baryonic mass
mass of starts and remnants
mass of living stars
M/L realated to 3 factors
age
Z
star-formation history
By colour
By SED
spectroscopy
Galax composition
stars
gas
mass distribution
80 - 90 %
baryons
Determining ages and Z of Galax
It is an inherent part of stars not galax
we add start contribution to one spectra to build it
need SSP spectra
approaches
color-mag diagrams
measure the color and go for age
old pop is redder
:heavy_minus_sign: con't distinguish bet:
olde - Z poor
young - Z rich
But by filter we avoid it
spectral indices
full Spectral fitting
Stellar evo track
M as F(age)
sophisticated modelling
stellar
stellar isochrone
shows location of stars with different masses be at a given age
Stellar Pop and Galax
2 types
blue cloud
red sequence
:star: between type so-called
green valley
galax evolve from blue to old red
combi stellart astor + galax creation
Other
Qustions: