L10-- stellar pop Flashcards
luminosity relation?
L= 4 pi stephan boltzman const * R^2 * T_eff^4
HRD types?
classical: M_abs vs spectral type
CMD: M_abs vs colour
kiell dig: log g (surface grav) vs T_eff
HRD evo track?
line/ track of same IMF diff ages/ evo track based on IMF of star
each point on evo track: life/ stage of star
lines defining the age of a star?
isochrones on HRD
effect of metallicity on evo track?
same mass diff meta; slightly diff path
identify main seq turn off point
MSTO: star leaving MS, highest T_eff on isochrone (bluest)
IMF? mean? formula? units
HMS / #LMS
dist of stellar mass in a cluster
IMF = 1/N dn/dm
[IMF] = per mass interval
logithrimic IMF?
formula?
1/N dn/d_mu
mu= log(m/solar_m)
parameterization of IMF? 2 methods?
two standard parametrisations are currently broadly used: A segmented power law with mass-dependent slopes (Kroupa et al. 1993), and a lognormal distribution (Chabrier 2003)
why IMF cant be measured directly?
masses not observables
HMS– short life– not represented
stellar pop types: SSP, CSP meaning? comparison of age/ metallicities/ isochrone?
SSP: group of stars formed by single gas cloud: same age, same metallicity, diff mass
CSP: superposition of multiple SSPs of different ages and possibly abundances, weighted by their respective mass fractions.
what do SP tells?
S Mass
SFR
SF history
S metallicity
metallicity of each element
why should IMF follow Gaussian dist?
central limit th:
sum of an infinite number of independent variables can be described by a normal or gaussian distribution function
SF: v complex, many variables
log-m is the sum of a series of possibly independent distribution functions. If the series is infinite and the variables are truly independent, we can then expect the distribution of log-m to follow a gaussian form.
challenges in calc IMF?
star count
PDMF
challneges in calc IMF: star count?
LMS»_space; # HMS
so v large sample is req to inc HMS
challenges in calc IMF: PDMF
stars lifetime finite, sample has stars of diff lifetimes: need to take IMF of present time
HMS have v short lifetime, so when taking PDMF: a lot of HMS wont be in the PDMF
PDMF doesn’t correctly represent HMS population then
High mass breakpoint and low mass breakpiunt reasons in IMF?
x
8 parameters of IMF?
in paper
what defines mass limit?
x
are mass limit and breakpoint diff?
x