Maurizio Salaris
Astrophysics Research Institute – Liverpool John Moores University
EaHS12 - Oxford
constraints on EOS of dark energy
constraints on galaxy formation (and
chemical evolution) models
characterize the evolutionary scenario of
the parent planetary population
First GC ages :
~3.5 Gyr (Sandage & Schwarzschild 1952)
6 ± 2 Gyr (Hoyle & Schwarzschild 1955)
Theoretical tools from stellar evolution theory
Ages from star cluster CMDs
Ages from field star CMDs
Ages from eclipsing binaries
Isochrones
The value of the
stellar mass around
the TO and along the
RGB is a function of
age, for a fixed initial
chemical composition
50 million yr
100 million yr
500 million yr
1 billion yr
5 billion yr
10 billion yr
Collaboration: Bedin, King, Anderson, Piotto, Salaris, Cassisi
GLOBULAR CLUSTER
AGB
HB
The Turn Off
MS
RGB
OPEN CLUSTERS
Isochrone fitting
~ 4 Gyr
Colours are not
predicted
accurately enough
template
Magnitude
“Absolute”
methods
Example of
MS-fitting
distance
determination
m-M
cluster
colour
Distance
fixed
Age from TO
absolute
magnitude
Differential methods
Phelps et al. (1994)
dΔ(B-V)/dt ~ 0.01 mag/Gyr
dΔV/dt ~ 0.1 mag/Gyr
Salaris & Weiss (2002)
Salaris et al. (2004)
Age (ΔV) reference clusters fixes age scale
Reference clusters
MS-fitting based
age
revised
Globular
clusters
Old open
clusters
Is atomic diffusion efficient in
globular cluster stars ?
Vandenberg
et al. (2002)
”
Ages from WD cooling sequences
Ingredients: WD cooling models – Initial-final mass relationship –
progenitor models
Salaris et al. (2010)
t(iso)=t(WD)+t(prog)
DA
DB
WD luminosity functions
WD LF for simple
stellar populations of
3, 6, 8 Gyr and
[Fe/H]=0.0
Larger age, fainter
peak
Age sensitivity MS Turn-Off
1213 Gyr Δ(F606W) ~0.1
23 Gyr Δ(F606W) ~0.4
The distance has
to be fixed
Bedin, Salaris et al.
(2009)
M4
11,12,13
Gyr
11,11.6,12,
13 Gyr
M67
Bellini et al. (2010)
3.75 , 4.0 Gyr
Isochrones
FIELD STARS
Schuster & Nissen
(1989)
Schuster et al. (1996)
Salaris & Weiss (2001)
The role played by
the efficiency of
diffusion
Jofre & Weiss
(2011)
SDSS data
Determination of
TO colour
Edge detection algorithm to
determine the colour of the MS
turn off
Field halo stars and GCs
appear to have the same
age
Age estimate
Bruntt et al. (2011)
ECLIPSING BINARIES
NGC 6791
Age-rotation-activity relationship
Needs calibration
Chromospheric activity is powered by rotation in the
presence of a deep convective envelope. Because of
rotation braking by a magnetised stellar wind,
rotational velocity decreases with age, as well as
activity, unless the angular momentum is sustained by
tidal interaction, as in the case of short-period
binaries. This simple picture is at the basis of the so
called age-activity-rotation relationship in solar-type
stars.
Pace & Pasquini
(2004)