Exploring the orbits of the stars from a blind chemical tagging experiment. Borja Anguiano Macquarie University, Sydney, Australia. Siblings, siblings, siblings…everywhere !. Star formation. Stars form in molecular clouds (HII) when denser parts core collapse under their on gravity.
Exploring the orbits of the stars from a blind chemical tagging experiment
Macquarie University, Sydney, Australia
New second generation from massive stars
Presence of radioactive-isotopes in primitive meteorites, the Sun was polluted by a SN of star about 15-25 solar masses within a distance of 0.02-1.6 pc (Looney et al. 2006).
Chemical information remains preserved in an open cluster (De Silva et al. 2007, Sestito et al. 2007) -> RECALL D. Yong’s talk about inhomogeneities in Open Clusters
“Spectroscopic survey of about a million stars, aimed at using chemical tagging techniques to reconstruct the star-forming aggregates that built up the disk, the bulge and halo of the Galaxy”
Goal: Using element abundance information from field stars to search for co-natal groups
C = chemical species
Ac = [X/Fe]
See A. Mitschang et al. 2012 for more details
Bensby, T.; Feltzing, S.; Oey, M. S. 2014
O, Na, Mg, Al, Si, Ca, Ti, Cr, Fe, Ni, Zn, Y, and Ba for 714 nearby F and G dwarf stars.
Random errors ~0.05 dex
Using a principal component analysis on chemical abundances spaces Ting et al. 2012 concluded that the [X/Fe] chemical abundance space in the solar neighbourhood has about six independent dimensions
Why so many -in such a small volume- ?
– Groups are highly contaminated
– Open clusters are not good representatives
– Galactic mixing is weak
– Groups are not co-natal stars, just co-eval
See A. Mitschang et al. 2014 for more details
B. Anguiano PhD thesis 2012
Edvardsson et al. 1993
Mitschang et al. 2014
Bensby et a. 2014 calculated the Galactic orbits using the GRINTON integrator (Bedin et al. 2006)
- Minimum and maximum distances from the Galactic centre –peri and apocentric values (Rmin,
- Maximum distance from the
Galactic plane, Zmax
- Eccentricity, Etot, Lz
IDEA: Use coeval groups identified in Mitschang et al. 2014 using the data set from Bensby et al. 2014 to explore the evolution of the stellar orbits parameters with time
Coeval groups with more than 5 members -> A total of 45 groups to play with.
Dots: mean value for Rmax, Rmin for a given group, error bars: standard deviation of the group.
Rmin is more sensitive to the angular momentum than Rmax
Mean <e> of the coeval groups increase with age. The dispersions is significant. e > 0.3 range from 2 to 10 Gyr…
We find an age relation with respect to the mean maximum distance from the Galactic plane for the computed orbits of the coeval groups. However note the scatter, there are old stars with low Zmax values
Age vs <Lz>
Age vs. σL