CCAPP Seminar: "Dwarf Galaxy Archaeology with the r-process Galaxy Reticulum II" Alex Ji (MIT)

December 5, 2016
Tuesday, October 4, 2016 - 11:30am to 12:30pm
PRB 4138
Oval

Detailed chemical abundances of metal-poor stars offer an observational window to the era of first stars and galaxies. Ultra-faint dwarf galaxies contain a coherent population of metal-poor stars, providing important environmental context to this record of early chemical enrichment. I will present an example of dwarf galaxy archaeology with the ultra-faint dwarf galaxy Reticulum II. Seven of nine stars in this galaxy display extremely enhanced r-process abundances 2-3 orders of magnitude higher than in the other ultra-faint dwarfs. Stars with such extreme r-process enhancements are only rarely found in the Milky Way halo. The r-process abundances imply that the neutron-capture material in Reticulum II was synthesized in a single prolific event, possibly a neutron star binary merger or a magnetically driven supernova. The single r-process enrichment event also provides a unique probe of the star formation and metal mixing history of this galaxy. Reticulum II illustrates how continued observations of faint dwarf galaxies can constrain the very high-redshift universe.

S M T W T F S
1
 
2
 
3
 
4
 
5
 
6
 
7
 
8
 
9
 
10
 
11
 
12
 
13
 
14
 
15
 
16
 
17
 
18
 
19
 
20
 
21
 
22
 
23
 
24
 
25
 
26
 
27
 
28
 
29
 
30
 
31