Transformation of Star-bursting Galaxies in Galaxy Clusters

Understanding the transformation of populations in galaxy clusters has been one of the challenges of galaxy evolution over the past several decades. The extreme environments, especially of the most massive clusters, are known to affect how galaxies evolve such that the populations of local galaxy clusters are very different from those in other environments. To help understand these populations, we have performed a detailed study on a type of star bursting galaxies seen predominately at intermediate redshifts in galaxy clusters: luminous compact blue galaxies. By looking at the distribution, kinematics, and spectral properties of these galaxies, it does appear that we are seeing the final star-burst from the progenitors of dwarf elliptical galaxies that dominate the populations of nearby galaxy clusters.

Transcript

1. Transformation of Star-bursting Galaxies in Galaxy Clusters Steve Crawford SAAO Collaborators: Matthew Bershady (U. Wisconsin), Greg Wirth (Keck Observatory), Solohery Randriamampandry (U. KwaZulu-Natal) Thursday, October 1, 15
2. Abel 1689 (HST) Thursday, October 1, 15
3. Abel 1689 (HST) Wolf et al. 2005 Thursday, October 1, 15
4. Abel 1689 (HST) Thursday, October 1, 15
5. Abel 1689 (HST) Thursday, October 1, 15
6. Abel 1689 (HST) Gomez et al. 2003 Thursday, October 1, 15
7. Abel 1689 (HST) Thursday, October 1, 15
8. Abel 1689 (HST) Jerjen Thursday, October 1, 15
9. Blue fraction Butchler & Oemler 1984 Haines et al. 2009 Thursday, October 1, 15
10. Build-up over time Dressler et al. 1998 Spirals transform into S0 Thursday, October 1, 15
11. Build up over time de Lucia et al. 2004 Thursday, October 1, 15
12. Transformations and Timescale Ram pressure stripping, starvation, mergers, pre- processing What are the timescales and dominant modes for transformation? Kenney et al. 2004 Thursday, October 1, 15
13. Populations −24 −22 −20 −18 −16 −1 0 1 M B (U−B) 0 RCX GV BCX −.5 0 .5 1 1.5 26 24 22 20 18 16 (B−V) 0 µ e (B) 0 LCBG Red Sequence Galaxies Green Valley Galaxies Blue Cloud Galaxies Thursday, October 1, 15
14. LCBGs −16 −.5 0 .5 1 1.5 26 24 22 20 18 16 (B−V) 0 µ e (B) 0 LCBG Luminous Compact Blue Galaxies s Compact Blue alaxies ing ies 0), se • Rapidly evolution population of galaxies (factor of ~10 drop since z~1) • Luminous (MB ~ -20), small (re ~2 kpc), and intense star formation rates (100x Milky Way) Thursday, October 1, 15
15. Observations Deep narrow band imaging combined with DEIMOS spectra Archive data from HST, Spitzer, VLA Thursday, October 1, 15
16. Thursday, October 1, 15
17. Clusters Triggering LCBGs Density of Cluster Galaxies Density of field galaxies Enhancement = Enhancement of LCBGs arison between giant galaxies, iral galaxies enhancement imilar to dE or ype galaxy. cantly different e spiral ution. Thursday, October 1, 15
18. Clusters Triggering LCBGs Density of Cluster Galaxies Density of field galaxies Enhancement = Thursday, October 1, 15
19. Clusters Triggering LCBGs Density of Cluster Galaxies Density of field galaxies Enhancement = Thursday, October 1, 15
20. Thursday, October 1, 15
21. LCBGs are different Thursday, October 1, 15
22. LCBGs are different Thursday, October 1, 15
23. LCBGs are different Combine with spatial distribution and GV, BC, and LCBGs avoid center Thursday, October 1, 15
24. Substructure Dressler-Shectman statistic is the classic test for substructure: Calculated as the offset from the cluster mean for the 10 nearest neighbors Thursday, October 1, 15
25. Different Scales Green valley galaxies show a similar substructure as red sequence galaxies, but LCBGs show a strong peak at small numbers Thursday, October 1, 15
26. Different Scales Green valley galaxies show a similar substructure as red sequence galaxies, but LCBGs show a strong peak at small numbers Thursday, October 1, 15
27. Different Scales Green valley galaxies show a similar substructure as red sequence galaxies, but LCBGs show a strong peak at small numbers Thursday, October 1, 15
28. Different Scales Green valley galaxies show a similar substructure as red sequence galaxies, but LCBGs show a strong peak at small numbers Thursday, October 1, 15
29. Merging Together Thursday, October 1, 15
30. Spectroscopic Properties Thursday, October 1, 15
31. Fate of LCBGs Thursday, October 1, 15
32. Fate of LCBGs Thursday, October 1, 15
33. Fate of LCBGs Thursday, October 1, 15
34. Fate of LCBGs Thursday, October 1, 15
35. Fate of LCBGs Thursday, October 1, 15
36. Fate of LCBGs Local cluster dE LF Thursday, October 1, 15
37. Young burst in dE Rys et al. 2015 Rys et al. showed that the typical dE had a burst of star formation ~5 Gyrs ago Thursday, October 1, 15
38. Summary • Galaxy Clusters trigger the star burst phase at intermediate redshifts • LCBGs are falling into clusters as pairs and small groups • Spectral properties of LCBGs are very similar to local, cluster dE • Likely between 30-75% of dE experienced a dE phase in the last 7.5 Gyrs Thursday, October 1, 15
39. Star formation in LCBGs Thursday, October 1, 15
40. Green Valley Galaxies Heterogeneous class of objects that look to be intermediate between the blue cloud and the red sequence Schawinski et al. 2014 Thursday, October 1, 15