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Galaxy Evolution in Supercluster SG1120: Insights from Hierarchical Assembly

Explore the evolution of galaxies in SG1120 supercluster using hierarchical assembly methods and redshift confirmations. Understand morphological changes, star formation rates, and galaxy interactions within this unique system. Uncover the mass distribution and dynamics of member groups in preparation for future cluster formation.

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Galaxy Evolution in Supercluster SG1120: Insights from Hierarchical Assembly

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  1. Life Before the Fall:Group Galaxy Evolution Prior to Cluster Assembly Anthony Gonzalez (Florida) Kim-Vy Tran (CfA) Michelle Conbere (Florida) Dennis Zaritsky (Arizona) John Moustakas (Arizona)

  2. Hierarchical Assembly: SG1120 • Detection: • Las Campanas Distant Cluster Survey (Gonzalez et al. 2001) • 4 candidates at z~0.4 within a 7’ diameter region • Confirmation: • Chandra + spectroscopy • 6 extended sources within a 13’ diameter region (~4 Mpc) Groups at z=0.37 (2,3,4,5) Cluster at z=0.48 (1) No redshift yet (6) • “Supergroup” SG1120-1202 Ringberg Workshop - October 25, 2005

  3. Hierarchical Assembly: SG1120 3 VLT BVR Imaging 4 Ringberg Workshop - October 25, 2005

  4. Spectroscopic Confirmation VLT Spectroscopy 101 confirmed members Ringberg Workshop - October 25, 2005

  5. Redshift Distribution Dispersions All 62050 km/s Group 3 37080 km/s Group 4 45080 km/s Group 5 56090 km/s Merging Galaxy Groups ``Virialized’’ Halos Gonzalez et al. 2005 Ringberg Workshop - October 25, 2005

  6. Mass and Dynamics • Mass • Tx (sum of individual groups 2-5): 5x1014 M - lower limit • Dynamical Analysis • Gravitationally bound • Should merge by z~0 • Additional velocities for groups 2,6 will refine this constraint Should evolve in to a Coma-ish cluster by z=0 Ringberg Workshop - October 25, 2005

  7. Galaxy Evolution in Groups Coma Cluster (z~0.02) SG1120 (z=0.37) Coma Progenitor Ringberg Workshop - October 25, 2005

  8. Galaxy Evolution in Groups • Key Questions • Morphological Evolution • Quenched/Enhanced Star Formation • E+A’s • Fraction of star-forming galaxies; total star formation rate • Galaxy Mass Assembly • HOD • Interaction Rate • Wet/Dry Mergers • Relation of above quantities to local density and galaxy mass Ringberg Workshop - October 25, 2005

  9. Galaxy Evolution in Groups • Method • Morphological Evolution (ACS - 10 orbit F814 mosaic) • Quenched/Enhanced Star Formation • E+A’s (VIMOS spectra, MIPS 24 m) • Fraction of star-forming galaxies; total star formation rate • Galaxy Mass Assembly (BVRJKS, ACS+WFPC2) • HOD • Interaction Rate • Wet/Dry Mergers • Relation of above quantities to local density and galaxy mass (Chandra, ACS, BVRJKs imaging, MIPS, spectroscopy) Ringberg Workshop - October 25, 2005

  10. Color-Magnitude Diagram Established Red Envelope Retains Population of Starforming Galaxies Intermediate between Field/Clusters Foreground/Background F Ringberg Workshop - October 25, 2005

  11. Passive Fraction Pre-processing 618% passive - Roughly twice as many as field (same z) Ringberg Workshop - October 25, 2005

  12. Member Galaxies and Interactions Ringberg Workshop - October 25, 2005

  13. Summary • SG1120 is a confirmed “supergroup” at z=0.37 • Gravitationally bound system • 4-5 member groups within target region • Direct view of progenitors of massive cluster • Well-defined red envelope • Strong correlation between surface density and passive fraction • Ongoing mergers of massive galaxies, high merger fraction Ringberg Workshop - October 25, 2005

  14. Work in Progress • ACS Mosaic (10 orbit F814W) • Morphological fractions and morphology-density relation • Interaction rate • MIPS - dusty star formation • Additional spectroscopy • E+A fraction • Fundamental plane • Finish mapping superstructure • ACS+Chandra+spectra • Cross-correlation between local density and X-ray surface brightness • SED and morphology vs X-ray surface brightness • Comparison with properties of both local clusters (Coma) and CL 1358 (z=0.33) Ringberg Workshop - October 25, 2005

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