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Life Before the Fall: Group Galaxy Evolution Prior to Cluster Assembly

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). Hierarchical Assembly: SG1120. Detection:

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Life Before the Fall: Group Galaxy Evolution Prior to Cluster 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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