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Spectroscopic Indicators of Galaxy Evolution:

Spectroscopic Indicators of Galaxy Evolution:. Early-type Galaxies in Cl0024+16 at z~0.4. Sean Moran Ge/Ay 132. Large Scale Surveys of Cl0024+17 (z~0.39) and MS0451-03 (Z~0.54). Cl0024: 39 sparsely sampled WFPC2 images, to 5 Mpc Spectra of over 200 members MS0451:

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Spectroscopic Indicators of Galaxy Evolution:

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  1. Spectroscopic Indicators of Galaxy Evolution: Early-type Galaxies in Cl0024+16 at z~0.4 Sean Moran Ge/Ay 132

  2. Large Scale Surveys of Cl0024+17 (z~0.39) and MS0451-03 (Z~0.54) • Cl0024: • 39 sparsely sampled WFPC2 images, to 5 Mpc • Spectra of over 200 members • MS0451: • Full coverage with 40 ACS pointings; in progress • Complimentary cluster: ~8x LX of Cl0024

  3. Morphology-Densityand Environmental Processes • Mix of galaxy types depends on where you look • More Ellipticals in cluster centers • Clusters: laboratories to study galaxies over a large range of Σ • Chicken or Egg: • initial conditions (E/S0 form in initially denser regions) • environmental processes (galaxies are transformed by environment as they fall into denser regions.) Treu et al. (2003)

  4. Environmental Processes • Spectral Properties as fn of radius to disentangle these processes • First results on Cl0024: look at Early type galaxies: [OII], [OIII], Hγ, Hδ • Are there abrupt and/or gradual changes in galaxy properties?

  5. [OII] (Osterbrock 1989) • Emission from [OII] 3726, 3729Å can indicate ongoing star formation (HII regions near O, B stars) • Transitions from: 2D3/2->4S3/2 2D5/2->4S3/2 • Also prominent in AGN

  6. [OIII] (Osterbrock 1989) • Emission from [OIII] 4959Å , 5007Å can also indicate star formation • Transitions from: 1D2->3P2 1D2->3P1 • Additional transition at 4363A too weak at these distances (1S0->1D2) • Also in AGN

  7. Hγ, Hδ • Hydrogen Balmer absorption may indicate recent star formation: • A and F stars relatively short-lived, but exhibit strong Balmer lines • Balmer emission may indicate either AGN activity or more HII regions from O, B stars. • Line ratios help distinguish

  8. AGN show emission in Hγ, sometimes in Hδ • For non-AGN, EW of lines increases w/ radius • Population of early types shows some star formation at edge of cluster

  9. Conclusions • Via [OII], [OIII], we identify AGN within a narrow range in cluster radius • [OII], Hγ, Hδ EWs increase outward: some early types undergo ‘gentle’ interaction with cluster environment • Will want to see if the trends in spectral features of spiral galaxies are as abrupt as we see for early types.

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