Spectroscopic Indicators of Galaxy Evolution: Early-type Galaxies in Cl at z~0.4 Sean Moran Ge/Ay 132

Large Scale Surveys of Cl (z~0.39) and MS (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 L X of Cl0024

Morphology-Density and 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)

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?

[OII] Emission from [OII] 3726, 3729Å can indicate ongoing star formation (HII regions near O, B stars) Transitions from: 2 D 3/2 -> 4 S 3/2 2 D 5/2 -> 4 S 3/2 Also prominent in AGN (Osterbrock 1989)

[OIII] Emission from [OIII] 4959Å, 5007Å can also indicate star formation Transitions from: 1 D 2 -> 3 P 2 1 D 2 -> 3 P 1 Additional transition at 4363A too weak at these distances ( 1 S 0 -> 1 D 2 ) Also in AGN (Osterbrock 1989)

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

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

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.