MOS Scientific Applications Michael Balogh University of Durham
MOS Scientific Applications (mostly galaxy clusters) Michael Balogh University of Durham
Outline 1. Galaxy Clusters: scientific motivation
2. Canadian Network for Observational Cosmology (CNOC) 3. More clusters and groups with MOS 4. Ultra-plex spectroscopy: Ha spectroscopy of 4 clusters at z~0.4
5. Future considerations
Why Clusters?
Why clusters? 1. Very rare objects, in the tail of the mass distribution. So very sensitive to cosmology 2. Largest structures just virialising today, so we can study the process of structure formation 3. Extreme environments can affect galaxy properties
150 Mpc/h University of Durham
dalla Vechia, Jenkins & Frenk Institute for Computational Cosmology
A Press-Schechter plot showing the growth of the mass structure of the universe LCDM cosmology Rapid growth of structure
Groups Clusters Renormalised relative to 1011 M☼
Why Does Star Formation Stop? Steidel et al. 1999
Cluster environments inhibit star formation (Balogh et al. 1997; 1998)
Can the growth in the abundance of clusters explain the global decline of star formation?
Or is it related to internal galaxy properties?
Why MOS? Clusters are ideal targets for MOS because: 1. high density of galaxies 2. close in velocity space, so can use narrow wavelength range to increase multiplex 3. Learn about cluster dynamics and galaxy properties from the same set of spectra
CNOC: Cluster masses
CNOC: Goals Sample: 15 X-ray luminous clusters from EMSS, 0.21
Groups at z > 1 1. Deep multicolour (VRi′z′JKs) images of Lynx and Q1335+28 (z=1.2). 2. Proposals to observe high redshift radio galaxies and radio-loud quasars: known to reside in dense environments • IRIS2 narrow band Ha and [OIII] at z=2.3 • GMOS/FORS2 narrow band filter + grism Ha and [OII] spectroscopy at z=1.4, 1.47, 2.3
Lynx clusters: z=1.2 Subaru VRi’z’ INGRID JKs
Y (arcmin)
Identified 7 groups around the clusters from photometric redshifts. GMOS spectroscopy pending
X (arcmin)
Nakata et al. (2002)
Overdensities around HizRG
z=1.44
z=1.59 Best et al. 2003
Conclusions 1. Clusters and groups have a large impact on galaxy star formation rates at the present day 2. Need to understand how cluster populations evolve to disentangle internal and external effects 3. MOS at high redshift essential. Nod-and-shuffle required to work at red wavelengths, but need full field of view.