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Extragalactic abstracts - IRSA - California Institute of Technology

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Spitzer_Approved_<strong>Extragalactic</strong><br />

Mar 25, 10 16:24 Page 613/742<br />

Spitzer Space Telescope − General Observer Proposal #20451<br />

A Mid−Infrared Survey <strong>of</strong> Gravitational Lenses<br />

Principal Investigator: Christopher Kochanek<br />

Institution: The Ohio State University<br />

Technical Contact: Christopher Kochanek, The Ohio State University<br />

Co−Investigators:<br />

Nicholas Morgan, The Ohio State University<br />

Xinyu Dai, The Ohio State University<br />

Emilio Falco, Smithsonian Astrophysical Observatory<br />

Science Category: galaxy clusters and groups<br />

Observing Modes: IracMap<br />

Hours Approved: 8.7<br />

Abstract:<br />

We will use mid−IR IRAC images <strong>of</strong> six gravitational lenses to understand a basic<br />

problem <strong>of</strong> gravitational lenses −− why simple lens models explain the image<br />

positions but not the image fluxes. We know from models <strong>of</strong> lensed quasar host<br />

galaxies observed by HST that the problem does not lie in our models for the<br />

gravitational potential <strong>of</strong> the main lens galaxy. For optical and near−IR data,<br />

the explanation can be propagation effects (dust), microlensing by stars in the<br />

lens galaxy, or what is known as cold dark matter (CDM) substructure<br />

(satellites) <strong>of</strong> the lens galaxy. The mid−IR fluxes are immune to both dust and<br />

microlensing −− the wavelength is to long to be bothered by dust and the<br />

emission region is to large to be bothered by microlensing. If the mid−IR flux<br />

ratios are still unexplained by simple lens models, the cause must be the<br />

predicted (and much debated) CDM substructure. Thus, the SST/IRAC observations<br />

will provide a simple test <strong>of</strong> a basic prediction <strong>of</strong> cold dark matter models for<br />

the formation <strong>of</strong> galaxies.<br />

Spitzer_Approved_<strong>Extragalactic</strong><br />

Printed_by_SSC<br />

Mar 25, 10 16:24 Page 614/742<br />

Spitzer Space Telescope − General Observer Proposal #50342<br />

Exploring the Web : Galaxy Evolution in High−Redshift Superclusters<br />

Principal Investigator: Lori Lubin<br />

Institution: University <strong>of</strong> <strong>California</strong><br />

Technical Contact: Lori Lubin, University <strong>of</strong> <strong>California</strong><br />

Co−Investigators:<br />

Brian Lemaux, UC Davis<br />

Dale Kocevski, UC Davis<br />

Christopher Fassnacht, UC Davis<br />

Roy Gal, <strong>Institute</strong> for Astronomy<br />

Neal Miller, JHU<br />

Gordon Squires, SSC/Caltech<br />

Mark Lacy, SSC/Caltech<br />

Jason Surace, SSC/Caltech<br />

Science Category: galaxy clusters and groups(high−z)<br />

Observing Modes: IracMap MipsScan<br />

Hours Approved: 32.8<br />

Abstract:<br />

We propose deep IRAC and MIPS mapping <strong>of</strong> the Cl 1324 supercluster at z = 0.7<br />

which contains 7+ clusters and extends 22 Mpc x 100 Mpc. The supercluster is<br />

already the subject <strong>of</strong> a multi−faceted program including (1) deep r’i’z’JK<br />

imaging from the Palomar 5−m and UKIRT 3.8−m to measure optical/near−IR colors,<br />

(2) spectroscopy with DEIMOS on the Keck 10−m to measure stellar content and<br />

[OII] emission for over 400 supercluster members, and (3)<br />

high−angular−resolution Chandra and VLA observations to study the starburst and<br />

AGN populations. Based on comparisons with our well−studied (in the optical,<br />

mid−IR, radio, and X−ray) and similarly−sized Cl 1604 supercluster at z = 0.9,<br />

we find significant evolution over only ~1 Gyr, with substantially smaller<br />

contributions from [OII]−emitting and starburst galaxies in the Cl 1324<br />

supercluster. Because dust will severely bias measurements made in the optical,<br />

we require 3.6−24 micron observations to measure accurately stellar mass, star<br />

formation rate, and nuclear/starburst activity in the member galaxies and<br />

determine the true extent <strong>of</strong> evolution over this timescale. With the combined<br />

observations <strong>of</strong> the Cl 1324 and Cl 1604 superclusters, we have the unique<br />

opportunity to constrain the effect <strong>of</strong> large scale environment on galaxy<br />

evolution, the physical mechanisms responsible for fueling starburst and nuclear<br />

activity, and the timescales <strong>of</strong> gas quenching and black−hole accretion.<br />

Thursday March 25, 2010 xgal_covers.txt<br />

307/371

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