Extragalactic abstracts - IRSA - California Institute of Technology
Extragalactic abstracts - IRSA - California Institute of Technology
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 />
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