Extragalactic abstracts - IRSA - California Institute of Technology

Spitzer_Approved_Extragalactic
Mar 25, 10 16:24 Page 353/742
Spitzer Space Telescope − Archive Research Proposal #20543
Detecting Clusters of Galaxies at 1 < z < 2 in the SWIRE Legacy Fields.
Principal Investigator: Gillian Wilson
Institution: Caltech
Technical Contact: Gillian Wilson, Caltech
Co−Investigators:
Mike Gladders, Carnegie Observatories
Henk Hoekstra, University of Victoria
Mark Lacy, Caltech
Adam Muzzin, University of Toronto
Jason Surace, Caltech
Howard Yee, University of Toronto
Science Category: high−z galaxies (z>0.5)
Dollars Approved: 57232.0
Abstract:
We propose to apply an infrared adaptation of the two−filter Cluster
Red−Sequence (CRS) technique to detect a large (500−1000) sample of clusters at
1.0 < z < 1.8 in the 50 square degree SWIRE Legacy Survey. We hope to discover
the elusive population of "young" clusters, the "missing−link" in the evolution
of proto−clusters discovered at z > 2 to the mature population found at z < 1.
In addition to providing a huge boost to cluster evolution studies, discovering
this elusive population would also be crucial to our "big picture" of
observational cosmology. For example, the evolution of the cluster mass function
N(M, z) can place strong constraints on the equation of state of the mysterious
dark energy. We have already applied the CRS technique successfully (albeit with
a non−optimal filter combination) to the Spitzer First Look Survey and find it
to be a very powerful and efficient new tool for detecting clusters of galaxies
at high redshift. The CRS technique has the huge additional advantage, not only
of detecting clusters in this redshift regime, but of providing very accurate
redshifts for the clusters, based solely on the color of their passively
evolving red sequence. We plan to release our final catalog as soon as possible.
Such a catalog of homogeneously selected clusters in this unexplored redshift
range would provide an invaluable resource to the cluster community and would
undoubtedly result in numerous follow−up studies. Our Spitzer cluster catalog
will also lay the groundwork for future Sunyaev−Zeldovich telescopes capable of
detecting > 10,000 cluster candidates at z > 1 but which will require the
clusters to be followed up using a CRS technique to determine a photometric
redshift. This very unique project can currently only be achieved with the SWIRE
dataset (area is vital because rich clusters are so rare). Our project will
contribute to Spitzer’s legacy by providing substantial returns to the entire
cluster community at very little cost.
Spitzer_Approved_Extragalactic
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Spitzer Space Telescope − General Observer Proposal #20629
Characterize the 24micron Population with Systematic IRS Sepctroscopy
Principal Investigator: Lin Yan
Institution: Caltech
Technical Contact: Lin Yan, Caltech
Co−Investigators:
George Helou, SSC/Caltech
Lee Armus, SSC/Caltech
Tim Heckman, University of Johns Hopkins
Harry Teplitz, SSC/Caltech
Bruce Draine, Princeton University
Dario Fadda, SSC/Caltech
Phil Choi, SSC/Caltech
Dave Frayer, SSC/Caltech
Anna Sajina, University of British Columbia
Science Category: high−z galaxies (z>0.5)
Observing Modes: IrsStare
Hours Approved: 181.0
Abstract:
With its exquisite sensitivity, the 24um band has yielded the most valuable data
on obscured star formation at cosmological distances, and the IRS has
demonstrated its diagnostic power by detecting Aromatic Features out to z ~ 2
(Yan et al 2005). Understanding the 24um population can only be achieved with
systematic spectroscopy at the mid−IR, coupled with secure redshifts and
diagnostics from optical spectra. We propose IRS spectroscopy at 7−38um of an
unbiased sample of 159 sources from the First Look Survey (FLS) for which
optical spectra are or will be available. These targets have 24um flux density
greater than 0.9mJy, and are selected to be representive of infrared galaxies
over a wide redshift range. The proposed spectra will provide an essential
library for interpreting enormous amount of mid−IR imaging data from Spitzer,
then WISE and JWST; we waive the proprietary period, and will release the
reduced 1D specrta to the public archive. This unbiased datset will allow us to
determine how the energy output from PAH emission in dusty starbursts changes as
a function of luminosity and redshift. We will also estimate the relative
frequencies of AGN, starburst and composite systems, thus deriving the true
obscured star formation density. Utilizing a rich variety of mid−IR spectral
diagnostics, including continuum slopes, line and PAH ratios, the strength of
PAH emission and silicate absorption, we will study in detail the physical
conditions of the ISM in galaxies with intense star formation and AGN activities
in early cosmological epochs, and understand the dust emission processes which
build both galaxies and blackholes.
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