Paper: astro-ph/0510194
Date: Thu, 6 Oct 2005 21:07:47 GMT (9kb)

Title: Dark Energy Studies: Challenges to Computational Cosmology

Authors: James Annis, Francisco J. Castander, August E. Evrard, Joshua A.
Frieman, Enrique Gaztanaga, Bhuvnesh Jain, Andrey V. Kravtsov, Ofer Lahav,
Huan Lin, Joseph Mohr, Paul M. Ricker, Albert Stebbins, Risa H. Wechsler,
David H. Weinberg, Jochen Weller (theory members of the DES collaboration)

Comments: 5 pages, theory white paper submitted to the Dark Energy Task Force
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The ability to test the nature of dark mass-energy components in the universe
through large-scale structure studies hinges on accurate predictions of sky
survey expectations within a given world model. Numerical simulations predict
key survey signatures with varying degrees of confidence, limited mainly by the
complex astrophysics of galaxy formation. As surveys grow in size and scale,
systematic uncertainties in theoretical modeling can become dominant. Dark
energy studies will challenge the computational cosmology community to
critically assess current techniques, develop new approaches to maximize
accuracy, and establish new tools and practices to efficiently employ globally
networked computing resources.

\\ ( http://arXiv.org/abs/astro-ph/0510194 , 9kb)

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Paper: astro-ph/0510195
Date: Thu, 6 Oct 2005 21:11:52 GMT (7kb)

Title: Constraining Dark Energy with the Dark Energy Survey: Theoretical
Challenges

Authors: James Annis, Sarah Bridle, Francisco J. Castander, August E. Evrard,
Pablo Fosalba, Joshua A. Frieman, Enrique Gaztanaga, Bhuvnesh Jain, Andrey V.
Kravtsov, Ofer Lahav, Huan Lin, Joseph Mohr, Albert Stebbins, Terence P.
Walker, Risa H. Wechsler, David H. Weinberg, Jochen Weller

Comments: 5 pages. White paper submitted to the Dark Energy Task Force
\\
The Dark Energy Survey (DES) will use a new imaging camera on the Blanco 4-m
telescope at CTIO to image 5000 square degrees of sky in the South Galactic Cap
in four optical bands, and to carry out repeat imaging over a smaller area to
identify and measure lightcurves of Type Ia supernovae. The main imaging area
overlaps the planned Sunyaev-Zel'dovich survey of the South Pole Telescope. The
idea behind DES is to use four distinct and largely independent methods to
probe the properties of dark energy: baryon oscillations of the power spectrum,
abundance and spatial distribution of clusters, weak gravitational lensing, and
Type Ia supernovae. This white paper outlines, in broad terms, some of the
theoretical issues associated with the first three of these probes (the issues
for supernovae are mostly different in character), and with the general task of
characterizing dark energy and distinguishing it from alternative explanations
for cosmic acceleration. A companion white paper discusses the kind of
numerical simulations and other theoretical tools that will be needed to
address the these issues and to create mock catalogs that allow end-to-end
tests of analysis procedures. Although we have been thinking about these
problems in the specific context of DES, many of them are also relevant to
other planned dark energy studies.

\\ ( http://arXiv.org/abs/astro-ph/0510195 , 7kb)

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Paper: astro-ph/0510196
Date: Thu, 6 Oct 2005 21:24:37 GMT (35kb)

Title: Dark Energy: The Observational Challenge

Authors: David H. Weinberg

Comments: 13 pages, to appear in proceedings of Wide Field Imaging From Space,
New Astronomy Reviews, eds. T. McKay, A. Fruchter, and E. Linder
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Nearly all proposed tests for the nature of dark energy measure some
combination of four fundamental observables: the Hubble parameter H(z), the
distance-redshift relation d(z), the age-redshift relation t(z), or the linear
growth factor D_1(z). I discuss the sensitivity of these observables to the
value and redshift history of the equation of state parameter w, emphasizing
where these different observables are and are not complementary. Demonstrating
time-variability of w is difficult in most cases because dark energy is
dynamically insignificant at high redshift. Time-variability in which dark
energy tracks the matter density at high redshift and changes to a cosmological
constant at low redshift is {\it relatively} easy to detect. However, even a
sharp transition of this sort at z_c=1 produces only percent-level differences
in d(z) or D_1(z) over the redshift range 0.4 < z < 1.8$, relative to the
closest constant-w model. Estimates of D_1(z) or H(z) at higher redshift,
potentially achievable with the Ly-alpha forest, galaxy redshift surveys, and
the CMB power spectrum, can add substantial leverage on such models, given
precise distance constraints at z < 2. The most promising routes to obtaining
sub-percent precision on dark energy observables are space-based studies of
Type Ia supernovae, which measure d(z) directly, and of weak gravitational
lensing, which is sensitive to d(z), D_1(z), and H(z).

\\ ( http://arXiv.org/abs/astro-ph/0510196 , 35kb)

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Paper: astro-ph/0510197
Date: Thu, 6 Oct 2005 21:39:30 GMT (280kb)

Title: Mapping the Large Scale Structure of the Universe

Authors: David H. Weinberg

Comments: 4 pages, 1 figure. A brief, semi-popular review of large scale
structure studies with the 2dFGRS and the SDSS

Journal-ref: Science, Vol. 309, pp. 564-565, July 22, 2005
\\
In a large scale view of the universe, galaxies are the basic unit of
structure. A typical bright galaxy may contain 100 billion stars and span tens
of thousands of light years, but the empty expanses between the galaxies are
much larger still. Galaxies are not randomly distributed in space, but instead
reside in groups and clusters, which are themselves arranged in an intricate
lattice of filaments and walls, threaded by tunnels and pocked with bubbles.
Two ambitious new surveys, the Two-Degree Field Galaxy Redshift Survey (2dFGRS)
and the Sloan Digital Sky Survey (SDSS), have mapped the three-dimensional
distribution of galaxies over an unprecedented range of scales. Astronomers are
using these maps to learn about conditions in the early universe, the matter
and energy contents of the cosmos, and the physics of galaxy formation.

\\ ( http://arXiv.org/abs/astro-ph/0510197 , 280kb)