This Hubble Space Telescope image shows the odd-shaped debris that likely came from a collision between two asteroids.

Click here to view the January 2006 AAS poster "LSST Supernova Cosmology". [PDF]

Because of its rapid cadence, large aperture, and flexible scheduling, LSST will be an excellent tool for studying supernovae and using them as cosmological probes. It will enable myriad new SN-based cosmological experiments that are impossible to perform with existing systems.

Shear Tomography

A glimpse of a universe of mass. Shown here is a map of mass obtained by gravitational lens mass tomography. This 2x2 degree field of mass, obtained in 15 hours of 4-meter telescope exposures in the Deep Lens Survey, would fit easily inside LSST's single snapshot field of view.

Features in the matter power spectrum, such as baryon acoustic oscillations (Peebles & Yu 1970; bond & Efstathiou 1984; Holtzman 1989; Hu & Sugiyama 1996; see Figure 1), can be used as CMB-calibrated standard rulers for determining the angular-diameter distance r(z) and constraining dark energy (Eisenstein, Hu, & Tegmark 1998; Linder 2003; Seo & Eisenstein 2003, hereafter SE03; Angulo et al. 2005).

Comparison Between the CMB and Cosmic Shear as Diagnostics of Cosmology

As predicted, observations of CMB anisotropies have provided tight constraints on cosmological parameters as well as definitive discrimination against competing models of cosmological structure formation. The CMB has been a phenomenal success as a cosmological probe. In this section we elucidate the foundations of this success and argue that the same foundations are in place for cosmic shear.

Weak Lensing and Dark Energy

Weak lensing is a powerful probe of cosmological models, beautifully complementary to those that have given rise to the current standard model of cosmology. The statistics of shear and mass maps on large scales over a wide range in redshift holds much promise for fundamental cosmology. The underlying physics is extremely simple General Relativity: FRW Universe plus the GR deflection formula. One measures angles, dimensionless ellipticities, and redshifts.

Supernovae are stellar explosions so energetic they can briefly outshine an entire galaxy, radiating as much energy in a short amount of time as an ordinary star like the Sun is expected to emit over its 10 billion-year life span. 

The LSST total effective system throughput, AΩ = 318 m² deg²,is nearly two orders of magnitude larger than that of any existing facility. LSST will enable a wide variety of complementary scientific investigations, all utilizing a common database. Of particular interest to particle physics, LSST will probe the physics of dark energy in multiple ways, as well as a measurement of the neutrino mass down to the 10 milli eV level. This will be done via data on the shapes, positions, and distances of billions of galaxies, plus a million supernovae.

LSST will provide multiple probes of dark energy, all using the same survey data. The two most powerful of these is weak gravitational lens tomography and baryon acoustic oscillations. But there are several other probes LSST can undertake as well.

Dark matter continues to stubbornly resist efforts to pin down its nature. Currently we have no means of capturing or making a dark matter particle, although efforts to do just that are underway at laboratories around the world.