Working from the standard model of the "Big Bang" some 14 billion years ago, we are investigating the early epoch of inflation and the nature and role of dark matter in the evolution of structure in the Universe. We also seek to understand the nature and properties of the "dark energy" that is speeding up the expansion of the Universe.

Seed Magnetic Fields

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Magnetic fields appear to be present in all galaxies and galaxy
clusters, and perhaps even in the smooth low density intergalactic
medium. One explanation for these observations is that a seed magnetic
field was generated by some unknown mechanism early in the life of the
Universe, and was later amplified by various dynamos in nonlinear
objects like galaxies and clusters. We showed that primordial
magnetic fields are expected to be generated in the early Universe on
purely linear scales through vorticity induced by scale-dependent

CMB Polarization

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BICEP 1, BICEP 2, Keck Array, and BICEP 3

Massive Cluster Surveys

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x-ray and optical images

ESA’s Planck Mission has provided a large, statistically representative sample of massive clusters, detected over the full sky (|b| > 15°) through their Sunyaev-Zel'dovich (SZ) effect. The Planck ESZ clusters are sufficiently X-ray bright that for all 165 z < 0.35 clusters, the proposed Chandra observations will collect 10,000 source counts that will be used to characterize each cluster’s dynamical state including merger properties, to measure cluster masses and mass proxies, and to define local cluster mass and temperature functions.

Extragalactic Distance Scale

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thin accretion disk surrounding the supermassive black hole at the center of the galaxy NGC 4258

Supermassive black holes are now thought to lie at the centers of many if not all galaxies. Under the right conditions, X-ray emission from hot gas very close to the black holes can stimulate water molecules further out to emit maser (i.e., microwave laser-like) emission.

Cosmic Microwave Background

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South Pole Telescope

The CfA is collaborating with several other institutions in the construction of a 10 meter diameter millimeter- and submillimeter-wave telescope located at the National Science Foundation Amundsen-Scott South Pole Station. The so-called South Pole Telescope is designed to feed large arrays of detectors and provide a low-background, low-noise environment. The first project, scheduled for 2007 and 2008, is a survey of 4000 square degrees of the southern sky at 2 mm wavelength to an rms noise level of 10 microKelvin (0.8 mJy).

21 cm Cosmology Observations

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simulation by Springel & Hernquist (2003) of the collapse of matter

The birth of the Universe in the Big Bang produced a hot soup of radiation and matter. After some 300,000 years, this soup had cooled sufficiently that free electrons and protons could combine to form neutral hydrogen atoms. Thus began the Cosmological Dark Age, an epoch when there were no stars, no quasars, no luminous sources. Compared to today, the universe was dark and cold.

Reionization & First Stars

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simulation of the reionization process

The reionization epoch marks the period when the first stars formed and produced ultra-violet photons that subsequently ionized most of the Universe's hydrogen. The epoch is arguably the least understood period in the lifetime of the Universe, and it marks the transition from a simple, homogeneous universe to a rich, structure-filled universe.

Galaxy Formation & Evolution

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simulation of high-redshift galaxies mergers

Observations reveal a rich diversity of galaxies around us. However, achieving a theoretical understanding of how such a diverse group of objects is created and evolves has proved to be challenging. TA scientists have been instrumental in understanding the pivotal role radiative feedback from a central super-massive black hole plays in galactic evolution. TA scientists are running numerical simulations to understand the effects mergers have on galactic morphology.

Clusters and Cosmology

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Most of the matter in the Universe is "dark". Although emission directly from this material has not been detected at any wavelength, the presence of this matter is inferred from observations at many wavelengths from the radio, through the optical, to the X-ray. These observations have shown that galaxies are surrounded by dark matter halos and that clusters of galaxies are filled with dark matter.

Intergalactic Medium

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blazar Markarian 421

Not all the original, primordial, gas originally spread almost perfectly uniformly after the Big Bang has yet collapsed to form galaxies. Galaxy formation is still ongoing, and we can watch it happening over cosmic time by looking to high redshifts. The gas not yet condensed into galaxies is called the "Intergalactic Medium".