PARTICLE ASTROPHYSICS & COSMOLOGY
PRINCIPAL INVESTIGATOR: GEORGE F. SMOOT
Other Group Members:

* Julian Borrill, Post Doctoral Fellow Physics
* John Jacobsen, Post Doctoral Fellow Physics
* Andrew Jaffe, Post Doctoral Fellow Physics
* Jodi Lamoureux Post-Doctoral Fellow Physicist
* Bruce Grossan, Assistant Research Physicist
* Eric Gawiser, Graduate Student, UCB Physics Department (shared with Joe Silk)
* Amedeo Balbi, Graduate Student, Physics Department, University of Roma
* Henrik Nordberg, Graduate Student, Physics Department, Lund University
* Bahman Rabii, Graduate Student, UCB Physics Department
* Mike Leung, undergraduate, Physics Department
* Asad Aboobaker, undergraduate, Physics Department
* KiWon Yoon, undergraduate, Physics Department
* Peter Curran, undergraduate, University College Cork
* Ian Ellwood, undergraduate
* Abraham Harte, undergraduate, College of Marin
* Jon Aymon, software/data analyst
* John Gibson, electronic engineer
* Vanessa Arce, Administrative Assistant
* Willi Chinowsky, Research Physicist

1. COSMOLOGY with the Cosmic Background Radiation
Measurements of The Cosmic Background Radiation (CMB) provide important information about physical processes in the Universe from soon after the Big Bang until the present. In the Big Bang model, which has now become the standard model of cosmology, the CMB last interacted significantly with matter at a time roughly one third of million years after the start of the universal expansion and about 10-15 billion years before the present epoch. The CMB carries with it the information about that interaction and to a lesser degree the effects occurring during its journey to us. Its angular distribution is related to the distribution of matter and energy in the early Universe; its spectrum provides information about processes involving the release of energy.

During the past year we have continued our investigations using the cosmic microwave background (CMB) radiation as a probe of cosmology.
COBE
Analysis of the COBE satellite data sets continues to provide additional new results and acts as a test bed for new techniques and algorithms in the 8th year past its launch and 5 years since its discovery of CMB anisotropies. Its data remain in many ways the best CMB anisotropy data. During 1998 the primary new results were presented in papers about the discovery of the cosmic infrared background radiation.

With COBE we have made major advances in measuring the large angular scale distribution of the CMB. The major products from COBE include a series of maps of the full sky in the 1 micrometer to 1 centimeter wavelength range. COBE was operated for four years, providing high quality data from about half its sensors. The other half of the sensors were turned off when the liquid helium coolant was exhausted near the end of the first year.

The processing and analysis of the data from COBE has provided high quality maps of the microwave and infrared sky, and their subsequent analysis has yielded significant new cosmological and astrophysical information. Of the three instruments aboard COBE, Dr. Smoot is principal investigator of the Differential Microwave Radiometer (DMR) experiment. The announcement of the detection of anisotropies by Dr. Smoot has been followed by numerous interpretive papers by members of the COBE/DMR collaboration and by outside researchers.

The observed anisotropies have been a powerful cosmological tool providing information on the initial conditions leading to the formation of large scale structure such as galaxies and clusters of galaxies. It has also let us determine important cosmological parameters such as the dynamics, geometry and topology of the Universe.

Our group has continued the analysis of the old and new data. Public release of the resulting skymaps occurred for the first year's observations in June 1993. The first two years worth of data were released in June, 1994. The full four-year data and first results were made public in January 1996. The COBE project came to its official termination at the end of 1997; however, we can anticipate that its data and experience will continue to play an important role in cosmology for a few more years.

Figure 1. Full sky map of the CMB anisotropies from the COBE DMR.
Max Planck Surveyor
We, as part of a larger collaboration, have completed the Phase A study of the third generation CMB anisotropy mission, the European Space Agency (ESA) M3 mission: Max Planck Surveyor satellite. Launch is anticipated circa 2007.
MAXIMA/BOOMERANG Balloon-borne Instruments
We - a collaboration with Professors Paul Richards at SSL, Andrew Lange (CalTech), and Paola deBernardis (Rome) - have built and tested a pair of new generation balloon-borne gondolas and instruments MAXIMA & BOOMERANG . BOOMERANG had its first and successful flight in early September 1997. MAXIMA had its first scientific utilizing an array receiver in August 1998. A long-duration flight of BOOMERANG from Antarctica is planned for in the coming season (mid-December to mid-January). We anticipate flying MAXIMA again in the summer of 1999 and preparations are underway.

Data processing and analysis of these data is underway and we anticipate first results being made public in early 1999 and much more later.
Foreground Emissions
We have reached the point where the emission from the galaxy is beginning to limit the interpretation of the data. Thus we have embarked on a program to improve our understanding and modeling of this emission for both the cosmological interpretations and the study of our galaxy. This involves both a project to make low frequency radio maps of the sky dubbed the Galactic Emission Mapping (GEM) project and an effort to model and find means to remove Galactic and extragalactic foregrounds from the data. The GEM instrument was shipped to Brazil from Tenerife. It has been refurbished and is now operating and taking data.
2. Ultra-High Energy Neutrino Astronomy
In collaboration with Hank Crawford (SSL), Willi Chinowsky, Dave Nygren, and Bob Stokstad we have been working on the development of a km-scale ultra-high energy neutrino detector. This work has led us to a collaboration with the AMANDA project. At this time we are deeply involved in the analysis of the 1997 AMANDA data in which a number of very high energy neutrino-induced muons have been detected. We are also busy preparing for the arrival of the 1998 AMANDA data. Work is underway on the development of a digital optical module technology and its deployment in the Antarctic ice an the 1999-2000 season.

6. Milestones

* Completion of the Instrument Proposals and their Selection for Planck Surveyor
* Award of NERSC supercomputer time and resources
* Award of NSF KDI grant to develop advanced data processing and analysis techniques

7. Graduate Students Supported

* Bahman Rabii, Physics Department
* Henrik Nordberg, Physics Department, Lund University
* Amedeo Balbi, Physics Department, University of Roma

8. Publications

* "The CMB Anisotropy Experiments: Cosmic Microwave Background," G.F. Smoot. The Cosmic Microwave Background, edited by C.H. Lineweaver, J.G. Bartlett, A. Blanchard, M. Signore, and J. Silk, 185-240, Kluwer Academic Publishers (1997).
* "The CMB Spectrum," G.F. Smoot. The Cosmic Microwave Background, edited by C.H. Lineweaver, J.G. Bartlett, A. Blanchard, M. Signore, and J. Silk, 271-308, Kluwer Academic Publishers (1997).
* "Cosmology with the CMB," G.F. Smoot. International Journal of Modern Physics D, 6, 4, 377-391, World Scientific Publishing Company (1997).
* "Diffraction Analysis of a Double-Shielded Antenna in the Fraunhofer and Fresnel Regimes," C. Tello, T. Villela, C. A. Wuensche, N. Figueiredo, S. Torres, M. Bersanelli, M. Bensadoun, G. DeAmici, and G.F. Smoot. Radio Science (1997).
* "The COBRAS/SAMBA Space Mission," N. Mandolesi, M. Bersanelli, C. Cesarsky, L. Danese, G. Efstathiou, M. Griffin, J.M. Lamarre, H.U. Norgaard-Nielsen, O. Pace, J.L. Puget, A. Raisanen, G.F. Smoot, and J. Tauber. Il Nuovo Cimento 20, 5 Sept.-Oct. (1997).
* "The COBE Diffuse Infrared Background Experiment Search for the Cosmic Infrared Background: Limits and Detections," M.G. Hauser, R.G. Arendt, T. Kelsall, E. Dwek, N. Odegard, J.L. Weiland, H.T. Freudenreich, W.T. Reach, R.F. Silverberg, S.H. Moseley, Y.C. Pei, P. Lubin, J.C. Mather, R.A. Shafer, G.F. Smoot, R. Weiss, D.T. Wilkinson, and E.L. Wright. December The Astrophysical Journal (1997).
* "Observing the Early Universe," G.F. Smoot. Proceedings from presentation at Ninth Partners in Science Conference. Posted on website. (1997).
* "Cosmic Background Radiation," G.F. Smoot and D. Scott. astro-ph/9711069. Revision of original, Oct. (1997).
* "CMB Experiment Baseline Determination by Minimizing Pixel Observations Dispersion," G.F. Smoot. astro-ph/9704193, COBE-5047-REV, The Astrophysical Journal (1997) Submitted
* "A Determination of the Spectral Index of Galactic Synchrotron Emission in the 1-10 GHz Range," P. Platania, M. Bensadoun, M. Bersanelli, G. De Amici, A. Kogut, S. Levin, D. Maino, and G.F. Smoot . astro-ph/9707252, The Astrophysical Journal (1997)
* "The Cosmic Microwave Background Spectrum: An Analysis of Observations," H.P. Nordberg, G.F. Smoot. astro-ph/9805123, The Astrophysical Journal (1998) Submitted
* "Galactic Free-Free and Ha Emission," G.F. Smoot. astro-ph/9801121 v.2 Jan. 14 The Astrophysical Journal (1998).
* "Cosmic Microwave Background Anisotropy Science," G.F. Smoot, Current Topics in Astrofundamental Physics: Primordial Cosmology, edited by N. Sanchez and A. Zichichi, Kluwer Academic Publishers (1998).
* `Matching Numerical Simulations To Continuum Field Theories: A Lattice Renormalization Study', Julian Borrill and Marcelo Gleiser, Nuc Phys B483 416 (1997). hep-lat/9607026
* "Semilocal String Formation in Two Dimensions', Ana Achucarro, Julian Borrill and Andrew R. Liddle, Phys Rev D57 3742 (1998). hep-ph/9702368
* `Power Spectrum Estimators For Large CMB Datasets', Julian Borrill (Submitted to Phys Rev D) (1997). astro-ph/9712121
* `The Formation Rate Of Semilocal Strings', Ana Achucarro, Julian Borrill and Andrew R. Liddle (Submitted to Phys Rev Lett) (1998). hep-ph/9802306
* `A Fast Method For Bounding The CMB Power Spectrum Likelihood Function', Julian Borrill and Philip J. Stark, (Submitted to Phys Rev D) (1998).astro-ph/9803114
* `The Formation Of Non-Topological String Networks', Ana Achucarro, Julian Borrill and Andrew R. Liddle (Physica B, in press) (1998). hep-ph/9810459
* `The Rate Of Formation Of Semilocal Strings', Julian Borrill, Ana Achucarro, and Andrew R. Liddle in "Proceedings of PASCOS-98". (1998)
* "Limits to Radiative Neutrino Decay from SN1987a", A. Jaffe & M.S. Turner, Phys. Rev. D55, 7951 (1997).
* "H0 and Odds on Cosmology", A. Jaffe, Ap. J., 471, 24, 1996.
* "Bending of Light by Gravity Waves", N. Kaiser & A. Jaffe, Ap. J., 484, 545, 1997.
* "Cosmic Parameter Estimation Combining Sub-Degree CMB Experiments With COBE", J.R. Bond & A. Jaffe, Proc. Moriond XVI, "Microwave Background Anisotropies," 1997.
* "Estimating the Power Spectrum of the Cosmic Microwave Background", J.R. Bond, A.H. Jaffe & L. Knox Phys. Rev. D, Submitted, 1997, CfPA/97-th-11