From Millimeter-wave Technology to Cosmology-The AMiBA Telescope

Ming-Tang ChenAcademia Sinica, Institute of Astronomy & Astrophysics

P. 0. Box 23-141, Taipei 10671, Taiwan

Abstract- This talk is to briefly illustrate the correlationbetween the advance in millimeter-wave technology and therecent rapid progress in modern cosmology. An on-goinginstrumentation project, the Array for Microwave BackgroundAnisotropy (AMiBA) is used as a working example to address theconnection between the technology and its scientific exploration.

I. INTRODUCTION

As the name explicitly indicates, radio astronomy is ascience inseparable from the engineering technology in radiofrequency. Originated from the serendipitous engineeringwork of Karl Jansky in 1930's, through the rapid developmentof radar in the '40 and '50, the technology in radio frequency isthe backbone of the modern radio astronomy. Interestingly,radio astronomy has since become a niche challenge for thoseRF engineers with scientific interest in mind [1]. Now the termof radio-wave technology in astronomy has spanned from verylow frequency, through microwave and millimeter-wave, to thequasi-optically terahertz regime. Sophisticated instrumentshave been built for ground-based and space-borne projects.For example the Submillimeter Array [2], and the AtacamaLarge Millimeter Array [3], which the later is the currentlylargest ground-base d project in the world.The advance in radio wave, in particular in millimeter-wave

(MMW) technology also transforms another scientific branch,cosmology, from a mostly theoretical modeling into a precisionobservational science. The synergy between cosmology and

Figure 1: AMiBA Telescope on Mauna Loa

MMW technology may not be such elusive once we realizethat the Universe is filled with photons with a blackbodytemperature of 2.7K. The connection is mostly prominent withthe blooming of the cosmology experiments and results in thepast two decades. With the launch of the Cosmic BackgroundExplorer (COBE) [4] in 1989, to the most recent WilkinsonMicrowave Anisotropy Probe (WMAP) data [5], followed bythe to-be-launched Planck telescope [6], the effort is to obtainthe ever-detailed maps of the cosmic microwave background(CMB) in temperature and in polarization. In parallel, there isa crowded race for the ground-based instruments developedand constructed with timely state-of-the-artMMWtechnologies, and meticulous optimized for the same purpose.They are all carefully designed to optimize their capability inobserving the CMB. Together with all these effort, we areobserving an unprecedented advance in our knowledge aboutthe origin of the universe and the content within.

This talk will briefly review the correlation between theMMW technology and the modern cosmology. A furtherdetailed will focus on a project that we have been working on,the Array for Microwave Background Anisotropy (AMiBA)[7][8]. As a dual-channel, 86-102 GHz interferometer array ofup to 19 elements, AMiBA is designed to have full polarizationcapabilities, sampling structures greater than 2 arc minutes insize. The AMiBA targets specifically the distribution of highred-shift clusters of galaxies via the Sunyaev-Zeldovich Effect(SZE), as a means to probe the structure of the universe.AMiBA will also measure the polarization properties of theCosmic Microwave Background (CMB), which is sensitive tothe ionization history of the universe and is a potential probefor gravity waves. AMiBA is sited on Mauna Loa in Hawaii,at an elevation of 3,300m to take advantage of higheratmospheric transparency and minimum radio frequencyinterference. Currently, activities are focused on the operationsof a seven-element AMiBA at the site, while we are pushingtoward an expansion of 13-element array.

REFERENCES

[1] C. H. Townes, "Challenge of Astronomy to Millimeter-WaveTechnology", IEEE Trans. Microwave Theory Tech., vol. 24, no.11, 709-71 1, November 1976.

[2] P. T. P. Ho, J. M. Moran, and K. Y. LO, "The Submillimeter Array,"Astrophysical Journal Lett. vol. 616,pp. L1-L6, Nov. 2004.

978-1-4244-1886-2/08/$25.00 C2008 IEEE. GSMM2008 Proceeding

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Mennella, G. Morgante, M. Sandri, L. Terenzi, L. Valenziano, "ThePlanck Telescope", The AIP Proceedings of the Workshop on"Experimental Cosmology at millimeter wavelengths", Cervinia, Italy, 9-13 July 2001. arXiv:astro-ph/0112173vl. Orhttp://sci.esa.int.

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[8] P. Raffin, P. Koch, Y.-D. Huang, C.-H. Chang, J. Chang, M.-T. Chen, K.Y. Lo, P. T. P. Ho, C.-W. Huang, R. Ibanez, H. Jiang, M. Kesteven, K.-Y.Lin, G.-C. Liu, H. Nishioka, and K. Umetsu, "Progress of the Array forMicrowave Background Anisotropy (AMiBA)", Proc. of SPIE Volume:6273, Optomechanical Technologies for Astronomy, May 2006.