ALMA Long Baseline Campaigns: Phase Characteristics of Atmosphere at Long Baselines in the Millimeter and Submillimeter Wavelengths
| Autor: | Richard Hills, Satoki Matsushita, Nicholas D. Whyborn, Luke T. Maud, Catherine Vlahakis, Remo P. J. Tilanus, Ryohei Kawabe, Edward B. Fomalont, Koh-Ichiro Morita, Denis Barkats, Bojan Nikolic, Yoshiharu Asaki |
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| Přispěvatelé: | Nikolic, Bojan [0000-0001-7168-2705], Apollo - University of Cambridge Repository |
| Jazyk: | angličtina |
| Rok vydání: | 2017 |
| Předmět: |
Physics
Phase (waves) FOS: Physical sciences techniques: high angular resolution Astronomy and Astrophysics Scale height Geodesy 01 natural sciences 010309 optics Atmosphere site testing Wavelength Path length Space and Planetary Science techniques: interferometric 0103 physical sciences Millimeter Astrophysics - Instrumentation and Methods for Astrophysics 010303 astronomy & astrophysics Instrumentation and Methods for Astrophysics (astro-ph.IM) Water vapor Coherence (physics) atmospheric effects |
| Zdroj: | PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF THE PACIFIC, 129(3), 035004 PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF THE PACIFIC |
| DOI: | 10.17863/cam.8498 |
| Popis: | This paper presents the first detailed investigation of the characteristics of mm/submm phase fluctuation and phase correction methods obtained using ALMA with baseline lengths up to ~15 km. Most of the spatial structure functions (SSFs) show that the phase fluctuation increases as a function of baseline length, with a power-law slope of ~0.6. In many cases, we find that the slope becomes shallower (average of ~0.2-0.3) at baseline lengths longer than ~1 km, namely showing a turn-over in SSF. The phase correction method using water vapor radiometers (WVRs) works well, especially for the cases where PWV >1 mm, which reduces the degree of phase fluctuations by a factor of two in many cases. However, phase fluctuations still remain after the WVR phase correction, suggesting the existence of other turbulent constituent that cause the phase fluctuation. This is supported by occasional SSFs that do not exhibit any turn-over; these are only seen when the PWV is low or after WVR phase correction. This means that the phase fluctuation caused by this turbulent constituent is inherently smaller than that caused by water vapor. Since there is no turn-over in the SSF up to the maximum baseline length of ~15 km, this turbulent constituent must have scale height of 10 km or more, and thus cannot be water vapor, whose scale height is around 1 km. This large scale height turbulent constituent is likely to be water ice or a dry component. Excess path length fluctuation after the WVR phase correction at a baseline length of 10 km is large (>200 micron), which is significant for high frequency (>450 GHz or 12 pages, 7 figures. PASP, in press |
| Databáze: | OpenAIRE |
| Externí odkaz: |
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