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Dicke's Superradiance in Astrophysics. I. The 21 cm Line

Rajabi, Fereshteh and Houde, Martin (2016) Dicke's Superradiance in Astrophysics. I. The 21 cm Line. Astrophysical Journal, 826 (2). Art. No. 216. ISSN 0004-637X. doi:10.3847/0004-637X/826/2/216.

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We have applied the concept of superradiance introduced by Dicke in 1954 to astrophysics by extending the corresponding analysis to the magnetic dipole interaction characterizing the atomic hydrogen 21 cm line. Although it is unlikely that superradiance could take place in thermally relaxed regions and that the lack of observational evidence of masers for this transition reduces the probability of detecting superradiance, in situations where the conditions necessary for superradiance are met (close atomic spacing, high velocity coherence, population inversion, and long dephasing timescales compared to those related to coherent behavior), our results suggest that relatively low levels of population inversion over short astronomical length-scales (e.g., as compared to those required for maser amplification) can lead to the cooperative behavior required for superradiance in the interstellar medium. Given the results of our analysis, we expect the observational properties of 21 cm superradiance to be characterized by the emission of high-intensity, spatially compact, burst-like features potentially taking place over short periods ranging from minutes to days.

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Additional Information:© 2016 American Astronomical Society. Received 2015 April 21; revised 2016 May 29; accepted 2016 June 1; published 2016 August 1. We thank M. Harwit for bringing this research topic to our attention and J. Zmuidzinas for helpful discussions. We are also grateful to T. Troland for alerting us to the evidence for a 21 cm population inversion in the Orion Veil. MH's research is funded through the NSERC Discovery Grant and the Western Strategic Support.
Funding AgencyGrant Number
Natural Sciences and Engineering Research Council of Canada (NSERC)UNSPECIFIED
Western Strategic SupportUNSPECIFIED
Subject Keywords:atomic processes; ISM: atoms; radiation mechanisms: general
Issue or Number:2
Record Number:CaltechAUTHORS:20161003-082759676
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Official Citation:Fereshteh Rajabi and Martin Houde 2016 ApJ 826 216
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:70741
Deposited By: Ruth Sustaita
Deposited On:03 Oct 2016 16:50
Last Modified:11 Nov 2021 04:34

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