NDLI: Interstellar scattering as a cosmological probe

Content Provider	IEEE Xplore Digital Library
Author	Koay, J.Y. Macquart, J. Rickett, B.J. Bignall, H.E. Lovell, J.E.J. Reynolds, C. Jauncey, D. Pursimo, T. Kedziora-Chudczer, L. Ojha, R.
Copyright Year	2011
Description	Author affiliation: Australia Telescope National Facility CSIRO, PO Box 76, Epping, NSW 1710, Australia (Jauncey, D.) \|\| Nordic Optical Telescope, Apartado 474, 38700 Santa Cruz de La Palma, Spain (Pursimo, T.) \|\| International Centre for Radio Astronomy Research, Curtin University, Bentley, WA 6102, Australia (Koay, J.Y.; Macquart, J.; Bignall, H.E.; Reynolds, C.) \|\| Department of Electrical and Computer Engineering, University of California, San Diego, CA 92093, USA (Rickett, B.J.) \|\| NASA, Goddard Space Flight Center, Greenbelt, MD 20771, USA (Ojha, R.) \|\| School of Physics and Astrophysics, University of New South Wales, Sydney, NSW 2052, Australia (Kedziora-Chudczer, L.) \|\| School of Mathematics and Physics, University of Tasmania, TAS 7001, Australia (Lovell, J.E.J.)
Abstract	Since the discovery that the flux densities of very compact astrophysical sources are modulated by scattering in the inhomogeneous, ionized interstellar medium (ISM) of our own Galaxy through a phenomenon known as Interstellar Scintillation (ISS), these scattering effects have been used with great success as a tool to probe the physics of the ISM and the sources themselves. With the recent discovery of a redshift dependence in the ISS of quasars in a 4.9 GHz survey of about 500 sources, large statistical studies of ISS have been imbued with a cosmological significance. Possible causes of this effect include cosmological expansion, scatter broadening by the ionized intergalactic medium and evolution of quasar morphology with redshift. Since each of these hypotheses have different wavelength dependences, we have carried out dual-frequency observations of a subsample of 140 quasars to determine the origin of this redshift dependence of ISS. We are therefore using interstellar scattering, for the first time, as a cosmological probe at micro-arcsecond scales — achieving an angular resolution two orders of magnitude finer than that of Very Long Baseline Interferometry (VLBI). We discover a weaker redshift dependence at 8.4 GHz as compared to 4.9 GHz, indicating a strong wavelength scaling in the effect. We are investigating possible source selection effects and developing the theory to model the observations to enable an accurate interpretation of the data.
Starting Page	1
Ending Page	4
File Size	391182
Page Count	4
File Format	PDF
ISBN	9781424451173
e-ISBN	9781424460519
DOI	10.1109/URSIGASS.2011.6051260
Language	English
Publisher	Institute of Electrical and Electronics Engineers, Inc. (IEEE)
Publisher Date	2011-08-13
Publisher Place	Turkey
Access Restriction	Subscribed
Rights Holder	Institute of Electrical and Electronics Engineers, Inc. (IEEE)
Subject Keyword	Radio astronomy NASA Scattering Educational institutions Australia Probes
Content Type	Text
Resource Type	Article

Sl.	Authority	Responsibilities	Communication Details
1	Ministry of Education (GoI), Department of Higher Education	Sanctioning Authority	https://www.education.gov.in/ict-initiatives
2	Indian Institute of Technology Kharagpur	Host Institute of the Project: The host institute of the project is responsible for providing infrastructure support and hosting the project	https://www.iitkgp.ac.in
3	National Digital Library of India Office, Indian Institute of Technology Kharagpur	The administrative and infrastructural headquarters of the project	Dr. B. Sutradhar bsutra@ndl.gov.in
4	Project PI / Joint PI	Principal Investigator and Joint Principal Investigators of the project	Dr. B. Sutradhar bsutra@ndl.gov.in Prof. Saswat Chakrabarti will be added soon
5	Website/Portal (Helpdesk)	Queries regarding NDLI and its services	support@ndl.gov.in
6	Contents and Copyright Issues	Queries related to content curation and copyright issues	content@ndl.gov.in
7	National Digital Library of India Club (NDLI Club)	Queries related to NDLI Club formation, support, user awareness program, seminar/symposium, collaboration, social media, promotion, and outreach	clubsupport@ndl.gov.in
8	Digital Preservation Centre (DPC)	Assistance with digitizing and archiving copyright-free printed books	dpc@ndl.gov.in
9	IDR Setup or Support	Queries related to establishment and support of Institutional Digital Repository (IDR) and IDR workshops	idr@ndl.gov.in

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