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DETECTING CHANGING POLARIZATION STRUCTURES IN SAGITTARIUS A* WITH HIGH FREQUENCY VLBI

Abstract

Sagittarius A* is the source of near infrared, X-ray, radio, and (sub)millimeter emission associated with the supermassive black hole at the Galactic Center. In the submillimeter regime, Sgr A* exhibits time-variable linear polarization on timescales corresponding to <10 Schwarzschild radii of the presumed 4 x 10{sup 6} M {sub sun} black hole. In previous work, we demonstrated the potential for total-intensity (sub)millimeter-wavelength very long baseline interferometry (VLBI) to detect time-variable-and periodic-source structure changes in the Sgr A* black hole system using nonimaging analyses. Here, we extend this work to include full polarimetric VLBI observations. We simulate full-polarization (sub)millimeter VLBI data of Sgr A* using a hot spot model that is embedded within an accretion disk, with emphasis on nonimaging polarimetric data products that are robust against calibration errors. Although the source-integrated linear polarization fraction in the models is typically only a few percent, the linear polarization fraction on small angular scales can be much higher, enabling the detection of changes in the polarimetric structure of Sgr A* on a wide variety of baselines. The shortest baselines track the source-integrated linear polarization fraction, while longer baselines are sensitive to polarization substructures that are beam-diluted by connected-element interferometry. The detection of periodic  More>>
Authors:
Fish, Vincent L; Doeleman, Sheperd S; Rogers, Alan E. E.; [1]  Broderick, Avery E; [2]  Loeb, Abraham [3] 
  1. Massachusetts Institute of Technology, Haystack Observatory, Route 40, Westford, MA 01886 (United States)
  2. Canadian Institute for Theoretical Astrophysics, University of Toronto, 60 St. George Street, Toronto, ON M5S 3H8 (Canada)
  3. Institute for Theory and Computation, Harvard University, Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States)
Publication Date:
Dec 01, 2009
Product Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 706; Journal Issue: 2; Other Information: DOI: 10.1088/0004-637X/706/2/1353
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ACCRETION DISKS; ANTENNAS; BLACK HOLES; CALIBRATION; FARADAY EFFECT; GALAXIES; HOT SPOTS; INTERFEROMETRY; PERIODICITY; POLARIZATION; SCHWARZSCHILD RADIUS; ELECTRICAL EQUIPMENT; EQUIPMENT; VARIATIONS
OSTI ID:
21378104
Country of Origin:
United States
Language:
English
Other Identifying Numbers:
Journal ID: ISSN 0004-637X; ASJOAB; TRN: US10O8679108558
Availability:
Available from http://dx.doi.org/10.1088/0004-637X/706/2/1353
Submitting Site:
INIS
Size:
page(s) 1353-1363
Announcement Date:
Dec 22, 2010

Citation Formats

Fish, Vincent L, Doeleman, Sheperd S, Rogers, Alan E. E., Broderick, Avery E, and Loeb, Abraham. DETECTING CHANGING POLARIZATION STRUCTURES IN SAGITTARIUS A* WITH HIGH FREQUENCY VLBI. United States: N. p., 2009. Web. doi:10.1088/0004-637X/706/2/1353.
Fish, Vincent L, Doeleman, Sheperd S, Rogers, Alan E. E., Broderick, Avery E, & Loeb, Abraham. DETECTING CHANGING POLARIZATION STRUCTURES IN SAGITTARIUS A* WITH HIGH FREQUENCY VLBI. United States. doi:10.1088/0004-637X/706/2/1353.
Fish, Vincent L, Doeleman, Sheperd S, Rogers, Alan E. E., Broderick, Avery E, and Loeb, Abraham. 2009. "DETECTING CHANGING POLARIZATION STRUCTURES IN SAGITTARIUS A* WITH HIGH FREQUENCY VLBI." United States. doi:10.1088/0004-637X/706/2/1353. https://www.osti.gov/servlets/purl/10.1088/0004-637X/706/2/1353.
@misc{etde_21378104,
title = {DETECTING CHANGING POLARIZATION STRUCTURES IN SAGITTARIUS A* WITH HIGH FREQUENCY VLBI}
author = {Fish, Vincent L, Doeleman, Sheperd S, Rogers, Alan E. E., Broderick, Avery E, and Loeb, Abraham}
abstractNote = {Sagittarius A* is the source of near infrared, X-ray, radio, and (sub)millimeter emission associated with the supermassive black hole at the Galactic Center. In the submillimeter regime, Sgr A* exhibits time-variable linear polarization on timescales corresponding to <10 Schwarzschild radii of the presumed 4 x 10{sup 6} M {sub sun} black hole. In previous work, we demonstrated the potential for total-intensity (sub)millimeter-wavelength very long baseline interferometry (VLBI) to detect time-variable-and periodic-source structure changes in the Sgr A* black hole system using nonimaging analyses. Here, we extend this work to include full polarimetric VLBI observations. We simulate full-polarization (sub)millimeter VLBI data of Sgr A* using a hot spot model that is embedded within an accretion disk, with emphasis on nonimaging polarimetric data products that are robust against calibration errors. Although the source-integrated linear polarization fraction in the models is typically only a few percent, the linear polarization fraction on small angular scales can be much higher, enabling the detection of changes in the polarimetric structure of Sgr A* on a wide variety of baselines. The shortest baselines track the source-integrated linear polarization fraction, while longer baselines are sensitive to polarization substructures that are beam-diluted by connected-element interferometry. The detection of periodic variability in source polarization should not be significantly affected even if instrumental polarization terms cannot be calibrated out. As more antennas are included in the (sub)millimeter-VLBI array, observations with full polarization will provide important new diagnostics to help disentangle intrinsic source polarization from Faraday rotation effects in the accretion and outflow region close to the black hole event horizon.}
doi = {10.1088/0004-637X/706/2/1353}
journal = {Astrophysical Journal}
issue = {2}
volume = {706}
place = {United States}
year = {2009}
month = {Dec}
}