Near infrared flares of Sagittarius A*: Importance of near infrared polarimetry

TL;DR

This paper presents simulations and observations of near-infrared flares from Sagittarius A*, emphasizing the importance of polarimetry in understanding accretion processes and detecting orbiting matter near the black hole.

Contribution

It introduces a combined approach of simulations and multi-epoch observations to analyze NIR flares and polarization, confirming the hot spot model and detecting signatures of orbiting matter.

Findings

Correlation between flux modulations and polarization changes

Detection of orbiting matter signatures under strong gravity

Confirmation of hot spot model predictions

Abstract

We report on the results of new simulations of near-infrared (NIR) observations of the Sagittarius A* (Sgr A*) counterpart associated with the super-massive black hole at the Galactic Center. The observations have been carried out using the NACO adaptive optics (AO) instrument at the European Southern Observatory's Very Large Telescope and CIAO NIR camera on the Subaru telescope (13 June 2004, 30 July 2005, 1 June 2006, 15 May 2007, 17 May 2007 and 28 May 2008). We used a model of synchrotron emission from relativistic electrons in the inner parts of an accretion disk. The relativistic simulations have been carried out using the Karas-Yaqoob (KY) ray-tracing code. We probe the existence of a correlation between the modulations of the observed flux density light curves and changes in polarimetric data. Furthermore, we confirm that the same correlation is also predicted by the hot spot model. Correlations between intensity and polarimetric parameters of the observed light curves as well as a comparison of predicted and observed light curve features through a pattern recognition algorithm result in the detection of a signature of orbiting matter under the influence of strong gravity. This pattern is detected statistically significant against randomly polarized red noise. Expected results from future observations of VLT interferometry like GRAVITY experiment are also discussed.