THE EFFECTS of ACCRETION FLOW DYNAMICS on the BLACK HOLE SHADOW of SAGITTARIUS A∗

Hung Yi Pu, Kazunori Akiyama, Keiichi Asada

Research output: Contribution to journalArticlepeer-review

15 Citations (Scopus)

Abstract

A radiatively inefficient accretion flow (RIAF), which is commonly characterized by its sub-Keplerian nature, is a favored accretion model for the supermassive black hole at the Galactic center, Sagittarius A∗. To investigate the observable features of an RIAF, we compare the modeled shadow images, visibilities, and spectra of three flow models with dynamics characterized by (i) a Keplerian shell that is rigidly rotating outside the innermost stable circular orbit (ISCO) and infalling with a constant angular momentum inside ISCO, (ii) a sub-Keplerian motion, and (iii) a free-falling motion with zero angular momentum at infinity. At near-millimeter wavelengths, the emission is dominated by the flow within several Schwarzschild radii. The energy shift due to these flow dynamics becomes important and distinguishable, suggesting that the flow dynamics are an important model parameter for interpreting the millimeter/sub-millimeter very long baseline interferometric observations with the forthcoming, fully assembled Event Horizon Telescope (EHT). As an example, we demonstrate that structural variations of Sagittarius A∗ on event horizon-scales detected in previous EHT observations can be explained by the non-stationary dynamics of an RIAF.

Original languageEnglish
Article number4
JournalAstrophysical Journal
Volume831
Issue number1
DOIs
Publication statusPublished - 2016 Nov 1
Externally publishedYes

Keywords

  • Galaxy: center
  • accretion, accretion disks
  • black hole physics
  • submillimeter: general
  • techniques: interferometric

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

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