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Title: Two-body relaxation driven evolution of the young stellar disk in the galactic center

Abstract

The center of our Galaxy hosts almost two hundred very young stars, a subset of which is orbiting the central supermassive black hole (SMBH) in a relatively thin disk-like structure. First analyses indicated a power-law surface density profile of the disk, Σ∝R {sup β} with β = –2. Recently, however, doubts about this profile arose. In particular, it now seems to be better described by a sort of broken power law. By means of both analytical arguments and numerical N-body modeling, we show that such a broken power-law profile is a natural consequence of the two-body relaxation of the disk. Due to the small relative velocities of the nearby stars in co-planar Keplerian orbits around the SMBH, two-body relaxation is effective enough to affect the evolution of the disk on timescales comparable to its estimated age. In the inner, densest part of the disk, the profile becomes rather flat (β ≈ –1) while the outer parts keep imprints of the initial state. Our numerical models show that the observed projected surface density profile of the young stellar disk can result from two-body relaxation driven evolution of a disk with initial single power-law profile with –2 ≲ β ≲ –1.5. Inmore » addition, we suggest that two-body relaxation may have caused a significant radial migration of the S-stars toward the central SMBH, thus playing an important role in their formation scenario.« less

Authors:
;  [1]
  1. Charles University in Prague, Faculty of Mathematics and Physics, Astronomical Institute, V Holešovičkách 2, Praha CZ-18000 (Czech Republic)
Publication Date:
OSTI Identifier:
22356931
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 786; Journal Issue: 2; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; BLACK HOLES; COMPARATIVE EVALUATIONS; DENSITY; EVOLUTION; GALAXIES; GALAXY NUCLEI; MIGRATION; ORBITS; RELAXATION; SIMULATION; STARS; SURFACES; TWO-BODY PROBLEM; VELOCITY

Citation Formats

Šubr, Ladislav, and Haas, Jaroslav. Two-body relaxation driven evolution of the young stellar disk in the galactic center. United States: N. p., 2014. Web. doi:10.1088/0004-637X/786/2/121.
Šubr, Ladislav, & Haas, Jaroslav. Two-body relaxation driven evolution of the young stellar disk in the galactic center. United States. doi:10.1088/0004-637X/786/2/121.
Šubr, Ladislav, and Haas, Jaroslav. 2014. "Two-body relaxation driven evolution of the young stellar disk in the galactic center". United States. doi:10.1088/0004-637X/786/2/121.
@article{osti_22356931,
title = {Two-body relaxation driven evolution of the young stellar disk in the galactic center},
author = {Šubr, Ladislav and Haas, Jaroslav},
abstractNote = {The center of our Galaxy hosts almost two hundred very young stars, a subset of which is orbiting the central supermassive black hole (SMBH) in a relatively thin disk-like structure. First analyses indicated a power-law surface density profile of the disk, Σ∝R {sup β} with β = –2. Recently, however, doubts about this profile arose. In particular, it now seems to be better described by a sort of broken power law. By means of both analytical arguments and numerical N-body modeling, we show that such a broken power-law profile is a natural consequence of the two-body relaxation of the disk. Due to the small relative velocities of the nearby stars in co-planar Keplerian orbits around the SMBH, two-body relaxation is effective enough to affect the evolution of the disk on timescales comparable to its estimated age. In the inner, densest part of the disk, the profile becomes rather flat (β ≈ –1) while the outer parts keep imprints of the initial state. Our numerical models show that the observed projected surface density profile of the young stellar disk can result from two-body relaxation driven evolution of a disk with initial single power-law profile with –2 ≲ β ≲ –1.5. In addition, we suggest that two-body relaxation may have caused a significant radial migration of the S-stars toward the central SMBH, thus playing an important role in their formation scenario.},
doi = {10.1088/0004-637X/786/2/121},
journal = {Astrophysical Journal},
number = 2,
volume = 786,
place = {United States},
year = 2014,
month = 5
}
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