Cosmological Smoothed Particle Hydrodynamic Simulations with Four Million Particles: Statistical Properties of X‐Ray Clusters in a Low‐Density Universe

2000 ◽  
Vol 535 (2) ◽  
pp. 593-601 ◽  
Author(s):  
Kohji Yoshikawa ◽  
Y. P. Jing ◽  
Yasushi Suto
Keyword(s):  
Statistical Properties ◽  
Low Density ◽  
Hydrodynamic Simulations ◽  
X Ray ◽  
Smoothed Particle ◽  
Smoothed Particle Hydrodynamic

scholarly journals The impact of episodic outflow feedback on stellar multiplicity and the star formation efficiency

2020 ◽  
Vol 500 (3) ◽  
pp. 3594-3612
Author(s):  
P F Rohde ◽  
S Walch ◽  
S D Clarke ◽  
D Seifried ◽  
A P Whitworth ◽  
...  
Keyword(s):  
Star Formation ◽  
Hydrodynamic Simulations ◽  
The Core ◽  
Subgrid Model ◽  
High Incidence ◽  
Smoothed Particle ◽  
The Mean ◽  
Smoothed Particle Hydrodynamic ◽  
Formation Efficiency ◽  
The Impact

ABSTRACT The accretion of material on to young protostars is accompanied by the launching of outflows. Observations show that accretion, and therefore also outflows, are episodic. However, the effects of episodic outflow feedback on the core scale are not well understood. We have performed 88 smoothed particle hydrodynamic simulations of turbulent dense $1 \, {{\mathrm{M}}}_{\odot }$ cores to study the influence of episodic outflow feedback on the stellar multiplicity and the star formation efficiency (SFE). Protostars are represented by sink particles, which use a subgrid model to capture stellar evolution, inner-disc evolution, episodic accretion, and the launching of outflows. By comparing simulations with and without episodic outflow feedback, we show that simulations with outflow feedback reproduce the binary statistics of young stellar populations, including the relative proportions of singles, binaries, triples, etc. and the high incidence of twin binaries with q ≥ 0.95; simulations without outflow feedback do not. Entrainment factors (the ratio between total outflowing mass and initially ejected mass) are typically ∼7 ± 2, but can be much higher if the total mass of stars formed in a core is low and/or outflow episodes are infrequent. By decreasing both the mean mass of the stars formed and the number of stars formed, outflow feedback reduces the SFE by about a factor of 2 (as compared with simulations that do not include outflow feedback).

scholarly journals Ultra-deep tidal disruption events: prompt self-intersections and observables

2019 ◽  
Vol 488 (4) ◽  
pp. 5267-5278 ◽  
Author(s):  
Siva Darbha ◽  
Eric R Coughlin ◽  
Daniel Kasen ◽  
Chris Nixon
Keyword(s):  
Close Agreement ◽  
Tidal Disruption ◽  
X Ray ◽  
Analytic Estimate ◽  
Smoothed Particle ◽  
Solar Type ◽  
General Relativistic ◽  
Low Mass ◽  
Smoothed Particle Hydrodynamic ◽  
Schwarzschild Radius

ABSTRACT A star approaching a supermassive black hole (SMBH) can be torn apart in a tidal disruption event (TDE). We examine ultra-deep TDEs, a new regime in which the disrupted debris approaches close to the black hole’s Schwarzschild radius, and the leading part intersects the trailing part at the first pericentre passage. We calculate the range of penetration factors β versus SMBH masses M that produce these prompt self-intersections using a Newtonian analytic estimate and a general relativistic (GR) geodesic model. We find that significant self-intersection of Solar-type stars requires β ∼ 50–127 for M/M⊙ = 104, down to β ∼ 5.6–5.9 forM/M⊙ = 106. We run smoothed particle hydrodynamic (SPH) simulations to corroborate our calculations and find close agreement, with a slightly shallower dependence on M. We predict that the shock from the collision emits an X-ray flare lasting t ∼ 2 s with L ∼ 1047 erg s−1 at E ∼ 2 keV, and the debris has a prompt accretion episode lasting t ∼ several minutes. The events are rare and occur with a rate $\dot{N} \lesssim 10^{-7}$ Mpc−3 yr−1. Ultra-deep TDEs can probe the strong gravity and demographics of low-mass SMBHs.

Analysis of Contact Mechanics and Smoothed Particle Hydrodynamic Simulations of Viscoelastic Polymer Sine Waves

2015 ◽  
Author(s):  
Nick Cramer ◽  
Janet Chao ◽  
Travis Tollefson ◽  
M. Teodorescu
Keyword(s):  
United States ◽  
Head And Neck ◽  
Contact Mechanics ◽  
The United States ◽  
Head And Neck Cancers ◽  
Malignant Neoplasms ◽  
Invasive Procedures ◽  
Hydrodynamic Simulations ◽  
Smoothed Particle ◽  
Smoothed Particle Hydrodynamic

According the American Cancer Society’s data, in 2013, an estimated 53,640 people developed head and neck cancers [1], which accounts for about 3% to 5% of all cancers in the United States. Removing head and neck malignant neoplasms is one of the first stages towards patient recovery. However, these types of invasive procedures often lead to disfiguring scars and resections with functional and aesthetical drawbacks (see Figure 1).

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