arXiv subjects

Yohai Meiron

Publications and source records attributed to Yohai Meiron.

23 records · Page 2Linked to original sources

arXiv2012

The limited role of mergers in the black hole to bulge mass relation

We examine the intrinsic scatter in the correlation between black hole masses and their host bulge masses, and find that it cannot be accounted for by mergers alone. A simple merger scenario of small galaxies leads to a proportionality relation between the late-time black hole and bulge masses, with intrinsic scatter (in linear scale) increasing along the ridge line of the relation as the square root of the mass. By examining a sample of 86 galaxies with well measured black hole masses, we find that the intrinsic scatter increases with mass more rapidly than expected from the merger-only scenario. We discuss the possibility that the feedback mechanism that operated during galaxy formation involved the presence of a cooling flow.

astro-ph.CO↗

arXiv2012

A conservation-based method for simulating the inspiral of binary black holes

We present a new approach to studying the evolution of massive black hole binaries in a stellar environment. By imposing conservation of total energy and angular momentum in scattering experiments, we find the dissipation forces that are exerted on the black holes by the stars, and thus obtain the decaying path of the binary from the classical dynamical friction regime down to subparsec scales. Our scheme lies between scattering experiments and N-body simulations. While still resolving collisions between stars and black holes, it is fast enough and allows to use a large enough number of particles to reach a smooth and convergent result. We studied both an equal mass and a 10:1 mass ratio binaries under various initial conditions. We show that while an equal mass binary stalls at a nearly circular orbit, a runaway growth of eccentricity occurs in the unequal mass case. This effect reduces the timescale for black hole coalescence through gravitational radiation to well below the Hubble time, even in spherical and gasless systems formed by dry mergers.

astro-ph.CO↗

arXiv2010

Correlation of Black Hole and Bulge Masses: Driven by Energy but Correlated with Momentum

We use a recent sample of 49 galaxies to show that there is a proportionality relation between the black hole mass M_BH and the quantity μ=M_G*σ/c, where M_G is mass of the spheroidal stellar component and σis the stellar velocity dispersion. μis called the momentum parameter and the ratio is M_BH/μ~3.3. This result is applied to the penetrating-jet feedback model which argues that the correlation that holds is with a momentum-like parameter, although this feedback mechanism is based on energy balance.

astro-ph.CO↗

arXiv2010

The Stellar Kinematic Signature of Massive Black Hole Binaries

The stalling radius of a merging massive binary black hole (BBH) is expected to be below 0".1 even in nearby galaxies (Yu 2002), and thus BBHs are not expected to be spatially resolved in the near future. However, as we show below, a BBH may be detectable through the significantly anisotropic stellar velocity distribution it produces on scales 5-10 times larger than the binary separation. We calculate the velocity distribution of stable orbits near a BBH by solving the restricted three body problem for a BBH embedded in a bulge potential. We present high resolution maps of the projected velocity distribution moments, based on snapshots of ~ 10^8 stable orbits. The kinematic signature of a BBH in the average velocity maps is a counter rotating torus of stars outside the BBH Hill spheres. The velocity dispersion maps reveal a dip in the inner region, and an excess of 20-40% further out, compared to a single BH of the same total mass. More pronounced signatures are seen in the third and fourth Gauss-Hermite velocity moments maps. The detection of these signatures may indicate the presence of a BBH currently, or at some earlier time, which depends on the rate of velocity phase space mixing following the BBH merger.

astro-ph.CO↗

arXiv2007

X-Ray Emission from Jet-Wind Interaction in Planetary Nebulae

We conduct 2D numerical simulations of jets expanding into the slow wind of asymptotic giant branch stars. We show that the post-shock jets' material can explain the observed extended X-ray emission from some planetary nebulae (PNs). Such jets are thought to shape many PNs, and therefore it is expected that this process will contribute to the X-ray emission from some PNs. In other PNs (not simulated in this work) the source of the extended X-ray emission is the shocked spherical wind blown by the central star. In a small fraction of PNs both sources might contribute, and a two-temperatures gas will fit better the X-ray properties than a one-temperature gas. A spacial separation between these two components is expected.

astro-ph↗