RELATION BETWEEN TIDAL DISRUPTION EVENTS AND HOST GALAXIES

Image: Artistic illustration of a black hole divouring a star. Credit: NASA/Goddard Space Flight Center/CI Lab

A tidal disruption event occurs when a star gets close enough to a supermassive black hole's event horizon and is pulled apart by the black hole's tidal forces.
In a recent paper (French, Arcavi & Zabludoff, 2016 ApJL) the authors show that the tidal disruption events occur more frequently in host galaxies with strong Balmer line absorption. This feature indicates low levels of current star formation.

The Balmer lines in atomic physics, is the designation of one of a set of six named series describing the spectral line emissions of the hydrogen atom. The Balmer series is characterized by the electron transitioning from n > 2 to n = 2, where n refers to the radial quantum number or principal quantum number of the electron.

In the simplified Rutherford Bohr model of the hydrogen atom, the Balmer lines result from an electron jump between the second energy level closest to the nucleus, and those levels more distant. Shown here is a photon emission. (https://en.wikipedia.org/wiki/Balmer_series)

The connection tidal-disruption/host-galaxy may be due to the fact that these host galaxies have had a recent galaxy-galaxy merger. Such event increases the possibility of formation of black-hole binaries, perturbed stellar orbits and a spatially-concentrated population of A giant stars.

Figure: Tidal disruption of a star. Credit: NASA/Goddard Space Flight Center/Swift

▪ French, Arcavi & Zabludoff (ApJL) - Tidal drisuption events prefer unusual host galaxies. (arXiv)

Comments

A UNIVERSE WITHOUT A CENTER?

Image Credit: Eugenio Bianchi, Carlo Rovelli & Rocky Kolb. According to the standard theories of cosmology, there is no center of the universe. In a conventional explosion, material expand out from a central point and the instinct suggests that with the Big Bang happened something similar. But the Big Bang was not an explosion like that at all: it was an explosion of space, not an explosion in space . The Big Bang happened everywhere in the Universe.

UNIVERSE IS FINITE OR INFINITE?

Art by Moonrunner Design At present there is no answer to this question. However I will try to list the hypothesys currently on the table with related issues.

New research looks at how ‘cosmic web’ of filaments alters star formation in galaxies

Cosmic Web. Credit: NASA Astronomer Gregory Rudnick sees the universe crisscrossed by something like an interstellar superhighway system. Filaments — the strands of aggregated matter that stretch millions of light years across the universe to connect galaxy clusters — are the freeways. “Galaxies will flow along filaments from less dense parts of the universe to more dense parts of the universe, kind of like cars flowing down a highway to the big city. In this case, they are going toward big clusters, being pulled by the gravity of those large concentrations of matter,” he said. “I’m interested in how galaxies are affected by the regions in which they live,” Rudnick said. “Filaments are the first place where galaxies come into contact with higher density regions of the universe. If a galaxy in a ‘rural’ part of the universe enters a dense part, I want to know how its properties change — for example, does it change the number of stars it forms, or does its shape get altered? Us...

SpaceTime

Search This Blog