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 SIGNIFICATIVE FRACTION OF BARYONS RESIDE IN THE FILAMENTS OF THE COSMIC WEB

(Credit: NASA, ESA, and E. Hallman (University of Colorado, Boulder) Observations of the cosmic microwave background indicate that baryons (protons, neutrons, etc., - the ordinary matter just to understand) occupies only 5% of the total energy content of the Universe (95% is dark matter and dark energy). However in the local universe approximately half of this "ordinary" matter it has never been observed.

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.

A Sapphire Super-Earth

Twenty-one light years away, in the constellation Cassiopeia, a planet by the name of HD219134 b orbits its star with a year that is just three days long. With a mass almost five times that of Earth, it is what is known as a super-Earth. Unlike our planet, however, these super-Earths were formed at high temperatures close to their host star and contain high quantities of calcium, aluminum and their oxides – including sapphire and ruby. HD219134 b is one of three candidates likely to belong to a new, exotic class of exoplanets. These objects are completely different from the majority of Earth-like planets. They have 10 to 20 percent lower densities than Earth. Researchers looked at different scenarios to explain the observed densities. For example, a thick atmosphere could lead to a lower overall density. But two of the exoplanets studied, 55 Cancri e and WASP-47 e, orbit their star so closely that their surface temperature is almost 3,000 degrees and they would have lost this ...

SpaceTime

Search This Blog