Observationally what is a quasar What role do black holes pl

Solution

Quasar are the most energetic and distant members of a class of objects called active galactic nuclei (AGN). Quasars are extremely luminous and were first identified as being high redshift sources ofelectromagnetic energy, including radio waves and visible light, that appeared to be similar to stars, rather than extended sources similar to galaxies. Their spectra contain very broad emission lines, unlike any known from stars, hence the name \"quasi-stellar.\" Their luminosity can be 100 times greater than that of the Milky Way.Most quasars were formed  Most quasars were formed approximately 12 billion years ago, and they are normally caused by collisions of galaxies, with the galaxies\' central black holes merging to form either a supermassive black hole or a binary black hole system.

Super massive black holes at the galactic centres are the \"engines\" that power the quasars.

Hubble observations have been fundamental in the study of the jets and discs of matter around a number of black holes. Accurate measurements of the masses have been possible for the first time. Hubble has found black holes 3 billion times as massive as our Sun at the centre of some galaxies. While this might have been expected, Hubble has surprised everyone by providing strong evidence that black holes exist at the centres of all large galaxies and even small galaxies. Hubble also managed not only to observe the jets created by black holes but also the glowing discs of material surrounding a supermassive black hole.

Furthermore, it appears that larger galaxies are the hosts of larger black holes. There must be some mechanism that links the formation of the galaxy to that of its black hole and vice versa. This has profound implications for theories of galaxy formation and evolution and is an ongoing area of research in astronomy.

Most galaxy evolutionary models require quasar feedback to regulate star formation in their host galaxies. In particular, at high redshift, models expect that feedback associated with quasar-driven outflows is so efficient that the gas in the host galaxy is largely swept away or heated up, hence suppressing star formation in massive galaxies. We observationally investigate this phenomenon by using VLT-SINFONI integral field spectroscopy of the luminous quasar 2QZJ002830.4-281706 at z=2.4. The spectra sample the optical emission lines redshifted into the near-IR. The 5007 emission-line kinematics map reveals a massive outflow on scales of several kpc. The detection of narrow Halpha emission reveals star formation in the quasar host galaxy, with SFR=100 Msun/yr. However, the star formation is not distributed uniformly, but is strongly suppressed in the region with the highest outflow velocity and highest velocity dispersion. This result indicates that star formation in this region is strongly quenched by the quasar outflow, which is cleaning the galaxy disk of its molecular gas. This is one of the first direct observational proofs of quasar feedback quenching the star formation at high redshift.