Do quasars have broad emission lines?
Broad absorption lines (BALs) seen in ~23% of quasars; similar range of widths, outflow velocities up to 0.2c. Broad emission lines (BELs) usually single-peaked. emission line peak is usually blueshifted from the Mg II peak.
What is a broad absorption line?
Broad absorption line (BAL) quasars are those quasars which show ultraviolet (UV) absorption troughs thousands of km s−1 wide (e.g. Lynds 1967; Allen et al. 2011), widths for which the accretion process in quasars is thought to be ultimately responsible.
What do spectral lines in quasars indicate?
Spectra of the nuclei in Seyferts are non-stellar in nature and display information concerning the emitting regions. From the Doppler effect, spectral lines that are broad in wavelength are emitted from gas clouds moving with high velocities. Likewise, low velocity clouds emit narrow lines.
What are the main characteristics of quasars?
1.4 Physical Characteristics: Quasars
- star-like object identified with a radio source;
- variable light;
- large ultraviolet flux of radiation;
- broad emission lines in the spectra with absorption lines in some cases;
- large redshift.
Why do quasars have unusual spectral lines?
With quasars, this radiation produces emission not only at radio wavelengths, but also in the visible and x-ray regions of the spectrum. The quasar emission lines, that do not come from the same region as the x-ray and synchrotron radiation, must originate from ionized gas at not too high a temperature.
What spectrum do quasars have?
Quasars can be detected over the entire observable electromagnetic spectrum, including radio, infrared, visible light, ultraviolet, X-ray and even gamma rays.
What kind of information might we get from study of quasar absorption lines?
The shape of an absorption line can therefore tell us the processes involved in the absorption, and gives us information about the conditions in the absorbing IGM gas. It can also tell us the relationship between the strength of the line and the column density of the absorbing cloud.
Do quasars have spectral lines?
Quasars are at the distances of galaxies, but are certainly not galaxies, as these contain stars and therefore have absorption lines, whereas quasar spectra are dominted by emission lines.
What are quasar absorption lines?
Quasar radiation is absorbed mainly along the entire line of sight of the “inter-galactic medium” (IGM), including intervening galaxies and the ISM of the Milky Way. PKS 0454+0339, z = 1.34. Typical moderate-z quasar spectrum showing the dominant Lyα emission line and many absorption lines, especially many Lyα.
What is a quasar simple definition?
quasar, an astronomical object of very high luminosity found in the centres of some galaxies and powered by gas spiraling at high velocity into an extremely large black hole.
What is the best characteristic of a quasar?
“Quasars are capable of emitting hundreds or even thousands of times the entire energy output of our galaxy, making them some of the most luminous and energetic objects in the entire universe,” according to NASA.
Why do quasars have emission lines?
The most widely accepted reason is that quasars, and other types of active galaxies, derive their energy output from an enormous black hole at the center of a galaxy. This black hole must be very large, at least a billion solar masses.
Do quasars have absorption lines?
Absorption lines were found in all quasars with z > 2 because (1) the strong ultraviolet resonance lines of abundant ions in the intergalactic medium were redshifted to wavelengths that could be observed with ground-based telescopes, and (2) the number density of lines was found to increase with redshift.
What is a quasar definition for kids?
Quasars are the brightest objects in the universe. They produce huge amounts of energy. Some of them produce up to 100 times more energy than our entire Milky Way Galaxy! A quasar is always found near a supermassive black hole. Every galaxy has a supermassive black hole at its center.
Are quasars black holes?
A quasar is a supermassive black hole feeding on gas at the center of a distant galaxy. Quasar is short for quasi-stellar radio source, because astronomers first discovered quasars in 1963 as objects that looked like stars but emitted radio waves.
How do quasars emit radiation?
The radio radiation from quasars is in the form of synchrotron radiation, which is when a charged particle enters a magnetic field, moves around the lines of force, speeds up close to the speed of light, and radiates energy.
What is a quasar and how is it formed?
A quasar is formed when a super massive black hole at the centre of a galaxy has enough material around it to fall into the accretion disc to generate the energy to power it. The only galaxies with enough material to create a quasar are young galaxies and colliding galaxies.
Is the Milky Way a quasar?
For the most part, this supermassive black hole is inactive, although it’s known to swallow sips of hydrogen gas occasionally. But, if astronomers at the Harvard-Smithsonian Center for Astrophysics (CfA) are correct, the Milky Way recently (by cosmic standards) went through a quasar stage in its evolution.
Do quasars emit radio waves?
With quasars, this radiation produces emission not only at radio wavelengths, but also in the visible and x-ray regions of the spectrum.
What are broad absorption-line quasars?
Broad absorption-line (BAL) quasars are quasars whose spectra exhibit broad absorption lines that are blueshifted relative to the quasar’s rest frame, resulting from gas flowing outward from the active nucleus in the direction toward the observer. Broad absorption lines are found in about 10% of quasars,…
What is a weak emission line quasar?
Weak emission line quasars are quasars having unusually faint emission lines in the ultraviolet/visible spectrum. The energetic radiation of the quasar makes dark galaxies glow, helping astronomers to understand the obscure early stages of galaxy formation.
Do all quasars have radio emission?
A cosmic mirage known as the Einstein Cross. Four apparent images are actually from the same quasar. Later it was found that not all quasars have strong radio emission; in fact only about 10% are “radio-loud”.
What is the difference between radio-loud and radio-quiet quasars?
Radio-loud quasars are quasars with powerful jets that are strong sources of radio-wavelength emission. These make up about 10% of the overall quasar population. Radio-quiet quasars are those quasars lacking powerful jets, with relatively weaker radio emission than the radio-loud population.