{[ promptMessage ]}

Bookmark it

{[ promptMessage ]}

lect 19 part 1

lect 19 part 1 - Quasars and their host galaxies It is very...

Info iconThis preview shows pages 1–3. Sign up to view the full content.

View Full Document Right Arrow Icon
1 Quasars and their host galaxies • It is very difficult to observe the “host galaxy” because the quasar’s light overwhelms light from the galaxy’s stars • In 1980’s, astronomers showed that the “fuzz” around quasars show stellar absorption and that the absorption lines of the stars have the same redshift as the Quasar’s emission lines Properties of Host Galaxies • Relatively nearby radio-quiet quasars (z < 0.2) tend to be located in spiral galaxies • Radio-loud quasars as well as more distant radio-quiet quasars tend to be located in ellipticals • A large percentage of the host galaxies have distorted shapes (or peculiar shapes). Many have companion galaxies (suggesting a link between collisions or merging and the quasar) • Clues to what quasars are come from a class of galaxies that are intermediate in luminosity between quasars and normal galaxies: Seyferts and radio galaxies Seyfert galaxies seem to be nearby, low-luminosity, radio-quiet quasars Seyfert galaxies are spiral galaxies with bright nuclei that are strong sources of radiation (and strong emission lines) •A few percent of the most luminous spiral galaxies are Seyfert. •In fact there is no sharp dividing line between the properties of Seyferts and those of quasars •Like radio-quiet quasars Seyfert tend to have only weak radio emission and like quasars, some Seyferts are members of interacting pairs of exhibit the vestiges of mergers or collisions
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
2 Radio galaxies are elliptical galaxies located midway between the lobes of a double radio source • Most of the light from the central regions is thermal radiation (with a spectrum like that of a blackbody, it only depends on the object’s temperature). There are also absorption lines in the spectrum which indicates that this radiation is due to stars crowded in the galaxy’s center • But the light from the jet is nonthermal radiation (this energy is NOT due to random thermal motion and has a very different spectrum that thermal radiation). It is synchroton radiation Synchrotron radiation is produced by high-speed particles traveling in a strong magnetic field Relativistic particles are ejected from the nucleus of a radio galaxy along two oppositely directed beams The radiation of the jet is non-thermal and
Background image of page 2
Image of page 3
This is the end of the preview. Sign up to access the rest of the document.

{[ snackBarMessage ]}

Page1 / 13

lect 19 part 1 - Quasars and their host galaxies It is very...

This preview shows document pages 1 - 3. Sign up to view the full document.

View Full Document Right Arrow Icon bookmark
Ask a homework question - tutors are online