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matthewota
2009-Jul-23, 09:11 PM
Are Quasars now known to be normal in the process of the evolution of galaxies?
Do all galaxies have Quasars in their early histories? Are Quasars formed of black holes?

max8166
2009-Jul-23, 09:22 PM
There are too many galaxies to be sure, I think the answer is we just don't know:
http://en.wikipedia.org/wiki/Quasar

chornedsnorkack
2009-Jul-23, 10:07 PM
Are Quasars now known to be normal in the process of the evolution of galaxies?
Do all galaxies have Quasars in their early histories?

Not all galaxies have active galactic nuclei in their late histories.

antoniseb
2009-Jul-23, 10:17 PM
New member Infinite Rainbows left an ATM message in this thread which was removed.

StupendousMan
2009-Jul-24, 12:46 AM
Short answers:


Are Quasars now known to be normal in the process of the evolution of galaxies?

If you mean, "Is it common for galaxies to pass through a stage in their evolution during which a quasar appears in their nucleus?" the answer is, "Yes, many of the most massive galaxies do pass through such a phase."



Do all galaxies have Quasars in their early histories?


There is good evidence that most massive galaxies may go through a phase during which we would identify a quasar in their nuclei. But there is also some evidence that low-mass galaxies -- which are far more numerous than the high-mass ones -- may not pass through such a stage (since they appear not to have massive black holes, though it's not easy to prove the _absence_ of such bodies).


Are Quasars formed of black holes?

A supermassive black hole, accreting matter at a high rate, is the central engine of a quasar; so, yes.

chornedsnorkack
2009-Jul-24, 08:42 AM
There is good evidence that most massive galaxies may go through a phase during which we would identify a quasar in their nuclei. But there is also some evidence that low-mass galaxies -- which are far more numerous than the high-mass ones -- may not pass through such a stage (since they appear not to have massive black holes, though it's not easy to prove the _absence_ of such bodies).


Not easy, but not impossible, for nearby objects.

For example, the Milky Way is not a quasar. Nor is the Milky Way even a radio or Seyfert galaxy. Nevertheless, as intrinsically dim as it is compared to quasars or radio galaxies, Sagittarius A is one of the brightest radio sources in the sky.

We can see the nucleus of Andromeda Nebula, too. It is 100 times farther away than the nucleus of Milky Way, but it is visible, and a similar object.

However, if we look at Large Magellanic Cloud or Triangulum, there is no bright object like an active galactic nucleus. And there is no passive galactic nucleus, either: if a supermassive black hole were emitting no light or radio waves, it would still cause nearby stars to have a higher scatter of Doppler shifts. Triangulum has been searched for any spots with abnormal scatter of Doppler shift, and complete absence of abnormal mass concentrations can be confirmed.

Now, a massive black hole completely outside any galaxy, or in the outskirts of a galaxy devoid of nearby stars to show Doppler shift scatter, would be harder to see, and it could only be detected through gravitational lensing of background light. Do any such exist?

Spaceman Spiff
2009-Jul-24, 02:41 PM
A couple of comments.

If the mass accretion rate onto the smbh of the Milky Way were much higher than at present, it's luminosity could rival the brightest of Seyfert type AGN, up to ~200 billion solar luminosities. Not a quasar for sure, but the Galaxy would definitely know of its presence. There may well have been 1 or more such episodes in the history of the MW.

The quasar HE 0450-2958 (http://adsabs.harvard.edu/cgi-bin/nph-abs_connect?db_key=AST&db_key=PRE&qform=AST&arxiv_sel=astro-ph&arxiv_sel=cond-mat&arxiv_sel=cs&arxiv_sel=gr-qc&arxiv_sel=hep-ex&arxiv_sel=hep-lat&arxiv_sel=hep-ph&arxiv_sel=hep-th&arxiv_sel=math&arxiv_sel=math-ph&arxiv_sel=nlin&arxiv_sel=nucl-ex&arxiv_sel=nucl-th&arxiv_sel=physics&arxiv_sel=quant-ph&arxiv_sel=q-bio&sim_query=YES&ned_query=YES&adsobj_query=YES&aut_logic=OR&obj_logic=OR&author=&object=&start_mon=&start_year=2007&end_mon=&end_year=&ttl_req=YES&ttl_logic=AND&title=HE+0450-2958&txt_logic=OR&text=&nr_to_return=200&start_nr=1&jou_pick=ALL&ref_stems=&data_and=ALL&group_and=ALL&start_entry_day=&start_entry_mon=&start_entry_year=&end_entry_day=&end_entry_mon=&end_entry_year=&min_score=&sort=SCORE&data_type=SHORT&aut_syn=YES&ttl_syn=YES&txt_syn=YES&aut_wt=1.0&obj_wt=1.0&ttl_wt=0.3&txt_wt=3.0&aut_wgt=YES&obj_wgt=YES&ttl_wgt=YES&txt_wgt=YES&ttl_sco=YES&txt_sco=YES&version=1) is a very interesting object, recently thought to be a "naked" quasar, but now thought to be a part of a complex merging/star forming "mess".

matthewota
2009-Jul-24, 03:01 PM
Thanks for the answers. My college astronomy textbooks are a bit out of date.

chornedsnorkack
2009-Jul-24, 06:43 PM
A couple of comments.

If the mass accretion rate onto the smbh of the Milky Way were much higher than at present, it's luminosity could rival the brightest of Seyfert type AGN, up to ~200 billion solar luminosities. Not a quasar for sure, but the Galaxy would definitely know of its presence.

What is the present luminosity of the Milky Way core?

What is the present accretion rate?

parejkoj
2009-Jul-25, 05:37 AM
chornedsnorkack: Sgr A* has a bolometric luminosity of around 1033 erg/s, or roughly the same as our Sun. Here's a reference to a measurement of an X-ray flare from it in 2002 (http://adsabs.harvard.edu/abs/2003A%26A...407L..17P). Most of its energy is in X-ray and mm/radio emission, instead of the optical emission of our Sun. That corresponds to an accretion rate around a hundred-thousandth of a solar mass per year.

At the maximal possible accretion rate mentioned by Spaceman Spiff, our Black Hole would not be too far shy of the typical definition of a quasar. Personally, at those luminosities, they're all bright AGN (Active Galactic Nuclei) to me. The quasar/not-quasar dividing line for AGN is rather arbitrary.

It is certainly true that nearly all large galaxies went through a bright AGN phase during some part of their life. And that AGN phase almost certainly influenced the subsequent evolution of the galaxy by heating up, and blowing out gas that would otherwise have formed stars.