Quasar Caught Building Future Home Galaxy

by Nicholos Wethington on December 1, 2009

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An artist's impression of how quasars may be able to construct their own galaxies. Image Credit: ESO/L. CalcadaThe birth of galaxies is quite a complicated affair, and little is known about whether the supermassive black holes at the center of most galaxies formed first, or if the matter in the galaxy accreted first, and formed the black hole later. Observations of the quasar HE0450-2958, which is situated outside of a galaxy, show the quasar aiding a nearby galaxy in the formation of stars. This provides evidence for the idea that supermassive black holes can ‘build’ their own galaxies.

The quasar HE0450-2958 is an odd entity: normally, supermassive black holes – also known as quasars – form at the center of galaxies. But HE0450-2958 doesn’t appear to have any host galaxy out of which it formed. This was a novel discovery in its own right when it was made back in 2005. Here’s our original story on the quasar, Rogue Supermassive Black Hole Has No Galaxy.

The formation of the quasar still remains a mystery, but current theories suggest that it formed out of cold interstellar gas filaments that accreted over time, or was somehow ejected from its host galaxy by a strong gravitational interaction with another galaxy.

The other oddity about the object is its proximity to a companion galaxy, which it may be aiding to form stars. The companion galaxy lies directly in the sights of one of the quasar’s jets, and is forming stars at a frantic rate. A team of astronomers from France, Germany and Belgium studied the quasar and companion galaxy using the Very Large Telescope at the European Southern Observatory. The astronomers were initially looking to find an elusive host galaxy for the quasar.

The phenomenon of ‘naked quasars’ has been reported before, but each time further observations are made, a host galaxy is found for the object. Energy streaming from the quasars can obscure a faint galaxy that is hidden behind dust, so the astronomers used the VLT spectrometer and imager for the mid-infrared (VISIR). Mid-infrared observations readily detect dust clouds. They combined these observations with new images obtained from the Hubble Space Telescope in the near-infrared.A color composite image of the quasar in HE0450-2958 obtained using the VISIR instrument on the Very Large Telescope and the Hubble Space Telescope. Image Credit: ESO

Observations of HE0450-2958, which lies 5 billion light years from Earth, confirmed that the quasar is indeed without a host galaxy, and that the energy and matter streaming out of the jets is pointed right at the companion galaxy. This scenario is ramping up star formation in that galaxy: 340 solar masses of stars a year are formed in the galaxy, one-hundred times more than for a typical galaxy in the Universe. The quasar and the galaxy are close enough that they will eventually merge, finally giving the quasar a home.

David Elbaz of the Service d’Astrophysique, who is the lead author of the paper which appeared in Astronomy & Astrophysics, said “The ‘chicken and egg’ question of whether a galaxy or its black hole comes first is one of the most debated subjects in astrophysics today. Our study suggests that supermassive black holes can trigger the formation of stars, thus ‘building’ their own host galaxies. This link could also explain why galaxies hosting larger black holes have more stars.”

‘Quasar feedback’ could be a potential explanation for how some galaxies form, and naturally the study of other systems is needed to confirm whether this scenario is unique, or a common feature in the Universe.

Source: ESO, Astronomy & Astrophysics

Jon Hanford December 4, 2009 at 6:50 AM

We may be looking at images of the inner accretion disk of Sgr A* within the next few years. Plans for imaging the accretion disk down to the event horizon in submillimeter wavelengths were discussed in a recent paper: http://arxiv.org/abs/0906.3899 . This would be a monumental achievement for astronomy, much like the discovery of the first exoplanets. Probably more questions will be raised than answered, but that’s how science works.

Btw, the paper gives a brief overview of accretion models for black holes in Section 2.4.

DrFlimmer December 4, 2009 at 8:39 AM

@ Jon Hanford:

At least, we would finally prove without a doubt the existence of black holes. This is a task I’d really liked to be accomplished.

Probably more questions will be raised than answered, [...]

Thank god, it works like that. Running out of questions would be the last thing science wants to encounter. (hm. Literally, that is correct. :D )

Hannes December 6, 2009 at 2:47 PM

Thanks for the picture IVAN3MAN, but there is nothing conclusive about the data from STIS.

M84 shows indeed many features of rotational gas. The instruments measured the increasing velocity of a disk of gas ORBITING the black hole. There is no measurement of inflow.

Chandra showed that M84 has 4 “bubbles”, from which there is dissipating energy in waves.
These waves tend to be concentrated near the center of M84 and in the direction perpendicular to the bubbles outflow. The waves detach directly from the AGN-inflated cavities.

So there is confirmed outflow, and orbiting gas. But no picture showing inflow.

DrFlimmer December 7, 2009 at 12:28 PM

@ Hannes:

As said before, this is a matter of resolution. And, although our telescopes are quite fancy now, their resolution is still too low to actually get a picture of an accretion disk.

Still: The physical basics are well known. The accretion model says that the plasma will circle faster as closer it is to the black hole. The next thing is that it will become fairly hot and will radiate far in the X-ray regime. Another point is: In order to get an inflow the plasma must get rid of its angular momentum. This can be done by friction (heat), twisted magnetic fields and outflows (uncollimated, or collimated; the latter would be jets).

This is the picture, and all of its features are seen in AGN and on other occasions.
I should note that many details are still a matter of strong research. E.g., the formation and collimation of jets is still quite unknown. Also how they stay so narrow for such long distances (Mpc scales!), is not yet fully understood!

But maybe we can resolve Sgr A* in the next few years! THAT would be awesome!

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