Quasar Caught Building Future Home Galaxy

The 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

35 Radio Observatories Link to Break Record

Ever wondered what the largest telescope on the Earth is? Well, this coming Wednesday and Thursday of this week, the largest telescope ever assembled here will take observations for a whole day. How big is the telescope? About the size of the whole Earth! 35 radio telescopes on 7 continents will link together for one whole day in an effort to observe distant quasars as part of an initiative to improve the reference frame that scientists use to measure positions in the sky.

Radio telescopes in Asia, Australia, Europe, North America, South America, Antarctica, and in the Pacific will all be linked together to measure the same 243 quasars over a 24-hour period. Quasars are galaxies that have a supermassive black hole at the center, which has strong emissions in the radio spectrum. The quasars being monitored are so far away from the Earth that they appear to be motionless in the sky. This makes them a perfect candidate for setting up a grid in the sky to use as a frame of reference, against which the positions of other objects can be determined.

This monitoring session comes out of a meeting of the International Astronomical Union in August, during which it was decided to start using a set of 295 quasars as a celestial reference frame starting January 1st, 2010. This is not a new reference frame to be used by astronomers – the current one was adopted in 1998 –  but an important update to the existing reference frame, the International Celestial Reference Frame.

The session, called the Very Large Astrometry Session is coordinated by the International VLBI Service for Geodesy and Astrometry. Several of the participating observatories will have live webcams running during the event (check for the observatory in your language!), and a public outreach page on the event,  hosted by the Bordeaux Observatory, can be found here. The public outreach page will post images as they are taken during the session, with information about observation coordinates.

Radio telescopes like the Very Long Base Array in the United States already link together observatories that are far apart to take observations. This technique is called very long baseline radio interferometry (VLBI), and allows for the use of smaller telescopes that are distant from one another to be linked together and have the same angular resolution as if they were one larger telescope. Doing these observations all in one go will reduce some of the errors that occur when disparate observatories take images at different times.

The previous record for radio observatories linked together to create a larger telescope for one monitoring session is 23. That means that this observing session will beat that record by a whopping 12 additional observatories. Even with this unprecedented amount of observatories monitoring the quasars, there will be a few gaps in the sky, mostly in the Southern hemisphere. Only 243 of the total 295 quasars in the reference frame will be observed this week, though that will break another record for the amount of objects observed in one session using this method. The image below depicts the locations of the participating observatories.A map of the observatories participating in the Very Large Astrometry Session. Check your local listings for live webcam images! Image Credit:IYA09

By taking data on the 243 selected quasars, astronomers will be able to more accurately pinpoint objects in the sky in all wavelengths, and gather more precise data. For instance, many objects of scientific interest are monitored by separate telescopes operating in the visible, radio, x-ray and infrared wavelengths. Having a more accurate frame of reference to tell these different telescopes where to point in the sky will improve the ability of the different telescopes to gather information from the same place in space.

Source: NRAO, IVS