Categories: galaxies

A Galaxy has been Found That’s as Bright as a Quasar… But it’s Not a Quasar

Astronomers have found a new type of galaxy that is very old, very distant and very bright in ultraviolet light. This is somewhat an unusual combination, and so when this bright galaxy was first detected, the team of researchers who found it first thought it was a quasar. But detailed study revealed it was actually a galaxy with some other unusual features, which contributes to its brightness: it is busy with star formation, it has almost no dust.

As of now, this galaxy – with the license plate-type name of BOSS-EUVLG1 – appears to be the only one of its kind.   

“BOSS-EUVLG1 seems to be dominated by a burst of formation of young, very massive stars, with hardly any dust, and with a very low metallicity,” said Rui Marques Chaves, a researcher at the Center for Astrobiology (CAB) in Madrid, Spain, lead author on an article published in the journal Monthly Notices of the Royal Astronomical Society Letters.

BOSS-EUVLG1 was discovered during analysis of half a million galaxies and quasars in the BOSS project of the Sloan Digital Sky Survey (SDSS). The Baryon Oscillation Spectroscopic Survey (BOSS) was designed to measure the expansion rate of the Universe, and it’s been mapping the spatial distribution of luminous red galaxies (LRGs) and quasars.  

The team used a variety of telescopes to study BOSS-EUVLG1: the Gran Telescopio Canarias (GTC), at the Roque de los Muchachos Observatory, (Garafía, La Palma, Canary Islands), and with the ATACAMA Large Millimetre/submillimetre Array (ALMA), in Chile.

Image of the region of the sky containing BOSS-EUVLG1 and artist`s drawing of the burst of star formation in BOSS-EUVLG1. Credit: DESI Legacy Imaging Surveys/Gabriel Pérez Díaz, SMM (IAC).

BOSS-EUVLG1, has a red-shift of 2.47, which means that we are seeing it when the universe was about 2 thousand million years old, or around 20% of its present age. The red-shift is a measure of the reddening of the light coming from the galaxy, and can be used to find its distance: the further away the galaxy, the greater the value.

The team said that the large values of redshift and luminosity of BOSS-EUVLG1 caused it to be originally classified as a quasar. High luminosity in quasars is due to the activity around the supermassive black holes in their nuclei.  However, from the observations made with the OSIRIS and EMIR instruments on the GTC, and with the millimeter wave telescope ALMA, the researchers have shown that it is not a quasar but in fact a galaxy with “extreme, exceptional properties.”

The team’s study revealed that the high luminosity of BOSS-EUVLG1 is due to the large number of young, massive stars in the galaxy. The rate of star formation in this galaxy is very high, around a thousand solar masses per year, around a thousand times higher than that in the Milky Way, although BOSS-EUVLG1 is 30 times smaller.

“This rate of star formation is comparable only to the most luminous infrared galaxies known, but the absence of dust in BOSS-EUVLG1 allows its ultraviolet and visible emission to reach us with hardly any attenuation,” said Ismael Pérez Fournon, an IAC researcher and a co-author of the article.

The team said their research suggests that BOSS-EUVLG1 is an example of the initial phases of the formation of massive galaxies. In spite of its high luminosity and star formation rate, its low metallicity shows that the galaxy has hardly had time to enrich its interstellar medium with dust and newly formed metals.

But the team wrote that eventually the galaxy will evolve towards a dustier phase, and its high luminosity in the UV will last only a few hundred million years, a very short period in the evolution of a galaxy.

“This would explain why other galaxies similar to BOSS-EUVLG1 have not been discovered,” said Claudio Dalla Vecchia, a researcher at the IAC, and another co-author.

Source: Instituto de Astrofisica de Canaraias (IAC)

Nancy Atkinson

Nancy has been with Universe Today since 2004. She is the author of a new book on the Apollo program, "Eight Years to the Moon," which shares the stories of 60 engineers and scientists who worked behind the scenes to make landing on the Moon possible. Her first book, "Incredible Stories from Space: A Behind-the-Scenes Look at the Missions Changing Our View of the Cosmos" tells the stories of those who work on NASA's robotic missions to explore the Solar System and beyond.

Recent Posts

The UK is Considering Nuclear Propulsion in Space

The UK Space Agency recently contracted with the British Rolls Royce company to research nuclear…

21 hours ago

James Webb Unfolds Sunshield

It’s almost time. Soon the James Webb Space Telescope will be on its way to…

23 hours ago

Thanks to Perseverance, We’re Finally Going to Hear What Mars Sounds Like

Many consider the various rovers we’ve sent to Mars as the next best thing to…

1 day ago

NASA Has Given Up on Trying to Deploy InSight’s Mole

It's always a sad day when a mission comes to an end. And it's even…

2 days ago

Mars is Still an Active World. Here’s a Landslide in Nili Fossae

A image released by the MRO mission shows a landslide near the location where the…

2 days ago

Astronomers see a Hint of the Gravitational Wave Background to the Universe

Astronomers have found evidence of faint gravitational waves using an array of pulsars in our…

2 days ago