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Astronomers discover the first galaxy whose ultraviolet luminosity is comparable to that of a quasar



Astronomers discover the first galaxy whose ultraviolet luminosity is comparable to that of a quasar

Left and center: Image of the sky area containing BOSS-EUVLG1, which stands out due to its blue color. Credit: DESI Legacy Imaging Surveys. Right: A drawing by the artist of the burst of star formation in BOSS-EUVLG1, which contains a large number of young massive stars and almost no dust. Credit: Gabriel Perez Diaz, SMM (IAC).

Using observations made with the Gran Telescopio Canarias (GTC) at the Roque de los Muchachos Observatory (Garafía, La Palma, Canary Islands) and the ATACAMA (ALMA) millimeter / submillimeter array in Chile, astronomers have found the first galaxy whose ultraviolet brightness is comparable to that of a quasar. The discovery was recently published in the journal Monthly notices of the letters of the Royal Astronomical Society.


The galaxy, called BOSS-EUVLG1, has a redshift of 2.47. This is a measure of the redness of light coming from the galaxy, and can be used to find its distance: the farther away the galaxy is, the greater the value. For BOSS-EUVLG1, a value of 2.47 means that the galaxy was observed when the universe was about 2,000 million years old, about 20% of its current age.

The large redshift and luminosity values ​​of BOSS-EUVLG1 led to its earlier classification in the BOSS (Baryon Oscillation Spectroscopic Survey) project as a quasar. From observations made with the OSIRIS and EMIR instruments on the GTC and the millimeter-wave telescope ALMA, the researchers showed that this is not a quasar, but in fact a galaxy with extreme, exceptional properties.

The study reveals that the high brightness of BOSS-EUVLG1 in ultraviolet and Lyman-alpha emissions is due to the large number of young, massive stars in the galaxy. This high luminosity, well above the range of other galaxies, gave rise to its initial identification as a quasar. In quasars, however, the high luminosity is due to the activity around the supermassive black holes in their nuclei, not to the formation of stars.

“BOSS-EUVLG1 appears to be dominated by a burst of young, very massive star formation, with almost no dust and very low metallicity,” explains Rui Marquis Chavez, a CAB researcher and former doctoral student at the Instituto de Astrofísica de Canarias and the University of La Laguna. (ULL), and the first author of the article.

The rate of star formation in this galaxy is very high, about 1,000 solar masses per year, which is about 1,000 times higher than in the Milky Way, although the galaxy is 30 times smaller. “This rate of star formation is comparable only to the brightest infrared galaxies known, but the absence of dust in BOSS-EUVLG1 allows its ultraviolet and visible radiation to reach us with almost no attenuation,” explains Ismail Perez Furnon. IAC researcher co-authored the article.

The results of the study suggest that BOSS-EUVLG1 is an example of the initial stages of the formation of massive galaxies. Despite its high luminosity and rate of star formation, its low metallicity indicates that the galaxy has hardly had time to enrich its interstellar medium with dust and newly formed metals. However, says IAC PhD student and co-author Camilo E. Jimenez Angel, “the galaxy will evolve into a dustier phase, similar to infrared galaxies. Also, its high brightness in UV will last only a few hundred million years, a very short period. from the evolution of the galaxy. “

“This would explain why other galaxies like BOSS-EUVLG1 have not been discovered,” said Claudio Dala Vecchia, an IAC researcher and co-author of the article.

BOSS-EUVLG1 was discovered by analyzing half a million spectra of galaxies and quasars in the BOSS project of the Sloan Digital Sky Survey (SDSS) and observations with large telescopes such as GTC and ALMA.


Interstellar medium of SDSS J2310 + 1855, studied with ALMA


More information:
The discovery of the most radiant star-forming galaxy with UV-Ly-alpha: a young, low-dust and metallic star burst with QSO-like glare. Archive: arxiv.org/abs/2009.02177v1

Provided by the Instituto de Astrofísica de Canarias

Quote: Astronomers discover the first galaxy whose ultraviolet luminosity is comparable to that of a quasar (2020, September 28), extracted on September 28, 2020 from https://phys.org/news/2020-09-astronomers-galaxy- ultraviolet-luminosity-quasar .html

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