Using the Atacama Large Millimeter/submillimeter Array (ALMA) and the Subaru Telescope, astronomers have discovered a merging pair of gas-rich galaxies that existed 12.8 billion years ago and housed a faint central quasar that may be the ancestor of some of the brightest and most massive quasars in the early universe.
Artist's impression of the quasars HSC J121503.42-014858.7 and HSC J121503.55-014859.3. Image courtesy of Izumi others., doi:10.3847/1538-4357/ad57c6.
Quasars are luminous objects that gained energy from matter falling into supermassive black holes at the centers of galaxies in the early universe.
The most accepted theory is that when two gas-rich galaxies merge to form one larger galaxy, the gravitational interaction between the two galaxies causes gas to fall towards a supermassive black hole in one or both of the galaxies, triggering quasar activity.
To test this theory, Dr. Takuma Izumi of the National Astronomical Observatory of Japan used ALMA to study the oldest known pair of close quasars.
The quasars, named HSC J121503.42-014858.7 and HSC J121503.55-014859.3, were discovered by the Subaru Telescope's Hyper Suprime-Cam.
These objects are very faint, about 10 to 100 times fainter than highly luminous quasars at the same redshift.
“It is located approximately 12.8 billion light-years away, corresponding to the 'cosmic dawn' era when the universe was only 900 million years old, making it the farthest such quasar pair on record,” the astronomers said.
“Because of their faintness, we thought these objects were in the pre-merger stage, before the supermassive black holes rapidly grow.”
“However, observations with the Subaru Telescope only provide information about the central supermassive black hole, and it remains unclear whether the host galaxy is destined to merge and ultimately grow into a luminous quasar.”
“As a next step, we used the ALMA radio telescope to carry out observations of the host galaxies of these quasar pairs.”
“The results were surprising: the observed distribution of interstellar material and the nature of its motions indicated that these galaxies are interacting with each other.”
“They are definitely on a path to merge into one galaxy in the near future.”
“Furthermore, calculations from observational data reveal that the total gas mass of these galaxies – about 100 billion times the mass of the Sun – is comparable to or exceeds the gas mass in the host galaxies of most luminous quasars, which have extremely bright cores.”
“This enormous amount of matter should easily trigger and sustain the post-merger burst of star formation and fueling of the supermassive black hole.”
“These discoveries therefore represent a significant achievement in identifying the ancestors of luminous quasars and starburst galaxies, the most luminous objects in the early universe, from various perspectives, including galactic structure, motion and the amount of interstellar material.”
of Survey results Appears in Astrophysical Journal.
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Takuma Izumi others2024. Gas-rich galaxy merger harboring a low-luminosity twin quasar at z = 6.05: a likely progenitor of the most luminous quasars. ApJ 972, 116;doi:10.3847/1538-4357/ad57c6
Source: www.sci.news
