NASA rastreia buracos negros supermassivos em seu ciclo de colisão

• Milky Way, likely formed larger galaxies through collisions in the early Universe.
• These newly-discovered merging dwarf galaxies can be used as analogs for more distant ones that are too faint to observe.
• The dwarf galaxies are on collision courses and are found in the galaxy clusters Abell 133 and Abell 1758S.

Evidence for two pairs of supermassive black holes in dwarf galaxies on collision courses has been found with Chandra. The two pairs are shown in X-rays from Chandra and optical light from the Canada-France-Hawaii telescope. The merger on the left is in a late stage and was given the single name of Mirabilis. The other merger is in the early stages and the two dwarf galaxies are named Elstir (bottom) and Vinteuil (top). Astronomers think that dwarf galaxies – those about 20 times less massive than the Milky Way – grow through mergers with others. This is an important process for galaxy growth in the early Universe and this discovery provides examples for scientists to study in greater detail. Credit: X-ray: NASA/CXC/Univ. of Alabama/M. Micic et al.; Optical: International Gemini Observatory/NOIRLab/NSF/AURA

A new study using NASA’s Chandra X-ray Observatory has tracked two pairs of supermassive black holes in dwarf galaxies on collision courses. This is the first evidence for such an impending encounter, providing scientists with important information about the growth of black holes in the early Universe.

By definition, dwarf galaxies contain stars with a total mass less than 3 billion Suns — or about 20 times less than the Milky Way. Astronomers have long suspected that dwarf galaxies merge, particularly in the relatively early Universe, in order to grow into the larger galaxies seen today. However, current technology cannot observe the first generation of dwarf galaxy mergers because they are extraordinarily faint at their great distances. Another tactic — looking for dwarf galaxy mergers closer by — had not been successful to date.

O novo estudo superou esses desafios realizando um levantamento sistemático das observações profundas de raios-X do Chandra e comparando-as com dados infravermelhos do Wide Infrared Survey Explorer (WISE) da NASA e dados ópticos do Canada, France and Hawaii Telescope (CFHT).

O Chandra foi particularmente valioso neste estudo porque o material que envolve os buracos negros pode ser aquecido a milhões de graus, emitindo grandes quantidades de raios-X. A equipe procurou por pares de fontes brilhantes de raios-X em galáxias anãs em colisão como evidência de dois buracos negros e descobriu dois exemplos.

Evidências de um par de buracos negros supermassivos foram encontradas em galáxias anãs em ciclos de colisão com o Chandra. O par é visto em raios-X do Chandra e luz óptica do Telescópio Canadá-França-Havaí. A fusão à esquerda está em estágio avançado e recebeu o nome individual de Mirabilis. A outra fusão está em seus estágios iniciais e as duas galáxias anãs foram nomeadas Elstir (abaixo) e Vinteuil (topo). Os astrônomos acreditam que as galáxias anãs – aquelas 20 vezes menores que a Via Láctea – crescem por meio de fusões com outras. Este é um processo importante para o crescimento das galáxias no início do universo e esta descoberta fornece exemplos para os cientistas estudarem com mais detalhes. Crédito: Raios-X: NASA/CXC/Univ. Alabama / m. Micic et ai.; Óptica: Gemini Observatory International/NOIRLab/NSF/AURA

Um par está no aglomerado de galáxias Abell 133 localizado a 760 milhões de anos-luz da Terra, visto na imagem composta à esquerda. Dados de raios X do Chandra em rosa e dados ópticos do CFHT em azul. Este par de galáxias anãs parece estar nos estágios finais de uma fusão, exibindo longas caudas causadas por efeitos de maré da colisão. Os autores do novo estudo o batizaram de Mirabilis, depois que ele se tornou criticamente ameaçado[{” attribute=””>species of hummingbird known for their exceptionally long tails. Only one name was chosen because the merger of two galaxies into one is almost complete. The two Chandra sources show X-rays from material around the black holes in each galaxy.

X-ray and optical composite of Mirabilis. Credit: X-ray: NASA/CXC/Univ. of Alabama/M. Micic et al.; Optical: International Gemini Observatory/NOIRLab/NSF/AURA

The other pair was discovered in Abell 1758S, a galaxy cluster about 3.2 billion light-years away. The composite image from Chandra and CFHT is on the right, using the same colors as for Mirabilis. The researchers nicknamed the merging dwarf galaxies “Elstir” and “Vinteuil,” after fictional artists from Marcel Proust’s “In Search of Lost Time”. Vinteuil is the galaxy on the top and Elstir is the galaxy on the bottom. Both have Chandra sources associated with them, again from X-rays from material around the black holes in each galaxy. The researchers think these two have been caught in the early stages of a merger, causing a bridge of stars and gas to connect the two colliding galaxies from their gravitational interaction.

X-ray and optical composite of Elstir & Vinteuil. Credit: X-ray: NASA/CXC/Univ. of Alabama/M. Micic et al.; Optical: International Gemini Observatory/NOIRLab/NSF/AURA

The details of merging black holes and dwarf galaxies may provide insight to our Milky Way’s own past. Scientists think nearly all galaxies began as dwarf or other types of small galaxies and grew over billions of years through mergers. Follow-up observations of these two systems will allow astronomers to study processes that are crucial for understanding galaxies and their black holes in the earliest stages of the Universe.

Um artigo descrevendo essas descobertas foi publicado em uma edição recente da o[{” attribute=””>Astrophysical Journal.

Reference: “Two Candidates for Dual AGN in Dwarf-Dwarf Galaxy Mergers” by Marko Mićić, Olivia J. Holmes, Brenna N. Wells and Jimmy A. Irwin, 22 February 2023, The Astrophysical Journal.
DOI: 10.3847/1538-4357/aca1bb

The authors of the study are Marko Micic, Olivia Holmes, Brenna Wells, and Jimmy Irwin, all from the University of Alabama at Tuscaloosa.

NASA’s Marshall Space Flight Center manages the Chandra program. The Smithsonian Astrophysical Observatory’s Chandra X-ray Center controls science operations from Cambridge, Massachusetts, and flight operations from Burlington, Massachusetts.