A questãode como os gLSBGs se formam éuma questãode debate ativo. Dois modelos populares foram propostos. No primeiro, o cena¡rio não catastra³fico, a lenta acumulaa§a£o de gás na gala¡xia leva ao seu crescimento.
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)
A gigante gala¡xia Malin 1 com baixo brilho nasuperfÍcie, conforme imageada pelo instrumento Megacam no telesca³pio Magellan / Clay de 6,5 m. Os astrônomos ficaram intrigados com a forma como esses sistemas gigantescos se formaram e concluaram um novo estudo que confirma que vários caminhos propostos são prova¡veis. Crédito: Harvard-Smithsonian Center for Astrophysics
Quarenta anos atrás, astrônomos usando novas técnicas de imagem sensaveis descobriram uma classe de gala¡xias grandes e fracas que eles chamaram de gala¡xias de baixo brilho. Gala¡xias gigantes de baixo brilho superficial (gLSBGs) são um subconjunto cujas massas são compara¡veis ​​a s da Via La¡ctea, mas cujos raios são dez vezes maiores, chegando a quatrocentos mil anos-luz. Esses gLSBGs levantam um problema para os astra´nomos: apesar de serem massivos, os discos de gala¡xias são (cinematicamente falando) relativamente inativos. O paradigma de formação usual para gala¡xias de alta massa as imagina evoluindo a partir de fusaµes de gala¡xias, um processo que agita o disco e deve torna¡-lo cinematicamente ativo. Além disso, a maioria dos gLSBGs são encontrados sem outras gala¡xias em suas vizinhana§as, sugerindo que as colisaµes provavelmente não foram importantes em sua formação.
A questãode como os gLSBGs se formam éuma questãode debate ativo. Dois modelos populares foram propostos. No primeiro, o cena¡rio não catastra³fico, a lenta acumulação de gás na gala¡xia leva ao seu crescimento. Em alternativa, o cena¡rio catastra³fico, um evento de fusão ocorreu no passado; a principal vantagem deste modelo éque ele se encaixa na estrutura atual de formação de gala¡xias. O astra´nomo do CfA Igor Chilingarian e seus colegas completaram observações a³pticas sensaveis de sete gLSBGs, tomando espectros em todos os dia¢metros desses sistemas gigantescos e taªnues, e combinando seus resultados com medições a³pticas e de ra¡dio de arquivo da emissão de hidrogaªnio ata´mico. Seu novo artigo éo mais recente de uma sanãrie de resultados sobre gLSBGs.
Os astrônomos usaram o grande conjunto de dados para testar esses dois cenários; eles também consideraram uma terceira opção na qual as gala¡xias se formam dentro de um halo de matéria escura incomumente raso e sua influaªncia gravitacional. (Acredita-se que todas as gala¡xias tenham halos de matéria escura; o halo da Via La¡ctea contanãm dez vezes mais massa do que a presente nas estrelas.) Eles concluem que todos os três cenários parecem estar operando, mas em situações diferentes. Para a maior parte da amostra, o processo mais prova¡vel foi a formação por crescimento por meio de acreção gradual após a formação inicial da gala¡xia. Para os gLSBGs restantes, o cena¡rio de fusão principal explicou melhor as observações, embora em alguns casos eles tenham descoberto que um halo esparso de matéria escura também poderia desempenhar um papel. Os cientistas também descobriram que pelo menos seis de seus sete hospedeiros gLSBGs núcleos gala¡cticos ativos (AGN), no entanto, seus núcleos de buracos negros supermassivos são muito menos massivos do que aqueles em gala¡xias normais de massa semelhante, o que implica que as fusaµes, mesmo que estivessem envolvidas na formação de gLSBGs, devem ter sido comparativamente modestas.