IR spectrum of radio galaxy at z=2.4

Montage of low resolution (R ~ 500) spectra that cover most of the 1 - 2.5 µm range of the radio galaxy MRC0406-244, as well as two extremely red (colour index R-K > 5) galaxies below and an anonymous galaxy above. The fact that these, and other very red galaxies, are found so close to the radio galaxy on the sky has led to speculation that they may be members of a cluster at the same redshift. The radio galaxy spectrum is characterized by a number of bright "blobs" which are due to the emission lines [O II] (from ionized oxygen), H-beta (hydrogen), [O III] (double ionized oxygen), [O I] (atomic oxygen), Halpha and [S II] (ionized sulphur) whose wavelengths fall in the visible spectrum of objects at rest, but are shifted into the infrared in this case due to the high recession speed of the radio galaxy. These lines can be seen more clearly in the extracted spectrum shown in the lower panel. They confirm the high redshift of the radio galaxy and provide more detailed information about its nature. The fact that neither of the two very red objects shows any of these emission lines appears to exclude the possibility that they are active or star-forming galaxies at the same redshift, but still leaves their actual nature and distance unclear. These spectra were obtained using the low resolution spectroscopic mode and with total integration times of 2 hours in the J band (right) and 1 hour in each of the H (middle) and K (left) bands.

Crédito:

ESO

Sobre a imagem

Id:eso9920o
Tipo:Carta
Data de divulgação:27 de Fevereiro de 1999
Notícias relacionadas:eso9920, eso9914
Tamanho:3000 x 2195 px

Sobre o objeto

Nome:Spectrum
Tipo:Early Universe : Galaxy
Distância:z=2.44 (desvio para o vermelho)
Categoria:Galaxies

Formatos de imagens

JPEG grande
2,1 MB

Cores e filtros

BandaTelescópio
Infravermelho
Near-IR
Very Large Telescope