The spectrum of the quasar PKS 1251-407

The spectrum of the quasar PKS 1251-407 (in red) is compared to the observations done by GROND in the seven different passbands (in green). The close agreement between the GROND data and the spectrum shows the strength of the photometric redshift technique. The large decrease in the flux in the blue part of the spectrum (around 500 nm) is the so-called Lyman drop-out and is what allows to determine the distance of the object. In this case, the Lyman-alpha line of atomic hydrogen (rest wavelength 121.6 nm) is observed at around 660 nm, i.e. in the red spectral region, indicating a redshift of 4.46, or a distance of 12.3 billion of light-years. Light from this object started its long journey towards us less than 1.4 billion years after the Big Bang.



About the Image

Release date:6 July 2007
Related releases:eso0730
Size:953 x 646 px

About the Object

Name:PKS 1251-407
Type:Early Universe : Galaxy : Activity : AGN : Quasar
Distance:z=4.46 (redshift)
Quasars and Black Holes

Image Formats

Large JPEG
97.4 KB
Screensize JPEG
93.2 KB

Colours & filters

OpticalMPG/ESO 2.2-metre telescope
InfraredMPG/ESO 2.2-metre telescope


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