You are in: Instruments > GMOS > Hot News > News Update 27 September 2001

GMOS Hot News

Observations of Abell383 obtained during GMOS commissioning in August 2001

27 September 2001

Full frame	Magnified section
		A 60s acquisition image of the galaxy cluster Abell 383 (at a redshift of 0.19), taken with GMOS in the r-band. Faint gravitational arcs are visible towards the center of the image. The GMOS on-instrument wavefront sensor probe is also visible as it guides on a star in the field. The image quality in this image is 0.58". Three CCD chips make up the detector array, with a total of over 28 million pixels. The full-frame image covers an area of 5.5arcmin x 5.5arcmin with a pixel scale of 0.072 "/pixel.
		After moving the MOS-mask designed for this field into the light path, selected objects align with the slits. This mask has 20 slits, each 1.0" wide.
		The light is then dispersed to produce spectra of each of the selected objects. This Multi-Object spectrum is the combination of three half-hour exposures (longer wavelengths are to the left). Emission lines from the sky are visible as well as emission lines from the faint galaxies.
		This spectrum was extracted from just a small piece of one of the MOS spectra (roughly corresponding to one of the magnified sections shown above). The galaxy in this example has a magnitude of approximately r=21.5. This section of its spectrum shows a weak continuum with three emission lines, H-beta and the OIII doublet, at a redshift of 0.28. The galaxy is therefore more distant than the main galaxy cluster. This example shows only a tiny fraction of the spectral information contained in the full MOS frame!

Original Aug 27 2001; Isobel Hook
Last update September 27 2001; Inger Jørgensen