First Results from Deimos Commissioning

Beginners Guide ("What in the world am I looking at??")

2D Spectra

1D Spectra

Beginners Guide

As you scroll down the page you will come across 2 different types ofimages. The first appears grainy and is organized in rows; it is referred to as 2D spectra. Each set of rows contains the visible spectrum (from approximately 6000A - 9000A) of one galaxy. If this confuses you, imagine that one long row has been chopped up into several smaller rows. Within each row the vertical axis contains the spatial information while the horizontal axis contains the wavelength information. So as you scroll down and come across a spectrum with two streaks of light in one row, you are seeing two galaxies very close together!

The second type of image, the one that looks more like a graph, is the 1D spectra, because the spatial information has been removed. What we see in the 1D spectra is the number of photons (roughly speaking) collected at each wavelength for a given galaxy. From the 1D spectra we can determine the redshift of the galaxy, i.e. how far away it is from us, by looking for characteristic emission or absorption lines.

Below I have given prime examples of 2D and 1D spectra for the most commonly observed emission and absorption lines.

H&K (CaII)




2D Spectra

**NOTE: Some of the 2D spectra have been cropped.

2 galaxies in 1 slitlet. Shown above is the OII doublet emission line. Both galaxies are at z=1.199

Rotation curves



Strong continuum, rotation is visible


z=1.02, strange OII.

z=1.21, 2 galaxies?




1D Spectra

z=.941 Check out that 4000A break!

z=0.72, smoothing = 10

AGN, z=??, smoothing = 20

Star, smoothing = 10

z=??, smooth = 15

maintained by Charlie Conroy