Background

To assist prospective DEIMOS observers in preparing for their runs, the DEEP2 team has generously shared information on the signal-to-noise ratio (S/N) achieved in their survey. The table and plot below report the measured S/N for a sample of 50,000 distant galaxies as a function of the source brightness. Observers wishing to estimate required exposure times to achieve a given S/N on marginally resolved objects with DEIMOS will find this information beneficial.

Plot

The blue line indicates the median S/N within each 0.5 mag bin as a function of the R magnitude. The red lines denote the interquartile range at each magnitude. The S/N is measured per pixel in a 1-hour exposure with the 1200G grating on DEIMOS, within the wavelength ranges 6600-6830 Å and 6960-7250 Å (to avoid sky lines). The R magnitude is measured on the AB system as described in Coil et al. 2004.

Table

The following table shows the same data in tabular format.

R(AB)	S/N per pixel in 1 hour
	Q1	Median	Q3
18.5	5.53	8.37	10.89
19.0	4.81	6.77	9.74
19.5	3.34	5.89	8.28
20.0	2.92	5.35	7.43
20.5	2.67	4.45	6.18
21.0	2.19	3.29	4.60
21.5	1.67	2.42	3.25
22.0	1.23	1.79	2.40
22.5	0.88	1.29	1.73
23.0	0.61	0.88	1.24
23.5	0.42	0.61	0.83
24.0	0.32	0.45	0.61

Acknowledgement

Michael Cooper of the DEEP2 Survey Team kindly provided the raw data for the plot.