IRCS camera filters

The following table lists the filters available in the camera section of IRCS, together with their sensitivities. The transmission curves of each filter are available as plots or ASCII lists (lists kindly provided by Alan Tokunaga of the IRTF) if indicated in the respective columns.

All sensitivity figures are for 5 sigma detections in 1 hour of on-source integration with the infrared secondary mirror. They assume background-limited performance (see the guide to exposure times). Point source sensitivities assume 0.5'' seeing and a 1.0'' diameter extraction aperture; extended source sensitivities are per pixel (the first column is for the 20 mas pixel scale, the second for the 52 mas pixel scale); binning over N pixels will improve the sensitivity by 1.25 log N mag.

[Note: The thermal background level was recovered to low level one before 2005 (See Figure) since the image rotator was recoated and reinstalled in July, 2008. The sensitivities in tables are revised based on new low thermal background levels.]

Broad-band filters

Observers should be aware that variations in the strength of the OH airglow can cause changes of up to 1 mag in the sky background, with significant changes in sensitivity.


Filter			Wavelength (um)		Sensitivity			mag for 1 e^-/s
Filter			Wavelength (um)		(mag)	(mag/arcsec²)
Name	Plot	List	Centre	Width	(mag)	20 mas	52 mas
z			1.033	0.073	23.9	19.9	20.9	25.7
J			1.25	0.16	23.6	19.6	20.6	26.3
H			1.63	0.30	22.8	18.6	19.6	26.2
H+K'			1.89	0.82	22.7	18.5	19.5	25.9
K'			2.12	0.35	22.6	18.4	19.4	25.6
K			2.20	0.34	22.3	18.2	19.2	25.5
L'⁽¹⁾			3.77	0.70	17.1	13.3	14.3	24.6
M'⁽²⁾			4.68	0.24	14.6	10.8	-	22.6

(1) L' observation with the 52 mas pixel scale is limited to a maximum 512x512 pixel subarray.
(2) M' observation is limited to 20 mas pixel scale mode.

Narrow-band filters


Filter			Wavelength (um)		Sensitivity			flux for 1 e^-/s (uJy)
Name	Plot	List	Centre	Width	(uJy)	(uJy/arcsec²)		flux for 1 e^-/s (uJy)
CH₄ short			1.570	0.100	1.7	60	23	0.06
H cont			1.573	0.020	3.7	130	52	0.3
CH₄ long			1.690	0.100	1.7	60	23	0.06
[Fe II]			1.644	0.026	3.3	120	47	0.4
H₂ 1-0			2.122	0.032	3.0	110	44	0.4
Br gamma			2.166	0.032	3.0	110	44	0.4
K cont			2.269	0.032	3.0	110	44	0.4
H2O Ice			3.050	0.152	41	2193	832	0.45
PAH			3.295	0.050	55	2900	1100	0.6
Br alpha cont			3.990	0.060	140	7500	3000	0.6
Br alpha			4.052	0.060	140	7500	3000	0.6