The WISE relative system response curves (RSRs) were created from the end-to-end lab measurements by modifying the prediction and design values at each wavelength by fitting a line in log-log space and using this to replace any originally negative values. Following the prescription of Bessell (2000), we convert the QE-based Wright et al. (2010) RSRs (Fig. 4) from electrons per photon to photon-counting response curves by multiplying by lambda and renormalizing each to a peak of unity; see Fig. 4b. Both W1 and W2 passbands have close correspondence with those of IRAC-1 and IRAC-2, although the W1 passband is slightly `blue' compared to IRAC-1 and W2 is slightly `red' compared to IRAC-2. The reddest channel of WISE, W4 at 22 µm, compares well with MIPS-24, although it is slightly bluer in response. Compared to Spitzer imaging, the only unique band of WISE is that of W3 (12 µm) which has only small overlap with that of IRAC-4 (8 µm), but is comparable to the IRAS 12 µm channel. One consequence of this band-to-band difference is demonstrated in Fig. 4c, the spectrum of ultra-luminous infrared galaxy Arp 220 has strong polycyclic aromatic hydrocarbon (PAH) emission bands, notably at 11.3 µm compared to the bands at 6.2 and 7.7 µm. WISE W3 compared to IRAC-4 will be more sensitive to both PAH emission and amorphous silicate absorption (10 µm) in nearby star-forming galaxies. Moreover, because W3 is a longer wavelength channel than IRAC-4, it is more sensitive to higher redshift galaxies in which strong near-IR continuum and mid-IR emission features redshift into the band.


The photon-counting RSRs in ASCII table format are available for W1, W2, W3, and W4, which include wavelength in microns, the response, and the uncertainty in the response in parts per thousand (from Jarrett et al. 2011).

http://wise2.ipac.caltech.edu/docs/release/prelim/expsup/sec4_3g.html#WISEZMA

downloaded 2/7/2012