Working Group on Infrared Astronomy
Groupe de Travail pour Astronomie Infrarouge

On Improving IR photometric passbands

A. T. Young¹, E. F. Milone², and C. R. Stagg²

Figures 8 through 25

	Figure 8: The zenith transmission in the 1.03-micrometer window, for the mid-latitude summer atmosphere at 1 km above sea level. Note the reduced transmission, compared to Fig. 4
	Figure 9: The zenith transmission in the J window, for the mid-latitude summer atmosphere at 1 km above sea level. Note the reduced transmission, compared to Fig. 4
	Figure 10a: Optimization curves for the placement of the proposed "z" passband. In this and other optimization plots, results are shown for two Kurucz stellar atmosphere models: T = 3500K, log g = 0 and T = 35000 K, log g = 4. The MODTRAN atmospheric model is for a site at 4.2 km at tropical latitudes, namely Mauna Kea
	Figure 10b: Optimization data for the determination of FWHM of the proposed "z" passband. Here as in several other plots, the data are virtually identical for the 3500K and 35000K sources and so are represented by the same symbols and lines. Results for triangular ("*") and trapezoidal ("+") passbands with the same FWHM and peak wavelength, but for a summer, mid-latitude site at 1 km altitude, are also shown
	Figure 11: Optimization data for the placement and FWHM determination of the proposed "J" passband. Note that the dispersion in with wavelength is minimal at 1.24 m. These results are for a 4.2 km tropical atmosphere but the results for a 1 km atmosphere are quite similar
	Figure 12: The zenith transmission in the H window, for the mid-latitude summer atmosphere at 1 km above sea level
	Figure 13a: Optimization curves for the placement of the proposed "H" passband. The results shown are for a 1 km, mid-latitude summer MODTRAN model, but results for higher altitude, drier sites are nearly identical
	Figure 13b: Optimization data for the FWHM determination of the proposed "H" passband
	Figure 14: The zenith transmission in the K window, for the mid-latitude summer atmosphere at 1 km above sea level
	Figure 15a: Optimization curves for the placement of the proposed "K" passband for the tropical atmosphere at 4.2 km above sea level. The least value occurs for a passband close to 2.2 m according to our simulations. We suggest a peak just to the blue of this minimum, at 2.196 m to minimize thermal atmospheric emission in the bandpass. This passband will give an extinction curve nearly free of the Forbes effect
	Figure 15b: Optimization data for the FWHM determination of the proposed "K" passband. The curve for the 4.2 km MODTRAN model rises more slowly than it does for the lower altitude sites. See the text for a description of how this passband differs from other K' passbands
	Figure 16: The zenith transmission in the L and M windows, for the mid-latitude summer atmosphere at 1 km above sea level. The original Johnson L response, and a typical L' passband, are superimposed on the L window for comparison
	Figure 17a: Optimization curve for the placement of the proposed "L" and "L'" passbands. Results are shown for a 1 km, mid-latitude, summer model. The minimum suggests the advisability of at least two passbands, one near 3.6 and the other near 3.9 m. Our suggested passbands overlap slightly.
	Figure 17b: Optimization data for the FWHM determination of the proposed "L" passband
	Figure 17c: Optimization data for the FWHM determination of the proposed "L' " passband in the cleaner part of the atmospheric window
	Figure 18: The zenith transmission in the L and M windows, for the tropical atmosphere at 4.2 km above sea level. Compare to Fig. 16, which is for 1 km above sea level
	Figure 19a: Optimization curve for the placement of the proposed "M" passband for the tropical atmosphere at 4.2 km above sea level
	Figure 19b: Optimization data for the FWHM determination of the proposed "M" passband. The solid line is the response for a 3500K dwarf, the dashed line that for a 35000K giant. Note the identical results for the trapezoidal filter ("x"), which has the same peak (4.675 m) and FWHM (0.114 m) as the suggested triangular passband but also a flat maximum and slightly narrower base
	Figure 20: The zenith transmission in the N window, for the mid-latitude summer atmosphere at 1 km above sea level. The band centered near 1040 cm^-1 is due to ozone
	Figure 21a: Optimization curves for the placement of the proposed "N" passband. These results shown are for a 1 km mid-latitude site in summer. The curve is for a passband with FWHM = 1.64 m; other data are given for 2.0 ("*") m FWHM
	Figure 21b: Optimization data for the FWHM determination of the proposed "N" passband for several peak wavelength placements. Note that for FWHM values greater than about 1.7 m, the lowest values are achieved for a peak wavelength of about 11.1 m
	Figure 22a: Optimization curve for the placement of a proposed "n" passband. Although the deepest minimum occurs at 9.11 m, rises rapidly at longer wavelengths so that we have suggested a peak wavelength closer to 9.0 m (see Fig. 22b). Results for two terrestrial atmosphere models are shown
	Figure 22b: Optimization data for the FWHM determination of a proposed "n" passband. Results are shown for both 4.2 km, tropical atmosphere and a 1 km, summer, mid-latitude atmosphere models. As in Fig. 22a, the differences for the two stellar sources are negligible. Note the increase in with FWHM beyond the apparent minimum for the passband peaking at 9.11 m ("+")
	Figure 23: The zenith transmission in the NOPQ windows, for the tropical atmosphere at 4.2 km above sea level; Q is the greatly obscured window at the left, near 550 cm^-1. The intense band centered near 667 cm^-1 is due to carbon dioxide. Fig. 20 shows the same region for a 1 km atmosphere model.
	Figure 24a: Optimization curve for the placement of a proposed "Q" passband with FWHM=1.6 m, for a tropical atmosphere at 4.2 km above sea level. Note that the minimum occurs near 18.08 m.
	Figure 24b: Optimization data for the FWHM determination of a proposed "Q" passband for a tropical atmosphere at 4.2 km above sea level. Results for peaks at 17.9 and 18.1 m are shown.
	Figure 25: Various "L" passbands actually in use. Johnson's original L is the long-dashed curve marked "L"; the others are filters used at several observatories.