2 Observations

a) CO $J=6 \rightarrow 5$ observations The CO $J=6 \rightarrow 5$ line (691.473 GHz) was observed with the "RxG'' receiver on JCMT (Mauna Kea, Hawaii - USA) in April 1995. Technical details on the performance of this receiver at the JCMT can be found in Harris et al. (1994). The spectral resolution was 0.61 km s^-1 per channel. The JCMT's beam is described by a composite beam containing 55% of the power in a 7'' FWHM Gaussian, and 45% in an 18'' FWHM Gaussian, giving an effective beam equal to 12''. The data has been converted from a $T_{\rm A}^*$ to $T_{\rm R}^*$ scale, applying an efficiency factor $\eta_{\rm fss}=0.27$, which corrects for all instrumental scattering and loss terms. The weather conditions were excellent, with a transmission at zenith of 0.6 at the CO  $J=6 \rightarrow 5$ frequency. We obtained a 5 $\times$ 5 point map spaced by 7'', covering a  $35'' \times 35''$ field centered on RA(1950.0) = 16$^{\rm h}$24 $^{\rm m}07\hbox{$.\!\!^{\rm s}$ }7$, Dec(1950.0) = $-24^{\rm o}30'37''$. The effective integration time on each position was 1 minute, yielding a rms noise level of $T_{\rm R}^*$ = 1.9 K. Additionally, we observed the ¹³CO  $J=6 \rightarrow 5$ line (at 661.067 GHz) towards the central position and towards $\Delta$RA, $\Delta$DEC = -14'', +14'', i.e. at the edge of the ¹²CO map. The effective integration time was 4 min yielding rms noise levels of 1.0 K. The observations were done in the beam switching mode, with the chop throw alternated between +120'' (reference position A) and -120'' (position B) in Azimuth. Contamination by CO  $J=6 \rightarrow 5$ emission in the A or B reference positions was checked by subtracting the spectra obtained with the A and B reference positions respectively. Both the averaged and subtracted spectra are given in Fig. 1.

b) ISO observations EL 29 was observed during Revolution 484 (14th March 1997) with the ISO-LWS. We obtained 15 scans covering the range from 43 $\mu$m to 197 $\mu$m in the low resolution mode ($R\sim$ 200) for a total of 2611 s of integration time. We also obtained other 15 scans toward an off-source position, at RA(2000) 16$^{\rm h}$27$^{\rm m}$09.3$^{\rm s}$ and DEC(2000) $-24^\circ$35'18.1''. The data were reduced using the Off-Line-Processing (OLP) version 10 and the ISO-Spectral-Analysis-Package (ISAP) version 2.1. The spectra were flux calibrated using Uranus (Swinyard et al. 1996) and the absolute accuracy is estimated to be better than 30%. Finally, the LWS beamsize is roughly constant at all wavelengths, namely $\sim$80'' (Swinyard et al. 1998). Note that these observations measure absolute fluxes, i.e. they are not "beam-switched'', as is the case for the JCMT observations reported in the previous paragraph.

We searched for five pure rotational lines of molecular hydrogen by using ISO-SWS: S(1), S(2), S(4), S(5) and S(6). The observations were performed during revolution 267 (August 1996) and 292 (September 1996) in the SW1 and SW6 modes respectively, with a spectral resolution of $\lambda$/ $\Delta \lambda$ equal to 400 and 1500 respectively. The SWS aperture is equal to $20'' \times 27''$ and $14'' \times 27''$ at the S(0) and S(1) transitions respectively, and $14'' \times 20''$ at the other ones. The absolute flux calibration is accurate to 20$\%$. More details on the data reduction are reported in Boogert et al. (2000).