9.5.1.3 IRSKY's Estimates

Since we know the background nebulosity is highly variable near the Trapezium, we would like to also make some background estimates with IRSKY. IRSKY will tell us, among many other things, the mean background over $30^{\prime }\times 30^{\prime }$. (We could change the size of that box, but that is the default output.) IRSKY can be found here:

http://www.ipac.caltech.edu/ipac/services/ibis/irsky.html

It also exists with a batch file interface, called IBIS, should we want to submit a list of targets:

http://www.ipac.caltech.edu/ipac/services/ibis/ibis.html

To log into IRSKY, do this:

ssh irsky.ipac.caltech.edu -l irskyssh

and enter the password ssh!irsky. The program is self-documenting, with many help options as we go along. At the end of the session, we are given the option to have our results sent to us by email. The results of a session looking at the $24$, $70$, and $160 \; \mu {\rm m}$ fluxes is in Appendix G and summarized in Table 9.2. As expected, the $160 \; \mu {\rm m}$ background decreased, but somewhat surprisingly, the $70 \; \mu {\rm m}$ background levels increased. See the next section for more on this.

Table 9.2: ONC MIPS background levels from IRSKY (averaged over $30^{\prime }\times 30^{\prime }$).

wavelength ( $\mu {\rm m}$)	ISM (MJy/sr)
24	241
70	3200
160	2370