First Look Survey (FLS): Community Workshop Report

The FLS Within-the-Milky-Way component:
B. Observational Definition and Description of Surveys

1. A "strip" one footprint (5 arcmin) wide at l=285 deg, -30 deg<=b<=0 deg. This should give a broad range of cirrus intensities and source counts at a longitude close to the inner galaxy. This zone is viewable by SIRTF for many months and so is fairly robust against deviations from launch date. Within this strip, we consider the range -10<=b<=0 to be most important to cover continuously, since it is closest to the plane and can be compared with another strip described in (b) below. The range -30<=b<=-10 could be covered with a lower filling factor, such as 50%. The coverage and integration times are the same as used for the extragalactic shallow survey, again with the assumption that IRAC and MIPS cover the same area. We consider this an important aspect of galactic FLS observations, since IRAC will be much more sensitive than currently available data at IRAC wavelengths. We estimate 6.7 hours for MIPS and 8.5 hours for IRAC to cover a filled strip 5 arcmin wide and 20 deg long.

2. A second strip similar to (a) above, but at a significantly different longitude, l=150 deg, and extending over the latitude range 0deg<=b<=10deg. Strips over this latitude range are viewable for nearly as long as is (a) provided one can shift the longitude slightly. For the same scanning procedure as in (a) and a fully sampled 10 degree strip, we estimate 3.33 hours for MIPS and 4.25h for IRAC.

   To characterize internal cirrus and background source counts toward a molecular cloud, the workshop suggested a 2 degree long scan through the Chamaeleon II cloud centered at RA(1950)=12h 50m and Dec(1950)=-77 deg. This should provide approximately equal scan length "off" and "on" the cloud. The cloud was chosen because it has a significant population of embedded T Tauri stars, with substantial cirrus emission, and because its position is fairly robust against launch date variations. It appears from information available at the workshop that this choice probably will not conflict with GTO observations. The same MIPS fast scan as assumed in the galactic scans above, and the same area coverage by IRAC as by MIPS are appropriate, but it is recommended to increase the IRAC integration time by a factor of ten over that assumed above. This increase is necessary because many observers will attempt to detect brown dwarfs with IRAC in clouds such as Chamaeleon II, and it will be useful to learn how limiting the cirrus is at the sensitivity needed to detect brown dwarfs. Accordingly the total time needed for this portion is estimated at 40 minutes for MIPS and 8.3 hours for IRAC.

   To characterize the ecliptic plane and zodiacal light for solar system observations, scans are suggested at ecliptic latitudes 0 deg and 15 deg. Each scan would be 5 deg long, with 3 passes by IRAC, each separated from the next by a few hours. This time interval should be enough to allow the 8 micron channel of IRAC to detect moving objects. Each scan would also have 1 pass by MIPS to get the spectral energy distribution of the objects detected by IRAC. For these observations the estimate is 3.3 hours for MIPS and 12.0 hours for IRAC.

   Although we do not suggest any specific spectroscopic observations with IRS as part of the FLS, we note that it would be very useful to observers to have "template spectra" of various objects, perhaps as part of the IOC campaign. We suggest that these include objects for which the background or instrument sensitivity may be limiting factors, such as a spectrum of a source in a region of high cirrus background, e.g. 200 MJy/sr at 100 microns, and a spectrum with R ~ 600 of a source at the limit of the IRS sensitivity.

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