ISO LWS Grating Parallel Mode Photometry Scans of the Galactic Center

F. Vivares & E Caux (CESR Toulouse, France)

The LWS Parallel Observing Mode (in use when an instrument other than LWS is the primary instrument during routine pointed observations), allowed for multiband photometry of the interstellar medium particularly along the galactic ridge. In this observing mode, the LWS grating is fixed, and detectors are read out once per second, producing a spectrum within ten narrow wavebands spaced between 46 microns and 178 microns. The Parallel Observing Mode data throughput is maximized when the primary instrument performs a raster observation, allowing LWS to map a uniformly sampled region of the sky with its ~75 arcsecond beam.

Maps presented here span 2 x 3 degrees, with a sampling pattern determined by the vagaries of the primary instrument target raster points. In the table below, minimum and maximum fluxes within the images are given, which are estimates, due to current uncertainties about the LWS beamsize.

           Center                   Min / Max    
 Det     wavelength  bandwidth       fluxes      
          (micron)    (micron)      (MJy/sr)     
-------------------------------------------------
 SW1        46.1        0.3        100 / 4.4e+04 
 SW2        56.1        0.3        100 / 6.5e+04 
 SW3        66.0        0.3        200 / 8.1e+04 
 SW4        75.6        0.3        300 / 8.1e+04 
 SW5        84.7        0.3        350 / 8.5e+04 
 LW1       102.2        0.6        700 / 8.4e+04 
 LW2       122.0        0.6       1000 / 8.2e+04 
 LW3       141.6        0.6       1100 / 1.1e+05 
 LW4       160.4        0.6       1100 / 1.0e+05 
 LW5       177.8        0.6       1000 / 1.2e+05 
-------------------------------------------------

46um

56um

66um

76um

85um

102um

122um

141um

160um

178um

The parallel mode results for the galactic center region are shown for the 10 LWS detectors.

Credits : ESA/ISO, LWS consortium, CESR : F. Vivares & E Caux