3,478 research outputs found
DIRBE Minus 2MASS: Confirming the Cosmic Infrared Background at 2.2 Microns
Stellar fluxes from the 2MASS catalog are used to remove the contribution due
to Galactic stars from the intensity measured by DIRBE in four regions in the
North and South Galactic polar caps. After subtracting the interplanetary and
galactic foregrounds, a consistent residual intensity of 14.8 +/- 4.6 kJy/sr or
20.2 +/- 6.3 nW/m^2/sr at 2.2 microns is found. At 1.25 microns the residuals
show more scatter and are a much smaller fraction of the foreground, leading to
a weak limit on the CIRB of 12.0 +/- 6.8 kJy/sr or 28.9 +/- 16.3 nW/m^2/sr (1
sigma).Comment: ApJ in press. 14 pages Latex with 7 included figures. accepted
version with 1 new figur
Using SIRTF to study extragalactic star formation
SIRTF, the Space Infrared Telescope Facility, is a NASA mission to provide a long lifetime, sensitive and flexible infrared observatory in space. SIRTF will be able to study selected objects with a sensitivity over 5,000 time better than the IRAS survey limits, and will provide photometric and low to medium resolution spectroscopic data over almost nine octaves from 1.8 to 700 micron wavelength. The baseline SIRTF design has an 85 cm telescope with optics and control system designed for diffraction limited operation at 4 micron and longer wavelengths. SIRTF will be able to measure important cooling lines from neutral regions, such as the 157 micron line, and lines from H II regions such as the 88 micron line. SIRTF will also be able to survey small areas of the sky to the confusion limit in the 3 to 700 micron region
Diffraction, chopping, and background subtraction for LDR
The Large Deployable Reflector (LDR) will be an extremely sensitive infrared telescope if the noise due to the photons in the large thermal background is the only limiting factor. For observations with a 3 arcsec aperture in a broadband at 100 micrometers, a 20-meter LDR will emit 10(exp 12) per second, while the photon noise limited sensitivity in a deep survey observation will be 3,000 photons per second. Thus the background subtraction has to work at the 1 part per billion level. Very small amounts of scattered or diffracted energy can be significant if they are modulated by the chopper. The results are presented for 1-D and 2-D diffraction calculations for the lightweight, low-cost LDR concept that uses an active chopping quaternary to correct the wavefront errors introduced by the primary. Fourier transforms were used to evaluate the diffraction of 1 mm waves through this system. Unbalanced signals due to dust and thermal gradients were also studied
Angular Power Spectra of the COBE DIRBE Maps
The angular power spectra of the infrared maps obtained by the DIRBE (Diffuse
InfraRed Background Experiment) instrument on the COBE satellite have been
obtained by two methods: the Hauser-Peebles method previously applied to the
DMR maps, and by Fourier transforming portions of the all-sky maps projected
onto a plane. The two methods give consistent results, and the power spectrum
of the high-latitude dust emission is C_\ell \propto \ell^{-3} in the range 2 <
\ell < 300.Comment: ApJ in press. 15 pages with 5 included figure
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