Clustering of the Diffuse Infrared Light from the COBE DIRBE maps. An all-sky survey of C(0)C(0)

We measure the smoothness of the infrared sky using the COBE DIRBE maps, and obtain interesting limits on the production of the diffuse cosmic infrared background (CIB) light by matter clustered like galaxies. The predicted fluctuations of the CIB with the DIRBE beam size of 0.7\deg\ are of the order of 10\%, and the maps are smooth at the level of $\delta\nu I_\nu \sim$ a few \nwm2sr rms from 2.2 to 100 \um. The lowest numbers are achieved at mid- to far-IR where the foreground is bright but smooth; they are $\sqrt{C(0)}$$\leq$$(1-1.5)$ \nwm2sr at $\lambda=$ 10-100 \um. If the CIB comes from clustered matter evolving according to typical scenarios, then the smoothness of the maps implies CIB levels less than $\sim (10-15)$ \nwm2sr over this wavelength range.Comment: 15 pages (LATEX) with 2 figures and 1 plate; Ap. J. Letters, in pres

Clustering of the Diffuse Infrared Light from the COBE DIRBE maps. I. C(0)C(0) and limits on the near-IR background

This paper is devoted to studying the CIB through its correlation properties. We studied the limits on CIB anisotropy in the near IR (1.25, 2.2, and 3.5 \um, or $J,\;K,\;L$) bands at a scale of 0.7\deg\ using the COBE\footnote{ The National Aeronautics and Space Administration/Goddard Space Flight Center (NASA/GSFC) is responsible for the design, development, and operation of the {\it COBE}. Scientific guidance is provided by the {\it COBE} Science Working Group. GSFC is also responsible for the development of the analysis software and for the production of the mission data sets.} Diffuse Infrared Background Experiment (DIRBE) data. In single bands we obtain the upper limits on the zero-lag correlation signal $C(0)= \langle(\nu \delta I_\nu)^2\rangle < 3.6 \times 10^{-16},\; 5.1 \times 10^{-17},\; 5.7 \times 10^{-18}$ \w2m4sr2 for the $J,K,L$ bands respectively. The DIRBE data exhibit a clear color between the various bands with a small dispersion. On the other hand most of the CIB is expected to come from redshifted galaxies and thus should have different color properties. We use this observation to develop a `color subtraction' method of linear combinations of maps at two different bands. This method is expected to suppress the dominant fluctuations from foreground stars and nearby galaxies, while not reducing (or perhaps even amplifying) the extragalactic contribution to $C(0)$. Applying this technique gives significantly lower and more isotropic limits.Comment: 44 pages postcript; includes 5 tables, 14 figures. Astrophysical Journal, in pres

Clustering of DIRBE Light and IR Background

We outline a new method for estimating the cosmic infrared background using the spatial and spectral correlation properties of infrared maps. The cosmic infrared background from galaxies should have a minimum fluctuation of the order of 10\% on angular scales of the order of 1\deg. We show that a linear combination of maps at different wavelengths can greatly reduce the fluctuations produced by foreground stars, while not eliminating the fluctuations of the background from high redshift galaxies. The method is potentially very powerful, especially at wavelengths where the foreground is bright but smooth.Comment: 7 pages postcript, talk at "Unveiling the cosmic infrared background" workshop, College Park, M

Thermal detectors as X-ray spectrometers

Sensitive thermal detectors should be useful for measuring very small energy pulses, such as those produced by the absorption of X-ray photons. The measurement uncertainty can be very small, making the technique promising for high resolution nondispersive X-ray spectroscopy. The limits to the energy resolution of such thermal detectors are derived and used to find the resolution to be expected for a detector suitable for X-ray spectroscopy in the 100 eV to 10,000 eV range. If there is no noise in the thermalization of the X-ray, resolution better than 1 eV full width at half maximum is possible for detectors operating at 0.1 K. Energy loss in the conversion of the photon energy to heat is a potential problem. The loss mechanisms may include emission of photons or electrons, or the trapping of energy in long lived metastable states. Fluctuations in the phonon spectrum could also limit the resolution if phonon relaxation times are very long. Conceptual solutions are given for each of these possible problems

Quantitative evaluation of polymer gel dosimeters by broadband ultrasound attenuation

Ultrasound has been examined previously as an alternative readout method for irradiated polymer gel dosimeters, with authors reporting varying dose response to ultrasound transmission measurements. In this current work we extend previous work to measure the broadband ultrasound attenuation (BUA) response of irradiated PAGAT gel dosimeters, using a novel ultrasound computed tomography system