Cosmic infrared

Finally, one of the instruments on COBE detected the presence of a cosmic infrared background (CIB), a remnant of the period during which the first stars began to form, many millions of years after the big bang itself. COBE was only one, albeit the best-known, of several research programs designed to study the CMB. In 1998, for example, two other research teams made use of balloons released into the stratosphere to study the cosmic microwave background. These... 

Fig. 1.1 Schematic Spectral Eneigy Distributions (SED) of the most important (by intensity) backgrounds in the Universe, and their approximate brightness in nW m sr written in the boxes. Erom right to left the Cosmic Microwave Background (CMB), the Cosmic Infrared Background (CIB) tmd the Cosmic Optical Background (COB) [Credit Dole et al. A A, 451(2), 417-429,2006, reproduced with permission ESO]...

RE. Dewdney, P.J. HaU, R.T. Schilizzi, T.J.L.W. Lazio, The square kilometre array. Proc. IEEE 97(8), 1482-1496 (2009). ISSN 0018-9219. doi 10.1109/JPROC.2009.2021005 H. Dole, G. Lagache, J.-L. Puget, K.I. Caputi, N. Femandez-Conde, E. Le Floc h, C. Papovich, P.G. P6rez-Gonzalez, G.H. Rieke, M. Blaylock, The cosmic infrared background resolved by Spitzer. Astron. Astrophys. 451(2), 417-429 (2006). doi 10.1051/0004-6361 20054446 ESA Concurrent Design Facility. Far Infrared Interferometer—CDF Study Report. CDF-49(A) 1-294, (2006). http //sci.esa.int/future-missions-office/40738-firi-cdf-study-report/... 

At the Detector Noise Moduie, the Noise Equivalent Power (NEP) associated to the detectors and the 1 // noise are calculated. In parallel, with the physical properties of the system defined, the Background Power Module calculates the background power noise due to the instmment and the Cosmic Microwave Background (CMB), Cosmic Infrared Background (CIB) and Zodiacal Light. 

Electromagnetic radiation (Section 13.1) Various forms of radiation propagated at the speed of light. Electromagnetic radiation includes (among others) visible light infrared, ultraviolet, and microwave radiation and radio waves, cosmic rays, and X-rays. 

On the last three decades, several space experiments with parts at very low temperatures have been flown. Among these, we mention IRAS (Infrared Astronomical Satellite) launched in 1983 (see Fig. 14.1), COBE (Cosmic Background Explorer) launched in 1989, ISO (Infrared Space Observatory) launched in 1995 and Astro-E (X-ray Observatory), launched in 2000 with instrumentation at 65 mK [35], Some cryogenic space missions are in the preparation or in final phase in Europe, USA and Japan. For example, ESA is going to fly Planck (for the mapping of the cosmic background radiation) and Herschel (called before FIRST Far Infrared and Submillimetre Telescope ) [36], These missions will carry experiments at 0.1 and 0.3 K respectively. 

The measurement of the cosmic microwave background. Far infrared astronomers were the first to develop thermal detectors. Some of the resulting technologies, such as neutron transmutation doping (NTD) [3], have been transferred to particle detection sensors and have allowed many groups (e.g., ref. [4-11] to make rapid progress). 

We shall now describe an infrared bolometer operating at 0.3 K, built by Lange et al. in 1992 [80], We chose this example because such composite bolometer can be easily described from a cryogenic point of view, whereas the analysis of more recent devices would be quite complicated. Nevertheless the bolometer performances are very good, the NEP being less than 10-16 W/(Hz)1/2 and the time constant r = 11ms. It was used for the measurement of the cosmic microwave background (CMB) in an experiment on board of a stratospheric balloon [81]. 

Fig. 12.6. Observable baryons in the Universe as a function of time. The curves represent the total mass density in stars (in Af0Mpc-3) from Rudnick et al. (2003) based on a survey of near-infrared selected galaxies in the Hubble Deep Field South, assuming a Salpeter(O.l) IMF. (For a Kennicutt (1983) IMF, the numbers would be approximately halved.) The points with error bars show the cosmic density of H I from DLAs and sub-DLAs at various redshifts, uncorrected for obscuration, while the point at bottom right shows the present-day density of H i clouds determined by Zwaan et al. (2005). The typical H I co-moving volume density corresponds to S2Hi — 0.7 x 10-3 (taking h = 0.65). After Peroux, Dessauges-Zavatsky, D Odorico et al. (2005).

The infrared and ultraviolet radiations are not visible to the eye and so they are know as invisible radiations. The energy of white light is least while the energy of cosmic rays is very large. 

So we have discovered that certain scenes of the cosmic show occur in the invisible. The most disturbing is perhaps this flux of chilled photons carrying over from the Big Bang, which comes to us invisible and inoffensive from the very depths of time. Cool astronomies have blossomed in the quest for red, and beyond it, infrared and millimetric radiation, whilst at the other extreme, beyond the violet, new forms of heat have been revealed to us, if indeed the notion of temperature still has meaning beyond a certain limit. 

In terms of what is measured or observed, there are (1) portions of the electromagnetic spectrum gamma-ray, cosmic ray, x-ray, ultraviolet, infrared, far-infrared, microwave, and radiowave instruments (2) regions pertaining to the energies of particles beta ray (electrons), protons, neutrons, and mass associated instruments and (3) instruments dealing with other spectra such as radioactive decay and Mossbauer effects. 

The most accurate measurements of the CMB spectrum to date have come from the Far InfraRed Absolute Spectrophotometer (FIRAS) on the COsmic Background Explorer (COBE) (Boggess et al., 1992). In contradiction to its name, FIRAS was a fully differential spectrograph that only measured the difference between the sky and an internal reference source that was very nearly a blackbody. Figure 9.2 shows the interferograms observed by FIRAS for the sky and for the external calibrator (XC) at three different temperatures, all taken with the internal calibrator (IC) at 2.759 K. Data from the entire FIRAS dataset show that the rms deviation from a blackbody is only 50 parts per million of the peak Iv of the blackbody (Fixsen et al., 1996) and a recalibration of the thermometers on the external calibrator yield a blackbody temperature of... 

Various Types of Electromagnetic Radiations The various types of electromagnetic radiations are radiowaves, microwaves, infrared waves, ultraviolet waves, visible light, X-rays, g-rays, cosmic rays, etc. 

The interstellar medium is the medium that fills the space between the stars. This space is far from empty. It includes magnetic fields, gas composed of atoms and ions at several different temperatures and densities, cosmic rays, and dust particles. The material content of the ISM changes with time owing to the formation of new stars from it and the ejection of matter from stars into it. The latter include the new nuclei thathave just been assembled by nucleosynthesis in the stars. The state of this medium is turbulent, driven by the shock waves from exploding supernovae. Dust comprises about one percent of the mass of the interstellar matter. It is measured by its infrared radiation and by its obscuration and reddening of starlight. 

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