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The cosmic submillimeter background as a possible signature of the initial burst of galaxy formation

Djorgovski, S. and Weir, Nicholas (1990) The cosmic submillimeter background as a possible signature of the initial burst of galaxy formation. Astrophysical Journal, 351 . pp. 343-355. ISSN 0004-637X.

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We propose a heuristic model for the origin of the cosmic submillimeter background (SMB), reported by the Nagoya-Berkeley collaboration. The SMB is interpreted as a direct signature of an epoch of (initial) galaxy formation at z ~ 10-15. The sources of the SMB are proposed to be dust-shrouded starburst protogalaxies, similar to the luminous IRAS galaxies at low redshifts. We interpret them as the progenitors of old stellar populations at low redshifts, ellipticals, bulges, and stellar components of the halos. The derived redshift of the galaxy formation is directly dependent on the dust temperatures assumed for these objects. The corresponding look-back times are -11.5h_(75)^(-1) Gyr for Ω_0 = 0.1, or ~ 8.5h_(75)^(-1) Gyr for Ω_0 = 1. The star formation history in an element of comoving volume was assumed to be a Gaussian in the rest frame, but this form is not critical for the models. Model spectra of the SMB were computed for the values of cosmological density parameter Ω_0 = 0.1 and 1, and the dust emissivity index n = 1 and 2. The largest allowed time scales for the star formation in these models (expressed as the FWHM of the luminosity history) are in the range FWHM ~ 0.2-0.6 Gyr for the low-density models (Ω_0 = 0.1); for the high-density models (Ω_0 = 1), the allowed widths are about a factor of 2 lower. These widths are comparable to, or slightly larger than, the free-fall times for normal galaxies. In order not to overproduce the baryonic mass density, it is necessary that the initial mass function (IMF) in these starbursts is biased toward high-mass stars; however, a substantial range in the IMF parameters is allowed. This postulated population of protogalaxies may be an important contributor to the diffuse soft X-ray background. Leaked (unobscured) starlight from these objects may give rise to a near-infrared background, at about the level detected by Matsumoto, Akiba, and Murakami. The predicted surface density of protogalaxies would be in the range ~10-100 arcsec^(-2), which is consistent with all relevant anisotropy measurements available at this time. The model also predicts that a considerable fraction of the mass density in the bulge and halo of our Galaxy would be provided by old white dwarfs, which may be detectable in deep surveys (a similar prediction was already made by Silk). Spectroscopic signatures of this population may be detectable with future space missions, e.g., with SIRTF or LDR, and possibly also from the ground in the near-infrared and millimeter/submillimeter regions.

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Djorgovski, S.0000-0002-0603-3087
Additional Information:© 1990 American Astronomical Society. Provided by the NASA Astrophysics Data System. Received 1989 May 17; accepted 1989 September 11. We are indebted to many colleagues for stimulating and informative discussions, and in particular to Andrew Lange and Joseph Silk. We thank Nick Scoville and the referee for useful comments on the manuscript. S. D. acknowledges the stimulating atmosphere of the Aspen Center for Physics, and the workshop organized by Jim Truran, which motivated this study. This work was supported in part by the Alfred P. Sloan Foundation and California Institute of Technology (S. D.), and a National Science Foundation fellowship (N. W.). The motivation for this work was in part to prepare a scientific rationale for the proposed NASA Submillimeter Explorer mission. The publication of this paper was supported in part by the funds from NASA.
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Alfred P. Sloan FoundationUNSPECIFIED
Subject Keywords:cosmic background radiation - cosmology - early universe - galaxies: formation - radiation mechanisms
Record Number:CaltechAUTHORS:20190819-160929683
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:98012
Deposited By: Tony Diaz
Deposited On:19 Aug 2019 23:24
Last Modified:03 Oct 2019 21:37

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