ISSN:0094-243X    

DOI:10.1063/1.49250

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

The cumulative emissions of pregalactic, protogalactic, and evolving galactic systems are expected to be recorded in a cosmic infrared background (CIB). Measurement of such a uniform background in the infrared requires absolute sky brightness measurements from space. The Diffuse Infrared Background Experiment (DIRBE) on the Cosmic Background Explorer (COBE) spacecraft is the first space experiment designed to conduct a systematic search for the CIB from 1.25 to 240 &mgr;m, and theCOBEFar Infrared Absolute Spectrophotometer (FIRAS) provides additional absolutely calibrated all‐sky measurements from 100 &mgr;m to 5 mm wavelengths. With the data from these two experiments in hand, the challenge now becomes discrimination of the bright foreground emissions from interplanetary dust and Galactic sources to reveal the extragalactic background. Conservative limits on the isotropic infrared background are given by the minimum observed sky brightness at each wavelength. Extensive modeling of the foregrounds is under way to isolate or strongly limit the extragalactic infrared component. The current approach to these modeling efforts is described and representative present residuals are reported. Results are compared with those from recent rocket flights and with the extragalactic light estimated from galaxy counts. ©1996 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.49243

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

Obtaining a model of the zodiacal cloud to predict the flux in a given waveband, in a given direction, at a given time of the year, to one per cent of the peak brightness, or better, will require a detailed understanding of the dynamics of the particles that originate from each of the various sources. Each component of the cloud (asteroidal, cometary and interstellar) gives rise to characteristic features and by resolving the cloud into its various components and determining the amplitudes of the signals associated with each, we are able to determine the fractional composition of the cloud. We can expect to have a good understanding of the dynamics of the asteroidal particles that give rise to the solar system dust bands and get trapped in the Earth’s circumsolar resonant ring. Our interpretations of the dust band observations and of the cloud’s trailing/leading asymmetry indicate that about one third of the particles in the cloud are asteroidal, implying that about two thirds of the particles originate from comets. Some progress has been made with understanding the dynamics of cometary particles, but this remains a challenging problem. In this paper, to illustrate the quality of the DIRBE data and to show how the observed structure of the cloud is amenable to a dynamical interpretation, we analyze the asymmetry of the cloud observed in the DIRBE 12 &mgr;m waveband. ©1996 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.49229

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

The Diffuse Infrared Background Experiment (DIRBE) aboard theCosmicBackgroundExplorer(COBE)1mapped the entire sky redundantly in 10 wavebands at 1.25, 2.2, 3.5, 4.9, 12, 25, 60, 100, 140, & 240 &mgr;m. The scattering or thermal emission from interplanetary dust contributes significantly to the sky brightness in all 10 wavebands, dominating most. The sky brightness is modulated in time due to the changing viewing aspect of the DIRBE line of sight through the interplanetary dust cloud. A three‐dimensional semi‐physical model for the distribution, emission, and scattering of interplanetary dust was optimized to match the time‐dependence of the sky brightness as observed by DIRBE. The method and results of this fitting procedure are described, as are the difficulties and some future prospects for disentangling the zodiacal light from other contributions to the diffuse infrared sky brightness. ©1996 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.49209

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

The marked trailing/leading asymmetry of the zodiacal cloud, first detected in the IRAS (Infrared Astronomical Satellite) data by Dermottetal. (1988), has since been confirmed by DIRBE (Reachetal., 1995). Our analysis of the DIRBE data shows that the asymmetry exists in a range of wavebands from 4.5 to 60 &mgr;m as well as at different solar elongations. We proposed (Dermottetal., 1994) that this asymmetry is caused by a trailing cloud of asteroidal dust particles that corotates with the Earth in a circumsolar ring of particles trapped in mean motion resonances. Here, we compare predictions derived from this model with the DIRBE observations and discuss the implications of the results for the sizes of the particles near the Earth, and their origin, and for the overall structure of the zodiacal cloud. ©1996 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.49210

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

The contribution of different solar system objects to the diffuse infrared sky brightness is discussed under the viewpoint whether and to what extent these contributions could mimic or hide true extragalactic background light emission. The objects considered range from interplanetary dust through a possible Kuiper belt population to the Oort cloud of comets. It is mainly uncertainties in the distribution of interplanetary dust which may compromise the detection of extragalactic background light, unnoticed contributions from the Kuiper belt or from interstellar particles streaming through the solar system being the next probable sources of uncertainty. A separation of the extragalactic component seems only possible if accurate sky brightness measurements over a wide range of wavelengths with largely different ratios of local to extragalactic contributions are available. ©1996 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.49211

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

I describe the capabilities of ‘‘SKY’’, the model for the point source sky originally developed by Wainscoatetal. (1992: ApJS, 83, 111) and considerably enhanced by Cohen (1994: AJ, 107, 582; also ApJ, 427, 848), emphasizing those aspects most relevant to interpretation of DIRBE data. SKY predicts cumulative and differential source counts, and integrated surface brightness of the sky due to smeared point sources, in any direction, both for eleven ‘‘hardwired’’ far‐UV, optical, and infrared filters and, in a customized mode, for any filter lying entirely within the 2.0–35.0 &mgr;m range. This enables it to predict specifically for the DIRBE bands. SKY realistically represents the Galaxy using disk, spiral arms, local spurs, Gould’s Belt, molecular ring, bulge, and halo. It also offers a good representation of the mid‐IR extragalactic sky. One can use SKY to generate all‐sky maps of the surface brightness of the Galactic point source foreground. These brightnesses fulfil one of the prerequisite elements for seeking cosmological background radiation from DIRBE. The contributions of the Galactic foreground at the South Ecliptic Pole are compared with DIRBE brightnesses. ©1996 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.49212

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

We useCOBE/DIRBE data from which zodiacal light and Galactic stellar foregrounds have been removed in order to derive an all‐sky view of the Galactic cirrus. The dust is seen in emission from 3.5 to 240 &mgr;m; the scattered contribution at 1.25 and 2.2 &mgr;m is not readily discernible. Similar spatial structure allows the correlation of the dust signal in each DIRBE band with a DIRBE 100 &mgr;m cirrus template. The slopes of these correlations are used to derive an average dust spectrum at high Galactic latitudes. The effectiveness of using this average spectrum to remove the contribution of the dust to the diffuse infrared sky brightness is discussed. We also place the DIRBE‐derived average dust spectrum in context with observations in the submillimeter (fromCOBE/FIRAS) and optical. ©1996 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.49213

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

The DENIS project (Deep Near Infrared Survey of the Southern Sky) will provide, for the first time, deep star counts on a large scale, in theI,J,Ksphotometric bands. A first analysis of star counts in theJandKsbands in various directions of our Galaxy, using preliminary data obtained with DENIS are presented. The counts are compared to the results of currently available models of stellar population synthesis for the Galaxy, in order to derive some constraints on the parameters of these models. ©1996 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.49214

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

A correlation analysis between DIRBE and FIRAS sky maps and the new Leiden‐Dwingeloo H Isurvey enables us to establish the large scale spectral and spatial properties of the far‐infrared dust emission over the high Galactic latitude sky. This work provides the information on the Galactic emission necessary to support the search for the far‐infrared Cosmic Background. ©1996 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.49215

出版商:AIP    

年代:1996

数据来源: AIP