arXiv subjects

B. Guiderdoni

Publications and source records attributed to B. Guiderdoni.

46 records · Page 3Linked to original sources

arXiv1999

The FIR/submm window on galaxy formation

Our view on the deep universe has been so far biased towards optically bright galaxies. Now, the measurement of the Cosmic Infrared Background in FIRAS and DIRBE residuals, and the observations of FIR/submm sources by the ISOPHOT and SCUBA instruments begin unveiling the ``optically dark side'' of galaxy formation. Though the origin of dust heating is still unsolved, it appears very likely that a large fraction of the FIR/submm emission is due to heavily-extinguished star formation. Consequently, the level of the CIRB implies that about 2/3 of galaxy/star formation in the universe is hidden by dust shrouds. In this review, we introduce a new modeling of galaxy formation and evolution that provides us with specific predictions in FIR/submm wavebands. These predictions are compared with the current status of the observations. Finally, the capabilities of current and forthcoming instruments for all-sky and deep surveys of FIR/submm sources are briefly described.

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arXiv1998

FIRBACK: I. A deep survey at 175 $μ$m with ISO, preliminary results

FIRBACK is a deep survey conducted with the ISOPHOT instrument aboard the Infrared Space Observatory (ISO) at an effective wavelength of 175 $μ$m. We present here results we have obtained on the first field, the so-called Marano1 which covers around 0.25 square degree. We find that the source density for objects with a flux above 200 mJy exceeds the counts expected for sources found in the IRAS deep surveys with a similar flux by about an order of magnitude. Such an excess was expected on the basis of the high far infrared background detected with the FIRAS and DIRBE instruments aboard the Cosmic Background Explorer (COBE). These sources are likely to be redshifted infrared galaxies. The steep number counts indicate strong cosmological evolution in this population. The detected sources account for only 10 % of the cosmic IR background. An extrapolation of the counts down to about 10 mJy would be needeed to account for the whole background at this wavelength.

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arXiv1998

Modelling the optically dark side of high--redshift galaxies

The recent detection of the Cosmic Infrared Background in FIRAS and DIRBE residuals, and the observations of IR/submm sources by the ISOPHOT and SCUBA instruments have shed new light on the optically dark side of galaxy formation. It turns out that our view on the deep universe has been so far biassed towards optically bright galaxies. We now know that a significant fraction of galaxy/star formation in the universe is hidden by dust shrouds. In this paper, we introduce a new modelling of galaxy formation and evolution that provides us with specific predictions in the IR/submm wavebands. These predictions are compared with the current status of the observations. Finally, the future all-sky and deep surveys with the PLANCK and FIRST missions are briefly described.

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arXiv1998

The FIRBACK 175 micron Survey

The FIRBACK project is a collaboration of eight institutes aimed at using long wavelength surveys with ISO to uncover the nature of the Cosmic Far-Infrared Background. We have surveyed nearly 4 sq. deg. in three regions in the northern and southern hemispheres with the ISOPHOT instrument on ISO, using the 175 micron filter. As reported by Puget et al. (1998) and Reach et al. (these proceedings), the first 0.25 sq. deg. region studied in this programme contains many more 175 micron sources than expected. Initial reduction of the remaining survey areas appears to confirm this result. The area surveyed by FIRBACK represents the largest and deepest long wavelength far-IR survey available before the launch of SIRTF.

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arXiv1998

Modelling High-z Galaxies from the far-UV to the far-IR

In this paper, we report on a first estimate of the contribution of galaxies to the diffuse extragalactic background from the far-UV to the submm, based on semi--analytic models of galaxy formation and evolution. We conclude that the global multi--wavelength picture seems to be consistent provided a quite important fraction of star--formation be hidden in dust--enshrouded systems at intermediate and high--redshift. We show that, according to such models, galaxies cannot stand as important contributors to the background hydrogen-ionizing flux at high-redshift unless neutral hydrogen absorption sites are clumpy and uncorrelated with star forming regions.We briefly discuss the robustness of such a result.

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arXiv1998

Cosmic Star Formation and Type Ia/II Supernova Rates at high z

We study how Type Ia/II supernova rates at various redshifts can be used to constrain the cosmic star formation rate (CSFR) history. We use a spectrophotometric model of galaxy evolution which provides a self-consistent description of global properties of local galaxies. We have chosen two CSFR histories, with and without dust extinction, both normalized in order to reproduce the observed comoving luminosity densities at different wavelengths. We show that as expected, the SNII rates provide a direct measurement of the instantaneous CSFR, whereas the SNIa rate depends on the CSFR history during the past few Gyrs. Therefore the SNIa rate detected up to $z {\sim}$ 1 is able to provide new insight on the CSFR at higher redshift. The comparison with the data are in good agreement with both local and high-$z$ measurement and provides an additional evidence of the validity of the CSFR up to $z$ = 1, but suggests values at $z >$ 1 higher than those of Madau et al. (1996) and consistent with the presence of extinction. We also show that Type Ia supernova observations at $z{\sim}$ 1 can already put constraints on the still puzzling nature of Type Ia progenitors.

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arXiv1997

What are the galaxies contributing to the Cosmic Infrared Background ?

Recent optical observations have led to a significant progress in our understanding of galaxy formation and evolution. However, our view on the deep universe is currently limited to the starlight which directly escapes from high-redshift galaxies, since we so far ignore the fraction of luminosity absorbed by dust and released in the IR/submm wavelength range. A new constraint is set by the possible detection of the Cosmic Infrared Background. We briefly review the observations and use a semi-analytic model of galaxy formation and evolution to predict number counts consistent with the level of the background. It turns out that the predictions fairly accomodate preliminary data at 175 and 850 microns. This suggests that a significant fraction of star/galaxy formation at high z is hidden by dust.

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arXiv1997

The optically-dark side of galaxy formation

In this letter, we estimate how much starlight was absorbed by dust and released in the infrared during the formation of galaxies. New constraints are set on this so-far hidden history by the recent detection of the Cosmic Infrared Background (CIB) built up from the accumulated light of faint sources (and revisited here). By means of a semi-analytical model of hierarchical galaxy formation, we estimate the population of dust-enshrouded starburst galaxies fitting the CIB. It is argued that a deep ISO survey at 175 micron could already detect these sources and help close the gap in our understanding of the history of light in the Universe.

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arXiv1997

Semi-analytic modelling of galaxy evolution in the IR/submm range

This paper proposes a new semi-analytic modelling of galaxy properties in the IR/submm wavelength range, which is explicitly set in a cosmological framework. This type of approach has had some success in reproducing the optical properties of galaxies. We hereafter propose a simple extension to the IR/submm range. We estimate the IR/submm luminosities of ``luminous UV/IR galaxies'', and we explore how much star formation could be hidden in heavily--extinguished, ``ultraluminous IR galaxies'' by designing a family of evolutionary scenarios which are consistent with the current status of the ``cosmic constraints'', as well as with the IRAS luminosity function and faint counts, but with different high-z IR luminosity densities. However, these scenarios generate a Cosmic Infrared Background whose spectrum falls within the range of the isotropic IR component detected by Puget et al. (1996) and revisited by Guiderdoni et al. (1997). We give predictions for the faint galaxy counts and redshift distributions at IR and submm wavelengths. The submm range is very sensitive to the details of the evolutionary scenarios. As a result, the on-going and forthcoming observations with ISO and SCUBA (and later with SIRTF, SOFIA, FIRST and PLANCK) will put strong constraints on the evolution of galaxies at z=1 and beyond.

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arXiv1997

The contribution of galaxies to the IR background

A new semi-analytic modelling of galaxy evolution in the IR/submm is hereafter outlined. This type of approach successfully reproduces the optical properties of galaxies. We illustrate a simple extension to the IR/submm wavelength range by taking the case of the SCDM model. We design a family of evolutionary scenarios with star formation histories reproducing the evolution of the overall gas and luminosity densities in the universe. These scenarios are also consistent with IRAS data and preliminary ISO counts, and we use them to disentangle the ``Cosmic Infared Background'' detected by Puget et al. (1996) into discrete sources. We finally give predictions for the faint galaxy counts and redshift distributions in various submm wavelengths, which seem to be very sensitive to the details of the evolutionary scenarios. As a consequence, it is easy to anticipate that the current and forthcoming instruments, such as SCUBA, FIRST and PLANCK, will strongly constrain the evolution of high-redshift galaxies.

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