Showing papers by "Brigitte Rocca-Volmerange published in 2000"
Imperial College London1, International School for Advanced Studies2, University of Edinburgh3, Spanish National Research Council4, Cardiff University5, University of Cantabria6, Max Planck Society7, California Institute of Technology8, University of Padua9, National and Kapodistrian University of Athens10, University of Turku11, Roma Tre University12, Niels Bohr Institute13, Danish Space Research Institute14, University of Helsinki15, Institut d'Astrophysique de Paris16, University of Paris17
TL;DR: The European Large Area ISO Survey (ELAIS) as mentioned in this paper was the largest single Open Time project conducted by ISO, mapping an area of 12deg^2 at 15μm and at 90μm with ISOPHOT.
Abstract: We describe the European Large Area ISO Survey (ELAIS). ELAIS was the largest single Open Time project conducted by ISO, mapping an area of 12deg^2 at 15μm with ISOCAM and at 90μm with ISOPHOT. Secondary surveys in other ISO bands were undertaken by the ELAIS team within the fields of the primary survey, with 6deg^2 being covered at 6.7μm and 1deg^2 at 175μm. This paper discusses the goals of the project and the techniques employed in its construction, as well as presenting details of the observations carried out, the data from which are now in the public domain. We outline the ELAIS `preliminary analysis' which led to the detection of over 1000 sources from the 15 and 90-μm surveys (the majority selected at 15μm with a flux limit of ~3mJy), to be fed into a ground-based follow-up campaign, as well as a programme of photometric observations of detected sources using both ISOCAM and ISOPHOT. We detail how the ELAIS survey complements other ISO surveys in terms of depth and areal coverage, and show that the extensive multi-wavelength coverage of the ELAIS fields resulting from our concerted and on-going follow-up programme has made these regions amongst the best studied areas of their size in the entire sky, and, therefore, natural targets for future surveys. This paper accompanies the release of extremely reliable subsets of the `preliminary analysis' products. Subsequent papers in this series will give further details of our data reduction techniques, reliability and completeness estimates and present the 15- and 90-μm number counts from the `preliminary analysis', while a further series of papers will discuss in detail the results from the ELAIS `final analysis', as well as from the follow-up programme.
196 citations
TL;DR: In this article, the authors present preliminary source counts at 6.7 and 15 μm from the preliminary analysis of the European Large Area ISO Survey, with limiting flux densities of ∼2 mJy at 15 μM and ∼1 mJY at 6.7 μm.
Abstract: We present preliminary source counts at 6.7 and 15 μm from the preliminary analysis of the European Large Area ISO Survey, with limiting flux densities of ∼2 mJy at 15 μm and ∼1 mJy at 6.7 μm. We separate the stellar contribution from the extragalactic using identifications with automated plate measurement sources made with the likelihood ratio technique. We quantify the completeness and reliability of our source extraction using (a) repeated observations over small areas, (b) cross-identifications with stars of known spectral type, (c) detections of the point spread function wings around bright sources and (d) comparison with independent algorithms. Flux calibration at 15 μm was performed using stellar identifications; the calibration does not agree with the pre-flight estimates, probably due to effects of detector hysteresis and photometric aperture correction. The 6.7-μm extragalactic counts are broadly reproduced in the Pearson & Rowan-Robinson model, but the Franceschini et al. model underpredicts the observed source density by ∼0.5–1 dex, although the photometry at 6.7 μm is still preliminary. At 15 μm the extragalactic counts are in excellent agreement with the predictions of the Pearson & Rowan-Robinson, Franceschini et al., Guiderdoni et al. models and the evolving models of Xu et al., over seven orders of magnitude in 15-μm flux density. The counts agree with other estimates from the ISOCAM instrument at overlapping flux densities, provided a consistent flux calibration is used. Luminosity evolution at a rate of (1+z)3, incorporating mid-infrared spectral features, provides a better fit to the 15-μm differential counts than (1+z)4 density evolution. No-evolution models are excluded, implying that below around 10 mJy at 15 μm the source counts become dominated by an evolving cosmological population of dust-shrouded starbursts and/or active galaxies.
99 citations
TL;DR: In this paper, the authors present preliminary source counts at 6.7um and 15um from the Preliminary Analysis of the European Large Area ISO survey, with limiting flux densities of \~2mJy at 15um and ~1m Jy at 6,7um.
Abstract: We present preliminary source counts at 6.7um and 15um from the Preliminary Analysis of the European Large Area ISO survey, with limiting flux densities of \~2mJy at 15um & ~1mJy at 6.7um. We separate the stellar contribution from the extragalactic using identifications with APM sources made with the likelihood ratio technique. We quantify the completeness & reliability of our source extraction using (a) repeated observations over small areas, (b) cross-IDs with stars of known spectral type, (c) detections of the PSF wings around bright sources, (d) comparison with independent algorithms. Flux calibration at 15um was performed using stellar IDs; the calibration does not agree with the pre-flight estimates, probably due to effects of detector hysteresis and photometric aperture correction. The 6.7um extragalactic counts are broadly reproduced in the Pearson & Rowan-Robinson model, but the Franceschini et al. (1997) model underpredicts the observed source density by ~0.5-1 dex, though the photometry at 6.7um is still preliminary. At 15um the extragalactic counts are in excellent agreement with the predictions of the Pearson & Rowan-Robinson (1996), Franceschini et al. (1994), Guiderdoni et al. (1997) and the evolving models of Xu et al. (1998), over 7 orders of magnitude in 15um flux density. The counts agree with other estimates from the ISOCAM instrument at overlapping flux densities (Elbaz et al. 1999), provided a consistent flux calibration is used. Luminosity evolution at a rate of (1+z)^3, incorporating mid-IR spectral features, provides a better fit to the 15um differential counts than (1+z)^4 density evolution. No-evolution models are excluded, and implying that below around 10mJy at 15um the source counts become dominated by an evolving cosmological population of dust-shrouded starbursts and/or active galaxies.
84 citations
TL;DR: In this article, the authors presented results and source counts at 90μm extracted from the preliminary analysis of the European Large Area ISO Survey (ELAIS), which covered about 12deg^2 of the sky in four main areas and was carried out with the ISOPHOT instrument onboard the Infrared Space Observatory (ISO).
Abstract: We present results and source counts at 90μm extracted from the preliminary analysis of the European Large Area ISO Survey (ELAIS). The survey covered about 12deg^2 of the sky in four main areas and was carried out with the ISOPHOT instrument onboard the Infrared Space Observatory (ISO). The survey is at least an order of magnitude deeper than the IRAS 100-μm survey and is expected to provide constraints on the formation and evolution of galaxies. The majority of the detected sources are associated with galaxies on optical images. In some cases the optical associations are interacting pairs or small groups of galaxies, suggesting that the sample may include a significant fraction of luminous infrared galaxies. The source counts extracted from a reliable subset of the detected sources are in agreement with strongly evolving models of the starburst galaxy population.
74 citations
TL;DR: In this paper, the authors presented results and source counts at 90micron extracted from the Preliminary Analysis of the European Large Area ISO Survey (ELAIS) and showed that the majority of the detected sources are associated with galaxies on optical images.
Abstract: We present results and source counts at 90micron extracted from the Preliminary Analysis of the European Large Area ISO Survey (ELAIS). The survey covered about 11.6 square degrees of the sky in four main areas and was carried out with the PHOT instrument onboard the Infrared Space Observatory (ISO). The survey is at least an order of magnitude deeper than the IRAS 100micron survey and is expected to provide constraints on the formation and evolution of galaxies. The majority of the detected sources are associated with galaxies on optical images. In some cases the optical associations are interacting pairs or small groups of galaxies suggesting the sample may include a significant fraction of luminous infrared galaxies. The source counts extracted from a reliable subset of the detected sources are in agreement with strongly evolving models of the starburst galaxy population.
60 citations
TL;DR: The results of near-infrared Very Large Telescope (VLT)-Infrared Spectrometer and Array Camera (ISAAC) spectroscopy of a sample of 12 galaxies at z = 0.4-1.4, drawn from the ISOCAM survey of the Hubble Deep Field South, were reported in this paper.
Abstract: We report the results of near-infrared Very Large Telescope (VLT)-Infrared Spectrometer and Array Camera (ISAAC) spectroscopy of a sample of 12 galaxies at z = 0.4-1.4, drawn from the ISOCAM survey of the Hubble Deep Field South. We find that the rest-frame R-band spectra of the ISOCAM galaxies resemble those of powerful dust-enshrouded starbursts. Hα emission is detected in 11 out of 12 objects down to a flux limit of 7 × 10-17 ergs cm-2 s-1, corresponding to a luminosity limit of 1041 ergs s-1 at z = 0.6 (for an H0 = 50 and Ω = 0.3 cosmology). From the Hα luminosities in these galaxies we derive estimates of the star formation rate (SFR) in the range 2-50 M☉ yr-1 for stellar masses 1-100 M☉. The raw Hα-based SFRs are an order of magnitude or more lower than SFR (far-infrared) estimates based on ISOCAM LW3 fluxes. If the Hα emission is corrected for extinction, the median offset is reduced to a factor of 3. The sample galaxies are part of a new population of optically faint but infrared-luminous active starburst galaxies, which are characterized by an extremely high rate of evolution with redshift up to z ~ 1.5 and are expected to contribute significantly to the cosmic far-infrared extragalactic background.
46 citations
TL;DR: The results of near-infrared VLT-ISAAC spectroscopy of a sample of 12 galaxies at z = 0.4-1.4, drawn from the ISOCAM survey of the Hubble Deep Field South, were reported in this paper.
Abstract: We report the results of near-infrared VLT-ISAAC spectroscopy of a sample of 12 galaxies at z = 0.4-1.4, drawn from the ISOCAM survey of the Hubble Deep Field South. We find that the rest frame R-band spectra of the ISOCAM galaxies resemble those of powerful dust-enshrouded starbursts. Halpha emission is detected in 11 out of 12 objects down to a flux limit of 7x10^(-17) erg/cm^2/s, corresponding to a luminosity limit of 10^41 erg/s at z = 0.6, (for an Ho = 50 and Omega = 0.3 cosmology). From the Halpha luminosities in these galaxies we derive estimates of the star formation rate in the range 2--50 Mo/yr for stellar masses 1--100 Mo. The raw Halpha-based star formation rates are an order of magnitude or more lower than SFR(FIR) estimates based on ISOCAM LW3 fluxes. If the Halpha emission is corrected for extinction the median offset is reduced to a factor of 3. The sample galaxies are part of a new population of optically faint but infrared--luminous active starburst galaxies, which are characterized by an extremely high rate of evolution with redshift up to z~1.5 and expected to contribute significantly to the cosmic far-IR extragalactic background.
45 citations
TL;DR: In this article, the evolution of the star formation activity is followed on a wide range of redshifts (0 2 -3 for cosmological reasons) and their intense star formation rates at high-z give strong constraints on early ionization phases, primeval populations or metal enrichments.
Abstract: Deep galaxy counts are among the best constraints on the cosmic star formation history (SFH) of galaxies. The evolution of the star formation activity is followed on a wide range of redshifts (0 2-3 for cosmological reasons). Their intense star formation rates at high-z give strong constraints on early ionization phases, primeval populations or metal enrichments.(abridged)
24 citations
TL;DR: In this article, the authors considered three classes of galaxies: E/SO (early-type), Sa-Sbc (intermediate-type) and bursting dwarfs (late-type).
Abstract: Deep galaxy counts are among the best constraints on the cosmic star formation history (SFH) of galaxies. Using various tracers, the evolution of the star formation activity may now be followed on a wide range of redshifts (0 ≤ z ≤ 4) covering most of the history of the Universe. Two incompatible interpretations of the observations are currently competing. After applying star formation rate (SFR) conversion factors to the CFRS, Hα or ISO samples, many authors conclude to a strong increase (≃ a factor 10) of the SFR from z = 0 to z = 1. They also find some evidence for a peak at z ≃ 1 and for a rapid decrease at higher redshifts. On the other side, the Hawaii deep surveys favor only a mild increase between z = 0 and 1 (Cowieet et al., 1996, 1999). In this paper, we tackle this problem from the point of view of the modelist of the spectral evolution of galaxies. To understand the reason for these discrepant interpretations, we consider three classes of galaxies: E/SO (‘early-type’); Sa-Sbc (‘intermediate-type’); Se-Sd, irregulars and bursting dwarfs (‘late-type’). We use the new version of our evolutionary synthesis code, Pegase (Floc and Rocca-Volmerange, 2000, in preparation), which takes into account metallicity and dust effects. The main results are: i) Late-type galaxies contribute significantly to the local SFR, especially bursting dwarfs (Fioc and Rocca-Volmerange, 1999). Because of that, the cosmic SFR can not decrease by a factor 10 from z = I to O. This is in agreement with Cowie et al., 1999’s result. ii) The SFR of intermediate-type galaxies has strongly decreased since z = 1. Though the decrease is less than what find Lilly et al., 1996, this suggests that the CFRS and Ha surveys are dominated by such bright early spirals. The limits in surface brightness and magnitudes of the observed samples may be the main reason for this selection. iii) The contribution of early-type galaxies increases rapidly from z = 1 to their redshift of formation (≥ 2-3 for cosmological reasons). Their intense star formation rates at high-z give strong constraints on early ionization phases, primeval populations or metal enrichments.
5 citations