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We present the final band-merged European Large-Area ISO Survey (ELAIS) Catalogue at 6.7, 15, 90 and 175 mum, and the associated data at U, g', r', i', Z, J, H, K and 20 cm. The origin of the survey, infrared and radio observations, data-reduction and optical identifications are briefly reviewed, and a summary of the area covered and the completeness limit for each infrared band is given. A detailed discussion of the band-merging and optical association strategy is given. The total Catalogue consists of 3762 sources. 23 per cent of the 15-mum sources and 75 per cent of the 6.7-mum sources are stars. For extragalactic sources observed in three or more infrared bands, colour-colour diagrams are presented and discussed in terms of the contributing infrared populations. Spectral energy distributions (SEDs) are shown for selected sources and compared with cirrus, M82 and Arp220 starburst, and active galactic nuclei (AGN) dust torus models. Spectroscopic redshifts are tabulated, where available. For the N1 and N2 areas, the Isaac Newton Telescope ugriz Wide Field Survey permits photometric redshifts to be estimated for galaxies and quasars. These agree well with the spectroscopic redshifts, within the uncertainty of the photometric method [similar to10 per cent in (1 + z) for galaxies]. The redshift distribution is given for selected ELAIS bands and colour-redshift diagrams are discussed. There is a high proportion of ultraluminous infrared galaxies (log(10) of 1-1000 mum luminosity L-ir > 12.22) in the ELAIS Catalogue (14 per cent of 15-mum galaxies with known z), many with Arp220-like SEDs. 10 per cent of the 15-mum sources are genuine optically blank fields to r' = 24: these must have very high infrared-to-optical ratios and probably have z > 0.6, so are high-luminosity dusty starbursts or Type 2 AGN. Nine hyperluminous infrared galaxies (L-ir > 13.22) and nine extremely red objects (EROs) (r - K > 6) are found in the survey. The latter are interpreted as u

We present J and K-band near-infrared photometry of a sample of mid-infrared sources detected by the Infrared Space Observatory (ISO) as part of the European Large Area ISO-Survey (ELAIS) and study their classification and star-forming properties. We have used the Preliminary ELAIS Catalogue for the 6.7 micron (LW2) and 15 micron (LW3) fluxes. All of the high-reliability LW2 sources and 80 per cent of the LW3 sources are identified in the near-IR survey reaching K = 17.5 mag. The near- to mid-IR flux ratios can effectively be used to separate stars from galaxies in mid-IR surveys. The stars detected in our survey region are used to derive a new accurate calibration for the ELAIS ISOCAM data in both the LW2 and LW3 filters. We show that near to mid-IR colour-colour diagrams can be used to further classify galaxies, as well as study star-formation. The ISOCAM ELAIS survey is found to mostly detect strongly star-forming late-type galaxies, possibly starburst powered galaxies, and it also picks out obscured AGN. The ELAIS galaxies yield an average mid-IR flux ratio LW2/LW3 = 0.67 +/- 0.27. We discuss this [6.7/15] ratio as a star formation tracer using ISO and IRAS data of a local comparison sample. We find that the [K/15] ratio is also agood indicator of activity level in galaxies and conclude that the drop in the [6.7/15] ratio seen in strongly star-forming galaxies is a result of both an increase of 15 mic emission and an apparent depletion of 6.7 mic emission. Near-IR data together with the mid-IR give the possibility to estimate the relative amount of interstellar matter in the galaxies., Comment: 18 pages, 15 figures; accepted for publication in MNRAS

We present J and K-band near-infrared photometry of a sample of mid-infrared sources detected by the Infrared Space Observatory (ISO) as part of the European Large Area ISO-Survey (ELAIS) and study their classification and star-forming properties. We have used the Preliminary ELAIS Catalogue for the 6.7 micron (LW2) and 15 micron (LW3) fluxes. All of the high-reliability LW2 sources and 80 per cent of the LW3 sources are identified in the near-IR survey reaching K = 17.5 mag. The near- to mid-IR flux ratios can effectively be used to separate stars from galaxies in mid-IR surveys. The stars detected in our survey region are used to derive a new accurate calibration for the ELAIS ISOCAM data in both the LW2 and LW3 filters. We show that near to mid-IR colour-colour diagrams can be used to further classify galaxies, as well as study star-formation. The ISOCAM ELAIS survey is found to mostly detect strongly star-forming late-type galaxies, possibly starburst powered galaxies, and it also picks out obscured AGN. The ELAIS galaxies yield an average mid-IR flux ratio LW2/LW3 = 0.67 +/- 0.27. We discuss this [6.7/15] ratio as a star formation tracer using ISO and IRAS data of a local comparison sample. We find that the [K/15] ratio is also agood indicator of activity level in galaxies and conclude that the drop in the [6.7/15] ratio seen in strongly star-forming galaxies is a result of both an increase of 15 mic emission and an apparent depletion of 6.7 mic emission. Near-IR data together with the mid-IR give the possibility to estimate the relative amount of interstellar matter in the galaxies., Comment: 18 pages, 15 figures; accepted for publication in MNRAS

We present the luminosity function of 90um selected galaxies from the European Large Area ISO Survey (ELAIS), extending to z=0.3. Their luminosities are in the range 10^9 < h_65^-2 L/Lsun < 10^12, i.e. non-ultraluminous. From our sample of 37 reliably detected galaxies in the ELAIS S1 region from the Efstathiou et al. (2000) S_90 >= 100mJy database, we found optical, 15um or 1.4GHz identifications for 24 (65%). We have obtained 2dF and UK Schmidt FLAIR spectroscopy of 89% of IDs to rigid multivariate flux limits. We construct a luminosity function assuming (a) our spectroscopic subset is an unbiased sparse sample, and (b) there are no galaxies which would not be represented in our spectroscopic sample at {\it any} redshift. We argue that we can be confident of both assumptions. We find the luminosity function is well-described by the local 100um luminosity function of Rowan-Robinson, Helou & Walker (1987). {\it Assuming} this local normalisation, we derive luminosity evolution of (1+z)^{2.45\pm0.85} (95% confidence). We argue that star formation dominates the bolometric luminosities of these galaxies and we derive comoving star formation rates in broad agreement with the Flores et al. (1999) and Rowan-Robinson et al. (1997) mid-IR-based estimates., Comment: MNRAS in press. 8 pages. Uses BoxedEPS (included). For more information on the ELAIS project see http://athena.ph.ic.ac.uk:80

We present some recent results from the European Large Area ISO Survey (ELAIS). This survey was the largest non-serendipitous ISO field survey. A preliminary reduction has recently been completed and catalogues of sources released to the community. Early results show strongly evolving source counts. A comprehensive identification programme is underway and a number of extremely luminous objects have already been discovered. This survey provides an exciting legacy from the ISO mission and (amongst many goals) will allow us to provide important constraints on the obscured star-formation history of the Universe., Comment: proceedings of "ISO Surveys of a Dusty Universe", eds. D. Lemke, M. Stickel, K. Wilke, Ringberg, 8-12 Nov 1999, to appear in Springer 'Lecture Notes of Physics'.,8 pages 4 Figures

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., Comment: MNRAS in press. 14 pages, uses BoxedEPS (included). For more information on the ELAIS project see http://athena.ph.ic.ac.uk

We present the luminosity function of 90um selected galaxies from the European Large Area ISO Survey (ELAIS), extending to z=0.3. Their luminosities are in the range 10^9 < h_65^-2 L/Lsun < 10^12, i.e. non-ultraluminous. From our sample of 37 reliably detected galaxies in the ELAIS S1 region from the Efstathiou et al. (2000) S_90 >= 100mJy database, we found optical, 15um or 1.4GHz identifications for 24 (65%). We have obtained 2dF and UK Schmidt FLAIR spectroscopy of 89% of IDs to rigid multivariate flux limits. We construct a luminosity function assuming (a) our spectroscopic subset is an unbiased sparse sample, and (b) there are no galaxies which would not be represented in our spectroscopic sample at {\it any} redshift. We argue that we can be confident of both assumptions. We find the luminosity function is well-described by the local 100um luminosity function of Rowan-Robinson, Helou & Walker (1987). {\it Assuming} this local normalisation, we derive luminosity evolution of (1+z)^{2.45\pm0.85} (95% confidence). We argue that star formation dominates the bolometric luminosities of these galaxies and we derive comoving star formation rates in broad agreement with the Flores et al. (1999) and Rowan-Robinson et al. (1997) mid-IR-based estimates., Comment: MNRAS in press. 8 pages. Uses BoxedEPS (included). For more information on the ELAIS project see http://athena.ph.ic.ac.uk:80

We present some recent results from the European Large Area ISO Survey (ELAIS). This survey was the largest non-serendipitous ISO field survey. A preliminary reduction has recently been completed and catalogues of sources released to the community. Early results show strongly evolving source counts. A comprehensive identification programme is underway and a number of extremely luminous objects have already been discovered. This survey provides an exciting legacy from the ISO mission and (amongst many goals) will allow us to provide important constraints on the obscured star-formation history of the Universe., Comment: proceedings of "ISO Surveys of a Dusty Universe", eds. D. Lemke, M. Stickel, K. Wilke, Ringberg, 8-12 Nov 1999, to appear in Springer 'Lecture Notes of Physics'.,8 pages 4 Figures

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., Comment: MNRAS in press. 14 pages, uses BoxedEPS (included). For more information on the ELAIS project see http://athena.ph.ic.ac.uk

We describe the European Large Area ISO Survey (ELAIS). ELAIS was the largest single Open Time project conducted by ISO, mapping an area of 12 deg2 at 15 μm with ISOCAM and at 90 μm with ISOPHOT. Secondary surveys in other ISO bands were undertaken by the ELAIS team within the fields of the primary survey, with 6 deg2 being covered at 6.7 μm and 1 deg2 at 175 μm. 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 15 μm with a flux limit of ∼3 mJy), 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.

We present the luminosity function of 90-μm-selected galaxies from the European Large Area ISO Survey (ELAIS), extending to z=0.3. Their luminosities are in the range 109

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