Olivier Le Fevre

The Canada-France Redshift Survey. VI. Evolution of the Galaxy Luminosity Function to Z approximately 1

The cosmic evolution of the field galaxy population has been studied out to a redshift of z � 1 using a sample of 730 I-band selected galaxies, of which 591 have secure redshifts with median � 0.56. The tri-variate luminosity function �(M,color,z) shows unambiguously that the population evolves and that this evolution is strongly differential with color and, less strongly, with luminosity. The luminosity function of red galaxies shows very little change in either number density or luminosity over the entire redshift range 0 0.5. By 0.5 < z < 0.75 the blue luminosity function appears to have uniformly brightened by approximately 1 magnitude. At higher redshifts, the evolution appears to saturate at the brightest magnitudes but continues at fainter levels leading to a steepening of the luminosity function. A significant excess of galaxies relative to the Loveday et al. (1992) local luminosity function is seen at low redshifts z < 0.2 around MAB(B) � 18 and these galaxies may possibly represent the descendants of the evolving blue population seen at higher redshifts. The changes seen in the luminosity function are also apparent in color-magnitude diagrams constructed at different epochs and in the V/Vmax statistic computed as a function of spectral type. Finally, it is argued that the picture of galaxy evolution presented here is consistent with the very much smaller samples of field galaxies that have been selected in other wavebands, and with the results of studies of galaxies selected on the basis of Mg II 2799 absorption

THE zCOSMOS 10k-BRIGHT SPECTROSCOPIC SAMPLE*

We present spectroscopic redshifts of a large sample of galaxies with I_(AB) < 22.5 in the COSMOS field, measured from spectra of 10,644 objects that have been obtained in the first two years of observations in the zCOSMOS-bright redshift survey. These include a statistically complete subset of 10,109 objects. The average accuracy of individual redshifts is 110 km s^(–1), independent of redshift. The reliability of individual redshifts is described by a Confidence Class that has been empirically calibrated through repeat spectroscopic observations of over 600 galaxies. There is very good agreement between spectroscopic and photometric redshifts for the most secure Confidence Classes. For the less secure Confidence Classes, there is a good correspondence between the fraction of objects with a consistent photometric redshift and the spectroscopic repeatability, suggesting that the photometric redshifts can be used to indicate which of the less secure spectroscopic redshifts are likely right and which are probably wrong, and to give an indication of the nature of objects for which we failed to determine a redshift. Using this approach, we can construct a spectroscopic sample that is 99% reliable and which is 88% complete in the sample as a whole, and 95% complete in the redshift range 0.5 < z < 0.8. The luminosity and mass completeness levels of the zCOSMOS-bright sample of galaxies is also discussed.

The Canada-UK Deep Submillimeter Survey: first submillimeter images, the source counts, and resolution of the background

We present the first results of a deep unbiased submillimeter survey carried out at 450 and 850 μm. We detected 12 sources at 850 μm at greater than the 3 σ level, giving a surface density of sources with S850μm>2.8 mJy of 0.49 ± 0.16 arcmin-2. If replicated over the sky, our sources would generate a background at 850 μm of 9.6 × 10−11 W m-2 sr-1, which is simeq20% of the value measured by the Far-Infrared Absolute Spectrophotometer (FIRAS) and a significant fraction of the total background radiation produced by stars. This implies, through the connection between metallicity and background radiation, that a significant fraction of all the stars that have ever been formed were formed in objects like those detected here. The combination of their large contribution to the background radiation and their extreme bolometric luminosities makes these objects excellent candidates for being proto-elliptical galaxies. Optical astronomers have recently shown that the UV luminosity density of the universe increases by a factor of simeq10 between z=0 and z=1-2 and then decreases again at higher redshifts. Using the results of a parallel submillimeter survey of the local universe, we show that both the submillimeter source density and background radiation (as detected by FIRAS) can be explained if the submillimeter luminosity density evolves in a similar way to the UV luminosity density. Thus, if these sources are elliptical galaxies in the process of formation, they are probably forming at relatively modest redshifts.

The Canada-United Kingdom Deep Submillimeter Survey. II. First Identifications, Redshifts, and Implications for Galaxy Evolution*

Identifications are sought for 12 submillimeter sources detected in a deep submillimeter survey. Six are securely identified, two have probable identifications, and four remain unidentified with IAB > 25. Spectroscopic and estimated photometric redshifts indicate that four of the sources have z 3. The spectral energy distributions of the identifications, as defined by measurements or upper limits to the flux densities at 8000 A, at 15, 450, 850 μm, and at 6 cm, are consistent with the spectral energy distributions of high-extinction starbursts such as Arp 220. The far-IR luminosities of the sources at z > 0.5 are of order 3 × 1012 h-250 L☉, i.e., slightly larger than that of Arp 220. As with local ultraluminous infrared galaxies, the optical luminosities of the identified galaxies are comparable to present-day L*, and the optical morphologies of many of the galaxies show evidence for mergers or highly disruptive interactions. Based on this small sample, the cumulative bolometric luminosity function shows strong evolution to z~1, but weaker or possibly even negative evolution beyond. The redshift dependence of the far-IR luminosity density does not appear, at this early stage, to be inconsistent with that seen in the ultraviolet luminosity density. Although the computation of bolometric luminosities is quite uncertain, the population of very luminous galaxies that is detected in the surveys at z > 1 is already matching, in the far-IR, the bolometric output in the ultraviolet of the whole optically selected population. Assuming that the energy source in the far-IR is massive stars, this suggests that the total luminous output from star formation in the universe will be dominated by the far-IR emission once the lower luminosity sources, below the current far-IR detection threshold, are included. Furthermore, the detected systems have individual star formation rates (exceeding 300 h-250 M☉ yr-1) that are much higher than seen in the ultraviolet-selected samples and that are sufficient to form substantial stellar populations on dynamical timescales of 108 yr. The association with mergerlike morphologies and the obvious presence of dust makes it attractive to identify these systems as forming the metal-rich spheroid population, in which case we would infer that much of this activity has occurred relatively recently, at z~2.

The Canada-France redshift survey. 1. Introduction to the survey, photometric catalogs and surface brightness selection effects

The Canada-France Redshift Survey has been undertaken to provide a large well-defined sample of faint galaxies at high redshift in which the selection criteria match as closely as possible those of samples of nearby galaxies. The survey is designed to have a median redshift of z ~ 0.6 corresponding to a look-back time of half the present age of the Universe for Omega ~ 1. Such a survey can then be used for studying many different aspects of the evolution of galaxies over the interval 0 < z < 1. In this paper we describe the selection of the fields, the multicolor imaging observations and the construction and validation of the photometric catalogs. Particular attention is paid to quantifying the unavoidable selection effects in surface brightness and their impact on the survey is assessed in the context of the properties of known populations of galaxies. The photometric catalogs contain several thousand objects brighter than I_{AB}< 22.5 and are essentially complete for central surface brightnesses as faint as

Photometric redshifts in the SWIRE Survey

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The XMM-LSS survey. Survey design and first results

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Post-starburst galaxies: more than just an interesting curiosity

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The Canada-France Redshift Survey. II. Spectroscopic Program: Data for the 0000-00 and 1000+25 Fields

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