F. Hammer

The Canada-France Redshift Survey: The Luminosity Density and Star Formation History of the Universe to z ~ 1

The comoving luminosity density of the universe, (λ), is estimated from the Canada-France Redshift Survey (CFRS) faint galaxy sample in three wave bands (2800 A, 4400 A, and 1 μm) over the redshift range 0 < z < 1. In all three wave bands, increases markedly with redshift. For a (q0 = 0.5, Ω = 1.0) cosmological model, the comoving luminosity density increases as (1 + z)2.1 ± 0.5 at 1 μm, as (1 + z)2.7 ± 0.5 at 4400 A, and as (1 + z)3.9 ± 0.75 at 2800 A, these exponents being reduced by 0.43 and 1.12 for (0.05, 0.1) and (-0.85, 0.1) cosmological models, respectively. The (λ)-τ relation can be reasonably well modeled by an actively evolving stellar population with a Salpeter initial mass function (IMF) extending to 125 M☉, and a star formation rate declining as τ-2.5 with a turn-on of star formation at early epochs. A Scalo IMF extending to the same mass limit produces too many long-lived low-mass stars. This rapid evolution of the star formation rate and comoving luminosity density of the universe is in good agreement with the conclusions of Pei & Fall from their analysis of the evolving metallicity of the universe. One consequence of this evolution is that the physical luminosity density at short wavelengths has probably declined by 2 orders of magnitude since z ~ 1.

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 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.

Hubble Space Telescope imaging of the CFRS and LDSS redshift surveys - IV. Influence of mergers in the evolution of faint field galaxies from z~1

ABSTRA C T Hubble Space Telescope images of a sample of 285 galaxies with measured redshifts from the Canada‐France Redshift Survey (CFRS) and Autofib‐Low Dispersion Spectrograph Survey (LDSS) redshift surveys are analysed to derive the evolution of the merger fraction out to redshifts z , 1. We have performed visual and machine-based merger identifications, as well as counts of bright pairs of galaxies with magnitude differences dm # 1:5 mag. We find that the pair fraction increases with redshift, with up to ,20 per cent of the galaxies being in physical pairs at z , 0:75‐1. We derive a merger fraction varying with redshift as /O1a zU 3:2^0:6 , after correction for line-of-sight contamination, in excellent agreement with the merger fraction derived from the visual classification of mergers for which ma 3:4 ^ 0:6. After correcting for seeing effects on the ground-based selection of survey galaxies, we conclude that the pair fraction evolves as/O1a zU 2:7^0:6 . This implies that an average L* galaxy will have undergone 0.8‐1.8 merger events from za 1t oza 0, with 0.5 to 1.2 merger events occuring in a 2-Gyr time-span at around z , 0:9. This result is consistent with predictions from semi-analytical models of galaxy formation. From the simple coaddition of the observed luminosities of the galaxies in pairs, physical mergers are computed to lead to a brightening of 0.5 mag for each pair on average, and a boost in star formation rate of a factor of 2, as derived from the average [O ii] equivalent widths. Mergers of galaxies are therefore contributing significantly to the evolution of both the luminosity function and luminosity density of the Universe out to z , 1.

15 Micron Infrared Space Observatory Observations of the 1415+52 Canada-France Redshift Survey Field: The Cosmic Star Formation Rate as Derived from Deep Ultraviolet, Optical, Mid-Infrared, and Radio Photometry

The Canada-France Redshift Survey 1452+52 field has been deeply imaged with the Infrared Space Observatory using ISOCAM through the LW3 filter (12-18 μm). Careful data analysis and comparison with deep optical and radio data have allowed us to generate a catalog of 78 15 μm sources with both radio and optical identifications. They are redder and lie at higher redshift than I-band-selected galaxies, with most of them being star-forming galaxies. We have considered the galaxies detected at radio and 15 μm wavelengths, which potentially include all strong and heavily extincted starbursts, up to z=1. Spectral energy distributions (SEDs) for each of the sources have been derived using deep radio, mid-IR, near-IR, optical, and UV photometry. The sources were then spectrally classified by comparing with SEDs of well-known nearby galaxies. By deriving their far-IR luminosities by interpolation, we can estimate their star formation rate (SFR) in a way that does not depend sensitively on the extinction. Between 35% and 85% of the star formation at z≤1 is related to IR emission, and the global extinction is in the range AV=0.5-0.85. While heavily extincted starbursts with SFRs in excess of 100 M☉ yr-1 constitute less than 1% of all galaxies, they contribute about 18% of the SFR density out to z=1. Their morphologies range from S0 to Sab, and more than a third are interacting systems. The SFR derived by far-IR fluxes is likely to be ~2.9 times higher than those previously estimated from UV fluxes. The derived stellar mass formed since the redshift of 1 could be too high when compared with the present-day stellar mass density. This might be due to an initial mass function in distant star-forming galaxies different from the solar neighborhood one or an underestimate of the local stellar mass density.

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

An extremely primitive star in the Galactic halo

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The Canada-France Redshift Survey. VIII. Evolution of the Clustering of Galaxies from Z approximately 1

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