Guy Mathez

The ESO-Sculptor faint galaxy redshift survey: The photometric sample

We present the photometric sample of a faint galaxy survey carried out in the southern hemisphere, us- ing CCD imaging at the 3.60 m and NTT-3.5 m telescopes at La Silla (ESO). The survey area is a continuous strip of 0:2 1:53 located at high galactic latitude (b II 83) in the Sculptor constellation. The photometric survey pro- vides total magnitudes in the bandsB,V (Johnson) andR (Cousins) to limiting magnitudes of 24.5, 24.0, 23.5 respec- tively. To these limits, the catalog contains about 9500, 12150, 13000 galaxies in B, V , R bands respectively and is the rst large digital multi-colour photometric catalog at this depth. This photometric survey also provides the entry catalog for a fully-sampled redshift survey of 700 galaxies with R 20:5 (Bellanger et al. 1995a). In this paper, we describe the photometric observations and the steps used in the data reduction. The analysis of objects and the star-galaxy separation with a neural net- work are performed using SExtractor, a new photometric software developed by E. Bertin (1996). By application of SExtractor to simulated frames and comparison of multi- ple measurements, we estimate that the photometric ac- curacy of our catalog is 0:05 m for R 22. Then, we use a method to obtain a homogeneous photometric scale over the whole survey using the overlapping regions of neigh- bouring CCDs. The dierential galaxy number counts in B, V , R are in good agreement with previously published CCD studies and conrm the evidence for signicant evo- lution at faint magnitudes as compared to a standard non evolving model (by factors 3.6, 2.6, 2.1). The galaxy colour distributions B R, B V of our sample show a blueing trend of 0:5 m between 21

Major mergers of haloes, the growth of massive black holes and the evolving luminosity function of quasars

We construct a physically motivated analytical model for the quasar luminosity function, based on the joint star formation and feeding of massive black holes suggested by the observed correlation between the black hole mass and the stellar mass of the hosting spheroids. The parallel growth of massive black holes and host galaxies is assumed to be triggered by major mergers of haloes. The halo major merger rate is computed within the framework of the extended Press-Schechter model. The evolution of black holes on cosmological time-scales is achieved by the integration of the governing set of differential equations, established from a few reasonable assumptions that account for the distinct (Eddington-limited or supply-limited) accretion regimes. Finally, the typical light curves of the reactivated quasars are obtained under the assumption that, in such accretion episodes, the fall of matter on to the black hole is achieved in a self-regulated stationary way. The predicted quasar luminosity function is compared with the luminosity functions of the 2dF quasi-stellar object sample and other, higher-redshift data. We find good agreement in all cases, except for z < 1 where the basic assumption of our model is likely to break down.

Spectroscopy of the gravitational arcs in Cl 2244-02, A370 (arclets A5), and Cl 0024+1654

New spectroscopic data on the blue giant arc in Cl 2244-02, on the arclet A5 in Abell 370, and on the split arc in Cl 0024+1654, are analyzed. A probable redshift z = 2.237 is derived for the source of the Cl 2244-02 arc, making this object one of the most distant field galaxies known today. A star formation rate is estimated from the Lyα intensity and compared to other distant field galaxies. For A5, no prominent emission line is found, but three absorption lines point to a tentative redshift z = 1.306. The spectra of the four parts of the Cl 0024+1654 arc look rather similar, but the absence of any spectral feature allows only the determination of a redshift range: 1< z <2.1

Determination of spatial velocity dispersion profile and stream velocity field in galaxy clusters - Application to Coma

The influence of physical effects (such as stream velocity field, ellipticity of the velocity tensor, temperature gradient) on observed velocity dispersion profiles is reviewed.

Neoclassic Cosmological Tests with QSOs

A new cosmological test has been devised, based on QSO samples. Its sensitivity to the parent cosmology (Ω and Λ) and to the various other parameters has been checked with numerical simulations. In particular it is found that increasing the upper redshift limit is largely as efficient as increasing the sample size.

LUMINOSITY SEGREGATION IN DISTANT GALAXY CLUSTERS

Angular separation-magnitude plots drawn from deep photometry of galaxies in distant clusters show evidence for luminosity segregation which cannot be accounted for by field contamination. This segregation, interpreted in terms of dynamical friction, allows one to determine (M/L)g, the mass-to-light ratio of galaxies from their velocity dispersion. In A370 (z=0.37) more than 30 velocities have been measured by multi-aperture spectroscopy, leading to (M/L)g ~ 70. Values greater than 100 are found in 5 other distant clusters by deriving the velocity dispersion from the richness. The luminosity segregation, observed even inside each of the clumps of 3C299, could result either from dynamical friction inside the clumps or from some early environmental influence.

What does the Dynamical Analsis of Clusters of Galaxies Tell Us about Massive Neutrinos

It is often claimed that massive neutrinos (ν’s) can solve the “missing mass” problem, but it is not so clear in the particular case of clusters of galaxies (C.O.G.). Let us assume that the unseen matter is composed by massive ν’s only. If they are cosmological, the ν’s should obey Fermi-Dirac statistics with a density of ~ 100 ν/cm3/species. But if “relic,” the ν’s would be so slow (1) that they cannot exist in this form (because of the previous Jeans instability or because they are trapped in wells generated by baryonic matter). Since the time when the ν’s decoupled from the primeval mixture (T ~ 3–1 MeV), the ν’s can be considered as a “gravitational plasma,” so that violent relaxation occurs in inhomogeneous systems, leading to a Lynden-Bell distribution defined by three parameters: ην (numerical density), Vν (r.m.s. velocity) and the ν-mass, mν, all unknown. All three of these parameters are, in fact, necessary to define a state of ν-matter.

Multimass Models for Clusters of Galaxies

It is now a widely spread opinion that a ratio of 10:1 between dark and luminous matter exists. Supported by the existence of flat rotation curves at large radii for spirals, this fact reinforces cosmological scenarios with, for instance, massive neutrinos. This content of dark matter is often estimated from the dynamical analysis of clusters of galaxies based essentially on the application of the Virial theorem or the monomassive Emden sphere or deduced from numerical simulations. However, a careful examination shows crucial failures in such approaches, at least the lack of a mass spectrum and/or of a dynamically influent Intra Cluster Medium. This has been included in simple models1 together with other realistic features such as temperature gradient, isovelocity and/or isothermicity of the gravitational plasma. Our aim is thus to account simultaneously for all the available data concerning both galaxies and ICM; namely, the Nonisothermal Multimass Models1 allow us to fit jointly the numerical density profiles of galaxies, the luminosity function, the velocity dispersion profiles versus magnitude or radius, the luminosity segregation2, the X-ray temperature, luminosity and surface brightness profiles.