We present BAX, Base de Données Amas de Galaxies X (http://bax.ast.obs-mip.fr), a multi-wavelengt... more We present BAX, Base de Données Amas de Galaxies X (http://bax.ast.obs-mip.fr), a multi-wavelength database dedicated to X-ray clusters and groups of galaxies allowing detailed information retrieval. BAX is designed to support astronomical research by providing access to published measurements of the main physical quantities and to the related bibliographic references: basic data stored in the database are cluster/group identifiers, equatorial coordinates, redshift, flux, X-ray luminosity (in the ROSAT band) and temperature, and links to additional linked parameters (in X-rays, such as spatial profile parameters, as well as SZ parameters of the hot gas, lensing measurements, and data at other wavelengths, such as optical and radio). The clusters and groups in BAX can be queried by the basic parameters as well as the linked parameters or combinations of these. We expect BAX to become an important tool for the astronomical community. BAX will optimize various aspects of the scientific analysis of X-ray clusters and groups of galaxies, from proposal planning to data collection, interpretation and publication, from both ground based facilities like MEGACAM (CFHT), VIRMOS (VLT) and space missions like XMM-Newton, Chandra and Planck.
We present analyses of the two-point correlation properties of the ESO Slice Project (ESP) galaxy... more We present analyses of the two-point correlation properties of the ESO Slice Project (ESP) galaxy redshift survey, both in redshift and real space. From the redshift-space correlation function ξ(s) we are able to trace positive clustering out to separations as large as 50 h −1 Mpc, after which ξ(s) smoothly breaks down, crossing the zero value between 60 and 80 h −1 Mpc. This is best seen from the whole magnitude-limited redshift catalogue, using the J 3 minimum-variance weighting estimator. ξ(s) is reasonably well described by a shallow power law with γ ∼ 1.5 between 3 and 50 h −1 Mpc, while on smaller scales (0.2 − 2 h −1 Mpc) it has a shallower slope (γ ∼ 1). This flattening is shown to be mostly due to the redshift-space damping produced by virialized structures, and is less evident when volume-limited samples of the survey are analysed. We examine the full effect of redshift-space distortions by computing the two-dimensional correlation function ξ(r p , π) , from which we project out the real-space ξ(r) below 10 h −1 Mpc. This function is well described by a power-law model (r/r o) −γ , with r o = 4.15 +0.20 −0.21 h −1 Mpc and γ = 1.67 +0.07 −0.09. Comparison to other redshift surveys shows a consistent picture in which galaxy clustering remains positive out to separations of 50 h −1 Mpc or larger, in substantial
Euclid is a European Space Agency medium-class mission selected for launch in 2019 within the Cos... more Euclid is a European Space Agency medium-class mission selected for launch in 2019 within the Cosmic Vision 2015-2025 program. The main goal of Euclid is to understand the origin of the accelerated expansion of the universe. Euclid will explore the expansion history of the universe and the evolution of cosmic structures by measuring shapes and red-shifts of galaxies as well as the distribution of clusters of galaxies over a large fraction of the sky. Although the main driver for Euclid is the nature of dark energy, Euclid science covers a vast range of topics, from cosmology to galaxy evolution to planetary research. In this review we focus on cosmology and fundamental physics, with a strong emphasis on science beyond the current standard models. We discuss five broad topics: dark energy and modified gravity, dark matter, initial conditions, basic assumptions and questions of methodology in the data analysis. This review has been planned and carried out within Euclid's Theory Working Group and is meant to provide a guide to the scientific themes that will underlie the activity of the group during the preparation of the Euclid mission.
We discuss the implications of two possible, recent Sunyaev-Zel'dovich (SZ) detections for which ... more We discuss the implications of two possible, recent Sunyaev-Zel'dovich (SZ) detections for which no optical or X-ray counterparts have been found. This suggests that the objects reside at high redshift, which is difficult to reconcile with a critical cosmology. We develop this argument and find that an open model with Ω o = 0.2 remains consistent with what we currently know about the two objects. The reasoning also demonstrates the utility of SZ cluster searches.
Aims. We investigate the cosmological test based on the evolution of the gas fraction in X-ray ga... more Aims. We investigate the cosmological test based on the evolution of the gas fraction in X-ray galaxy clusters and the stability of the cosmological parameters derived from it. Methods. Using a sample of distant clusters observed by XMM-Newton and Chandra, and comparing their gas fraction at different radii to the gas fraction observed for nearby clusters, we have determined the likelihood functions for Ω m in a flat universe and the confidence contours in the Ω m − Ω Λ plane. Results. Results obtained at the virial radius point to a high matter density Universe, while for inner radii the Ω m parameter obtained tends to decrease, reaching values compatible with the concordance model. The analysis allows us to conclude that this test provides ambiguous results due to the complex structure of the ICM that induces a dependence of the gas fraction on temperature, radius, and redshift, which cannot be accounted for by the self-similar picture expected from pure gravitational heating of the ICM. Conclusions. The use of gas fraction in X-ray clusters to constrain cosmological parameters seems therefore to be compromised until a better understanding of the ICM physics and the ability to obtain observations of better quality up to the virial radius are achieved.
Proceedings of Advancing Astrophysics with the Square Kilometre Array — PoS(AASKA14), 2015
The extremely high sensitivity and resolution of the Square Kilometre Array (SKA) will be useful ... more The extremely high sensitivity and resolution of the Square Kilometre Array (SKA) will be useful for addressing a wide set of themes relevant for cosmology, in synergy with current and future cosmic microwave background (CMB) projects. Many of these themes also have a link with future optical-IR and X-ray observations. We discuss the scientific perspectives for these goals, the instrumental requirements and the observational and data analysis approaches, and identify several topics that are important for cosmology and astrophysics at different cosmic epochs.
Astronomy and Astrophysics Supplement Series, 1998
The ESO Slice Project (ESP) is a galaxy redshift survey extending over about 23 square degrees, i... more The ESO Slice Project (ESP) is a galaxy redshift survey extending over about 23 square degrees, in a region near the South Galactic Pole. The survey is ∼ 85% complete to the limiting magnitude b J = 19.4 and consists of 3342 galaxies with redshift determination. The ESP survey is intermediate between shallow, wide angle samples and very deep, one-dimensional pencil beams; the spanned volume is ∼ 5 10 4 h −3 Mpc 3 at the sensitivity peak (z ∼ 0.1). In this paper we present the description of the observations and of the data reduction, the ESP redshift catalogue and the analysis of the quality of the velocity determinations.
Properties of high redshift clusters are a fundamental source of information for cosmology. It ha... more Properties of high redshift clusters are a fundamental source of information for cosmology. It has been shown by Oukbir and Blanchard (1997) that the combined knowledge of the redshift distribution of X-ray clusters of galaxies and the luminosity-temperature correlation, L X − T X , provides a powerful test of the mean density of the Universe. In this paper, we address the question of the possible evolution of this relation from an observational point of view and its cosmological significance. We introduce a new indicator in order to measure the evolution of the X-ray luminosity-temperature relation with redshift and take advantage of the recent availability of temperature information for a significant number of high and intermediate redshift X-ray clusters of galaxies. From our analysis, we find a slightly positive evolution in the L X − T X relation. This implies a high value of the density parameter of 0.85 ± 0.2. However, because the selection of clusters included in our sample is unknown, this can be considered only as a tentative result. A well-controlled Xray selected survey would provide a more robust answer. XMM will be ideal for such a program.
Europe is one of the major partners building the International Space Station (ISS) and European i... more Europe is one of the major partners building the International Space Station (ISS) and European industry, together with ESA, is responsible for many station components including the Columbus Orbital Facility, the Automated Transport Vehicle, two connecting modules and the European Robotic Arm. Together with this impressive list of contributions there is a strong desire within the ESA Member States to benefit from this investment by utilizing the unique capabilities of the ISS to perform world-class science.
Europe is one of the major partners building the International Space Station (ISS) and European i... more Europe is one of the major partners building the International Space Station (ISS) and European industry, together with ESA, is responsible for many station components including the Columbus Orbital Facility, the Automated Transport Vehicle, two connecting modules and the European Robotic Arm. Together with this impressive list of contributions there is a strong desire within the ESA Member States to benefit from this investment by utilizing the unique capabilities of the ISS to perform world-class science.
We present BAX, Base de Données Amas de Galaxies X (http://bax.ast.obs-mip.fr), a multi-wavelengt... more We present BAX, Base de Données Amas de Galaxies X (http://bax.ast.obs-mip.fr), a multi-wavelength database dedicated to X-ray clusters and groups of galaxies allowing detailed information retrieval. BAX is designed to support astronomical research by providing access to published measurements of the main physical quantities and to the related bibliographic references: basic data stored in the database are cluster/group identifiers, equatorial coordinates, redshift, flux, X-ray luminosity (in the ROSAT band) and temperature, and links to additional linked parameters (in X-rays, such as spatial profile parameters, as well as SZ parameters of the hot gas, lensing measurements, and data at other wavelengths, such as optical and radio). The clusters and groups in BAX can be queried by the basic parameters as well as the linked parameters or combinations of these. We expect BAX to become an important tool for the astronomical community. BAX will optimize various aspects of the scientific analysis of X-ray clusters and groups of galaxies, from proposal planning to data collection, interpretation and publication, from both ground based facilities like MEGACAM (CFHT), VIRMOS (VLT) and space missions like XMM-Newton, Chandra and Planck.
We present analyses of the two-point correlation properties of the ESO Slice Project (ESP) galaxy... more We present analyses of the two-point correlation properties of the ESO Slice Project (ESP) galaxy redshift survey, both in redshift and real space. From the redshift-space correlation function ξ(s) we are able to trace positive clustering out to separations as large as 50 h −1 Mpc, after which ξ(s) smoothly breaks down, crossing the zero value between 60 and 80 h −1 Mpc. This is best seen from the whole magnitude-limited redshift catalogue, using the J 3 minimum-variance weighting estimator. ξ(s) is reasonably well described by a shallow power law with γ ∼ 1.5 between 3 and 50 h −1 Mpc, while on smaller scales (0.2 − 2 h −1 Mpc) it has a shallower slope (γ ∼ 1). This flattening is shown to be mostly due to the redshift-space damping produced by virialized structures, and is less evident when volume-limited samples of the survey are analysed. We examine the full effect of redshift-space distortions by computing the two-dimensional correlation function ξ(r p , π) , from which we project out the real-space ξ(r) below 10 h −1 Mpc. This function is well described by a power-law model (r/r o) −γ , with r o = 4.15 +0.20 −0.21 h −1 Mpc and γ = 1.67 +0.07 −0.09. Comparison to other redshift surveys shows a consistent picture in which galaxy clustering remains positive out to separations of 50 h −1 Mpc or larger, in substantial
Euclid is a European Space Agency medium-class mission selected for launch in 2019 within the Cos... more Euclid is a European Space Agency medium-class mission selected for launch in 2019 within the Cosmic Vision 2015-2025 program. The main goal of Euclid is to understand the origin of the accelerated expansion of the universe. Euclid will explore the expansion history of the universe and the evolution of cosmic structures by measuring shapes and red-shifts of galaxies as well as the distribution of clusters of galaxies over a large fraction of the sky. Although the main driver for Euclid is the nature of dark energy, Euclid science covers a vast range of topics, from cosmology to galaxy evolution to planetary research. In this review we focus on cosmology and fundamental physics, with a strong emphasis on science beyond the current standard models. We discuss five broad topics: dark energy and modified gravity, dark matter, initial conditions, basic assumptions and questions of methodology in the data analysis. This review has been planned and carried out within Euclid's Theory Working Group and is meant to provide a guide to the scientific themes that will underlie the activity of the group during the preparation of the Euclid mission.
We discuss the implications of two possible, recent Sunyaev-Zel'dovich (SZ) detections for which ... more We discuss the implications of two possible, recent Sunyaev-Zel'dovich (SZ) detections for which no optical or X-ray counterparts have been found. This suggests that the objects reside at high redshift, which is difficult to reconcile with a critical cosmology. We develop this argument and find that an open model with Ω o = 0.2 remains consistent with what we currently know about the two objects. The reasoning also demonstrates the utility of SZ cluster searches.
Aims. We investigate the cosmological test based on the evolution of the gas fraction in X-ray ga... more Aims. We investigate the cosmological test based on the evolution of the gas fraction in X-ray galaxy clusters and the stability of the cosmological parameters derived from it. Methods. Using a sample of distant clusters observed by XMM-Newton and Chandra, and comparing their gas fraction at different radii to the gas fraction observed for nearby clusters, we have determined the likelihood functions for Ω m in a flat universe and the confidence contours in the Ω m − Ω Λ plane. Results. Results obtained at the virial radius point to a high matter density Universe, while for inner radii the Ω m parameter obtained tends to decrease, reaching values compatible with the concordance model. The analysis allows us to conclude that this test provides ambiguous results due to the complex structure of the ICM that induces a dependence of the gas fraction on temperature, radius, and redshift, which cannot be accounted for by the self-similar picture expected from pure gravitational heating of the ICM. Conclusions. The use of gas fraction in X-ray clusters to constrain cosmological parameters seems therefore to be compromised until a better understanding of the ICM physics and the ability to obtain observations of better quality up to the virial radius are achieved.
Proceedings of Advancing Astrophysics with the Square Kilometre Array — PoS(AASKA14), 2015
The extremely high sensitivity and resolution of the Square Kilometre Array (SKA) will be useful ... more The extremely high sensitivity and resolution of the Square Kilometre Array (SKA) will be useful for addressing a wide set of themes relevant for cosmology, in synergy with current and future cosmic microwave background (CMB) projects. Many of these themes also have a link with future optical-IR and X-ray observations. We discuss the scientific perspectives for these goals, the instrumental requirements and the observational and data analysis approaches, and identify several topics that are important for cosmology and astrophysics at different cosmic epochs.
Astronomy and Astrophysics Supplement Series, 1998
The ESO Slice Project (ESP) is a galaxy redshift survey extending over about 23 square degrees, i... more The ESO Slice Project (ESP) is a galaxy redshift survey extending over about 23 square degrees, in a region near the South Galactic Pole. The survey is ∼ 85% complete to the limiting magnitude b J = 19.4 and consists of 3342 galaxies with redshift determination. The ESP survey is intermediate between shallow, wide angle samples and very deep, one-dimensional pencil beams; the spanned volume is ∼ 5 10 4 h −3 Mpc 3 at the sensitivity peak (z ∼ 0.1). In this paper we present the description of the observations and of the data reduction, the ESP redshift catalogue and the analysis of the quality of the velocity determinations.
Properties of high redshift clusters are a fundamental source of information for cosmology. It ha... more Properties of high redshift clusters are a fundamental source of information for cosmology. It has been shown by Oukbir and Blanchard (1997) that the combined knowledge of the redshift distribution of X-ray clusters of galaxies and the luminosity-temperature correlation, L X − T X , provides a powerful test of the mean density of the Universe. In this paper, we address the question of the possible evolution of this relation from an observational point of view and its cosmological significance. We introduce a new indicator in order to measure the evolution of the X-ray luminosity-temperature relation with redshift and take advantage of the recent availability of temperature information for a significant number of high and intermediate redshift X-ray clusters of galaxies. From our analysis, we find a slightly positive evolution in the L X − T X relation. This implies a high value of the density parameter of 0.85 ± 0.2. However, because the selection of clusters included in our sample is unknown, this can be considered only as a tentative result. A well-controlled Xray selected survey would provide a more robust answer. XMM will be ideal for such a program.
Europe is one of the major partners building the International Space Station (ISS) and European i... more Europe is one of the major partners building the International Space Station (ISS) and European industry, together with ESA, is responsible for many station components including the Columbus Orbital Facility, the Automated Transport Vehicle, two connecting modules and the European Robotic Arm. Together with this impressive list of contributions there is a strong desire within the ESA Member States to benefit from this investment by utilizing the unique capabilities of the ISS to perform world-class science.
Europe is one of the major partners building the International Space Station (ISS) and European i... more Europe is one of the major partners building the International Space Station (ISS) and European industry, together with ESA, is responsible for many station components including the Columbus Orbital Facility, the Automated Transport Vehicle, two connecting modules and the European Robotic Arm. Together with this impressive list of contributions there is a strong desire within the ESA Member States to benefit from this investment by utilizing the unique capabilities of the ISS to perform world-class science.
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Papers by A. Blanchard