Abstract: We present an integral field spectroscopy survey of rich clusters of galaxies aimed at ... more Abstract: We present an integral field spectroscopy survey of rich clusters of galaxies aimed at studying their lensing properties. Thanks to knowledge of the spectroscopic caracteristics of more than three families of multiple images in a single lens, one is able in principle to derive constraints on the geometric cosmological parameters. We show that this ambitious program is feasible and present some new results, in particular the redshift measurement of the giant arc in A2667 and the resdshift confirmation of the counter-image of the radial arc ...
N-body + hydrodynamical simulations of formation and evolution of galaxy groups in a ΛCDM cosmolo... more N-body + hydrodynamical simulations of formation and evolution of galaxy groups in a ΛCDM cosmology have been performed. The properties of the galaxy populations in 12 groups are here discussed, with focus on the colour-magnitude relation in both normal and fossil groups.
Abstract This is a report of Chandra, XMM-Newton, HST, and ARC observations of an extended X-ray ... more Abstract This is a report of Chandra, XMM-Newton, HST, and ARC observations of an extended X-ray source at z= 0.33. The apparent member galaxies range from spiral to elliptical and are relatively red (i'-Ks about 3). We interpret this object to be a young fossil group which has somehow managed to suppress the star formation rate of the resident galaxies. This complex system sheds new light on the origin and evolution of galaxies in fossil groups and the relationship of fossil groups to poor clusters. The system also ...
The only way to detect planets around stars at distances several kpc is by (photometric or astrom... more The only way to detect planets around stars at distances several kpc is by (photometric or astrometric) microlensing (µL) observations. In this paper, we show that the capability of photometric µL extends to the detection of signals caused by planets around stars in nearby galaxies (e.g. M31) and that there is no other method that can achieve this. Due to the large crowding, µL experiments towards M31 can only observe the high-magnification part of a lensing light curve. Therefore, the dominating channel for µL signals by planets is in distortions near the peak of high-magnification events as discussed by ). We calculate the probability to detect planetary anomalies for µL experiments towards M31 and find that jupiter-like planets around stars in M31 can be detected. Though the characterization of the planet(s) involved in this signal will be difficult, the absence of such signals can yield strong constraints on the abundance of jupiter-like planets.
... This is consistent with recent VLA observations showing that HI is detected in galaxies locat... more ... This is consistent with recent VLA observations showing that HI is detected in galaxies located in the east half of the cluster but not in the west half, therefore suggesting that their HI content has been stripped by a merger coming from the west (Bravo-Alfaro et al. in preparation). ...
Monthly Notices of the Royal Astronomical Society, 2014
We investigate the evolution of dark and luminous matter in the central regions of early-type gal... more We investigate the evolution of dark and luminous matter in the central regions of early-type galaxies (ETGs) up to z ∼ 0.8. We use a spectroscopically selected sample of 154 cluster and field galaxies from the EDisCS survey, covering a wide range in redshifts (z ∼ 0.4-0.8), stellar masses (log M ⋆ /M ⊙ ∼ 10.5-11.5 dex) and velocity dispersions (σ ⋆ ∼ 100-300 km/s). We obtain central dark matter (DM) fractions by determining the dynamical masses from Jeans modelling of galaxy aperture velocity dispersions and the M ⋆ from galaxy colours, and compare the results with local samples. We discuss how the correlations of central DM with galaxy size (i.e. the effective radius, R e ), M ⋆ and σ ⋆ evolve as a function of redshift, finding clear indications that local galaxies are, on average, more DM dominated than their counterparts at larger redshift. This DM fraction evolution with z can be only partially interpreted as a consequence of the size-redshift evolution. We discuss our results within galaxy formation scenarios, and conclude that the growth in size and DM content which we measure within the last 7 Gyr is incompatible with passive evolution, while it is well reproduced in the multiple minor merger scenario. We also discuss the impact of the IMF on our DM inferences and argue that this can be non-universal with the lookback time. In particular, we find the Salpeter IMF can be better accommodated by low redshift systems, while producing stellar masses at high-z which are unphysically larger than the estimated dynamical masses (particularly for lower-σ ⋆ systems).
Context. One of the most peculiar characteristics of Active Galactic Nuclei (AGN) is their variab... more Context. One of the most peculiar characteristics of Active Galactic Nuclei (AGN) is their variability over all wavelengths. This property has been used in the past to select AGN samples and is foreseen to be one of the detection techniques applied in future multi-epoch surveys, complementing photometric and spectroscopic methods. Aims. In this paper, we aim to construct and characterise an AGN sample using a multi-epoch dataset in the r band from the SUDARE-VOICE survey. Methods. Our work makes use of the VST monitoring program of an area surrounding the Chandra Deep Field South to select variable sources. We use data spanning a six month period over an area of 2 square degrees, to identify AGN based on their photometric variability.
Monthly Notices of the Royal Astronomical Society, 2015
The joint analysis of clustering and stacked gravitational lensing of galaxy clusters in large su... more The joint analysis of clustering and stacked gravitational lensing of galaxy clusters in large surveys can constrain the formation and evolution of structures and the cosmological parameters. On scales outside a few virial radii, the halo bias, b, is linear and the lensing signal is dominated by the correlated distribution of matter around galaxy clusters. We discuss a method to measure the power spectrum amplitude σ 8 and b based on a minimal modelling. We considered a sample of ∼ 120000 clusters photometrically selected from the Sloan Digital Sky Survey in the redshift range 0.1 < z < 0.6. The auto-correlation was studied through the two-point function of a subsample of ∼ 70000 clusters; the matter-halo correlation was derived from the weak lensing signal of the subsample of ∼ 1200 clusters with Canada-France-Hawaii Lensing Survey data. We obtained a direct measurement of b, which increases with mass in agreement with predictions of the ΛCDM paradigm. Assuming Ω M = 0.3, we found σ 8 = 0.78 ± 0.17. We used the same clusters for measuring both lensing and clustering and the estimate of σ 8 did require neither the mass-richness relation, nor the knowledge of the selection function, nor the modelling of b. With an additional theoretical prior on the bias, we obtained σ 8 = 0.80 ± 0.10.
On Recent Developments in Theoretical and Experimental General Relativity, Gravitation and Relativistic Field Theories (In 3 Volumes), 2002
Abstract Photometric and astrometric microlensing (muL) observations are the only way to detect p... more Abstract Photometric and astrometric microlensing (muL) observations are the only way to detect planets around stars at very large distances 1. We show that the capability of photometric muL extends to the detection of signals caused by planets around stars in nearby galaxies (eg M31). No other method that can achieve this 2...
On Recent Developments in Theoretical and Experimental General Relativity, Gravitation and Relativistic Field Theories (In 3 Volumes), 2002
Abstract Gravitational leasing plays an important role in studing the cosmological parameters, si... more Abstract Gravitational leasing plays an important role in studing the cosmological parameters, since propagation of light rays in curved spacetime is intrinsically connected to the structure of the universe. In particular, it depends also on the clumps of matter that it encounters on its way from the source to the observer...
Context. The statistics of peaks in weak lensing convergence maps is a promising tool to investig... more Context. The statistics of peaks in weak lensing convergence maps is a promising tool to investigate both the properties of dark matter haloes and constrain the cosmological parameters. Aims. We study how the number of detectable peaks and its scaling with redshift depend upon the cluster dark matter halo profiles and use peak statistics to constrain the parameters of the mass -concentration (MC) relation. We investigate which constraints the Euclid mission can set on the MC coefficients also taking into account degeneracies with the cosmological parameters. Methods. To this end, we first estimate the number of peaks and its redshift distribution for different MC relations. We find that the steeper the mass dependence and the larger the normalisation, the higher is the number of detectable clusters, with the total number of peaks changing up to 40% depending on the MC relation. We then perform a Fisher matrix forecast of the errors on the MC relation parameters as well as cosmological parameters. Results. We find that peak number counts detected by Euclid can determine the normalization A v , the mass B v and redshift C v slopes and intrinsic scatter σ v of the MC relation to an unprecedented accuracy being
Proceedings of the International Astronomical Union, 2006
We present a study of the morphologies and stellar content of the galaxies in the central ∼ 74" ×... more We present a study of the morphologies and stellar content of the galaxies in the central ∼ 74" × 64" region of the galaxy cluster Abell 2218 (see ). The spectroscopic data were obtained with the integral field unit PMAS in the PPAK mode , at the 3.5 m telescope of the Calar Alto Observatory. The covered wavelength range was 4650-8000Å, with a spectral resolution FWHM ∼ 10Å. These data were combined with with deep HST/ACS F475W, F555W, F625W and F850LP imaging, and additional data from the literature.
ABSTRACT The SUpernova Diversity And Rate Evolution (SUDARE) programme on the VLT Survey Telescop... more ABSTRACT The SUpernova Diversity And Rate Evolution (SUDARE) programme on the VLT Survey Telescope aims to collect an unbiased and homogeneous sample of supernovae (SNe) in all types of galaxies out to redshift ~ 0.6. In four years, around 500 Type Ia and core-collapse SNe are expected to be discovered, including significant numbers of rare SN types. The programme is outlined and 100 SNe candidates have already been detected in the first year of the programme. Follow-up spectroscopy of the SN candidates, an important aspect of the programme, is also described.
Abstract: We present an integral field spectroscopy survey of rich clusters of galaxies aimed at ... more Abstract: We present an integral field spectroscopy survey of rich clusters of galaxies aimed at studying their lensing properties. Thanks to knowledge of the spectroscopic caracteristics of more than three families of multiple images in a single lens, one is able in principle to derive constraints on the geometric cosmological parameters. We show that this ambitious program is feasible and present some new results, in particular the redshift measurement of the giant arc in A2667 and the resdshift confirmation of the counter-image of the radial arc ...
N-body + hydrodynamical simulations of formation and evolution of galaxy groups in a ΛCDM cosmolo... more N-body + hydrodynamical simulations of formation and evolution of galaxy groups in a ΛCDM cosmology have been performed. The properties of the galaxy populations in 12 groups are here discussed, with focus on the colour-magnitude relation in both normal and fossil groups.
Abstract This is a report of Chandra, XMM-Newton, HST, and ARC observations of an extended X-ray ... more Abstract This is a report of Chandra, XMM-Newton, HST, and ARC observations of an extended X-ray source at z= 0.33. The apparent member galaxies range from spiral to elliptical and are relatively red (i&amp;#x27;-Ks about 3). We interpret this object to be a young fossil group which has somehow managed to suppress the star formation rate of the resident galaxies. This complex system sheds new light on the origin and evolution of galaxies in fossil groups and the relationship of fossil groups to poor clusters. The system also ...
The only way to detect planets around stars at distances several kpc is by (photometric or astrom... more The only way to detect planets around stars at distances several kpc is by (photometric or astrometric) microlensing (µL) observations. In this paper, we show that the capability of photometric µL extends to the detection of signals caused by planets around stars in nearby galaxies (e.g. M31) and that there is no other method that can achieve this. Due to the large crowding, µL experiments towards M31 can only observe the high-magnification part of a lensing light curve. Therefore, the dominating channel for µL signals by planets is in distortions near the peak of high-magnification events as discussed by ). We calculate the probability to detect planetary anomalies for µL experiments towards M31 and find that jupiter-like planets around stars in M31 can be detected. Though the characterization of the planet(s) involved in this signal will be difficult, the absence of such signals can yield strong constraints on the abundance of jupiter-like planets.
... This is consistent with recent VLA observations showing that HI is detected in galaxies locat... more ... This is consistent with recent VLA observations showing that HI is detected in galaxies located in the east half of the cluster but not in the west half, therefore suggesting that their HI content has been stripped by a merger coming from the west (Bravo-Alfaro et al. in preparation). ...
Monthly Notices of the Royal Astronomical Society, 2014
We investigate the evolution of dark and luminous matter in the central regions of early-type gal... more We investigate the evolution of dark and luminous matter in the central regions of early-type galaxies (ETGs) up to z ∼ 0.8. We use a spectroscopically selected sample of 154 cluster and field galaxies from the EDisCS survey, covering a wide range in redshifts (z ∼ 0.4-0.8), stellar masses (log M ⋆ /M ⊙ ∼ 10.5-11.5 dex) and velocity dispersions (σ ⋆ ∼ 100-300 km/s). We obtain central dark matter (DM) fractions by determining the dynamical masses from Jeans modelling of galaxy aperture velocity dispersions and the M ⋆ from galaxy colours, and compare the results with local samples. We discuss how the correlations of central DM with galaxy size (i.e. the effective radius, R e ), M ⋆ and σ ⋆ evolve as a function of redshift, finding clear indications that local galaxies are, on average, more DM dominated than their counterparts at larger redshift. This DM fraction evolution with z can be only partially interpreted as a consequence of the size-redshift evolution. We discuss our results within galaxy formation scenarios, and conclude that the growth in size and DM content which we measure within the last 7 Gyr is incompatible with passive evolution, while it is well reproduced in the multiple minor merger scenario. We also discuss the impact of the IMF on our DM inferences and argue that this can be non-universal with the lookback time. In particular, we find the Salpeter IMF can be better accommodated by low redshift systems, while producing stellar masses at high-z which are unphysically larger than the estimated dynamical masses (particularly for lower-σ ⋆ systems).
Context. One of the most peculiar characteristics of Active Galactic Nuclei (AGN) is their variab... more Context. One of the most peculiar characteristics of Active Galactic Nuclei (AGN) is their variability over all wavelengths. This property has been used in the past to select AGN samples and is foreseen to be one of the detection techniques applied in future multi-epoch surveys, complementing photometric and spectroscopic methods. Aims. In this paper, we aim to construct and characterise an AGN sample using a multi-epoch dataset in the r band from the SUDARE-VOICE survey. Methods. Our work makes use of the VST monitoring program of an area surrounding the Chandra Deep Field South to select variable sources. We use data spanning a six month period over an area of 2 square degrees, to identify AGN based on their photometric variability.
Monthly Notices of the Royal Astronomical Society, 2015
The joint analysis of clustering and stacked gravitational lensing of galaxy clusters in large su... more The joint analysis of clustering and stacked gravitational lensing of galaxy clusters in large surveys can constrain the formation and evolution of structures and the cosmological parameters. On scales outside a few virial radii, the halo bias, b, is linear and the lensing signal is dominated by the correlated distribution of matter around galaxy clusters. We discuss a method to measure the power spectrum amplitude σ 8 and b based on a minimal modelling. We considered a sample of ∼ 120000 clusters photometrically selected from the Sloan Digital Sky Survey in the redshift range 0.1 < z < 0.6. The auto-correlation was studied through the two-point function of a subsample of ∼ 70000 clusters; the matter-halo correlation was derived from the weak lensing signal of the subsample of ∼ 1200 clusters with Canada-France-Hawaii Lensing Survey data. We obtained a direct measurement of b, which increases with mass in agreement with predictions of the ΛCDM paradigm. Assuming Ω M = 0.3, we found σ 8 = 0.78 ± 0.17. We used the same clusters for measuring both lensing and clustering and the estimate of σ 8 did require neither the mass-richness relation, nor the knowledge of the selection function, nor the modelling of b. With an additional theoretical prior on the bias, we obtained σ 8 = 0.80 ± 0.10.
On Recent Developments in Theoretical and Experimental General Relativity, Gravitation and Relativistic Field Theories (In 3 Volumes), 2002
Abstract Photometric and astrometric microlensing (muL) observations are the only way to detect p... more Abstract Photometric and astrometric microlensing (muL) observations are the only way to detect planets around stars at very large distances 1. We show that the capability of photometric muL extends to the detection of signals caused by planets around stars in nearby galaxies (eg M31). No other method that can achieve this 2...
On Recent Developments in Theoretical and Experimental General Relativity, Gravitation and Relativistic Field Theories (In 3 Volumes), 2002
Abstract Gravitational leasing plays an important role in studing the cosmological parameters, si... more Abstract Gravitational leasing plays an important role in studing the cosmological parameters, since propagation of light rays in curved spacetime is intrinsically connected to the structure of the universe. In particular, it depends also on the clumps of matter that it encounters on its way from the source to the observer...
Context. The statistics of peaks in weak lensing convergence maps is a promising tool to investig... more Context. The statistics of peaks in weak lensing convergence maps is a promising tool to investigate both the properties of dark matter haloes and constrain the cosmological parameters. Aims. We study how the number of detectable peaks and its scaling with redshift depend upon the cluster dark matter halo profiles and use peak statistics to constrain the parameters of the mass -concentration (MC) relation. We investigate which constraints the Euclid mission can set on the MC coefficients also taking into account degeneracies with the cosmological parameters. Methods. To this end, we first estimate the number of peaks and its redshift distribution for different MC relations. We find that the steeper the mass dependence and the larger the normalisation, the higher is the number of detectable clusters, with the total number of peaks changing up to 40% depending on the MC relation. We then perform a Fisher matrix forecast of the errors on the MC relation parameters as well as cosmological parameters. Results. We find that peak number counts detected by Euclid can determine the normalization A v , the mass B v and redshift C v slopes and intrinsic scatter σ v of the MC relation to an unprecedented accuracy being
Proceedings of the International Astronomical Union, 2006
We present a study of the morphologies and stellar content of the galaxies in the central ∼ 74" ×... more We present a study of the morphologies and stellar content of the galaxies in the central ∼ 74" × 64" region of the galaxy cluster Abell 2218 (see ). The spectroscopic data were obtained with the integral field unit PMAS in the PPAK mode , at the 3.5 m telescope of the Calar Alto Observatory. The covered wavelength range was 4650-8000Å, with a spectral resolution FWHM ∼ 10Å. These data were combined with with deep HST/ACS F475W, F555W, F625W and F850LP imaging, and additional data from the literature.
ABSTRACT The SUpernova Diversity And Rate Evolution (SUDARE) programme on the VLT Survey Telescop... more ABSTRACT The SUpernova Diversity And Rate Evolution (SUDARE) programme on the VLT Survey Telescope aims to collect an unbiased and homogeneous sample of supernovae (SNe) in all types of galaxies out to redshift ~ 0.6. In four years, around 500 Type Ia and core-collapse SNe are expected to be discovered, including significant numbers of rare SN types. The programme is outlined and 100 SNe candidates have already been detected in the first year of the programme. Follow-up spectroscopy of the SN candidates, an important aspect of the programme, is also described.
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Papers by Giovanni Covone