Jaime Forero | Universidad de los Andes (Colombia) (original) (raw)
Papers by Jaime Forero
Astronomy & Astrophysics, 2014
ABSTRACT We analyzed the Einstein radius, thetaE\theta_EthetaE, in our sample of SL2S galaxy groups, and co... more ABSTRACT We analyzed the Einstein radius, thetaE\theta_EthetaE, in our sample of SL2S galaxy groups, and compared it with RAR_ARA (the distance from the arcs to the center of the lens), using three different approaches: 1.- the velocity dispersion obtained from weak lensing assuming a Singular Isothermal Sphere profile ($\theta_{E,I}$), 2.- a strong lensing analytical method ($\theta_{E,II}$) combined with a velocity dispersion-concentration relation derived from numerical simulations designed to mimic our group sample, 3.- strong lensing modeling ($\theta_{E,III}$) of eleven groups (with four new models presented in this work) using HST and CFHT images. Finally, RAR_ARA was analyzed as a function of redshift zzz to investigate possible correlations with L, N, and the richness-to-luminosity ratio (N/L). We found a correlation between thetaE\theta_{E}thetaE and RAR_ARA, but with large scatter. We estimate thetaE,I\theta_{E,I}thetaE,I = (2.2 pm\pmpm 0.9) + (0.7 pm\pmpm 0.2)$R_A$, thetaE,II\theta_{E,II}thetaE,II = (0.4 pm\pmpm 1.5) + (1.1 pm\pmpm 0.4)$R_A$, and thetaE,III\theta_{E,III}thetaE,III = (0.4 pm\pmpm 1.5) + (0.9 pm\pmpm 0.3)$R_A$ for each method respectively. We found a weak evidence of anti-correlation between RAR_ARA and zzz, with Log$R_A$ = (0.58$\pm$0.06) - (0.04$\pm$0.1)$z$, suggesting a possible evolution of the Einstein radius with zzz, as reported previously by other authors. Our results also show that RAR_ARA is correlated with L and N (more luminous and richer groups have greater RAR_ARA), and a possible correlation between RAR_ARA and the N/L ratio. Our analysis indicates that RAR_ARA is correlated with thetaE\theta_EthetaE in our sample, making RAR_ARA useful to characterize properties like L and N (and possible N/L) in galaxy groups. Additionally, we present evidence suggesting that the Einstein radius evolves with zzz.
Monthly Notices of the Royal Astronomical Society, 2009
We introduce the contour process to describe the geometrical properties of merger trees. The cont... more We introduce the contour process to describe the geometrical properties of merger trees. The contour process translates a tree structure into a one-dimensional object: the contour walk. We characterize the contour walk measuring its length and action. The length is proportional to the number of progenitors in the tree, and the action is a proxy for the mean length of a branch in the tree.
Monthly Notices of the Royal Astronomical Society, 2011
We present the implementation of a halo based method for the reconstruction of the cosmic mass de... more We present the implementation of a halo based method for the reconstruction of the cosmic mass density field. The method employs the mass density distribution of dark matter haloes and its environments computed from cosmological N-body simulations and convolves it with a halo catalog to reconstruct the dark matter density field determined by the distribution of haloes. We applied the method to the group catalog of Yang et al. built from the SDSS Data Release 4. As result we obtain reconstructions of the cosmic mass density field that are independent on any explicit assumption of bias. We describe in detail the implementation of the method, present a detailed characterization of the reconstructed density field (mean mass density distribution, correlation function and counts in cells) and the results of the classification of large scale environments (filaments, voids, peaks and sheets) in our reconstruction. Applications of the method include morphological studies of the galaxy population on large scales and the realization of constrained simulations.
Monthly Notices of the Royal Astronomical Society, 2009
A dynamical classification of the cosmic web is proposed. The large scale environment is classifi... more A dynamical classification of the cosmic web is proposed. The large scale environment is classified into four web types: voids, sheets, filaments and knots. The classification is based on the evaluation of the deformation tensor, i.e. the Hessian of the gravitational potential, on a grid. The classification is based on counting the number of eigenvalues above a certain threshold, λ th , at each grid point, where the case of zero, one, two or three such eigenvalues corresponds to void, sheet, filament or a knot grid point. The collection of neighboring grid points, friends-of-friends, of the same web attribute constitutes voids, sheets, filaments and knots as web objects.
Monthly Notices of the Royal Astronomical Society, 2013
The alignment of dark matter (DM) halos and the surrounding large scale structure (LSS) is examin... more The alignment of dark matter (DM) halos and the surrounding large scale structure (LSS) is examined in the context of the cosmic web. Halo spin, shape and the orbital angular momentum of subhaloes is investigated relative to the LSS using the eigenvectors of the velocity shear tensor evaluated on a grid with a scale of 1 Mpc/h, deep within the non-linear regime. Knots, filaments, sheets and voids are associated with regions that are collapsing along 3, 2, 1 or 0 principal directions simultaneously. Each halo is tagged with a web classification (i.e. knot halo, filament halo, etc) according to the nature of the collapse at the halos position. The full distribution of shear eigenvalues is found to be substantially different from that tagged to haloes, indicating that the observed velocity shear is significantly biased. We find that larger mass haloes live in regions where the shear is more isotropic, namely the expansion or collapse is more spherical. A correlation is found between the halos shape and the eigenvectors of the shear tensor, with the longest (shortest) axis of the halos shape being aligned with the slowest (fastest) collapsing eigenvector. This correlation is web independent, suggesting that the velocity shear is a fundamental tracer of the halo alignment. A similar result is found for the alignment of halo spin with the cosmic web. It has been shown that high mass haloes exhibit a spin flip with respect to the LSS: we find the mass at which this spin flip occurs is web dependent and not universal as suggested previously. Although weaker than haloes, subhalo orbits too exhibit an alignment with the LSS, providing a possible insight into the highly correlated co-rotation of the Milky Ways satellite system. The present study suggests that the velocity shear tensor constitutes the natural framework for studying the directional properties of the non-linear LSS and of halos and galaxies.
Monthly Notices of the Royal Astronomical Society, 2007
We present the Lensed Mock Map Facility (LeMoMaF), a tool designed to perform mock weak lensing m... more We present the Lensed Mock Map Facility (LeMoMaF), a tool designed to perform mock weak lensing measurements on numerically simulated chunks of the universe. Coupling N-body simulations to a semi-analytical model of galaxy formation, LeMo-MaF can create realistic lensed images and mock catalogues of galaxies, at wavelengths ranging from the UV to the submm. To demonstrate the power of such a tool we compute predictions of the source-lens clustering effect on the convergence statistics, and quantify the impact of weak lensing on galaxy counts in two different filters. We find that the source-lens clustering effect skews the probability density function of the convergence towards low values, with an intensity which strongly depends on the redshift distribution of galaxies. On the other hand, the degree of enhancement or depletion in galaxy counts due to weak lensing is independent of the source-lens clustering effect. We discuss the impact on the two-points shear statistics to be measured by future missions like SNAP and LSST. The source-lens clustering effect would bias the estimation of σ 8 from two point statistics by 2% − 5%. We conclude that accurate photometric redshifts for individual galaxies are necessary in order to quantify and isolate the source-lens clustering effect.
The Astrophysical Journal, 2013
Recent observations constrained the tangential velocity of M31 with respect to the Milky Way (MW)... more Recent observations constrained the tangential velocity of M31 with respect to the Milky Way (MW) to be v M31,tan < 34.4 km s −1 and the radial velocity to be in the range v M31,rad = −109 ± 4.4 km s −1 (van der . In this study we use a large volume high resolution N-body cosmological simulation (Bolshoi) together with three constrained simulations to statistically study this kinematics in the context of the ΛCDM. The comparison of the ensembles of simulated pairs with the observed LG at the 1-σ level in the uncertainties has been done with respect to the radial and tangential velocities, the reduced orbital energy (e tot ), angular momentum (l orb ) and the dimensionless spin parameter, λ. Our main results are: (i) the preferred radial and tangential velocities for pairs in ΛCDM are v r = −80 ± 20 km s −1 , v t = 50 ± 10 km s −1 , (ii) pairs around that region are 3 to 13 times more common than pairs within the observational values, (iii) 15% to 24% of LG-like pairs in ΛCDM have energy and angular momentum consistent with observations while (iv) 9% to 13% of pairs in the same sample show similar values in the inferred dimensionless spin parameter. It follows that within current observational uncertainties the quasi-conserved quantities that characterize the orbit of the LG, i.e. e tot , l orb and λ, do not challenge the standard ΛCDM model, but the model is in tension with regard to the actual values of the radial and tangential velocities. This might hint to a problem of the ΛCDM model to reproduce the observed LG.
Astronomy & Astrophysics, 2014
ABSTRACT We analyzed the Einstein radius, thetaE\theta_EthetaE, in our sample of SL2S galaxy groups, and co... more ABSTRACT We analyzed the Einstein radius, thetaE\theta_EthetaE, in our sample of SL2S galaxy groups, and compared it with RAR_ARA (the distance from the arcs to the center of the lens), using three different approaches: 1.- the velocity dispersion obtained from weak lensing assuming a Singular Isothermal Sphere profile ($\theta_{E,I}$), 2.- a strong lensing analytical method ($\theta_{E,II}$) combined with a velocity dispersion-concentration relation derived from numerical simulations designed to mimic our group sample, 3.- strong lensing modeling ($\theta_{E,III}$) of eleven groups (with four new models presented in this work) using HST and CFHT images. Finally, RAR_ARA was analyzed as a function of redshift zzz to investigate possible correlations with L, N, and the richness-to-luminosity ratio (N/L). We found a correlation between thetaE\theta_{E}thetaE and RAR_ARA, but with large scatter. We estimate thetaE,I\theta_{E,I}thetaE,I = (2.2 pm\pmpm 0.9) + (0.7 pm\pmpm 0.2)$R_A$, thetaE,II\theta_{E,II}thetaE,II = (0.4 pm\pmpm 1.5) + (1.1 pm\pmpm 0.4)$R_A$, and thetaE,III\theta_{E,III}thetaE,III = (0.4 pm\pmpm 1.5) + (0.9 pm\pmpm 0.3)$R_A$ for each method respectively. We found a weak evidence of anti-correlation between RAR_ARA and zzz, with Log$R_A$ = (0.58$\pm$0.06) - (0.04$\pm$0.1)$z$, suggesting a possible evolution of the Einstein radius with zzz, as reported previously by other authors. Our results also show that RAR_ARA is correlated with L and N (more luminous and richer groups have greater RAR_ARA), and a possible correlation between RAR_ARA and the N/L ratio. Our analysis indicates that RAR_ARA is correlated with thetaE\theta_EthetaE in our sample, making RAR_ARA useful to characterize properties like L and N (and possible N/L) in galaxy groups. Additionally, we present evidence suggesting that the Einstein radius evolves with zzz.
Monthly Notices of the Royal Astronomical Society, 2009
We introduce the contour process to describe the geometrical properties of merger trees. The cont... more We introduce the contour process to describe the geometrical properties of merger trees. The contour process translates a tree structure into a one-dimensional object: the contour walk. We characterize the contour walk measuring its length and action. The length is proportional to the number of progenitors in the tree, and the action is a proxy for the mean length of a branch in the tree.
Monthly Notices of the Royal Astronomical Society, 2011
We present the implementation of a halo based method for the reconstruction of the cosmic mass de... more We present the implementation of a halo based method for the reconstruction of the cosmic mass density field. The method employs the mass density distribution of dark matter haloes and its environments computed from cosmological N-body simulations and convolves it with a halo catalog to reconstruct the dark matter density field determined by the distribution of haloes. We applied the method to the group catalog of Yang et al. built from the SDSS Data Release 4. As result we obtain reconstructions of the cosmic mass density field that are independent on any explicit assumption of bias. We describe in detail the implementation of the method, present a detailed characterization of the reconstructed density field (mean mass density distribution, correlation function and counts in cells) and the results of the classification of large scale environments (filaments, voids, peaks and sheets) in our reconstruction. Applications of the method include morphological studies of the galaxy population on large scales and the realization of constrained simulations.
Monthly Notices of the Royal Astronomical Society, 2009
A dynamical classification of the cosmic web is proposed. The large scale environment is classifi... more A dynamical classification of the cosmic web is proposed. The large scale environment is classified into four web types: voids, sheets, filaments and knots. The classification is based on the evaluation of the deformation tensor, i.e. the Hessian of the gravitational potential, on a grid. The classification is based on counting the number of eigenvalues above a certain threshold, λ th , at each grid point, where the case of zero, one, two or three such eigenvalues corresponds to void, sheet, filament or a knot grid point. The collection of neighboring grid points, friends-of-friends, of the same web attribute constitutes voids, sheets, filaments and knots as web objects.
Monthly Notices of the Royal Astronomical Society, 2013
The alignment of dark matter (DM) halos and the surrounding large scale structure (LSS) is examin... more The alignment of dark matter (DM) halos and the surrounding large scale structure (LSS) is examined in the context of the cosmic web. Halo spin, shape and the orbital angular momentum of subhaloes is investigated relative to the LSS using the eigenvectors of the velocity shear tensor evaluated on a grid with a scale of 1 Mpc/h, deep within the non-linear regime. Knots, filaments, sheets and voids are associated with regions that are collapsing along 3, 2, 1 or 0 principal directions simultaneously. Each halo is tagged with a web classification (i.e. knot halo, filament halo, etc) according to the nature of the collapse at the halos position. The full distribution of shear eigenvalues is found to be substantially different from that tagged to haloes, indicating that the observed velocity shear is significantly biased. We find that larger mass haloes live in regions where the shear is more isotropic, namely the expansion or collapse is more spherical. A correlation is found between the halos shape and the eigenvectors of the shear tensor, with the longest (shortest) axis of the halos shape being aligned with the slowest (fastest) collapsing eigenvector. This correlation is web independent, suggesting that the velocity shear is a fundamental tracer of the halo alignment. A similar result is found for the alignment of halo spin with the cosmic web. It has been shown that high mass haloes exhibit a spin flip with respect to the LSS: we find the mass at which this spin flip occurs is web dependent and not universal as suggested previously. Although weaker than haloes, subhalo orbits too exhibit an alignment with the LSS, providing a possible insight into the highly correlated co-rotation of the Milky Ways satellite system. The present study suggests that the velocity shear tensor constitutes the natural framework for studying the directional properties of the non-linear LSS and of halos and galaxies.
Monthly Notices of the Royal Astronomical Society, 2007
We present the Lensed Mock Map Facility (LeMoMaF), a tool designed to perform mock weak lensing m... more We present the Lensed Mock Map Facility (LeMoMaF), a tool designed to perform mock weak lensing measurements on numerically simulated chunks of the universe. Coupling N-body simulations to a semi-analytical model of galaxy formation, LeMo-MaF can create realistic lensed images and mock catalogues of galaxies, at wavelengths ranging from the UV to the submm. To demonstrate the power of such a tool we compute predictions of the source-lens clustering effect on the convergence statistics, and quantify the impact of weak lensing on galaxy counts in two different filters. We find that the source-lens clustering effect skews the probability density function of the convergence towards low values, with an intensity which strongly depends on the redshift distribution of galaxies. On the other hand, the degree of enhancement or depletion in galaxy counts due to weak lensing is independent of the source-lens clustering effect. We discuss the impact on the two-points shear statistics to be measured by future missions like SNAP and LSST. The source-lens clustering effect would bias the estimation of σ 8 from two point statistics by 2% − 5%. We conclude that accurate photometric redshifts for individual galaxies are necessary in order to quantify and isolate the source-lens clustering effect.
The Astrophysical Journal, 2013
Recent observations constrained the tangential velocity of M31 with respect to the Milky Way (MW)... more Recent observations constrained the tangential velocity of M31 with respect to the Milky Way (MW) to be v M31,tan < 34.4 km s −1 and the radial velocity to be in the range v M31,rad = −109 ± 4.4 km s −1 (van der . In this study we use a large volume high resolution N-body cosmological simulation (Bolshoi) together with three constrained simulations to statistically study this kinematics in the context of the ΛCDM. The comparison of the ensembles of simulated pairs with the observed LG at the 1-σ level in the uncertainties has been done with respect to the radial and tangential velocities, the reduced orbital energy (e tot ), angular momentum (l orb ) and the dimensionless spin parameter, λ. Our main results are: (i) the preferred radial and tangential velocities for pairs in ΛCDM are v r = −80 ± 20 km s −1 , v t = 50 ± 10 km s −1 , (ii) pairs around that region are 3 to 13 times more common than pairs within the observational values, (iii) 15% to 24% of LG-like pairs in ΛCDM have energy and angular momentum consistent with observations while (iv) 9% to 13% of pairs in the same sample show similar values in the inferred dimensionless spin parameter. It follows that within current observational uncertainties the quasi-conserved quantities that characterize the orbit of the LG, i.e. e tot , l orb and λ, do not challenge the standard ΛCDM model, but the model is in tension with regard to the actual values of the radial and tangential velocities. This might hint to a problem of the ΛCDM model to reproduce the observed LG.