Papers by Hector Andres Cuevas Larenas
cucg, Mar 1, 2000
We present the results of a dynamical analysis of three rich, X-ray luminous galaxy clusters, Abe... more We present the results of a dynamical analysis of three rich, X-ray luminous galaxy clusters, Abell 222, Abell 223 and Abell 520, that are at intermediate redshifts. Our study is based on radial velocities for 71 cluster members, respectively 30 for A222, 20 for A223 and 21 for A520, measured from spectra obtained at the Canada-France-Hawaii Telescope, the European Southern Observatory, and the Pic du Midi Observatory, and supplemented with radial velocities from the literature. A222 galaxies have slightly higher velocities than those of A223, with bi-weighted mean velocity of V bi = 64242 ± 194 km s −1 for A222, and of V bi = 63197 ± 266 km s −1 for A223. The velocity dispersions of the two clusters are about the same: σ bi = 1013 ± 150 km s −1 and σ bi = 1058 ± 160 km s −1 for A222 and A223, respectively. For A520 we obtain V bi = 60127 ± 284 km s −1 with σ bi = 1250 ± 189 km s −1. We also give mass and massluminosities ratio estimates for each cluster separately. We argue that these clusters are presently undergoing strong dynamical evolution and that A222 and A223 will probably merge in the future. We have applied a Principal Component Analysis to a sample of 51 CFHT spectra to produce a spectral classification for these galaxies. This classification has allowed us to show that the morphological and kinematical segregations were already established in these intermediate redshift clusters.
We present an analysis of the environment of six QSO triplets at 1 . z . 1.5 by analyzing multiba... more We present an analysis of the environment of six QSO triplets at 1 . z . 1.5 by analyzing multiband (r, i, z, or g, r, i) images obtained with Megacam at the CFHT telescope, aiming to investigate whether they are associated or not with galaxy protoclusters. This was done by using photometric redshifts trained using the high accuracy photometric redshifts of the COSMOS2015 catalogue. To improve the quality of our photometric redshift estimation, we included in our analysis near-infrared photometry (3.6 and 4.5μm) from the unWISE survey available for our fields and the COSMOS survey. This approach allowed us to obtain good photometric redshifts with dispersion, as measured with the robust σNMAD statistics (which scales as (1+z)−1), of∼0.04 for our six fields. Our analysis setup was reproduced on lightcones constructed from the Millennium Simulation data and the latest version of the L-GALAXIES semi-analytic model to verify the protocluster detectability in such conditions. The density...
Monthly Notices of the Royal Astronomical Society, 2021
The progenitors of present-day galaxy clusters give important clues about the evolution of the la... more The progenitors of present-day galaxy clusters give important clues about the evolution of the large-scale structure, cosmic mass assembly, and galaxy evolution. Simulations are a major tool for these studies since they are used to interpret observations. In this work, we introduce a set of ‘protocluster-light-cones’, dubbed PCcones. They are mock galaxy catalogues generated from the Millennium Simulation with the L-GALAXIES semi-analytic model. These light-cones were constructed by placing a desired structure at the redshift of interest in the centre of the cone. This approach allows to adopt a set of observational constraints, such as magnitude limits and uncertainties in magnitudes and photometric redshifts (photo-zs) to produce realistic simulations of photometric surveys. We show that photo-zs obtained with PCcones are more accurate than those obtained directly with the Millennium Simulation, mostly due to the difference in how apparent magnitudes are computed. We apply PCcones...
Publications of the Astronomical Society of the Pacific, 2018
We present a new global array of small aperture optical telescopes designed to study artificial s... more We present a new global array of small aperture optical telescopes designed to study artificial satellites and the nearby universe: the Falcon Telescope Network (FTN). Developed by the Center for Space Situational Awareness Research in the Department of Physics at the United States Air Force Academy (USAFA), the FTN is composed of 12 observatories in the United States, Chile, Germany, and Australia, with a potential site in South Africa. The observatory sites were strategically selected with the main objective that once in operation, the telescopes will be capable of working together to perform simultaneous and/or continuous observations of a single object in the sky. This capability allows the observation of artificial satellites from different baselines in a wide range of orbits, continuous data acquisition of variable astronomical sources, and rapid response observations of transient phenomena that require almost immediate follow-up (gamma-ray bursts, novae, or supernovae, etc.). Consisting of commercially available equipment, each observatory is equipped with a 0.5 m primary mirror telescope, a CCD camera, photometric filters, including a special filter to detect exoplanets, and a diffraction grating. The FTN is designed for remote and robotic operation with a host of automation software and services housed on the site computers and at USAFA. FTN partners will have access to a web-based interface where both the observation application as well as the raw data obtained by any of the Falcon nodes will be available. The FTN is a collaborative effort between the USAFA and educational or research institutions on four continents, demonstrating that, through the cooperation of multiple institutions of different levels and capabilities, high-level scientific and educational programs can be carried out, regardless of the geographic location of the various network members.
Monthly Notices of the Royal Astronomical Society, 2020
We present the methods and results of the optical follow-up, conducted by the Transient Optical R... more We present the methods and results of the optical follow-up, conducted by the Transient Optical Robotic Observatory of the South Collaboration, of gravitational wave events detected during the Advanced LIGO–Virgo second observing run (2016 November–2017 August). Given the limited field of view (∼100 arcmin) of our observational instrumentation, we targeted galaxies within the area of high localization probability that were observable from our sites. We analysed the observations using difference imaging, followed by a random forest algorithm to discriminate between real and spurious transients. Our observations were conducted using telescopes at Estación Astrofísica de Bosque Alegre, Cerro Tololo Inter-American Observatory, the Dr. Cristina V. Torres Memorial Astronomical Observatory, and an observing station in Salta, Argentina.
![Research paper thumbnail of Witnessing the Formation of a Galaxy Cluster atz= 0.485: Optical and X‐Ray Properties of RX J1117.4+0743 ([VMF 98] 097)](https://attachments.academia-assets.com/93969963/thumbnails/1.jpg)
The Astrophysical Journal, 2007
We present a multiwavelength study of the poor cluster RX J1117.4+0743 ([VMF 98] 097) at z=0.485,... more We present a multiwavelength study of the poor cluster RX J1117.4+0743 ([VMF 98] 097) at z=0.485, based on GMOS/Gemini South g ′ , r ′ photometry and spectroscopy, and XMM-Newton observations. We examine its nature and surroundings by analyzing the projected galaxy distribution, the galaxy velocity distribution, the weak-lensing mass reconstruction, and the X-ray spectroscopy and imaging. The cluster shows a complex morphology. It is composed by at least two structures along the line-of-sight, with velocity dispersions of 592±82 km s −1 and 391±85 km s −1 respectively. Other structures are also detected in X-ray, in the galaxy projected number density map, and by weaklensing. One of these clumps, located East from the cluster center, could be gravitationally bound and associated to the main cluster. The derived temperature and bolometric X-ray luminosity reveal that [VMF 98] 097 behave like a normal cluster, in agreement with L X −T X correlation found for both local (z = 0) and moderate redshift (z ∼ 0.4) clusters. We find that the mass determination inferred from weak-lensing is in average 3 to 4.8 times higher (depending on the model assumed) than the X-ray mass. We have two possible explanations for this discrepancy: i) the cluster is in non-equilibrium, then the deviation of the X-ray estimated mass from the true value can be as high as a factor of two; ii) the intervening mass along the line-of-sight of the cluster is producing an over-estimation of the weak-lensing mass. Based on the analysis presented, we conclude that [VMF 98] 097 is a perturbed cluster with at least two substructures in velocity space and with other nearby structures at projected distances of about 1 h −1 70 Mpc. This cluster is an example of a poor cluster caught in the process of accreting sub-structures to become a rich cluster.
Vistas in Astronomy, 1994
We investigate the integrated spectra of a sample of 24 normal galaxies. A principal component an... more We investigate the integrated spectra of a sample of 24 normal galaxies. A principal component analysis suggests that most of the variance present in the spectra is due to the di erences in morphology of the galaxies in the sample. We show that spectroscopic parameters extracted from the spectra, like the amplitude of the 4000 A break or of the CN band, correlate well with Hubble types and are useful for quantitative classi cation.
Arxiv preprint astro-ph/9608143, 1996
Abstract. We have investigated some statistical properties of integrated spectra of galaxies with... more Abstract. We have investigated some statistical properties of integrated spectra of galaxies with principal component analysis. The projection of the spectra onto the plane defined by the first two principal compo-nents shows that normal galaxies are in a quasi-linear sequence ...
The Astrophysical Journal Supplement Series, 2000
... I. OBSERVATIONS AND DATA CALIBRATION H. QUINTANA,1,2 L. INFANTE, P. FOUQUE,3 ER CARRASCO,4 H.... more ... I. OBSERVATIONS AND DATA CALIBRATION H. QUINTANA,1,2 L. INFANTE, P. FOUQUE,3 ER CARRASCO,4 H. CUEVAS,4,5 G ... 1964; Schombert 1987), occasionally with distortions (Johnstone, Taylor, & Fabian 1991), have multiple or complex nuclei (Rood & Leir 1979), may ...
Astronomy and Astrophysics, 2003
We present a dynamical analysis of the galaxy cluster Abell 376 based on a set of 73 velocities, ... more We present a dynamical analysis of the galaxy cluster Abell 376 based on a set of 73 velocities, most of them measured at Pic du Midi and Haute-Provence observatories and completed with data from the literature. Data on individual galaxies are presented and the accuracy of the determined velocities is discussed as well as some properties of the cluster. We obtained an improved mean redshift value z = 0.0478 +0.005 −0.006 and velocity dispersion σ = 852 +120 −76 km s −1. Our analysis indicates that inside a radius of ∼900 h −1 70 kpc (∼15 arcmin) the cluster is well relaxed without any remarkable features and the X-ray emission traces fairly well the galaxy distribution. A possible substructure is seen at 20 arcmin from the centre towards the Southwest direction, but is not confirmed by the velocity field. This SW clump is, however, kinematically bound to the main structure of Abell 376. A dense condensation of galaxies is detected at 46 arcmin (projected distance 2.6 h −1 70 Mpc) from the centre towards the Northwest and analysis of the apparent luminosity distribution of its galaxies suggests that this clump is part of the large scale structure of Abell 376. X-ray spectroscopic analysis of ASCA data resulted in a temperature kT = 4.3 ± 0.4 keV and metal abundance Z = 0.32 ± 0.08 Z. The velocity dispersion corresponding to this temperature using the T X-σ scaling relation is in agreement with the measured galaxies velocities.
Astronomy & Astrophysics, 2001
We present a dynamical analysis of the galaxy cluster Abell 970 based on a new set of radial velo... more We present a dynamical analysis of the galaxy cluster Abell 970 based on a new set of radial velocities measured at ESO, Pic du Midi and Haute-Provence observatories. Our analysis indicates that this cluster has a substructure and is out of dynamical equilibrium. This conclusion is also supported by differences in the positions of the peaks of the surface density distribution and X-ray emission, as well as by the evidence of a large-scale velocity gradient in the cluster. We also found a discrepancy between the masses inferred with the virial theorem and those inferred with the X-ray emission, which is expected if the galaxies and the gas inside the cluster are not in hydrostatic equilibrium. Abell 970 has a modest cooling flow, as is expected if it is out of equilibrium. We propose that cooling flows may have an intermittent behaviour, with phases of massive cooling flows being followed by phases without significant cooling flows after the accretion of a galaxy group massive enough to disrupt the dynamical equilibrium in the centre of the clusters. A massive cooling flow will be established again, after a new equilibrium is achieved.
Monthly Notices of the Royal Astronomical Society, 1997
We have investigated some statistical properties of integrated spectra of galaxies from Kennicutt... more We have investigated some statistical properties of integrated spectra of galaxies from Kennicutt (1992a) spectrophotometric atlas. The input for the analysis are galaxy spectra sampled in 1300 bins between 3750Å and 6500Å. We make use of Principal Component Analysis (PCA) to analyse the 1300-dimensional space spanned by the spectra. Their projection onto the plane defined by the first two principal components, the principal plane, shows that normal galaxies are in a quasi-linear sequence that we call spectral sequence. We show that the spectral sequence is closely related to the Hubble morphological sequence. These results are robust in the sense that the reality of the spectral sequence does not depend on data normalization. The existence of this sequence suggests that a single parameter may describe the spectrum of normal galaxies. We have investigated this hypothesis with Bruzual & Charlot (1995) models of spectral evolution. We show that, for single age models (15 Gyr), the spectral sequence can be parametrized by the characteristic star formation timescales of the different morphological types. By examining the projection of evolutionary tracks of normal galaxies onto the principal plane, we verify that the spectral sequence is also an evolutive sequence, with galaxy spectra evolving from later to earlier spectral types. Considering the close correspondence between the spectral and morphological sequences, this lead us to speculate that galaxies may evolve morphologically along the Hubble sequence, from Sm/Im to E.
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Papers by Hector Andres Cuevas Larenas