Papers by Octavio Valenzuela
Journal of microbiology (Seoul, Korea), 2013
Proceedings of the International Astronomical Union, 2015
We use a dynamical model for the decay of supermassive black hole binaries (BHBs) coupled with a ... more We use a dynamical model for the decay of supermassive black hole binaries (BHBs) coupled with a cosmological simulation and semi-empirical approaches to the occupation of halos by galaxies and BHs, in order to investigate the properties of galaxies hosting BHBs. We found bimodal distributions of hosts properties, with one peak corresponding to BHBs suitable to be detected by PTAs and the other to BHBs in the eLISA frequency window. We note that for some of the scenarios explored there must be a considerable population of such sources in the nearby Universe that might show detectable EM signatures, representing an important laboratory for multimessenger astrophysics.
Monthly Notices of the Royal Astronomical Society
Analysis of large galaxy surveys requires confidence in the robustness of numerical simulation me... more Analysis of large galaxy surveys requires confidence in the robustness of numerical simulation methods. The simulations are used to construct mock galaxy catalogues to validate data analysis pipelines and identify potential systematics. We compare three N-body simulation codes, abacus, gadget-2, and swift, to investigate the regimes in which their results agree. We run N-body simulations at three different mass resolutions, 6.25 × 108, 2.11 × 109, and 5.00 × 109 h−1 M⊙, matching phases to reduce the noise within the comparisons. We find systematic errors in the halo clustering between different codes are smaller than the Dark Energy Spectroscopic Instrument (DESI) statistical error for $s\ \gt\ 20\ h^{-1}$ Mpc in the correlation function in redshift space. Through the resolution comparison we find that simulations run with a mass resolution of 2.1 × 109 h−1 M⊙ are sufficiently converged for systematic effects in the halo clustering to be smaller than the DESI statistical error at sc...
Bulletin of the American Physical Society, 2014
present results from numerical simulations of low-mass galaxies with the aim to explore the way t... more present results from numerical simulations of low-mass galaxies with the aim to explore the way their stellar masses are assembled. We analyze how the mass assembly histories of the parent halo determine the growth of their host galaxy and its implications on the current paradigm of formation and evolution of low-mass structures in the LCDM scenario. We have found that low-mass galaxies simulated in this scenario assemble their stellar masses following roughly the dark matter halo assembly, which seems to be in tension with the downsizing trend suggested by current observational inferences. We show that there is no more room to increase the strength of feedback from astrophysical processes in order to deviate strongly the stellar mass assembly from the dark halo one, as has been recently invoked to solve some of the potential issues faced by CDM-based simulations of dwarf galaxies.
We present a method to implement relativistic corrections to the evolution of dark matter structu... more We present a method to implement relativistic corrections to the evolution of dark matter structures in cosmological simulations of a ΛCDM universe. We take the nonlinear correspondence between the Lagrangian (Newtonian) evolution of dark matter inhomogeneities and the synchronous-comoving (relativistic) matter density description, and use it to promote the relativistic constraint as the initial condition for numerical simulations of structure formation. In this method, the incorporation of Primordial non-Gaussianity (PNG) contributions as initial conditions is straightforward. We implement the relativistic, fNL and gNL contributions as initial conditions for the L-PICOLA code, and derive the power spectrum and bispectrum of the evolved matter field. We focus specifically in the case of largest values of non-Gaussianity allowed at 1-σ by Planck (fNL = −4.2 and gNL = −7000). As a checkup, we show consistency with the one-loop perturbative prescription in the adequate scales. Our resu...
Astronomy & Astrophysics, 2015
Using six-dimensional phase-space information from the Fourth Data release of the RAdial Velocity... more Using six-dimensional phase-space information from the Fourth Data release of the RAdial Velocity Experiment (RAVE) over the range of Galactic longitude 240 • < l < 360 • and V LSR < −239 km s −1 , we computed orbits for 329 RAVE stars that were originally selected as chemically and kinematically related to ω Centauri. The orbits were integrated in a Milky-Way-like axisymmetric Galactic potential, ignoring the effects of the dynamical evolution of ω Centauri due to the tidal effects of the Galaxy disk on the cluster along time. We also ignored secular changes in the Milky Way potential over time. In a Monte Carlo scheme, and under the assumption that the stars may have been ejected with velocities greater than the escape velocity (V rel > V esc,0) from the cluster, we identified 15 stars as having close encounters with ω Centauri: (i) 8 stars with relative velocities V rel < 200 km s −1 may have been ejected ∼200 Myr ago from ω Centauri; (ii) another group of 7 stars were identified with high relative velocity V rel > 200 km s −1 during close encounters, and it seems unlikely that they were ejected from ω Centauri. We also confirm the link between J131340.4-484714 as a potential member of ω Centauri, and probably ejected ∼2.0 Myr ago, with a relative velocity V rel ∼ 80 km s −1 .
arXiv: Instrumentation and Methods for Astrophysics, 2016
DESI (Dark Energy Spectropic Instrument) is a Stage IV ground-based dark energy experiment that w... more DESI (Dark Energy Spectropic Instrument) is a Stage IV ground-based dark energy experiment that will study baryon acoustic oscillations and the growth of structure through redshift-space distortions with a wide-area galaxy and quasar redshift survey. The DESI instrument is a robotically-actuated, fiber-fed spectrograph capable of taking up to 5,000 simultaneous spectra over a wavelength range from 360 nm to 980 nm. The fibers feed ten three-arm spectrographs with resolution $R= \lambda/\Delta\lambda$ between 2000 and 5500, depending on wavelength. The DESI instrument will be used to conduct a five-year survey designed to cover 14,000 deg$^2$. This powerful instrument will be installed at prime focus on the 4-m Mayall telescope in Kitt Peak, Arizona, along with a new optical corrector, which will provide a three-degree diameter field of view. The DESI collaboration will also deliver a spectroscopic pipeline and data management system to reduce and archive all data for eventual public...
DESI (Dark Energy Spectroscopic Instrument) is a Stage IV ground-based dark energy experiment tha... more DESI (Dark Energy Spectroscopic Instrument) is a Stage IV ground-based dark energy experiment that will study baryon acoustic oscillations (BAO) and the growth of structure through redshift-space distortions with a wide-area galaxy and quasar redshift survey. To trace the underlying dark matter distribution, spectroscopic targets will be selected in four classes from imaging data. We will measure luminous red galaxies up to $z=1.0$. To probe the Universe out to even higher redshift, DESI will target bright [O II] emission line galaxies up to $z=1.7$. Quasars will be targeted both as direct tracers of the underlying dark matter distribution and, at higher redshifts ($ 2.1 < z < 3.5$), for the Ly-$\alpha$ forest absorption features in their spectra, which will be used to trace the distribution of neutral hydrogen. When moonlight prevents efficient observations of the faint targets of the baseline survey, DESI will conduct a magnitude-limited Bright Galaxy Survey comprising appro...
The Astrophysical Journal, 2020
We use the stellar kinematics for 2458 galaxies from the Mapping Nearby Galaxies at Apache point ... more We use the stellar kinematics for 2458 galaxies from the Mapping Nearby Galaxies at Apache point observatory (MaNGA) survey to explore dynamical scaling relations between the stellar mass M , and the total velocity parameter at the effective radius, R e , defined as S 2 K = KV 2 Re + σ 2 e , which combines rotation velocity V Re , and velocity dispersion σ e. We confirm that spheroidal and spiral galaxies follow the same M − S 0.5 scaling relation with lower scatter than the M − V Re and M − σ e ones. We also explore a more general two-dimensional surface known as Universal Fundamental Plane described by the equation log(Υ e) = log(S 2 0.5)−log(I e)−log(R e)+C., which in addition to kinematics, S 0.5 , and effective radius, R e , it includes information of the surface brightness, I e , and dynamical mass-to-light ratio, Υ e. We use sophisticated Schwarzschild orbit-based dynamical models for a subsample of 300 galaxies from the CALIFA survey to calibrate the so called Universal Fundamental Plane. That calibration allows us to propose both: (i) a parametrization to estimate the difficult-tomeasure dynamical mass-to-light ratio at the effective radius of galaxies, once the internal kinematics, surface brightness and effective radius are known; and (ii) a new dynamical mass proxy consistent with dynamical models within 0.09 dex. We show that this dynamical mass estimator is more robust that the one previously proposed using only kinematics. We are able to reproduce the relation between the dynamical mass and the stellar mass in the inner regions of galaxies with lower scatter. We use the estimated dynamical mass-to-light ratio from our analysis, Υ f it e , to explore the Universal Fundamental Plane with the MaNGA data set. We find that all classes of galaxies, from spheroids to disks, follow this Universal Fundamental Plane with a scatter significantly smaller (0.05 dex) than the one reported for the M − S 0.5 relation (0.1 dex), the Fundamental Plane (∼ 0.09 dex) and comparable with Tully-Fisher studies (∼ 0.05 dex), but for a wider range of galaxy types.
We explore the density profiles of dark matter halos formed in high-resolution cosmological N-bod... more We explore the density profiles of dark matter halos formed in high-resolution cosmological N-body simulations with power spectra of density fluctuations damped below a given length scale R f. The density profile shape of halos with masses smaller than the mass M f corresponding to R f does not significantly differ from that of the cold dark matter (CDM) halos; on the average, this shape is well described by the Navarro, Frenk, & White profile. However, the concentration of halos less massive than M f remains constant as the mass decreases, while for the CDM halos the concentration increases. The cosmogony of the former halos is not hierarchical but due to fragmentation of pancakes, their typical formation epoch being slightly later than that of halos of mass close to M f. The lower concentrations of these halos relative to the CDM ones may be explained by their late formation. If the suppression of power is associated with the free-streaming damping characteristic for warm dark matter (WDM) particles, then particles will have a residual thermal velocity dispersion v th. We have included this velocity dispersion in our simulations and have found that its influence on the halo structure is negligible. Using an analytical formalism, we show that halos formed by monolithic collapse will present a significant soft core only when particles have velocity dispersions much larger than the v th of warm particles. Relative to CDM, in a WDM model with R f ≈ 0.15 − 0.20 Mpc (flat cosmology with Ω Λ = h = 0.7) we find that not only the number of satellite galaxies in Milky-Way systems is in better agreement with the observations, but also the concentrations, the Tully-Fisher relation, and the formation epochs of dwarf galaxies.
Monthly Notices of the Royal Astronomical Society, 2021
We study the vertical perturbations in the galactic disc of the Milky Way-size high-resolution hy... more We study the vertical perturbations in the galactic disc of the Milky Way-size high-resolution hydrodynamical cosmological simulation named GARROTXA. We detect phase spirals in the vertical projection Z − VZ of disc’s stellar particles for the first time in this type of simulations. Qualitatively similar structures were detected in the recent Gaia data, and their origin is still under study. In our model the spiral-like structures in the phase space are present in a wide range of times and locations across the disc. By accounting for an evolving mix of stellar populations, we observe that, as seen in the data, the phase spirals are better observed in the range of younger-intermediate star particles. We measure the intensity of the spiral with a Fourier decomposition and find that these structures appear stronger near satellite pericenters. Current dynamical models of the phase spiral considering a single perturber required a mass at least of the order of 1010 M⊙, but all three of ou...
For the past several decades efforts to directly detect dark matter (DM), the particle thought to... more For the past several decades efforts to directly detect dark matter (DM), the particle thought to constitute ∼ 24% of the matter-energy density of the universe have largely
arXiv: Astrophysics of Galaxies, Jan 26, 2017
Two well studied dwarf galaxies -- NGC 3109 and NGC 6822 -- present some of the strongest observa... more Two well studied dwarf galaxies -- NGC 3109 and NGC 6822 -- present some of the strongest observational support for a flat core at the center of galactic dark matter (DM) halos. We use detailed cosmologically motivated numerical models to investigate the systematics and the accuracy of recovering parameters of the galaxies. Some of our models match the observed structure of the two galaxies remarkably well. Our analysis shows that the rotation curves of these two galaxies are instead quite compatible with their DM halos having steep cuspy density profiles. The rotation curves in our models are measured using standard observational techniques. The models reproduce the rotation curves of both galaxies, the disk surface brightness profiles as well as the profile of isophotal ellipticity and position angle. The models are centrally dominated by baryons; however, the dark matter component is globally dominant. The simulated disk mass is marginally consistent with a stellar mass-to-light ...
Assuming the dark matter halo of the Milky Way as a non-spherical potential (i.e. triaxial, prola... more Assuming the dark matter halo of the Milky Way as a non-spherical potential (i.e. triaxial, prolate, oblate), we show how the assembling process of the Milky Way halo, may have left long lasting stellar halo kinematic fossils only due to the shape of the dark matter halo. In contrast with tidal streams, associated with recent satellite accretion events, these stellar kinematic groups will typically show inhomogeneous chemical and stellar population properties. However, they may be dominated by a single accretion event for certain mass assembling histories. If the detection of these peculiar kinematic stellar groups is confirmed, they would be the smoking gun for the predicted triaxiality of dark halos in cosmological galaxy formation scenarios.
D ynam ics ofbarred galaxies:eects ofdisk height
A B ST R A C T W estudy dynam icsofbarsin m odelsofdisk galaxiesem beded in realisticdark m atter... more A B ST R A C T W estudy dynam icsofbarsin m odelsofdisk galaxiesem beded in realisticdark m atter halos.W end that disk thickness plays an im portant,ifnot dom inant,role in the evolution and structureofthebars.W ealsom akeextensivenum ericaltestsofdierent N -body codesused to study bardynam ics.M odelswith thick diskstypically used in this type ofm odeling (height-to-length ratio hz=Rd = 0:2)produce slowly rotating, and very long,bars.In contrast,m ore realistic thin diskswith the sam e param eters asin ourGalaxy (hz=Rd � 0:1)produce barswith norm allength RbarRd,which rotate quickly with the ratio ofthe corotation radius to the bar radius R = 1:2 1:4 com patible with observations.Bars in these m odels do not show a tendency to slow down,and m ay lose aslittle as2-3 percentoftheirangularm om entum due to dynam icalfriction with the dark m atter over cosm ologicaltim e.W e attribute the dierencesbetween the m odelsto a com bined eectofhigh phase-space density and sm allerJeansm assi...
Vertex deviation maps to bracked the Milky Way resonant radius
arXiv: Cosmology and Nongalactic Astrophysics, 2020
Shortly after its discovery, General Relativity (GR) was applied to predict the behavior of our U... more Shortly after its discovery, General Relativity (GR) was applied to predict the behavior of our Universe on the largest scales, and later became the foundation of modern cosmology. Its validity has been verified on a range of scales and environments from the Solar system to merging black holes. However, experimental confirmations of GR on cosmological scales have so far lacked the accuracy one would hope for -- its applications on those scales being largely based on extrapolation and its validity sometimes questioned in the shadow of the unexpected cosmic acceleration. Future astronomical instruments surveying the distribution and evolution of galaxies over substantial portions of the observable Universe, such as the Dark Energy Spectroscopic Instrument (DESI), will be able to measure the fingerprints of gravity and their statistical power will allow strong constraints on alternatives to GR. In this paper, based on a set of $N$-body simulations and mock galaxy catalogs, we study the...
We study the radial acceleration relation (RAR) for early-type galaxies (ETGs) in the SDSS MaNGA ... more We study the radial acceleration relation (RAR) for early-type galaxies (ETGs) in the SDSS MaNGA MPL5 data set. The complete ETG sample show a slightly offset RAR from the relation reported by McGaugh et al. (2016) at the low-acceleration end; we find that the deviation is due to the fact that the slow rotators show a systematically higher acceleration relation than the McGaugh's RAR, while the fast rotators show a consistent acceleration relation to McGaugh's RAR. There is a 1σ significant difference between the acceleration relations of the fast and slow rotators, suggesting that the acceleration relation correlates with the galactic spins, and that the slow rotators may have a different mass distribution compared with fast rotators and late-type galaxies. We suspect that the acceleration relation deviation of slow rotators may be attributed to more galaxy merger events, which would disrupt the original spins and correlated distributions of baryons and dark matter orbits i...
Monthly Notices of the Royal Astronomical Society, 2019
We investigate the dependence of the galaxy–halo connection and galaxy density field in modified ... more We investigate the dependence of the galaxy–halo connection and galaxy density field in modified gravity models using the N-body simulations for f(R) and nDGP models at z = 0. Because of the screening mechanisms employed by these models, chameleon and Vainshtein, haloes are clustered differently in the non-linear regime of structure formation. We quantify their deviations in the galaxy density field from the standard Λ cold dark matter (ΛCDM) model under different environments. We populate galaxies in haloes via the (sub)halo abundance matching. Our main results are as follows: (1) The galaxy–halo connection strongly depends on the gravity model; a maximum variation of ${\sim }40{{\ \rm per\ cent}}$ is observed between halo occupational distribution (HOD) parameters; (2) f(R) gravity models predict an excess of galaxies in low-density environments of ${\sim }10{{\ \rm per\ cent}}$ but predict a deficit of ${\sim }10{{\ \rm per\ cent}}$ at high-density environments for |fR0| = 10−4 a...
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Papers by Octavio Valenzuela