O. Valenzuela - Profile on Academia.edu (original) (raw)

Papers by O. Valenzuela

arXiv: Astrophysics of Galaxies, 2017

We present here the characterization of the main properties of a sample of 98 AGN host galaxies, ... more We present here the characterization of the main properties of a sample of 98 AGN host galaxies, both type-II and type-I, in comparison with those of about 2700 non-active galaxies observed by the MaNGA survey. We found that AGN hosts are morphologically early-type or early-spirals. For a given morphology AGN hosts are, in average, more massive, more compact, more central peaked and rather pressurethan rotational-supported systems. We confirm previous results indicating that AGN hosts are located in the intermediate/transition region between star-forming and non-star-forming galaxies (i.e., the so-called green valley), both in the ColorMagnitude and the star formation main sequence diagrams. Taking into account their relative distribution in terms of the stellar metallicity and oxygen gas abundance and a rough estimation of their molecular gas content, we consider that these galaxies are in the process of halting/quenching the star formation, in an actual transition between both gro...

The Astrophysical Journal, 2016

We report on detection, from observations obtained with the APOGEE spectroscopic survey, of a met... more We report on detection, from observations obtained with the APOGEE spectroscopic survey, of a metal-poor ([Fe/H] = −1.3 dex) field giant star with an extreme Mg-Al abundance ratio ([Mg/Fe] = −0.31 dex; [Al/Fe] = 1.49 dex). Such low Mg/Al ratios are seen only among the second-generation population of globular clusters, and are not present among Galactic disk field stars. The light element abundances of this star, 2M16011638-1201525, suggest that it could have been born in a globular cluster. We explore several origin scenarios, in particular studying the orbit of the star to check the probability of it being kinematically related to known globular clusters. We performed simple orbital integrations assuming the estimated distance of 2M16011638-1201525 and the available six-dimensional phase-space coordinates of 63 globular clusters, looking for close encounters in the past with a minimum distance approach within the tidal radius of each cluster. We found a very low probability that 2M16011638-1201525 was ejected from most globular clusters; however, we note that the best progenitor candidate to host this star is globular cluster ω Centauri (NGC 5139). Our dynamical investigation demonstrates that 2M16011638-1201525 reaches a distance |Z max | < 3 kpc from the Galactic plane and a minimum and maximum approach to the Galactic center of R min < 0.62 kpc and R max < 7.26 kpc in an eccentric (e ∼ 0.53) and retrograde orbit. Since the extreme chemical anomaly of 2M16011638-1201525 has also been observed in halo field stars, this object could also be considered a halo contaminant, likely been ejected into the Milky Way disk from the halo. We conclude that, 2M16011638-20152 is also kinematically consistent with the disk but chemically consistent with halo field stars.

Optical and near-infrared morphology of the barred galaxy NGC 3367

Proceedings of The International Astronomical Union, 2009

The Astrophysical Journal, 2002

A series of high-resolution numerical simulations were performed to study the structure and subst... more A series of high-resolution numerical simulations were performed to study the structure and substructure of Milky Way (MW)-and cluster-sized halos in a Λ−Cold Dark Matter (CDM) cosmology with self-interacting (SI) dark particles. The cross section per unit of particle mass has the form σ DM = σ 0 (1/v 100) α , where σ 0 is a constant in units of cm 2 gr −1 and v 100 is the relative velocity in units of 100 kms −1. Different values for σ 0 with α = 0 or 1 were used. For small values of σ DM = const. (∼ < 0.5, α = 0), the core density of the halos at z = 0 is typically higher at a given mass for lower values of σ 0 or, at a given σ 0 , for lower masses. For values of σ 0 as high as 3.0, both cluster-and MW-sized halos may undergo the gravothermal catastrophe before z = 0. The core expansion occurs in a stable regime because the heat capacity, C, is positive in the center. After the maximum expansion, the isothermal core is hotter than the periphery and C < 0. Then, the gravothermal catastrophe triggers. The instability onset can be delayed by both the dynamical heating of the halo by major mergers and the interaction of cool particles with the hot environment of a host halo. When α = 1, the core density of cluster-and MW-sized halos is similar. Using σ DM = 0.5 − 1.0 (1/v 100), our predictions agree with the central densities and the core scaling laws of halos both inferred from the observations of dwarf and low surface brightness galaxies and clusters of galaxies. Regarding the cumulative v max −function of subhalos within MW-sized halos, when (σ 0 , α) = (0.1,0.0), (0.5,0.0) or (0.5,1.0) it agrees roughly with observations (luminous satellites) for v max ∼ > 30kms −1 , while at v max = 20kms −1 the functions are already a factor 5-8 higher, similar to the CDM predictions. For (σ 0 , α) = (1.0,1.0), this function lies above the corresponding CDM function. The structure and number of subhalos are affected by the scattering properties of the host halo rather than by those of the subhalos. The halos with SI have more specific angular momentum at a given mass shell and are rounder than their CDM counterparts. However, the angular momentum excess w.r.t. CDM is small. We conclude that the introduction of SI particles with σ DM ∝ 1/v 100 may remedy the cuspy core problem of the CDM cosmogony, at the same time keeping a subhalo population similar to that of the CDM halos.

The Astrophysical Journal, 2010

We present numerical simulations aimed at exploring the effects of varying the sub-grid physics p... more We present numerical simulations aimed at exploring the effects of varying the sub-grid physics parameters on the evolution and the properties of the galaxy formed in a low-mass dark matter halo (∼ 7 × 10 10 h −1 M ⊙ at redshift z = 0). The simulations are run within a cosmological setting with a nominal resolution of 218 pc comoving and are stopped at z = 0.43. For simulations that cannot resolve individual molecular clouds, we propose the criterion that the threshold density for star formation, n SF , should be chosen such that the column density of the star-forming cells equals the threshold value for molecule formation, N ∼ 10 21 cm −2 , or ∼ 8 M ⊙ pc −2. In all of our simulations, an extended old/intermediate-age stellar halo and a more compact younger stellar disk are formed, and in most cases, the halo's specific angular momentum is slightly larger than that of the galaxy, and sensitive to the SF/feedback parameters. We found that a non negligible fraction of the halo stars are formed in situ in a spheroidal distribution. Changes in the sub-grid physics parameters affect significantly and in a complex way the evolution and properties of the galaxy: (i) Lower threshold densities n SF produce larger stellar effective radii R e , less peaked circular velocity curves V c (R), and greater amounts of low-density and hot gas in the disk mid-plane; (ii) When stellar feedback is modeled by temporarily switching off radiative cooling in the star forming regions, R e increases (by a factor of ∼ 2 in our particular model), the circular velocity curve becomes flatter, and a complex multiphase gaseous disk structure develops; (iii) A more efficient local conversion of gas mass to stars, measured by a stellar particle mass distribution biased toward larger values, increases the strength of the feedback energy injection-driving outflows and inducing burstier SF histories; iv) If feedback is too strong, gas loss by galactic outflows-which are easier to produce in low-mass galaxiesinterrupts SF, whose history becomes episodic; v) In all cases, the surface SF rate versus the gas surface density correlation is steeper than the Kennicutt law but in agreement with observations in low-surface brightness galaxies. The simulations exhibit two important shortcomings: the baryon fractions are higher, and the specific SF rates are much smaller, than observationally inferred values for redshifts ∼ 0.4 − 1. These shortcomings pose a major challenge to the SF/feedback physics commonly applied in the ΛCDM-based galaxy formation simulations.

Monthly Notices of the Royal Astronomical Society, 2011

We study the spiral arm influence on the solar neighbourhood stellar kinematics. As the nature of... more We study the spiral arm influence on the solar neighbourhood stellar kinematics. As the nature of the Milky Way (MW) spiral arms is not completely determined, we study two models: the Tight-Winding Approximation (TWA) model, which represents a local approximation, and a model with self-consistent material arms named sPiral arms potEntial foRmed by obLAte Spheroids (PERLAS). This is a mass distribution with more abrupt gravitational forces. We perform test particle simulations after tuning the two models to the observational range for the MW spiral arm properties. We find that some of the currently observed MW spiral arm properties are not in obvious agreement with the TWA model. We explore the effects of the arm properties and find that a significant region of the allowed parameter space favours the appearance of kinematic groups. The velocity distribution is mostly sensitive to the relative spiral arm phase and pattern speed. In all cases the arms induce strong kinematic imprints for pattern speeds around 17 km s −1 kpc −1 (close to the 4:1 inner resonance) but no substructure is induced close to corotation. The groups change significantly if one moves only ∼0.6 kpc in galactocentric radius, but ∼2 kpc in azimuth. The appearance time of each group is different, ranging from 0 to more than 1 Gyr. Recent spiral arms can produce strong kinematic structures. The stellar response to the two potential models is significantly different near the Sun, both in density and in kinematics. The PERLAS model triggers more substructure for a larger range of pattern speed values. The kinematic groups can be used to reduce the current uncertainty about the MW spiral structure and to test whether this follows the TWA. However, groups such as the observed ones in the solar vicinity can be reproduced by different parameter combinations. Data from velocity distributions at larger distances are needed for a definitive constraint.

The Astronomical Journal, 2013

We present the result of an extensive search for non-axisymmetric structures in the dwarf satelli... more We present the result of an extensive search for non-axisymmetric structures in the dwarf satellite galaxy of M81: NGC 2976, using multiwavelength archival observations. The galaxy is known to present kinematic evidence for a bysimmetric distortion (Spekkens & Sellwood 2007; Sellwood & Sánchez 2010; Adams et al. 2011) however the stellar bar presence is controversial. This controversy motivated the possible interpretation of NGC 2976 presenting an elliptical disk triggered by a prolate dark matter halo (Simon et al. 2003; Kazantzidis et al. 2010a). We applied diagnostics used in spiral galaxies in order to detect stellar bars or spiral arms. The m=2 fourier phase has a jump around 60 arcsecs consistent with a central bar and bisymmetric arms. The CO, 3.6 µ surface brightness and the dust lanes are consistent with a gas rich central bar and possibly with gaseous spiral arms. The barlike feature is close to 20 degrees offset the disc position angle, in agreement with kinematic estimations. The kinematic jumps related with the dust lanes suggest that the bar perturbation in the disk kinematics is non-negligible and the reported noncircular motions, the central gas excess and the nuclear X-ray source (AGN/Starburst) might be produced by the central bar. SPH simulations of disks inside triaxial dark halos suggest that the two symmetric spots at 130 arcsecs and the narrow arms may be produced by gas at turning points in an elliptical disk, alternatively the potential ellipticity can be originated by tidally induced strong stellar bar/arms, in both cases rotation curve interpretation is importantly biased. The M81 group is a natural candidate to trigger the bisymmetric distortion and the related evolution as suggested by the HI tidal bridge detected by Chynoweth et al. (2008). We conclude that both mechanisms, the gas rich bar and spiral arms triggered by environment (tidal stirring), and primordial halo triaxiality, can explain most of NGC 2976 non-circular motions, mass redistribution and nuclear activity. Distinguishing between them requires detailed modeling of environmental effects. A similar analysis like ours may reveal such kind of structures in other nearby dwarf satellite galaxies, if this is confirmed, the same evolutionary scenario will be applicable to them. This implies biases constraining their dark matter distribution and also making comparison against theoretical predictions for isolated galaxies.

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...

OUP accepted manuscript

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...

It was argued in the past that bulges of galaxies cannot be formed through collisionless secular ... more It was argued in the past that bulges of galaxies cannot be formed through collisionless secular evolution because that would violate constraints on the phase-space density: the phase-space density in bulges is several times larger than in the inner parts of discs. We show that these arguments against secular evolution are not correct. Observations give estimates of the coarse-grained phase-space densities of galaxies, f ′ = ρs/σRσφσz, where ρs is stellar density and σR, σφ, σz are the radial, tangential, and vertical rms velocities of stars. Using high-resolution N-body simulations, we study the evolution of f ′ in discs of Galaxy-size models. During the secular evolution, the discs, which are embedded in live Cold Dark Matter haloes, form a bar and then a thick, dynamically hot, central mass concentration. In the course of evolution f ′ declines at all radii, not just in the central region. The decline is different in different parts of the disc. In the inner disc, f ′ (R) develop...

We study the phase space available to the local stellar distribution using a Galactic potential c... more We study the phase space available to the local stellar distribution using a Galactic potential consistent with several recent observational constraints. We find that the induced phase space structure has several observable consequences. The spiral arm contribution to the kinematic structure in the solar neighborhood may be as important as the one produced by the Galactic bar. We suggest that some of the stellar kinematic groups in the solar neighborhood, like the Hercules structure and the kinematic branches, can be created by the dynamical resonances of self-gravitating spiral arms and not exclusively by the Galactic bar. A structure coincident with the Arcturus kinematic group is developed when a hot stellar disk population is considered, which introduces a new perspective on the interpretation of its extragalactic origin. A bar-related resonant mechanism can modify this kinematic structure. We show that particles in the dark matter disk-like structure predicted by recent LCDM ga...

Revista Mexicana De Astronomia Y Astrofisica, 2008

Resumen en: We have initiated a project that aims to revise the robustness of the suggestions of ... more Resumen en: We have initiated a project that aims to revise the robustness of the suggestions of the dearth of dark matter in the central regions of barred galaxies ...

We explore the possible constraints to the dark matter (DM) mass power spectrum amplitude at sub-... more We explore the possible constraints to the dark matter (DM) mass power spectrum amplitude at sub-galactic scales, with the aim to test the properties of DM particle candidates. We present preliminary results discussing the sensitivity of Solar System dynamics and dSph’s wide binaries abundance to the small scale DM distribution. We also discuss possible future avenues.

Journal of Cosmology and Astroparticle Physics, 2021

We explore two possible scenarios to explain the observed γ-ray emission associated with the atyp... more We explore two possible scenarios to explain the observed γ-ray emission associated with the atypical globular cluster ω-Centauri: emission from millisecond pulsars (MSP) and dark matter (DM) annihilation. In the first case the total number of MSPs needed to produce the γ-ray flux is compatible with the known (but not confirmed) MSP candidates observed in X-rays. A DM interpretation is motivated by the possibility of ω-Centauri being the remnant core of an ancient dwarf galaxy hosting a surviving DM component. At least two annihilation channels, light quarks and muons, can plausibly produce the observed γ-ray spectrum. We outline constraints on the parameter space of DM mass versus the product of the pair-annihilation cross section and integrated squared DM density (the so-called J-factor ). We translate upper limits on the dark matter content of ω-Centauri into lower limits on the annihilation cross section. This shows s-wave annihilation into muons to be inconsistent with CMB observations, while a small window for annihilation into light quarks is allowed. Further analysis of ω-Centauri's internal kinematics, and/or additional information on the resident MSP population will yield much stronger constraints and shed light about the origin of this otherwise mysterious γ-ray source.

The Astrophysical Journal Supplement Series, 2017

The fourth generation of the Sloan Digital Sky Survey (SDSS-IV) began observations in July 2014. ... more The fourth generation of the Sloan Digital Sky Survey (SDSS-IV) began observations in July 2014. It pursues three core programs: the Apache Point Observatory Galactic Evolution Experiment 2 (APOGEE-2), Mapping Nearby Galaxies at APO (MaNGA), and the Extended Baryon Oscillation Spectroscopic Survey (eBOSS). As well as its core program, eBOSS contains two major subprograms: the Time Domain Spectroscopic Survey (TDSS) and the SPectroscopic IDentification of ERosita Sources (SPIDERS). This paper describes the first data release from SDSS-IV, Data Release 13 (DR13). DR13 makes publicly available the first 1390 spatially resolved integral field unit observations of nearby galaxies from MaNGA. It includes new observations from eBOSS, completing the Sloan Extended QUasar, Emission-line galaxy, Luminous red galaxy Survey (SEQUELS), which also targeted variability-selected objects and X-ray selected objects. DR13 includes new reductions of the SDSS-III BOSS data, improving the spectrophotometric calibration and redshift classification, and new reductions of the SDSS-III APOGEE-1 data, improving stellar parameters for dwarf stars and cooler stars. DR13 provides more robust and precise photometric calibrations. Value-added target catalogs relevant for eBOSS, TDSS, and SPIDERS and an updated red-clump catalog for APOGEE are also available. This paper describes the location and format of the data and provides references to important technical papers. The SDSS website, www.sdss.org, provides links to the data, tutorials, examples of data access, and extensive documentation of the reduction and analysis procedures. DR13 is the first of a scheduled set that will contain new data and analyses from the planned ∼ 6-year operations of SDSS-IV.

Monthly Notices of the Royal Astronomical Society, 2016

The most accurate 6D phase-space information from the Radial Velocity Experiment (RAVE) was used ... more The most accurate 6D phase-space information from the Radial Velocity Experiment (RAVE) was used to integrate the orbits of 105 stars around the galactic globular cluster 47 Tucanae, to look for close encounters between them in the past, with a minimum distance approach less than the cluster tidal radius. The stars are currently over the distance range 3.0 kpc < d < 5.5 kpc. Using the uncertainties in the current position and velocity vector for both, star and cluster, 105 pairs of star-cluster orbits were generated in a Monte Carlo numerical scheme, integrated over 2 Gyr and considering an axisymmetric and non-axisymmetric Milky-Way-like Galactic potential, respectively. In this scheme, we identified 20 potential cluster members that had close encounters with the globular cluster 47 Tucanae, all of which have a relative velocity distribution (V rel) less than 200 km s −1 at the minimum distance approach. Among these potential members, 9 had close encounters with the cluster with velocities less than the escape velocity of 47 Tucanae, therefore a scenario of tidal stripping seems likely. These stars have been classified with a 93% confidence level, leading to the identification of extratidal cluster stars. For the other 11 stars, V rel exceeds the escape velocity of the cluster, therefore they were likely ejected or are unassociated interlopers.

One of the most intriguing features in the solar neighborhood stellar velocity distribution are t... more One of the most intriguing features in the solar neighborhood stellar velocity distribution are the so called moving groups. These groups are stellar streams observed as overdensities in the velocity space, crossing the region nearby the Sun. At 140 years of their discovery, the understanding of the origin of these kinematic structures is still far from complete. Several scenarios for

Astronomy & Astrophysics, 2015

We present a survey for RR Lyrae stars in an area of 50 deg 2 around the globular cluster ω Centa... more We present a survey for RR Lyrae stars in an area of 50 deg 2 around the globular cluster ω Centauri, aimed to detect debris material from the alleged progenitor galaxy of the cluster. We detected 48 RR Lyrae stars of which only 11 have been previously reported. Ten among the eleven previously known stars were found inside the tidal radius of the cluster. The rest were located outside the tidal radius up to distances of ∼ 6 degrees from the center of the cluster. Several of those stars are located at distances similar to that of ω Centauri. We investigated the probability that those stars may have been stripped off the cluster by studying their properties (mean periods), calculating the expected halo/thick disk population of RR Lyrae stars in this part of the sky, analyzing the radial velocity of a sub-sample of the RR Lyrae stars, and finally, studying the probable orbits of this sub-sample around the Galaxy. None of these investigations support the scenario that there is significant tidal debris around ω Centauri, confirming previous studies in the region. It is puzzling that tidal debris have been found elsewhere but not near the cluster itself.

The Astrophysical Journal, 2004

We study properties of dark matter halos at high redshifts z = 2-10 for a vast range of masses wi... more We study properties of dark matter halos at high redshifts z = 2-10 for a vast range of masses with the emphasis on dwarf halos with masses 10 7 -10 9 h -1 M ⊙ . We find that the density profiles of relaxed dwarf halos are well fitted by the NFW profile and do not have cores. We compute the halo mass function and the halo spin parameter distribution and find that the former is very well reproduced by the Sheth & Tormen model while the latter is well fitted by a lognormal distribution with λ 0 = 0.042 and σ λ = 0.63. We estimate the distribution of concentrations for halos in mass range that covers six orders of magnitude from 10 7 h -1 M ⊙ to 10 13 h -1 M ⊙ , and find that the data are well reproduced by the model of Bullock et al. The extrapolation of our results to z = 0 predicts that present-day isolated dwarf halos should have a very large median concentration of ∼ 35. We measure the subhalo circular velocity functions for halos with masses that range from 4.6 × 10 9 h -1 M ⊙ to 10 13 h -1 M ⊙ and find that they are similar when normalized to the circular velocity of the parent halo. Dwarf halos studied in this paper are many orders of magnitude smaller than well-studied cluster-and Milky Way-sized halos. Yet, in all respects the dwarfs are just down-scaled versions of the large halos. They are cuspy and, as expected, more concentrated. They have the same spin parameter distribution and follow the same mass function that was measured for large halos.

The Astronomical Journal, 2011

NGC 3367 is a nearby isolated active galaxy that shows a radio jet, a strong bar and evidence of ... more NGC 3367 is a nearby isolated active galaxy that shows a radio jet, a strong bar and evidence of lopsidedness. We present a quantitative analysis of the stellar and gaseous structure of the galaxy disk and a search for evidence of recent interaction based on new U BV RI Hα and JHK images and on archival Hα Fabry-Perot and HI VLA data. From a coupled 1D/2D GALFIT bulge/bar/disk decomposition an (B/D ∼ 0.07-0.1) exponential pseudobulge is inferred in all the observed bands. A N IR estimate of the bar strength < Q max