M. G. Abadi

Universidad Nacional de Córdoba

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D. G. Lambas

Universidad Nacional de Córdoba

Julio F. Navarro

University of Victoria

Laura V. Sales

University of California, Riverside

Matthias Steinmetz

Leibniz Institute for Astrophysics Potsdam

P. B. Tissera

Universidad Andrés Bello

H. Muriel

Universidad Nacional de Córdoba

I. Ferrero

University of Oslo

José A. Benavides

University of California, Riverside

S. A. Cora

Universidad Nacional de La Plata

F. Ramos

Universidad Nacional de Córdoba

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Centre National de la Recherche Scientifique

200

Max Planck Society

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Consejo Nacional de Investigaciones Científicas y Técnicas

Purple Mountain Observatory

Observatoire de Paris

Université Paris Cité

Sorbonne Université

Max Planck Institute for Astronomy

Argentine National Observatory

Australian National University

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CHAPTER XI: INDIVIDUAL MEMBERSHIP

Proceedings of the International Astronomical Union (2007)

M. G. Abadi E. Agüero A. V. Ahumada J. A. Ahumada M. V. Alonso

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10.1017/s1743921308024393

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Citations (1)

THE EFFECT OF RADIAL MIGRATION ON GALACTIC DISKS

The Astrophysical Journal (2014)

Carlos Vera-Ciro Elena D’Onghia Julio F. Navarro M. G. Abadi

We study the radial migration of stars driven by recurring multi-arm spiral features in an exponential disk embedded in a dark matter halo. The spiral perturbations redistribute angular momentum within the disk and lead to substantial radial displacements of individual stars, in a manner that largely preserves the circularity of their orbits and that results, after 5 Gyr (∼40 full rotations at the disk scale length), in little radial heating and no appreciable changes to the vertical or radial structure of the disk. Our results clarify a number of issues related to the spatial distribution and kinematics of migrators. In particular, we find that migrators are a heavily biased subset of stars with preferentially low vertical velocity dispersions. This "provenance bias" for migrators is not surprising in hindsight, for stars with small vertical excursions spend more time near the disk plane, and thus respond more readily to non-axisymmetric perturbations. We also find that the vertical velocity dispersion of outward migrators always decreases, whereas the opposite holds for inward migrators. To first order, newly arrived migrators simply replace stars that have migrated off to other radii, thus inheriting the vertical bias of the latter. Extreme migrators might therefore be recognized, if present, by the unexpectedly small amplitude of their vertical excursions. Our results show that migration, understood as changes in angular momentum that preserve circularity, can strongly affect the thin disk, but cast doubts on models that envision the Galactic thick disk as a relic of radial migration.

Radial velocity

10.1088/0004-637x/794/2/173

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Citations (124)

Simulations of Galaxy Formation in a Λ Cold Dark Matter Universe. II. The Fine Structure of Simulated Galactic Disks

The Astrophysical Journal (2003)

M. G. Abadi Julio F. Navarro Matthias Steinmetz V. R. Eke

We present a detailed analysis of the dynamical properties of a simulated disk galaxy assembled hierarchically in the Lambda CDM cosmogony. At z=0, two distinct dynamical components are identified on the basis of the orbital parameters of stars in the galaxy: a slowly rotating, centrally concentrated spheroid and a disk-like component largely supported by rotation. These components are also recognized in the surface brightness profile of the galaxy, which can be very well approximated by the superposition of an R^{1/4} spheroid and an exponential disk. However, neither does the dynamically-identified spheroid follow de Vaucouleurs' law nor is the disk purely exponential, a resultwhich calls for caution when estimating the importance of the disk from traditional photometric decomposition techniques. The disk may be further decomposed into a thin, dynamically cold component with stars on nearly circularorbits and a hotter, thicker component with orbital parameters transitional between the thin disk and the spheroid. The spheroid is old, and has essentiallyno stars younger than the time elapsed since the last major accretion event ~8 Gyr ago. The majority of thin disk stars, form after the merging activity is over, although a significant fraction ~15% of thin-disk stars are old enough to predate the last major merger event. This unexpected population of old disk stars consists mainly of the tidal debris of satellites whose orbital plane was coincident with the disk and whose orbits were circularized by dynamical friction prior to full disruption. Our results highlight the role of satellite accretion events in shaping the disk and the spheroidal component and reveal some of the clues to the assembly process of a galaxy preserved in the detailed dynamics of old stellar populations.

Thick disk

Thin disk

10.1086/378316

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Age and metallicity gradients in simulated galaxies of the Local Group

Boletin de la Asociacion Argentina de Astronomia La Plata Argentina (2021)

Ornela F Marioni M. G. Abadi

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LCDM predictions for galaxy halos and visible components

Matthias Steinmetz M. G. Abadi V. R. Eke Franziska Köckert Laura V. Sales

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Simulations of Galaxy Formation in a Λ Cold Dark Matter Universe. I. Dynamical and Photometric Properties of a Simulated Disk Galaxy

The Astrophysical Journal (2003)

M. G. Abadi Julio F. Navarro Matthias Steinmetz V. R. Eke

We present a detailed analysis of the dynamical and photometric properties of a disk galaxy simulated in the Λ cold dark matter (ΛCDM) cosmogony. The galaxy is assembled through a number of high-redshift mergers followed by a period of quiescent accretion after z ~ 1 that lead to the formation of two distinct dynamical components: a spheroid of mostly old stars and a rotationally supported disk of younger stars. The surface brightness profile is very well approximated by the superposition of an R1/4 spheroid and an exponential disk. Each photometric component contributes a similar fraction of the total luminosity of the system, although less than a quarter of the stars form after the last merger episode at z ~ 1. In the optical bands the surface brightness profile is remarkably similar to that of Sab galaxy UGC 615, but the simulated galaxy rotates significantly faster and has a declining rotation curve dominated by the spheroid near the center. The decline in circular velocity is at odds with observation and results from the high concentration of the dark matter and baryonic components, as well as from the relatively high mass-to-light ratio of the stars in the simulation. The simulated galaxy lies ~1 mag off the I-band Tully-Fisher relation of late-type spirals but seems to be in reasonable agreement with Tully-Fisher data on S0 galaxies. In agreement with previous simulation work, the angular momentum of the luminous component is an order of magnitude lower than that of late-type spirals of similar rotation speed. This again reflects the dominance of the slowly rotating, dense spheroidal component, to which most discrepancies with observation may be traced. On its own, the disk component has properties rather similar to those of late-type spirals: its luminosity, its exponential scale length, and its colors are all comparable to those of galaxy disks of similar rotation speed. This suggests that a different form of feedback than adopted here is required to inhibit the efficient collapse and cooling of gas at high redshift that leads to the formation of the spheroid. Reconciling, without fine-tuning, the properties of disk galaxies with the early collapse and high merging rates characteristic of hierarchical scenarios such as ΛCDM remains a challenging, yet so far elusive, proposition.

Cold dark matter

10.1086/375512

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Citations (379)

Correlation Length of X‐Ray–Brightest Abell Clusters

The Astrophysical Journal (1998)

M. G. Abadi D. G. Lambas H. Muriel

We compute the cluster auto-correlation function $ξ_{cc}(r)$ of an X-ray flux limited sample of Abell clusters (XBACs, \cite{ebe}). For the total XBACs sample we find a power-law fit $ξ_{cc}=(r/r_0)^γ$ with $r_0=21.1$ Mpc h$^{-1}$and $γ=-1.9$ consistent with the results of $R \ge 1 $ Abell clusters. We also analyze $ξ_{cc}(r)$ for subsamples defined by different X-ray luminosity thresholds where we find a weak tendency of larger values of $r_0$ with increasing X-ray luminosity although with a low statistical significance. In the different subsamples analyzed we find $21 < r_0 < 35 $ Mpc h$^{-1}$ and $-1.9< γ< -1.6$. Our analysis suggests that cluster X-ray luminosities may be used for a reliable confrontation of cluster spatial distribution properties in models and observations.

10.1086/306342

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Pieces of the puzzle: ancient substructure in the Galactic disc

Monthly Notices of the Royal Astronomical Society (2005)

A. Helmi Julio F. Navarro B. Nordström Johan Holmberg M. G. Abadi

We search for signatures of past accretion events in the Milky Way in the recently published catalogue by Nordström et al., containing accurate spatial and kinematic information as well as metallicities for 13 240 nearby stars. To optimize our strategy, we use numerical simulations and characterize the properties of the debris from disrupted satellites. We find that stars with a common progenitor should show distinct correlations between their orbital parameters; in particular, between the apocentre (A) and pericentre (P), as well as their z-angular momentum (Lz). In the APL space, such stars are expected to cluster around regions of roughly constant eccentricity.

Substructure

Eccentricity (behavior)

Stellar dynamics

10.1111/j.1365-2966.2005.09818.x

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Citations (160)

A simple model for dissipative galaxy formation

The Astrophysical Journal (1990)

M. G. Abadi D. G. Lambas M. B. Mosconi

view Abstract Citations (6) References (27) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS A Simple Model for Dissipative Galaxy Formation Abadi, Mario G. ; Garcia Lambas, Diego ; Mosconi, Mirta B. Abstract Numerical experiments of the dynamics of a distribution of interacting gas clouds in a protogalactic potential well are analyzed. Dissipation of energy by means of inelastic cloud-cloud collisions produce, after a few characteristic times, a strong flattening (5:1), and a large ratio of rotational versus total kinetic energy for the clouds with several inelastic collisions. The adimensional spin parameter 位 = J |E|^1/2^G^-1^M^-5/2^ reaches high values (位 >= 0.25) for this highly dissipative component, in contrast with 位 ~ 0.07, for those clouds that never collided. After the collapse, the resulting systems live in a "long" stationary state, where the collisions gradually increase the number of "star clusters," made up of gas clouds with a threshold condition in the number of inelastic collisions. Gasdynamical effects involving energy dissipation and relaxation processes play fundamental roles in the galaxy formation model depicted here. We conclude from our experiments that accretion from a gaseous medium surrounding a galactic potential well can account for many desirable properties of a model of disk galaxy formation. Publication: The Astrophysical Journal Pub Date: September 1990 DOI: 10.1086/169126 Bibcode: 1990ApJ...360..343A Keywords: Astronomical Models; Galactic Evolution; Galactic Structure; Molecular Clouds; Cosmology; Spatial Distribution; Star Formation; Universe; Astrophysics; GALAXIES: FORMATION; GALAXIES: STRUCTURE full text sources ADS |

10.1086/169126

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Tidal stripping of globular clusters in a simulated galaxy cluster

arXiv (Cornell University) (2015)

Felipe Ramos Valeria Coenda H. Muriel M. G. Abadi

Using a cosmological N-body numerical simulation of the formation of a galaxy cluster- sized halo, we analyze the temporal evolution of its globular cluster population. We follow the dynamical evolution of 38 galactic dark matter halos orbiting in a galaxy cluster that at redshift z=0 has a virial mass of 1.71 * 10 ^14 Msol h^-1. In order to mimic both "blue" and "red" populations of globular clusters, for each galactic halo we select two different sets of particles at high redshift (z ~ 1), constrained by the condition that, at redshift z=0, their average radial density profiles are similar to the observed profiles. As expected, the general galaxy cluster tidal field removes a significant fraction of the globular cluster populations to feed the intracluster population. On average, halos lost approximately 16% and 29% of their initial red and blue globular cluster populations, respectively. Our results suggest that these fractions strongly depend on the orbital trajectory of the galactic halo, specifically on the number of orbits and on the minimum pericentric distance to the galaxy cluster center that the halo has had. At a given time, these fractions also depend on the current clustercentric distance, just as observations show that the specific frequencyof globular clusters S_N depends on their clustercentric distance.

10.48550/arxiv.1505.05506

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