Observatorio Astronomico

Laprida, Argentina

Observatorio Astronomico

Laprida, Argentina
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Ruiz-Lara T.,University of Granada | Ruiz-Lara T.,Institute of Astrophysics of Canarias | Ruiz-Lara T.,University of La Laguna | Perez I.,University of Granada | And 27 more authors.
Astronomy and Astrophysics | Year: 2017

Context. According to numerical simulations, stars are not always kept at their birth galactocentric distances but they have a tendency to migrate. The importance of this radial migration in shaping galactic light distributions is still unclear. However, if radial migration is indeed important, galaxies with different surface brightness (SB) profiles must display differences in their stellar population properties. Aims. We investigate the role of radial migration in the light distribution and radial stellar content by comparing the inner colour, age, and metallicity gradients for galaxies with different SB profiles. We define these inner parts, avoiding the bulge and bar regions and up to around three disc scale lengths (type I, pure exponential) or the break radius (type II, downbending; type III, upbending). Methods. We analysed 214 spiral galaxies from the CALIFA survey covering different SB profiles. We made use of GASP2D and SDSS data to characterise the light distribution and obtain colour profiles of these spiral galaxies. The stellar age and metallicity profiles were computed using a methodology based on full-spectrum fitting techniques (pPXF, GANDALF, and STECKMAP) to the Integral Field Spectroscopic CALIFA data. Results. The distributions of the colour, stellar age, and stellar metallicity gradients in the inner parts for galaxies displaying different SB profiles are unalike as suggested by Kolmogorov-Smirnov and Anderson-Darling tests. We find a trend in which type II galaxies show the steepest profiles of all, type III show the shallowest, and type I display an intermediate behaviour. Conclusions. These results are consistent with a scenario in which radial migration is more efficient for type III galaxies than for type I systems, where type II galaxies present the lowest radial migration efficiency. In such a scenario, radial migration mixes the stellar content, thereby flattening the radial stellar properties and shaping different SB profiles. However, in light of these results we cannot further quantify the importance of radial migration in shaping spiral galaxies, and other processes, such as recent star formation or satellite accretion, might play a role. © ESO, 2017.


Aquilano R.,CONICET | Navone H.,Observatorio Astronomico
Advanced Studies in Theoretical Physics | Year: 2010

We analyze a type of self-gravitating object, described by a soliton to the coupled system of the Einstein equation and a matter field equation. The existence of such objects could have important connotations in astrophysics, specially by high density stars.


Cano-Diaz M.,National Autonomous University of Mexico | Sanchez S.F.,National Autonomous University of Mexico | Zibetti S.,National institute for astrophysics | Ascasibar Y.,Autonomous University of Madrid | And 23 more authors.
Astrophysical Journal Letters | Year: 2016

The "main sequence of galaxies" - defined in terms of the total star formation rate ψ versus the total stellar mass M ∗ - is a well-studied tight relation that has been observed at several wavelengths and at different redshifts. All earlier studies have derived this relation from integrated properties of galaxies. We recover the same relation from an analysis of spatially resolved properties, with integral field spectroscopic (IFS) observations of 306 galaxies from the CALIFA survey. We consider the SFR surface density in units of log(M o yr-1 Kpc-2) and the stellar mass surface density in units of log(M o Kpc-2) in individual spaxels that probe spatial scales of 0.5-1.5 Kpc. This local relation exhibits a high degree of correlation with small scatter (σ = 0.23 dex), irrespective of the dominant ionization source of the host galaxy or its integrated stellar mass. We highlight (i) the integrated star formation main sequence formed by galaxies whose dominant ionization process is related to star formation, for which we find a slope of 0.81 ± 0.02; (ii) for the spatially resolved relation obtained with the spaxel analysis, we find a slope of 0.72 ± 0.04; and (iii) for the integrated main sequence, we also identified a sequence formed by galaxies that are dominated by an old stellar population, which we have called the retired galaxies sequence. © 2016. The American Astronomical Society. All rights reserved..


Piatti A.E.,Institute Astronomia y Fisica del Espacio | Claria J.J.,Observatorio Astronomico | Bica E.,Federal University of Rio Grande do Sul | Geisler D.,University of Concepción | And 3 more authors.
Monthly Notices of the Royal Astronomical Society | Year: 2011

We present CCD photometry in the Washington system C, T1 and T2 passbands down to T1~ 23 in the fields of L3, L28, HW66, L100, HW79, IC1708, L106, L108, L109, NGC643, L112, HW84, HW85 and HW86, 14 Small Magellanic Cloud (SMC) clusters, most of them poorly studied objects. We measured T1 magnitudes and C-T1 and T1-T2 colours for a total of 213516 stars spread throughout cluster areas of 14.7 × 14.7arcmin2 each. We carried out an in-depth analysis of the field star contamination of the colour-magnitude diagrams (CMDs) and statistically cleaned the cluster CMDs. Based on the best fits of isochrones computed by the Padova group to the (T1, C-T1) CMDs, as well as from the δ(T1) index and the standard giant branch procedure, we derived ages and metallicities for the cluster sample. With the exception of IC1708, a relatively metal-poor Hyades-age cluster, the remaining 13 objects are between intermediate and old age (from 1.0 to 6.3Gyr), their [Fe/H] values ranging from -1.4 to -0.7dex. By combining these results with others available in the literature, we compiled a sample of 43 well-known SMC clusters older than 1Gyr, with which we produced a revised age distribution. We found that the present clusters' age distribution reveals two primary excesses of clusters at t~ 2 and 5Gyr, which engraves the SMC with clear signs of enhanced formation episodes at both ages. In addition, we found that from the birth of the SMC cluster system until approximately the first 4Gyr of its lifetime, the cluster formation resembles that of a constant formation rate scenario. © 2011 The Authors. Monthly Notices of the Royal Astronomical Society © 2011 RAS.


Mottola S.,German Aerospace Center | Di Martino M.,National institute for astrophysics | Erikson A.,German Aerospace Center | Gonano-Beurer M.,German Aerospace Center | And 7 more authors.
Astronomical Journal | Year: 2011

We present the results of a Jupiter Trojans' light curve survey aimed at characterizing the rotational properties of Trojans in the approximate size range 60-150km. The survey, which was designed to provide reliable and unbiased estimates of rotation periods and amplitudes, resulted in light curves for a total of 80 objects, 56 of which represent the first determinations published to date and nine of which supersede previously published erroneous values. Our results more than double the size of the existing database of rotational properties of Jovian Trojans in the selected size range. The analysis of the distributions of the rotation periods and light curve amplitudes is the subject of companion papers. © 2011. The American Astronomical Society. All rights reserved.


Minniti D.,University of Santiago de Chile | Hempel M.,University of Santiago de Chile | Toledo I.,University of Santiago de Chile | Ivanov V.D.,European Southern Observatory | And 14 more authors.
Astronomy and Astrophysics | Year: 2011

Context. It is not known how many globular clusters may remain undetected towards the Galactic bulge. Aims. One of the aims of the VISTA Variables in the Via Lactea (VVV) Survey is to accurately measure the physical parameters of the known globular clusters in the inner regions of the Milky Way and search for new ones, hidden in regions of large extinction. Methods. From deep near-infrared images, we derive deep JHKS-band photometry of a region surrounding the known globular cluster UKS 1 and reveal a new low-mass globular cluster candidate that we name VVV CL001. Results. We use the horizontal-branch red clump to measure E(B - V) ∼ 2.2 mag, (m - M)0 = 16.01 mag, and D = 15.9 kpc for the globular cluster UKS 1. On the basis of near-infrared colour - magnitude diagrams, we also find that VVV CL001 has E(B - V) ∼ 2.0, and that it is at least as metal-poor as UKS 1, although its distance remains uncertain. Conclusions. Our finding confirms the previous projection that the central region of the Milky Way harbours more globular clusters. VVV CL001 and UKS 1 are good candidates for a physical cluster binary, but follow-up observations are needed to decide if they are located at the same distance and have similar radial velocities. © 2011 ESO.


Orellana R.B.,National University of La Plata | Orellana R.B.,CONICET | De Biasi M.S.,National University of La Plata | De Biasi M.S.,CONICET | And 3 more authors.
New Astronomy | Year: 2015

We present results of a study that combines photometry and astrometry for the open clusters vdB80, vdB85 and vdB130. We apply a model which analyses the proper motion distribution and the stellar density to find the kinematic parameters and stellar membership in the region of the mentioned open clusters. The astrometric data are obtained from UCAC4 catalogue. For each cluster, we report the centre coordinates, the components of mean proper motion, the angular diameter and the astrometric members. They are: vdB80: α=97°.73938±0°.00846,δ=-9°.66953±0°.01177,μαcosδ=-2.13±0.47mas/yr,μδ=-0.95±0.47mas/yr,12′, 15 members; vdB85: α=101°.71670±0°.00808,δ=1°.34392±0°.01253,μαcosδ=0.89±0.43mas/yr,μδ=3.24±0.43mas/yr,8′, 9 members; vdB130: α=304°.44001±0°.01407,δ=39°.32745±0°.00726,μαcosδ=-4.14±0.25mas/yr,μδ=-5.15±0.25mas/yr,9′, 9 members. We analyse the incidence of the proper motion errors in the determination of the cluster parameters and of the stellar membership and find that they are not significantly changed. We finally compare the astrometric members with the photometric ones given in the literature. © 2014 Elsevier B.V. All rights reserved.


Calderon J.H.,Observatorio Astronomico | Calderon J.H.,CONICET | Bustos Fierro I.H.,Observatorio Astronomico
Revista Mexicana de Astronomia y Astrofisica: Serie de Conferencias | Year: 2014

In this paper we present preliminary results from the measurement and analysis of images of the ecliptic zone obtained with MegaCam at Canada-France-Hawaii Telescope (CFHT) located at Mauna Kea (Hawaii). We are evaluating the feasibility of constructing an astrometric and photometric catalogue with all the astronomical sources identified on those images. We comment and discuss the criteria and procedures for the identification of sources, the photometric reduction and their classification as stellar or extended objects.


Bustos Fierro I.H.,Observatorio Astronomico | Calderon J.H.,Observatorio Astronomico | Calderon J.H.,CONICET
Revista Mexicana de Astronomia y Astrofisica: Serie de Conferencias | Year: 2014

In this paper we present the evaluations of the astrometric reduction of CFHT images that are intended to be used for the construction of a deep ecliptic catalogue, using UCAC3 as reference catalogue. We find that the average centering error for star-like objects is 0.012 pixel (2.2 mas), but for extended objects it is 0.037 pixel (6.9 mas). By comparing measurements with two different filters a strong chromatic aberration was detected, that was modeled and corrected. After that correction the differences between instrumental coordinates in both filters are (-7± 11) mas in X and (-1 ± 12) mas in Y and no systematic pattern is apparent. The differences between celestial coordinates obtained with the two filters are 15 mas in αcos(δ) and 26 mas in δ.


Orellana R.B.,National University of La Plata | Orellana R.B.,CONICET | De Biasi M.S.,National University of La Plata | De Biasi M.S.,CONICET | And 2 more authors.
Astronomy and Astrophysics | Year: 2010

Aims. Based on stellar positions and proper motions, we aim to re-analyse the region of the controversial open cluster Collinder 132. Methods. We have developed a model which analyses the proper motion distribution and the stellar density to find moving groups. The astrometric data were obtained from four Carte du Ciel (CdC) and one Astrogaphic Catalogue (AC) plates of the Córdoba Astronomical Observatory collection (Argentina). Results. We detected an open cluster from the field stars and calculated the mean proper motion and the membership probabilities of the region's stars. We report new coordinates of its centre αc = 108\fdg347, δc = -31\fdg011, the components of mean proper motion μ αcosδ = -2.62±0.44 mas/yr, μδ = 4.79±0.88 mas/yr. Thirteen stars are astrometric members giving a value of 20' for the cluster angular diameter. Six stars fulfil the astrometric and photometric criteria for being cluster members and locate the cluster at 360 pc from the Sun. We propose a simple model for the analysis of the proper motion distribution of an association. We report the components of the association mean proper motion μαcosδ = -1.38±0.14 mas/yr, μδ = 2.26±0.16 mas/yr. We found 149 astrometric members, 11 of which have reliable photometric data that locate them betweeen 417 and 660 pc from the Sun. © 2010 ESO.

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