Examinando por Autor "Gómez, Matías"
Mostrando 1 - 9 de 9
Resultados por página
Opciones de ordenación
Ítem Confirmation of a New Metal-poor Globular Cluster in the Galactic Bulge(Institute of Physics Publishing, 2018-10) Minniti, Dante; Schlafly E.F.; Palma, Tali; Clariá, Juan J.; Hempel, Maren; Alonso-García, Javier; Bica, Eduardo; Bonatto, Charles; Braga, Vittorio F.; Clementini, Gisella; Garofalo, Alessia; Gómez, Matías; Ivanov, Valentin D.; Lucas, Phillip W.; Pullen, Joyce; Saito, Roberto K.; Smith, Leigh C.We use deep near-IR photometry of the VISTA Variables in the V'a L'ctea (VVV) Survey and deep DECam Plane Survey (DECaPS) optical photometry to confirm the physical reality of the candidate globular cluster (GC) Minni 22, which is located in the Galactic bulge. This object, which was detected as a high density region in our maps of bulge red giants, is now confirmed as a real GC based on the optical and near-IR color'magnitude diagrams. We also recover three known fundamental mode (ab type) RR Lyrae stars within 2 arcmin of the cluster center. The presence of RR Lyrae stars also seems to confirm Minni 22 as a bonafide old and metal-poor GC. We estimate a cluster reddening E(J - Ks) = 0.6 mag and determine its heliocentric distance D = 7.4 ± 0.3 kpc. The optical and near-IR color'magnitude diagrams reveal well-defined red giant branches in all cases, including a red giant branch bump at Ks = 13.30 ± 0.05 mag. The comparison with theoretical isochrones yields a mean metallicity of [Fe/H] = -1.3 ± 0.3 dex, and age of t ∼ 11.2 Gyr. This is a good example of a new low-luminosity (MV = -6.2 mag) GC found in the central bulge of the Milky Way. After discussing the different ways to confirm the existence of bulge GC candidates, we find that one of the best methods is to use the CMDs from the combination of the DECaPS + VVV photometries. © 2018 The American Astronomical Society. All rights reserved.Ítem Early-type galaxies in the Antlia Cluster: A deep look into scaling relations(Oxford University Press, 2015-05) Calderón, Juan P.; Bassino, Lilia P.; Cellone, Sergio A.; Richtler, Tom; Caso, Juan P.; Gómez, MatíasWe present the first large-scale study of the photometric and structural relations followed by early-type galaxies (ETGs) in the Antlia cluster. Antlia is the third nearest populous galaxy cluster after Fornax and Virgo (d ~ 35 Mpc). A photographic catalogue of its galaxy content was built by Ferguson & Sandage in 1990 (FS90). Afterwards, we performed further analysis of the ETG population located at the cluster centre. Now, we extend our study covering an area four times larger, calculating new total magnitudes and colours, instead of isophotal photometry, as well as structural parameters obtained through Sérsic model fits extrapolated to infinity. This work involves a total of 177 ETGs, out of them 56 per cent have been catalogued by FS90 while the rest (77 galaxies) are newly discovered ones. Medium-resolution GEMINI and Very Large Telescope (VLT) spectra are used to confirm membership when available. Including radial velocities from the literature, 59 ETGs are confirmed as Antlia members. Antlia scaling relations mainly support the existence of unique functions (linear and curved) that join bright and dwarf ETGs, excluding compact ellipticals (cEs). Lenticular galaxies are outliers only with respect to the curved relation derived for effective surface brightness versus absolute magnitude. The small number of bright ellipticals and cEs present in Antlia, prevents us from testing if the same data can be fitted with two different linear sequences, for bright and dwarf ETGs. However, adding data from other clusters and groups, the existence of such sequences is also noticeable in the same scaling relations. © 2015 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society.Ítem Galactic archaeology in the 21st century : unveiling accretion in the MW disc(Universidad Andrés Bello, 2022) Tronrud, Thorold; Tissera, Patricia; Gómez, Facundo A.; Gómez, Matías; Bignone, Lucas; Facultad de Ciencias ExactasThe evolution of large galaxies such as the Milky Way (MW) in Λ Cold Dark Matter (ΛCDM) cosmology is driven by interactions with other galaxies. These interactions affect the structure of the galaxy in long-lasting ways, not only forming the stellar halo, and modifying the size and characteristics of the stellar disc, but also contributing gas that fuels star formation and depositing stars directly into the galaxy. This stellar debris, formed outside the galaxy in which they now reside (a.k.a. ex-situ), retain the chemical fingerprint of the environment in which they formed, leaving them distinct from the stars that were formed within the primary galaxy (a.k.a. in-situ). If these ex-situ stars are located beyond the disc, in the stellar halo, the distributions they occupy in space — based on the kinematics of their progenitor object — may be readily apparent as streams or great circles surrounding the primary galaxy. A population of ex-situ stars are also expected to reside in the stellar disc, even at high circularities. These stars have been found in simulations to be deposited by relatively few massive mergers, but finding them poses a challenge in this dense region. I propose a method, based on training and utilizing neural networks, to classify disc stars as in- or ex-situ based on their chemical parameters. The use of this method is motivated by my research into the effects mergers and accretion have on the galactic stellar disc of a suite of simulated MW-like galaxies, in which I demonstrate that accretion events and accreted stars cause observable changes to calculated metallicity gradients, and can cause disagreements in correlations between observed parameters based on the ages of the stars being used. Galactic discs form inside-out, starting small and slowly expanding with new star formation at the outer edges. This imparts a natural negative age gradient. Stars that have been deposited onto the disc will not necessarily follow this age gradient, which is one of the primary drivers of the stellar disc’s metallicity gradient. These ex-situ stars drive several age-specific correlations between metallicity gradient and 𝑅 −1 eff and 𝜆 ★ gal that vanish entirely once these contaminants are removed. A chemistry-based method for flagging potentially-accreted stars will allow researchers to remove the bulk of these from their samples, which will allow them to examine the evolution of the galactic disc more finely. Furthermore, these flagged, ex-situ stars can be grouped by their characteristics, for attempts to discern early progenitors of the primary galaxy with significantly less noise from stars formed in-situ. I demonstrate that the Galactic Archaeology Neural Network (GANN) recovers usable fractions of nearly every contributor to the suite of simulated stellar discs. Thus, a catalogue of stars flagged by GANN will contain most of the merger information that is present in the stellar disc of a galaxy. Future applications of this method could aid in the discovery of many ancient remnants, and broaden our understanding of how our galaxy formed.Ítem Globular cluster scale sizes in giant galaxies: orbital anisotropy and tidally underfilling clusters in M87, NGC 1399 and NGC 5128(OXFORD UNIV PRESS, 2016-08) Webb, Jeremy J.; Sills, Alison; Harris, William E.; Gómez, Matías; Paolillo, Maurizio; Woodley, Kristin A.; Puzia, Thomas H.We investigate the shallow increase in globular cluster half-light radii with projected galactocentric distance Rgc observed in the giant galaxies M87, NGC 1399, and NGC 5128. To model the trend in each galaxy, we explore the effects of orbital anisotropy and tidally underfilling clusters. While a strong degeneracy exists between the two parameters, we use kinematic studies to help constrain the distance Rβ beyond which cluster orbits become anisotropic, as well as the distance Rfα beyond which clusters are tidally underfilling. For M87 we find Rβ > 27 kpc and 20 < Rfα < 40 kpc and for NGC 1399 Rβ > 13 kpc and 10 < Rfα < 30 kpc. The connection of Rfα with each galaxy's mass profile indicates the relationship between size and Rgc may be imposed at formation, with only inner clusters being tidally affected. The best-fitting models suggest the dynamical histories of brightest cluster galaxies yield similar present-day distributions of cluster properties. For NGC 5128, the central giant in a small galaxy group, we find Rβ > 5 kpc and Rfα > 30 kpc. While we cannot rule out a dependence on Rgc, NGC 5128 is well fitted by a tidally filling cluster population with an isotropic distribution of orbits, suggesting it may have formed via an initial fast accretion phase. Perturbations from the surrounding environment may also affect a galaxy's orbital anisotropy profile, as outer clusters in M87 and NGC 1399 have primarily radial orbits while outer NGC 5128 clusters remain isotropic.Ítem Globular cluster systems as tracers of the evolutionary history in NGC 3258 and NGC 3268(Journal, 2017-09) Caso, Juan Pablo; Bassino, Lilia P.; Gómez, MatíasWe present a new photometric study of NGC 3258 and NGC 3268 globular cluster systems (GCSs), using images in filters B, C, V, R, I and z', obtained from four different telescopes. The wide spatial coverage allows us to estimate the whole extension of both GCSs more precisely than in previous works, and new values for the richness of GC subpopulations. We find differences in the azimuthal distribution between blue (metal-poor) and red (metal-rich) globular clusters (GCs), and confirm that radial profiles flatten towards the centre of the galaxies. In both cases we detected a radial gradient in the colour peak of blue GCs which might be related to the construction of the GCSs. We analyse the similarities and differences in both GCSs, in the context of the possible evolutionary histories of the host galaxies. We also obtain photometric metallicities for a large number of GC candidates around NGC 3258, by applying multicolour-metallicity relations. These results confirm the bimodal metallicity distribution. © 2017 The Authors.Ítem New Candidate Planetary Nebulae in Galactic Globular Clusters from the VVV Survey(Institute of Physics Publishing, 2019-11) Minniti, Dante; Dias, Bruno; Gómez, Matías; Palma, Tali; Pullen, Joyce B.Only four globular cluster planetary nebulae (GCPN) are known so far in the Milky Way. About 50 new globular clusters have been recently discovered toward the Galactic bulge. We present a search for planetary nebulae within 3′ of the new globular clusters, revealing the identification of new candidate GCPN. These possible associations are PN SB 2 with the GC Minni 06, PN G354.9-02.8 with the GC Minni 11, PN G356.8-03.6 with the GC Minni 28, and PN Pe 2-11 with the GC Minni 31. We discard PN H 2-14 located well within the projected tidal radius of the new globular cluster FSR1758 because they have different measured radial velocities. These are interesting objects that need follow-up observations (especially radial velocities) in order to confirm membership and to measure their physical properties in detail. If confirmed, this would double the total number of Galactic GCPN. © 2019. The American Astronomical Society. All rights reserved..Ítem Structural Parameters of the M87 Globular Clusters(2009) Madrid, Juan P.; Harris, William E.; Blakeslee, John P.; Gómez, MatíasWe derive structural parameters for ∼ 2000 globular clusters in the giant Virgo elliptical M87 using extremely deep Hubble Space Telescope images in F606W (V) and F814W (I) taken with the ACS/WFC. The cluster scale sizes (half-light radii rh) and ellipticities are determined from PSF-convolved King-model profile fitting. We find that the rh distribution closely resembles the inner Milky Way clusters, peaking at rh ≃ 2.5 pc and with virtually no clusters more compact than rh ≃ 1 pc. The metal-poor clusters have on average an rh 24% larger than the metal-rich ones. The cluster scale size shows a gradual and noticeable increase with galactocentric distance. Clusters are very slightly larger in the bluer waveband V , a possible hint that we may be beginning to see the effects of mass segregation within the clusters. We also derived a color magnitude diagram for the M87 globular cluster system which show a striking bimodal distribution.Ítem The ages, metallicities, and alpha element enhancements of globular clusters in the elliptical NGC 5128: A homogeneous spectroscopic study with gemini/gemini multi-object spectrograph(Institute of Physics Publishing, 2010) Woodley, Kristin A.; Harris, William E.; Puzia, Thomas H.; Gómez, Matías; Harris, Gretchen L. H.; Geisler, DougWe present new integrated light spectroscopy of globular clusters (GCs) in NGC 5128, a nearby giant elliptical galaxy less than 4 Mpc away, in order to measure radial velocities and derive ages, metallicities, and alpha-element abundance ratios. Using the Gemini South 8 meter telescope with the instrument Gemini Multi-Object Spectrograph, we obtained spectroscopy in the range of ∼ 3400-5700 for 72 GCs with a signal-to-noise ratio greater than 30Å -1; and we have also discovered 35 new GCs within NGC 5128 from our radial velocity measurements. We measured and compared the Lick indices from HδA through Fe5406 with the single stellar population models of Thomas etal. in order to derive age, metallicity, and [α/Fe] values. We also measure Lick indices for 41 Milky Way GCs from Puzia etal. and Schiavon etal. with the same methodology for direct comparison. Our results show that 68% of the NGC 5128 GCs have old ages (>8 Gyr), 14% have intermediate ages (5-8 Gyr), and 18% have young ages (<5 Gyr). However, when we look at the metallicity of the GCs as a function of age, we find 92% of metal-poor GCs and 56% of metal-rich GCs in NGC 5128 have ages >8 Gyr, indicating that the majority of both metallicity subpopulations of GCs formed earlier, with a significant population of young and metal-rich GCs forming later. Our metallicity distribution function generated directly from spectroscopic Lick indices is clearly bimodal, as is the color distribution of the same set of GCs. Thus, the metallicity bimodality is real and not an artifact of the color to metallicity conversion. However, the metallicity distribution function obtained from comparison with the single stellar population models is consistent with a unimodal, bimodal, or multimodal shape. The [α/Fe] values are supersolar with a mean value of 0.14 ± 0.04, indicating a fast formation timescale. However, the GCs in NGC 5128 are not as [α/Fe] enhanced as the Milky Way GCs also examined in this study. Our measured indices also indicate that the GCs in NGC 5128 may have a slight overabundance in nitrogen and a wider range of calcium strength compared to the Milky Way GCs. Our results support a rapid, early formation of the GC system in NGC 5128, with subsequent major accretion and/or GC and star-forming events in more recent times. © 2010. The American Astronomical Society.Ítem The globular cluster systems of the milky way and the Sagittarius dwarf galaxy(Universidad Andrés Bello, 2023) Garro, Elisa Rita; Minniti, D.; Fernández Trincado, Jose Gregorio; Gómez, Matías; Alonso García, Javier; Ripepi, Vincenzo; Facultad de Ciencias ExactasThe VISTA Variables in the Via Lactea Survey (VVV) and its Extension (VVVX) allow us to probe ´ previously unexplored regions of the inner Milky Way (MW), especially those that are affected by stellar crowding and strong extinction. My long-term goal is to identify new star clusters and investigate them to reveal their true nature. In particular, I am looking for new candidate globular clusters (GCs) located in the Galactic bulge and disk, with the aim of completing the census of the MW GC system. I searched and characterized new star clusters, using a combination of the near-infrared (IR) VVV-VVVX survey and Two Micron All Sky survey (2MASS) datasets, and the optical Gaia Data Releases (DR2, EDR3 and DR3) photometry and its precise astrometry and proper motions (PMs). Performing a PM-decontamination procedure, I built final catalogues with high-likely cluster members, on which I carried out a detailed photometric analysis. I estimated the main physical parameters, such as reddenings and extinction, heliocentric and Galactocentric distances, mean cluster PMs, metallicities, ages, integrated luminosities, and structural parameters (core and tidal radii). I analysed 34 new GC candidates in the MW and 21 in the Sagittarius dwarf galaxies, confirming (photometrically) the GC nature for 17 of them, and 4 are old open clusters in the MW bulge and disk, whereas other 17 GCs belonging to the Sagittarius dwarf galaxy. Finally, for 11 bound systems, I collected radial velocity informations (from H-/K-band spectra and/or Gaia DR3 datasets) in order to reconstruct their orbital history for the first time, thus associating these clusters to the relative Galactic components and understand their (in-situ or ex-situ) origin.