Examinando por Autor "Gómez M."
Mostrando 1 - 5 de 5
Resultados por página
Opciones de ordenación
Ítem The curious case of the companion: Evidence for cold accretion onto a dwarf satellite near the isolated elliptical NGC 7796(EDP Sciences, 2018-12) Richtler T.; Hilker M.; Voggel K.; Puzia T.H.; Salinas R.; Gómez M.; Lane R.Context. The isolated elliptical (IE) NGC 7796 is accompanied by an interesting early-type dwarf galaxy, named NGC 7796-DW1. It exhibits a tidal tail, very boxy isophotes, and multiple nuclei or regions (A, B, and C) that are bluer than the bulk population of the galaxy, indicating a younger age. These properties are suggestive of a dwarf-dwarf merger remnant. Aims. Dwarf-dwarf mergers are poorly understood, but may have a high importance for dwarf galaxy evolution. We want to investigate the properties of the dwarf galaxy and its components to find more evidence for a dwarf-dwarf merger or for alternative formation scenarios. Methods. We use the Multi-Unit Spectroscopic Explorer (MUSE) at the VLT to investigate NGC 7796-DW1. We extract characteristic spectra to which we apply the STARLIGHT population synthesis software to obtain ages and metallicities of the various population components of the galaxy. This permits us to isolate the emission lines for which fluxes and flux ratios can be measured and to which strong-line diagnostic tools can be applied. Results. The galaxy's main body is old and metal-poor. A surprising result is the extended line emission in the galaxy, forming a ring-like structure with a projected diameter of 2.2 kpc. The line ratios fall into the regime of HII-regions, although OB-stellar populations cannot be identified by spectral signatures. The low Hα surface brightnesses indicate unresolved star-forming substructures, which means that broad-band colours are not reliable age or metallicity indicators. Nucleus A is a relatively old (7 Gyr or older) and metalpoor super star cluster, most probably the nucleus of the dwarf, now displaced. The star-forming regions B and C show younger and distinctly more metal-rich components. The emission line ratios of regions B and C indicate an almost solar oxygen abundance, if compared with radiation models of HII regions. Oxygen abundances from empirical calibrations point to only half-solar. The ring-like Hα-structure does not exhibit signs of rotation or orbital movements. Conclusions. NGC 7796-DW1 occupies a particular role in the group of transition-type galaxies with respect to its origin and current evolutionary state, being the companion of an IE. The dwarf-dwarf merger scenario is excluded because of the missing metal-rich merger component. A viable alternative is gas accretion from a reservoir of cold, metal-rich gas. NGC 7796 has to provide this gas within its X-ray bright halo. As illustrated by NGC 7796-DW1, cold accretion may be a general solution to the problem of extended star formation histories in transition dwarf galaxies. © ESO 2018.Ítem The globular cluster system of NGC 1316: IV. Nature of the star cluster complex SH2(EDP Sciences, 2017-05) Richtler T.; Husemann B.; Hilker M.; b; Puzia T.H.; Bresolin F.; Gómez M.Context. The light of the merger remnant NGC 1316 (Fornax A) is dominated by old and intermediate-age stars. The only sign of current star formation in this big galaxy is the Hii region SH2, an isolated star cluster complex with a ring-like morphology and an estimated age of 0.1 Gyr at a galactocentric distance of about 35 kpc. A nearby intermediate-age globular cluster, surrounded by weak line emission and a few more young star clusters, is kinematically associated. The origin of this complex is enigmatic. Aims. We want to investigate the nature of this star cluster complex. The nebular emission lines permit a metallicity determination which can discriminate between a dwarf galaxy or other possible precursors. Methods. We used the Integral Field Unit (IFU) of the VIMOS instrument at the Very Large Telescope of the European Southern Observatory in high dispersion mode to study the morphology, kinematics, and metallicity employing line maps, velocity maps, and line diagnostics of a few characteristic spectra. Results. The line ratios of different spectra vary, indicating highly structured Hii regions, but define a locus of uniform metallicity. The strong-line diagnostic diagrams and empirical calibrations point to a nearly solar or even super-solar oxygen abundance. The velocity dispersion of the gas is highest in the region offset from the bright clusters. Star formation may be active on a low level. There is evidence for a large-scale disk-like structure in the region of SH2, which would make the similar radial velocity of the nearby globular cluster easier to understand. Conclusions. The high metallicity does not fit to a dwarf galaxy as progenitor. We favour the scenario of a free-floating gaseous complex having its origin in the merger 2 Gyr ago. Over a long period the densities increased secularly until finally the threshold for star formation was reached. SH2 illustrates how massive star clusters can form outside starbursts and without a considerable field population. © 2017 ESO.Ítem Three new Galactic globular cluster candidates: FSR1700, Teutsch67, and CWNU4193(EDP Sciences, 2024-09) Saroon S.; Dias B.; Minniti D.; Parisi M.C.; Gómez M.; Alonso-García J.The VISTA Variables in the Via Láctea Extended Survey (VVVX) enables exploration of previously uncharted territories within the inner Milky Way (MW), particularly those obscured by stellar crowding and intense extinction. Our objective is to identify and investigate new star clusters to elucidate their intrinsic characteristics. Specifically, we are focused on uncovering new candidate globular clusters (GCs) situated at low Galactic latitudes, with the ultimate goal of completing the census of the MW GC system. Leveraging a combination of near-infrared (NIR) data from the VVVX survey and Two Micron All Sky Survey (2MASS), along with optical photometry and precise proper motions (PMs) from the Gaia Data Release 3 (DR3), we are conducting a systematic characterisation of new GCs. As a result, we report the discovery and characterisation of four new Galactic clusters named FSR 1700, FSR 1415, CWNU 4193, and Teutsch 67, all located within the MW disc. We estimate a wide range of reddening, with values ranging from 0.44 to 0.73 mag for E(J'''Ks). The heliocentric distances span from 10.3 to 13.2 kpc. Additionally, we determine their metallicities and ages, finding a range of '0.85 to '0.75 dex for [Fe/H] and ages approximately close to 11 Gyr, respectively. FSR 1415 is an exception; it is an old open cluster with an age of 3 Gyr and [Fe/H] of '0.10. Furthermore, we fitted the radial density profiles to derive their structural parameters like the tidal radius, core radius, and concentration parameters. In conclusion, based on their positions, kinematics, metallicities, and ages, and comparing our findings with existing literature, we categorise FSR 1700, Teutsch 67, and CWNU 4193 as genuine GC candidates, while FSR 1415 is an old open cluster exhibiting characteristics of a post-core-collapse cluster.Ítem VVVX survey dusts off a new intermediate-age star cluster in the Milky Way disk(EDP Sciences, 2024-08) Garro E.R.; Minniti D.; Alonso-García J.; Fernández-Trincado J.G.; Gómez M.; Palma T.; Saito R.K.; Obasi C.Context. In the last decade, many new star clusters have been discovered in heavily obscured regions of the Milky Way bulge and disk. Aims. Our primary long-term objective is to seek out additional star clusters in the poorly studied regions of the Milky Way, where detections pose significant challenges. The aim of this pursuit is to finalize the Milky Way's globular and open cluster system census and to gain a comprehensive understanding of both the formation and evolution of these systems and our Galaxy as a whole. Methods. We report the discovery of a new star cluster, named Garro 03. We investigated this new target using a combination of near-infrared and optical databases. We employed the VISTA Variables in the Via Láctea Survey and Two Micron All Sky Survey data in the near-infrared, and the Gaia Data Release 3 and the DECam Plane Survey datasets in the optical passband. We constructed density maps and vector proper motion diagrams in order to highlight our target. We performed a photometrical analysis in order to derive its main physical parameters. Results. Garro 03 is located at equatorial coordinates RA = 14:01:29.3 and Dec = -65:30:57.0. From our photometric analysis we find that this cluster is not heavily affected by extinction with AKs = 0.25 ± 0.04 mag and AG = 1.54 ± 0.02 mag. It is located at heliocentric distance of 14.1 ± 0.5 kpc, which places Garro 03 at 10.6 kpc from the Galactic centre and Z = -0.89 kpc below the Galactic plane. We also calculated the mean cluster proper motion of (μα∗,μδ)=(-4.57 ± 0.29, -1.36 ± 0.27) mas yr-1. We derived an age of 3 Gyr and metallicity [Fe/H] = -0.5 ± 0.2 by the isochrone-fitting method, employing the PARSEC models. The total luminosity was derived in the Ks and V bands, finding MKs = -6.32 ± 1.10 mag and MV = -4.06 mag. Finally, the core and tidal radii were measured constructing the Garro 03 radial density profile and fitting the King model. We obtained rc = 3.07 ± 0.98 pc and rt = 19.36 ± 15.96 pc, respectively. Conclusions. We photometrically confirm the cluster nature for Garro 03, located in the Galactic disk. It is a distant, low-luminosity, metal-rich star cluster of intermediate age. We also searched for possible signatures (streams or bridges) between Garro 03 and Garro 01, but we exclude a companionship with the present analysis. We need spectroscopic data to classify it as an old open cluster or a young globular cluster, and to understand its origin.Ítem Wide-field study of the peculiar globular cluster system hosted by the field lenticular NGC 1172(Oxford University Press, 2020-12) Ennis A.I.; Caso J.P.; Bassino L.P.; Salinas R.; Gómez M.We present a wide-field study of the globular cluster system (GCS) of the field lenticular galaxy NGC 1172, based on observations from Gemini Multi-Object Spectrograph/Gemini (optical), FourStar/Magellan (NIR), and archival data from ACS/Hubble Space Telescope (optical). This analysis covers the full extension of the GCS, and results in a value of specific frequency (SN = 8.6 ± 1.5) peculiarly high for an intermediate-mass galaxy in a low-density environment such as this one. We find that the GCS appears to be bimodal, although the colour distribution is narrow and does not allow for an accurate separation of the subpopulations. However, the combination of optical and NIR filters allows us to obtain an estimation of the metallicity distribution based on the photometry, which supports bimodality. We conclude that the presence of a large fraction of metal-poor globular clusters (GCs) and the high specific frequency point to NGC 1172 having accreted a significant amount of GCs from low-mass satellites in the past. © 2020 The Author(s).