arXiv subjects

M. Gómez

Publications and source records attributed to M. Gómez.

At least 19 recordsLinked to original sources

arXiv2026

Unresolved triple systems in the aged open cluster Trumpler 19: Discovery, confirmation, and implications

It is difficult to identify unresolved triple and higher-order systems beyond the solar vicinity. Star clusters yield controlled environments with known physical parameters, providing a way to explore homogeneous stellar samples. Combining modern optical and near-IR surveys, our main goal is to explore the region of the color-magnitude diagrams located above the sequence of equal-mass binaries, which is inhabited by unresolved triple and quadruple systems. Specifically, here we aim to discover and characterize the presence of multiple systems in the aged open star cluster Trumpler 19. We selected cluster members using Gaia astrometry and photometry from the VVVX and DECAPS2 surveys. We made optical and near-IR color-magnitude diagrams to select stars located >0.75 mag above the cluster main sequence, including suitable unresolved triple and quadruple systems. We confirm previous results that there is a sizable sequence of unresolved binaries in Trumpler 19. We also report the discovery of a sequence of unresolved multiple systems in this cluster, and confirm some of these multiple systems via radial velocities measured by the ESO KMOS VVVX-GalCen spectroscopic survey. The fraction of multiple stars in this cluster is comparable to that of the solar neighborhood, with the caveat that the local sample probes deeper down the main sequence. The fraction of unresolved triples and quadruples is also three times higher than that of the open cluster M 67, which is of a similar age and chemical composition. The discovery of unresolved triple systems in Trumpler 19 leads to our main conclusion that these systems were able to survive within the cluster for nearly 4 Gyr. In addition, this cluster contains more multiple systems than M 67, which has a similar total present mass. Further investigations are needed to unveil if this is a primordial feature or the result of dynamical evolution.

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arXiv2026

Chemo-dynamical stratification of the Galactic disc using \emph{Gaia}-ESO open clusters

Understanding how the Milky Way disc assembled and evolved requires tracing the coupled evolution of stellar chemistry and orbital structure over time. Open clusters, as coeval stellar populations with well-constrained ages, distances, and chemical properties, provide powerful benchmarks for this purpose. We aim to characterise the age-dependent chemo-dynamical structure of the Galactic disc and to investigate how open clusters populate dynamical phase space as a function of age. We analysed a sample of Galactic open clusters using homogeneous chemical abundances from the Gaia-ESO Survey together with Gaia DR3 phase-space information. Combining cluster ages with orbital parameters and actions, we examined how clusters populate dynamical phase space over the last ~4 Gyr. We find that clusters with similar chemical properties occupy coherent regions of action space, while their orbital structure shows a clear dependence on age. Radial excursions and orbital eccentricities broaden systematically toward older ages, indicating increasingly diverse orbital configurations in the older cluster population. The dispersion in the [Fe/H]-Rg relation also increases with age, consistent with a combination of secular redistribution, survival bias, and dynamically distinct outer-disc populations. In addition, older clusters reach larger vertical amplitudes and vertical actions, revealing a coupled but anisotropic evolution between in-plane and vertical orbital structure. Open clusters provide precise, age-resolved tracers of the chemo-dynamical structure of the Galactic disc. Our results reveal systematic age-dependent variations in the orbital and chemical properties of the cluster population, consistent with the combined effects of secular evolution, orbital redistribution, and environmentally dependent cluster survival over the last few Gyr.

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arXiv2026

Spectral classification of brown dwarfs using machine learning

Brown dwarfs are compact objects that do not reach temperatures high enough to produce sustained hydrogen fusion. Consequently, they cool over time, gradually evolving through later spectral types. In fact, three new spectral types (L, T, and Y) were added to the Harvard sequence to accommodate the spectral features of brown dwarfs. During the cooling process, some brown dwarfs unexpectedly become bluer instead of redder (at optical and near-infrared wavelengths). This phenomenon, known as the bluing effect, is particularly noticeable at the L/T spectral transition. The aim of this work is to approximate the spectral type of brown dwarfs using only photometric data, in particular 2MASS and WISE magnitudes. We used two machine learning algorithms, Random Forest and Gaussian Processes, which were evaluated using a 70/30 train/test split. Both models were trained using 5-fold cross-validation and achieved F1-scores of 0.84 and 0.87, respectively, on the test set. After validating the reliability of the algorithms, we applied them to 21 isolated brown dwarfs without prior spectral type determinations. Our results indicate that 5 of these objects have a spectral type between L0 and L4, while the remaining 16 fall within the M6-M9 range. Machine learning algorithms, combined with multi-band photometry, are a powerful tool for estimating the spectral types of brown dwarfs.

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arXiv2025

The VVVX quest for satellites around the Circinus galaxy

The Circinus galaxy is the nearest type-2 Seyfert galaxy, which is at a distance of 4.2 Mpc. Its environment is challenging to explore because it is located at low Galactic latitudes, behind the Galactic disc. The long-term goal is to characterise the Circinus galaxy halo and determine the presence of dwarf satellites using near-infrared data. We selected 1,542 galaxies from the VVV NIRGC within a 2-degree radius around Circinus, representing 2/3 of the virial radius. Structural parameters such as half-light radii and colours were used, and correlations were examined. A neural network was trained with 486 galaxies with known spectroscopic redshifts to estimate photometric redshifts for all galaxies. Potential satellites were defined based on half-light radii compatible with the typical sizes of dwarf satellites, and combined with photometric redshifts. The galaxy properties are reliably characterised down to $K_{s}$ $\sim$ 15.5 mag, which represents about 90% completeness of detections. At the distance of Circinus, this limiting magnitude corresponds to $K_{s}$ absolute magnitude of $-12.6$ mag, which allows us to find dwarf galaxies. There are 20 galaxies with half-light radii larger than 2.45 arcsec, only 8 have photometric redshifts below 0.04. None of these galaxies is close to Circinus, which has a redshift of 0.0015. The ANNz model exhibited a high degree of accuracy in the range $0.001 < z_{phot} < 0.023$. The presence of dwarf satellites could not be confirmed with the available data in the studied region. The apparent lack of satellites may be genuine, possibly related to AGN feedback effects. This work demonstrates the effectiveness of combining near-infrared data and machine learning techniques to estimate photometric redshifts at low Galactic latitudes, providing useful information for future spectroscopic follow-up campaigns.

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arXiv2025

A song of interactions and mergers: The case of NGC 4709

Globular clusters (GCs) are fundamental tools to unveil the interaction and merger history of their host galaxies. Our goal is to perform the photometric analysis of the globular cluster system (GCS) of the elliptical galaxy NGC 4709, which is the brightest galaxy of the Cen 45 spiral rich galaxy group, and to highlight its interaction history with NGC 4696, the giant elliptical galaxy of the Cen 30 subcluster. Using Magellan 6.5 m MegaCam (g, r, i) photometry, with which we identified a sample of 556 GC candidates around NGC 4709 that were analyzed in the context of the interaction history with the giant elliptical NGC 4696 and other galaxies of the Cen 45 group. Our results point toward a complex interaction history that shaped the GCS of NGC 4709. The GCS is characterized by a bimodal color distribution. Its azimuthal distribution shows a peak coinciding with the direction of NGC 4696, confirming that the interaction between these galaxies shaped the GCS of NGC 4709. From the GC luminosity function, we derived a distance of about 29.9 Mpc, which is much closer than the other galaxies of the Centaurus cluster, and a specific frequency of about 3.7, in good agreement with previously estimated values. From the GCs density maps, we identified overdensities corresponding to the positions of five other galaxies of the Centaurus cluster, and we found a bridge of GCs connecting NGC 4709 to NGC 4696. All of these findings point toward a complex GCS for NGC 4709, strongly influenced by the interaction with NGC 4696, and confirm previous findings that its apparent distance is smaller than that of the main cluster galaxy NGC 4696 by about 8.5 Mpc and that it is smaller than the distance of the other Centaurus galaxies, making it an outlier in Centaurus and suggesting a past first encounter with Cen 30.

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arXiv2025

The VVV near-IR galaxy catalogue of the southern Galactic disc

The distribution of galaxies in the Zone of Avoidance (ZoA) is incomplete due to the presence of our own Galaxy. Our research focused on the identification and characterisation of galaxies in the ZoA, using the new near-infrared data from the VVVX survey in the regions that cover the southern Galactic disc. We used our previously-established procedure based on photometric and morphological criteria to identify galaxies. The large data volume collected by the VVVX required alternatives to visual inspection, including artificial intelligence techniques, such as classifiers based on neural networks. The VVV NIR galaxy catalogue is presented, covering the southern Galactic disc, significantly extending the vision down to $K^0_s=16$ mag throughout the ZoA. This catalogue provides positions, photometric and morphological parameters for a total of 167,559 galaxies with their probabilities determined by the CNN and XGBoost algorithms based on image and photometric data, respectively. The construction of the catalogue involves the employment of optimal probability criteria. 14% of these galaxies were confirmed by visual inspection or by matching with previous catalogues. The peculiarities exhibited by distinct regions across the Galactic disc, along with the characteristics of the galaxies, are thoroughly examined. The catalogue serves as a valuable resource for extragalactic studies within the ZoA, providing a crucial complement to the forthcoming radio catalogues and future surveys utilizing the Vera C.~Rubin Observatory and the Nancy Grace Roman Space Telescope. We present a deep galaxy map, covering a 1080 sq. deg. region, which reveals that the apparent galaxy density is predominantly influenced by foreground extinction from the Milky Way. However, the presence of intrinsic inhomogeneities, potentially associated with candidate galaxy groups or clusters and filaments, is also discernible.

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arXiv2025

Multi-Wavelength characterization of VVVX open clusters

Context. Large-scale surveys across wavelengths, aided by machine learning, have improved the detection of old open clusters in high-extinction Milky Way regions. Aims. We aim to confirm or reject automatically detected open clusters in poorly studied, contaminated regions, refining samples for Galactic disk formation studies. Methods. Using VVVX, 2MASS, and Gaia DR3, we analyzed nine cluster candidates: BH118, BH144, Schuster-MWSC 1756, Saurer 3, FSR 1521, Saurer 2, Haffner 10-FSR 1231, Juchert 12, and Pismis 3. We examined density maps, proper motion diagrams, and photometry to derive physical parameters. Results. We identified star clusters via overdensities in 2MASS, WISE, and DECaPS, confirmed with VVVX and Gaussian Kernel Density Estimation. Using Gaia proper motions, we refined memberships, building a high-likelihood cluster catalog. We derived extinction ($A_{Ks} = 0.07$-$0.50$), color excess ($E(J-Ks) = 0.16$-$0.60$), distances ($D = 2.06$-$8.64$ kpc), and Galactocentric distances ($R_G = 7.69$-$14.81$ kpc). Ages range from 20 Myr to 5 Gyr, metallicity from [Fe/H] = -0.5 to 0.5. Structural parameters include core radii ($r_c = 0.71'$-$5.21'$) and tidal radii ($r_t = 3.4'$-$12.0'$). Conclusions. We confirm the open cluster nature of nine targets, updating their physical parameters.

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arXiv2024

VVVX survey dusts off a new intermediate-age star cluster in the Milky Way disk

Our primary long-term objective is to seek out additional star clusters in the poorly studied regions of the MW. The aim of this pursuit is to finalize the MG'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. We report the discovery of a new star cluster, named Garro~03. We investigated this target using a combination of near-infrared and optical databases. We employed VVVX and 2MASS data in the NIR, and Gaia DR3 and the DECaPS2 datasets in the optical passband. We performed a photometrical analysis in order to derive its main physical parameters. Garro~03 is located at equatorial coordinates RA=14:01:29.3 and Dec=-65:30:57.0. It is not heavily affected by extinction $A_{Ks}=0.25\pm 0.04$ mag. It is located at heliocentric distance of $14.1\pm0.5$ kpc, which places Garro~03 at 10.6 kpc from the Galactic centre and Z=-0.89 kpc below the Galactic plane. We calculated the mean cluster PM of ($μ_α^{\ast},μ_δ) = (-4.57\pm 0.29,\ -1.36\pm 0.27$) mas yr$^{-1}$. We derived an age=3 Gyr and [Fe/H]~$= -0.5\pm 0.2$ by the isochrone-fitting method. The total luminosity was derived in the $K_s$ and V-bands, finding $M_{Ks} = -6.32\pm 1.10$ mag and $M_V =-4.06$ mag. The core and tidal radii were measured constructing the Garro~03 radial density profile and fitting the King model, obtaining $r_c = 3.07\pm 0.98$ pc and $r_t = 19.36\pm 15.96$ pc. 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 possible companionship. We need spectroscopic data to classify it as an old open cluster or a young globular cluster, and to understand its origin.

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arXiv2024

The VISTA Variables in the Vía Láctea eXtended (VVVX) ESO public survey: Completion of the observations and legacy

The ESO public survey VISTA Variables in the Vía Láctea (VVV) surveyed the inner Galactic bulge and the adjacent southern Galactic disk from $2009-2015$. Upon its conclusion, the complementary VVV eXtended (VVVX) survey has expanded both the temporal as well as spatial coverage of the original VVV area, widening it from $562$ to $1700$ sq. deg., as well as providing additional epochs in $JHK_{\rm s}$ filters from $2016-2023$. With the completion of VVVX observations during the first semester of 2023, we present here the observing strategy, a description of data quality and access, and the legacy of VVVX. VVVX took $\sim 2000$ hours, covering about 4% of the sky in the bulge and southern disk. VVVX covered most of the gaps left between the VVV and the VISTA Hemisphere Survey (VHS) areas and extended the VVV time baseline in the obscured regions affected by high extinction and hence hidden from optical observations. VVVX provides a deep $JHK_{\rm s}$ catalogue of $\gtrsim 1.5\times10^9$ point sources, as well as a $K_{\rm s}$ band catalogue of $\sim 10^7$ variable sources. Within the existing VVV area, we produced a $5D$ map of the surveyed region by combining positions, distances, and proper motions of well-understood distance indicators such as red clump stars, RR Lyrae, and Cepheid variables. In March 2023 we successfully finished the VVVX survey observations that started in 2016, an accomplishment for ESO Paranal Observatory upon 4200 hours of observations for VVV+VVVX. The VVV+VVVX catalogues complement those from the Gaia mission at low Galactic latitudes and provide spectroscopic targets for the forthcoming ESO high-multiplex spectrographs MOONS and 4MOST.

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arXiv2024

The turbulent life of NGC 4696 as told by its globular cluster system

In this work we perform the photometric analysis of the globular cluster system (GCS) of the giant elliptical NGC4696, which is the brightest member of Centaurus, a rich and dynamically young galaxy cluster. We obtained deep Magellan 6.5 m/MegaCam (g', r', i') photometry, with which we identified a sample of 3818 stellar clusters around NGC4696 that were analyzed in the context of possible interactions and its assembly history. After carefully modeling and subtracting the galaxy light, we used selection criteria based on the shape, colors, and magnitudes to identify GC candidates. We find a number of features that indicate a disturbed GCS that points toward a complex evolution with other neighboring members of Centaurus. Formally, two subpopulations could be found at (g'-i')_0 = 0.763 $\pm$ 0.004 and (g'-i')_0=1.012 $\pm$ 0.004. Moreover, the color distribution does not show the presence of a significant blue tilt, but it presents a trend with the radius, where at small galactocentric distances a unimodal distribution is preferable to a bimodal one, suggesting the presence of an intermediate GC population. Besides the color distribution, the metallicity distribution also shows a bimodal trend, with peaks at [Fe/H]=-1.363 $\pm$ 0.010 and [Fe/H]=-0.488 $\pm$ 0.012. The radial density profiles show different slopes for the blue and red populations and the azimuthal distributions are well fitted by an asymmetrical sinusoidal function, with peaks projecting toward two nearby galaxies, NGC4696B and NGC4709, indicating past interactions among these three galaxies. Finally, we derived a GC specific frequency of S_N=6.8 $\pm$ 0.9, in good agreement with the values obtained for other giant ellipticals and with previously estimated S_N of NGC4696. All these results point toward a complex GCS, strongly influenced by the interaction history of NGC4696 with the other galaxies of the Centaurus cluster.

astro-ph.GA↗

arXiv2022

The globular cluster system of the nearest Seyfert II galaxy Circinus

Context. The globular cluster (GC) system of Circinus galaxy has not been probed previously partly because of the location of the galaxy at - 3.8$^\circ$ Galactic latitude which suffers severely from interstellar extinction, stellar crowding, and Galactic foreground contamination. However, the deep near-infrared (NIR) photometry by the VISTA Variables in the Via Láctea Extended Survey (VVVX) in combination with the precise astrometry of Gaia EDR3 allow us to map GCs in this region. Aims. Our long-term goal is to study and characterise the distributions of GCs and Ultra-compact dwarfs of Circinus galaxy which is the nearest Seyfert II galaxy. Here we conduct the first pilot search for GCs in this galaxy. Methods. We use NIR VVVX photometry in combination with Gaia EDR3 astrometric features such as astrometric excess noise and BP/RP excess factor to build the first homogeneous catalogue of GCs in Circinus galaxy. A robust combination of selection criteria allows us to effectively clean interlopers from our sample. Results. We report the detection of$\sim$ 70 GC candidates in this galaxy at a 3 $σ$ confidence level. They show a bimodal colour distribution with the blue peak at (G-Ks)$_0$ = 0.985$\pm$0.127 mag with a dispersion of 0.211$\pm$0.091 mag and the red peak at (G-Ks)$_0$ = 1.625$\pm$0.177 mag with a dispersion of 0.482$\pm$0.114 mag. A GC specific frequency (S$_N$) of 1.3$\pm$0.2 was derived for the galaxy, and we estimated a total population of 120$\pm$40 GCs. Based on the projected radial distribution it appears that Circinus has a different distribution of GC candidates than MW and M31. Conclusions. We demonstrate that Circinus galaxy hosts a sizeable number of cluster candidates. This result is the first leap towards understanding the evolution of old stellar clusters in this galaxy.

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arXiv2022

High-contrast imaging of HD 29992 and HD 196385 with GPI

Based on high contrast images obtained with the Gemini Planet Imager (GPI), we report the discovery of two point-like sources at angular separations of $ρ\sim0.18''$ and $ρ\sim0.80''$ from the stars HD 29992 and HD 196385. A combined analysis of the new GPI observations and images from the literature indicates that the source close to HD 29992 could be a companion to the star. Concerning HD 196385, the small number of contaminants ($\sim0.5$) suggests that the detected source may be gravitationally bound to the star. For both systems, we discarded the presence of other potential companions with $m>75$ M$_{\rm Jup}$ at $ρ\sim0.3 - 1.3''$. From stellar model atmospheres and low-resolution GPI spectra, we derive masses of $\sim0.2$ - $0.3$ M$_{\odot}$ for these sources. Using a Markov-chain Monte Carlo approach, we performed a joint fit of the new astrometry measurements and published radial velocity data to characterize the possible orbits. For HD 196385B, the median dynamic mass is in agreement with that derived from model atmospheres, whilst for HD 29992B, the orbital fit favors masses close to the brown dwarf regime($\sim0.08$ M$_{\odot}$). HD 29992 and HD 196385 might be two new binary systems with M-type stellar companions. However, new high angular resolution images would help to definitively confirm whether the detected sources are gravitationally bound to their respective stars, and permit tighter constraints on the orbital parameters of both systems.

astro-ph.SR↗

arXiv2022

A new low-luminosity globular cluster discovered in the Milky Way with the VVVX survey

The VISTA Variables in the Via Láctea Extended Survey (VVVX) allows probing previously unexplored regions of the inner Milky Way (MW). We are looking for new candidate globular clusters (GCs), with the aim of completing the census of the MW GC system. We searched and characterised new GCs, using a combination of the near-IR VVVX survey and 2MASS datasets, and the optical Gaia EDR3 photometry and its precise proper motions (PMs). We report the discovery of a new Galactic GC, named Garro 02, situated at RA=18:05:51.1, Dec=-17:42:02 and l=12.042 deg, b=+1.656 deg. Performing a PM-decontamination procedure, we built a final catalogue with all cluster members, on which we performed a photometric analysis. We calculated a reddening of $E(J-K_s)=1.07\pm 0.06$ mag and extinction of $A_{Ks}=0.79\pm 0.04$ mag in the near-IR; while $E(BP-RP)=2.40\pm 0.01$ mag and $A_{G}=4.80\pm 0.02$ mag in optical passbands. Its heliocentric distance is $D=5.6\pm 0.8$ kpc, which places Garro 02 at a Galactocentric distance of $R_G=2.9$ kpc and Z=0.006 kpc above the Galactic plane. We estimated the metallicity and age by comparison with known GCs and by fitting PARSEC isochrones, finding [Fe/H]$=-1.30\pm 0.2$ dex and age=$12\pm 2$ Gyr. We derived the mean cluster PM of $(μ_α^{\ast}, μ_δ) = (-6.07\pm 0.62, -6.15\pm 0.75)$ mas yr$^{-1}$. We calculated the cluster luminosity in the near-IR of $M_{Ks}=-7.52\pm 1.23$ mag, which is equivalent to $M_{V}=-5.44$ mag. The core and tidal radii from the radial density profile are $r_c =1.25\pm 0.27$ arcmin (2.07 pc) and $r_t = 7.13\pm 3.83$ arcmin (11.82 pc), respectively. We confirm Garro 02 as a new genuine Galactic GC, located in the MW bulge. It is a low-luminosity, metal-poor, and old GC, and it is a lucky survivor of the strong dynamical processes that occurred during the MW's entire life.

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arXiv2021

Unveiling the nature of 12 new low-luminosity Galactic Globular Cluster Candidates

The Galactic globular cluster system is incomplete, especially in the low latitude regions of the Galactic bulge and disk. We report the physical characterization of twelve star clusters in the Milky Way, most of which are explored here for the first time. Our aim is determining their main physical parameters, such as reddening and extinction, metallicity, age, total luminosity, mean cluster proper motions (PMs), distances, in order to unveil their physical nature. We study the clusters using optical and near-infrared (NIR) datasets. We use the Gaia Early Data Release 3 (EDR3) PMs in order to perform a PM-decontamination procedure and build final catalogues. We match the Gaia EDR3 with the VISTA Variables in the Vía Láctea extended (VVVX) survey and Two Micron All Sky survey (2MASS) in the NIR, in order to construct complete colour-magnitude diagrams (CMDs) and investigate the clusters properties. The extinctions are evaluated using existing reddening maps, spanning $0.09\lesssim A_{Ks}\lesssim 0.86$ mag and $0.89 \lesssim A_{G}\lesssim 4.72$ mag in the NIR and optical, respectively. We obtain their heliocentric distances, that range from about 4 to 20 kpc, placing these clusters at $3\lesssim R_{G}\lesssim 14$ kpc from the Galactic centre. The best PARSEC isochrone fit yields a metallicity range of $-1.8<$[Fe/H]$<+0.3$ and an approximative age range of $2<$Age$<14$ Gyr. We find that all clusters have low-luminosities, with $-6.9<M_{V}<-3.5$ mag. Based on our photometric analysis, we confirm the OC nature for Kronberger100, while we classify Patchick125 as a metal-poor GC, Ferrero54 as a metal-rich GC, and ESO92-18 as a possible old OC or young GC. The classification as GC candidates is also suggested for Kronberger99, Patchick122, Patchick126, Riddle15, FSR190 and Gaia2. We also conclude that Kronberger119 and Kronberger143 might be either old OCs or young GCs.

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arXiv2021

High-resolution images of two wiggling stellar jets, MHO 1502 and MHO 2147, obtained with GSAOI+GeMS

We investigated the possible cause-effect relation between the wiggling shape of two stellar jets, MHO 1502 and MHO 2147, and the potential binarity of the respective driving stars. We present high-angular-resolution H$_2$ (2.122 $μ$m) and K-band images obtained with the Gemini South Adaptive Optics Imager (GSAOI) and the Gemini Multi-conjugate Adaptive Optics System (GeMS). The profiles of the jets are depicted in detail by the H$_2$ images. We used K-band data to search for potential close companions to the previously suggested exciting sources, and used archive data to investigate these sources and the environments in which the jets are located. We also applied a model to reproduce the wiggling profiles of the jets. MHO~1502 is composed of a chain of knots delineating the wiggling jet, suggesting that the driving source emitted them in an intermittent manner. Our K-band image of the previously proposed exciting star, IRAC 18064, shows two sources separated by $\sim240$ AU, hinting at its binarity. However, as IRAC 18064 is located off the jet axis at $\sim2064$ AU, it is questionable as to whether this source is the true exciting star. Moreover, the orbital model centred on IRAC 18064 suggests a binary companion at a much greater distance ($\sim2200$ AU) than the nearby star (at $\sim$240 AU). On the other hand, the orbital model centred on the axis provides the best fits. Nevertheless, the precession model centred on the axis cannot be discarded, despite having larger residuals and $χ^2$. MHO 2147 displays an S-shaped gentle continuous emission in H$_2$. We identify two other jets in the field of MHO 2147: a previously reported quasi-perpendicular jet, MHO 2148, and a third jet adjacent to MHO 2147. The model that best fits the morphology of the MHO 2147 jet and that of its adjacent jet is precession. The exciting source of MHO 2147 may be a triple system.

astro-ph.SR↗

arXiv2021

Inspection of 19 globular cluster candidates in the Galactic bulge with the VVV survey

The census of the globular clusters (GCs) in the Milky Way (MW) is still a work in progress. We explore the nature of 19 new GC candidates in the Galactic bulge, based on the analysis of their colour-magnitude diagrams (CMDs) in the near-IR, using the VISTA Variables in the Via Láctea Survey (VVV) database. We estimate their main astrophysical parameters: reddening and extinction, distance, total luminosity, mean cluster proper motions (PMs), metallicity and age. We obtain the cluster catalogues including the likely cluster members by applying a decontamination procedure on the observed CMDs, based upon the vector PM diagrams from VIRAC2. We estimate a wide reddening range of the $0.25 \leqslant E(J-K_s) \leqslant 2.0$ mag and extinction $0.11 \leqslant A_{Ks} \leqslant 0.86$ mag for the sample clusters as expected in the bulge regions. The range of heliocentric distances is $6.8\leqslant D\leqslant 11.4$ kpc. This allows us to place these clusters between 0.56 and 3.25 kpc from the Galactic centre, assuming $R_{\odot}=8.2$ kpc. Also, their PMs are kinematically similar to the typical motion of the Galactic bulge, apart from VVV-CL160, which shows different PMs. We also derive their metallicities and ages, finding $-1.40 \leqslant$ [Fe/H] $\leqslant 0.0$ dex and $t\approx 8-13$ Gyr respectively. The luminosities are calculated both in $K_{s}-$ and V-bands, recovering $-3.4 \leqslant M_V \leqslant -7.5$. We also examine the possible RR Lyrae members found in the cluster fields. Based on their positions, kinematics, metallicities and ages and comparing our results with the literature, we conclude that 9 candidates are real GCs, 7 need more observations to be fully confirmed as GCs, whereas 3 candidates are discarded for being younger open clusters.

astro-ph.GA↗

arXiv2021

Physical characterization of recently discovered globular clusters in the Sagittarius dwarf spheroidal galaxy II. Metallicities, ages and luminosities

Globular clusters (GCs) are important tools to rebuild the accretion history of a galaxy. There are newly discovered GCs in the Sagittarius (Sgr) dwarf galaxy, that can be used as probes of the accretion event onto the Milky Way (MW). Our main aim is to characterize the Sgr GC system by measuring its main physical parameters. We build the optical and near-IR color-magnitude diagrams (CMDs) for 21 new Sgr GCs using the VISTA Variables in the Via Lactea Extended Survey (VVVX) near-IR database combined with the Gaia EDR3 optical database. We derive metallicities and ages for all targets, using the isochrone-fitting method and the RGB-slope and metallicity relation. The total luminosities are calculated both in the near-IR and in the optical. We construct the metallicity distribution (MD), the globular cluster luminosity function (GCLF), and the age-metallicity relation for the Sgr GC system. We find 17 metal-rich GCs with -0.9<[Fe/H]<-0.3, 4 metal-poor GCs with -2.0<[Fe/H]<-1.1 in the new Sgr GC sample. Even though our age estimates are rough, we find that the metal-poor GCs are consistent with an old population with an average age of ~13 Gyr, while the metal-rich GCs show a wider age range, between 6-8 Gyr and 10-13 Gyr. We compare the MD and the GCLF for the Sgr GC system with those of the MW, M31 and Large Magellanic Cloud (LMC) galaxies. We conclude that the majority of the metal-rich GCs are located within the main body of Sgr galaxy. We confirm that the GCLF is not a universal distribution, since the Sgr GCLF peaks at fainter luminosities than the GCLFs of the MW, M31 and LMC. The MD shows a double-peaked distribution, and we note that the metal-rich population looks like the MW bulge GCs. We compared our results with the literature concluding that the Sgr progenitor could have been a reasonably large galaxy able to retain the SNe ejecta, thus enriching its ISM.

astro-ph.GA↗

arXiv2021

An Intriguing Globular Cluster in the Galactic Bulge from the VVV Survey

Recent near-IR Surveys have discovered a number of new bulge globular cluster (GC) candidates that need to be further investigated. Our main objective is to use public data from the Gaia Mission, VVV, 2MASS and WISE in order to measure the physical parameters of Minni48, a new candidate GC located in the inner bulge of the Galaxy at l=359.35 deg, b=2.79 deg. Even though there is a bright foreground star contaminating the field, the cluster appears quite bright in near- and mid-IR images. We obtain deep decontaminated optical and near-IR colour-magnitude diagrams (CMDs) for this cluster. The heliocentric cluster distance is determined from the red clump (RC) and the red giant branch (RGB) tip magnitudes in the near-IR CMD, while the cluster metallicity is estimated from the RGB slope and the fit to theoretical isochrones. The GC size is found to be r = 6' +/- 1', while reddening and extinction values are E(J-Ks)=0.60 +/- 0.05 mag, A_G=3.23 +/- 0.10 mag, A_Ks=0.45 +/- 0.05 mag. The resulting mean Gaia proper motions are PMRA=-3.5 +/- 0.5 mas/yr, PMDEC=-6.0 +/- 0.5 mas/yr. The IR magnitude of the RC yields an accurate distance modulus estimate of (m-M)_0=14.61 mag, equivalent to a distance D=8.4 +/- 1.0 kpc. This is consistent with the optical distance estimate: (m-M)_0=14.67 mag, D=8.6 +/- 1.0 kpc, and with the RGB tip distance: (m-M)_0=14.45 mag, D=7.8 +/- 1.0 kpc. The derived metallicity is [Fe/H]=-0.20 +/- 0.30 dex. A good fit to the PARSEC stellar isochrones is obtained in all CMDs using Age = 10 +/- 2 Gyr. The total absolute magnitude of this GC is estimated to be M_Ks= -9.04 +/- 0.66 mag. Based on its position, kinematics, metallicity and age, we conclude that Minni48 is a genuine GC, similar to other well known metal-rich bulge GCs. It is located at a projected Galactocentric angular distance of 2.9 deg, equivalent to 0.4 kpc, being one of the closest GCs to the Galactic centre.

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