Resumen:

Many globular clusters (GCs) in the Milky Way (MW) have been studied in recent years, especially in hidden regions, like the MW bulge. We want to understand what we can learn if we include these new objects into the MWGC system that we know today. We catalogue 45 recently discovered GCs. We use metallicity distribution (MD), luminosity function (LF), age distribution, and [Mg/Fe]-[Fe/H] diagram for investigating the Galactic bulge GC system. We consider 3 samples: new GCs, known and well-characterized GCs and a merging of these two samples. We find a double-peaked distribution for the LF and MDs. We also construct the MD for the field star sample, and comparing this with that one of the GCs, we learn that a high percentage of field stars show [Fe/H]>0, whereas we do not detect any GCs in the same metallicity range. Therefore, we construct the age-metallicity diagram for both samples, noting that the old and metal-poor population is represented by GCs, while the young and metal-rich population corresponds to field stars. We build up the [Mg/Fe]-[Fe/H] diagram for known GCs and field stars, finding that the GCs are formed during the initial burst. The most metal-rich GCs seem to be the outcome of a violent and bursty star formation in the bulge or from an accreted metal-rich elliptical galaxy. We conclude that the bimodal distribution of GCLF suggests that many GCs have been accreted during past merging events. This is also supported by the MD, which indicates that the metal-poor component is mainly the contribution due to the tidal disruption of dwarf-like objects whereas the metal-rich population is related to the formation of the bulge and/or disk. The difference that we notice between the cluster and field star samples should be sought in the evolutionary difference between these two stellar populations.

Resumen:

The warp is a well-known undulation of the Milky Way disc. Its structure has been widely studied, but only since Gaia DR2 has it been possible to reveal its kinematic signature beyond the solar neighbourhood. In this work we will present an analysis of the warp's structure by means of a Fourier decomposition in vertical high ($Z$) and vertical velocity ($V_z$) traced by Cepheids. We find a clear but complex signal that in both variables reveals an asymmetrical warp. In $Z$ we find the warp to be almost symmetric in amplitude at the disc's outskirts but with the two extremes never being diametrically opposed at any radius and the line of nodes presenting a twist in the direction of stellar rotation for $R>11$ kpc. In $V_z$ an $m=2$ mode is needed to represent the kinematic signal of the warp, reflecting its azimuthal asymmetry. We also find that the line of maximum vertical velocity is similarly twisted but does not overlap with the line of nodes, it trails behind by $\approx 25$ deg. We will show how the twisted line of maximum $V_z$ creates "arches" in the mean $V_z$ as a function of radii, a signature of global warp kinematics that has been observed with other tracers with less azimuthal coverage of the disc. Finally, a joint analysis of the Fourier decompositions in $Z$ and $V_z$ allows us to develop a new model-independent formalism to derive the pattern speed and change in amplitude of each mode at each radii. By applying it to our results for the Cepheids we find, for the $m=1$ mode, a constant pattern speed in the direction of stellar rotation of $9.18$ km/s/kpc, a constant amplitude up to $R\approx 14$ kpc and a slight increase in amplitude at larger radii, in agreement with previous works.

Resumen:

We use a combination of data from 2MASS, WISE, APOGEE, and Gaia DR3 to study the kinematic and chemical properties of Monoceros' stellar overdensity. Monoceros is a structure located towards the Galactic anticenter and close to the Galactic plane. We identified that its stars have azimuthal velocity in the range of 200 < v(phi) (km/s) < 250. Combining their kinematics and spatial distribution, we designed a new method to select stars from this overdensity. This method allows us to easily identify the structure in both hemispheres and estimate their distances. Furthermore, we characterized, for the first time, the Monoceros overdensity in several chemical-abundance spaces. Our results demonstrate that the southern (Mon-S) and northern (Mon-N) regions of Monoceros exhibit indistinguishable chemical compositions, and we also confirm their resemblance to stars found in the thin disk of the Galaxy and suggesting an in situ formation.