Pau Ramos
Pau Ramos
In this study, we devised a methodology to detect the kinematic substructure in velocity space (moving groups) across different the whole Milky Way disc accessible to Gaia DR2.
As a result, we provide the first quantification of the gradients of all known moving groups as a function of Radius and Azimuth.
We demonstrate that the moving groups have a variety of morphologies in Vr-Vphi and different gradients, which constitute one of the first proofs of several dynamical mechanisms acting in superposition on the stellar disc.
Following on our previous work, we re-detected the Sagittarius stream on the RR Lyrae sample (combination of Gaia DR2 and PS1 classifications).
The resulting samples (one focusing on purity, the other on completness) confirmed that the total number of RR Lyrae in the stream must be around ~8k stars as previous works estimated based on partial data.
Since this sample of stars are standard candles, this opened the door into a full 5+1D view of the stream: mean velocities, velocity dispersions, distances, metallicities, etc.
Also, we detected the birfucation in the leading arm and studied in detail the differences in proper motion and distance between both, without finding any significant discrepancy.
With the advent of Gaia DR2, we succeded in procuring the first large sample of stars (~300k) of the Sagittarius stream, as well as measuring with precission its proper motions along the entire first wrap.
As a result, we detected a significant deviation from the expectetions set by N-body models in the proper motions of the leading tidal arm. Latter, it has been confirmed that said deviations are infact the result of the LMC gravitational pull both on Sagittarius as well as on the Milky Way centre of mass (reflex motion).
After characterising the kinematic groups in the Milky Way disc and one of its main perturbers, the Sagittarius dwarf galaxy, we explored the outermost parts of the Galactic disc: the outskirts of the stellar disc.
We used Gaia DR2 to blindly detect Monoceros and ACS using only their kinematics. As a result, we obtained a large sample of stellar members with which we characterised their distance and HR-diagrams.
From our analysis, we concluded that this structures were, most likely, born in the disc and got lunched into inclined orbits by the impact of Sagittarius. If that is the case, our data should be used to constrain not only the orbital parameters of the perturber, but also the chemical evolution of the Milky Way.
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