Found 16 talks width keyword Galactic structure

I will review the status of the QUIJOTE (Q-U-I JOint TEnerife) experiment, a project led from the IAC with the aim of characterising the polarisation of the Cosmic Microwave Background (CMB) and other galactic or extragalactic physical processes that emit in microwaves in the frequency range 10-42GHz, and at large angular scales (1 degree resolution). QUIJOTE consists of two telescopes and three instruments operating from the Teide Observatory, and started operations about 10 years ago, in November 2012.

I will discuss the status of the project, and I will present the latest scientific results associated with the wide survey carried out with the first QUIJOTE instrument (MFI) at 11, 13, 17 and 19GHz, covering approximately 29000 deg$^2$ with polarisation sensitivities in the range of 35-40 $\mu$K/deg. These MFI maps provide the most accurate description we have of the polarization of the emission of the Milky Way in the microwave range, in a frequency domain previously unexplored by other experiments. These maps provide a unique view of the Galactic
magnetic field as traced by the synchrotron emission. These results have been presented in an initial series of 6 scientific articles published on January 12th, 2023.

Finally, I will describe the prospects for future CMB observations from the Teide Observatory.

To understand the early phases of galaxy formation, metal-poor stars in the local universe play a special rôle, allowing to trace both how galactic assembly proceeds, and the conditions in which early star formation proceed. Metal-poor stars in our Galaxy and its satellites are fossils of these past processes and have therefore been the subject of intense dedicated searches and surveys since decades. Here I shall review some of the recent results that the « Pristine » narrow-band photometric survey at CFHT, has enabled, aided by the transformational information brought by the Gaia space mission. These results range from enravelling a very primordial disc in the Milky-Way, characterizing very pristine streams of stars in the galactic halo, and characterizing the co-existing halo and bulge populations in the inner parts of the Milky-Way. Finally, I will outline the plans to characterise further these extreme and very metal-poor stars with the new WEAVE multi-object facility that should start its science surveys early 2023.

To understand the early phases of galaxy formation, metal-poor stars in the local universe play a special rôle, allowing to trace both how galactic assembly proceeds, and the conditions in which early star formation proceed. Metal-poor stars in our Galaxy and its satellites are fossils of these past processes and have therefore been the subject of intense dedicated searches and surveys since decades. Here I shall review some of the recent results that the « Pristine » narrow-band photometric survey at CFHT, has enabled, aided by the transformational information brought by the Gaia space mission. These results range from enravelling a very primordial disc in the Milky-Way, characterizing very pristine streams of stars in the galactic halo, and characterizing the co-existing halo and bulge populations in the inner parts of the Milky-Way. 
Finally, I will outline the plans to characterise further these extreme and very metal-poor stars with the new WEAVE multi-object facility that should start its science surveys early 2023.

After placing the Gaia mission in the context of current astrophysical research, the astrometric, photometric, and spectroscopic data provided by the satellite, as presented in its third data archive, DR3, will be reviewed. Gaia third archive contains, in addition to the measurements from the satellite's instruments, an extensive set of astrophysical parameters derived by the DPAC data processing consortium, for stars, unresolved galaxies, and solar system objects. These parameters correspond to about 1.8 billion sources repeatedly observed by the satellite during the first 34 months of operation. In the case of the Milky Way stars, DR3 contains information for about 1% of its stars, which has made it possible, for the first time, to study the dynamics of the disk and the halo, and to reconstruct the tumultuous evolutionary history of our galaxy, which is etched in its halo. Studying the integrals of the motion and the orbital actions, some 15 episodes of accretion of other galaxies by our galaxy have been identified, which shows that our Galaxy is the result of billions of years of "galactic canibalism". Accretion phenomena and tidal current trails are frequently observed in other galaxies and show that our Universe evolves through a hierarchical formation of galaxies.

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Meeting will be held online

Youtube: https://youtu.be/ns78Go3FM7I

Zoom: https://rediris.zoom.us/j/87455295473?pwd=dnd2SkppQ1F2UlN2K0FLbmlLZEFmZz09

Meeting ID: 874 5529 5473

Passcode: 941406

I discuss the dynamical interactions between the Milky Way and its satellite galaxies, focusing on the closest and most massive satellites - the Large Magellanic Cloud (LMC) and the Sagittarius dwarf galaxy. The former just has had its first close encounter with the Milky Way very recently, and the latter has been orbiting our Galaxy for several Gyr and is tidally disrupting, leaving a prominent tidal stream spanning the entire sky. Thanks to the abundant and precise observational data from the Gaia satellite and various spectroscopic surveys, we now have a very detailed view of the Sagittarius stream and the remnant. It appears that to reproduce its observed properties, one needs to take into account the gravitational effect of the LMC itself and the effect that it produces on the motion of the Milky Way: an intricate dance of three galaxies. The LMC also affects the motion of other streams and satellite galaxies in the outskirts of the Milky Way, and I discuss an approach for compensating these perturbations in the context of dynamical modelling of the Milky Way mass distribution and the analysis of satellite orbits.

The search for the primordial B-modes polarization in the cosmic microwave background (CMB) radiation,
carrying the signature of the primordial gravitational waves from the inflation epoch, motivated a significant
technological progress enabling the next generation of CMB instruments (e.g. CMB-S4, LiteBIRD)
to reach an unprecedented sensitivity. However, such a challenging detection demands a very high control
of the instrumental systematics and CMB foreground emissions.
Among those, the galactic dust polarized emission spectral dependence, not yet fully
characterized, could leave a high level of uncertainty in the cosmological polarization data
producing an ambiguous detection of the CMB B-modes.
Characterizing the dust spectral energy distribution (SED) spatial variations became one of
the most critical issues in the quest for primordial B-modes.
In the work that I will present we have used the release of the Planck satellite HFI data
obtained with the software Sroll2 (Delouis+2019, A&A 629, A38), in order to characterize
and compare the SEDs for polarization and total intensity.
The mean SEDs for dust polarization and total intensity from 353 to 100 GHz are confirmed
to be remarkably close. However, the data show evidence for spatial variations of the
polarization SED. These variations are correlated with variations of dust temperature
measured on total intensity data but the correlation is tight only in the Galactic plane.
At higher latitudes, by considering 90% of useful sky fraction and less, the amplitude of the dust
emission residuals in polarization suggests that an additional contribution, coming from
variations of the polarization angle, becomes dominant. Current models, which extrapolate
the SED spatial variations from total intensity to polarization, would be therefore grossly
simplifying and underestimating the foreground signal to CMB polarization.

The lowest metallicity stars that still exist today represent a window into the early Universe. Studying these stars gives us a local avenue to guide our understanding of star formation and supernova feedback in the early Universe, the early build-up of galaxies like our Milky Way, and the epoch of reionization. In this talk I will present recent results of the Pristine survey, a narrow-band photometric survey of the Milky Way designed to get metallicity information for millions of stars very efficiently. I will discuss what we have learned from our analysis of the most metal-poor stars about the early formation of the Milky Way. Moreover, I will highlight the bright future for this type of study in synergy with the upcoming highly-multiplexed spectroscopic surveys.

The formation and evolution of galaxies across cosmic time proceeds in different phases, paced by their internal evolution and external factors like gas accretion and mergers. The complex and always changing interplay between these mechanisms drives the assembly of galaxies and the physical conditions for star formation, which leaves observable imprints on the stellar populations. Large astrometric and spectroscopic surveys (e.g. Gaia, APOGEE, GALAH) collect the signatures of these past events in the building history of the Milky Way. However, simulations and models are necessary to decode the data. In this talk, I will present results from a series of hydrodynamical simulations of Milky Way-like galaxies, both in isolation and in cosmological context using the VINTERGATAN simulation. I will show the crucial role of mergers, and of the end of the merger phase, in forming the thick and thin Galactic discs, and making the transition between the two. I will then nuance this conclusion by explaining why the secular consumption of gas enables a similar transition, as well as the emergence of spirals, without any external factors.

At present, our understanding of the formation history of the MW is limited due to the complexity of observing the imprints of accretion events and of reproducing them in numerical simulations. Moreover, though being the only galaxy, in which the Galactic potential can be probed in detail, the distribution of mass in the MW, and hence of the dark matter, is poorly constraint, especially at large distances. In addition, the MW is not isolated, and it has recently been suggested that the infall of the LMC can induce a perturbation in the stellar and dark matter distribution of the MW. As a consequence, the details of the formation history of our Galaxy are still unknown, such as the number of accretion events, the mass of the accreted galaxies, and the epoch of these events. Yet this information is crucial to understand our environment and to constrain the theoretical models and simulations that try to reproduce it.

One of the major challenges of the field is that a tremendous number of multi-aspect (astrometric, photometric and spectroscopic) observations at significant depth is required to study the morphology, the kinematics and the chemistry of the outskirts of our Galaxy, where are located the signatures of these events. Hopefully, the advent of recent and incoming complementary large surveys, such as the European Gaia mission, UNIONS (Ultraviolet Near Infrared Optical Northern Survey), Pristine, Pan-STARRS (PS), WEAVE or LSST (Legacy Survey of Space and Time), is offering a new global point of view on our Galaxy’s halo, allowing us to precisely probe the Galactic potential our the MW, and to retrace itsaccretion history.

In this talk I will present recent works that have been conducted to better catarerized our Galaxy and its history with some of the existing surveys mentioned above. In addition, I will present the major improvement that will bring this new generation of large, multi-aspect surveys, to study both our Galactic history, as well as the fundamental nature of the dark matter.

Bosonic ultra-light dark matter (ULDM) in the mass range m ~ $10^{-22} - 10^{-21} \rm eV$ has been invoked as a motivated candidate with new input for the small-scale `puzzles' of cold dark matter. Numerical simulations show that these models form cored density distributions at the center of galaxies ('solitons'). These works also found an empirical scaling relation between the mass of the large-scale host halo and the mass of the central soliton. We show that this relation predicts that the peak circular velocity of the outskirts of the galaxy should approximately repeat itself in the central region. Contrasting this prediction to the measured rotation curves of well-resolved near-by galaxies, we show that ULDM in the mass range m ~ $10^{-22} - 10^{-21} \rm eV$ is in tension with the data.