Found 215 talks archived in Galaxies
I present a detailed analysis of the scaling relations of ETGs and suggest a way to predict the evolution of the distributions of galaxies in these planes. This new approach is able to account of several features observed in the FP projections and of the tilt of the Fundamental Plane.
Meeting ID: 817 0462 3667
Dwarf galaxies are powerful tools of near-field cosmology and galactic archaeology: their numbers, distribution, and star formation can be linked to both the tenets of LCDM (the missing satellite "problem," their (an)isotropic distribution, their dark matter content) and to the build up of their hosts and their environment (accretion, quenching). The exquisite detail offered by observation of the nearby Milky Way dwarf galaxies has built a picture of what dwarf galaxies are and how they evolved through time. In this talk, I will review the increasingly sharp view we are building of the dwarf-galaxy system of the Milky Way's "sister" galaxy, Andromeda, and emphasize key similarities and differences between these two systems of satellites in the hope to learn what features are common or, on the contrary, driven by the different pasts of the Milky Way and Andromeda.
Meeting ID: 841 1580 773
In this talk, I will present recent results on a new sample of extremely UV-luminous star-forming galaxies at z=2-4 discovered within the 9000deg^2-wide Baryon Oscillation Spectroscopic Survey database of the Sloan Digital Sky Survey. These puzzling sources show apparent magnitudes rivaling those of bright QSOs, but without any hint of AGN activity or being magnified by gravitational lensing. Instead, these sources are characterized by very young stellar populations (~ 10 Myr) and compact morphologies. The two highest-redshift sources in our sample show very high Lyman continuum (LyC, with >13.6 eV) escape fractions, up to fesc(LyC)~90%, being the most powerful ionizing sources identified so far among the star-forming galaxy population, both in terms of the intrinsic LyC photon production rate and escape. With SFRs~1000 Msun/yr, but almost un-obscured, and specific star formation sSFR >50-100 Gyr^-1, these sources are very efficient star-forming galaxies, possibly representing a short-lived phase in the evolution of massive and compact galaxies. I will highlight some unique properties observed in these sources including LyC emission, complex Lyman-alpha profiles, strong wind lines, SEDs, among others. Finally, I discuss the properties of these UV-bright sources in the broad context of galaxy formation and evolution, and possible implications to cosmic reionization.
Bars are prominent features observed in most disc galaxies, having a crucial
within the galaxies, while rotating around the centre at a given angular frequency,
the bar pattern speed.
When formed in an isolated galaxy, a bar is expected to be born as fast rotating
with a bar rotation rate R (a parameter used to describe the bar pattern speed)
equal to 1.0 ≤ R ≤ 1.4. During its evolution, the bar can be slowed through the
exchange of angular momentum with the other components and/or when an efficient
dynamical friction is exerted by the dark matter (DM) halo. In this case, R is
shifted in the slow regime (R > 1.4), while the bar radius and strength are increasing.
On the other hand, ultrafast (UF) bars, with R < 1.0, are physically unstable.
Measuring the bar rotation rate becomes desirable both to investigate the secular
evolution of barred galaxies and to test whether the measured DM distribution matches
that predicted by cosmological simulations in the cold DM framework.
The only model-independent way to recover the bar pattern speed (and derive R) is
the Tremaine-Weinberg (TW) method, nowadays largely applied thanks to the advent
of integral-field spectroscopy: most of the analysed bars are compatible with the
fast regime, while a non-negligible fraction belongs to the unstable UF regime.
As a consequence, the question arises whether these results are biased by an
improper application of the method or instead they come from a not completely
theoretically understanding of the nature of slow/UF bars.
We explore the open questions on bar pattern speed with the TW method by
1. testing the reliability of the TW measurements which led to UF bars
2. pushing further the quest of slow bars applying the TW method to a sample of
dwarf galaxies, the best candidates to host slowly-rotating bars, since they are
commonly thought to host a massive and centrally-concentrated DM halo.
We measure the bar radius from the analysis of the maps tracing the transverse-to-radial
force ratio, showing that UF bars are no longer observed when the correct measurement
of the bar radius is adopted to derive R.
We apply the TW method to dedicated MUSE observations of a sample of 5 dwarf barred
suggests they could have been slowed down by a dense and massive DM halo.
Meeting ID: 885 2034 1620
Vimos Public Extragalactic Redshift Survey (VIPERS) is a spectroscopic survey designed to investigate the spatial distribution of ~90k galaxies on redshift 0.4<z<1.2. The catalogue of spectroscopic observations, combined with auxiliary photometric data, is perfect for evolutionary studies of different types of galaxies. But also for tracing rare objects. One of them are the so-called “red nuggets”, progenitors of the most massive galaxies in the local Universe. The discovery of red nuggets - highly massive, passive and extremely compact galaxies - at high redshift challenged the leading cosmological models, as they do not fit into the evolutionary paths of passive galaxies. Taking into account that the galaxies' mergers are stochastic events, it is possible that some red nuggets remain relatively unaltered for billions of years. Those survivors constitute a group of unique galaxies in the local Universe, commonly named “relics”. Despite numerous studies dedicated to red nuggets and relics, the link between the population of compact, massive, passive galaxies in the early Universe and their remnants in the local Universe, is still poorly understood.
In my talk I will present the first spectroscopically selected catalogue of red nuggets at the intermediate redshift. It is the most extensive catalogue of this kind of galaxies above redshift z > 0.5. Selected under the most strict criteria, the group of 77 objects consists of a statistically important sample, which allows for analysis of physical properties of those rare passive giants. I will discuss the influence of compactness criteria on the sample size. Moreover I will present VIPERS red nuggets number densities and discuss the environmental preferences of those exceptional galaxies.
The formation of the first galaxies in the Universe is the new frontier of both galaxy formation and reionization studies. In fact, we will soon directly observe primeval galaxies thanks to the James Webb Space Telescope, and witness the reionization process through 21cm intensity mapping experiments. This unique moment in human history creates a fierce new challenge, i.e. to simultaneously understand in a unique and coherent picture the processes of galaxy formation and reionization, and – crucially – their connection. The latter, in particular, has escaped past numerical efforts. In this talk I will present the first results on this front from an years-long effort geared toward achieving such comprehensive picture, culminated in the Thesan suite of cosmological radiation-magneto-hydrodynamical simulations. I will briefly introduce the features of Thesan, highlighting the successes and failures of its physical model. Thesan produces realistic galaxy populations thanks to state-of-the-art physics, including self-consistent dust production+destruction and radiation transport. I will then show how Thesan can, for the first time, reproduce the connection between IGM and galaxies, as measured from the modulation of the Lyman-alpha flux around galaxies. Finally, I will chart the way forward towards and even deeper understanding of the emergence of the first structures in the Universe.
The first Gigayears of our Galactic halo can be probed by using ancient stellar populations as traced by RR Lyrae stars. Today, with the advancement in our knowledge of RR Lyrae properties belonging to the Halo and to Milky Way satellite systems (Globular clusters and dwarf galaxies) we are able
to provide solid constraints on the link between these stellar systems. Here, we present some recent results concerning the Halo formation by using a detailed evolutionary analysis of RR Lyrae stars for which chemical abundances are available.
With the aim of detecting cosmological gas accretion onto galaxies of the local Universe, we examined the Ha emission in the halo of the 164 galaxies in the field of view of MUSE-Wide (Urrutia+19) with observable Ha (redshift < 0.42). An exhaustive screening of the Ha images led us to select 118 reliable Ha emitting gas clouds. To our surprise, around 38 % of the time the Ha line profile shows a double peak centered at the rest-frame of the corresponding galaxy. We have explored several physical scenarios to explain this Ha emission, among which accretion disks around rogue intermediate mass black holes (IMBHs) fit the observations best. I will describe the data analysis (to discard, e.g, instrumental artifacts and high redshift interlopers), the properties of the Ha emitting clumps (their fluxes, peak separation, and spatial distribution with respect to the central galaxy), and the arguments leading to the IMBH hypothesis rather than other alternatives (e.g., cosmological gas, expanding bubbles, or shocks in the circum galactic medium).
- A new, multi-cloud method to accurately model emission lines in star-forming galaxiesDr. Amirnezam AmiriTuesday April 11, 2023 - 12:30 GMT+1 (Aula)
- Women in AstrophysicsProf. Jocelyn BellThursday April 13, 2023 - 10:30 GMT+1 (Aula)