Found 15 talks width keyword galactic halos

Thursday June 15, 2023


Using CGMS deep integral field data we have discovered that the massive galaxy NGC 1277 has no dark matter. This is the first time that a galaxy as massive as the Milky Way or more is found to be dark matter deficient. This result is unexpected within the Lambda-CDM cosmological paradigm. We propose several alternatives to explain this intriguing observation but none is completely satisfactory, so the mystery about how to generate a galaxy without dark matter remains.


ID: 818 9512 1297

Passcode: 460746


Friday May 26, 2023
Universidad Nacional Autonoma de Mexico


We present the extended data release of the Calar Alto Legacy Integral Field Area (CALIFA) survey (eDR). It comprises science-grade quality data for 895 galaxies obtained with the PMAS/PPak instrument at the 3.5 m telescope at the Calar Alto Observatory along the last 12 years, using the V500 setup (3700-7500Å, 6Å/FWHM) and the CALIFA observing strategy. It includes galaxies of any morphological type, star-formation stage, a wide range of stellar masses ( ∼10^7-10^12 Msun), at an average redshift of  ∼0.015 (90\% within 0.005 < z <0.05). Primarily selected based on the projected size and apparent magnitude, we demonstrate that it can be volume corrected resulting in a statistically limited but representative sample of the population of galaxies in the nearby Universe. All the data were homogeneously re-reduced, introducing a set of modifications to the previous reduction. The most relevant is the development and implementation of a new cube-reconstruction algorithm that provides an (almost) seeing-limited spatial resolution (FWHM PSF  ∼1.0").  Furthermore we present the analysis performed using the pyPipe3D pipeline for these dataset. We include a description of (i) the analysis performed by the pipeline, (ii) the adopted datamodel for the derived spatially resolved properties and (iii) the catalog of integrated, characteristics and slope of the radial gradients for a set of observational and physical parameters derived for each galaxy. All these data has been distributed through the following webpage:

Thursday May 25, 2023


One of the most active areas of research of the last decade is undoubtedly the study of the effects of baryons on the observed dynamics of galaxies. This particularly led to the establishment of some fundamental scaling relations, which characterise the dependence of the abundance of baryons on the properties of galaxies' dark matter haloes. Among these fundamental relations, the stellar–to-halo mass relation appears to be one of the most investigated.
In this talk, I will present the less commonly explored neutral hydrogen-to-halo mass relation constructed using high-quality extended HI rotation curves of isolated rotationally-supported disk galaxies, selected from the SPARC and LITTLE THINGS databases. I will discuss how we constrain the dark matter halo of these galaxies using a Navarro-Frenk-White cuspy density profile and a semi-analytic Dekel-Zhao density profile and how we investigate the scaling relations between baryons and halo parameters.

Tuesday March 7, 2023
Kapteyn Institute at the University of Groningen


Only recently, thanks to the Gaia, have we been able to directly measure how our own Galaxy was formed since its infancy, by cannibalizing smaller galaxies formed at the core of dark matter subhalos. These accretion events can be seen as kinematic groups and may have brought their own group of globular clusters, some of which are only seen today as their remnant cold stellar streams. Here I will discuss how the main accretion events unveiled by Gaia can be linked to previously known halo substructures, mainly large stellar clouds identified more than a decade ago in large photometric surveys. Additionally I will discuss the Jhelum stellar stream in the light of its interaction with the Sagittarius stream, which can give us insight on the details of this ongoing accretion event. Finally, I will briefly discuss how the new Gaia XP DR3 spectra is aiding in  the identification of metal-poor unmixed halo substructures in the solar neighbourhood, highlighting the case of ED-2, a [Fe/H] = -2.5 cold stellar stream in which the Sun is embedded in. 

Finally, I will briefly discuss how the new Gaia XP DR3 spectra is aiding in  the identification of metal-poor unmixed halo substructures in the solar neighbourhood, highlighting the case of ED-2, a [Fe/H] = -2.5 cold stellar stream  in which the Sun is embedded in.

Tuesday May 24, 2022
Weizmann Institute


Gravitational dynamical friction affecting the orbits of globular clusters (GCs) was studied extensively as a possible formation mechanism for nuclear star clusters in galaxies. In well-known examples that showcase this phenomenon, like the Milky Way and M31 galaxies, the medium which affects the dynamical friction is dominated by bulge stars. In comparison, the case for dynamical friction in dark matter-dominated systems is much less clear. A puzzling example is the Fornax dwarf galaxy, where the observed positions of GCs have long been suspected to pose a challenge for dark matter, dynamical friction theory, or both. We search for additional systems that are dark matter-dominated and contain a rich population of GCs, offering a test of the mechanism. A possible example is the ultra diffuse galaxy NGC5846-UDG1: we show that GC photometry in this galaxy provide evidence for the imprint of dynamical friction, visible via mass segregation. If confirmed by future analyses of more GC-rich UDG systems, these observations could provide a novel perspective on the nature of dark matter.

Thursday May 19, 2022


Black hole feedback is central to our theoretical understanding of galaxies. The energy and momentum radiated by growing supermassive black holes is expected to regulate the baryonic cycle, in particular, within massive dark matter halos, modulating gas cooling and thus star formation. Observational evidence of the role of black hole feedback remains, however, scarce, casting serious doubt on our current galaxy formation modelling. In this talk I will summarize our recent efforts trying to empirically characterize the effect of black hole feedback on galactic scales. I will describe how the combination of detailed stellar population analysis and well-known scaling relations can be used to actually constrain the physical processes behind black hole feedback. Moreover, I will also present evidence of black hole feedback acting beyond the host galaxy, further supporting the importance of black hole feedback in regulating the evolution of galaxies.

Thursday April 21, 2022


Recent years have seen impressive development in cosmological simulations for spiral disc galaxies like the Milky Way. I present a suite of high-resolution magneto-hydrodynamic simulations that include many physical processes relevant for galaxy formation, including star formation, stellar evolution and feedback, active galactic nuclei and magnetic fields. I will discuss how these processes affect the formation of galactic discs, and what these simulations can tell us about the formation of the Milky Way, such as the properties of the Galaxy's putative last significant merger and its effect on the formation of the thick disc and stellar halo. 

Thursday March 17, 2022
ICC Durham



The hierarchical nature of structure formation predicts that haloes grow by the aggregation of several lower-mass "clumps". A natural consequence of this process is the existence of an extended halo of stars surrounding galaxies, which is built up from the debris of destroyed lower mass objects. The nature of these haloes has been studied extensively from Milky Way to cluster-mass systems. However, the stellar haloes of dwarf galaxies have been given relatively little attention.  In this talk, I will discuss recent work using N-body cosmological simulations and empirical galaxy models to study the  build-up of stellar haloes surrounding dwarf galaxies. We find that the galaxy formation model parameters, namely the stellar mass-halo mass relation and the galaxy occupation fraction, strongly influence the stellar mass accreted onto dwarf galaxies. Moreover, the type of dark matter can also be important, as minor mergers are greatly suppressed in warm dark matter models. Finally, I will discuss the observational implications of these results, and the future prospects for constraining small-scale models with observational probes.





Thursday May 13, 2021
Imperial College


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.

Thursday June 25, 2020
University of Southampton


It has been claimed for decades that almost all galaxies in the local Universe host at their centre a supermassive black hole (SMBH) the mass of which appears to be tightly correlated with the stellar mass and the random motion ("velocity dispersion", sigma) of the stars in the host galaxy. In this talk I will first review the state of the art in this field. I will then highlight that significant biases affect local black hole-galaxy correlations.  I will specifically show that the majority of quiescent early-type galaxies with central black hole dynamical mass estimates have significantly higher velocity dispersions than local typical galaxies of similar stellar mass. Through aimed Monte Carlo simulations, residual analysis, and the comparison with latest AGN clustering measurements, I will then illustrate that present data sets of active and quiescent galaxies strongly favour on average lower SMBH masses than previously thought, and point to velocity dispersion as more ``fundamental'' than galaxy stellar mass, galaxy size or Sérsic index. I will then move on discussing the main implications of these findings, in particular: 1) The implied black hole radiative efficiencies and obscured fractions; 2) the consequences on feedback from active black holes and SMBH binary gravitational waves; 3) the connection to cosmological models that rely on velocity dispersion, rather than stellar mass, as main driver of black hole growth.

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