Narrow Results

Using the deepest and most complete observations of distant galaxies, we investigate the progenitors of present-day large spirals. Observations include spatially-resolved kinematics, detailed morphologies and photometry from UV to mid-IR. Six billion years ago, half of the present-day spirals were starbursts experiencing major mergers, evidenced by their anomalous kinematics and morphologies. They are consequently modeled using hydrodynamic models of mergers and it perfectly matches with merger rate predictions by state-of-the-art-ΛCDM semi-empirical models. Furthermore imprints in the halo of local galaxies such as M31 or NGC5907 are likely caused by major merger relics. This suggests that the hierarchical scenario has played a major role in shaping the massive galaxies of the Hubble sequence. Linking galaxy properties at different epochs is the best way to fully understand galaxy formation processes and we have tested such a link through generated series of simulations of gas-rich mergers. Mergers have expelled material in galactic haloes and beyond, possibly explaining 60% of the missing baryons in Milky-Way (MW) mass galaxies. A past major merger in M31 might affect drastically our understanding of Local Group galaxies, including MW dwarves. We also propose future directions to observationally constrain the necessary ingredients in galaxy simulations.

Dark energy is the largest fraction of the energy density of our universe — yet it remains one of the enduring enigmas of our times. Here we show that dark energy can be used to solve 2 tantalizing mysteries of the observable universe. We build on existing models of dark energy linked to neutrino masses. In these models, dark energy can undergo phase transitions and form black holes. Here we look at the implications of the family structure of neutrinos for the phase transitions in dark energy and associated peaks in black hole formation. It has been previously shown that one of these peaks in black hole formation is associated with the observed peak in quasar formation at redshifts $z\sim 2.5$. Here, we predict that there will also be an earlier peak in the dark energy black holes at high redshifts $z\sim 18$. These dark energy black holes formed at high redshifts are Intermediate Mass Black Holes (IMBHs). These dark energy black holes at large redshift can help explain both the EDGES observations and the observations of large Supermassive Black Holes (SMBHs) at redshifts of 7 or larger. This work directs us to actively look for these dark energy black holes at these high redshifts as predicted here through targeted searches for these black holes at the redshifts $z$ near 18. There is a slight dependence of the location of the peak on the lightest neutrino mass. This may enable a measurement of the lightest neutrino mass — something which has eluded us so far. Finding these dark energy black holes of Intermediate Mass should be within the reach of upcoming observations — particularly with the James Webb Space Telescope — but perhaps also through the use of other innovative techniques focusing specifically on the redshifts $z$ around 18.