Research

Young stars are generally surrounded by dust and gas discs from which they accrete material and grow in mass. These discs are supposed to be the site where planet formation occurs. I am interested in the hydrodynamics of such discs, with emphasis on the role of gravitational instabilities in redistributing angular momentum and favouring accretion. I have also studied the effect of such instabilities in the formation of planetesimals (the building blocks of planets) and possibly of the planets themselves.

Recent relevant papers:

1.The effects of opacity on gravitational stability in protoplanetary discs, by Cossins, Lodato & Clarke, MNRAS, in press (2009)
2.Limits on the location of planetesimal formation in self-gravitating protostellar discs, by Clarke & Lodato, MNRAS, 398, L6 (2009)
3.Chaotic star formation and the alignment of stellar rotation with discs and planetary orbital axes, by Bate, Lodato & Pringle, MNRAS, in press (2009)
4.Eccentricity growth of planetesimals in a self-gravitating protoplanetary disc, by Britsch, Clarke and Lodato, MNRAS, 385, 1067 (2008)

I study several dynamical processes occuring within accretion discs. In particular, I am interested in the development of gravitational instabilities, and in assessing their role in the process of angular momentum transport within the disc.

I am also interested in the evolution of warped accretion discs. A spinning black hole exerts a relativistic torque on matter whose orbital plane is inclined with respect to the equatorial plane of the black hole. This causes the orbits of rotating matter to precess around the black hole spin axis. An accretion disc around such a spinning black hole will therefore attain a warped shape. I am studying the consequences of this warping process on the secular evolution of the black hole - accretion disc system and on observables from Active Galactic Nuclei.

I am also running large numerical simulations to determine accurately the speed at which such warps propagate in a thin and viscous disc.

Recent relevant papers:

1.Characterizing the gravitational instability in cooling accretion discs, By Cossins, Lodato & Clarke, MNRAS, 393, 1157 (2009)
2. Warp diffusion in accretion discs: a numerical investigation, by Lodato & Pringle, MNRAS, 381, 1287 (2007)
3.The evolution of misaligned accretion discs and spinning black holes, by Lodato & Pringle, MNRAS, 368, 1196 (2006)

In order to power the AGN which are observed at very large red-shifts, supermassive black holes have to form very early on, when the Universe was very young. I have developed a model for the formation of the seeds of such SMBH at large redshift. This model relates their properties (like their mass) to the properties of the dark matter halo inside which they are formed. These model can be used to determine the abundance of such seeds and their mass distribution.

I also study other growth processes for black holes, such as mergers with other black holes (which might provide an important mechanism for the production of gravitational waves, that can be observed by upcoming missions such as LISA) and tidal disruption of stars in the vicinity of the black hole.

Recent relevant papers:

1. Black hole mergers: the first light, by Rossi, Lodato, Armitage, King & Pringle, MNRAS, in press (2009)
2. Black hole mergers: can gas discs solve the `final parsec’ problem?, by Lodato, Nayakshin, King & Pringle, MNRAS, 398, 1392 (2009)
3. Stellar disruption by a supermassive black hole: is the lightcurve really proportional to t^(-5/3)?, by Lodato, King & Pringle, MNRAS, 392, 332 (2009)
4. The evolution of massive black hole seeds, by Volonteri, Lodato and Natarajan, MNRAS, 383, 1079 (2008)
5. The mass function of high redshift seed black holes, by Lodato and Natarajan, MNRAS, 377, L64 (2007)
6. Supermassive black hole formation during the assembly of pre-galactic discs, by Lodato & Natarajan, MNRAS, 371, 1813 (2006)