Tue 19 Mar 14:00: Primordial black holes in the dark matter halo of our Galaxy
If there are primordial black holes in the dark matter halo, they must collide with the Galactic neutron stars (NSs) and produce light black holes (LBHs), with masses below 1.4 M_Sun. This has observational consequences that may be checked by microlensing, by LIGO -Virgo-Kagra interferometers detecting gravitational waves from collisions of LBHs with NSs and BHs, and (possibly) by detecting LBHs in X-ray binaries and from pulsars statistics.
- Speaker: Prof. Marek Abramowicz
- Tuesday 19 March 2024, 14:00-15:00
- Venue: The Hoyle Lecture Theatre + Zoom .
- Series: Institute of Astronomy Seminars; organiser: .
Wed 13 Mar 13:15: A new convection scheme for exoplanet atmospheres
Convection is an essential process for transporting heat and moisture in planetary atmospheres. The standard Earth picture of moist convection rising from the surface is only one of a number of modes of convection. Notably, convection in atmospheres with a high condensible mass fraction (non-dilute atmospheres), or with a lighter background gas than the condensible species (e.g. water convection in a hydrogen dominated atmosphere) – acts very differently and can be much weaker or even shut down entirely in the latter case. Here I present a new mass-flux scheme which can capture these variations and simulate convection in a wide range of parameter space for use in 3D climate models. A validation using the case of Trappist-1 e is presented.
- Speaker: Edouard Barrier (University of Cambridge)
- Wednesday 13 March 2024, 13:15-13:40
- Venue: The Hoyle Lecture Theatre + Zoom .
- Series: Institute of Astronomy Seminars; organiser: Hannah Uebler.
Wed 13 Mar 13:40: Constraining physics and astrophysics with multifrequency CMB data
The CMB anisotropies are measured in several microwave frequency bands. Having this frequency information allows us to separate signals that are due to different sources. We can easily make maps that are sensitive to specific frequency combinations, and in this way isolate the contribution from the primary CMB (early-Universe) and various other CMB interactions such as the Sunyaev—Zel’dovich (SZ) effect (the scattering of the CMB from electrons in the late Universe). I will talk about constraints on the SZ effect from Planck data using a new frequency-separation code, pyilc, which we use to isolate the signal while removing other late-Universe biases, in particular the infrared emission from star-forming galaxies. I will also show an application to beyond standard model interactions between the CMB and a non-trivial dark sector, and how we can use the CMB to constrain beyond-standard-model particle physics.
- Speaker: Fiona McCarthy (DAMTP)
- Wednesday 13 March 2024, 13:40-14:05
- Venue: The Hoyle Lecture Theatre + Zoom .
- Series: Institute of Astronomy Seminars; organiser: Hannah Uebler.
Wed 06 Mar 13:15: The Nature of Dark Matter with Lyman-Alpha Forest
The existence of dark matter, which constitutes 85% of the matter density and 26% of the total energy density, is clearly demonstrated by cosmological observations of the Universe. And yet, very little is known about the nature of dark matter. The observations support the ‘cold dark matter’ (CDM) paradigm, in which the dark matter is a heavy particle, with little to no interactions through fundamental forces other than gravity. The cosmological and astrophysical observations of dark matter’s gravitational interaction currently provide the only robust evidence of dark matter. These observations typically rely on characterising the distribution of matter in the Universe. A dark matter particle that is lighter than the standard CDM paradigm predicts imprints a suppression of structure in the matter distribution. The exact scale where this happens is most often linked to the mass of the dark matter particle. I will present new results on the thermal relic warm dark matter constraints using the high-redshift cosmic web as traced by the Lyman-alpha forest.
- Speaker: Vid Iršič
- Wednesday 06 March 2024, 13:15-13:40
- Venue: The Hoyle Lecture Theatre + Zoom .
- Series: Institute of Astronomy Seminars; organiser: .