Description

Nearby Galaxies

Studies of nearby galaxies at Yale range from studies of Local Group galaxies (lead by Marla Geha) to cluster galaxies, particularly in the Virgo cluster (Jeffrey Kenney).

Marla Geha's group studies dwarf galaxies associated with the Milky Way and M31, with the aim of understanding their dark matter content and their role in structure formation. Among recent results is the finding that these small galaxies have a very high dark matter content, which implies that their overall mass density is in better agreement with theoretical models than was previously thought. The main tool in this work is multi-object spectroscopy on 6m-10m class telescopes.

Jeffrey Kenney focuses on the effects that galaxy clusters have on their constituent galaxies. Through extensive observations (particularly with the 3.5m WIYN telescope) of galaxies in Virgo, Kenney's group as mapped and studied the interaction of galaxies with the intra-cluster medium and with other cluster galaxies.

High Redshift Galaxies

Priya Natarajan is a theoretical cosmologist, who has a strong interest in galaxy formation and evolution. The focus is on the distribution and properties of dark matter, which makes up ~90% of a galaxy's mass but is still not understood. Using weak lensing measurements the dark matter can be mapped in clusters of galaxies, and its distribution can be directly compared to models.

van Dokkum's group studies the formation and evolution of galaxies, using large telescopes on the ground and in space. The focus is on the most massive galaxies, as they provide strong constraints on galaxy formation models. Several programs are underway, including a 64-night program with the Kitt Peak 4m telescope using the new NEWFIRM near-infrared camera. A recent result is that massive galaxies at z~2.5 (when the Universe was less than 3 billion years old) are surprisingly compact, having sizes 5x smaller than present-day galaxies. This result was obtained with the Hubble Space Telescope and the 10m Keck telescope on Hawaii.

Evolution of Active Galactic Nuclei

Meg Urry's group studies the demographics and properties of active galactic nuclei and their host galaxies. Deep multiwavelength surveys like MUSYC, GOODS, and COSMOS reveal that most black hole accretion is obscured, identifiable only from infrared and hard X-ray signatures. Continuing work addresses the relation between galaxy evolution and black hole growth. Urry's group also studies relativistic jets and blazars (with Coppi and Bailyn), including projects with Chandra, Hubble, Spitzer, and GLAST.

Galaxy Formation

Prof. Frank van den Bosch and his group study the formation and evolution of galaxies using (semi)-analytical models, galaxy group catalogues, and numerical simulations of structure formation.
Prof. van den Bosch uses state-of-the-art analytical models for the formation of disk galaxies to investigate how disk galaxies acquire their angular momentum, how they evolve with redshift, and how they regulate their star formation and gas accretion. Using a large galaxy group catalogue, extracted from the Sloan Digital Sky Survey, Prof. van den Bosch and his group are investigating how galaxy properties correlated with environment (group mass). A main focus of their research is to constrain which physical mechanisms are responsible for quenching the star formation of satellite galaxies and central galaxies. Prof. van den Bosch is also a member of the LasDamas collaboration, which uses a large suite of dark matter simulations in order to study the formation, structure and clustering of dark matter haloes.