Structures, Masses, and Composition of High Redshift Star-Forming Galaxies
Sedona Price, Berkeley
Recent photometric and spectroscopic surveys have paved the way for detailed studies of galaxy evolution from when galaxies were most rapidly forming stars (z~2) to the current epoch. The combination of deep multi-band photometry and spectra has extended our understanding of the composition, structure, and masses of early star-forming galaxies. In particular, spectroscopic surveys provide key insights into galaxy masses and structures through their internal kinematics. Additionally, these surveys constrain the properties of dust in early galaxies, which is needed to infer accurate star formation rates. In this talk, I will present observations of the dust content, internal kinematics, and masses of star-forming galaxies at z~1.5-2.3, and how these properties change over time. I will also discuss how mock observations of cosmological simulations aid in the interpretation of structural and kinematic properties of distant galaxies and how they compare to late-time galaxy properties.
Luke Kelley, Harvard
Gravitational Waves (GW) from stellar-mass BH binaries have recently been observed by LIGO, but GW from their supermassive counterparts have remained elusive. Recent upper limits from Pulsar Timing Arrays (PTA) have excluded significant portions of the predicted parameter space. Most previous studies, however, have assumed that most or all Massive Black Hole (MBH) Binaries merge effectively and quickly. I will present results derived—for the first time—from cosmological, hydrodynamic simulations with self-consistently coevolved populations of MBH particles. We perform post-processing simulations of the MBH merger process, using realistic galactic environments, including models of dynamical friction, stellar scattering, gas drag from a circumbinary disk, and GW emission—with no assumptions of merger fractions or timescales. We find that despite only the most massive systems merging effectively (and still on gigayear timescales), the GW Background is only just below current detection limits with PTA. Our models suggest that PTA should make detections within the next decade, and will provide information about MBH binary populations, environments, and even eccentricities. I’ll also briefly discuss prospects for observations of dual-AGN, and the possible importance of MBH triples in the merger process.