Rationale

The key topics for this meeting are:

  • Properties of emergent galaxies in the early Universe (e.g. star-formation rates, ages, metallicities, masses, sizes)
  • Interplay between gas and star formation at z>1
  • Growth of black holes at z>1, interaction of AGN with the interstellar medium
  • Origin of the Hubble sequence and evolution of galaxy morphology
  • Confrontation of observations and galaxy-formation models
  • Linking studies of early galaxies with the existing literature at z<1, to construct a coherent picture of galaxy evolution over ~90% of cosmic time
  • Exploitation of new and future facilities
  • Key post-2015 goals and challenges

Over the last two decades, a convergence of powerful observational facilities  and high-performance computing has significantly advanced our understanding of  galaxy evolution. Detailed empirical studies have quantified the evolution of  galaxy properties (particularly over the latter half of cosmic time) and  theoretical models, within the framework of the LCDM paradigm, have met with  significant success in reproducing these properties.

While our knowledge is still dominated by work in the nearby (z<1) Universe, an  explosion of multi-wavelength data at high redshift is revolutionising our  understanding of emergent galaxies at z>1. Since the bulk of the cosmic  stellar-mass assembly and black-hole growth takes place at these redshifts  (both peaking around z~2), answers to basic questions at these epochs are central to a complete understanding of galaxy evolution. For example, what  processes drove the growth of early stellar populations and black holes? How  did interactions between galaxies and their constituent black holes shape the  Universe we see today? How did the morphological mix of the visible Universe  evolve into today’s Hubble sequence? How well do our current theoretical models  reproduce the properties of galaxies in the early Universe?

Recent and ongoing studies are delivering a dramatic improvement in our  understanding of these fundamental questions. HST surveys like CANDELS,  combined with facilities like Spitzer and Herschel, are now constraining galaxy  parameters, such as star-formation rates, ages, metallicities, masses and  sizes, to z~2 and beyond. Together with deep Chandra observations, these data are probing the co-evolution of young galaxies and their black holes, and the  critical role of AGN-driven jets in producing negative feedback, that quenches  star formation and influences the morphology of galaxies at early epochs. High-resolution near-infrared imaging from the HST is quantifying the origin  and evolution of the Hubble sequence in the early Universe, allowing us to  probe the evolving morphological mix of the visible Universe over cosmic time.  In parallel, near-infrared integral-field spectrographs on 10m class telescopes  such as SINFONI and OSIRIS, together with facilities like IRAM, are enabling  detailed spatially-resolved studies of the kinematics, star formation and  molecular gas in significant samples of early galaxies, yielding crucial insights into what drives the assembly of the stellar populations that dominate  our Universe today. This growing empirical literature is motivating an array of  theoretical work, in particular high-resolution hydro-simulations, which are elucidating the cosmic drivers of stellar-mass buildup, black-hole growth and  morphological transformations with unprecedented accuracy.

Our current understanding of galaxy evolution will shortly be bolstered by new  instruments with multiplexing capabilities, such as KMOS, MUSE and MOSFIRE, and  those that offer high-resolution imaging in the long-wavelength regime, such as  ALMA and the SKA precursors (e-MERLIN, LOFAR, etc.). These will enable  unprecedented studies of stellar and gas kinematics at high redshift, and allow  us to investigate the poorly-understood interplay between gas and star  formation in the early Universe. In addition, the unprecedented depth and  resolution of the e-ROSITA X-ray mission will offer transformational insights  into large-scale structure and AGN across cosmic time. Looking further ahead to the turn of the decade, the field is poised for yet  another revolution, both in terms of the ground-breaking depth and area offered  by future imaging and spectroscopic surveys (e.g. LSST, Euclid, 4MOST, MOONS),  and our ability to comprehensively probe galaxy evolution all the way up to the  epoch of reionization, using instruments like the JWST and the ELTs.

The time will be ripe in 2015 for bringing together the wealth of empirical and  theoretical studies that are leveraging today’s instruments, and setting the stage  for the exploitation of new and forthcoming facilities. For example, the  interpretation of current multi-wavelength survey data (e.g HST programmes like  CANDELS, Herschel programmes like HerMES, etc.) will be mature, and large sets of data will be  available from new instruments such as KMOS, ALMA and e-MERLIN. In the same  vein, while theoretical simulations are just starting to produce realistic  assembly histories for galaxies in the early Universe, more accurate analyses are expected  between now and 2015 (possibly revealing new questions and challenges).