Observational tests of the galaxy formation process

The mutual feedback between star formation and nuclear activity in large spheroidal galaxies may be a key ingredient to overcome several difficulties plaguing current semi-analytic models for galaxy formation. We discuss some observational implications of the model by Granato et al. (2003) for the co-evolution of galaxies and active nuclei at their centers and stress the potential of the forthcoming surveys of the Sunyaev-Zeldovich effect on arcminute scales, down to $\mu$K levels, to investigate the early galaxy formation phases, difficult to access by other means.Comment: 6, pages, 1 figure, to appear in proc. of the meeting "Baryons on Cosmic Structures", Roma, October 20-21, 200

Fitting the integrated Spectral Energy Distributions of Galaxies

Fitting the spectral energy distributions (SEDs) of galaxies is an almost universally used technique that has matured significantly in the last decade. Model predictions and fitting procedures have improved significantly over this time, attempting to keep up with the vastly increased volume and quality of available data. We review here the field of SED fitting, describing the modelling of ultraviolet to infrared galaxy SEDs, the creation of multiwavelength data sets, and the methods used to fit model SEDs to observed galaxy data sets. We touch upon the achievements and challenges in the major ingredients of SED fitting, with a special emphasis on describing the interplay between the quality of the available data, the quality of the available models, and the best fitting technique to use in order to obtain a realistic measurement as well as realistic uncertainties. We conclude that SED fitting can be used effectively to derive a range of physical properties of galaxies, such as redshift, stellar masses, star formation rates, dust masses, and metallicities, with care taken not to over-interpret the available data. Yet there still exist many issues such as estimating the age of the oldest stars in a galaxy, finer details ofdust properties and dust-star geometry, and the influences of poorly understood, luminous stellar types and phases. The challenge for the coming years will be to improve both the models and the observational data sets to resolve these uncertainties. The present review will be made available on an interactive, moderated web page (sedfitting.org), where the community can access and change the text. The intention is to expand the text and keep it up to date over the coming years.Comment: 54 pages, 26 figures, Accepted for publication in Astrophysics & Space Scienc

SHADES: THE SCUBA HALF DEGREE EXTRAGALACTIC SURVEY

SHADES is a new, major, extragalactic sub-mm survey currently being undertaken with SCUBA on the JCMT. The aim of this survey is to map 0.5 square degrees of sky at a depth sufficient to provide the first, major ( ≃ 300 source), unbiased sample of bright (S850 ≃ 8 mJy) sub-mm sources. Combined with extensive multi-frequency supporting observations already in hand, we aim to measure the redshift distribution, clustering and AGN content of the sub-mm population. Currently ≃ 40 % complete, the survey is due to run until early 2006. Here I provide some early example results which demonstrate the potential power of our combined data set, and highlight a series of forthcoming papers which will present results based on the current interim sample of ≃ 130 850µm sources detected within the Lockman Hole and SXDF SHADES survey fields. 1. Survey Rationale The sub-mm galaxy population continues to present a major challenge to theories of galaxy formation (e.g., Baugh et al. 2004, Somerville 2004), as current semi-analytic models cannot naturally explain the existence of a substantial population of dust-enshrouded starburst galaxies at high redshift. However, while now regarded as of key importance by theorists, the basic properties of sub-mm galaxies are not, in fact, well defined. Several redshifts have been measured (Chapman et al. 2003), some masses have been determined from CO observations (Genzel et al. 2004), and several individual SCUBA-selected galaxies have been studied in detail (e.g., Smail et al. 2003). However, these follow-up studies have had to rely on small, inhomogeneous, and often deliberately biased (e.g., lensed or radio pre-selected) samples of sub-mm sources, and until now no robust, complete, unbiased and statistically significant (i.e.,> 100 sources) sample of sub-mm sources has been constructed. SHADE