Galaxy Structure and Evolution
ICCUB research in this area includes both galactic and extragalactic astronomy:
Galactic astronomy
Galactic astronomy is the study of the Milky Way. Our Galaxy is a complex system, a late type spiral, with major structural elements, namely the bar and bulge, the halo and both the thick and thin disks. The majority of the mass of the Galaxy is contained within the dark matter halo —clues as to this can be found in measurements of the globular clusters in the halo and, more generally, the dynamics of stars in the latter. Our Galaxy is a rich laboratory where we can explore how stars and galaxies form, how they evolve, and what processes shape their current forms. Stars harbour planets, and our planetary system provide pointers to extra-solar worlds. Making linkages from the local solar neighbourhood, to planetary systems, open clusters, the disk or to our galaxy as a whole, is the key to our understanding of the wider evolution of the Universe — from the Big Bang to its eventual cold and lonely demise. [+]
Understanding the formation and evolution of galaxies is of fundamental importance in the study of modern astrophysics. Observations of the most distant galaxies give us valuable information on the epoch at which these systems were formed. However, only our own galaxy provides a fossil record detailed enough to unravel its complete formation history. Current cosmological models envisage the formation of large galaxies through the merging of smaller structures. Deciphering the assembly history of our Galaxy requires a detailed mapping of the structure, dynamics, chemical composition, and age distribution of its stellar populations. Ideally one would like to “tag” individual stars to each of the progenitor building blocks, and relate this to the structure of the gas, dust and magnetic fields, which combine to shape the galaxy. Stars record the past in terms of their age, chemistry, and kinematics. Identifying and studying stellar streams, from the knowledge of phase-space distributions, can aid in determining the accretion history and future dissolution of stellar clusters. The study of the various components of the Milky Way (e.g. bulge, disk, and halo) can help decipher the assembly mechanisms in the Galaxy, and reveal, for instance, the relative importance of early mergers compared to later accretion events or internal bursts of star formation.
Extragalactic astronomy
Extragalactic astronomy is concerned with everything that lies beyond the domain of galactic astronomy (i.e. the Milky Way). This includes a large array of objects and phenomena ranging from galaxies to superclusters and spanning the last 13 billion years of the history of the Universe. This makes extragalactic astronomy a fertile ground for the merging of many branches of physics (mainly high energy physics and cosmology). [+]
An important extragalactic and cosmological issue which deserves much attention is the origin of galaxies, the building blocks of the universe. Almost one century after their discovery, there are still important aspects in their formation and evolution which are poorly understood and much effort is being made in this field both in the theoretical and the observational domains. It is nowadays believed that the galaxy formation process, a highly non-linear process involving complicated baryon physics on a very wide range of scales, is greatly influenced by feedback effects which are hard to handle, such as the ionizing flux emitted by the first generation (Population III) stars, the heating of the intergalactic medium (IGM) by active galactic nuclei powered by super-massive black holes (SMBH) located at the galaxy centers, and galaxy interactions.
ICCUB Contribution
Galactic astronomy
Research in galactic astronomy at the ICCUB includes three main lines of research: galaxy modeling, the study of stellar constituents and stellar luminosity calibration. At present, this research is highly influenced by the preparation of the scientific exploitation of the Gaia mission, in which ICCUB researchers are deeply involved (see the GAIA Mission link for more information). [+]
Understanding the Milky Way as a holistic system is one of the key challenges astrophysicists will face in the coming decade. ICCUB’s contribution to galaxy modeling is directed towards a better understanding of the origin and evolution of the large structures in the galactic disk —bar, spirals and warp— and the archaeology of the Milky Way —missing satellites—, through an in-depth investigation of the dynamics and chemistry of the system.
On the other hand, the study of the stellar constituents of the Galactic disk and halo focuses on two central aspects: 1) where do the stars form and 2) what are their astrophysical properties. The Gaia mission will provide us with a detailed interpretation of the phase space data in terms of specific events that have shaped the Milky Way. ICCUB’s contribution is organized around two central goals: a) to provide new insights into the popular scenario that all stars have formed in clusters, i.e. to investigate cluster formation and evolution, and b) to capitalize on the opportunities that Gaia brings to the study of variable stars’ data. ICCUB is also involved in the Gaia-ESO Spectroscopic survey (300 nights of observations in 5 years) to acquire complementary data for Gaia stars.
The Gaia satellite will have a dramatic impact on the definition of the cosmic distance scale, providing the direct measurement, via parallaxes, of the local primary distance indicators and, in turn, a direct re-calibration of the secondary distance indicators. This will significantly improve our estimate of the Hubble constant. At the same time Gaia will offer a unique opportunity to assess the systematics affecting the various indicators contributing to the cosmic distance scale as well as to establish new standard candles. ICCUB is working on stellar luminosity calibration in order to develop the necessary tools to achieve these goals.
Extragalactic astronomy
ICCUB’s interest in galactic astrophysics extends beyond the Milky Way and is concerned, too, with the formation of the first galaxies, which were formed from pristine matter. They comprised population III stars, which reionised the intergalactic medium, polluted it with metals and left behind the seeds of SMBHs. These are processes currently being modeled at ICCUB. [+]
Detailed analytical models and huge numerical simulations are being developed, which make use of the most powerful computational tools presently available. The resulting predictions are confronted with the latest, progressively complete, observations drawn from huge wide angle (all-sky) nearby galaxy surveys (e.g. SDSS, 2dF) as well as very deep, high-redshift, ones (e.g. Hubble Deep Field, GROTH, DEEP2), carried out by means of the new generation of very large ground-based telescopes and sophisticated detectors on board of satellites covering the whole electromagnetic spectrum, from gamma to radio wavelengths.
Lines of Research
- Semianalytical and numerical modeling of galaxy formation and evolution
- Dark matter clustering and halo structure and kinematics
- Galaxy evolution in groups and clusters
- Kinematics and structure of the galaxy
- Data reduction of the GAIA mission
Members
