Science Goals for ALMA

The power of ALMA will enable new science in many areas, examples of which are highlighted below. The design of the instrument is being driven by three key science goals:

  1. Detect spectral line emission from CO or CII in a normal galaxy like the Milky Way at a redshift of z = 3, in less than 24 hours of observation.
  2. Image the gas kinematics in protostars and in protoplanetary disks around young Sun-like stars at a distance of the nearest star-forming clouds. This will enable the study of their physical, chemical and magnetic field structures and the detection of the tidal gaps created by planets undergoing formation in the disks.
  3. Provide precise images at an angular resolution of 0.1 arcsec. Here the term "precise image" means being able to represent, within the noise level, the sky brightness at all points where the brightness is greater than 0.1% of the peak image brightness.

These three goals drive the large collecting area, the spectral capabilities, and the number of elements of ALMA, as detailed in ALMA Scientific Specifications and Requirements.

What this Instrument further can do

This remarkable instrument will be able to:

  • Image the redshifted dust continuum emission from evolving galaxies at epochs of formation as early as z = 10. The inverse K-correction on the Rayleigh-Jeans side of the spectral energy distribution of a dusty galaxy compensates for dimming at high redshift, making ALMA the ideal instrument for investigating the origins of galaxies in the early universe, with confusion minimized by the high spatial resolution.
  • Use the emission from CO to measure the redshift of star-forming galaxies throughout the universe. The spacing between successive transitions of CO shrinks with redshift as (1 + z), and the large instantaneous total bandwidth of ALMA will make possible blind surveys in order to establish the star-forming history of the universe, without the uncertainties inherent in optical and UV studies caused by dust extinction.
  • Probe the cold dust and molecular gas in nearby galaxies, allowing detailed studies of the interstellar medium in different galactic environments, the effect of the physical conditions on the local star formation history, and galactic structure. The resolution of ALMA will reveal the kinematics of obscured active galactic nuclei and quasars on spatial scales of 10-100 pc, and will be able to test unification models of Seyfert galaxies.
  • Image the complex dynamics of the molecular gas at the center of our own Galaxy with unprecedented spatial resolution, thereby revealing the tidal, magnetic, and turbulent processes that make stellar birth and death at the Galactic Center more extreme than in the local Solar neighborhood.
  • Reveal the details of how stars form from the gravitational collapse of dense cores in molecular clouds. The spatial resolution of ALMA will allow the accretion of cloud material onto an accretion disk to be imaged, and will trace the formation and evolution of disks and jets in young protostellar systems. For older protostars and pre-main sequence stars ALMA will show how planets form, sweeping gaps in circumstellar and debris disks.
  • Uncover the chemical composition of the molecular gas surrounding young stars, including establishing the role of the freeze-out of gas-phase species onto grains, the re-release of these species back into the gas phase in the warm inner regions of circumstellar disks, and the subsequent formation of complex organic molecules. ALMA will have the large total bandwidth, high spectral resolution, and sensitivity needed to detect the myriad of lines associated with heavy, pre-biotic molecules such as those which may have been present in the young Solar System.
  • Image the formation of molecules and dust grains in the circumstellar shells and envelopes of evolved stars, novae, and supernovae. ALMA will resolve the crucial isotopic and chemical gradients within these circumstellar shells, which reflect the chronology of the invisible stellar nuclear processing.
  • Refine dynamical and chemical models of the atmospheres of planets in our own Solar System, and provide unobscured images of cometary nuclei, hundreds of asteroids, Centaurs, and Kuiper Belt Objects.

A Taste of the Scientific Potential of ALMA

More information on the scientific capabilities of ALMA can be found at the following locations:

Further Information