Expected progress and break-throughs inground-based extragalactic astronomy

Ralf BenderESO Council

FORS Deep Field

Achievements and Challenges 2003:

• Cosmological framework in which galaxies evolve is now sufficiently well determined.

• WMAP and Planck are determining the cosmological parameters with increasing accuracy.

• The main cosmological problems of the future are the nature of dark matter and dark energy. Attacking these in the astrophysical context requires both detailed studies of galaxies and clusters ( central dark matter density profiles) and large O/NIR/submm surveys ( nature of dark energy from SNIa, clusters; dark matter distribution from lensing).

Achievements and Challenges 2003 (continued):

• Evolution of cold dark matter ‘easy’ to model and seems understood at scales larger than galaxy size.

• Evolution of baryonic component complex and not at all well understood (difficult interplay between star formation, nuclear activity, different gas phases, collaps and merging).

• Stellar ages of galaxies in conflict with hierarchical formation? (massive galaxies are old, low mass galaxies young)

• Formation of supermassive black holes in galaxy centers in relation to galaxy formation/evolution still in the dark…

New capabilities on the ground and synergies with space observatories

• Imaging capabilites in optical/NIR will reach hundreds of megapixels (VST/OmegaCAM: 2004, VISTA: 2007) Multicolor optical-IR surveys enable reliable photometric redshifts and classifications for tens of millions of galaxies.

The evolution of type-dependent galaxy luminosity functions can be derived, cosmic variance can be analyzed, and targets for follow-up (e.g. spectroscopy) with large ground- based telescopes and satellites can be selected.

The dark matter distribution can be analyzed with the weak gravitational shear effect.

Variable objects (AGN, SNIa) can be searched efficiently.

Combination with surveys in X-rays, radio, submm, HST… opens new research opportunities ( Virtual Observatory)

• The spectroscopic survey capabilities for galaxy studies are increasing rapidly (FORS, ISAAC: 1998, VIMOS: 2003, FLAMES: 2003, KMOS, MUSE: 2009)

Evolution of large scale structure / galaxy clustering can be analyzed to high redshifts.

Intrinsic kinematics, stellar population properties, gas content and star formation activity of galaxies can be measured to highest z allowing to follow the mass assembly and morphology evolution over time.

Complementary observations by Hubble Space Telescope are crucial for detailed structural analysis (radii, densities, disk-to-bulge ratios …): GOODS, GEMS, COSMOS…

• Adaptive optics and laser beacons will increase the spatial resolution by a factor of ~3 over HST over tens of arcseconds (NACO, SINFONI: 2003, 2005)

Detailed structural and kinematical studies of merging and star-forming galaxies up to high redshift.

Analysis of physical conditions in Active Galactic Nuclei.

Search for inactive supermassive black holes in nearby galaxies.

Structure of star formation regions in nearby galaxies

(most of these fields up to now served by HST)

• VLT Interferometry of relatively faint sources will become possible through PRIMA and can provide spatial resolutions in the milliarcsec range: ~2007

In the Galactic center, the black hole parameters can be determined more accurately. General relativistic effects can be measured (precession of pericenter of stellar orbits)

Interferometry is the only way to study the dust tori around the central engines of Active Galactic Nuclei (the dust tori are expected to have a crucial influence on the nature of an AGN).

• ALMA will open a new window to sensitive, high resolution mm and sub-mm observations: >2007

ALMA can analyse the mm and submm continuum and thousands of molecular lines to characterize dust and gas in the universe (wavelength and spatial resolution complementary to Herschel).

ALMA will provide a view complementary to O/IR into the assembly of galaxies and dust-enshrouded violent star formation processes that may have produced a large fraction of all stars in the universe, especially those in spheroids.

ALMA will allow to probe the collapse of the first massive galaxy fragments before they have largely turned into stars.

ALMA can detect molecular absorption lines in many quasars, the Sunyaev-Zeldovich ( Planck) effect to high redshift, ...

• An ELT/OWL will lead into a new era of ground-based extragalactic astronomy because of its superb resolution and extreme light collecting power: >2012

High redshift universe can be studied in the same detail as the local universe today (e.g. SDSS at z~3 is possible).

High resolution spectra of intergalactic medium allow detailed analysis of chemical enrichment history.

Earliest phases of star and galaxy formation at z>7 (complementary to ALMA in wavelength and to JWST in resolution and light collecting power)

Systematic studies of large numbers of SNIa to constrain nature of dark energy.

Analysis of local galaxies as we analyse the Galaxy today (stellar populations, assembly history)

World-class facilities for extragalactic astronomy beyond 2010 (ground, space):

• 8-10m class O/IR telescopes– With adaptive optics & second generation instruments– Linked interferometrically (VLTI) – Supported by survey telescopes (VST, VISTA)

• ALMA, Herschel for mm/submm regime

• HST: UV, O, NIR; followed by JWST: O, NIR, MIR

• Extremely Large Telescopes (OWL?)

• LOFAR, and eventually SKA, for radio regime

• GAIA: spectroscopy and kinematics of the Milky Way

• High-energy observatories

What extragalactic astronomy may be

missing in UV/O/NIR capabilities: • Wide-field high spatial resolution UV/O satellite (SNAP?).

• The survey satellite for the low surface brightness universe:

SB ~ (1+z)-4 , i.e.

the central surface

brightness of the

Galaxy’s disk at

z ~ 3 is about

28 KAB/arcsec2!!

i.e., JWST can do

it, but a satellite

like PRIME or WISE

is more efficient.