sei ENCEWITHTHEV LTI VLTI I The Early Universe with the VLT HIGHLIGHTS OF THE ESO WORKSHOP, APRIL 1-4,1996

A. RENZINI, ESO

Progress in science is not a steady Redshift Survey that was presented by of finding high-redshift galaxies was il­ process. Occasionally, when a funda­ F. Hammer. Beyond z = 1, one now has lustrated by Y. Mellier, who advocated mental breakthrough takes place, the a set of lower limits established by HOF strong gravitational lensing by massive frontier of our knowledge of Nature and Keck spectroscopic data. These lim­ clusters offering the advantage of ampli­ moves suddenly ahead more than it had its are likely to move up somewhat as fying the light of distant galaxies, thus in years before. Those who last April at­ new data will soon become available, helping their detailed study. tended in Garching the workshop ''The with the expectation that in a few years While the very high redshift galaxies Early Universe with the VLT" were left the whole diagram will be filled all the played the primadonna role at the meet­ with the feeling that one of these quan­ way to z = 5 with determinations as ac­ ing, very impressive was also the tum jumps is indeed taking place right cu rate as those now available for z ~ 1. progress of systematic studies of the now in observational cosmology. The The product will be the accurate recon­ redshift and morphology of galaxies at main breakthrough is probably repre­ struction of the whole global star-forma­ more moderately high redshifts (R. Ellis, sented by the success of a simple but tion history of the universe. Theoretical M. Colless, and W. Couch). The HOF robust photometric criterion for the iden­ work on the chemical evolution of the images have now allowed to morpholog­ tification of high-redshift galaxies, that universe (hopefully a closed box indeed) ically classify galaxies as faint as I = has allowed to find star-forming galaxies that parallel these observations was pre­ 24.5, and have shown once more that all the way to z = 3.5, and that may weil sented at the meeting by M. Fall, while the well-known excess in faint galaxy work also beyond (cf. Steidel et al., complementary constraints on the early counts is mainly due to blue, irregular, 1995, AJ, 110, 2519; see also Macchetto SFR that can be obtained from far-infra­ star-forming galaxies. So, the ratio of and Giavalisco, 1995, The Messenger, red observations by FIRAS/COBE and blue to red galaxies appears to increase 81, 14). M. Giavalisco showed aseries ISO, were discussed by J.L. Puget, M. with redshift, both in the field as weil as of impressive Keck telescope spectra of Rowan-Robinson, and A. Franceschini. in clusters (the latter being the Butchler­ these galaxies, selected in both the ge­ Searching for very high redshift galax­ Oemler effect), and it remains to be neric field and the Hubble Deep Field ies, either by Lya. imaging or photometri­ quantitatively established what differ­ (HOF), and together with O. Macchetto cally locating breaks in the spectral en­ ence exists (if any) between fjeld and argued for these objects being the pre­ ergy distribution, was further discussed clusters as far as the evolution with z of cursors of present-day spheroidals by K. Meisenheimer, E. Thommes, and the B/R ratio is concerned. caught in the act of their formation. Fig­ E. Giallongo, the latter reporting the dis­ Intriguingly, Figure 1 suggests that the ure 1 (also shown by Giavalisco, from covery of the so far most distant star­ global SFR may peak somewhere Madau et al., 1996, preprint) gives an forming galaxy at z = 4.7, about 2" away around z = 2, tantalisingly c10se to the idea of the kind of high-level information from a quasar with the same redshift well-known peak in the aso redshift on the evolution of the universe that we (see Fig. 2). 3D spectroscopic observa­ distribution that was reviewed by S. can now grasp from these data. The glo­ tions of this object were also presented Cristiani. However, the distribution itself bal star-formation rate (SFR) per unit by G. Adam, and the merits for high-red­ remains somewhat uncertain beyond z comoving volume appears to climb a shift studies of a 3D, adaptive optics fed = 2, and various speakers (R. McMa­ factor - 10 from z = 0 to z = 1, a result spectrograph on the VLT were further il­ hon, R. Webster, A. Omont, and P. Shav­ that comes from the Canada-France lustrated by G. Comte. Yet another way er) reported on current efforts to put it on firmer grounds, with special emphasis on prospects to detect asos beyond the z = 5 wall. What relation is there be­ Figure 1: The global star tween the peak in the aso activity and formation and metal pro­ -1 duction rates per unit eo­ the expected peak in the global SFR? moving volume (right Hence, what relation is there between seale and left seale, re­ the formation of galactic spheroids, and speetively) as a (unetion -3 that of massive central black holes, the of redshift (from Madau n, -1.5 Ö likely powerhouse of aso emission? ()Q et al. 1996, preprint). ;:.. These questions did not receive an­ The open triangle gives ~ ~~ swers at the meeting, but several speak­ the loeal value (from -33 . ------1--- --j------1- ers (H. Röttgering, A. Cimatti, and S. di Gallego et al. 1995, ApJ, 455, L1); filled eireles are 6 -2 Serego Alighieri) discussed the latest re­ from the Canada-Franee sults - especially from HST - concern­ Redshift Survey (Lilly et ing high-redshift radio galaxies, and the al., 1996, ApJ, 460, LI); perspectives to understand the connec­ the cross is (rom Steidel tion between galaxy formation and nu­ -2.5 et al. (1996, ApJ. in clear activity. The relative contribution of press); and the (illed aso's and primeval galaxies in reionis­ squares are (or galaxies ing the universe was then explored by A. in the Hubble Oeep - 4.5 '--::--'-1-'---''-'-.J....L-'-'-'-:':-'--'---'-'-L..L..1-'-L-'-i...... L.-'-L....L...l 023 Blanchard. Field. The horizontalline 4 5 redshifl is the eosmie-time aver­ A complementary approach to gather age rate as derived (rom the loeal abundanee o( heavy elements (assuming qo = 0.5 and Ho = 50 insight into the formation of galaclic (paper presented by M. Giavaliseo). spheroids (i.e., ellipticals and the bulge 10 8.0 10-18 Leibundgut), and of course the local LSS with its walls, filaments, and voids that Lya Galaxy dose to the may or may not persist to high redshifts ~ i QSO BR1202-0725 depending on the cosmological model. < 6.0 10-18 < Altogether, this wealth of data needs i to be framed in a world model to make < ::J I baryons are present in the amount pre­ (;: dicted by Big Bang nucleosynthesis, (3) primordial density fluctuation are gaus­ 0 sian and were generated by quantum ef­ 7000 8000 fects during inflation, (4) structures grow Wavelenglh ( Ä) solely through the effect of gravity, and (5) galaxies form by dissipative collapse Figure 2:A 3.5-hour integration on the galaxy - 2"from the z = 4. 7 QSO BR1202-0725 obtained with the EMMI spectrograph at the ESO 3.5-m NTT (courtesy of S. D'Odorico). The spectrum within massive halos made of dark mat­ shows a strong emission line identified as Lya atz = 4.702, and a continuum level in agreement ter. Within this frame the observations with the integrated magnitude of this object (I = 24.1, Fontana et al., 1996, MNRAS 279, L27). should allow us to unambiguously deter­ 1 This level of the rest frame ultraviolet continuum indicates a star-formation rate of - 30 M0 yr • mine a consistent set of the main model The C IVemission doublet is not detected, which sets an upper limit to its intensity of - 1/10 that parameters: Ho Qo) Qb' QCDM' A, and n, of Lya. The object is one of the-high redshift candidates from a deep, four-colour study of the the spectral index of the primordial fluc­ galaxies in the field of the QSO (paper presented by E. Giallongo). tuations. As S. White emphasised, should this effort fail, we will have to give up some of the five basic assumptions. of spirals) is to follow their evolution with carini), group and cluster detection from The role that the VLT will be able to redshift. R. Bender and M. Franx report­ aso absorption li ne systems (P. play in observational cosmology will ulti­ ed about the construction of the funda­ Petitjean and M. Haehnelt) and from mately depend (besides the commit­ mental plane relation for cluster ellipti­ gravitational shear (P. Schneider and B. ment of the ESO community) on its com­ cals up to z = 0.4, thus setting a tight Fort). While systematic studies of mod­ plement of focal instruments and on lower limit (z ;;::: 2) for the formation ep­ erate redshift clusters (unfortunately their efficiency. For this reason VLT in­ och of the bulk of the present-day stellar mostly Iimited to the northern hemi­ struments were on stage both at the be­ content in these galaxies. Combining sphere) are now weil under way (R. ginning and at the closure of the meet­ HST imaging (giving accurate effective Carlberg), successful detections of clus­ ing, with the PI's of the first-generation radii and surface brightness distribu­ ters around powerful AGNs were re port­ instruments and of those under consid­ tions) with 8-10-m-telescope spectros­ ed. These included a cluster at z = 1.2, eration illustrating their scientific drivers copy (giving velocity dispersions and that combined HST and Keck data show and their technical performances. Thus, metaliicity indices) is the winning strate­ to contain already red (Le. old) ellipticals I. Appenzeller, S. D'Odorico, P. Feien­ gy in this field, and D. Koo reported re­ (M. Dickinson), and the detection of bok, O. LeFEwre, R. Lenzen, A. Moor­ cent Keck observations of high-z ellipti­ c1ustering at a redshift as high as - 2.4 wood, and K. Taylor presented respec­ cals as weil as spirals and faint blue gal­ (P. Francis). Tracing the evolution of tively FORS, UVES, FUEGOS, VIR­ axies. The evolution of the fundamental large-scale structure (LSS) at high red­ MOS, CONICA, ISAAC, AUSTRALlS, plane and Tully-Fisher relations involve shift was then illustrated both by present and SINFONI, all acronyms that will be­ both dynamical and stellar population and planned galaxy redshift surveys (V. come familiar to us like today are SUSI properties of galaxies. As such, they can De Lapparent and G. Vettolani), and by and EMMI and TIMMI, etc. Some limita­ constrain the formation epoch of the gravitational shear (P. Schneider and B. tions of the first-generation instruments stars in these galaxies, but still allow a Fort). emerged clearly at the meeting, espe­ variety of galaxy-build-up scenarios. For While the emphasis of the meeting cially concerning the multiobject and example, in some CDM simulations of was obviously on high-redshift objects, area spectroscopy, and G. Monnet in its galaxy formation and evolution (reported D. Tytler in his comprehensive general c10sure talk illustrated how ESO is going by G. Kauffmann and M. Steinmetz) the introduction emphasized that a great to cope with this in selecting the next­ bulk of stars may weil form at very high deal about the early universe can be un­ generation instruments. z, but their assembly to build up the big derstood by looking at nearby objects. In the end, what lessons did we learn galaxies of today does not complete the For example, dating the oldest stars and from this most exciting meeting, that process before z::; 1. Thus, even more mapping the age, chemical and kinemat­ may be relevant for planning the future fundamental than the fundamental plane ic structure in our own Galaxy and in science at the VLT? The first lesson was itself may eventually be the empirical nearby galaxies, getting stellar abun­ that VLT-grade projects need extensive construction of the distribution functions dances for residues of the Big Bang nu­ preparation, both in terms of finding and of the velocity widths and velocity dis­ c1eosynthesis, etc. One crucial aspect of selecting the appropriate targets, and in persions at various redshifts. Velocities the local universe still worth investigating terms of dedicated scientific software to - better than luminosities - indeed rep­ concerns normalisations. While getting handle enormous data cubes. The sec­ resent a rather direct measure of the rich sampies of galaxies at high red­ ond lesson comes from the tremendous depth of galaxy potential wells, and their shifts, one would like to compare them to success of a combined HST and Keck distribution traces the assembly of dark fair sampies at z = 0, so as to gauge the approach to so many astrophysical matter halos on galaxy scales, the firmer change that has intervened in between. problems, with HST providing high-reso­ result of CDM simulations. This includes e.g. the local luminosity lution imaging on fairly wide fields and/or Next to galaxies on the mass scale, function for morphologically typed galax­ UV spectroscopy, and the 10-m tele­ galaxy clusters at high redshift also re­ ies (G. Vettolani reported on the ESO scope providing spectra of sufficient res­ ceived wide coverage at the meeting, in­ redshift survey results), supernovae of olution of the same objects. By the year cluding X-ray searches (H. Böhringer) Type la, where observation of high-z 2000 about a dozen 8-m-class tele­ and their optical counterparts (G. Chin- counterparts can help determine qo (B. scopes will be in operation world-wide, 11 and European astronomers will held data are made public just days after hav­ ever, and this was the fifth lesson, the about a 50% share of the whole stack. ing been obtained. This example is likely explosion we are now witnessing thanks Maintaining adequate access to HST, to be contagious, and a growing fraction primarily to HST and Keck can only ac­ and especially to the Next-Generation of astronomical data is likely to be dis­ celerate further as more 8-10-m-class Space Telescope now under study, is vi­ tributed in a similar way in the future. We telescopes come into line. Hence, timing tal for European astronomy to get full should prepare and be prepared for that, becomes essential. With progress being profit from its investments on ground­ and anticipate the sociological changes so fast, maintaining the schedule and based as weil as space-borne tele­ that such a new operation mode will deploying focal instruments in the short­ scopes (e.g. VLT, GEMINI, LBT, CO­ bring along. The fourth lesson, perhaps est possible time is a top priority for the BRAS/SAMBA, ISO, XMM, etc.). Only if a hardly new one, was that a large varie­ VLT project. such access will be secured (and ex­ ty of observational capabilities is re­ panded) will European astronomy re­ quired to make progress in observation­ main fully competitive. The third lesson al cosmology, and it is somewhat reas­ also comes from the HST experience. suring to appreciate once more that the With the HDF, for the first time a huge current VLT instrumentation plan ofters Alvio Renzini amount of high-quality, frontier-science in fact the needed diversification. How- e-mail: [email protected]

Aerial view of Paranal laken by H. Zodel in May 1996.

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