摘要:

Human efforts to probe the extent of the cosmos clearly date back to pre-literate times, with significant progress occurring in early literate societies, the Renaissance to 18th century, the 19th and 20th centuries, but with some issues remaining for the millennium. The important issues are the size of the earth, the distance to the moon, the earth-sun distance, the distances to the stars, the size of the Milky Way, and the size of the universe as a whole, plus its age. It is perhaps significant that, with one exception, each question was definitively, answered in a later period than the one that first asked it. ©1999 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.58627

出版商:AIP    

年代:1999

数据来源: AIP

摘要:

At redshifts beyond 5–perhaps even beyond 20–stars formed within ‘subgalaxies’ and created the first heavy elements; these same systems (together perhaps with ‘miniquasars’) generated the UV radiation that ionized the IGM, and maybe also the first significant magnetic fields. These uncertain processes set the backdrop for the phenomena atz<5that are the theme of the present conference. ©1999 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.58643

出版商:AIP    

年代:1999

数据来源: AIP

摘要:

Observations of the cosmic microwave background will be an important ingredient in our efforts to understand the epoch of galaxy formation. Microwave background observations are most sensitive to physical conditions near the surface of last scatter,z∼1100.MAP should enable cosmologists to infer many of the initial conditions for galaxy formation. The microwave background photons also illuminate the “dark age”. Measurements of microwave background polarization can determine or at least constrain the redshift at which stars (or quasars) first reionize the universe. The observations are also sensitive to non-linear density fluctuations during this epoch. Microwave background measurements also probe the nearby universe. Low redshift objects produce additional fluctuations through gravitational lensing, the ISW effect and the Sunyaev-Zeldovich effect. ©1999 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.58644

出版商:AIP    

年代:1999

数据来源: AIP

摘要:

Empirical studies of the first generation of stars and quasars in the Universe will likely become feasible over the next decade. TheNext Generation Space Telescopewill provide direct imaging and photometry of sub-galactic objects atz≳10,while microwave anisotropy experiments, such as MAP or Planck, will set constraints on the ionization history of the intergalactic medium due to these sources. We describe the expected signals that will be detectable with these future instruments. ©1999 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.58620

出版商:AIP    

年代:1999

数据来源: AIP

摘要:

We study formation of galactic bulges in a representative CDM-type cosmological model using hydrodynamic numerical simulations. We show that currently favorable cosmological models predict that galactic bulges form at moderately high redshifts,z∼4,with correct density profiles and sizes. On the contrary, cosmological models with more small scale power, like the PIB class of models, would predict galactic bulges that are two orders of magnitude more dense than the observed ones. ©1999 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.58634

出版商:AIP    

年代:1999

数据来源: AIP

摘要:

We describe results from a 3D adaptive mesh refinement simulation offirst structure formationin a CDM-dominated universe. A spatial dynamic range of >250,000 is achieved, allowing us to see the formation of a collapsing primordial protostellar cloud core set within a cosmological framework. The core mass is∼100 M⊙,comparable to the Jeans mass at the densities and temperatures which prevail in the halo center onceH2cooling has become inefficient. ©1999 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.58641

出版商:AIP    

年代:1999

数据来源: AIP

摘要:

We present models for dusty high-redshift Ly&agr; emitting galaxies by combining the Press-Schechter formalism with a treatment of inhomogeneous dust distribution inside galaxies. These models reproduce the surface density of emitters inferred from recent observations, and also agree with previous non-detections. Although a detailed determination of the individual model parameters is precluded by uncertainties, we find that (i) the dust content of primordial galaxies builds up in no more than∼5×108&hthinsp;yr,(ii) the galactic HII regions are inhomogeneous with a cloud covering factor of order unity, and (iii) the overall star formation efficiency is at least ∼ 5&percent;. Future observations should be able to detect Ly&agr; galaxies up to redshifts ofz∼8.If the universe is reionized atzr≲8,the corresponding decline in the number of Ly&agr; emitters atz≳zrcould prove to be a useful probe of the reionization epoch. ©1999 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.58635

出版商:AIP    

年代:1999

数据来源: AIP

摘要:

In order to constrain the initial mass function of the first generation of stars (Population III), one has to study the fragmentation properties of primordial gas. We present results from 3D simulations, based on Smoothed Particle Hydrodynamics, which explore the idea that small-scale fluctuations in the (cold) dark matter recreate a filamentary and clumpy structure in the gas component on scales smaller than the initial Jeans mass, where all primordial fluctuations would have been wiped out. ©1999 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.58636

出版商:AIP    

年代:1999

数据来源: AIP

摘要:

I explore some consequences of Milgrom’s modified dynamics for cosmology. There appear to be two promising tests for distinguishing MOND from CDM: (1) the rate of growth of structure and (2) the baryon fraction. These should be testable with observations of clusters at high redshift and the microwave background, respectively. ©1999 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.58637

出版商:AIP    

年代:1999

数据来源: AIP

摘要:

The title of this article could of course encompass an entire meeting. I will focus my comments on reviewing of what we know about the most numerous absorption lines, the neutral hydrogen absorbers, and their evolution with redshift. This field of study has undergone a renaissance in last few years driven by observations with the Hubble Space Telescope of low redshift quasar absorption lines, observations of high redshift absorbers with the HIRES instrument on Keck, and cosmological modeling that allows us to make detailed comparisons of lines of sight through simulated universes. ©1999 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.58638

出版商:AIP    

年代:1999

数据来源: AIP