Welcome to the LEVEL5 Knowledge Base on Extragalactic Astronomy and Cosmology.

LEVEL5 is an on-going and developing experimental service supported in part by the National Aeronautics and Space Administration (NASA) (through the Applied Information Systems Research Program: AISRP) and by the Carnegie Institution of Washington (CIW), in conjunction with the NASA/IPAC Extragalactic Database (NED). LEVEL5 is operated out of the Infrared Processing and Analysis Center (IPAC) on the campus of the California Institute of Technology (CIT) in Pasadena, California.

The purpose of LEVEL5 is to bring together in a single gateway WEB site (where copyrights allow) "original" documents and reviews and/or electronic links to articles of current and lasting interest to cosmologists, particle physicists and extragalactic astronomers.

LEVEL5 is a hyperlinked document, providing multiple paths to information, presented at a variety of levels of complexity: from simple definitions up to essays, recent research articles, detailed monographs and extensive reviews. Within each of these articles, the individual extragalactic objects cited in the text are cross-linked to the NED Basic Data frames, and similarly all available citations are hyperlinked to NASA's Abstract Data Service (ADS) or to ASTRO-PH, in some important cases prior to publication. Tabular Data, images and graphs are also provided and are being progressively linked to and from essays and review articles.

We hope that you find LEVEL5 useful in your personal research and graduate education programs.

Barry F. Madore (barry@ipac.caltech.edu)
NED Co-Director, LEVEL5 PI

Joseph Mazzarella (mazz@ipac.caltech.edu)
NED Scientist, LEVEL5 Co-Investigator

Cren Frayer (cd@ipac.caltech.edu)
LEVEL5 Webmaster

Kay Baker (kbaker@ipac.caltech.edu)
Graphics

Diana Schettini (diana@ipac.caltech.edu)
Special Projects

[If you have comments on LEVEL5 please feel free to contact Barry F. Madore either by phone (626-395-1859), by e-mail (barry@ipac.caltech.edu), or by regular mail (NED, MS 100-22, IPAC, Caltech, Pasadena, CA 91125). We would especially appreciate having suggestions for prioritizing the inclusion of the many fine review articles presently available in print; our time is limited but our intent is to make LEVEL5 be as useful as possible in a timely manner to the widest community of users. This site is still in its early phases of development, and as such it claims no degree of completeness.]

We are indebted to Annual Reviews Inc., and especially its Editor-in-Chief, Mr. Sam Gubbins, for its early support in allowing us to scan in, reformat and provide WEB access to the many articles from the Annual Reviews of Astronomy and Astrophysics now appearing in LEVEL5. We also gratefully acknowledge the proactive support given by Dr. Adam Black and Dr. Simon Mitton in providing on-line access to introductory chapters in monographs and graduate textbooks on extragalactic topics as published by Cambridge University Press.