Download or read book Aperture Synthesis Study of Neutral Hydrogen in NGC 2403 and NGC 4236 I Observations II Discussion written by G. S. Shostak and published by . This book was released on 1972 with total page 60 pages. Available in PDF, EPUB and Kindle. Book excerpt: Observational results of an aperture synthesis study of neutral hydrogen in the nearby galaxies NGC 2403 and NGC 4236 are presented. Maps of the integral of the line profile at each position on the galaxies are given, as well as maps showing lines of constant radial velocity determined from the peaks of the profiles. Spatial resolution is 2' of arc; velocity resolution is 21 km/s. In addition, line profiles for the galaxies as a whole and maps of the 1420 MHz continuum radiation from each object are displayed. (Author).
Download or read book Nuclear Science Abstracts written by and published by . This book was released on 1974 with total page 692 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Nuclear Science Abstracts written by and published by . This book was released on 1974-03 with total page 1100 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Aperture Synthesis Study of Neutral Hydrogen in the Galaxies NGC 6946 and IC 342 written by and published by . This book was released on 1972 with total page 33 pages. Available in PDF, EPUB and Kindle. Book excerpt: Synthesis observations of netural hydrogen emission in the two spiral galaxies NGC 6946 and IC 342 are presented. The velocity resolution is 21 km/s and the angular resolution is 2 and 4 min of arc for NGC 6946 and IC 342 respectively. Results are presented in the form of contour maps of the integral and mean velocity of the HI profile at each position in the galaxy, as well as a line profile for each galaxy as a whole. Both galaxies evidence a central depression in their HI distributions. The rotation curves have steep central gradients with rather constant velocities once the maximal velocity is reached. The HI mass for NGC 6946 is 21 billion solar mass units and for IC 342 is 15 billion solar mass units, assuming distances of 10.1 and 4.5 Mpc respectively. Other properties are summarized in the table.
Download or read book The Dark Matter Problem written by Robert H. Sanders and published by Cambridge University Press. This book was released on 2010-04-22 with total page 214 pages. Available in PDF, EPUB and Kindle. Book excerpt: Most astronomers and physicists now believe that the matter content of the Universe is dominated by dark matter: hypothetical particles which interact with normal matter primarily through the force of gravity. Though invisible to current direct detection methods, dark matter can explain a variety of astronomical observations. This book describes how this theory has developed over the past 75 years, and why it is now a central feature of extragalactic astronomy and cosmology. Current attempts to directly detect dark matter locally are discussed, together with the implications for particle physics. The author comments on the sociology of these developments, demonstrating how and why scientists work and interact. Modified Newtonian Dynamics (MOND), the leading alternative to this theory, is also presented. This fascinating overview will interest cosmologists, astronomers and particle physicists. Mathematics is kept to a minimum, so the book can be understood by non-specialists.
Download or read book Literature 1973 Part 1 written by Siegfried Böhme and published by Springer Science & Business Media. This book was released on 2013-03-14 with total page 618 pages. Available in PDF, EPUB and Kindle. Book excerpt: Astronomy and Astrophysics Abstracts, which has appeared in semi-annual volumes since 1969, is de voted to the recording, summarizing and indexing of astronomical publications throughout the world. It is prepared under the auspices of the International Astronomical Union (according to a resolution adopted at the 14th General Assembly in 1970). Astronomy and Astrophysics Abstracts aims to present a comprehensive documentation of literature in all fields of astronomy and astrophysics. Every effort will be made to ensure that the average time interval between the date of receipt of the original literature and publication of the abstracts will not exceed eight months. This time interval is near to that achieved by monthly abstracting journals, com pared to which our system of accumulating abstracts for about six months offers the advantage of greater convenience for the user. Volume 9 contains literature published in 1973 and received before August 15, 1973; some older liter ature which was received late and which is not recorded in earlier volumes is also included. We acknowledge with thanks contributions to this volume by Dr. J. Bouska, who surveyed journals and publications in the Czech language and supplied us with abstracts in English, and by the Common wealth Scientific and Industrial Research Organization (C.S.I.R.O.), Sydney, for providing titles and abstracts of papers on radio astronomy.
Download or read book Aperture Synthesis Study of Neutral Hydrogen in the Galaxy M 101 I Observations II Discussion written by D. H. Rogstad and published by . This book was released on 1971 with total page 50 pages. Available in PDF, EPUB and Kindle. Book excerpt: Synthesis observations of neutral hydrogen emission in the spiral galaxy M101 obtained with the Owens Valley twin-element interferometer are presented. The spatial resolution is 4 sec. of arc, and the velocity resolution is 21 km/s. The observations are given in the form of contour maps of the integral and the mean velocity of the HI profile at each position in the galaxy, and a line profile for the galaxy as a whole. A contour map of the 21 cm continuum radiation is also presented. The observations described in another paper (Rogstad and Shostak, 1971) are discussed with the following conclusions: There is a close correspondence between features in the surface density of both light and HI in the galaxy M101. The HI velocity field contains streaming motions which are in agreement with the predictions of the first-order density wave theory of spiral structure. There is evidence for expansion motions of at least 40 km/s in the central region of the galaxy. (Author).
Download or read book Cosmology s Century written by P. J. E. Peebles and published by Princeton University Press. This book was released on 2022-04-26 with total page 432 pages. Available in PDF, EPUB and Kindle. Book excerpt: From Nobel Prize–winning physicist P. J. E. Peebles, the story of cosmology from Einstein to today Modern cosmology began a century ago with Albert Einstein's general theory of relativity and his notion of a homogenous, philosophically satisfying cosmos. Cosmology's Century is the story of how generations of scientists built on these thoughts and many new measurements to arrive at a well-tested physical theory of the structure and evolution of our expanding universe. In this landmark book, one of the world's most esteemed theoretical cosmologists offers an unparalleled personal perspective on how the field developed. P. J. E. Peebles was at the forefront of many of the greatest discoveries of the past century, making fundamental contributions to our understanding of the presence of helium and microwave radiation from the hot big bang, the measures of the distribution and motion of ordinary matter, and the new kind of dark matter that allows us to make sense of these results. Taking readers from the field's beginnings, Peebles describes how scientists working in independent directions found themselves converging on a theory of cosmic evolution interesting enough to warrant the rigorous testing it passes so well. He explores the major advances—some inspired by remarkable insights or perhaps just lucky guesses—as well as the wrong turns taken and the roads not explored. He shares recollections from major players in this story and provides a rare, inside look at how science is really done. A monumental work, Cosmology's Century also emphasizes where the present theory is incomplete, suggesting exciting directions for continuing research.
Download or read book Astronomy and Astrophysics written by and published by . This book was released on 1973 with total page 208 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Scientific and Technical Aerospace Reports written by and published by . This book was released on 1973 with total page 818 pages. Available in PDF, EPUB and Kindle. Book excerpt: Lists citations with abstracts for aerospace related reports obtained from world wide sources and announces documents that have recently been entered into the NASA Scientific and Technical Information Database.
Download or read book Government Reports Index written by and published by . This book was released on 1972 with total page 916 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Neutral Hydrogen Aperture Synthesis Maps of IC2574 and NGC 7640 written by G. A. Seielstad and published by . This book was released on 1973 with total page 22 pages. Available in PDF, EPUB and Kindle. Book excerpt: Aperture synthesis observations with an angular resolution about 2 arc-min of two late-type galaxies have revealed HI distributions some 1.5 times larger than their photographic images. IC2574, classified as an irregular galaxy, has a well organized velocity field typical of a late spiral galaxy. The major HI concentrations do not correspond with the brightest optical features. A ridge of peculiar velocities of about 10 km/s in the region of the optical 'bar' may indicate streaming motions of gas along the bar. NGC7640 is an SBc galaxy at an inclination of 77 degrees. There is no evidence of any HI halo brighter than 100 degrees K km/s, although there is a suggestion of warping of the plane of the HI layer. (Author).
Download or read book International Aerospace Abstracts written by and published by . This book was released on 1973 with total page 1108 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Government Reports Announcements written by and published by . This book was released on 1972-10 with total page 1290 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book IBZ written by Otto Zeller and published by . This book was released on 1976 with total page 720 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Aperture Synthesis Observations of Neutral Hydrogen in Three Galaxies written by G. Seth Shostak and published by . This book was released on 1974 with total page 228 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Aperture Synthesis of Interstellar Neutral Hydrogen in Absorption II Cygnus A the Crab Nebula and Other Sources written by Eric W. Greisen and published by . This book was released on 1973 with total page 47 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Owens Valley Radio Observatory interferometer has been used to carry out a program of aperture synthesis in the interstellar neutral hydrogen line. The results of synthesis observations of Cygnus A, the Crab Nebula and 3C353 and single-spacing observations of W12 and 3C147 are presented. Considerable spatial structure in the absorbing medium is found with scale lengths about 1 pc (and perhaps even as small as 0.14 pc) being common. Some of the small-scale features are seen as condensations within much larger clouds. The hydrogen densities appear to be mostly on the order of 100/cc. Upper limits to the temperatures lower than 50K are found for some spectral components, but upper limits between 80 and 160K are more common. The implications of these results for the two-phase model of the interstellar medium are discussed. (Author Modified Abstract).
