5,555 research outputs found
VLBI detection of an Infrared-Faint Radio Source
Infrared-Faint Radio Sources represent a new and unexpected class of object
which is bright at radio wavelengths but unusually faint at infrared
wavelengths. If, like most mJy radio sources, they were either conventional
active or star-forming galaxies in the local Universe, we would expect them to
be detectable at infrared wavelengths, and so their non-detection by the
Spitzer Space Telescope is surprising. Here we report the detection of one of
these sources using Very Long Baseline Interferometry, from which we conclude
that the sources are driven by Active Galactic Nuclei. We suggest that these
sources are either normal radio-loud quasars at high redshift or abnormally
obscured radio galaxies.Comment: accepted by MNRA
Extragalactic Radio Continuum Surveys and the Transformation of Radio Astronomy
Next-generation radio surveys are about to transform radio astronomy by
discovering and studying tens of millions of previously unknown radio sources.
These surveys will provide new insights to understand the evolution of
galaxies, measuring the evolution of the cosmic star formation rate, and
rivalling traditional techniques in the measurement of fundamental cosmological
parameters. By observing a new volume of observational parameter space, they
are also likely to discover unexpected new phenomena. This review traces the
evolution of extragalactic radio continuum surveys from the earliest days of
radio astronomy to the present, and identifies the challenges that must be
overcome to achieve this transformational change.Comment: To be published in Nature Astronomy 18 Sept 201
The Search for Extraterrestrial Intelligence (SETI)
A bibliography of reports concerning the Search for Extraterrestrial Intelligence is presented. Cosmic evolution, space communication, and technological advances are discussed along with search strategies and search systems
Interferometry
The following recommended programs are reviewed: (1) infrared and optical interferometry (a ground-based and space programs); (2) compensation for the atmosphere with adaptive optics (a program for development and implementation of adaptive optics); and (3) gravitational waves (high frequency gravitational wave sources (LIGO), low frequency gravitational wave sources (LAGOS), a gravitational wave observatory program, laser gravitational wave observatory in space, and technology development during the 1990's). Prospects for international collaboration and related issues are also discussed
Hydrogen 2p--2s transition: signals from the epochs of recombination and reionization
We propose a method to study the epoch of reionization based on the possible
observation of 2p--2s fine structure lines from the neutral hydrogen outside
the cosmological H {\sc ii} regions enveloping QSOs and other ionizing sources
in the reionization era. We show that for parameters typical of luminous
sources observed at the strength of this signal, which is
proportional to the H {\sc i} fraction, has a brightness temperature for a fully neutral medium. The fine structure line from this redshift
is observable at and we discuss prospects for the
detection with several operational and future radio telescopes. We also compute
the characteristics of this signal from the epoch of recombination: the peak
brightness is expected to be ; this signal appears in the
frequency range 5-10 MHz. The signal from the recombination era is nearly
impossible to detect owing to the extreme brightness of the Galactic emission
at these frequencies.Comment: 17 pages, 1 figure, to appear in Ap
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