32,501 research outputs found
The Deep SWIRE Field III. WIYN Spectroscopy
We present the results of spectroscopy using HYDRA on the WIYN 3.5m telescope
of objects in the deep SWIRE radio field. The goal of the project was to
determine spectroscopic redshifts for as many of the brighter objects in the
field as possible, especially those detected in the radio and at 24 microns.
These redshifts are primarily being used in studies of galaxy evolution and the
connection of that evolution to AGN and star-formation. Redshifts measured for
365 individual objects are reported. The redshifts range from 0.03 to 2.5,
mostly with z < 0.9. The sources were selected to be within the WIYN HYDRA
field of approximately 30' in radius from the center of the SWIRE deep field,
10h46m00s, 59d 01'00" (J2000). Optical sources for spectroscopic observation
were selected from a r-band image of the field. A priority list of
spectroscopic targets was established in the following order: 20cm detections,
24 micron detections, galaxies with r < 20 and the balance made up of fainter
galaxies in the field. We provide a table listing the galaxy positions,
measured redshift and error, and note any emission lines that were visible in
the spectrum. In practice almost all the galaxies with r < 19 were observed
including all of the radio sources and most of the 24 microns sources with r <
20 and a sample of radio sources which had fainter optical counterparts on the
r-band image.Comment: 6 pages, 3 tables, 2 figures, full electronic tables at
http://www.aoc.nrao.edu/~fowen/papers/SWIRE/WIYNpaper3/, accepted ApJ Suppl
Serie
Development of a character, line and point display system
A compact graphics terminal for use as the input to a computerized medical records system is described. The principal mode of communication between the terminal and the records system is by checklists and menu selection. However, the terminal accepts short, handwritten messages as well as conventional alphanumeric input. The terminal consists of an electronic tablet, a display, a microcomputer controller, a character generator, and a refresh memory for the display. An Intel SBC 80/10 microcomputer controls the flow of information and a 16 kilobyte memory stores the point-by-point array of information to be displayed. A specially designed interface continuously generates the raster display without the intervention of the microcomputer
The evaporation valley in the Kepler planets
A new piece of evidence supporting the photoevaporation-driven evolution
model for low-mass, close-in exoplanets was recently presented by the
California-Kepler-Survey. The radius distribution of the Kepler planets is
shown to be bimodal, with a ``valley' separating two peaks at 1.3 and 2.6
Rearth. Such an ``evaporation-valley' had been predicted by numerical models
previously. Here, we develop a minimal model to demonstrate that this valley
results from the following fact: the timescale for envelope erosion is the
longest for those planets with hydrogen/helium-rich envelopes that, while only
a few percent in weight, double its radius. The timescale falls for envelopes
lighter than this because the planet's radius remains largely constant for
tenuous envelopes. The timescale also drops for heavier envelopes because the
planet swells up faster than the addition of envelope mass. Photoevaporation,
therefore, herds planets into either bare cores ~1.3 Rearth, or those with
double the core's radius (~2.6 Rearth). This process mostly occurs during the
first 100 Myrs when the stars' high energy flux are high and nearly constant.
The observed radius distribution further requires that the Kepler planets are
clustered around 3 Mearth in mass, are born with H/He envelopes more than a few
percent in mass, and that their cores are similar to the Earth in composition.
Such envelopes must have been accreted before the dispersal of the gas disks,
while the core composition indicates formation inside the ice-line. Lastly, the
photoevaporation model fails to account for bare planets beyond ~30-60 days, if
these planets are abundant, they may point to a significant second channel for
planet formation, resembling the Solar-System terrestrial planets.Comment: 15 pages, published in Ap
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