123 research outputs found
The Atacama Large Millimeter/submillimeter Array: Overview & status
The Atacama Large Millimeter/submillimeter Array (ALMA) is an international
radio telescope under construction in the Atacama Desert of northern Chile.
ALMA will be situated on a high-altitude site at 5000 m elevation which
provides excellent atmospheric transmission over the instrument wavelength
range of 0.3 to 3 mm. ALMA will be comprised of two key observing components:
an array of up to sixty-four 12-m diameter antennas arranged in a multiple
configurations ranging in size from 0.15 to ~14 km, and a set of four 12-m and
twelve 7-m antennas operating in closely-packed configurations ~50m in diameter
(known as the Atacama Compact Array, or ACA), providing both interferometric
and total-power astronomical information. High-sensitivity dual-polarization 8
GHz-bandwidth spectral-line and continuum measurements between all antennas
will be available from two flexible digital correlators
A Study of the Large-Scale Distribution of Galaxies in the South Galactic Pole Region: II. Further Evidence for a Preferential Clustering Scale?
We analyse a set of new pencil-beam galaxy redshift data in three small
regions around the South Galactic Pole (SGP) area. We investigate whether we
can find any evidence of the quasi-periodic peaks discovered by Broadhurst et
al. (1990) in the distribution of galaxies along the NGP-SGP directions. We use
both a power spectrum analysis and a cross-correlation with a sliding comb-like
window (the comb-template technique). Despite the data are less deep (~600
h^{-1} Mpc) and certainly not optimal for such an investigation, there is
evidence of the same preferential ~130 h^{-1} Mpc scale in two fields displaced
respectively 15 and 30 degrees West of the Broadhurst et al. original probe.
Taken alone, however, this peak would not be statistically distinguishable from
a noise fluctuation. Nevertheless, the statistical significance of the
detection raises to 99% when one considers the CONDITIONAL probability of
finding a peak around THE SAME scale measured by Broadhurst et al.Comment: 5 LaTeX mn-style pages plus 3 tables and 7 PS figures, uses mn.sty,
accepted for publication in MNRA
A Study of the Large--Scale Distribution of Galaxies in the South Galactic Pole Region: I. The Data
We present the data from an extensive, moderately deep (b_J = 19.5)
spectroscopic survey of galaxies within four regions of sky located
near the South Galactic Pole. About 75% of the measured galaxies are in a 3deg
x 1.5deg region dominated by the rich cluster Klemola 44 (Abell 4038). The
other three smaller areas cover about 1 square degree each. Here we discuss in
detail the observing and data reduction strategies, the completeness and errors
on the measured redshifts. The data collected are being used for: (1) a study
of the large--scale redshift distribution of the galaxies in each field, and
(2) a thorough dynamical investigation of Klemola 44. Results from these
analyses will be presented in forthcoming papers.Comment: 7 MN-style text pages + 5 reduced-size tables, all in uu-compressed-
tarred PS format. 16 figures available in hardcopy from the authors. MNRAS,
in pres
Enzymatic colorimetric method for the determination of inorganic phosphorus in serum and urine.
The performance of an enzymatic colorimetric method for the determination of inorganic phosphorus in serum and urine is described. Phosphate ions react with inosine in the presence of purine nucleoside phosphorylase to form hypoxanthine; this is oxidized by xanthine oxidase to uric acid with production of hydrogen peroxide. The latter is determined with the aid of the chromogen system peroxidase/4-aminophenazone/N-ethyl-N-(3-methylphenyl)-N'-acetyl- ethylenediamine, the coloured product being measured at 555 nm. This series of reactions is completed in 5 min at 37\ub0C. The test is linear up to 240 mg/l. Analytical recovery in serum averaged 101.2 \ub1 1.2% and in urine 101.9 \ub1 3.2%. Within-run and between-run precision studies in serum and urine samples gave CVs 64 4.54% (at 22.0 mg/l). Results obtained by this method agree (r = 65 0.983) with the molybdate UV and molybdenum blue methods. Interference by endogenous substances, including organic phosphate, was negligible
Infrared Candidates for the Intense Galactic X-ray Source GX 17+2
We present new astrometric solutions and infrared Hubble Space Telescope
observations of GX 17+2 (X1813-140), one of the brightest X-ray sources on the
celestial sphere. Despite 30 years of intensive study, and the existence of a
strong radio counterpart with a sub-arcsecond position, the object remains
optically unidentified. The observed X-ray characteristics strongly suggest
that it is a so-called "Z-source," the rare but important category that
includes Sco X-1 and Cyg X-2. Use of the USNO-A2.0 catalog enables us to
measure the position of optical and infrared objects near the radio source to
sub-arcsecond precision within the International Celestial Reference Frame, for
direct comparison with the radio position, which we also recompute using modern
calibrators. With high confidence we eliminate the V~17.5 star NP Ser, often
listed as the probable optical counterpart of the X-ray source, as a candidate.
Our HST NICMOS observations show two faint objects within our 0.5" radius 90%
confidence error circle. Even the brighter of the two, Star A, is far fainter
than expected (H~19.8), given multiple estimates of the extinction in this
field and our previous understanding of Z sources, but it becomes the best
candidate for the counterpart of GX 17+2. The probability of a chance
coincidence of an unrelated faint object on the radio position is high.
However, if the true counterpart is not Star A, it is fainter still, and our
conclusion that the optical counterpart is surprisingly underluminous is but
strengthened.Comment: 15 pages including 3 figures and 3 tables. Accepted for publication
in The Astrophysical Journa
Infrared Photometric Variability of GX13+1 and GX17+2
We present infrared photometry of the Galactic Bulge X-ray binary systems
GX13+1 and GX17+2 obtained in 1997 July and August using OSIRIS on the 1.8m
Perkins Telescope at Lowell Observatory. GX13+1 clearly varies over ~0.6
magnitudes in the K-band. Our light curve suggests a modulation on a timescale
of ~20 days, which is in agreement with previously proposed orbital periods for
the system. The IR counterpart of GX17+2 is also variable in the K-band over
\~0.8 magnitudes on a timescale of days to weeks, extending the variability
first seen by Naylor, Charles, & Longmore (1991). We discuss the implications
our data have for Deutsch et al's (1999) identification of ``star A'' as the
true IR counterpart of GX17+2. The variability observed in our photometry of
the blend of star A and the foreground star NP Ser implies a ~4 magnitude
intrinsic variation in the K-band for GX17+2.Comment: Accepted for publication in ApJ, 5 pages, 4 figure
Tests with a Carlina-type diluted telescope; Primary coherencing
Studies are under way to propose a new generation of post-VLTI
interferometers. The Carlina concept studied at the Haute- Provence Observatory
is one of the proposed solutions. It consists in an optical interferometer
configured like a diluted version of the Arecibo radio telescope: above the
diluted primary mirror made of fixed cospherical segments, a helium balloon (or
cables suspended between two mountains), carries a gondola containing the focal
optics. Since 2003, we have been building a technical demonstrator of this
diluted telescope. First fringes were obtained in May 2004 with two
closely-spaced primary segments and a CCD on the focal gondola. We have been
testing the whole optical train with three primary mirrors. The main aim of
this article is to describe the metrology that we have conceived, and tested
under the helium balloon to align the primary mirrors separate by 5-10 m on the
ground with an accuracy of a few microns. The servo loop stabilizes the mirror
of metrology under the helium balloon with an accuracy better than 5 mm while
it moves horizontally by 30 cm in open loop by 10-20 km/h of wind. We have
obtained the white fringes of metrology; i.e., the three mirrors are aligned
(cospherized) with an accuracy of {\approx} 1 micron. We show data proving the
stability of fringes over 15 minutes, therefore providing evidence that the
mechanical parts are stabilized within a few microns. This is an important step
that demonstrates the feasibility of building a diluted telescope using cables
strained between cliffs or under a balloon. Carlina, like the MMT or LBT, could
be one of the first members of a new class of telescopes named diluted
telescopes.Comment: 18 pages, 17 figures, A&A, accepte
- …