2,404 research outputs found
Application of a New Non-Linear Least Squares Velocity Curve Analysis Technique for Spectroscopic Binary Stars
Using measured radial velocity data of nine double lined spectroscopic binary
systems NSV 223, AB And, V2082 Cyg, HS Her, V918 Her, BV Dra, BW Dra, V2357
Oph, and YZ Cas, we find corresponding orbital and spectroscopic elements via
the method introduced by Karami & Mohebi (2007a) and Karami & Teimoorinia
(2007). Our numerical results are in good agreement with those obtained by
others using more traditional methods.Comment: 6 pages, 3 figures. Accepted for publication in Astrophysics & Space
Scienc
On polymorphic logical gates in sub-excitable chemical medium
In a sub-excitable light-sensitive Belousov-Zhabotinsky chemical medium an
asymmetric disturbance causes the formation of localized traveling
wave-fragments. Under the right conditions these wave-fragment can conserve
their shape and velocity vectors for extended time periods. The size and life
span of a fragment depend on the illumination level of the medium. When two or
more wave-fragments collide they annihilate or merge into a new wave-fragment.
In computer simulations based on the Oregonator model we demonstrate that the
outcomes of inter-fragment collisions can be controlled by varying the
illumination level applied to the medium. We interpret these wave-fragments as
values of Boolean variables and design collision-based polymorphic logical
gates. The gate implements operation XNOR for low illumination, and it acts as
NOR gate for high illumination. As a NOR gate is a universal gate then we are
able to demonstrate that a simulated light sensitive BZ medium exhibits
computational universality
The abundances of ethane to acetylene in the atmospheres of Jupiter and Saturn
The present determination of the stratospheric abundances of ethane and acetylene on Jupiter and Saturn on the basis of IR spectra near 780/cm uses atmospheric models whose thermal and density profiles have constant mixing ratios. The ratio of ethane to acetylene is noted to be insensitive to model atmosphere assumptions; it is 55 + or - 31 for Jupiter and 23 + or - 12 where model mixing ratios are uniform. Atmospheric model density profiles adapted from theoretical photochemical models are noted to also yield a higher ethane/acetylene ratios for Jupiter
The Assembly of the Red Sequence at z ~ 1: The Color and Spectral Properties of Galaxies in the Cl1604 Supercluster
We investigate the properties of the 525 spectroscopically confirmed members of the Cl1604 supercluster at z ~ 0.9 as part of the Observations of Redshift Evolution in Large Scale Environments survey. In particular, we focus on the photometric, stellar mass, morphological, and spectral properties of the 305 member galaxies of the eight clusters and groups that comprise the Cl1604 supercluster. Using an extensive Keck Low-Resolution Imaging Spectrometer (LRIS)/DEep Imaging Multi-Object Spectrograph (DEIMOS) spectroscopic database in conjunction with ten-band ground-based, Spitzer, and Hubble Space Telescope imaging, we investigate the buildup of the red sequence in groups and clusters at high redshift. Nearly all of the brightest and most massive red-sequence galaxies present in the supercluster environment are found to lie within the bounds of the cluster and group systems, with a surprisingly large number of such galaxies present in low-mass group systems. Despite the prevalence of these red-sequence galaxies, we find that the average cluster galaxy has a spectrum indicative of a star-forming galaxy, with a star formation rate between those of z ~ 1 field galaxies and moderate-redshift cluster galaxies. The average group galaxy is even more active, exhibiting spectral properties indicative of a starburst. The presence of massive, red galaxies and the high fraction of starbursting galaxies present in the group environment suggest that significant processing is occurring in group environments at z ~ 1 and earlier. There is a deficit of low-luminosity red-sequence galaxies in all Cl1604 clusters and groups, suggesting that such galaxies transition to the red sequence at later times. Extremely massive (~10^(12)M_☉) red-sequence galaxies routinely observed in rich clusters at z ~ 0 are also absent from the Cl1604 clusters and groups. We suggest that such galaxies form at later times through merging processes. There are significant populations of transition galaxies at intermediate stellar masses (log(M_*)=10.25-10.75) present in the group and cluster environments, suggesting that this range is important for the buildup of the red-sequence mass function at z ~ 1. Through a comparison of the transitional populations present in the Cl1604 cluster and group systems, we find evidence that massive blue-cloud galaxies are quenched earliest in the most dynamically relaxed systems and at progressively later times in dynamically unrelaxed systems
Exploring the inner region of Type 1 AGNs with the Keck interferometer
The exploration of extragalactic objects with long-baseline interferometers
in the near-infrared has been very limited. Here we report successful
observations with the Keck interferometer at K-band (2.2 um) for four Type 1
AGNs, namely NGC4151, Mrk231, NGC4051, and the QSO IRAS13349+2438 at z=0.108.
For the latter three objects, these are the first long-baseline interferometric
measurements in the infrared. We detect high visibilities (V^2 ~ 0.8-0.9) for
all the four objects, including NGC4151 for which we confirm the high V^2 level
measured by Swain et al.(2003). We marginally detect a decrease of V^2 with
increasing baseline lengths for NGC4151, although over a very limited range,
where the decrease and absolute V^2 are well fitted with a ring model of radius
0.45+/-0.04 mas (0.039+/-0.003 pc). Strikingly, this matches independent radius
measurements from optical--infrared reverberations that are thought to be
probing the dust sublimation radius. We also show that the effective radius of
the other objects, obtained from the same ring model, is either roughly equal
to or slightly larger than the reverberation radius as a function of AGN
luminosity. This suggests that we are indeed partially resolving the dust
sublimation region. The ratio of the effective ring radius to the reverberation
radius might also give us an approximate probe for the radial structure of the
inner accreting material in each object. This should be scrutinized with
further observations.Comment: accepted for publication in A&A Letter
Bridging the Gaps: Collaboration in a Faculty and Librarian Community of Practice on Information Literacy
Mass Flows in Cometary UCHII Regions
High spectral and spatial resolution, mid-infrared fine structure line
observations toward two ultracompact HII (UCHII) regions (G29.96 -0.02 and Mon
R2) allow us to study the structure and kinematics of cometary UCHII regions.
In our earlier study of Mon R2, we showed that highly organized mass motions
accounted for most of the velocity structure in that UCHII region. In this
work, we show that the kinematics in both Mon R2 and G29.96 are consistent with
motion along an approximately paraboloidal shell. We model the velocity
structure seen in our mapping data and test the stellar wind bow shock model
for such paraboloidal like flows. The observations and the simulation indicate
that the ram pressures of the stellar wind and ambient interstellar medium
cause the accumulated mass in the bow shock to flow along the surface of the
shock. A relaxation code reproduces the mass flow's velocity structure as
derived by the analytical solution. It further predicts that the pressure
gradient along the flow can accelerate ionized gas to a speed higher than that
of the moving star. In the original bow shock model, the star speed relative to
the ambient medium was considered to be the exit speed of ionized gas in the
shell.Comment: 34 pages, including 14 figures and 1 table, to be published in ApJ,
September 200
Survey of Pasture Species and Management, Manure Management, Milk Production and Reproduction on Pasture-Based Dairy Farms in Florida and Georgia, USA
Traditionally, most dairy farms in the south-eastern United States confine cows to barns or on pasture lots year-round and feed stored forages and concentrated feeds (Fontaneli et al. 2005). Often, much of the feed is purchased, however, the cost of purchased feed and fuel has risen rapidly in the last 5 years (NASS 2009). In addition, a significant amount of capital is tied up in buildings, machinery and manure management systems on the farms. For these reasons, many dairy farmers have shown an interest in or started transitioning to pasture-based dairy systems (Ricks and Hardee 2012). The management practices and production results of pasture-based dairy farms in the south-east appear to vary widely (Macoon et al. 2011), but have not been described.
The objective of this study was to document pasture and crop management, manure management and milk production on pasture-based dairy farms in Florida and Georgia
Mid-Infrared Photometry and Spectra of Three High Mass Protostellar Candidates at IRAS 18151-1208 and IRAS 20343+4129
We present arcsecond-scale mid-ir photometry (in the 10.5 micron N band and
at 24.8 microns), and low resolution spectra in the N band (R~100) of a
candidate high mass protostellar object (HMPO) in IRAS 18151-1208 and of two
HMPO candidates in IRAS 20343+4129, IRS 1 and IRS 3. In addition we present
high resolution mid-ir spectra (R~80000) of the two HMPO candidates in IRAS
20343+4129. These data are fitted with simple models to estimate the masses of
gas and dust associated with the mid-ir emitting clumps, the column densities
of overlying absorbing dust and gas, the luminosities of the HMPO candidates,
and the likely spectral type of the HMPO candidate for which [Ne II] 12.8
micron emission was detected (IRAS 20343+4129 IRS 3). We suggest that IRAS
18151-1208 is a pre-ultracompact HII region HMPO, IRAS 20343+4129 IRS 1 is an
embedded young stellar object with the luminosity of a B3 star, and IRAS
20343+4129 IRS 3 is a B2 ZAMS star that has formed an ultracompact HII region
and disrupted its natal envelope.Comment: 40 pages, 8 figures, 3 tables. Accepted for publication in
Astrophysical Journal (Part 1
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