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Deployment and Monitoring of an X-Band Dual-Polarization Phased Array Weather Radar
This thesis describes the deployment of MIRSL\u27s X-band dual-polarization Phase-Tilt Weather Radar (PTWR) at the University of Texas at Arlington during spring 2014. While this radar has been used to observe weather in Western Massachusetts, more observations of severe weather were required to determine the limits of its abilities in sensing more rapidly evolving weather systems. This site was chosen also for its proximity to the Dallas-Fort Worth Urban Testbed Network set up by the Center for Collaborative Adaptive Sensing of the Atmosphere (CASA), which provided the ability to compare and calibrate the PTWR data against another well-documented X-band weather radar. A data processing pipeline was developed for converting raw PTWR data to NetCDF format, which allows for easy sharing and mapping of weather data. Finally, this is the first in-depth documentation of the PTWR system and specifically the roof-mounted setup utilized for this deployment
A Structural Analysis of Star-Forming Region AFGL 490
We present Spitzer IRAC and MIPS observations of the star-forming region
containing intermediate-mass young stellar object (YSO) AFGL 490. We supplement
these data with near-IR 2MASS photometry and with deep SQIID observations off
the central high extinction region. We have more than doubled the known
membership of this region to 57 Class I and 303 Class II YSOs via the combined
1-24 um photometric catalog derived from these data. We construct and analyze
the minimum spanning tree of their projected positions, isolating one locally
over-dense cluster core containing 219 YSOs (60.8% of the region's members). We
find this cluster core to be larger yet less dense than similarly analyzed
clusters. Although the structure of this cluster core appears irregular, we
demonstrate that the parsec-scale surface densities of both YSOs and gas are
correlated with a power law slope of 2.8, as found for other similarly analyzed
nearby molecular clouds. We also explore the mass segregation implications of
AFGL 490's offset from the center of its core, finding that it has no apparent
preferential central position relative to the low-mass members.Comment: 44 pages, 13 figures, accepted to Ap
Mass and luminosity evolution of young stellar objects
A model of protostar mass and luminosity evolution in clusters gives new
estimates of cluster age, protostar birthrate, accretion rate and mean
accretion time. The model assumes constant protostar birthrate, core-clump
accretion, and equally likely accretion stopping. Its parameters are set to
reproduce the initial mass function, and to match protostar luminosity
distributions in nearby star-forming regions. It obtains cluster ages and
birthrates from the observed numbers of protostars and pre-main sequence (PMS)
stars, and from the modal value of the protostar luminosity. In 31 embedded
clusters and complexes the global cluster age is 1-3 Myr, matching available
estimates based on optical spectroscopy and evolutionary tracks. This method of
age estimation is simpler than optical spectroscopy, and is more useful for
young embedded clusters where optical spectrocopy is not possible. In the
youngest clusters, the protostar fraction decreases outward from the densest
gas, indicating that the local star-forming age increases outward from a few
0.1 Myr in small protostar-dominated zones to a few Myr in large PMS-dominated
zones.Comment: To appear in The Astrophysical Journal, Part
IRAS 20050+2720: Anatomy of a young stellar cluster
IRAS 20050+2720 is young star forming region at a distance of 700 pc without
apparent high mass stars. We present results of our multiwavelength study of
IRAS 20050+2720 which includes observations by Chandra and Spitzer, and 2MASS
and UBVRI photometry. In total, about 300 YSOs in different evolutionary stages
are found. We characterize the distribution of young stellar objects (YSOs) in
this region using a minimum spanning tree (MST) analysis. We newly identify a
second cluster core, which consists mostly of class II objects, about 10 arcmin
from the center of the cloud. YSOs of earlier evolutionary stages are more
clustered than more evolved objects. The X-ray luminosity function (XLF) of
IRAS 20050+2720 is roughly lognormal, but steeper than the XLF of the more
massive Orion nebula complex. IRAS 20050+2720 shows a lower N_H/A_K ratio
compared with the diffuse ISM.Comment: 15 pages, 12 figures, accepted by A
Weed management guide 1990 for commercial vegetable growers / 907: 1990
Caption title."Revised annually.""October 1989.
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