1,277 research outputs found
Extreme Starlight Polarization in a Region with Highly Polarized Dust Emission
Galactic dust emission is polarized at unexpectedly high levels, as revealed
by Planck. The origin of the observed polarization fractions can
be identified by characterizing the properties of optical starlight
polarization in a region with maximally polarized dust emission. We measure the
R-band linear polarization of 22 stars in a region with a submillimeter
polarization fraction of . A subset of 6 stars is also measured in
the B, V and I bands to investigate the wavelength dependence of polarization.
We find that starlight is polarized at correspondingly high levels. Through
multiband polarimetry we find that the high polarization fractions are unlikely
to arise from unusual dust properties, such as enhanced grain alignment.
Instead, a favorable magnetic field geometry is the most likely explanation,
and is supported by observational probes of the magnetic field morphology. The
observed starlight polarization exceeds the classical upper limit of
%mag and is at least
as high as 13%mag that was inferred from a joint analysis of Planck
data, starlight polarization and reddening measurements. Thus, we confirm that
the intrinsic polarizing ability of dust grains at optical wavelengths has long
been underestimated.Comment: Accepted by A&AL, data to appear on CDS after publication. 6 page
Towards real-time classification of astronomical transients
Exploration of time domain is now a vibrant area of research in astronomy, driven by the advent of digital synoptic sky surveys. While panoramic surveys can detect variable or transient events, typically some follow-up observations are needed; for short-lived phenomena, a rapid response is essential. Ability to automatically classify and prioritize transient events for follow-up studies becomes critical as the data rates increase. We have been developing such methods using the data streams from the Palomar-Quest survey, the Catalina Sky Survey and others, using the VOEventNet framework. The goal is to automatically classify transient events, using the new measurements, combined with archival data (previous and multi-wavelength measurements), and contextual information (e.g., Galactic or ecliptic latitude, presence of a possible host galaxy nearby, etc.); and to iterate them dynamically as the follow-up data come in (e.g., light curves or colors). We have been investigating Bayesian methodologies for classification, as well as discriminated follow-up to optimize the use of available resources, including Naive Bayesian approach, and the non-parametric Gaussian process regression. We will also be deploying variants of the traditional machine learning techniques such as Neural Nets and Support Vector Machines on datasets of reliably classified transients as they build up
Canton Connections: A University-Community Partnership for Post-Disaster Revitalization
Back-to-back hurricanes prompted the creation of a partnership between Western Carolina University and an affected community in western North Carolina. The partnership was designed to promote the economic, social, and cultural revitalization of the community while creating opportunities for civic engagement and enriched student learning. The principal stakeholders in the partnership were the university and the municipal government, representing the community at large. The partners undertook several projects over a three-year period as part of a comprehensive, multifaceted initiative. In this article, the authors discuss the benefits and impact of the projects on participants and the community. They also share the insights gained and lessons learned from the initiative and comment briefly on factors inherent in effective university-community partnerships
A New Detection of Extragalactic Anomalous Microwave Emission in a Compact, Optically-Faint Region of NGC\,4725
We discuss the nature of a discrete, compact radio source (NGC 4725 B)
located 1.9 kpc from the nucleus in the nearby star-forming galaxy NGC
4725, which we believe to be a new detection of extragalactic Anomalous
Microwave Emission (AME). Based on detections at 3, 15, 22, 33, and 44 GHz, NGC
4725 B is a Jy radio source peaking at 33 GHz. While the source
is not identified in photometry, we detect counterparts in the
mid-infrared /IRAC bands (3.6, 4.5, 5.8, 8.0 m) that appear to be
associated with dust emission in the central region of NGC 4725. Consequently,
we conclude that NGC 4725 B is a new detection of AME, and very similar to a
recent detection of AME in an outer-disk star-forming region in NGC 6946. We
find that models of electric dipole emission from rapidly rotating ultra-small
grains are able to reproduce the radio spectrum for reasonable interstellar
medium conditions. Given the lack of an optical counterpart and the shape of
the radio spectrum, NGC 4725 B appears consistent with a nascent star-forming
region in which young ( Myr) massive stars are still highly
enshrouded by their natal cocoons of gas and dust with insufficient supernovae
occurring to produce a measurable amount of synchrotron emission.Comment: 10 pages, 4 figures, accepted for publication in Ap
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