419 research outputs found
Alleviating Poverty by Empowering Women Through Business Model Innovation: Manufacturing & Service Operations Management Insights and Opportunities
*Manufacturing & Service Operations Management (M&SOM)* has published papers of importance for poverty alleviation. Yet, rich opportunities for impactful research remain as yet untapped. Operations management (OM) insights suggest business model innovations that alleviate poverty by simultaneously empowering women, protecting natural systems or mitigating pollution, increasing incomes, and creating low-cost, high-quality products or services. OM researchers can help empower women and overcome poverty by developing, testing, refining and disseminating such business model innovations
Dispersion of Magnetic Fields in Molecular Clouds. IV - Analysis of Interferometry Data
We expand on the dispersion analysis of polarimetry maps toward applications to interferometry data. We show how the filtering of low spatial frequencies can be accounted for within the idealized Gaussian turbulence model, initially introduced for single-dish data analysis, to recover reliable estimates for correlation lengths of magnetized turbulence, as well as magnetic field strengths (plane-of-the-sky component) using the Davis–Chandrasekhar–Fermi method. We apply our updated technique to TADPOL/CARMA data obtained on W3(OH), W3 Main, and DR21(OH). For W3(OH), our analysis yields a turbulence correlation length δ ≃ 19 mpc, a ratio of turbulent-to-total magnetic energy 〈B〉_^2_t/〈B^2〉 ≃ 0.58, and a magnetic field strength B_0 ~ 1.1 mG for W3 Main δ ≃ 22mpc, 〈B_t^2〉/〈B^2〉 ≃ 0.74, and B_0 ~ 0.7 mG while for DR21(OH) δ ≃ 12 mpc, 〈B_t^2〉/〈B^2〉 ≃ 0.70, and B_0 ~ 1.2 mG
An extremely high velocity molecular jet surrounded by an ionized cavity in the protostellar source Serpens SMM1
We report ALMA observations of a one-sided, high-velocity (80 km
s) CO() jet powered by the intermediate-mass
protostellar source Serpens SMM1-a. The highly collimated molecular jet is
flanked at the base by a wide-angle cavity; the walls of the cavity can be seen
in both 4 cm free-free emission detected by the VLA and 1.3 mm thermal dust
emission detected by ALMA. This is the first time that ionization of an outflow
cavity has been directly detected via free-free emission in a very young,
embedded Class 0 protostellar source that is still powering a molecular jet.
The cavity walls are ionized either by UV photons escaping from the accreting
protostellar source, or by the precessing molecular jet impacting the walls.
These observations suggest that ionized outflow cavities may be common in Class
0 protostellar sources, shedding further light on the radiation, outflow, and
jet environments in the youngest, most embedded forming stars.Comment: 6 pages, 4 figures, accepted for publication in the Astrophysical
Journal Letter
Giant Molecular Clouds in M33 - I. BIMA All Disk Survey
We present the first interferometric CO(J=1->0) map of the entire H-alpha
disk of M33. The 13" diameter synthesized beam corresponds to a linear
resolution of 50 pc, sufficient to distinguish individual giant molecular
clouds (GMCs). From these data we generated a catalog of 148 GMCs with an
expectation that no more than 15 of the sources are spurious. The catalog is
complete down to GMC masses of 1.5 X 10^5 M_sun and contains a total mass of
2.3 X 10^7 M_sun. Single dish observations of CO in selected fields imply that
our survey detects ~50% of the CO flux, hence that the total molecular mass of
M33 is 4.5 X 10^7 M_sun, approximately 2% of the HI mass. The GMCs in our
catalog are confined largely to the central region (R < 4 kpc). They show a
remarkable spatial and kinematic correlation with overdense HI filaments; the
geometry suggests that the formation of GMCs follows that of the filaments. The
GMCs exhibit a mass spectrum dN/dM ~ M^(-2.6 +/- 0.3), considerably steeper
than that found in the Milky Way and in the LMC. Combined with the total mass,
this steep function implies that the GMCs in M33 form with a characteristic
mass of 7 X 10^4 M_sun. More than 2/3 of the GMCs have associated HII regions,
implying that the GMCs have a short quiescent period. Our results suggest the
rapid assembly of molecular clouds from atomic gas, with prompt onset of
massive star formation.Comment: 19 pages, Accepted for Publication in the Astrophysical Journal
Supplemen
ALMA observations of dust polarization and molecular line emission from the Class 0 protostellar source Serpens SMM1
We present high angular resolution dust polarization and molecular line
observations carried out with the Atacama Large Millimeter/submillimeter Array
(ALMA) toward the Class 0 protostar Serpens SMM1. By complementing these
observations with new polarization observations from the Submillimeter Array
(SMA) and archival data from the Combined Array for Research in Millimeter-wave
Astronomy (CARMA) and the James Clerk Maxwell Telescopes (JCMT), we can compare
the magnetic field orientations at different spatial scales. We find major
changes in the magnetic field orientation between large (~0.1 pc) scales --
where the magnetic field is oriented E-W, perpendicular to the major axis of
the dusty filament where SMM1 is embedded -- and the intermediate and small
scales probed by CARMA (~1000 AU resolution), the SMA (~350 AU resolution), and
ALMA (~140 AU resolution). The ALMA maps reveal that the redshifted lobe of the
bipolar outflow is shaping the magnetic field in SMM1 on the southeast side of
the source; however, on the northwestern side and elsewhere in the source, low
velocity shocks may be causing the observed chaotic magnetic field pattern.
High-spatial-resolution continuum and spectral-line observations also reveal a
tight (~130 AU) protobinary system in SMM1-b, the eastern component of which is
launching an extremely high-velocity, one-sided jet visible in both CO(2-1) and
SiO(5-4); however, that jet does not appear to be shaping the magnetic field.
These observations show that with the sensitivity and resolution of ALMA, we
can now begin to understand the role that feedback (e.g., from protostellar
outflows) plays in shaping the magnetic field in very young, star-forming
sources like SMM1.Comment: 15 pages, 6 figures, 4 tables, 1 appendix. Accepted for publication
in the Astrophysical Journal. Materials accessible in the online version of
the (open-access) ApJ article include the FITS files used to make the ALMA
image in Figure 1(d), and a full, machine-readable version of Table
A Parallactic Distance of 389 +24/-21 parsecs to the Orion Nebula Cluster from Very Long Baseline Array Observations
We determine the parallax and proper motion of the flaring, non-thermal radio
star GMR A, a member of the Orion Nebula Cluster, using Very Long Baseline
Array observations. Based on the parallax, we measure a distance of 389 +24/-21
parsecs to the source. Our measurement places the Orion Nebula Cluster
considerably closer than the canonical distance of 480 +/- 80 parsecs
determined by Genzel et al. (1981). A change of this magnitude in distance
lowers the luminosities of the stars in the cluster by a factor of ~ 1.5. We
briefly discuss two effects of this change--an increase in the age spread of
the pre-main sequence stars and better agreement between the zero-age
main-sequence and the temperatures and luminosities of massive stars.Comment: 10 pages, 4 figures, emulateapj, accepted to Ap
Unusually Luminous Giant Molecular Clouds in the Outer Disk of M33
We use high spatial resolution (~7pc) CARMA observations to derive detailed
properties for 8 giant molecular clouds (GMCs) at a galactocentric radius
corresponding to approximately two CO scale lengths, or ~0.5 optical radii
(r25), in the Local Group spiral galaxy M33. At this radius, molecular gas
fraction, dust-to-gas ratio and metallicity are much lower than in the inner
part of M33 or in a typical spiral galaxy. This allows us to probe the impact
of environment on GMC properties by comparing our measurements to previous data
from the inner disk of M33, the Milky Way and other nearby galaxies. The outer
disk clouds roughly fall on the size-linewidth relation defined by
extragalactic GMCs, but are slightly displaced from the luminosity-virial mass
relation in the sense of having high CO luminosity compared to the inferred
virial mass. This implies a different CO-to-H2 conversion factor, which is on
average a factor of two lower than the inner disk and the extragalactic
average. We attribute this to significantly higher measured brightness
temperatures of the outer disk clouds compared to the ancillary sample of GMCs,
which is likely an effect of enhanced radiation levels due to massive star
formation in the vicinity of our target field. Apart from brightness
temperature, the properties we determine for the outer disk GMCs in M33 do not
differ significantly from those of our comparison sample. In particular, the
combined sample of inner and outer disk M33 clouds covers roughly the same
range in size, linewidth, virial mass and CO luminosity than the sample of
Milky Way GMCs. When compared to the inner disk clouds in M33, however, we find
even the brightest outer disk clouds to be smaller than most of their inner
disk counterparts. This may be due to incomplete sampling or a potentially
steeper cloud mass function at larger radii.Comment: Accepted for Publication in ApJ; 7 pages, 4 figure
Untangling drivers for supplier environmental and social responsibility:An investigation in Philips Lighting's Chinese supply chain
This study unpacks the environmental and social dimensions of supplier responsibility and links each dimension to distinct drivers. Using stakeholder theory and the relational view, we distinguish between two main drivers: stakeholder pressures (i.e., from regulatory agencies, buying firms, and nongovernmental organizations) and relational mechanisms offered by multinational companies (MNCs) (i.e., lean trainings and relational capital). We used a multi-method research design to study how these drivers uniquely influence supplier responsibility in an emerging-country context. An in-depth case study with Philips Lighting and 10 of its Chinese suppliers reveals causal inferences that link stakeholder and relational drivers with each responsibility dimension (environmental vs. social). Audit and survey data from Philips Lighting's 134 Chinese suppliers, complemented with four archival databases, bolster these inferences. Overall, the results show that supplier environmental responsibility can be fostered through both stakeholder pressures and relational drivers; whereas, supplier social responsibility is much harder to address. The integrated methods offer a fuller, more comprehensive understanding of the specifics of supplier responsibility in China and also provide recommendations for MNCs that seek to improve it
A Feature Movie of SiO Emission 20-100 AU from the Massive Young Stellar Object Orion Source I
We present multi-epoch VLBA imaging of the 28SiO v=1 & v=2, J=1-0 maser
emission toward the massive YSO Orion Source I. Both SiO transitions were
observed simultaneously with an angular resolution of ~0.5 mas (~0.2 AU for
d=414 pc). Here we explore the global properties and kinematics of the emission
through two 19-epoch animated movies spanning 21 months (2001 March 19 to 2002
December 10). These movies provide the most detailed view to date of the
dynamics and temporal evolution of molecular material within ~20-100 AU of a
massive (~>8M_sun) YSO. The bulk of the SiO masers surrounding Source I lie in
an X-shaped locus; emission in the South/East arms is predominantly blueshifted
and in the North and West is predominantly redshifted. In addition, bridges of
intermediate-velocity emission connect the red and blue sides of the emission
distribution. We have measured proper motions of >1000 maser features and find
a combination of radially outward migrations along the four arms and motions
tangent to the bridges. We interpret the SiO masers as arising from a
wide-angle bipolar wind emanating from a rotating, edge-on disk. The detection
of maser features along extended, curved filaments suggests that magnetic
fields may play a role in launching and/or shaping the wind. Our observations
appear to support a picture in which stars with M ~>8 M_sun form via
disk-mediated accretion. However, we cannot rule out that the Source I disk may
have been formed or altered following a close encounter. (Abridged).Comment: Accepted to ApJ (January 2010); a full resolution version along with
two accompanying GIF movies may be found at
http://www.cfa.harvard.edu/kalypso
- …