25 research outputs found
Complex Radio Spectral Energy Distributions in Luminous and Ultraluminous Infrared Galaxies
We use the Expanded Very Large Array to image radio continuum emission from
local luminous and ultraluminous infrared galaxies (LIRGs and ULIRGs) in 1 GHz
windows centered at 4.7, 7.2, 29, and 36 GHz. This allows us to probe the
integrated radio spectral energy distribution (SED) of the most energetic
galaxies in the local universe. The 4-8 GHz flux densities agree well with
previous measurements. They yield spectral indices \alpha \approx -0.67 (where
F_\nu \propto \nu^\alpha) with \pm 0.15 (1\sigma) scatter, typical of
nonthermal (synchrotron) emission from star-forming galaxies. The contrast of
our 4-8 GHz data with literature 1.5 and 8.4 GHz flux densities gives further
evidence for curvature of the radio SED of U/LIRGs. The SED appears flatter
near \sim 1 GHz than near \sim 6 GHz, suggesting significant optical depth
effects at the lower frequencies. The high frequency (28-37 GHz) flux densities
are low compared to extrapolations from the 4-8 GHz data. We confirm and extend
to higher frequency a previously observed deficit of high frequency radio
emission for luminous starburst galaxies.Comment: 7 pages, 3 figures, 1 table, accepted for publication in the EVLA
Special Issue of ApJ Letter
Cosmological origin of anomalous radio background
The ARCADE 2 collaboration has reported a significant excess in the isotropic radio background, whose homogeneity cannot be reconciled with clustered sources. This suggests a cosmological origin prior to structure formation. We investigate several potential mechanisms and show that injection of relativistic electrons through late decays of a metastable particle can give rise to the observed excess radio spectrum through synchrotron emission. However, constraints from the cosmic microwave background (CMB) anisotropy, on injection of charged particles and on the primordial magnetic field, present a challenge. The simplest scenario is with a gtrsim9 GeV particle decaying into e+e− at a redshift of z ~ 5, in a magnetic field of ~ 5μG, which exceeds the CMB B-field constraints, unless the field was generated after decoupling. Decays into exotic millicharged particles can alleviate this tension, if they emit synchroton radiation in conjunction with a sufficiently large background magnetic field of a dark U(1)' gauge field
Workplace violence in a large correctional health servce in New South Wales, Australia: a retrospective review of incident management records
BackgroundLittle is known about workplace violence among correctional health professionals. This studyaimed to describe the patterns, severity and outcomes of incidents of workplace violenceamong employees of a large correctional health service, and to explore the help-seekingbehaviours of staff following an incident.MethodsThe study setting was Justice Health, a statutory health corporation established to providehealth care to people who come into contact with the criminal justice system in New SouthWales, Australia. We reviewed incident management records describing workplace violenceamong Justice Health staff. The three-year study period was 1/7/2007-30/6/2010.ResultsDuring the period under review, 208 incidents of workplace violence were recorded. Verbalabuse (71%) was more common than physical abuse (29%). The most (44%) incidents ofworkplace violence (including both verbal and physical abuse) occurred in adult maleprisons, although the most (50%) incidents of physical abuse occurred in a forensic hospital.Most (90%) of the victims were nurses and two-thirds were females. Younger employees andmales were most likely to be a victim of physical abuse. Preparing or dispensing medicationand attempting to calm and/or restrain an aggressive patient were identified as ‘high risk’work duties for verbal abuse and physical abuse, respectively. Most (93%) of the incidents ofworkplace violence were initiated by a prisoner/patient. Almost all of the incidents receivedeither a medium (46%) or low (52%) Severity Assessment Code. Few victims of workplaceviolence incurred a serious physical injury – there were no workplace deaths during the studyperiod. However, mental stress was common, especially among the victims of verbal abuse(85%). Few (6%) victims of verbal abuse sought help from a health professional.ConclusionsAmong employees of a large correctional health service, verbal abuse in the workplace wassubstantially more common than physical abuse. The most incidents of workplace violenceoccurred in adult male prisons. Review of the types of adverse health outcomes experiencedby the victims of workplace violence and the assessments of severity assigned to violentincidents suggests that, compared with health care settings in the community, correctionalsettings are fairly safe places in which to practice