78 research outputs found
Detecting optical transients and variables with MeerLICHT
For a long time, the discovery of a transient in a one wavelength triggered observations in other wavelengths. Due to various constraints such as telescope access, scheduling and availability, and the need for human intervention, follow up observations of the transient event could take place long after the initial discovery. Due to the time-critical nature of some transients, with prompt emission that can fade rapidly, this delay in follow up observations can result in important information about the event being missed. Thus, the concept of MeerLICHT was born. MeerLICHT is an fully robotic, optical telescope whose main goal is the detection of transients in real-time. In collaboration with two legacy-style large survey projects (ThunderKAT and MeerTRAP) on MeerKAT (South Africa’s precursor to the Square Kilometre Array), MeerLICHT is the first fully dedicated telescope to follow another telescope in a different wavelength. Through linked-pointing, MeerLICHT and MeerKAT will provide simultaneous optical and radio data of the transient sky. This will provide invaluable information on emission at both wavelengths, including: the relation and evolution of emission from both wavelength windows, the discovery of optical counterparts of radio transients, the characterization of radio transients, and an early warning of radio transients using optical transients. This thesis contains the work on the development and implementation of the data processing pipeline for MeerLICHT. This data processing pipeline was developed for the automatic processing of data from MeerLICHT/BlackGEM for transient detection in real time
Rebalancing criminal justice : potentials and pitfalls for neighbourhood justice panels
The coalition government have pledged a commitment to a shift from 'Big Government' that presumes to know best, to the 'Big Society' that trusts in people for ideas and innovation to mend Britain's 'broken society'. While the policy implications of this shift remain opaque at this stage, further work has been undertaken to articulate what this strategy entails (see Cabinet Office, 2010). Five key themes have emerged which promise a dramatic shake-up of the system. This paper focuses on the theme that most closely relates to notions of 'Big Society' - restorative justice. In the current economic climate it is perhaps unsurprising that the coalition is supportive of restorative justice, as it mirrors the desire to redistribute power from central government to local communities and individuals. The Liberal Democrat experimentation with Community Justice Panels (now being referred to as Neighbourhood Justice Panels or NJPs) in the run-up to the general election has been highlighted as a measure that will be introduced to combat low-level offending and antisocial behaviour. This is given particular consideration as it involves local communities and victims themselves responding to offending behaviour rather than the state. NJPs, it is claimed, have a dramatic impact on recidivism rates in comparison to the traditional
criminal justice process and a corresponding reduction on police time and resources. However, as Crawford & Newburn (2002) highlight, England has traditionally adopted a
more punitive approach towards dealing with offending behaviour due to widespread public anxiety about crime and political competition to secure votes. Thus, this paper seeks to explore the potential implementational difficulties and resistance that may come
Assessment of hazard metrics for predicting field benthic invertebrate toxicity in the Detroit River, Ontario, Canada
Numerical sediment quality guidelines (SQGs) are frequently used to interpret site specific sediment chemistry and predict potential toxicity to benthic communities. These SQGs are useful for a screening line of evidence (LOE) that can be combined with other LOEs in a full weight of evidence (WOE) assessment of impacted sites. Three common multi-chemical hazard quotient methods (PEC-Qavg, PEC-Qmet and PEC-Qsum) and a novel (Hazard Score; HZD) approach were used in conjunction with a consensus based set of SQGs to evaluate the ability of different scoring metrics to predict the biological effects of sediment contamination under field conditions. Multivariate analyses were first used to categorize river sediments into distinct habitats based on a set of physicochemical parameters to include gravel, low and high flow sand and silt. For high flow sand and gravel, no significant dose-response relationships between numerically dominant species and various toxicity metric scores were observed. Significant dose-response relationships were observed for Chironomid abundances and toxicity scores in low flow sand and silt habitats. For silt habitats the HZD scoring metric provided the best predictor of Chironomid abundances compared to various PEC-Q methods according to goodness of fit tests. For low flow sand habitats, PEC-Qsum followed by HZD, provided the best predictors of Chironomid abundance. Differences in apparent Chironomid toxicity between the two habitats suggest habitat specific differences in chemical bioavailability and indicator taxa sensitivity. Using an index of biological integrity (IBI) method, the HZD, PEC-Qavg and PEC-Qmet approaches provided reasonable correlations with calculated IBI values in both silt and low flow sand habitats but not for gravel or high flow sands. Computation differences between the various multi-chemical toxicity scoring metrics and how this contributes to bias in different estimates of chemical mixture toxicity scores are discussed and compared
The distant, galaxy cluster environment of the short GRB 161104A at and a comparison to the short GRB host population
We present optical observations of the Swift short-duration gamma-ray burst
(GRB) GRB 161104A and its host galaxy at . We model the
multiband photometry and spectroscopy with the stellar population inference
code Prospector, and explore the posterior using nested sampling. We find that
the mass-weighted age ~Gyr, stellar mass
, metallicity , dust extinction mag, and
the star formation rate ~yr.
These properties, along with a prominent 4000 Angstrom break and optical
absorption lines classify this host as an early-type, quiescent galaxy. Using
Dark Energy Survey galaxy catalogues, we demonstrate that the host of GRB
161104A resides on the outskirts of a galaxy cluster at ,
situated Mpc from the likely brightest cluster galaxy. We also
present new modeling for 20 additional short GRB hosts ( of which
are early-type galaxies), finding population medians of and ~Gyr ( confidence).
We further find that the host of GRB 161104A is more distant, less massive, and
younger than the four other short GRB hosts known to be associated with galaxy
clusters. Cluster short GRBs have faint afterglows, in the lower
() of observed X-ray (optical) luminosities. We place a lower
limit on the fraction of short GRBs in galaxy clusters versus those in the
field of , consistent with the fraction of stellar mass
in galaxy clusters at redshifts .Comment: 20 pages, 9 figures, ApJ: Vol. 904, No.
Short GRB Host Galaxies. II. A Legacy Sample of Redshifts, Stellar Population Properties, and Implications for their Neutron Star Merger Origins
We present the stellar population properties of 69 short gamma-ray burst
(GRB) host galaxies, representing the largest uniformly-modeled sample to-date.
Using the Prospector stellar population inference code, we jointly fit
photometry and/or spectroscopy of each host galaxy. We find a population median
redshift of ( confidence), including 10 new or
revised photometric redshifts at . We further find a median
mass-weighted age of Gyr, stellar mass of
, star formation rate of
SFR=yr, stellar metallicity of
, and dust attenuation of
~mag (68\% confidence). Overall, the majority of
short GRB hosts are star-forming (), with small fractions that are
either transitioning () or quiescent (); however, we
observe a much larger fraction () of quiescent and transitioning
hosts at , commensurate with galaxy evolution. We find that
short GRB hosts populate the star-forming main sequence of normal field
galaxies, but do not include as many high-mass galaxies, implying that their
binary neutron star (BNS) merger progenitors are dependent on a combination of
host star formation and stellar mass. The distribution of ages and redshifts
implies a broad delay-time distribution, with a fast-merging channel at
and a decreased BNS formation efficiency at lower redshifts. If short GRB hosts
are representative of BNS merger hosts within the horizon of current
gravitational wave detectors, these results can inform future searches for
electromagnetic counterparts. All of the data and modeling products are
available on the BRIGHT website.Comment: 32 pages, 15 figures, 3 tables, accepted to Ap
- …