887 research outputs found
Color bimodality: Implications for galaxy evolution
We use a sample of 69726 galaxies from the SDSS to study the variation of the
bimodal color-magnitude (CM) distribution with environment. Dividing the galaxy
population by environment (Sigma_5) and luminosity (-23<M_r<-17), the u-r color
functions are modeled using double-Gaussian functions. This enables a
deconvolution of the CM distributions into two populations: red and blue
sequences. The changes with increasing environmental density can be separated
into two effects: a large increase in the fraction of galaxies in the red
distribution, and a small color shift in the CM relations of each distribution.
The average color shifts are 0.05+-0.01 and 0.11+-0.02 for the red and blue
distributions, respectively, over a factor of 100 in projected neighbor
density. The red fraction varies between about 0% and 70% for low-luminosity
galaxies and between about 50% and 90% for high-luminosity galaxies. This
difference is also shown by the variation of the luminosity functions with
environment. We demonstrate that the effects of environment and luminosity can
be unified. A combined quantity, Sigma_mod = Sigma_5/Mpc^{-2} + L_r/L_{-20.2},
predicts the fraction of red galaxies, which may be related to the probability
of transformation events. Our results are consistent with major interactions
(mergers and/or harassment) causing galaxies to transform from the blue to the
red distribution. We discuss this and other implications for galaxy evolution
from earlier results and model the effect of slow transformations on the color
functions.Comment: 14 pages, 8 figures, in AIP Conf. Proc., The New Cosmology, eds. R.
E. Allen et al. (aka. The Mitchell Symposium), see
http://proceedings.aip.org/proceedings/confproceed/743.jsp ; v2: replaced
Figure 5 which was incomplete in original submissio
Galaxy bimodality versus stellar mass and environment
We analyse a z<0.1 galaxy sample from the Sloan Digital Sky Survey focusing
on the variation of the galaxy colour bimodality with stellar mass and
projected neighbour density Sigma, and on measurements of the galaxy stellar
mass functions. The characteristic mass increases with environmental density
from about 10^10.6 Msun to 10^10.9 Msun (Kroupa IMF, H_0=70) for Sigma in the
range 0.1--10 per Mpc^2. The galaxy population naturally divides into a red and
blue sequence with the locus of the sequences in colour-mass and
colour-concentration index not varying strongly with environment. The fraction
of galaxies on the red sequence is determined in bins of 0.2 in log Sigma and
log mass (12 x 13 bins). The red fraction f_r generally increases continuously
in both Sigma and mass such that there is a unified relation: f_r =
F(Sigma,mass). Two simple functions are proposed which provide good fits to the
data. These data are compared with analogous quantities in semi-analytical
models based on the Millennium N-body simulation: the Bower et al. (2006) and
Croton et al. (2006) models that incorporate AGN feedback. Both models predict
a strong dependence of the red fraction on stellar mass and environment that is
qualitatively similar to the observations. However, a quantitative comparison
shows that the Bower et al. model is a significantly better match; this appears
to be due to the different treatment of feedback in central galaxies.Comment: 19 pages, 17 figures; accepted by MNRAS, minor change
Evaluating the impact of public housing after prison for a sex offence
This article evaluates the impact of housing assistance on the post-release pathways of people convicted of sex offences, in terms of a range of criminal justice outcomes and associated costs. Using linked administrative data from New South Wales government agencies, it compares outcomes and costs for two groups of formerly incarcerated sex offendersâone group who received public housing tenancies at some stage after their release, the other who only received private rental assistance. We find the public housing group had better criminal justice outcomes (e.g. fewer police incidents, court appearances, proven offences, days in custody and days on community-based orders) than the non-public housing group, achieved mostly at less cost to governments. The evidence, likely applicable in other jurisdictions with similar housing systems, strongly supports the increased provision of social housing to this group of ex-prisoners and, we hope, helps disarm the controversy that affects this area of policy in Australia and internationally
Supporting home care for the dying: an evaluation of healthcare professionals' perspectives of an individually tailored hospice at home service
AIMS AND OBJECTIVES: To explore health care professionals' perspective of hospice at home service that has different components, individually tailored to meet the needs of patients. BACKGROUND: Over 50% of adults diagnosed with a terminal illness and the majority of people who have cancer, prefer to be cared for and to die in their own home. Despite this, most deaths occur in hospital. Increasing the options available for patients, including their place of care and death is central to current UK policy initiatives. Hospice at home services aim to support patients to remain at home, yet there are wide variations in the design of services and delivery. A hospice at home service was developed to provide various components (accompanied transfer home, crisis intervention and hospice aides) that could be tailored to meet the individual needs of patients. DESIGN: An evaluation study. METHODS: Data were collected from 75 health care professionals. District nurses participated in one focus group (13) and 31 completed an electronic survey. Palliative care specialist nurses participated in a focus group (9). One hospital discharge co-ordinator and two general practitioners participated in semi-structured interviews and a further 19 general practitioners completed the electronic survey. RESULTS: Health care professionals reported the impact and value of each of the components of the service, as helping to support patients to remain at home, by individually tailoring care. They also positively reported that support for family carers appeared to enable them to continue coping, rapid access to the service was suggested to contribute to faster hospital discharges and the crisis intervention service was identified as helping patients remain in their own home, where they wanted to be. CONCLUSIONS: Health care professionals perceived that the additional individualised support provided by this service contributed to enabling patients to continue be cared for and to die at home in their place of choice. RELEVANCE TO CLINICAL PRACTICE: This service offers various components of a hospice at home service, enabling a tailor made package to meet individual and local area needs. Developing an individually tailored package of care appears to be able to meet specific needs
Welcome to the House of Fun: Work Space and Social Identity
Following the diffusion of HRM as the dominant legitimating managerial ideology, some employers have started to see the built working environment as a component in managing organisational culture and employee commitment. A good example is where the work space is designed to support a range of officially encouraged âfunâ activities at work. Drawing on recent research literature and from media reports of contemporary developments, this paper explores the consequences of such developments for employeesâ social identity formation and maintenance, with a particular focus on the office and customer service centre. Our analysis suggests that managementâs attempts to determine what is deemed fun may not only be resented by workers because it intrudes on their existing private identities but also because it seeks to re-shape their values and expression
Revealing components of the galaxy population through nonparametric techniques
The distributions of galaxy properties vary with environment, and are often
multimodal, suggesting that the galaxy population may be a combination of
multiple components. The behaviour of these components versus environment holds
details about the processes of galaxy development. To release this information
we apply a novel, nonparametric statistical technique, identifying four
components present in the distribution of galaxy H emission-line
equivalent-widths. We interpret these components as passive, star-forming, and
two varieties of active galactic nuclei. Independent of this interpretation,
the properties of each component are remarkably constant as a function of
environment. Only their relative proportions display substantial variation. The
galaxy population thus appears to comprise distinct components which are
individually independent of environment, with galaxies rapidly transitioning
between components as they move into denser environments.Comment: 12 pages, 10 figures, accepted for publication in MNRA
Solar-like oscillations in the G2 subgiant beta Hydri from dual-site observations
We have observed oscillations in the nearby G2 subgiant star beta Hyi using
high-precision velocity observations obtained over more than a week with the
HARPS and UCLES spectrographs. The oscillation frequencies show a regular comb
structure, as expected for solar-like oscillations, but with several l=1 modes
being strongly affected by avoided crossings. The data, combined with those we
obtained five years earlier, allow us to identify 28 oscillation modes. By
scaling the large frequency separation from the Sun, we measure the mean
density of beta Hyi to an accuracy of 0.6%. The amplitudes of the oscillations
are about 2.5 times solar and the mode lifetime is 2.3 d. A detailed comparison
of the mixed l=1 modes with theoretical models should allow a precise estimate
of the age of the star.Comment: 13 pages, 14 figures, accepted by ApJ. Fixed minor typo (ref to Fig
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