8,206 research outputs found

    Dwarf Galaxy Clustering and Missing Satellites

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    At redshifts around 0.1 the CFHT Legacy Survey Deep fields contain some 6x10^4 galaxies spanning the mass range from 10^5 to 10^12 Msun. We measure the stellar mass dependence of the two point correlation using angular measurements to largely bypass the errors, approximately 0.02 in the median, of the photometric redshifts. Inverting the power-law fits with Limber's equation we find that the auto-correlation length increases from a very low 0.4hMpc at 10^5.5 Msun to the conventional 4.5hMpc at 10^10.5 Msun. The power law fit to the correlation function has a slope which increases from gamma approximately 1.6 at high mass to gamma approximately 2.3 at low mass. The spatial cross-correlation of dwarf galaxies with more massive galaxies shows fairly similar trends, with a steeper radial dependence at low mass than predicted in numerical simulations of sub-halos within galaxy halos. To examine the issue of missing satellites we combine the cross-correlation measurements with our estimates of the low mass galaxy number density. We find on the average there are 60+/-20 dwarfs in sub-halos with M(total) > 10^7 Msun for a typical Local Group M(total)/M(stars)=30, corresponding to M/L_V approximately 100 for a galaxy with no recent star formation. The number of dwarfs per galaxy is about a factor of two larger than currently found for the Milky Way. Nevertheless, the average dwarf counts are about a factor of 30 below LCDM simulation results. The divergence from LCDM predictions is one of slope of the relation, approximately dN/dlnM approximately -0.5 rather than the predicted -0.9, not sudden onset at some characteristic scale. The dwarf galaxy star formation rates span the range from passive to bursting, which suggests that there are few completely dark halos.Comment: revised version submitted to Astrophysical Journa

    The Ha luminosity function and star formation rate up to z~1

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    We describe ISAAC/ESO-VLT observations of the Ha(6563) Balmer line of 33 field galaxies from the Canada-France Redshift Survey (CFRS) with redshifts selected between 0.5 and 1.1. We detect Ha in emission in 30 galaxies and compare the properties of this sample with the low-redshift sample of CFRS galaxies at z~0.2 (Tresse & Maddox 1998). We find that the Ha luminosity, L(Ha), is tightly correlated to M(B(AB)) in the same way for both the low- and high-redshift samples. L(Ha) is also correlated to L([OII]3727), and again the relation appears to be similar at low and high redshifts. The ratio L([OII])/L(Ha) decreases for brighter galaxies by as much as a factor 2 on average. Derived from the Ha luminosity function, the comoving Ha luminosity density increases by a factor 12 from =0.2 to =1.3. Our results confirm a strong rise of the star formation rate (SFR) at z<1.3, proportional to (1+z)^{4.1+/-0.3} (with H_0=50 km/s/Mpc, q_0=0.5). We find an average SFR(2800 Ang)/SFR(Ha) ratio of 3.2 using the Kennicutt (1998) SFR transformations. This corresponds to the dust correction that is required to make the near UV data consistent with the reddening-corrected Ha data within the self-contained, I-selected CFRS sample.Comment: 16 pages, 16 figures and 3 tables included, figures and text updated, same results as in the 1st version, accepted in MNRA

    “Wrapping myself in cotton wool“: Australian women's experience of being diagnosed with vasa praevia

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    © 2014 Javid et al.; licensee BioMed Central Ltd. Background: Vasa praevia (VP) is an obstetric condition that is associated with significant perinatal mortality and morbidity. Although the incidence of VP is low, it is one of the few causes of perinatal death that can be potentially prevented through detection and appropriate care. The experience of women diagnosed with or suspected to have VP is largely unknown. The aim of this study was to explore the experiences and impact that a diagnosis or suspected diagnosis of VP had on a group of Australian women.Method: A qualitative study using a descriptive exploratory design was conducted and Australian women diagnosed with VP were recruited via online methods in 2012. An inductive approach was undertaken and interviews were analysed using the stages of thematic analysis. Results: Of the 14 women interviewed, 11 were diagnosed with VP during pregnancy with 5 subsequently found not to have VP (non-confirmed diagnosis). Three women were diagnosed during childbirth with one neonatal death. Five major themes were identified: feeling like a ticking time bomb; getting diagnosis right; being taken seriously; coping with inconsistent information; and, just a massive relief when it was all over.Conclusions: This is the first study to describe women's experience of being diagnosed with or suspected to have VP. The findings from this research reveal the dilemmas these women face even if their baby is ultimately born healthy. Their need for clear and consistent information, sensitive care, support and continuity is evident. Clinicians can use these findings in developing information, counselling and models of care for these women

    Processes and priorities in planning mathematics teaching

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    Insights into teachers' planning of mathematics reported here were gathered as part of a broader project examining aspects of the implementation of the Australian curriculum in mathematics (and English). In particular, the responses of primary and secondary teachers to a survey of various aspects of decisions that inform their use of curriculum documents and assessment processes to plan their teaching are discussed. Teachers appear to have a clear idea of the overall topic as the focus of their planning, but they are less clear when asked to articulate the important ideas in that topic. While there is considerable diversity in the processes that teachers use for planning and in the ways that assessment information informs that planning, a consistent theme was that teachers make active decisions at all stages in the planning process. Teachers use a variety of assessment data in various ways, but these are not typically data extracted from external assessments. This research has important implications for those responsible for supporting teachers in the transition to the Australian Curriculum: Mathematic

    Assessment of Adolescents’ Victimization, Aggression, and Problem Behaviors: Evaluation of the Problem Behavior Frequency Scale

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    This study evaluated the Problem Behavior Frequency Scale (PBFS), a self-report measure designed to assess adolescents’ frequency of victimization, aggression, and other problem behaviors. Analyses were conducted on a sample of 5,532 adolescents from 37 schools at 4 sites. About half (49%) of participants were male; 48% self-identified as Black non-Hispanic; 21% as Hispanic, 18% as White non-Hispanic. Adolescents completed the PBFS and measures of beliefs and values related to aggression, and delinquent peer associations at the start of the 6th grade and over 2 years later. Ratings of participants’ behavior were also obtained from teachers on the Behavioral Assessment System for Children. Confirmatory factor analyses supported a 7-factor model that differentiated among 3 forms of aggression (physical, verbal, and relational), 2 forms of victimization (overt and relational), drug use, and other delinquent behavior. Support was found for strong measurement invariance across gender, sites, and time. The PBFS factors generally showed the expected pattern of correlations with teacher ratings of adolescents’ behavior and self-report measures of relevant constructs

    Clustering of supernova Ia host galaxies

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    For the first time the cross-correlation between type Ia supernova host galaxies and surrounding field galaxies is measured using the Supernova Legacy Survey sample. Over the z=0.2 to 0.9 redshift range we find that supernova hosts are correlated an average of 60% more strongly than similarly selected field galaxies over the 3-100 arcsec range and about a factor of 3 more strongly below 10 arcsec. The correlation errors are empirically established with a jackknife analysis of the four SNLS fields. The hosts are more correlated than the field at a significance of 99% in the fitted amplitude and slope, with the point-by-point difference of the two correlation functions having a reduced χ2\chi^2 for 8 degrees of freedom of 4.3, which has a probability of random occurrence of less than 3x10^{-5}. The correlation angle is 1.5+/-0.5 arcsec, which deprojects to a fixed co-moving correlation length of approximately 6.5+/- 2/h mpc. Weighting the field galaxies with the mass and star formation rate supernova frequencies of the simple A+B model produces good agreement with the observed clustering. We conclude that these supernova clustering differences are primarily the expected outcome of the dependence of supernova rates on galaxy masses and stellar populations with their clustering environment.Comment: ApJ (Letts) accepte

    Designing for change: The poetic potential of responsive architecture

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    The integration of responsive components in architecture offers the potential to enhance the experience of the building by giving expression to fleeting, changeable aspects of the environment. Responsive buildings enable a physical response to changes in the environment through specific building elements; in rare cases these responsive elements become an integral and poetic element of a culturally significant work of architecture. In this paper I examine two types of responsiveness, one which concerns the changing environment and another the activities and needs of the building׳s inhabitants. I look at two examples of buildings that illustrate a potential poetic role for architectural components responding to these two types of change, and propose that architects will need to acquire experience with designing for specific rates, scales and types of change before responsive elements will more frequently appear as a poetic and integral part of the building

    Invariant Peano curves of expanding Thurston maps

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    We consider Thurston maps, i.e., branched covering maps f ⁣:S2S2f\colon S^2\to S^2 that are postcritically finite. In addition, we assume that ff is expanding in a suitable sense. It is shown that each sufficiently high iterate F=fnF=f^n of ff is semi-conjugate to zd ⁣:S1S1z^d\colon S^1\to S^1, where dd is equal to the degree of FF. More precisely, for such an FF we construct a Peano curve γ ⁣:S1S2\gamma\colon S^1\to S^2 (onto), such that Fγ(z)=γ(zd)F\circ \gamma(z) = \gamma(z^d) (for all zS1z\in S^1).Comment: 63 pages, 12 figure

    Schizophrenia and the progression of emotional expression in relation to others

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    Gaining an improved understanding of people diagnosed with schizophrenia has the potential to influence priorities for therapy. Psychosis is commonly understood through the perspective of the medical model. However, the experience of social context surrounding psychosis is not well understood. In this research project we used a phenomenological methodology with a longitudinal design to interview 7 participants across a 12-month period to understand the social experiences surrounding psychosis. Eleven themes were explicated and divided into two phases of the illness experience: (a) transition into emotional shutdown included the experiences of not being acknowledged, relational confusion, not being expressive, detachment, reliving the past, and having no sense of direction; and (b) recovery from emotional shutdown included the experiences of being acknowledged, expression, resolution, independence, and a sense of direction. The experiential themes provide clinicians with new insights to better assess vulnerability, and have the potential to inform goals for therapy
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