801 research outputs found
Extending conceptualisations of the diversity and value of extracurricular activities: a cultural capital approach to graduate outcomes
This report presents the findings from the research project Extending conceptualisations of the diversity and value of extra curricular activities: a cultural capital approach to graduate outcomes. Very little research has directly addressed the question of what constitutes extra-curricular activities (ECA), the extent to which students engage in ECA, and how students experience and conceptualise benefits from their engagement. Nor is there research that looks at how staff understand ECA. This research sought to address these questions from a cultural capital approach. Traditionally conceived ECA include campus-based cultural and sporting activities and volunteering. An awareness is required of the fact that many students work for economic reasons, continue their faith and caring activities, and continue to live at home. The researchers were interested in the possible differential recognition and valuing of activities undertaken by different groups of students. This research explores issues of inter-generational capital that might shape both the capacities to participate and how students understood the benefits
Into the central 10 pc of the most distant known radio quasar. VLBI imaging observations of J1429+5447 at z=6.21
Context: There are about 60 quasars known at redshifts z>5.7 to date. Only
three of them are detected in the radio above 1 mJy flux density at 1.4 GHz
frequency. Among them, J1429+5447 (z=6.21) is the highest-redshift radio quasar
known at present. These rare, distant, and powerful objects provide important
insight into the activity of the supermassive black holes in the Universe at
early cosmological epochs, and on the physical conditions in their environment.
Aims: We studied the compact radio structure of J1429+5447 on the
milli-arcsecond (mas) angular scale, in order to compare the structural and
spectral properties with those of other two z~6 radio-loud quasars, J0836+0054
(z=5.77) and J1427+3312 (z=6.12). Methods: We performed Very Long Baseline
Interferometry (VLBI) imaging observations of J1429+5447 with the European VLBI
Network (EVN) at 1.6 GHz on 2010 June 8, and at 5 GHz on 2010 May 27. Results:
Based on its observed radio properties, the compact but somewhat resolved
structure on linear scales of <100 pc, and the steep spectrum, the quasar
J1429+5447 is remarkably similar to J0836+0054 and J1427+3312. To answer the
question whether the compact steep-spectrum radio emission is a "universal"
feature of the most distant radio quasars, it is essential to study more, yet
to be discovered radio-loud active galactic nuclei at z>6.Comment: 4 pages, 2 figures, accepted for publication as a Letter to the
editor in Astronomy & Astrophyic
The radio luminosity function of radio-loud quasars from the 7C Redshift Survey
We present a complete sample of 24 radio-loud quasars (RLQs) from the new 7C
Redshift Survey. Every quasar with a low-frequency (151 MHz) radio flux-density
S_151 > 0.5 Jy in two regions of the sky covering 0.013 sr is included; 23 of
these have sufficient extended flux to meet the selection criteria, 18 of these
have steep radio spectra (hereafter denoted as SSQs). The key advantage of this
sample over most samples of RLQs is the lack of an optical magnitude limit. By
combining the 7C and 3CRR samples, we have investigated the properties of RLQs
as a function of redshift z and radio luminosity L_151.
We derive the radio luminosity function (RLF) of RLQs and find that the data
are well fitted by a single power-law with slope alpha_1=1.9. We find that
there must be a break in the RLQ RLF at log_10(L_151 / W Hz^-1 sr^-1) < 27, in
order for the models to be consistent with the 7C and 6C source counts. The
z-dependence of the RLF follows a one-tailed gaussian which peaks at z=1.7. We
find no evidence for a decline in the co-moving space density of RLQs at higher
redshifts.
A positive correlation between the radio and optical luminosities of SSQs is
observed, confirming a result of Serjeant et al. (1998). We are able to rule
out this correlation being due to selection effects or biases in our combined
sample. The radio-optical correlation and best-fit model RLF enable us to
estimate the distribution of optical magnitudes of quasars in samples selected
at low radio frequencies. We conclude that for samples with S_151 < 1 Jy one
must use optical data significantly deeper than the POSS-I limit (R approx 20),
in order to avoid severe incompleteness.Comment: 28 pages with 13 figures. To appear in MNRA
Extremely red radio galaxies
At least half the radio galaxies at z>1 in the 7C Redshift Survey have
extremely red colours (R-K>5), consistent with stellar populations which formed
at high redshift (z>5). We discuss the implications of this for the evolution
of massive galaxies in general and for the fraction of near-IR-selected EROs
which host AGN, a result which is now being tested by deep, hard X-ray surveys.
The conclusion is that many massive galaxies undergo at least two active
phases: one at z~5 when the black hole and stellar bulge formed and another at
z~1-2 when activity is triggered by an event such as an interaction or merger.Comment: 6 pages, 2 figures, to appear in the proceedings of the workshop on
"QSO hosts and their environments", IAA, Granada, 10-12 Jan 2001, Ed. I.
Marque
Near-zone sizes and the rest frame extreme ultra-violet spectral index of the highest redshift quasars
The discovery of quasars with redshifts higher than six has prompted a great
deal of discussion in the literature regarding the role of quasars, both as
sources of reionization, and as probes of the ionization state of the IGM.
However the extreme ultra-violet (EUV) spectral index cannot be measured
directly for high redshift quasars owing to absorption at frequencies above the
Lyman limit, and as a result, studies of the impact of quasars on the
intergalactic medium during reionization must assume a spectral energy
distribution in the extreme ultra-violet based on observations at low redshift,
z<1. In this paper we use regions of high Ly-alpha transmission (near-zones)
around the highest redshift quasars to measure the quasar EUV spectral index at
z~6. We jointly fit the available observations for variation of near-zone size
with both redshift and luminosity, and propose that the observed relation
provides evidence for an EUV spectral index that varies with absolute magnitude
in the high redshift quasar sample, becoming softer at higher luminosity. Using
a large suite of detailed numerical simulations we find that the typical value
of spectral index for a luminous quasar at z~6 is constrained to be
alpha=1.3+/-0.4 for a specific luminosity of the form L\propto\nu^{-alpha}. We
find the scatter in spectral index among individual quasars to be in the range
~0.75-1.25. These values are in agreement with direct observations at low
redshift, and indicate that there has been no significant evolution in the EUV
spectral index of quasars over 90% of cosmic time.Comment: 12 pages, 8 figures. Submitted to MNRA
Dealing with the distress of people with intellectual disabilities reporting sexual assault and rape
When police officers interview people with intellectual disabilities who allege sexual assault and rape, they must establish rapport with the interviewee but deal with their distress in a way that does not compromise the interview’s impartiality and its acceptability in court. Inspection of 19 videotaped interviews from an English police force’s records reveals that the officers deal with expressed distress by choosing among three practices: minimal (e.g. okay) or no acknowledgement, acknowledging the expressed emotion as a matter of the complainant’s difficulty in proceeding (e.g. take your time) and rarely (and only if the complainants were apparently unable to resume their talk) explicit reference to their emotion (e.g. it’s obviously upsetting for you). We discuss these practices as ways of managing the conflicting demands of rapport and evidence-gathering
The importance of radio sources in accounting for the highest mass black holes
The most massive black holes lie in the most massive elliptical galaxies, and
at low-z all radio-loud AGNs lie in giant ellipticals. This strongly suggests a
link between radio-loudness and black hole mass. We argue that the increase in
the radio-loud fraction with AGN luminosity in optically-selected quasar
samples is consistent with this picture. We also use the ratio of black holes
today to quasars at z~2 to conclude that the most bolometrically-luminous AGN,
either radio-loud or radio quiet, are constrained to have lifetimes <~10^8 yr.
If radio sources are associated with black holes of >~10^9 M_sun at all
redshifts, then the same lifetime constraint applies to all radio sources with
luminosities above L_5GHz ~ 10^24 W/Hz/sr.Comment: 6 pages, 2 figures. To appear in "Lifecycles of Radio Galaxies", ed
J. Biretta et al., New Astronomy Review
Mid-infrared sources in the ELAIS Deep X-ray Survey
We present a cross‐correlation of the European Large Area Infrared Space Observatory (ISO) survey (ELAIS) with the ELAIS Deep X‐ray Survey of the N1 and N2 fields. There are seven Chandra point sources with matches in the ELAIS Final Analysis 15‐μm catalogue, out of a total of 28 extragalactic ISO sources present in the Chandra fields. Five of these are consistent with active galactic nuclei (AGN) giving an AGN fraction of ∼19 per cent in the 15‐μm flux range 0.8–6 mJy. We have co‐added the hard X‐ray fluxes of the individually undetected ISO sources and find a low significance detection consistent with star formation in the remaining population. We combine our point source cross‐correlation fraction with the XMM–Newton observations of the Lockman Hole and Chandra observations of the Hubble Deep Field North to constrain source count models of the mid‐infrared galaxy population. The low dust‐enshrouded AGN fraction in ELAIS implied by the number of cross‐identifications between the ELAIS mid‐infrared sample and the Chandra point sources is encouraging for the use of mid‐infrared surveys to constrain the cosmic star formation history, provided there are not further large undetected populations of Compton‐thick AGN
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