1,096 research outputs found
Social Presence, Identity, and Online Learning Research: Research Development and Needs
Scholars across many disciplines have grappled with questions of what it means for a person to be and interact online. Who are we when we go online? How do others know we are there and how do they perceive us? Within the context of online learning, scholarly questions tend to reflect more specific concerns focused on how well people can learn in a setting limited to mediated interactions lacking various communication cues. For example, how can a teacher and students come to know each other if they cannot see each other? How can they effectively understand and communicate with each other if they are separated by space and, in many instances, time? These concerns are related to issues of social presence and identity, both of which are complex, multi-faceted, closely interrelated constructs
Luminosities of H alpha emitting regions in a pair of interacting galaxies in the Bootes void
Luminosities of H alpha emission from a pair of interacting galaxies in the low density environment of the Bootes void are presented. CG 692 (IRAS 1519+5050) has an H alpha luminosity of 2 x 10(exp 42) ergs s(exp -1), indicating a star formation rate of 18.4 solar mass yr(exp -1). Individual extranuclear H alpha regions have luminosities of approximately 10(exp 40) ergs s(exp -1). These luminosities are similar to those found for H II regions in bright, late-type galaxies in more densely populated parts of the Universe
Marketing, the past and corporate heritage
Argues for a more expansive conceptualisation of the pastâs relevance in, and for, marketing. Such a differentiated approach to the past is pregnant with possibilities in terms of advancing scholarship apropos temporal agency in marketing along with consumption practices. Symptomatic of this perspective is the increased mindfulness of the rich palate of past-related concepts. Significantly, the corporate heritage notion - because of its omni-temporal nature - represents a distinct and meaningful vector on the past by coalescing the past, present and future into a new type of temporality. As such, the authors reason this expansive conceptualisation of âthe past-in-marketingâ is both timely and efficacious. Whilst sensitive of the importance of the historical method in marketing and the history of marketing scholarship and practice per se. This broader marketing approach to and of the past highlights the ideational and material manifestations of the past-in-the-present and an envisaged past-in-the future
Optical Morphologies of Millijansky Radio Galaxies Observed by HST and in the VLA FIRST Survey
We report on a statistical study of the 51 radio galaxies at the millijansky
flux level from the Faint Images of the Radio Sky at Twenty centimeters,
including their optical morphologies and structure obtained with the Hubble
Space Telescope. Our optical imaging is significantly deeper (~2 mag) than
previous studies with the superior angular resolution of space-based imaging.
We that find 8/51 (16%) of the radio sources have no optically identifiable
counterpart to AB~24 mag. For the remaining 43 sources, only 25 are
sufficiently resolved in the HST images to reliably assign a visual
classification: 15 (60%) are elliptical galaxies, 2 (8%) are late-type spiral
galaxies, 1 (4%) is an S0, 3 (12%) are point-like objects (quasars), and 4
(16%) are merger systems. We find a similar distribution of optical types with
measurements of the Sersic index. The optical magnitude distribution of these
galaxies peaks at I~20.7+-0.5 AB mag, which is ~3 mag brighter than the depth
of our typical HST field and is thus not due to the WFPC2 detection limit. This
supports the luminosity-dependent density evolutionary model, where the
majority of faint radio galaxies typically have L*-optical luminosities and a
median redshift of z~0.8 with a relatively abrupt redshift cut-off at z>~2. We
discuss our results in the context of the evolution of elliptical galaxies and
active galactic nuclei.Comment: 20 pages, 8 figures, 51 galaxy images, and 5 tables. Uses
emulateapj.cls and natbib.sty. Accepted to ApJS. High resolution images are
available upon reques
A companion to a quasar at redshift 4.7
There is a growing consensus that the emergence of quasars at high redshifts
is related to the onset of galaxy formation, suggesting that the detection of
concentrations of gas accompanying such quasars should provide clues about the
early history of galaxies. Quasar companions have been recently identified at
redshifts up to . Here we report observations of Lyman-
emission (a tracer of ionised hydrogen) from the companion to a quasar at
=4.702, corresponding to a time when the Universe was less than ten per cent
of its present age. We argue that most of the emission arises in a gaseous
nebula that has been photoionised by the quasar, but an additional component of
continuum light -perhaps quasar light scattered from dust in the companion
body, or emission from young stars within the nebula- appears necessary to
explain the observations. These observations may be indicative of the first
stages in the assembly of galaxy-sized structures.Comment: 8 pages, 4 figures, plain LaTeX. Accepted for publication in Natur
Properties of Ly-alpha and Gamma Ray Burst selected starbursts at high redshifts
Selection of starbursts through either deep narrow band imaging of redshifted
Ly-alpha emitters, or localisation of host galaxies of gamma-ray bursts both
give access to starburst galaxies that are significantly fainter than what is
currently available from selection techniques based on the continuum (such as
Lyman-break selection). We here present results from a survey for Ly-alpha
emitters at z=3, conducted at the European Southern Observatory's Very Large
Telescope. Furthermore, we briefly describe the properties of host galaxies of
gamma-ray bursts at z>2. The majority of both Ly-alpha and gamma-ray burst
selected starbursts are fainter than the flux limit of the Lyman-break galaxy
sample, suggesting that a significant fraction of the integrated star formation
at z~3 is located in galaxies at the faint end of the luminosity function.Comment: invited talk, 6 pages, 3 figures, to appear in ``Starbursts from 30
Doradus to Lyman Break Galaxies'', eds. R. de Grijs, R. M. Gonzalez Delgado,
Astrophysics & Space Science Library Series, Kluwer (in press
The Nature of Compact Galaxies in the Hubble Deep Field (II): Spectroscopic Properties and Implications for the Evolution of the Star Formation Rate Density of the Universe
We present a spectroscopic study of 51 compact field galaxies with redshifts
z < 1.4 and apparent magnitudes I < 23.74 in the flanking fields of the Hubble
Deep Field. These galaxies are compact in the sense that they have small
apparent half-light radii (r_e < 0.5 arcsec) and high surface brightnesses
(SB_e < 22.2 mag arcsec^-2). The spectra, taken at the Keck telescope, show
emission lines in 88% of our sample, and only absorption lines in the remaining
12%. Emission-line profiles are roughly Gaussian with velocity widths that
range from the measurement limit of sigma = 35 km s^-1 to 150 km s^-1.
Rest-frame [OII]3727 equivalent widths range from 5A to 94A , yielding star
formation rates (SFR) of 0.1 to 14 M yr^-1. The analysis of various line
diagnostic diagrams reveals that 60% of compact emission-line galaxies have
velocity widths, excitations, Hbeta luminosities, SFRs, and mass-to-light
ratios characteristic of young star-forming HII galaxies. The remaining 40%
form a more heterogeneous class of evolved starbursts, similar to local
starburst disk galaxies. We find that, although the compact galaxies at z>0.7
have similar SFRs per unit mass to those at z<0.7, they are on average 10 times
more massive. Our sample implies a lower limit for the global comoving SFR
density of 0.004 M yr^-1 Mpc^-3 at z = 0.55, and 0.008 M yr^-1 Mpc^-3 at z =
0.85 (assuming Salpeter IMF, Ho = 50 km s^-1 Mpc^-1, and qo = 0.5). These
values, when compared to estimates for a sample of local compact galaxies
selected in a similar fashion, support a history of the universe in which the
SFR density declines by a factor 10 from z = 1 to today.Comment: LaTeX, 38 pages, 2 tables, 10 postscript figures. Accepted for
publication in the Astrophysical Journa
Registrar wellness in Botswana: Measuring burnout and identifying ways to improve wellness
Background. Burnout during registrar training is high, especially in resource-limited settings where stressors are intensified. Burnout leads to decreased quality of life for doctors, poor job and patient satisfaction, and difficulty retaining doctors.Objectives. Primary: to measure burnout among registrars working at Princess Marina Hospital in Gaborone, Botswana. Secondary: to determine factors contributing to burnout and identify potential wellness interventions.Methods. The validated Maslach Burnout Inventory was used to measure the degree of emotional exhaustion, depersonalisation and personal accomplishment. Work-related difficulties and potential wellness interventions were explored through multiple-choice and open-ended questions.Results. Of 40 eligible registrars, 20 (50%) completed the survey. High levels of burnout were reported for emotional exhaustion in 65% (13/20), depersonalisation in 45% (9/20), and personal accomplishment in 35% (7/20) of registrars. A high degree of burnout was reported by 75% (15/20) of registrars in one or more domains. In the previous 7 days, registrars worked an average of 77 hours, took 1.5 overnight calls, slept 5.7 hours per night, and 53% (10/19) had â„1 of their patients die. Five (25%) registrars considered leaving Botswana to work in another country, which correlated with those with the highest degree of burnout. The most common frustrations included insufficient salary and limited medical resources. Suggested interventions included improved mentorship and wellness lectures.Conclusions. There is a high degree of burnout, especially emotional exhaustion, among registrars. Encouragingly, most registrars have a desire to work in Botswana after training. Future research on improving registrar wellness in low-resource settings is urgently needed
Deep 1.1 mm-wavelength imaging of the GOODS-South field by AzTEC/ASTE -- II. Redshift distribution and nature of the submillimetre galaxy population
We report the results of the counterpart identification and a detailed
analysis of the physical properties of the 48 sources discovered in our deep
1.1mm wavelength imaging survey of the GOODS-South field using the AzTEC
instrument on the Atacama Submillimeter Telescope Experiment (ASTE). One or
more robust or tentative counterpart candidate is found for 27 and 14 AzTEC
sources, respectively, by employing deep radio continuum, Spitzer MIPS & IRAC,
and LABOCA 870 micron data. Five of the sources (10%) have two robust
counterparts each, supporting the idea that these galaxies are strongly
clustered and/or heavily confused. Photometric redshifts and star formation
rates (SFRs) are derived by analyzing UV-to-optical and IR-to-radio SEDs. The
median redshift of z~2.6 is similar to other earlier estimates, but we show
that 80% of the AzTEC-GOODS sources are at z>2, with a significant high
redshift tail (20% at z>3.3). Rest-frame UV and optical properties of AzTEC
sources are extremely diverse, spanning 10 magnitude in the i- and K-band
photometry with median values of i=25.3 and K=22.6 and a broad range of red
colour (i-K=0-6). These AzTEC sources are some of the most luminous galaxies in
the rest-frame optical bands at z>2, with inferred stellar masses of (1-30) x
10^{10} solar masses and UV-derived star formation rates of SFR(UV) > 10-1000
solar masses per year. The IR-derived SFR, 200-2000 solar masses per year, is
independent of redshift or stellar mass. The resulting specific star formation
rates, SSFR = 1-100 per Gyr, are 10-100 times higher than similar mass galaxies
at z=0, and they extend the previously observed rapid rise in the SSFR with
redshift to z=2-5. These galaxies have a SFR high enough to have built up their
entire stellar mass within their Hubble time. We find only marginal evidence
for an AGN contribution to the near-IR and mid-IR SEDs. (abridged)Comment: 31 pages including 14 figures, accepted for publication in the MNRAS.
A higher quality Figure 1 is also included as Figure1.jp
A Correlation Between Galaxy Morphology and MgII Halo Absorption Strength
(Abridged) We compared the quantified morphological properties of 37
intermediate redshift MgII absorption selected galaxies to the properties of
the absorbing halo gas, observed in the spectra of background quasars. The
galaxy morphologies were measured using GIM2D modeling of Hubble Space
Telescope WFPC-2 images and the absorbing gas properties were obtained from
HIRES/Keck and UVES/VLT quasar spectra. We found a 3.1 sigma correlation
between galaxy morphological asymmetries normalized by the quasar-galaxy
projected separations, A/D, and the MgII rest-frame equivalent widths.
Saturation effects cause increased scatter in the relationship with increasing
W_r(2796). We defined a subsample for which the fraction of saturated pixels in
the absorption profiles is f_sat<0.5. The correlation strengthened to 3.3
sigma. We also find a paucity of small morphological asymmetries for galaxies
selected by MgII absorption as compared to those of the general population of
field galaxies, as measured in the Medium Deep Survey. The K-S probability that
the two samples are drawn from the same galaxy population is ruled out at a
99.8% confidence level. The A/D-W_r(2796) correlation suggests a connection
between the processes that perturb galaxies and the quantity of gas in their
halos, normalized by the impact parameter. Since the perturbations are minor,
it is clear that dramatic processes or events are not required for a galaxy to
have an extended halo; the galaxies appear "normal". We suggest that common,
more mild processes that populate halos with gas, such as satellite galaxy
merging, accretion of the local cosmic web, and longer-range galaxy-galaxy
interactions, consequently also induce the observed minor perturbations in the
galaxies.Comment: Accepted for publication in the Astrophysical Journa
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