2,059 research outputs found
The Tully-Fisher relation of distant field galaxies
We examine the evolution of the Tully-Fisher relation (TFR) using a sample of
89 field spirals, with 0.1 < z < 1, for which we have measured confident
rotation velocities (Vrot). By plotting the residuals from the local TFR versus
redshift, or alternatively fitting the TFR to our data in several redshift
bins, we find evidence that luminous spiral galaxies are increasingly offset
from the local TFR with redshift, reaching a brightening of -1.0+-0.5 mag, for
a given Vrot, by approximately z = 1. Since selection effects would generally
increase the fraction of intrinsically-bright galaxies at higher redshifts, we
argue that the observed evolution is probably an upper limit.
Previous studies have used an observed correlation between the TFR residuals
and Vrot to argue that low mass galaxies have evolved significantly more than
those with higher mass. However, we demonstrate that such a correlation may
exist purely due to an intrinsic coupling between the Vrot scatter and TFR
residuals, acting in combination with the TFR scatter and restrictions on the
magnitude range of the data, and therefore it does not necessarily indicate a
physical difference in the evolution of galaxies with different Vrot.
Finally, if we interpret the luminosity evolution derived from the TFR as due
to the evolution of the star formation rate (SFR) in these luminous spiral
galaxies, we find that SFR(z) is proportional to (1+z)^(1.7+-1.1), slower than
commonly derived for the overall field galaxy population. This suggests that
the rapid evolution in the SFR density of the universe observed since
approximately z = 1 is not driven by the evolution of the SFR in individual
bright spiral galaxies. (Abridged.)Comment: 14 pages, 10 figures, accepted by MNRA
MegaMorph: classifying galaxy morphology using multi-wavelength S\'ersic profile fits
Aims. This work investigates the potential of using the wavelength-dependence
of galaxy structural parameters (S\'ersic index, n, and effective radius, Re)
to separate galaxies into distinct types. Methods. A sample of nearby galaxies
with reliable visual morphologies is considered, for which we measure
structural parameters by fitting multi-wavelength single-S\'ersic models.
Additionally, we use a set of artificially redshifted galaxies to test how
these classifiers behave when the signal-to-noise decreases. Results. We show
that the wavelength-dependence of n may be employed to separate
visually-classified early- and late-type galaxies, in a manner similar to the
use of colour and n. Furthermore, we find that the wavelength variation of n
can recover galaxies that are misclassified by these other morphological
proxies. Roughly half of the spiral galaxies that contaminate an early-type
sample selected using (u-r) versus n can be correctly identified as late-types
by N, the ratio of n measured in two different bands. Using a set of
artificially-redshifted images, we show that this technique remains effective
up to z ~ 0.1. N can therefore be used to achieve purer samples of early-types
and more complete samples of late-types than using a colour-n cut alone. We
also study the suitability of R, the ratio of Re in two different bands, as a
morphological classifier, but find that the average sizes of both early- and
late-type galaxies do not change substantially over optical wavelengths.Comment: 6 pages, 2 figures, 2 tables, Accepted for publication in A&
Evolution of field spiral galaxies up to redshifts z=1
We have gained VLT/FORS spectra and HST/ACS images of a sample of 220 distant
field spiral galaxies. Spatially resolved rotation curves were extracted and
fitted with synthetic velocity fields that take into account all geometric and
observational effects, like blurring due to the slit width and seeing
influence. The maximum rotation velocity Vmax could be determined for 124
galaxies that cover the redshift range 0.1<z<1.0. The luminosity-rotation
velocity distribution of this sample is offset from the Tully-Fisher relation
(TFR) of local low-mass spirals, whereas the distant high-mass spirals are
compatible with the local TFR. We show that the slope of the local and the
intermediate-z TFR would be in compliance if its scatter decreased by more than
a factor of 3 between z~0.5 and z~0. On the other hand, the distant
low-luminosity disks have much lower stellar M/L ratios than their local
counterparts, while high-luminosity disks barely evolved in M/L over the
covered redshift range. This could be the manifestation of the "downsizing"
effect, i.e. the succesive shift of the peak of star formation from high-mass
to low-mass galaxies towards lower redshifts. This trend might be canceled out
in the TF diagram due to the simultaneous evolution of multiple parameters. We
also estimate the ratios between stellar and total masses, finding that these
remained constant since z=1, as would be expected in the context of
hierarchically growing structure. (Abridged)Comment: 20 pages, 5 figures, ApJ, accepte
Presentation of a Peri-prosthetic Atypical Femur Fracture After Long Term Anti-Resorptive Medication Use
Peri-prosthetic atypical femur fractures are rare. Most are associated with the use of long-term bisphosphonates and other anti-resorptive medications. This case highlights a 74-year-old female treated with approximately 13 years of bisphosphonate therapy followed by a short course of denosumab, who suffered an atraumatic peri-prosthetic fracture after a several month prodrome. This case report\u27s objectives are to show how the prodrome presents, increase recognition of the condition and work up prior to fracture, and emphasize the need to consider drug holidays
Star formation rates and chemical abundances of emission line galaxies in intermediate-redshift clusters
We examine the evolutionary status of luminous, star-forming galaxies in
intermediate-redshift clusters by considering their star formation rates and
the chemical and ionsiation properties of their interstellar emitting gas. Our
sample consists of 17 massive, star-forming, mostly disk galaxies with
M_{B}<-20, in clusters with redshifts in the range 0.31< z <0.59, with a median
of =0.42. We compare these galaxies with the identically selected and
analysed intermediate-redshift field sample of Mouhcine et al. (2006), and with
local galaxies from the Nearby Field Galaxy Survey of Jansen et al. (2000).
From our optical spectra we measure the equivalent widths of OII, Hbeta and
OIII emission lines to determine diagnostic line ratios, oxygen abundances, and
extinction-corrected star formation rates. The star-forming galaxies in
intermediate-redshift clusters display emission line equivalent widths which
are, on average, significantly smaller than measured for field galaxies at
comparable redshifts. However, a contrasting fraction of our cluster galaxies
have equivalent widths similar to the highest observed in the field. This
tentatively suggests a bimodality in the star-formation rates per unit
luminosity for galaxies in distant clusters. We find no evidence for further
bimodalities, or differences between our cluster and field samples, when
examining additional diagnostics and the oxygen abundances of our galaxies.
This maybe because no such differences exist, perhaps because the cluster
galaxies which still display signs of star-formation have recently arrived from
the field. In order to examine this topic with more certainty, and to further
investigate the way in which any disparity varies as a function of cluster
properties, larger spectroscopic samples are needed.Comment: 10 pages, 6 figures, MNRAS in pres
How well does Anorexia Nervosa fit with personal values? An exploratory study.
BACKGROUND: Despite an increasing clinical interest in the use of personal values as a motivational tool in psychological therapies for Anorexia Nervosa (AN), research is limited. This study explored personal values among individuals with AN, with a particular focus on the 'fit' between participants' values and their AN. METHODS: A qualitative research design was employed in this study. In-depth, semi-structured interviews were carried out among eight female outpatients and inpatients with a diagnosis of AN or Eating Disorder Not Otherwise Specified - AN type (EDNOS-AN type). Data was analysed using Interpretative Phenomenological Analysis (IPA; Smith, Jarman & Osborne, 1999). RESULTS: Three super-ordinate themes emerged from analysis: 'Balancing Values' (difficulty finding balance in relating to and acting on values), 'Congruence and Clashes between AN and Values' (experiences of AN representing a mixed-fit with values) and 'From Ambivalence to Motivation' (ambivalence toward both AN and recovery - in the context of its mixed-fit with values - and experiences of values as a motivational tool in recovery). CONCLUSIONS: Study findings support a role for psychological therapies in working with personal values as a means of promoting recovery in AN, through supporting individuals to explore AN's workability in the context of their values. Further research investigating the optimal stage of treatment to work with values as a motivational tool is warranted
Fossil wood of Cretaceous age from the Namaqualand continental shelf, South Africa
Fossil wood was collected from sediments on the Namaqualand shelf, West Coast, South Africa, between the Orange River mouth and just to the south of Kleinzee. Forty three of these samples are here described. All the woods are gymnospermous and have abietinian tracheid pitting. Nineteen of them are well enough preserved to be identified to species level: Podocarpoxylon cf. umzambense, Mesembrioxylon cf. stokesii, M. cf. sahnii, M. cf. woburnense and Protocupressinoxylon cf. purbeckensis. The remainder of the woods have been placed in the artificial genus Mesembrioxylon without species names. The woods are probably primitive members of the Podocarpaceae growing during the Lower Cretaceous. They indicate a seasonal climate and inhabited the extensive low-lying coastal regions.De Beer
More fossil wood from the Namaqualand coast, South Africa; onshore material.
Main articleFossil wood was collected from a palaeo-beach sequence on the farms Sandkop, Oubeep and
adjacent State land, on the Namaqualand (west) coast of South Africa. Of the 14 samples sectioned
only 5 were well enough preserved to describe and identify to species level. The woods are
podocarpaceous and have been assigned to the taxa Podocarpoxylon cf. umzambense,
Mesembrioxylon woburnense, M. stokesi and Mesembrioxylon sp. The samples are Lower
Cretaceous in age and were most probably reworked a number of times into successively younger
palaeoshoreline deposits. The same species occurred in the offshore sediments, therefore
indicating a wider area of "woodland" and further evidence of extensive shelf erosion by
subsequent marine transgressions and regressions.Non
The Tully-Fisher relation of intermediate redshift field and cluster galaxies from Subaru spectroscopy
We have carried out spectroscopic observations in 4 cluster fields using
Subaru's FOCAS multi-slit spectrograph and obtained spectra for 103 bright disk
field and cluster galaxies at . Seventy-seven of these
show emission lines, and 33 provide reasonably-secure determinations of the
galaxies' rotation velocity. The rotation velocities, luminosities, colours and
emission-line properties of these galaxies are used to study the possible
effects of the cluster environment on the star-formation history of the
galaxies. Comparing the Tully-Fisher relations of cluster and field galaxies at
similar reshifts we find no measurable difference in rest-frame -band
luminosity at a given rotation velocity (the formal difference is mag). The colours of the cluster emission line galaxies are only marginally
redder in rest-frame (by mag) than the field galaxies in
our sample. Taken at face value, these results seem to indicate that bright
star-forming cluster spirals are similar to their field counterparts in their
star-formation properties. However, we find that the fraction of disk galaxies
with absorption-line spectra (i.e., with no current star formation) is larger
in clusters than in the field by a factor of --5. This suggests that the
cluster environment has the overall effect of switching off star formation in
(at least) some spiral galaxies. To interpret these observational results, we
carry out simulations of the possible effects of the cluster environment on the
star-formation history of disk galaxies and thus their photometric and
spectroscopic properties. Finally, we evaluate the evolution of the rest-frame
absolute -band magnitude per unit redshift at fixed rotation velocity.Comment: 21 pages, 13 figures, accepted for publication in MNRA
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