1,673 research outputs found
Distant radio galaxies in the near IR
We are carrying out a program of near IR imaging and spectroscopy of radio galaxies with redshifts of 1.5 and greater. One of its principal goals is to constrain the ages and star formation histories of massive galaxies at early epochs. The radio galaxies are drawn from the survey of 1Jy class sources by McCarthy et al (1989) and McCarthy (1990). The sample contains 18 radio galaxies with redshifts greater than 2 and an additional 10 objects with 1.5 less than z less than 2.0. The redshifts were obtained from long slit spectra with the CTIO 4 m. While the galaxies are quite faint (r approximately = 21-24.5) all have Lyman alpha emission with rest frame equivalent widths of 100 - 1000 A. Multicolor photometry in the g,r,i and J,H,K bands has been obtained with the 2.5-m Du Pont Telescope on Las Campanas and with the Hale 5 m telescope at Palomar. We have recently obtained near IR spectra, using the 4 m telescopes at KPNO and CTIO, of a few objects with the goal of determining the Lyman alpha/H-alpha ratio and hence the reddening
What drives the translocation of stiff chains?
We study the dynamics of the passage of a stiff chain through a pore into a
cell containing particles that bind reversibly to it. Using Brownian Molecular
Dynamics simulations we investigate the mean-first-passage time as a function
of the length of the chain inside, for different concentrations of binding
particles. As a consequence of the interactions with these particles, the chain
experiences a net force along its length whose calculated value from the
simulations accounts for the velocity at which it enters the cell. This force
can in turn be obtained from the solution of a generalized diffusion equation
incorporating an effective Langmuir adsorption free energy for the chain plus
binding particles. These results suggest a role of binding particles in the
translocation process which is in general quite different from that of a
Brownian ratchet. Furthermore, non-equilibrium effects contribute significantly
to the dynamics, \emph{e.g.}, the chain often enters the cell faster than
particle binding can be saturated, resulting in a force several times smaller
than the equilibrium value.Comment: 7 pages, 4 figure
Coupled surface plasmons and optical guided wave exploration of near-surface director profile
Copyright © 2007 IOP Publishing Ltd and Deutsche Physikalische Gesellschaft. This is the published version of an article published in New Journal of Physics Vol. 9, article 49. DOI: 10.1088/1367-2630/9/3/049For a liquid crystal (LC) cell with thin silver claddings it is possible, using a high index coupling prism, to excite both surface plasmon modes and ordinary optical guided modes. In a situation where the tilt of the director varies from homogeneous to homeotropic through the cell, then for p-polarized incident radiation the p-polarized surface plasmon mode and the ordinary guided waves may couple to each other. When the plane containing the director is normal to the incident plane, there is also polarization conversion leading to strong coupling between the p-polarized surface plasmon and s-like guided modes. From theoretical analyses together with numerical modelling it is shown how this coupling between the surface plasmon mode and guided waves gives a high sensitivity to the surface director tilt profile near the walls, higher than that of the surface plasmon mode alone. Experimental confirmation of this has been realized using a hybrid aligned nematic (HAN) LC cell with the director in a plane normal to the incident plane. The results fully confirm the model predictions showing that this coupling of surface plasmons to guided waves provides a powerful tool for near-surface director studies
Molecular Hydrogen and Paschen-alpha Emission in Cooling Flow Galaxies
We present near-infrared spectra obtained to search for Pa-alpha and
molecular hydrogen lines in edge-darkened (FR I-type) radio galaxies with
bright Halpha emission in the redshift range 0.0535<z<0.15. We find that all
three galaxies in our sample (PKS 0745-191, PKS 1346+26, & PKS2322-12) which
are associated with strong cooling flows also have strong Pa-alpha and H_2
(1-0) S(1) through S(5) emission, while other radio galaxies do not. Together
with earlier observations this confirms claims that cooling flow galaxies are
copious emitters of molecular hydrogen with large H_2 (1-0) S(3)/Pa-alpha
ratios in the range 0.5 to 2. The emission is centrally concentrated within the
inner few kiloparsec and could come from warm (T ~ 1000-1500 K) molecular
material which is being deposited by the cooling flow. We speculate that the
H_2 emission could be related to the interaction between the jets and this
molecular gas.Comment: ApJ Letters, in press, AAS LaTex, preprint also available at
http://www.astro.umd.edu/~hfalcke/publications.html#nirga
The Unusual Infrared Object HDF-N J123656.3+621322
We describe an object in the Hubble Deep Field North with very unusual
near-infrared properties. It is readily visible in Hubble Space Telescope
NICMOS images at 1.6um and from the ground at 2.2um, but is undetected (with
signal-to-noise <~ 2) in very deep WFPC2 and NICMOS data from 0.3 to 1.1um. The
f_nu flux density drops by a factor >~ 8.3 (97.7% confidence) from 1.6 to
1.1um. The object is compact but may be slightly resolved in the NICMOS 1.6um
image. In a low-resolution, near-infrared spectrogram, we find a possible
emission line at 1.643um, but a reobservation at higher spectral resolution
failed to confirm the line, leaving its reality in doubt. We consider various
hypotheses for the nature of this object. Its colors are unlike those of known
galactic stars, except perhaps the most extreme carbon stars or Mira variables
with thick circumstellar dust shells. It does not appear to be possible to
explain its spectral energy distribution as that of a normal galaxy at any
redshift without additional opacity from either dust or intergalactic neutral
hydrogen. The colors can be matched by those of a dusty galaxy at z >~ 2, by a
maximally old elliptical galaxy at z >~ 3 (perhaps with some additional
reddening), or by an object at z >~ 10 whose optical and 1.1um light have been
suppressed by the intergalactic medium. Under the latter hypothesis, if the
luminosity results from stars and not an AGN, the object would resemble a
classical, unobscured protogalaxy, with a star formation rate >~ 100 M_sun/yr.
Such UV-bright objects are evidently rare at 2 < z < 12.5, however, with a
space density several hundred times lower than that of present-day L* galaxies.Comment: Accepted for publication in the Astrophysical Journal. 27 pages,
LaTeX, with 7 figures (8 files); citations & references updated + minor
format change
Color Gradients and Surface Brightness Profiles of Galaxies in the Hubble Deep Field-North
We fit elliptical isophotes to the Hubble Deep Field-North WFPC-2 and NICMOS
data to study the rest-frame UV_{218}-U_{300} color profiles and rest-frame B
surface brightness profiles of 33 intermediate redshift galaxies (0.5 <= z <=
1.2) with I_{814} < 25 and 50 high redshift galaxies (2.0 <= z <= 3.5) with
H_{160}< 27. From the weighted least-squares fit to the color profiles we find
that, at intermediate redshifts, the galaxies possess negative color gradients
indicating a reddening towards the center of the profile similar to local
samples whereas, at high redshifts, the galaxies possess positive color
gradients. This indicates that star formation is more centrally concentrated in
the distant galaxy sample which differs from the prevalent mode of extended
disk star formation that we observe in the local universe. Additionally, we
find that it is critical to correct for PSF effects when evaluating the surface
brightness profiles since at small scale lengths and faint magnitudes, an
r^{1/4} profile can be smoothed out substantially to become consistent with an
exponential profile. After correcting for PSF effects, we find that at higher
look-back time, the fraction of galaxies possessing exponential profiles have
slightly decreased while the fraction of galaxies possessing r^{1/4} profiles
have slightly increased. Our results also suggest a statistically insignificant
increase in the fraction of peculiar/irregular type galaxies. We compare our
results with recent semi-analytical models which treat galaxy formation and
evolution following the cold dark matter hierarchical framework.Comment: 31 pages, 10 JPEG figures. To be published in AJ Vol. 124, October
200
Integrating the voluntary sector in personalised care: mixed methods study of the outcomes from wellbeing co-ordination for adults with complex needs
PurposeThis integrated care study seeks to highlight how voluntary sector “wellbeing co-ordinators” co-located in a horizontally and vertically integrated, multidisciplinary community hub within one locality of an Integrated Care Organisation contribute to complex, person-centred, co-ordinated care.Design/methodology/approachThis is a naturalistic, mixed method and mixed data study. It is complementing a before-and-after study with a sub-group analysis of people receiving input from the wider hub (including Wellbeing Co-ordination and Enhanced Intermediate Care), qualitative case studies, interviews, and observations co-produced with embedded researchers-in-residence.FindingsThe cross-case analysis uses trajectories and outcome patterns across six client groups to illustrate the bio-psycho-social complexity of each group across the life course, corresponding with the range of inputs offered by the hub.Research limitations/implicationsTo consider the effectiveness and mechanisms of complex system-wide interventions operating at horizontal and vertical interfaces and researching this applying co-produced, embedded, naturalistic and mixed methods approaches.Practical implicationsHow a bio-psycho-social approach by a wellbeing co-ordinator can contribute to improved person reported outcomes from a range of preventive, rehabilitation, palliative care and bereavement services in the community.Social implicationsTo combine knowledge about individuals held in the community to align the respective inputs, and expectations about outcomes while considering networked pathways based on functional status, above diagnostic pathways, and along a life-continuum.Originality/valueThe hub as a whole seems to (1) Enhance engagement through relationship, trust and activation, (2) Exchanging knowledge to co-create a shared bio-psycho-social understanding of each individual’s situation and goals, (3) Personalising care planning by utilising the range of available resources to ensure needs are met, and (4) Enhancing co-ordination and ongoing care through multi-disciplinary working between practitioners, across teams and sectors.</jats:sec
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