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CANDELS Observations Of The Structural Properties Of Cluster Galaxies At Z=1.62
We discuss the structural and morphological properties of galaxies in a z = 1.62 proto-cluster using near-IR imaging data from Hubble Space Telescope Wide Field Camera 3 data of the Cosmic Assembly Near-IR Deep Extragalactic Legacy Survey (CANDELS). The cluster galaxies exhibit a clear color-morphology relation: galaxies with colors of quiescent stellar populations generally have morphologies consistent with spheroids, and galaxies with colors consistent with ongoing star formation have disk-like and irregular morphologies. The size distribution of the quiescent cluster galaxies shows a deficit of compact (less than or similar to 1 kpc), massive galaxies compared to CANDELS field galaxies at z = 1.6. As a result, the cluster quiescent galaxies have larger average effective sizes compared to field galaxies at fixed mass at greater than 90% significance. Combined with data from the literature, the size evolution of quiescent cluster galaxies is relatively slow from z similar or equal to 1.6 to the present, growing as (1 + z)(-0.6 +/- 0.1). If this result is generalizable, then it implies that physical processes associated with the denser cluster region seem to have caused accelerated size growth in quiescent galaxies prior to z = 1.6 and slower subsequent growth at z < 1.6 compared to galaxies in the lower density field. The quiescent cluster galaxies at z = 1.6 have higher ellipticities compared to lower redshift samples at fixed mass, and their surface-brightness profiles suggest that they contain extended stellar disks. We argue that the cluster galaxies require dissipationless (i.e., gas-poor or "dry") mergers to reorganize the disk material and to match the relations for ellipticity, stellar mass, size, and color of early-type galaxies in z < 1 clusters.NASA NAS5-26555HST GO-12060NASA through from the Space Telescope Science Institute GO-12060European Research CouncilRoyal SocietyTexas AM UniversityGeorge P. and Cynthia Woods Institute for Fundamental Physics and AstronomyAstronom
CANDELS Observations of the Environmental Dependence of the Color-Mass-Morphology Relation at z = 1.6
We study the environmental dependence of color, stellar mass, and morphology
by comparing galaxies in a forming cluster to those in the field at z = 1:6
with Hubble Space Telescope near-infrared imaging in the CANDELS/UDS field. We
quantify the morphology of the galaxies using the effective radius, reff, and
S\'ersic index, n. In both the cluster and field, approximately half of the
bulge-dominated galaxies (n > 2) reside on the red sequence of the
color-magnitude diagram, and most disk-dominated galaxies (n < 2) have colors
expected for star-forming galaxies. There is weak evidence that cluster
galaxies have redder rest-frame U - B colors and higher stellar masses compared
to the field. Star-forming galaxies in both the cluster and field show no
significant differences in their morphologies. In contrast, there is evidence
that quiescent galaxies in the cluster have larger median effective radii and
smaller S\'ersic indices compared to the field with a significance of 2?. These
differences are most pronounced for galaxies at clustercentric distances 1 Mpc
< Rproj < 1.5 Mpc, which have low S\'ersic indices and possibly larger
effective radii, more consistent with star-forming galaxies at this epoch and
in contrast to other quiescent galaxies. We argue that star-forming galaxies
are processed under the influence of the cluster environment at distances
greater than the cluster-halo virial radius. Our results are consistent with
models where gas accretion onto these galaxies is suppressed from processes
associated with the cluster environment.Comment: ApJ accepted, 19 pages, 10 figure
Fostering creativity with wisdom
This is a postprint of an article whose final and definitive form has been published in the Cambridge Journal of Education© 2006 Copyright University of Cambridge, Faculty of Education; Cambridge Journal of Education is available online at http://www.informaworld.comOver the past five years, creativity has become a focus of attention for policy-makers in education. However, the increased interest in creativity has occurred as if without reference to any value framework. This article suggests that in fact an invisible underpinning value framework has been provided by western individualism, in turn both supporting and driven by the globalized capitalist marketplace. What could this mean for nurturing creativity with wisdom in schools? Working from the stance that wisdom involves making thoughtful, well-informed and appropriate judgments leading to sound courses of action with regard to the consequences, this paper discusses some significant objections to a market-driven model of creativity in education, discusses a possible framework for understanding creativity in a way which emphasizes responsibility as well as rights to expression and proposes wisdom as a necessary element of pedagogy
Mesoscopic organization reveals the constraints governing C. elegans nervous system
One of the biggest challenges in biology is to understand how activity at the
cellular level of neurons, as a result of their mutual interactions, leads to
the observed behavior of an organism responding to a variety of environmental
stimuli. Investigating the intermediate or mesoscopic level of organization in
the nervous system is a vital step towards understanding how the integration of
micro-level dynamics results in macro-level functioning. In this paper, we have
considered the somatic nervous system of the nematode Caenorhabditis elegans,
for which the entire neuronal connectivity diagram is known. We focus on the
organization of the system into modules, i.e., neuronal groups having
relatively higher connection density compared to that of the overall network.
We show that this mesoscopic feature cannot be explained exclusively in terms
of considerations, such as optimizing for resource constraints (viz., total
wiring cost) and communication efficiency (i.e., network path length).
Comparison with other complex networks designed for efficient transport (of
signals or resources) implies that neuronal networks form a distinct class.
This suggests that the principal function of the network, viz., processing of
sensory information resulting in appropriate motor response, may be playing a
vital role in determining the connection topology. Using modular spectral
analysis, we make explicit the intimate relation between function and structure
in the nervous system. This is further brought out by identifying functionally
critical neurons purely on the basis of patterns of intra- and inter-modular
connections. Our study reveals how the design of the nervous system reflects
several constraints, including its key functional role as a processor of
information.Comment: Published version, Minor modifications, 16 pages, 9 figure
The Seventh Data Release of the Sloan Digital Sky Survey
This paper describes the Seventh Data Release of the Sloan Digital Sky Survey
(SDSS), marking the completion of the original goals of the SDSS and the end of
the phase known as SDSS-II. It includes 11663 deg^2 of imaging data, with most
of the roughly 2000 deg^2 increment over the previous data release lying in
regions of low Galactic latitude. The catalog contains five-band photometry for
357 million distinct objects. The survey also includes repeat photometry over
250 deg^2 along the Celestial Equator in the Southern Galactic Cap. A
coaddition of these data goes roughly two magnitudes fainter than the main
survey. The spectroscopy is now complete over a contiguous area of 7500 deg^2
in the Northern Galactic Cap, closing the gap that was present in previous data
releases. There are over 1.6 million spectra in total, including 930,000
galaxies, 120,000 quasars, and 460,000 stars. The data release includes
improved stellar photometry at low Galactic latitude. The astrometry has all
been recalibrated with the second version of the USNO CCD Astrograph Catalog
(UCAC-2), reducing the rms statistical errors at the bright end to 45
milli-arcseconds per coordinate. A systematic error in bright galaxy photometr
is less severe than previously reported for the majority of galaxies. Finally,
we describe a series of improvements to the spectroscopic reductions, including
better flat-fielding and improved wavelength calibration at the blue end,
better processing of objects with extremely strong narrow emission lines, and
an improved determination of stellar metallicities. (Abridged)Comment: 20 pages, 10 embedded figures. Accepted to ApJS after minor
correction
Non-Stationarity in the “Resting Brain’s” Modular Architecture
Task-free functional magnetic resonance imaging (TF-fMRI) has great potential for advancing the understanding and treatment of neurologic illness. However, as with all measures of neural activity, variability is a hallmark of intrinsic connectivity networks (ICNs) identified by TF-fMRI. This variability has hampered efforts to define a robust metric of connectivity suitable as a biomarker for neurologic illness. We hypothesized that some of this variability rather than representing noise in the measurement process, is related to a fundamental feature of connectivity within ICNs, which is their non-stationary nature. To test this hypothesis, we used a large (n = 892) population-based sample of older subjects to construct a well characterized atlas of 68 functional regions, which were categorized based on independent component analysis network of origin, anatomical locations, and a functional meta-analysis. These regions were then used to construct dynamic graphical representations of brain connectivity within a sliding time window for each subject. This allowed us to demonstrate the non-stationary nature of the brain’s modular organization and assign each region to a “meta-modular” group. Using this grouping, we then compared dwell time in strong sub-network configurations of the default mode network (DMN) between 28 subjects with Alzheimer’s dementia and 56 cognitively normal elderly subjects matched 1∶2 on age, gender, and education. We found that differences in connectivity we and others have previously observed in Alzheimer’s disease can be explained by differences in dwell time in DMN sub-network configurations, rather than steady state connectivity magnitude. DMN dwell time in specific modular configurations may also underlie the TF-fMRI findings that have been described in mild cognitive impairment and cognitively normal subjects who are at risk for Alzheimer’s dementia
TLR7 gain-of-function genetic variation causes human lupus
Although circumstantial evidence supports enhanced Toll-like receptor 7 (TLR7) signalling as a mechanism of human systemic autoimmune disease evidence of lupus-causing TLR7 gene variants is lacking. Here we describe human systemic lupus erythematosus caused by a TLR7 gain-of-function variant. TLR7 is a sensor of viral RNA and binds to guanosine. We identified a de novo, previously undescribed missense TLR7Y264H variant in a child with severe lupus and additional variants in other patients with lupus. The TLR7Y264H variant selectively increased sensing of guanosine and 2',3'-cGMP1 and was sufficient to cause lupus when introduced into mice. We show that enhanced TLR7 signalling drives aberrant survival of B cell receptor (BCR)-activated B cells, and in a cell-intrinsic manner, accumulation of CD11c+ age-associated B cells and germinal centre B cells. Follicular and extrafollicular helper T cells were also increased but these phenotypes were cell-extrinsic. Deficiency of MyD88 (an adaptor protein downstream of TLR7) rescued autoimmunity, aberrant B cell survival, and all cellular and serological phenotypes. Despite prominent spontaneous germinal-centre formation in Tlr7Y264H mice, autoimmunity was not ameliorated by germinal-centre deficiency, suggesting an extrafollicular origin of pathogenic B cells. We establish the importance of TLR7 and guanosine-containing self-ligands for human lupus pathogenesis, which paves the way for therapeutic TLR7 or MyD88 inhibition
Resting-State Multi-Spectrum Functional Connectivity Networks for Identification of MCI Patients
In this paper, a high-dimensional pattern classification framework, based on functional associations between brain regions during resting-state, is proposed to accurately identify MCI individuals from subjects who experience normal aging. The proposed technique employs multi-spectrum networks to characterize the complex yet subtle blood oxygenation level dependent (BOLD) signal changes caused by pathological attacks. The utilization of multi-spectrum networks in identifying MCI individuals is motivated by the inherent frequency-specific properties of BOLD spectrum. It is believed that frequency specific information extracted from different spectra may delineate the complex yet subtle variations of BOLD signals more effectively. In the proposed technique, regional mean time series of each region-of-interest (ROI) is band-pass filtered ( Hz) before it is decomposed into five frequency sub-bands. Five connectivity networks are constructed, one from each frequency sub-band. Clustering coefficient of each ROI in relation to the other ROIs are extracted as features for classification. Classification accuracy was evaluated via leave-one-out cross-validation to ensure generalization of performance. The classification accuracy obtained by this approach is 86.5%, which is an increase of at least 18.9% from the conventional full-spectrum methods. A cross-validation estimation of the generalization performance shows an area of 0.863 under the receiver operating characteristic (ROC) curve, indicating good diagnostic power. It was also found that, based on the selected features, portions of the prefrontal cortex, orbitofrontal cortex, temporal lobe, and parietal lobe regions provided the most discriminant information for classification, in line with results reported in previous studies. Analysis on individual frequency sub-bands demonstrated that different sub-bands contribute differently to classification, providing extra evidence regarding frequency-specific distribution of BOLD signals. Our MCI classification framework, which allows accurate early detection of functional brain abnormalities, makes an important positive contribution to the treatment management of potential AD patients
Cosmological Constraints from the SDSS Luminous Red Galaxies
We measure the large-scale real-space power spectrum P(k) using luminous red
galaxies (LRGs) in the Sloan Digital Sky Survey (SDSS) and use this measurement
to sharpen constraints on cosmological parameters from the Wilkinson Microwave
Anisotropy Probe (WMAP). We employ a matrix-based power spectrum estimation
method using Pseudo-Karhunen-Loeve eigenmodes, producing uncorrelated
minimum-variance measurements in 20 k-bands of both the clustering power and
its anisotropy due to redshift-space distortions, with narrow and well-behaved
window functions in the range 0.01h/Mpc < k < 0.2h/Mpc. Results from the LRG
and main galaxy samples are consistent, with the former providing higher
signal-to-noise. Our results are robust to omitting angular and radial density
fluctuations and are consistent between different parts of the sky. They
provide a striking confirmation of the predicted large-scale LCDM power
spectrum.
Combining only SDSS LRG and WMAP data places robust constraints on many
cosmological parameters that complement prior analyses of multiple data sets.
The LRGs provide independent cross-checks on Om and the baryon fraction in good
agreement with WMAP. Within the context of flat LCDM models, our LRG
measurements complement WMAP by sharpening the constraints on the matter
density, the neutrino density and the tensor amplitude by about a factor of
two, giving Omega_m=0.24+-0.02 (1 sigma), sum m_nu < 0.9 eV (95%) and r<0.3
(95%). Baryon oscillations are clearly detected and provide a robust
measurement of the comoving distance to the median survey redshift z=0.35
independent of curvature and dark energy properties. Within the LCDM framework,
our power spectrum measurement improves the evidence for spatial flatness,
sharpening the curvature constraint Omega_tot=1.05+-0.05 from WMAP alone to
Omega_tot=1.003+-0.010. Assuming Omega_tot=1, the equation of state parameter
is constrained to w=-0.94+-0.09, indicating the potential for more ambitious
future LRG measurements to provide precision tests of the nature of dark
energy. All these constraints are essentially independent of scales k>0.1h/Mpc
and associated nonlinear complications, yet agree well with more aggressive
published analyses where nonlinear modeling is crucial.Comment: Matches accepted PRD version. SDSS data, likelihood code, Markov
chains and ppt figures available at
http://space.mit.edu/home/tegmark/sdss.html 36 journal pages, 25 figs.
CosmoMC plugin at http://cosmologist.info/cosmomc
CANDELS: THE EVOLUTION OF GALAXY REST-FRAME ULTRAVIOLET COLORS FROM z = 8 TO 4
We study the evolution of galaxy rest-frame ultraviolet (UV) colors in the
epoch 4 < z < 8. We use new wide-field near-infrared data in GOODS-S from the
CANDELS, HUDF09 and ERS programs to select galaxies via photometric redshift
measurements. Our sample consists of 2812 candidate galaxies at z > 3.5,
including 113 at z = 7 to 8. We fit the observed spectral energy distribution
to a suite of synthetic stellar population models, and measure the value of the
UV spectral slope (beta) from the best-fit model spectrum. The median value of
beta evolves significantly from -1.82 (+0.00,-0.04) at z = 4, to -2.37
(+0.26,-0.06) at z = 7. Additionally, we find that faint galaxies at z = 7 have
beta = -2.68 (+0.39,-0.24) (~ -2.4 after correcting for observational bias);
this is redder than previous claims in the literature, and does not require
"exotic" stellar populations to explain their colors. This evolution can be
explained by an increase in dust extinction, with the timescale consistent with
low-mass AGB stars forming the bulk of the dust. We find no significant (<
2-sigma) correlation between beta and M_UV when measuring M_UV at a consistent
rest-frame wavelength of 1500 A. This is particularly true at bright
magnitudes, though our results do show evidence for a weak correlation at faint
magnitudes when galaxies in the HUDF are considered separately, hinting that
dynamic range in sample luminosities may play a role. We do find a strong
correlation between beta and the stellar mass at all redshifts, in that more
massive galaxies exhibit redder colors. The most massive galaxies in our sample
have red colors at each redshift, implying that dust can build up quickly in
massive galaxies, and that feedback is likely removing dust from low-mass
galaxies at z > 7. Thus the stellar-mass - metallicity relation, previously
observed up to z ~ 3, may extend out to z = 7 - 8.Comment: Accepted to the Astrophysical Journal. 19 pages, 8 figures and 5
tables. The complete data for Table 3 will be available in the online version
of the Astrophysical Journal, and a version is included in the source files
for this submissio
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