60 research outputs found
A Vast Thin Plane of Co-rotating Dwarf Galaxies Orbiting the Andromeda Galaxy
Dwarf satellite galaxies are thought to be the remnants of the population of
primordial structures that coalesced to form giant galaxies like the Milky Way.
An early analysis noted that dwarf galaxies may not be isotropically
distributed around our Galaxy, as several are correlated with streams of HI
emission, and possibly form co-planar groups. These suspicions are supported by
recent analyses, and it has been claimed that the apparently planar
distribution of satellites is not predicted within standard cosmology, and
cannot simply represent a memory of past coherent accretion. However, other
studies dispute this conclusion. Here we report the existence (99.998%
significance) of a planar sub-group of satellites in the Andromeda galaxy,
comprising approximately 50% of the population. The structure is vast: at least
400 kpc in diameter, but also extremely thin, with a perpendicular scatter
<14.1 kpc (99% confidence). Radial velocity measurements reveal that the
satellites in this structure have the same sense of rotation about their host.
This finding shows conclusively that substantial numbers of dwarf satellite
galaxies share the same dynamical orbital properties and direction of angular
momentum, a new insight for our understanding of the origin of these most dark
matter dominated of galaxies. Intriguingly, the plane we identify is
approximately aligned with the pole of the Milky Way's disk and is co-planar
with the Milky Way to Andromeda position vector. The existence of such
extensive coherent kinematic structures within the halos of massive galaxies is
a fact that must be explained within the framework of galaxy formation and
cosmology.Comment: Published in the 3rd Jan 2013 issue of Nature. 19 pages, 4 figures, 1
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The clustering of galaxies at z~0.5 in the SDSS-III Data Release 9 BOSS-CMASS sample: a test for the LCDM cosmology
We present results on the clustering of 282,068 galaxies in the Baryon
Oscillation Spectroscopic Survey (BOSS) sample of massive galaxies with
redshifts 0.4<z<0.7 which is part of the Sloan Digital Sky Survey III project.
Our results cover a large range of scales from ~0.5 to ~90 Mpc/h. We compare
these estimates with the expectations of the flat LCDM cosmological model with
parameters compatible with WMAP7 data. We use the MultiDark cosmological
simulation together with a simple halo abundance matching technique, to
estimate galaxy correlation functions, power spectra, abundance of subhaloes
and galaxy biases. We find that the LCDM model gives a reasonable description
to the observed correlation functions at z~0.5, which is a remarkably good
agreement considering that the model, once matched to the observed abundance of
BOSS galaxies, does not have any free parameters. However, we find a deviation
(>~10%) in the correlation functions for scales less than ~1 Mpc/h and ~10-40
Mpc/h. A more realistic abundance matching model and better statistics from
upcoming observations are needed to clarify the situation. We also estimate
that about 12% of the "galaxies" in the abundance-matched sample are satellites
inhabiting central haloes with mass M>~1e14 M_sun/h. Using the MultiDark
simulation we also study the real space halo bias b(r) of the matched catalogue
finding that b=2.00+/-0.07 at large scales, consistent with the one obtained
using the measured BOSS projected correlation function. Furthermore, the linear
large-scale bias depends on the number density n of the abundance-matched
sample as b=-0.048-(0.594+/-0.02)*log(n/(h/Mpc)^3). Extrapolating these results
to BAO scales we measure a scale-dependent damping of the acoustic signal
produced by non-linear evolution that leads to ~2-4% dips at ~3 sigma level for
wavenumbers k>~0.1 h/Mpc in the linear large-scale bias.Comment: Replaced to match published version. Typos corrected; 25 pages, 17
figures, 9 tables. To appear in MNRAS. Correlation functions (projected and
redshift-space) and correlation matrices of CMASS presented in Appendix B.
Correlation and covariance data for the combined CMASS sample can be
downloaded from http://www.sdss3.org/science/boss_publications.ph
LSST Science Book, Version 2.0
A survey that can cover the sky in optical bands over wide fields to faint
magnitudes with a fast cadence will enable many of the exciting science
opportunities of the next decade. The Large Synoptic Survey Telescope (LSST)
will have an effective aperture of 6.7 meters and an imaging camera with field
of view of 9.6 deg^2, and will be devoted to a ten-year imaging survey over
20,000 deg^2 south of +15 deg. Each pointing will be imaged 2000 times with
fifteen second exposures in six broad bands from 0.35 to 1.1 microns, to a
total point-source depth of r~27.5. The LSST Science Book describes the basic
parameters of the LSST hardware, software, and observing plans. The book
discusses educational and outreach opportunities, then goes on to describe a
broad range of science that LSST will revolutionize: mapping the inner and
outer Solar System, stellar populations in the Milky Way and nearby galaxies,
the structure of the Milky Way disk and halo and other objects in the Local
Volume, transient and variable objects both at low and high redshift, and the
properties of normal and active galaxies at low and high redshift. It then
turns to far-field cosmological topics, exploring properties of supernovae to
z~1, strong and weak lensing, the large-scale distribution of galaxies and
baryon oscillations, and how these different probes may be combined to
constrain cosmological models and the physics of dark energy.Comment: 596 pages. Also available at full resolution at
http://www.lsst.org/lsst/sciboo
IL-10 transcription is negatively regulated by BAF180, a component of the SWI/SNF chromatin remodeling enzyme
<p>Abstract</p> <p>Background</p> <p>SWI/SNF chromatin remodeling enzymes play a critical role in the development of T helper lymphocytes, including Th2 cells, and directly program chromatin structure at Th2 cytokine genes. Different versions of SWI/SNF complexes, including BAF and PBAF, have been described based on unique subunit composition. However, the relative role of BAF and PBAF in Th cell function and cytokine expression has not been reported.</p> <p>Results</p> <p>Here we examine the role of the PBAF SWI/SNF complex in Th cell development and gene expression using mice deficient for a PBAF-specific component, BAF180. We find that T cell development in the thymus and lymphoid periphery is largely normal when the BAF180 gene is deleted late in thymic development. However, BAF180-deficient Th2 cells express high levels of the immunoregulatory cytokine IL-10. BAF180 binds directly to regulatory elements in the Il-10 locus but is replaced by BAF250 BAF complexes in the absence of BAF180, resulting in increased histone acetylation and CBP recruitment to the IL-10 locus.</p> <p>Conclusions</p> <p>These results demonstrate that BAF180 is a repressor of IL-10 transcription in Th2 cells and suggest that the differential recruitment of different SWI/SNF subtypes can have direct consequences on chromatin structure and gene transcription.</p
SOX2 Co-Occupies Distal Enhancer Elements with Distinct POU Factors in ESCs and NPCs to Specify Cell State
SOX2 is a master regulator of both pluripotent embryonic stem cells (ESCs) and multipotent neural progenitor cells (NPCs); however, we currently lack a detailed understanding of how SOX2 controls these distinct stem cell populations. Here we show by genome-wide analysis that, while SOX2 bound to a distinct set of gene promoters in ESCs and NPCs, the majority of regions coincided with unique distal enhancer elements, important cis-acting regulators of tissue-specific gene expression programs. Notably, SOX2 bound the same consensus DNA motif in both cell types, suggesting that additional factors contribute to target specificity. We found that, similar to its association with OCT4 (Pou5f1) in ESCs, the related POU family member BRN2 (Pou3f2) co-occupied a large set of putative distal enhancers with SOX2 in NPCs. Forced expression of BRN2 in ESCs led to functional recruitment of SOX2 to a subset of NPC-specific targets and to precocious differentiation toward a neural-like state. Further analysis of the bound sequences revealed differences in the distances of SOX and POU peaks in the two cell types and identified motifs for additional transcription factors. Together, these data suggest that SOX2 controls a larger network of genes than previously anticipated through binding of distal enhancers and that transitions in POU partner factors may control tissue-specific transcriptional programs. Our findings have important implications for understanding lineage specification and somatic cell reprogramming, where SOX2, OCT4, and BRN2 have been shown to be key factors
Post-Operative Functional Outcomes in Early Age Onset Rectal Cancer
Background: Impairment of bowel, urogenital and fertility-related function in patients treated for rectal cancer is common. While the rate of rectal cancer in the young (<50 years) is rising, there is little data on functional outcomes in this group. Methods: The REACCT international collaborative database was reviewed and data on eligible patients analysed. Inclusion criteria comprised patients with a histologically confirmed rectal cancer, <50 years of age at time of diagnosis and with documented follow-up including functional outcomes. Results: A total of 1428 (n=1428) patients met the eligibility criteria and were included in the final analysis. Metastatic disease was present at diagnosis in 13%. Of these, 40% received neoadjuvant therapy and 50% adjuvant chemotherapy. The incidence of post-operative major morbidity was 10%. A defunctioning stoma was placed for 621 patients (43%); 534 of these proceeded to elective restoration of bowel continuity. The median follow-up time was 42 months. Of this cohort, a total of 415 (29%) reported persistent impairment of functional outcomes, the most frequent of which was bowel dysfunction (16%), followed by bladder dysfunction (7%), sexual dysfunction (4.5%) and infertility (1%). Conclusion: A substantial proportion of patients with early-onset rectal cancer who undergo surgery report persistent impairment of functional status. Patients should be involved in the discussion regarding their treatment options and potential impact on quality of life. Functional outcomes should be routinely recorded as part of follow up alongside oncological parameters
Social Networks of Researchers and Educators on nanoHUB.org
The science gateway nanoHUB.org is the world’s largest nanotechnology user facility, serving 167,196 users in 2010 with over 2,300 resources including 189 simulation programs. Surveys of nanoHUB users and automated usage analysis find widespread simulation use in formal classroom education, thereby connecting recent research more rapidly and closely to education. Analysis of 719 citations in the scientific literature by over 1,300 authors to nanoHUB.org resources documents use of simulation programs by new research collaborations, by researchers outside of the community originating the program, and by experimentalists. The publication and author networks reveal research collaborations and capacity building through knowledge transfer. Analysis of secondary citations documents the quality of the conducted research with an h-index of 30 after just 10 years of operation. Our analysis proves with quantitative metrics that impactful research can be conducted by an ever growing research community. We argue that HUBzero technology and the user- focused design and operation of nanoHUB.org are success criteria that can be transferred to other science gateways
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