17,167 research outputs found
The Properties of Radio Galaxies and the Effect of Environment in Large Scale Structures at
In this study we investigate 89 radio galaxies that are
spectroscopically-confirmed to be members of five large scale structures in the
redshift range of . Based on a two-stage classification
scheme, the radio galaxies are classified into three sub-classes: active
galactic nucleus (AGN), hybrid, and star-forming galaxy (SFG). We study the
properties of the three radio sub-classes and their global and local
environmental preferences. We find AGN hosts are the most massive population
and exhibit quiescence in their star-formation activity. The SFG population has
a comparable stellar mass to those hosting a radio AGN but are unequivocally
powered by star formation. Hybrids, though selected as an intermediate
population in our classification scheme, were found in almost all analyses to
be a unique type of radio galaxies rather than a mixture of AGN and SFGs. They
are dominated by a high-excitation radio galaxy (HERG) population. We discuss
environmental effects and scenarios for each sub-class. AGN tend to be
preferentially located in locally dense environments and in the cores of
clusters/groups, with these preferences persisting when comparing to galaxies
of similar colour and stellar mass, suggesting that their activity may be
ignited in the cluster/group virialized core regions. Conversely, SFGs exhibit
a strong preference for intermediate-density global environments, suggesting
that dusty starbursting activity in LSSs is largely driven by galaxy-galaxy
interactions and merging.Comment: 28 pages, 10 figures, accepted to MNRA
The SAGA Survey: I. Satellite Galaxy Populations Around Eight Milky Way Analogs
We present the survey strategy and early results of the "Satellites Around
Galactic Analogs" (SAGA) Survey. The SAGA Survey's goal is to measure the
distribution of satellite galaxies around 100 systems analogous to the Milky
Way down to the luminosity of the Leo I dwarf galaxy (). We
define a Milky Way analog based on -band luminosity and local environment.
Here, we present satellite luminosity functions for 8 Milky Way analog galaxies
between 20 to 40 Mpc. These systems have nearly complete spectroscopic coverage
of candidate satellites within the projected host virial radius down to using low redshift color criteria. We have discovered a total of
25 new satellite galaxies: 14 new satellite galaxies meet our formal criteria
around our complete host systems, plus 11 additional satellites in either
incompletely surveyed hosts or below our formal magnitude limit. Combined with
13 previously known satellites, there are a total of 27 satellites around 8
complete Milky Way analog hosts. We find a wide distribution in the number of
satellites per host, from 1 to 9, in the luminosity range for which there are
five Milky Way satellites. Standard abundance matching extrapolated from higher
luminosities predicts less scatter between hosts and a steeper luminosity
function slope than observed. We find that the majority of satellites (26 of
27) are star-forming. These early results indicate that the Milky Way has a
different satellite population than typical in our sample, potentially changing
the physical interpretation of measurements based only on the Milky Way's
satellite galaxies.Comment: 22 pages, 19 figures, 2 tables. Updated to published version. Survey
website: http://sagasurvey.org
Characterization of Metabolic, Diffusion, and Perfusion Properties in GBM: Contrast-Enhancing versus Non-Enhancing Tumor.
BackgroundAlthough the contrast-enhancing (CE) lesion on T1-weighted MR images is widely used as a surrogate for glioblastoma (GBM), there are also non-enhancing regions of infiltrative tumor within the T2-weighted lesion, which elude radiologic detection. Because non-enhancing GBM (Enh-) challenges clinical patient management as latent disease, this study sought to characterize ex vivo metabolic profiles from Enh- and CE GBM (Enh+) samples, alongside histological and in vivo MR parameters, to assist in defining criteria for estimating total tumor burden.MethodsFifty-six patients with newly diagnosed GBM received a multi-parametric pre-surgical MR examination. Targets for obtaining image-guided tissue samples were defined based on in vivo parameters that were suspicious for tumor. The actual location from where tissue samples were obtained was recorded, and half of each sample was analyzed for histopathology while the other half was scanned using HR-MAS spectroscopy.ResultsThe Enh+ and Enh- tumor samples demonstrated comparable mitotic activity, but also significant heterogeneity in microvascular morphology. Ex vivo spectroscopic parameters indicated similar levels of total choline and N-acetylaspartate between these contrast-based radiographic subtypes of GBM, and characteristic differences in the levels of myo-inositol, creatine/phosphocreatine, and phosphoethanolamine. Analysis of in vivo parameters at the sample locations were consistent with histological and ex vivo metabolic data.ConclusionsThe similarity between ex vivo levels of choline and NAA, and between in vivo levels of choline, NAA and nADC in Enh+ and Enh- tumor, indicate that these parameters can be used in defining non-invasive metrics of total tumor burden for patients with GBM
Extragalactic Science, Cosmology and Galactic Archaeology with the Subaru Prime Focus Spectrograph (PFS)
The Subaru Prime Focus Spectrograph (PFS) is a massively-multiplexed
fiber-fed optical and near-infrared 3-arm spectrograph (N_fiber=2400,
380<lambda<1260nm, 1.3 degree diameter FoV), offering unique opportunities in
survey astronomy. Here we summarize the science case feasible for a survey of
Subaru 300 nights. We describe plans to constrain the nature of dark energy via
a survey of emission line galaxies spanning a comoving volume of 9.3 (Gpc/h)^3
in the redshift range 0.8<z<2.4. In each of 6 redshift bins, the cosmological
distances will be measured to 3% precision via BAO, and redshift-space
distortions will be used to constrain structure growth to 6% precision. In the
GA program, radial velocities and chemical abundances of stars in the Milky Way
and M31 will be used to infer the past assembly histories of spiral galaxies
and the structure of their dark matter halos. Data will be secured for 10^6
stars in the Galactic thick-disk, halo and tidal streams as faint as V~22,
including stars with V < 20 to complement the goals of the Gaia mission. A
medium-resolution mode with R = 5000 to be implemented in the red arm will
allow the measurement of multiple alpha-element abundances and more precise
velocities for Galactic stars, elucidating the detailed chemo-dynamical
structure and evolution of each of the main stellar components of the Milky Way
Galaxy and of its dwarf spheroidal galaxies. For the extragalactic program, our
simulations suggest the wide avelength range will be powerful in probing the
galaxy population and its clustering over a wide redshift range. We propose to
conduct a color-selected survey of 1<z<2 galaxies and AGN over 16 deg^2 to
J~23.4, yielding a fair sample of galaxies with stellar masses above ~10^{10}Ms
at z~2. A two-tiered survey of higher redshift LBGs and LAEs will quantify the
properties of early systems close to the reionization epoch.Comment: This document describes the scientific program and requirements for
the Subaru Prime Focus Spectrograph (PFS) project. Made significant revision
based on studies for the Preliminary Design Review (PRD) held in Feb 2013.
The higher-resolution paper file is available from
http://member.ipmu.jp/masahiro.takada/pfs_astroph_rv.pd
The NGC 5846 Group: Dynamics and the Luminosity Function to M_R=-12
We conduct a photometric and spectroscopic survey of a 10 sq. deg. region
surrounding the nearby NGC 5846 group of galaxies, using the
Canada-France-Hawaii and Keck I telescopes to study the population of dwarf
galaxies as faint as M_R=-10. Candidates are identified on the basis of
quantitative surface brightness and qualitative morphological criteria.
Spectroscopic follow up and a spatial correlation analysis provide the basis
for affirming group memberships. Altogether, 324 candidates are identified and
83 have spectroscopic membership confirmation. We argue on statistical grounds
that a total 251 +/- 10 galaxies in our sample are group members. The
observations, together with archival Sloan Digital Sky Survey, ROSAT,
XMM-Newton, and ASCA data, suggest that the giant ellipticals NGC 5846 and NGC
5813 are the dominant components of subgroups separated by 600 kpc in
projection and embedded in a 1.6 Mpc diameter dynamically evolved halo. The
galaxy population is overwhelmingly early type. The group velocity dispersion
is 322 km/s, its virial mass is 8.4 x 10^13 M_sun, and M/L_R = 320 M_sun/L_sun.
The ratio of dwarfs to giants is large compared with other environments in the
Local Supercluster studied and, correspondingly, the luminosity function is
relatively steep, with a faint end Schechter function slope of \alpha_d = -1.3
+/- 0.1 (statistical) +/- 0.1 (systematic) at our completeness limit of M_R =
-12.Comment: 17 pages; accepted for publication in the Astronomical Journa
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Hyperpolarized 13C Spectroscopic Evaluation of Oxidative Stress in a Rodent Model of Steatohepatitis.
Nonalcoholic fatty liver disease (NAFLD) has become highly prevalent, now considered the most common liver disease in the western world. Approximately one-third of patients with NASH develop non-alchoholic steatohepatitis (NASH), histologically defined by lobular and portal inflammation, and accompanied by marked oxidative stress. Patients with NASH are at increased risk for cirrhosis and hepatocellular carcinoma, and diagnosis currently requires invasive biopsy. In animal models of NASH, particularly the methionine-choline deficient (MCD) model, profound changes are seen in redox enzymes and key intracellular antioxidants. To study antioxidant status in NASH non-invasively, we applied the redox probe hyperpolarized [1-13C] dehydroascorbic acid (HP DHA), which is reduced to Vitamin C (VitC) rapidly in the normal liver. In MCD mice, we observed a significant decrease in HP DHA to VitC conversion that accompanied hepatic fat deposition. When these animals were subsequently placed on a normal diet, resonance ratios reverted to those seen in control mice. These findings suggest that HP DHA, a potentially clinically translatable imaging agent, holds special promise in imaging NASH and other metabolic syndromes, to monitor disease progression and response to targeted therapies
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