157 research outputs found
Discovery of a new M32-like "Compact Elliptical" galaxy in the halo of the Abell 496 cD galaxy
Aims: ``Compact ellipticals'' are so rare that a search for M32 analogs is
needed to ensure the very existence of this class. Methods: We report here the
discovery of A496cE, a M32 twin in the cluster Abell 496, located in the halo
of the central cD. Results: Based on CFHT and HST imaging we show that the
light profile of A496cE requires a two component fit: a Sersic bulge and an
exponential disc. The spectrum of A496cE obtained with the ESO-VLT
FLAMES/Giraffe spectrograph can be fit by a stellar synthesis spectrum
dominated by old stars, with high values of [Mg/Fe] and velocity dispersion.
Conclusions: The capture of A496cE by the cD galaxy and tidal stripping of most
of its disc are briefly discussed.Comment: 4 pages, 4 figures, accepted for publication in A&A Letter
The SAURON project. II. Sample and early results
Early results are reported from the SAURON survey of the kinematics and
stellar populations of a representative sample of nearby E, S0 and Sa galaxies.
The survey is aimed at determining the intrinsic shape of the galaxies, their
orbital structure, the mass-to-light ratio as a function of radius, the age and
metallicity of the stellar populations, and the frequency of kinematically
decoupled cores and nuclear black holes. The construction of the representative
sample is described, and its properties are illustrated. A comparison with
long-slit spectroscopic data establishes that the SAURON measurements are
comparable to, or better than, the highest-quality determinations. Comparisons
are presented for NGC 3384 and NGC 4365 where stellar velocities and velocity
dispersions are determined to a precision of 6 km/s, and the h3 and h4
parameters of the line-of-sight velocity distribution to a precision of better
than 0.02. Extraction of accurate gas emission-line intensities, velocities and
line widths from the datacubes is illustrated for NGC 5813. Comparisons with
published line-strengths for NGC 3384 and NGC 5813 reveal uncertainties of <
0.1 A on the measurements of the Hbeta, Mgb and Fe5270 indices. Integral-field
mapping uniquely connects measurements of the kinematics and stellar
populations to the galaxy morphology. The maps presented here illustrate the
rich stellar kinematics, gaseous kinematics, and line-strength distributions of
early-type galaxies. The results include the discovery of a thin, edge-on, disk
in NGC 3623, confirm the axisymmetric shape of the central region of M32,
illustrate the LINER nucleus and surrounding counter-rotating star-forming ring
in NGC 7742, and suggest a uniform stellar population in the decoupled core
galaxy NGC 5813.Comment: 20 pages, 17 figures. To be published in MNRAS. Version with full
resolution images available at
http://www.strw.leidenuniv.nl/~dynamics/Instruments/Sauron/pub_list.htm
Quasars Probing Quasars III: New Clues to Feedback, Quenching, and the Physics of Massive Galaxy Formation
Galaxies hosting z~2 quasars are the high- progenitors of today's massive
`red-and-dead' galaxies. With close pairs of quasars at different redshifts, a
background quasar can be used to study a foreground quasar's halo gas in
absorption, providing a wealth of information about feedback, quenching, and
the physics of massive galaxy formation. We present a Keck/HIRES spectrum of
the bright background quasar in a projected pair with angular separation 13.3"
corresponding to 108kpc at the redshift of the foreground quasar z_fg=2.4360
+/- 0.0005, precisely determined from Gemini/GNIRS near-IR spectroscopy. Our
echelle spectrum reveals optically thick gas (NHI~10^19.7), coincident with the
foreground quasar redshift. The ionic transitions of associated metal-lines
reveal the following properties of the foreground quasar's halo: (1) the
kinematics are extreme with absorption extending to +780km/s relative to z_fg;
(2) the metallicity is nearly solar; (3) the temperature of the predominantly
ionized gas is T<~20,000K; (4) the electron density is n_e~1 cm^-3 indicating a
characteristic size ~10 - 100pc for the absorbing `clouds'; (7) there is a
negligible amount of warm gas 10^5K < T < 10^6K; (8) the gas is unlikely
illuminated by the foreground quasar, implying anisotropic or intermittent
emission. The mass of cold T~10^4K gas implied by our observations is
significant, amounting to a few percent of the total expected baryonic mass
density of the foreground quasar's dark halo at r~100kpc. The origin of this
material is still unclear, and we discuss several possibilities in the context
of current models of feedback and massive galaxy formation.Comment: Accepted to ApJ. 38 pages, 11 figure
Identification and localization of minimal MHC-restricted CD8+ T cell epitopes within the Plasmodium falciparum AMA1 protein
<p>Abstract</p> <p>Background</p> <p><it>Plasmodium falciparum </it>apical membrane antigen-1 (AMA1) is a leading malaria vaccine candidate antigen that is expressed by sporozoite, liver and blood stage parasites. Since CD8+ T cell responses have been implicated in protection against pre-erythrocytic stage malaria, this study was designed to identify MHC class I-restricted epitopes within AMA1.</p> <p>Methods</p> <p>A recombinant adenovirus serotype 5 vector expressing <it>P. falciparum </it>AMA1 was highly immunogenic when administered to healthy, malaria-naive adult volunteers as determined by IFN-γ ELISpot responses to peptide pools containing overlapping 15-mer peptides spanning full-length AMA1. Computerized algorithms (NetMHC software) were used to predict minimal MHC-restricted 8-10-mer epitope sequences within AMA1 15-mer peptides active in ELISpot. A subset of epitopes was synthesized and tested for induction of CD8+ T cell IFN-γ responses by ELISpot depletion and ICS assays. A 3-dimensional model combining Domains I + II of <it>P. falciparum </it>AMA1 and Domain III of <it>P. vivax </it>AMA1 was used to map these epitopes.</p> <p>Results</p> <p>Fourteen 8-10-mer epitopes were predicted to bind to HLA supertypes A01 (3 epitopes), A02 (4 epitopes), B08 (2 epitopes) and B44 (5 epitopes). Nine of the 14 predicted epitopes were recognized in ELISpot or ELISpot and ICS assays by one or more volunteers. Depletion of T cell subsets confirmed that these epitopes were CD8+ T cell-dependent. A mixture of the 14 minimal epitopes was capable of recalling CD8+ T cell IFN-γ responses from PBMC of immunized volunteers. Thirteen of the 14 predicted epitopes were polymorphic and the majority localized to the more conserved front surface of the AMA1 model structure.</p> <p>Conclusions</p> <p>This study predicted 14 and confirmed nine MHC class I-restricted CD8+ T cell epitopes on AMA1 recognized in the context of seven HLA alleles. These HLA alleles belong to four HLA supertypes that have a phenotypic frequency between 23% - 100% in different human populations.</p
Elliptical Galaxies and Bulges of Disk Galaxies: Summary of Progress and Outstanding Issues
This is the summary chapter of a review book on galaxy bulges. Bulge
properties and formation histories are more varied than those of ellipticals. I
emphasize two advances: 1 - "Classical bulges" are observationally
indistinguishable from ellipticals, and like them, are thought to form by major
galaxy mergers. "Disky pseudobulges" are diskier and more actively star-forming
(except in S0s) than are ellipticals. Theys are products of the slow
("secular") evolution of galaxy disks: bars and other nonaxisymmetries move
disk gas toward the center, where it starbursts and builds relatively flat,
rapidly rotating components. This secular evolution is a new area of galaxy
evolution work that complements hierarchical clustering. 2 - Disks of
high-redshift galaxies are unstable to the formation of mass clumps that sink
to the center and merge - an alternative channel for the formation of classical
bulges. I review successes and unsolved problems in the formation of
bulges+ellipticals and their coevolution (or not) with supermassive black
holes. I present an observer's perspective on simulations of dark matter galaxy
formation including baryons. I review how our picture of the quenching of star
formation is becoming general and secure at redshifts z < 1. The biggest
challenge is to produce realistic bulges+ellipticals and disks that overlap
over a factor of 10**3 in mass but that differ from each other as observed over
that whole range. Second, how does hierarchical clustering make so many giant,
bulgeless galaxies in field but not cluster environments? I argue that we rely
too much on AGN and star-formation feedback to solve these challenges.Comment: 46 pages, 10 postscript figures, accepted for publication in Galactic
Bulges, ed. E. Laurikainen, R. F. Peletier, & D. A. Gadotti (New York:
Springer), in press (2015
A standardized protocol for blood and cerebrospinal fluid collection and processing for biomarker research in ataxia
The European Spinocerebellar Ataxia Type 3/Machado-Joseph Disease Initiative (ESMI) is a consortium established with the ambition to set up the largest European longitudinal trial-ready cohort of Spinocerebellar Ataxia Type 3/Machado Joseph disease (SCA3/MJD), the most common autosomal dominantly inherited ataxia worldwide. A major focus of ESMI has been the identification of SCA3/MJD biomarkers to enable future interventional studies. As biosample collection and processing variables significantly impact the outcomes of biomarkers studies, biosampling procedures standardization was done previously to study visit initiation. Here, we describe the ESMI consensus biosampling protocol, developed within the scope of ESMI, that ultimately might be translated to other neurodegenerative disorders, particularly ataxias, being the first step to protocol harmonization in the field
Kinematics and Stellar Populations of Low-Luminosity Early-Type Galaxies in the Abell 496 Cluster
The morphology and stellar populations of low-luminosity early-type galaxies
in clusters have until now been limited to a few relatively nearby clusters
such as Virgo or Fornax. Scenarii for the formation and evolution of dwarf
galaxies in clusters are therefore not well constrained. We investigate here
the morphology and stellar populations of low-luminosity galaxies in the
relaxed cluster Abell 496 (z=0.0330). Deep multiband imaging obtained with the
CFHT Megacam allowed us to select a sample of faint galaxies (-18.8<M_B<-15.1
mag). We observed 118 galaxies spectroscopically with the ESO VLT
FLAMES/Giraffe spectrograph (R=6300). We present structural analysis and colour
maps for the 48 galaxies belonging to the cluster. We fit the spectra of 46
objects with PEGASE.HR synthetic spectra to estimate the ages, metallicities,
and velocity dispersions. We computed values of /Fe abundance ratios
from the measurements of Lick indices. High-precision estimates of stellar
population properties have been obtained for a large sample of faint galaxies
in a cluster, allowing for the extension of relations between stellar
populations and internal kinematics to the low-velocity dispersion regime. We
have revealed a peculiar population of elliptical galaxies in the core of the
cluster, resembling massive early-type galaxies by their stellar population
properties and velocity dispersions, but having luminosities of about 2 mag
fainter. External mechanisms of gas removal (ram pressure stripping and
gravitational harassment) are more likely to have occurred than internal
mechanisms such as supernova-driven winds. The violent tidal stripping of
intermediate-luminosity, early-type galaxies in the cluster core can explain
the properties of the peculiar elliptical galaxies surrounding the cD galaxy.Comment: Accepted to A&A, 48 pages, 62 figures, 3 tables. This version
contains low-resolution figures. We encourage you to get the full-resolution
PDF (16Mb) from http://voplus.obspm.fr/DataCollections/Abell0496
The SAURON project - III. Integral-field absorption-line kinematics of 48 elliptical and lenticular galaxies
We present the stellar kinematics of 48 representative elliptical and
lenticular galaxies obtained with our custom-built integral-field spectrograph
SAURON operating on the William Herschel Telescope. The data were homogeneously
processed through a dedicated reduction and analysis pipeline. All resulting
SAURON datacubes were spatially binned to a constant minimum signal-to-noise.
We have measured the stellar kinematics with an optimized (penalized
pixel-fitting) routine which fits the spectra in pixel space, via the use of
optimal templates, and prevents the presence of emission lines to affect the
measurements. We have thus generated maps of the mean stellar velocity, the
velocity dispersion, and the Gauss-Hermite moments h3 and h4 of the
line-of-sight velocity distributions. The maps extend to approximately one
effective radius. Many objects display kinematic twists, kinematically
decoupled components, central stellar disks, and other peculiarities, the
nature of which will be discussed in future papers of this series.Comment: 23 pages, 18 figures. Accepted for publication in MNRAS. Version with
full resolution images available at
http://www.strw.leidenuniv.nl/sauron/papers/emsellem2004_sauron3.pd
Detecting Radio AGN Signatures in Red Geysers
A new class of quiescent galaxies harboring possible AGN-driven winds has been discovered using spatially resolved optical spectroscopy from the ongoing SDSS-IV MaNGA survey. These galaxies, termed "red geysers", constitute 5−10% of the local quiescent population and are characterized by narrow bisymmetric patterns in ionized gas emission features. Cheung et al. argued that these galaxies host large-scale AGN-driven winds that may play a role in suppressing star formation at late times. In this work, we test the hypothesis that AGN activity is ultimately responsible for the red geyser phenomenon. We compare the nuclear radio activity of the red geysers to a matched control sample with similar stellar mass, redshift, rest frame NUV−r color, axis ratio and presence of ionized gas. We have used the 1.4 GHz radio continuum data from VLA FIRST survey to stack the radio flux from the red geyser and control samples. In addition to a 3 times higher FIRST detection rate, we find that red geysers have a 5σ higher level of average radio flux than control galaxies. After restricting to rest-frame NUV−r color > 5 and checking mid-IR WISE photometry, we rule out star formation contamination and conclude that red geysers are associated with more active AGN. Red geysers and a possibly-related class with disturbed Hα emission account for 40\% of all radio-detected red galaxies with log (M⋆/M⊙)<11. Our results support a picture in which episodic AGN activity drives large-scale-relatively weak ionized winds that may provide a feedback mechanism for many early-type galaxies
The Toll→NFκB Signaling Pathway Mediates the Neuropathological Effects of the Human Alzheimer's Aβ42 Polypeptide in Drosophila
Alzheimer's (AD) is a progressive neurodegenerative disease that afflicts a significant fraction of older individuals. Although a proteolytic product of the Amyloid precursor protein, the Αβ42 polypeptide, has been directly implicated in the disease, the genes and biological pathways that are deployed during the process of Αβ42 induced neurodegeneration are not well understood and remain controversial. To identify genes and pathways that mediated Αβ42 induced neurodegeneration we took advantage of a Drosophila model for AD disease in which ectopically expressed human Αβ42 polypeptide induces cell death and tissue degeneration in the compound eye. One of the genes identified in our genetic screen is Toll (Tl). It encodes the receptor for the highly conserved Tl→NFkB innate immunity/inflammatory pathway and is a fly homolog of the mammalian Interleukin-1 (Ilk-1) receptor. We found that Tl loss-of-function mutations dominantly suppress the neuropathological effects of the Αβ42 polypeptide while gain-of-function mutations that increase receptor activity dominantly enhance them. Furthermore, we present evidence demonstrating that Tl and key downstream components of the innate immunity/inflammatory pathway play a central role in mediating the neuropathological activities of Αβ42. We show that the deleterious effects of Αβ42 can be suppressed by genetic manipulations of the Tl→NFkB pathway that downregulate signal transduction. Conversely, manipulations that upregulate signal transduction exacerbate the deleterious effects of Aβ42. Since postmortem studies have shown that the Ilk-1→NFkB innate immunity pathway is substantially upregulated in the brains of AD patients, the demonstration that the Tl→NFkB signaling actively promotes the process of Αβ42 induced cell death and tissue degeneration in flies points to possible therapeutic targets and strategies
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