683 research outputs found
Local Group Dwarf Spheroidals: Correlated Deviations from the Baryonic Tully-Fisher Relation
Local Group dwarf spheroidal satellite galaxies are the faintest
extragalactic stellar systems known. We examine recent data for these objects
in the plane of the Baryonic Tully-Fisher Relation (BTFR). While some dwarf
spheroidals adhere to the BTFR, others deviate substantially. We examine the
residuals from the BTFR and find that they are not random. The residuals
correlate with luminosity, size, metallicity, ellipticity, and susceptibility
of the dwarfs to tidal disruption in the sense that fainter, more elliptical,
and tidally more susceptible dwarfs deviate farther from the BTFR. These
correlations disfavor stochastic processes and suggest a role for tidal
effects. We identify a test to distinguish between the {\Lambda}CDM and MOND
based on the orbits of the dwarf satellites of the Milky Way and how stars are
lost from them.Comment: 16 pages, 7 figures. Submitted to ApJ. Revised in response to referee
repor
A decade of GRB follow-up by BOOTES in Spain (2003-2013)
This article covers ten years of GRB follow-ups by the Spanish BOOTES
stations: 71 follow-ups providing 23 detections. Follow-ups by BOOTES-1B from
2005 to 2008 were given in the previous article, and are here reviewed,
updated, and include additional detection data points as the former article
merely stated their existence. The all-sky cameras CASSANDRA have not yet
detected any GRB optical afterglows, but limits are reported where available
Understanding local Dwarf Spheroidals and their scaling relations under MOdified Newtonian Dynamics
We use a specific form of the interpolation function in the MOND formalism,
which optimally accounts for the internal structure of dwarf spheroidal (dSph)
galaxies, to explore the consequences it has on the scaling relations seen in
these systems.}} {{The particular form of the interpolation function we used
leads to a law of gravity that does not degrade the good fit of the MOND
proposal on galactic scales, and in fact, slightly improves the accordance with
observations at dSph scales. This formalism yields a good description of
gravitational phenomena without the need of invoking any still undetected and
hypothetically dominant dark matter, in the weak field regime probed by local
dSph galaxies.}} {{Isothermal equilibrium density profiles then yield projected
surface density profiles for the local dSph galaxies in very good agreement
with observational determinations, for values of the relevant parameters as
inferred from recent observations of these Galactic satellites. The observed
scaling relations for these systems are also naturally accounted for within the
proposed scheme, including a previously unrecognised correlation of the
inferred mass-to-light ratios of local dSph's with the ages of their stellar
populations, which is natural in modified gravity schemes in the absence of
dark matter.}} {The results shed some light on the form that the MOND
interpolating function may have in the most challenging regime, which occurs at
moderate accelerations and intermediate mass--weighted lengths.Comment: 8 pages, 4 figures, 1 table, Accepted for publication in Astronomy
and Astrophysics. Copy matches published versio
On the Efficiency of the Tidal Stirring Mechanism for the Origin of Dwarf Spheroidals: Dependence on the Orbital and Structural Parameters of the Progenitor Disky Dwarfs
(Abridged) The tidal stirring model posits the formation of dSph galaxies via
the tidal interactions between rotationally-supported dwarfs and MW-sized host
galaxies. Using a set of collisionless N-body simulations, we investigate the
efficiency of the tidal stirring mechanism. We explore a wide variety of dwarf
orbital configurations and initial structures and demonstrate that in most
cases the disky dwarfs experience significant mass loss and their stellar
components undergo a dramatic morphological and dynamical transformation: from
disks to bars and finally to pressure-supported spheroidal systems with
kinematic and structural properties akin to those of the classic dSphs in the
Local Group (LG). Our results suggest that such tidal transformations should be
common occurrences within the currently favored cosmological paradigm and
highlight the key factor responsible for an effective metamorphosis to be the
strength of the tidal shocks at the pericenters of the orbit. We demonstrate
that the combination of short orbital times and small pericenters,
characteristic of dwarfs being accreted at high redshift, induces the strongest
transformations. Our models also indicate that the transformation efficiency is
affected significantly by the structure of the progenitor disky dwarfs. Lastly,
we find that the dwarf remnants satisfy the relation Vmax = \sqrt{3} * sigma,
where sigma is the 1D, central stellar velocity dispersion and Vmax is the
maximum halo circular velocity, with intriguing implications for the missing
satellites problem. Overall, we conclude that the action of tidal forces from
the hosts constitutes a crucial evolutionary mechanism for shaping the nature
of dwarf galaxies in environments such as that of the LG. Environmental
processes of this type should thus be included as ingredients in models of
dwarf galaxy formation and evolution.Comment: submitted to ApJ, 34 pages, 15 figures, LaTeX (uses emulateapj.cls
A genome-wide association study follow-up suggests a possible role for PPARG in systemic sclerosis susceptibility
Introduction:
A recent genome-wide association study (GWAS) comprising a French cohort of systemic sclerosis (SSc) reported several non-HLA single-nucleotide polymorphisms (SNPs) showing a nominal association in the discovery phase. We aimed to identify previously overlooked susceptibility variants by using a follow-up strategy.<p></p>
Methods:
Sixty-six non-HLA SNPs showing a P value <10-4 in the discovery phase of the French SSc GWAS were analyzed in the first step of this study, performing a meta-analysis that combined data from the two published SSc GWASs. A total of 2,921 SSc patients and 6,963 healthy controls were included in this first phase. Two SNPs, PPARG rs310746 and CHRNA9 rs6832151, were selected for genotyping in the replication cohort (1,068 SSc patients and 6,762 healthy controls) based on the results of the first step. Genotyping was performed by using TaqMan SNP genotyping assays.
Results:
We observed nominal associations for both PPARG rs310746 (PMH = 1.90 × 10-6, OR, 1.28) and CHRNA9 rs6832151 (PMH = 4.30 × 10-6, OR, 1.17) genetic variants with SSc in the first step of our study. In the replication phase, we observed a trend of association for PPARG rs310746 (P value = 0.066; OR, 1.17). The combined overall Mantel-Haenszel meta-analysis of all the cohorts included in the present study revealed that PPARG rs310746 remained associated with SSc with a nominal non-genome-wide significant P value (PMH = 5.00 × 10-7; OR, 1.25). No evidence of association was observed for CHRNA9 rs6832151 either in the replication phase or in the overall pooled analysis.<p></p>
Conclusion:
Our results suggest a role of PPARG gene in the development of SSc
Biologic Therapy in Refractory Non-Multiple Sclerosis Optic Neuritis Isolated or Associated to Immune Mediated Inflammatory Diseases. A Multicenter Study
We aimed to assess the e cacy of biologic therapy in refractory non-Multiple Sclerosis
(MS) Optic Neuritis (ON), a condition more infrequent, chronic and severe than MS ON. This was
an open-label multicenter study of patients with non-MS ON refractory to systemic corticosteroids
and at least one conventional immunosuppressive drug. The main outcomes were Best Corrected
Visual Acuity (BCVA) and both Macular Thickness (MT) and Retinal Nerve Fiber Layer (RNFL) using
Optical Coherence Tomography (OCT). These outcome variables were assessed at baseline, 1 week,
and 1, 3, 6 and 12 months after biologic therapy initiation. Remission was defined as the absence of ON symptoms and signs that lasted longer than 24 h, with or without an associated new lesion
on magnetic resonance imaging with gadolinium contrast agents for at least 3 months. We studied
19 patients (11 women/8 men; mean age, 34.8 13.9 years). The underlying diseases were Bechet?s
disease (n = 5), neuromyelitis optica (n = 3), systemic lupus erythematosus (n = 2), sarcoidosis (n = 1),
relapsing polychondritis (n = 1) and anti-neutrophil cytoplasmic antibody -associated vasculitis (n = 1).
It was idiopathic in 6 patients. The first biologic agent used in each patient was: adalimumab (n = 6),
rituximab (n = 6), infliximab (n = 5) and tocilizumab (n = 2). A second immunosuppressive drug was
simultaneously used in 11 patients: methotrexate (n = 11), azathioprine (n = 2), mycophenolate mofetil
(n = 1) and hydroxychloroquine (n = 1). Improvement of the main outcomes was observed after 1 year
of therapy when compared with baseline data: mean SD BCVA (0.8 0.3 LogMAR vs. 0.6 0.3
LogMAR; p = 0.03), mean SD RNFL (190.5 175.4 m vs. 183.4 139.5 m; p = 0.02), mean SD
MT (270.7 23.2 m vs. 369.6 137.4 m; p = 0.03). Besides, the median (IQR) prednisone-dose was
also reduced from 40 (10?61.5) mg/day at baseline to. 2.5 (0?5) mg/day after one year of follow-up;
p = 0.001. After a mean SD follow-up of 35 months, 15 patients (78.9%) achieved ocular remission,
and 2 (10.5%) experienced severe adverse events. Biologic therapy is e ective in patients with
refractory non-MS ON
Next generation flow for minimally-invasive blood characterization of MGUS and multiple myeloma at diagnosis based on circulating tumor plasma cells (CTPC)
© The Author(s) 2018.Here, we investigated for the first time the frequency and number of circulating tumor plasma cells (CTPC) in peripheral blood (PB) of newly diagnosed patients with localized and systemic plasma cell neoplasms (PCN) using next-generation flow cytometry (NGF) and correlated our findings with the distinct diagnostic and prognostic categories of the disease. Overall, 508 samples from 264 newly diagnosed PCN patients, were studied. CTPC were detected in PB of all active multiple myeloma (MM; 100%), and smoldering MM (SMM) patients (100%), and in more than half (59%) monoclonal gammopathy of undetermined significance (MGUS) cases (p <0.0001); in contrast, CTPC were present in a small fraction of solitary plasmacytoma patients (18%). Higher numbers of CTPC in PB were associated with higher levels of BM infiltration and more adverse prognostic features, together with shorter time to progression from MGUS to MM (p <0.0001) and a shorter survival in MM patients with active disease requiring treatment (p ≤ 0.03). In summary, the presence of CTPC in PB as assessed by NGF at diagnosis, emerges as a hallmark of disseminated PCN, higher numbers of PB CTPC being strongly associated with a malignant disease behavior and a poorer outcome of both MGUS and MM.This work has been supported by the International Myeloma Foundation-Black Swan Research Initiative and the EuroFlow Consortium; Centro de Investigación Biomédica en Red de Cáncer (CIBER-ONC; Instituto de Salud Carlos III, Ministerio de Economía y Competitividad, Madrid, Spain and FONDOS FEDER), numbers: CB16/12/00400, CB16/12/00369, CB16/12/00489 and CB16/12/00233; grant SA079U14 from the Consejería de Educación, Junta de Castilla y León, Valladolid, Spain and; grant DTS15/00119 from Instituto de Salud Carlos III, Ministerio de Economía y Competitividad, Madrid, Spain. Acuerdo de colaboración con Fundación de Hemoterapia y Hemodonación de Castilla y León, Valladolid, Spain. This study was also supported by the Qatar National Research Fund (QNRF) Award No. 7-916-3-237, the AACR-Millennium Fellowship in Multiple Myeloma Research (15-40-38-PAIV), ERA-NET TRANSCAN-2 (iMMunocell), by a 2017 Leonardo Grant (BZG10931) for Researchers and Cultural Creators, BBVA Foundation, and the European Research Council (ERC) 2015 Starting Grant (MYELOMANEXT)
A unique isolated dwarf spheroidal galaxy at D=1.9 Mpc
We present a photometric and spectroscopic study of the unique isolated
nearby dSph galaxy KKR25. The galaxy was resolved into stars with HST/WFPC2
including old red giant branch and red clump. We have constructed a model of
the resolved stellar populations and measured the star formation rate and
metallicity as function of time. The main star formation activity period
occurred about 12.6 to 13.7 Gyr ago. These stars are mostly metal-poor, with a
mean metallicity [Fe/H]\sim -1 to -1.6 dex. About 60 per cent of the total
stellar mass was formed during this event. There are indications of
intermediate age star formation in KKR25 between 1 and 4 Gyr with no
significant signs of metal enrichment for these stars. Long-slit spectroscopy
was carried out using the Russian 6-m telescope of the integrated starlight and
bright individual objects in the galaxy. We have discovered a planetary nebula
(PN) in KKR25. This is the first known PN in a dwarf spheroidal galaxy outside
the Local Group. We have measured its oxygen abundance 12+log(O/H)=7.60+-0.07
dex and a radial velocity Vh=-79 km/s. We have analysed the stellar density
distribution in the galaxy body. The galaxy has an exponential surface
brightness profile with a central light depression. We discuss the evolutionary
status of KKR25, which belongs to a rare class of very isolated dwarf galaxies
with spheroidal morphology.Comment: Accepted to MNRAS. 11 figures, 7 table
First year of energetic particle measurements in the inner heliosphere with Solar Orbiter's Energetic Particle Detector
Context. Solar Orbiter strives to unveil how the Sun controls and shapes the heliosphere and fills it with energetic particle radiation. To this end, its Energetic Particle Detector (EPD) has now been in operation, providing excellent data, for just over a year.
Aims. EPD measures suprathermal and energetic particles in the energy range from a few keV up to (near-) relativistic energies (few MeV for electrons and about 500 MeV nuc−1 for ions). We present an overview of the initial results from the first year of operations and we provide a first assessment of issues and limitations. In addition, we present areas where EPD excels and provides opportunities for significant scientific progress in understanding how our Sun shapes the heliosphere.
Methods. We used the solar particle events observed by Solar Orbiter on 21 July and between 10 and 11 December 2020 to discuss the capabilities, along with updates and open issues related to EPD on Solar Orbiter. We also give some words of caution and caveats related to the use of EPD-derived data.
Results. During this first year of operations of the Solar Orbiter mission, EPD has recorded several particle events at distances between 0.5 and 1 au from the Sun. We present dynamic and time-averaged energy spectra for ions that were measured with a combination of all four EPD sensors, namely: the SupraThermal Electron and Proton sensor (STEP), the Electron Proton Telescope (EPT), the Suprathermal Ion Spectrograph (SIS), and the High-Energy Telescope (HET) as well as the associated energy spectra for electrons measured with STEP and EPT. We illustrate the capabilities of the EPD suite using the 10 and 11 December 2020 solar particle event. This event showed an enrichment of heavy ions as well as 3He, for which we also present dynamic spectra measured with SIS. The high anisotropy of electrons at the onset of the event and its temporal evolution is also shown using data from these sensors. We discuss the ongoing in-flight calibration and a few open instrumental issues using data from the 21 July and the 10 and 11 December 2020 events and give guidelines and examples for the usage of the EPD data. We explain how spacecraft operations may affect EPD data and we present a list of such time periods in the appendix. A list of the most significant particle enhancements as observed by EPT during this first year is also provided.Ministerio de Economía y CompetitividadAgencia Estatal de Investigació
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