359 research outputs found
Proper Motions in Kapteyn Selected Area 103: A Preliminary Orbit for the Virgo Stellar Stream
We present absolute proper motions in Kapteyn Selected Area (SA) 103. This
field is located 7 degrees west of the center of the Virgo Stellar Stream (VSS,
Duffau et al. 2006), and has a well-defined main sequence representing the
stream. In SA 103 we identify one RR Lyrae star as a member of the VSS
according to its metallicity, radial velocity and distance. VSS candidate
turnoff stars and subgiant stars have proper motions consistent with that of
the RR Lyrae star. The 3D velocity data imply an orbit with a pericenter of 11
kpc and an apocenter of ~90 kpc. Thus, the VSS comprises tidal debris found
near the pericenter of a highly destructive orbit. Examining the six globular
clusters at distances larger than 50 kpc from the Galactic center, and the
proposed orbit of the VSS, we find one tentative association, NGC 2419. We
speculate that NGC 2419 is possibly the nucleus of a disrupted system of which
the VSS is a part.Comment: ApJL accepte
Management of Low-Grade Glioma
The optimal management of patients with low-grade glioma (LGG) is controversial. The controversy largely stems from the lack of well-designed clinical trials with adequate follow-up to account for the relatively long progression-free survival and overall survival of patients with LGG. Nonetheless, the literature increasingly suggests that expectant management is no longer optimal. Rather, there is mounting evidence supporting active management including consideration of surgical resection, radiotherapy, chemotherapy, molecular and histopathologic characterization, and use of modern imaging techniques for monitoring and prognostication. In particular, there is growing evidence favoring extensive surgical resection and increasing interest in the role of chemotherapy (especially temozolomide) in the management of these tumors. In this review, we critically analyze emerging trends in the literature with respect to management of LGG, with particular emphasis on reports published during the past year
Stellar Population Variations in the Milky Way's Stellar Halo
If the stellar halos of disk galaxies are built up from the disruption of
dwarf galaxies, models predict highly structured variations in the stellar
populations within these halos. We test this prediction by studying the ratio
of blue horizontal branch stars (BHB stars; more abundant in old, metal-poor
populations) to main-sequence turn-off stars (MSTO stars; a feature of all
populations) in the stellar halo of the Milky Way using data from the Sloan
Digital Sky Survey. We develop and apply an improved technique to select BHB
stars using ugr color information alone, yielding a sample of ~9000 g<18
candidates where ~70% of them are BHB stars. We map the BHB/MSTO ratio across
~1/4 of the sky at the distance resolution permitted by the absolute magnitude
distribution of MSTO stars. We find large variations of BHB/MSTO star ratio in
the stellar halo. Previously identified, stream-like halo structures have
distinctive BHB/MSTO ratios, indicating different ages/metallicities. Some halo
features, e.g., the low-latitude structure, appear to be almost completely
devoid of BHB stars, whereas other structures appear to be rich in BHB stars.
The Sagittarius tidal stream shows an apparent variation in BHB/MSTO ratio
along its extent, which we interpret in terms of population gradients within
the progenitor dwarf galaxy. Our detection of coherent stellar population
variations between different stellar halo substructures provides yet more
support to cosmologically motivated models for stellar halo growth.Comment: Astronomical Journal, in press. 10 pages, 5 color figures. Much
better printed in colo
Using classical Cepheids to study the far side of the Milky Way disk: I. Spectroscopic classification and the metallicity gradient
The structure, kinematics, and chemical composition of the far side of the
Milky Way disk, beyond the bulge, are still to be revealed. Classical Cepheids
(CCs) are young and luminous standard candles. We aim to use a
well-characterized sample of these variable stars to study the present time
properties of the far side of the Galactic disk. A sample of 45 Cepheid
variable star candidates were selected from near infrared time series
photometry obtained by the VVV survey. We characterized this sample using high
quality near infrared spectra obtained with VLT/X-Shooter, deriving radial
velocities and iron abundances for all the sample Cepheids. This allowed us to
separate the CCs, which are metal rich and with kinematics consistent with the
disk rotation, from type II Cepheids (T2Cs), which are more metal poor and with
different kinematics. We estimated individual distances and extinctions using
VVV photometry and period-luminosity relations, reporting the characterization
of 30 CCs located on the far side of the Galactic disk, plus 8 T2Cs mainly
located in the bulge region, of which 10 CCs and 4 T2Cs are new discoveries.
This is the first sizeable sample of CCs in this distant region of our Galaxy
that has been spectroscopically confirmed. We use their positions, kinematics,
and metallicities to confirm that the general properties of the far disk are
similar to those of the well-studied disk on the solar side of the Galaxy. In
addition, we derive for the first time the radial metallicity gradient on the
disk's far side. Considering all the CCs with ,
we measure a gradient with a slope of and
an intercept of , which is in agreement with previous
determinations based on CCs on the near side of the disk.Comment: 16 pages, 10 figures, accepted for publication in Astronomy &
Astrophysic
The Northern wraps of the Sagittarius Stream as traced by Red Clump stars: distances, intrinsic widths and stellar densities
We trace the tidal Stream of the Sagittarius dwarf spheroidal galaxy (Sgr
dSph) using Red Clump stars from the catalog of the Sloan Digital Sky Survey -
Data Release 6, in the range 150{\deg} < RA < 220{\deg}, corresponding to the
range of orbital azimuth 220{\deg} < Lambda < 290{\deg}. Substructures along
the line of sight are identified as significant peaks in the differential star
count profiles (SCP) of candidate Red Clump stars. A proper modeling of the
SCPs allows us to obtain: (a) <10% accurate, purely differential distances with
respect to the main body of Sgr, (b) estimates of the FWHM along the line of
sight, and (c) estimates of the local density, for each detected substructure.
In the range 255{\deg} < Lambda < 290{\deg} we cleanly and continuously trace
various coherent structures that can be ascribed to the Stream, in particular:
the well known northern portion of the leading arm, running from d~43 kpc at
Lambda ~ 290{\deg} to d ~ 30 kpc at Lambda ~ 255{\deg}, and a more nearby
coherent series of detections lying at constant distance d ~ 25 kpc, that can
be identified with a wrap of the trailing arm. The latter structure, predicted
by several models of the disruption of Sgr dSph, was never traced before;
comparison with existing models indicates that the difference in distance
between these portions of the leading and trailing arms may provide a powerful
tool to discriminate between theoretical models assuming different shapes of
the Galactic potential. A further, more distant wrap in the same portion of the
sky is detected only along a couple of lines of sight.[abridged]Comment: 31 pages, 28 figures, accepted for publication in the Astrophysical
Journal, a version with figures at full resolution can be downloaded at the
following URL: http://www.bo.astro.it/SGR
The Gaia-ESO Survey : Extracting diffuse interstellar bands from cool star spectra: DIB-based interstellar medium line-of-sight structures at the kpc scale
Date of Acceptance: 05/10/2014Aims. We study how diffuse interstellar bands (DIBs) measured toward distance-distributed target stars can be used to locate dense interstellar (IS) clouds in the Galaxy and probe a line-of-sight (LOS) kinematical structure, a potentially useful tool when gaseous absorption lines are saturated or not available in the spectral range. Cool target stars are numerous enough for this purpose. Methods. We devised automated DIB-fitting methods appropriate for cool star spectra and multiple IS components. The data were fitted with a combination of a synthetic stellar spectrum, a synthetic telluric transmission, and empirical DIB profiles. The initial number of DIB components and their radial velocity were guided by HI 21 cm emission spectra, or, when available in the spectral range, IS neutral sodium absorption lines. For NaI, radial velocities of NaI lines and DIBs were maintained linked during a global simultaneous fit. In parallel, stellar distances and extinctions were estimated self-consistently by means of a 2D Bayesian method from spectroscopically-derived stellar parameters and photometric data. Results. We have analyzed Gaia-ESO Survey (GES) spectra of 225 stars that probe between ∼2 and 10 kpc long LOS in five different regions of the Milky Way. The targets are the two CoRoT fields, two open clusters (NGC 4815 and γ Vel), and the Galactic bulge. Two OGLE fields toward the bulge observed before the GES are also included (205 target stars). Depending on the observed spectral intervals, we extracted one or more of the following DIBs: λλ 6283.8, 6613.6, and 8620.4. For each field, we compared the DIB strengths with the Bayesian distances and extinctions, and the DIB Doppler velocities with the HI emission spectra. Conclusions. For all fields, the DIB strength and the target extinction are well correlated. For targets that are widely distributed in distance, marked steps in DIBs and extinction radial distance profiles match each other and broadly correspond to the expected locations of spiral arms. For all fields, the DIB velocity structure agrees with HI emission spectra, and all detected DIBs correspond to strong NaI lines. This illustrates how DIBs can be used to locate the Galactic interstellar gas and to study its kinematics at the kpc scale, as illustrated by Local and Perseus Arm DIBs that differ by ≳∼30 km s-1, in agreement with HI emission spectra. On the other hand, if most targets are located beyond the main absorber, DIBs can trace the differential reddening within the field.Peer reviewedFinal Accepted Versio
Strategies for resection of lesions in the motor area: preliminary results in 42 surgical patients
Let's Make Love: Whiteness, Cleanliness and Sexuality in the French Reception of Marilyn Monroe
Copyright © by SAGE PublicationsRichard Dyer’s seminal work on whiteness in film considers Marilyn Monroe as the epitome of an institutionally racist Hollywood system that imagines the most desirable woman to be blonde, given that blondeness is understood as a guarantee of whiteness. This article adds to other recent scholarship on Monroe that has sought to complicate this reading by examining other meanings that can be attributed to her bleached blonde hair. By closely analyzing media texts that discussed Monroe in 1950s France, this article demonstrates the way in which her performance of ideal American female sexuality was read through the prism of Monroe as icon of cleanliness and (linked) modernity. It examines the way in which Monroe’s modernity allowed her to partially escape the traditional feminine private sphere and it concludes that Monroe’s bleached blonde hair can be seen in this context as having liberatory potential
Chemotherapy and diffuse low-grade gliomas: a survey within the European Low-Grade Glioma Network.
Diffuse low-grade gliomas (DLGGs) are rare and incurable tumors. Whereas maximal safe, functional-based surgical resection is the first-line treatment, the timing and choice of further treatments (chemotherapy, radiation therapy, or combined treatments) remain controversial.
An online survey on the management of DLGG patients was sent to 28 expert centers from the European Low-Grade Glioma Network (ELGGN) in May 2015. It contained 40 specific questions addressing the modalities of use of chemotherapy in these patients.
The survey demonstrated a significant heterogeneity in practice regarding the initial management of DLGG patients and the use of chemotherapy. Interestingly, radiation therapy combined with the procarbazine, CCNU (lomustine), and vincristine regimen has not imposed itself as the gold-standard treatment after surgery, despite the results of the Radiation Therapy Oncology Group 9802 study. Temozolomide is largely used as first-line treatment after surgical resection for high-risk DLGG patients, or at progression.
The heterogeneity in the management of patients with DLGG demonstrates that many questions regarding the postoperative strategy and the use of chemotherapy remain unanswered. Our survey reveals a high recruitment potential within the ELGGN for retrospective or prospective studies to generate new data regarding these issues
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