164 research outputs found
Gemini/GMOS Imaging of Globular Cluster Systems in Five Early-type Galaxies
This paper presents deep high quality photometry of globular cluster (GC)
systems belonging to five early-type galaxies covering a range of mass and
environment. Photometric data were obtained with the Gemini North and Gemini
South telescopes in the filter passbands g', r', and i'. The combination of
these filters with good seeing conditions allows an excellent separation
between GC candidates and unresolved field objects. Bimodal GC colour
distributions are found in all five galaxies. Most of the GC systems appear
bimodal even in the (g' -r') vs (r' -i') plane. A population of
resolved/marginally resolved GC and Ultra Compact Dwarf candidates was found in
all the galaxies. A search for the so-called "blue tilt" in the
colour-magnitude diagrams reveals that NGC 4649 clearly shows that phenomenon
although no conclusive evidence was found for the other galaxies in the sample.
This "blue tilt" translates into a mass-metallicity relation given by Z \propto
M^0.28\pm0.03 . This dependence was found using a new empirical (g' -i') vs
[Z/H] relation which relies on an homogeneous sample of GC colours and
metallicities. This paper also explores the radial trends in both colour and
surface density for the blue (metal-poor) and red (metal-rich) GC
subpopulations. As usual, the red GCs show a steeper radial distribution than
the blue ones. Evidence of galactocentric colour gradients is found in some of
the GC systems, being more significant for the two S0 galaxies in the sample.
Red GC subpopulations show similar colours and gradients to the galaxy halo
stars in their inner region. A GC mean colour-galaxy luminosity relation,
consistent with [Z/H] \propto L_B ^0.26\pm0.08, is present for the red GCs. An
estimate of the total GC populations and specific frequency SN values is
presented for NGC 3115, NGC 3379, NGC 3923 and NGC 4649.Comment: 23 pages, 13 figures and 9 tables. Tables A1 and A2 will be published
in full online only. Accepted for publication in MNRA
Acute liver toxicity with ifosfamide in the treatment of sarcoma: a case report
<p>Abstract</p> <p>Introduction</p> <p>Ifosfamide is a chemotherapy agent infrequently associated with liver toxicity. To the best of our knowledge, this report is the first to describe serious liver toxicity associated with ifosfamide used in combination with doxorubicin that caused acute but fully reversible liver failure and encephalopathy. This report reviews the possible mechanisms by which ifosfamide causes this adverse effect.</p> <p>Case report</p> <p>A 61-year-old Caucasian woman who presented with an inoperable right neck mass due to synovial sarcoma was treated with standard-dose ifosfamide and doxorubicin. Within 24 hours of completing the first cycle of chemotherapy, she developed significant derangements in liver function, with a 250-fold increase in transaminase and associated synthetic function impairment and encephalopathy. No other causes of liver failure were identified. Both biochemical tests and encephalopathy were reversed after supportive management and treatment with <it>N</it>-acetylcysteine. No liver toxicity was observed with subsequent cycles of chemotherapy with doxorubicin alone.</p> <p>Conclusion</p> <p>This case highlights the possibility that chemotherapy agents can cause rare and idiosyncratic toxicities, so physicians must be vigilant for drug reactions, especially when patients do not respond to usual treatment.</p
Acute liver toxicity with ifosfamide in the treatment of sarcoma: a case report
<p>Abstract</p> <p>Introduction</p> <p>Ifosfamide is a chemotherapy agent infrequently associated with liver toxicity. To the best of our knowledge, this report is the first to describe serious liver toxicity associated with ifosfamide used in combination with doxorubicin that caused acute but fully reversible liver failure and encephalopathy. This report reviews the possible mechanisms by which ifosfamide causes this adverse effect.</p> <p>Case report</p> <p>A 61-year-old Caucasian woman who presented with an inoperable right neck mass due to synovial sarcoma was treated with standard-dose ifosfamide and doxorubicin. Within 24 hours of completing the first cycle of chemotherapy, she developed significant derangements in liver function, with a 250-fold increase in transaminase and associated synthetic function impairment and encephalopathy. No other causes of liver failure were identified. Both biochemical tests and encephalopathy were reversed after supportive management and treatment with <it>N</it>-acetylcysteine. No liver toxicity was observed with subsequent cycles of chemotherapy with doxorubicin alone.</p> <p>Conclusion</p> <p>This case highlights the possibility that chemotherapy agents can cause rare and idiosyncratic toxicities, so physicians must be vigilant for drug reactions, especially when patients do not respond to usual treatment.</p
Tracking seabird migration in the tropical Indian Ocean reveals basin-scale conservation need
Summary
Understanding marine predator distributions is an essential component of arresting their catastrophic declines.1,2,3,4 In temperate, polar, and upwelling seas, predictable oceanographic features can aggregate migratory predators, which benefit from site-based protection.5,6,7,8 In more oligotrophic tropical waters, however, it is unclear whether environmental conditions create similar multi-species hotspots. We track the non-breeding movements and habitat preferences of a tropical seabird assemblage (n = 348 individuals, 9 species, and 10 colonies in the western Indian Ocean), which supports globally important biodiversity.9,10,11,12 We mapped species richness from tracked populations and then predicted the same diversity measure for all known Indian Ocean colonies. Most species had large non-breeding ranges, low or variable residency patterns, and specific habitat preferences. This in turn revealed that maximum species richness covered >3.9 million km2, with no focused aggregations, in stark contrast to large-scale tracking studies in all other ocean basins.5,6,7,13,14 High species richness was captured by existing marine protected areas (MPAs) in the region; however, most occurred in the unprotected high seas beyond national jurisdictions. Seabirds experience cumulative anthropogenic impacts13 and high mortality15,16 during non-breeding. Therefore, our results suggest that seabird conservation in the tropical Indian Ocean requires an ocean-wide perspective, including high seas legislation.17 As restoration actions improve the outlook for tropical seabirds on land18,19,20,21,22 and environmental change reshapes the habitats that support them at sea,15,16 appropriate marine conservation will be crucial for their long-term recovery and whole ecosystem restoration
Galactic Models and White Dwarf Populations
We make use of a previous well tested Galactic model, but describing the
observational behavior of the various stellar components in terms of suitable
assumptions on their evolutionary status. In this way we are able to predict
the expected distribution of Galactic White Dwarfs (WDs), with results which
appear in {\em rather good} agreement with recent estimates of the local WD
luminosity function. The predicted occurrence of WDs in deep observations of
selected galactic fields is presented, discussing the role played by WDs in
star counts. The effects on the theoretical predictions of different White
Dwarfs evolutionary models, ages, initial mass functions and relations between
progenitor mass and WD mass are also discussed.Comment: 9 pages with 11 eps fig
The non-peculiar velocity dispersion profile of the stellar system omega Centauri
We present the results of a survey of radial velocities over a wide region
extending from r~10 arcmin out to r~80 arcmin (~1.5 tidal radii) within the
massive star cluster omega Centauri. The survey was performed with FLAMES@VLT,
to study the velocity dispersion profile in the outer regions of this stellar
system. We derived accurate radial velocities for a sample of 2557 newly
observed stars, identifying 318 bona-fide cluster red giants. Merging our data
with those provided by Pancino et al. (2007), we assembled a final homogeneous
sample of 946 cluster members that allowed us to trace the velocity dispersion
profile from the center out to r~32 arcmin. The velocity dispersion appears to
decrease monotonically over this range, from a central value of sigma_{v}~17.2
Km/s down to a minimum value of sigma_{v}~5.2 Km/s. The observed surface
brightness profile, rotation curve, velocity dispersion profile and ellipticity
profile are simultaneously well reproduced by a simple dynamical model in which
mass follows light, within the classical Newtonian theory of gravitation. The
comparison with an N-body model of the evolution of a system mimicking omega
Cen during the last 10 orbits into the Galactic potential suggests that (a) the
rotation of stars lying in the inner ~20 arcmin of the clusters is not due to
the effects of the tidal field of the Milky Way, as hypothized by other
authors, and (b) the overall observational scenario is still compatible with
the possibility that the outer regions of the cluster are subject to some tidal
stirring.Comment: 12 pages, 12 figures, accepted for publication by MNRA
A primordial star in the heart of the Lion
Context: The discovery and chemical analysis of extremely metal-poor stars
permit a better understanding of the star formation of the first generation of
stars and of the Universe emerging from the Big Bang. aims: We report the study
of a primordial star situated in the centre of the constellation Leo (SDSS
J102915+172027). method: The star, selected from the low resolution-spectrum of
the Sloan Digital Sky Survey, was observed at intermediate (with X-Shooter at
VLT) and at high spectral resolution (with UVES at VLT). The stellar parameters
were derived from the photometry. The standard spectroscopic analysis based on
1D ATLAS models was completed by applying 3D and non-LTE corrections. results:
An iron abundance of [Fe/H]=--4.89 makes SDSS J102915+172927 one of the lowest
[Fe/H] stars known. However, the absence of measurable C and N enhancements
indicates that it has the lowest metallicity, Z<= 7.40x10^{-7} (metal-mass
fraction), ever detected. No oxygen measurement was possible. conclusions: The
discovery of SDSS J102915+172927 highlights that low-mass star formation
occurred at metallicities lower than previously assumed. Even lower metallicity
stars may yet be discovered, with a chemical composition closer to the
composition of the primordial gas and of the first supernovae.Comment: To be published in A&
Structure and Kinematics of the Stellar Halos and Thick Disks of the Milky Way Based on Calibration Stars from SDSS DR7
The structure and kinematics of the recognized stellar components of the
Milky Way are explored, based on well-determined atmospheric parameters and
kinematic quantities for 32360 calibration stars from the Sloan Digital Sky
Survey (SDSS) and its first extension, (SDSS-II), which included the sub-survey
SEGUE: Sloan Extension for Galactic Understanding and Exploration. Full space
motions for a sub-sample of 16920 stars, exploring a local volume within 4 kpc
of the Sun, are used to derive velocity ellipsoids for the inner- and
outer-halo components of the Galaxy, as well as for the canonical thick-disk
and proposed metal-weak thick-disk populations. We first examine the question
of whether the data require the presence of at least a two-component halo in
order to account for the rotational behavior of likely halo stars in the local
volume, and whether more than two components are needed. We also address the
question of whether the proposed metal-weak thick disk is kinematically and
chemically distinct from the canonical thick disk. In addition, we consider the
fractions of each component required to understand the nature of the observed
kinematic behavior of the stellar populations of the Galaxy as a function of
distance from the plane. Scale lengths and scale heights for the thick-disk and
metal-weak thick-disk components are determined. Spatial density profiles for
the inner- and outer-halo populations are inferred from a Jeans Theorem
analysis. The full set of calibration stars (including those outside the local
volume) is used to test for the expected changes in the observed stellar
metallicity distribution function with distance above the Galactic plane
in-situ, due to the changing contributions from the underlying stellar
populations. [abridged]Comment: Accepted for publication in the Ap
Gaia Universe Model Snapshot : A statistical analysis of the expected contents of the Gaia catalogue
Context. This study has been developed in the framework of the computational
simulations executed for the preparation of the ESA Gaia astrometric mission.
Aims. We focus on describing the objects and characteristics that Gaia will
potentially observe without taking into consideration instrumental effects
(detection efficiency, observing errors). Methods. The theoretical Universe
Model prepared for the Gaia simulation has been statistically analyzed at a
given time. Ingredients of the model are described, giving most attention to
the stellar content, the double and multiple stars, and variability. Results.
In this simulation the errors have not been included yet. Hence we estimate the
number of objects and their theoretical photometric, astrometric and
spectroscopic characteristics in the case that they are perfectly detected. We
show that Gaia will be able to potentially observe 1.1 billion of stars (single
or part of multiple star systems) of which about 2% are variable stars, 3% have
one or two exoplanets. At the extragalactic level, observations will be
potentially composed by several millions of galaxies, half million to 1 million
of quasars and about 50,000 supernovas that will occur during the 5 years of
mission. The simulated catalogue will be made publicly available by the DPAC on
the Gaia portal of the ESA web site http://www.rssd.esa.int/gaia/.Comment: 21 pages, 21 figures, accepted for publication in Astronomy and
Astrophysics, typos corrected in author name
The calibration of the RGB Tip as a Standard Candle: Extension to Near Infrared colors and higher metallicity
New empirical calibrations of the Red Giant Branch Tip in the I,J,H and K
bands based on two fundamental pillars, namely omega Centauri and 47 Tucanae,
have been obtained by using a large optical and near infrared photometric
database. Our best estimates give M_I(TRGB)= -4.05 pm 0.12, M_J(TRGB)= -5.20 pm
0.16, M_H(TRGB)= -5.94 pm 0.18 and M_K(TRGB) = -6.04 pm 0.16 at [M/H]=-1.5
(omega Cen) and M_I(TRGB)= -3.91 pm 0.13, M_J(TRGB)= -5.47 pm 0.25, M_H(TRGB)=
-6.35 pm 0.30 and M_K(TRGB)= -6.56 pm 0.20 at [M/H]=-0.6 (47 Tuc). With these
new empirical calibrations we also provide robust relations of the TRGB
magnitude in I, J, H and K bands as a function of the global metallicity
([M/H]). It has also been shown that our calibrations self-consistently provide
a distance modulus of the Large Magellanic Cloud in good agreement with the
standard value ((m-M)_0 = 18.50)).Comment: A&A latex, 14 pages, 7 .ps figures (fig. 1 and fig. 3 provided in low
resolution version). Accepted by Astronomy & Astrophysics Correction of a
typographical error in Fig. 7; M_I vs [M/H] relatio
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