401 research outputs found
BCR-ABL Promotes PTEN Downregulation in Chronic Myeloid Leukemia.
Chronic myeloid leukemia (CML) is a myeloproliferative disorder characterized by the t(9;22) translocation coding for the chimeric protein p210 BCR-ABL. The tumor suppressor PTEN plays a critical role in the pathogenesis of CML chronic phase, through non genomic loss of function mechanisms, such as protein down-regulation and impaired nuclear/cytoplasmic shuttling. Here we demonstrate that BCR-ABL promotes PTEN downregulation through a MEK dependent pathway. Furthermore, we describe a novel not recurrent N212D-PTEN point mutation found in the EM2 blast crisis cell line
Non-standard grain properties, dark gas reservoir, and extended submillimeter excess, probed by Herschel in the Large Magellanic Cloud
Context. Herschel provides crucial constraints on the IR SEDs of galaxies, allowing unprecedented accuracy on the dust mass estimates. However, these estimates rely on non-linear models and poorly-known optical properties.
Aims. In this paper, we perform detailed modelling of the Spitzer and Herschel observations of the LMC, in order to: (i) systematically study the uncertainties and biases affecting dust mass estimates; and to (ii) explore the peculiar ISM properties of the LMC.
Methods. To achieve these goals, we have modelled the spatially resolved SEDs with two alternate grain compositions, to study the impact of different submillimetre opacities on the dust mass. We have rigorously propagated the observational errors (noise and calibration) through the entire fitting process, in order to derive consistent parameter uncertainties.
Results. First, we show that using the integrated SED leads to underestimating the dust mass by ≃50% compared to the value obtained with sufficient spatial resolution, for the region we studied. This might be the case, in general, for unresolved galaxies. Second, we show that Milky Way type grains produce higher gas-to-dust mass ratios than what seems possible according to the element abundances in the LMC. A spatial analysis shows that this dilemma is the result of an exceptional property: the grains of the LMC have on average a larger intrinsic submm opacity (emissivity index β ≃ 1.7 and opacity κ_(abs)(160 μm) = 1.6 m^2 kg^(-1)) than those of the Galaxy. By studying the spatial distribution of the gas-to-dust mass ratio, we are able to constrain the fraction of unseen gas mass between ≃10, and ≃100% and show that it is not sufficient to explain the gas-to-dust mass ratio obtained with Milky Way type grains. Finally, we confirm the detection of a 500 μm extended emission excess with an average relative amplitude of ≃15%, varying up to 40%. This excess anticorrelates well with the dust mass surface density. Although we do not know the origin of this excess, we show that it is unlikely the result of very cold dust, or CMB fluctuations
The effects of star formation on the low-metallicity ISM: NGC4214 mapped with Herschel/PACS spectroscopy
We present Herschel/PACS spectroscopic maps of the dwarf galaxy NC4214
observed in 6 far infrared fine-structure lines: [C II] 158mu, [O III] 88mu, [O
I] 63mu, [O I] 146mu, [N II] 122mu, and [N II] 205mu. The maps are sampled to
the full telescope spatial resolution and reveal unprecedented detail on ~ 150
pc size scales. We detect [C II] emission over the whole mapped area, [O III]
being the most luminous FIR line. The ratio of [O III]/[C II] peaks at about 2
toward the sites of massive star formation, higher than ratios seen in dusty
starburst galaxies. The [C II]/CO ratios are 20 000 to 70 000 toward the 2
massive clusters, which are at least an order of magnitude larger than spiral
or dusty starbursts, and cannot be reconciled with single-slab PDR models.
Toward the 2 massive star-forming regions, we find that L[CII] is 0.5 to 0.8%
of the LTIR . All of the lines together contribute up to 2% of LTIR . These
extreme findings are a consequence of the lower metallicity and young,
massive-star formation commonly found in dwarf galaxies. These conditions
promote large-scale photodissociation into the molecular reservoir, which is
evident in the FIR line ratios. This illustrates the necessity to move to
multiphase models applicable to star-forming clusters or galaxies as a whole.Comment: Accepted for publication in the A&A Herschel Special Issu
The Spitzer discovery of a galaxy with infrared emission solely due to AGN activity
We present a galaxy (SAGE1CJ053634.78-722658.5) at a redshift of 0.14 of
which the IR is entirely dominated by emission associated with the AGN. We
present the 5-37 um Spitzer/IRS spectrum and broad wavelength SED of
SAGE1CJ053634, an IR point-source detected by Spitzer/SAGE (Meixner et al
2006). The source was observed in the SAGE-Spec program (Kemper et al., 2010)
and was included to determine the nature of sources with deviant IR colours.
The spectrum shows a redshifted (z=0.14+-0.005) silicate emission feature with
an exceptionally high feature-to-continuum ratio and weak polycyclic aromatic
hydrocarbon (PAH) bands. We compare the source with models of emission from
dusty tori around AGNs from Nenkova et al. (2008). We present a diagnostic
diagram that will help to identify similar sources based on Spitzer/MIPS and
Herschel/PACS photometry. The SED of SAGE1CJ053634 is peculiar because it lacks
far-IR emission and a clear stellar counterpart. We find that the SED and the
IR spectrum can be understood as emission originating from the inner ~10 pc
around an accreting black hole. There is no need to invoke emission from the
host galaxy, either from the stars or from the interstellar medium, although a
possible early-type host galaxy cannot be excluded based on the SED analysis.
The hot dust around the accretion disk gives rise to a continuum, which peaks
at 4 um, whereas the strong silicate features may arise from optically thin
emission of dusty clouds within ~10 pc around the black hole. The weak PAH
emission does not appear to be linked to star formation, as star formation
templates strongly over-predict the measured far-IR flux levels. The SED of
SAGE1CJ053634 is rare in the local universe but may be more common in the more
distant universe. The conspicuous absence of host-galaxy IR emission places
limits on the far-IR emission arising from the dusty torus alone.Comment: Accepted for publication in A&A, 7 pages, 6 figure
Gaia on-board metrology: basic angle and best focus
The Gaia payload ensures maximum passive stability using a single material,
SiC, for most of its elements. Dedicated metrology instruments are, however,
required to carry out two functions: monitoring the basic angle and refocusing
the telescope. Two interferometers fed by the same laser are used to measure
the basic angle changes at the level of as (prad, micropixel), which is
the highest level ever achieved in space. Two Shack-Hartmann wavefront sensors,
combined with an ad-hoc analysis of the scientific data are used to define and
reach the overall best-focus. In this contribution, the systems, data analysis,
procedures and performance achieved during commissioning are presentedComment: 18 pages, 14 figures. To appear in SPIE proceedings 9143-30. Space
Telescopes and Instrumentation 2014: Optical, Infrared, and Millimeter Wav
Herschel Observations of a Newly Discovered UX Ori Star in the Large Magellanic Cloud
The LMC star, SSTISAGE1C J050756.44-703453.9, was first noticed during a
survey of EROS-2 lightcurves for stars with large irregular brightness
variations typical of the R Coronae Borealis (RCB) class. However, the visible
spectrum showing emission lines including the Balmer and Paschen series as well
as many Fe II lines is emphatically not that of an RCB star. This star has all
of the characteristics of a typical UX Ori star. It has a spectral type of
approximately A2 and has excited an H II region in its vicinity. However, if it
is an LMC member, then it is very luminous for a Herbig Ae/Be star. It shows
irregular drops in brightness of up to 2 mag, and displays the reddening and
"blueing" typical of this class of stars. Its spectrum, showing a combination
of emission and absorption lines, is typical of a UX Ori star that is in a
decline caused by obscuration from the circumstellar dust. SSTISAGE1C
J050756.44-703453.9 has a strong IR excess and significant emission is present
out to 500 micron. Monte Carlo radiative transfer modeling of the SED requires
that SSTISAGE1C J050756.44-703453.9 has both a dusty disk as well as a large
extended diffuse envelope to fit both the mid- and far-IR dust emission. This
star is a new member of the UX Ori subclass of the Herbig Ae/Be stars and only
the second such star to be discovered in the LMC.Comment: ApJ, in press. 9 pages, 5 figure
Dust in the bright supernova remnant N49 in the LMC
We investigate the dust associated with the supernova remnant (SNR) N49 in
the Large Magellanic Cloud (LMC) as observed with the Herschel Space
Observatory. N49 is unusually bright because of an interaction with a molecular
cloud along its eastern edge. We have used PACS and SPIRE to measure the far IR
flux densities of the entire SNR and of a bright region on the eastern edge of
the SNR where the SNR shock is encountering the molecular cloud. Using these
fluxes supplemented with archival data at shorter wavelengths, we estimate the
dust mass associated with N49 to be about 10 Msun. The bulk of the dust in our
simple two-component model has a temperature of 20-30 K, similar to that of
nearby molecular clouds. Unfortunately, as a result of the limited angular
resolution of Herschel at the wavelengths sampled with SPIRE, the uncertainties
are fairly large. Assuming this estimate of the dust mass associated with the
SNR is approximately correct, it is probable that most of the dust in the SNR
arises from regions where the shock speed is too low to produce significant
X-ray emission. The total amount of warm 50-60 K dust is ~0.1 or 0.4 Msun,
depending on whether the dust is modeled in terms of carbonaceous or silicate
grains. This provides a firm lower limit to the amount of shock heated dust in
N49.Comment: accepted by the Astronomy & Astrophysics Lette
The Herschel Reference Survey: Dust in Early-Type Galaxies and Across the Hubble Sequence
We present Herschel observations of 62 Early-Type Galaxies (ETGs), including
39 galaxies morphologically classified as S0+S0a and 23 galaxies classified as
ellipticals using SPIRE at 250, 350 and 500 microns (and PACS 100 and 160
microns for 19 sources) as part of the volume-limited Herschel Reference
Survey. We detect dust emission in 24% of the ellipticals and 62% of the S0s.
The mean temperature of the dust is 23.9+/-0.8 K, warmer than that found for
late-type galaxies in the Virgo Cluster. Including the non-detections, the mean
dust mass is log(Mdust) = 5.9+/-0.1 and 5.2+/-0.1 Msun for the S0s and
elliptical galaxies respectively. The mean dust-to-stellar mass is
log(Mdust/Mstar) = -4.4+/-0.1 (S0s) and -5.8+/-0.1 (ellipticals). Virtually all
the galaxies lie close to the red sequence yet the large number of detections
of cool dust, the gas-to-dust ratios and the ratios of far-infrared to radio
emission all suggest that many ETGs contain a cool interstellar medium similar
to that in late-type galaxies. The mean dust-to-stellar mass ratio for S0s is
approximatly a factor of ten less than for early-type spirals and the sizes of
the dust sources in the S0s are also much smaller. We show that the difference
cannot be explained by either the different bulge-to-disk ratios or
environmental effects such as ram-pressure stripping. The wide range in the
dust-to-stellar mass ratio for ETGs and the lack of a correlation between dust
mass and optical luminosity suggest that much of the dust in the ETGs detected
by Herschel has been acquired as the result of gravitational interactions;
these interactions are unlikely to have had a major effect on the stellar
masses of the ETGs. The Herschel observations tentatively suggest that in the
most massive ETGs, the mass of the interstellar medium is unconnected to the
evolution of the stellar populations.Comment: 28 Pages, 12 Figures. Submitted to ApJ December 2011; accepted
January 201
IRAS F02044+0957: radio source in interacting system of galaxies
The steep spectrum of IRAS F02044+0957 was obtained with the RATAN-600 radio
telescope at four frequencies. Optical spectroscopy of the system components,
was carried out with the 2.1m telescope of the Guillermo Haro Observatory.
Observational data allow us to conclude that this object is a pair of
interacting galaxies, a LINER and a HII galaxy, at .Comment: 2 pages, 2 EPS-figures, uses newpasp.sty. To appear in Proc. IAU
Colloq. 184, AGN Surveys, ed. R. F. Green, E. Ye. Khachikian, & D. B. Sanders
(San Francisco: ASP
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