271 research outputs found
A Keplerian gaseous disk around the B0 star R Mon
We present high-angular resolution observations of the circumstellar disk
around the massive Herbig Be star R Mon (M~8 Msun) in the continuum at 2.7mm
and 1.3mm and the CO 1->0 and 2->1 rotational lines. Based on the new 1.3mm
continuum image we estimate a disk mass (gas+dust) of 0.007 Msun and an outer
radius of <150 AU. Our CO images are consistent with the existence of a
Keplerian rotating gaseous disk around this star. Up to our knowledge, this is
the most clear evidence for the existence of Keplerian disks around massive
stars reported thus far. The mass and physical characteristics of this disk are
similar to thoseof the more evolved T Tauri stars and indicate a shorter
timescale for the evolution and dispersal of circumstellar disks around massive
stars which lose most of their mass before the star becomes visible.Comment: 5 page
Protostellar clusters in intermediate-mass (IM) star forming regions
The transition between the low density groups of T Tauri stars and the high
density clusters around massive stars occurs in the intermediate-mass (IM)
range (M2--8 M). High spatial resolution studies of IM young
stellar objects (YSO) can provide important clues to understand the clustering
in massive star forming regions.
Aims: Our aim is to search for clustering in IM Class 0 protostars. The high
spatial resolution and sensitivity provided by the new A configuration of the
Plateau de Bure Interferometer (PdBI) allow us to study the clustering in these
nearby objects.
Methods: We have imaged three IM Class 0 protostars (Serpens-FIRS 1, IC 1396
N, CB 3) in the continuum at 3.3 and 1.3mm using the PdBI. The sources have
been selected with different luminosity to investigate the dependence of the
clustering process on the luminosity of the source.
Results: Only one millimeter (mm) source is detected towards the low
luminosity source Serpens--FIRS 1. Towards CB 3 and IC1396 N, we detect two
compact sources separated by 0.05 pc. The 1.3mm image of IC 1396 N, which
provides the highest spatial resolution, reveal that one of these cores is
splitted in, at least, three individual sources.Comment: 4 pages, 3 figures, accepted for publication in Astronomy and
Astrophysics Letters (Special Feature IRAM/PdB
Dissecting an intermediate-mass (IM) protostar: Chemical differentiation in IC1396N
We have carried out high-angular resolution (1.4") observations in the
continuum at 3.1mm and in the N2H+ 1-0, CH3CN 5_k-4_k and 13CS 2-1 lines using
the Plateau de Bure Interferometer (PdBI) towards the intermediate mass (IM)
protostar IRAS21391+5802 (IC1396N). In addition, we have merged the PdBI images
with previous BIMA (continuum data at 1.2mm and 3.1mm) and single-dish (N2H+
1-0) data to have a comprehensive description of the region. The combination of
our data with BIMA and 30m data show that the bipolar outflow associated has
completely eroded the initial molecular globule. The 1.2mm and 3.1mm continuum
emissions are extended along the outflow axis tracing the warm walls of the
biconical cavity. Most of the molecular gas, however, is located in an
elongated feature in the direction perpendicular to the outflow. A strong
chemical differentiation is detected across the molecular toroid, with the N2H+
1-0 emission absent in the inner region.This chemical differentiation can be
understood in terms of the different gas kinetic temperature. The
[CH3CN]/[N2H+] ratio increases by 5 orders of magnitude with gas temperature,
for temperatures between 20K and 100K. The CH3CN abundance towards IRAM 2A, the
most massive protostellar core, is similar to that found in hot corinos and
lower than that expected towards IM and high mass hot cores. This could
indicate that IRAM 2A is a low mass or at most Herbig Ae star (IRAM 2A) instead
of the precursor of a massive Be star. Alternatively, the low CH3CN abundance
could also be the consequence of IRAM 2A being a Class 0/I transition object
which has already formed a small photodissociation region (PDR).Comment: accepted A&
The dusty disk around VV Ser
We have carried out observations at millimeter and centimeter wavelengths
towards VV Ser using the Plateau de Bure Interferometer and the Very Large
Array. This allows us to compute the SED from near infrared to centimeter
wavelengths. The modeling of the full SED has provided insight into the dust
properties and a more accurate value of the disk mass.
The mass of dust in the disk around VV Ser is found to be about 4 10^(-5)
Msun, i.e. 400 times larger than previous estimates. Moreoever, the SED can
only be accounted for assuming dust stratification in the vertical direction
across the disk. The existence of small grains (0.25--1 micron) in the disk
surface is required to explain the emission at near- and mid-infrared
wavelengths. The fluxes measured at millimeter wavelengths imply that the dust
grains in the midplane have grown up to very large sizes, at least to some
centimeters.Comment: To appear in Ap
The abundance of C18O and HDO in the envelope and hot core of the intermediate mass protostar NGC 7129 FIRS 2
NGC 7129 FIRS 2 is a young intermediate-mass (IM) protostar, which is
associated with two energetic bipolar outflows and displays clear signs of the
presence of a hot core. It has been extensively observed with ground based
telescopes and within the WISH Guaranteed Time Herschel Key Program. We present
new observations of the C18O 3-2 and the HDO 3_{12}-2_{21} lines towards NGC
7129 FIRS 2. Combining these observations with Herschel data and modeling their
emissions, we constrain the C18O and HDO abundance profiles across the
protostellar envelope. In particular, we derive the abundance of C18O and HDO
in the hot core. The intensities of the C18O lines are well reproduced assuming
that the C18O abundance decreases through the protostellar envelope from the
outer edge towards the centre until the point where the gas and dust reach the
CO evaporation temperature (~20-25 K) where the C18O is released back to the
gas phase. Once the C18O is released to the gas phase, the modelled C18O
abundance is found to be ~1.6x10^{-8}, which is a factor of 10 lower than the
reference abundance. This result is supported by the non-detection of C18O 9-8,
which proves that even in the hot core (T_k>100 K) the CO abundance must be 10
times lower than the reference value. Several scenarios are discussed to
explain this C18O deficiency. One possible explanation is that during the
pre-stellar and protostellar phase, the CO is removed from the grain mantles by
reactions to form more complex molecules. Our HDO modeling shows that the
emission of HDO 3_{12}-2_{21} line is maser and comes from the hot core
(T_k>100 K). Assuming the physical structure derived by Crimier et al. (2010),
we determine a HDO abundance of ~0.4 - 1x10^{-7} in the hot core of this IM
protostar, similar to that found in the hot corinos NGC 1333 IRAS 2A and IRAS
16293-2422.Comment: 10 pages, 7 figure
Spectral line survey of the ultracompact HII region Mon R2
Ultracompact (UC) HII regions constitute one of the earliest phases in the
formation of a massive star and are characterized by extreme physical
conditions (Go>10^5 Habing field and n>10^6 cm^-3). The UC HII Mon R2 is the
closest one and therefore an excellent target to study the chemistry in these
complex regions.
We carried out a 3mm and 1mm spectral survey using the IRAM 30-m telescope
towards three positions that represent different physical environments in Mon
R2: (i) the ionization front (IF) at (0",0"); two peaks in the molecular cloud
(ii) MP1 at the offset (+15",-15") and (iii) MP2 at the farther offset
(0",40"). In addition, we carried out extensive modeling to explain the
chemical differences between the three observed regions.
We detected more than thirty different species. We detected SO+ and C4H
suggesting that UV radiation plays an important role in the molecular chemistry
of this region. We detected the typical PDR molecules CN, HCN, HCO, C2H, and
c-C3H2. While the IF and the MP1 have a chemistry similar to that found in high
UV field and dense PDRs like the Orion Bar, the MP2 is more similar to lower
UV/density PDRs like the Horsehead nebula.
We also detected complex molecules that are not usually found in PDRs (CH3CN,
H2CO, HC3N, CH3OH and CH3C2H). Sulfur compounds CS, HCS+, C2S, H2CS, SO and SO2
and the deuterated species DCN and C2D were also identified. [DCN]/[HCN]=0.03
and [C2D]/[C2H]=0.05, are among the highest in warm regions.
Our results show that the high UV/dense PDRs present a different chemistry
from that of the low UV case. Abundance ratios like [CO+]/[HCO+] or
[HCO]/[HCO+] are good diagnostics to differentiate between them. In Mon R2 we
have the two classes of PDRs, a high UV PDR towards the IF and the adjacent
molecular bar and a low-UV PDR which extends towards the north-west following
the border of the cloud.Comment: 31 page
Nanoparticles engineered to bind cellular motors for efficient delivery
Background: Dynein is a cytoskeletal molecular motor protein that transports cellular cargoes along microtubules. Biomimetic synthetic peptides designed to bind dynein have been shown to acquire dynamic properties such as cell accumulation and active intra- and inter-cellular motion through cell-to-cell contacts and projections to distant cells. On the basis of these properties dynein-binding peptides could be used to functionalize nanoparticles for drug delivery applications. Results: Here, we show that gold nanoparticles modified with dynein-binding delivery sequences become mobile, powered by molecular motor proteins. Modified nanoparticles showed dynamic properties, such as travelling the cytosol, crossing intracellular barriers and shuttling the nuclear membrane. Furthermore, nanoparticles were transported from one cell to another through cell-to-cell contacts and quickly spread to distant cells through cell projections. Conclusions: The capacity of these motor-bound nanoparticles to spread to many cells and increasing cellular retention, thus avoiding losses and allowing lower dosage, could make them candidate carriers for drug delivery
UV femtosecond laser cleaning of encrusted historical stained-glasses
Laser irradiation enables the removal of unwanted surface deposits from different materials in a safe and controllable manner. Laser parameters should be carefully selected to achieve the removal of the target contaminants without inducing damage to the substrate. Ultra-short pulse lasers have opened new opportunities for safe and controlled decontamination of cultural heritage materials because the thickness of material that is affected by the laser is limited. In this study, an ultraviolet femtosecond pulsed laser was used for the removal of unwanted encrustation formed on the surface of an historical colourless stained-glass sample from the Cuenca Cathedral in Spain. One of the sides of this glass exhibits a reddish-brown grisaille that also has to be preserved. A laser cleaning process has been designed to avoid heat accumulation while controlling the thickness of ablated material. In this context, a multi-step process was selected in order to be able to eliminate, in a controlled way, the crust layer without damaging the grisaille layer, or the glass substrate. In this case, laser irradiation in beam scanning mode with a pulse repetition frequency of 10 kHz proved to be effective for the safe cleaning of the glass. The latter was analysed before and after laser cleaning by optical and confocal microscopy, scanning electron microscopy, energy dispersive X-ray spectroscopy, X-ray fluorescence, and Raman spectroscopy, confirming that the crust layer was effectively eliminated without damaging the surface
ALMA resolves the torus of NGC 1068: continuum and molecular line emission
We have used the Atacama Large Millimeter Array (ALMA) to map the emission of
the CO(6-5) molecular line and the 432 {\mu}m continuum emission from the 300
pc-sized circumnuclear disk (CND) of the nearby Seyfert 2 galaxy NGC 1068 with
a spatial resolution of ~4 pc. These observations spatially resolve the CND
and, for the first time, image the dust emission, the molecular gas
distribution, and the kinematics from a 7-10 pc-diameter disk that represents
the submillimeter counterpart of the putative torus of NGC 1068. We fitted the
nuclear spectral energy distribution of the torus using ALMA and near and
mid-infrared (NIR/MIR) data with CLUMPY models. The mass and radius of the
best-fit solution for the torus are both consistent with the values derived
from the ALMA data alone: Mgas_torus=(1+-0.3)x10^5 Msun and Rtorus=3.5+-0.5 pc.
The dynamics of the molecular gas in the torus show non-circular motions and
enhanced turbulence superposed on the rotating pattern of the disk. The
kinematic major axis of the CO torus is tilted relative to its morphological
major axis. By contrast with the nearly edge-on orientation of the H2O
megamaser disk, we have found evidence suggesting that the molecular torus is
less inclined (i=34deg-66deg) at larger radii. The lopsided morphology and
complex kinematics of the torus could be the signature of the
Papaloizou-Pringle instability, long predicted to likely drive the dynamical
evolution of active galactic nuclei (AGN) tori.Comment: Final version accepted by the Astrophysical Journal Letters
(ApJLetters) on April 27th 2016, 6 pages, 5 figure
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