999 research outputs found
A SCUBA survey of the NGC 2068/2071 protoclusters
We report the results of a submillimeter dust continuum survey of the
protoclusters NGC 2068 and NGC 2071 in Orion B carried out at 850 microns and
450 microns with SCUBA on JCMT. The mapped region is ~ 32' x 18' in size (~ 4
pc x 2 pc) and consists of filamentary dense cores which break up into
small-scale (~ 5000 AU) fragments, including 70 starless condensations and 5
circumstellar envelopes/disks. The starless condensations, seen on the same
spatial scales as protostellar envelopes, are likely to be gravitationally
bound and pre-stellar in nature. Their mass spectrum, ranging from ~ 0.3 Msun
to ~ 5 Msun, is reminiscent of the stellar initial mass function (IMF). Their
mass-size relation suggests that they originate from gravitationally-driven
fragmentation. We thus argue that pre-collapse cloud fragmentation plays a
major role in shaping the IMF.Comment: 6 pages, 4 figures, 1 table. Letter accepted by Astronomy &
Astrophysic
High Mass Star Formation. II. The Mass Function of Submillimeter Clumps in M17
We have mapped an approximately 5.5 by 5.5 pc portion of the M17 massive
star-forming region in both 850 and 450 micron dust continuum emission using
the Submillimeter Common-User Bolometer Array (SCUBA) on the James Clerk
Maxwell Telescope (JCMT). The maps reveal more than 100 dusty clumps with
deconvolved linear sizes of 0.05--0.2 pc and masses of 0.8--120 solar masses,
most of which are not associated with known mid-infrared point sources. Fitting
the clump mass function with a double power law gives a mean power law exponent
of alpha_high = -2.4 +/- 0.3 for the high-mass power law, consistent with the
exponent of the Salpeter stellar mass function. We show that a lognormal clump
mass distribution with a peak at about 4 solar masses produces as good a fit to
the clump mass function as does a double power law. This 4 solar mass peak mass
is well above the peak masses of both the stellar initial mass function and the
mass function of clumps in low-mass star-forming regions. Despite the
difference in intrinsic mass scale, the shape of the M17 clump mass function
appears to be consistent with the shape of the core mass function in low-mass
star-forming regions. Thus, we suggest that the clump mass function in
high-mass star-forming regions may be a scaled-up version of that in low-mass
regions, instead of its extension to higher masses.Comment: 33 pages, 6 figures, 3 tables. Accepted for publication in the
Astrophysical Journa
A deep wide-field sub-mm survey of the Carina Nebula complex
The Great Nebula in Carina is a superb location in which to study the physics
of violent massive star-formation and the resulting feedback effects, including
cloud dispersal and triggered star-formation. In order to reveal the cold dusty
clouds in the Carina Nebula complex, we used the Large APEX Bolometer Camera
LABOCA at the APEX telescope to map a 1.25 deg x 1.25 deg (= 50 x 50 pc^2)
region at 870 micrometer. From a comparison to Halpha images we infer that
about 6% of the 870 micrometer flux in the observed area is likely free-free
emission from the HII region, while about 94% of the flux is very likely
thermal dust emission. The total (dust + gas) mass of all clouds for which our
map is sensitive is ~ 60 000 Msun, in good agreement with the mass of the
compact clouds in this region derived from 13CO line observations. We generally
find good agreement in the cloud morphology seen at 870 micrometer and the
Spitzer 8 micrometer emission maps, but also identify a prominent infrared dark
cloud. Finally, we construct a radiative transfer model for the Carina Nebula
complex that reproduces the observed integrated spectral energy distribution
reasonably well. Our analysis suggests a total gas + dust mass of about 200000
Msun in the investigated area; most of this material is in the form of
molecular clouds, but a widely distributed component of (partly) atomic gas,
containing up to ~ 50% of the total mass, may also be present. Currently, only
some 10% of the gas is in sufficiently dense clouds to be immediately available
for future star formation, but this fraction may increase with time owing to
the ongoing compression of the strongly irradiated clouds and the expected
shockwaves of the imminent supernova explosions.Comment: Accepted for publication in Astronomy & Astrophysics; high-quality
pre-prints can be obtained from
http://www.usm.uni-muenchen.de/people/preibisch/publications.htm
High-mass star formation at high luminosities: W31 at >10^6 L_sun
Context: High-mass star formation has been a very active field over the last
decade, however, most studies targeted regions of luminosities between 10^4 and
10^5 L_sun. Methods: We selected the W31 star-forming complex with a total
luminosity of ~6x10^6 L_sun for a multi-wavelength spectral line and continuum
study covering wavelengths from the near- and mid-infrared via (sub)mm
wavelength observations to radio data in the cm regime. Results: While the
overall structure of the multi-wavelength continuum data resembles each other
well, there are several intriguing differences. The 24mum emission stemming
largely from small dust grains follows tightly the spatial structure of the cm
emission tracing the ionized free-free emission. Hence warm dust resides in
regions that are spatially associated with the ionized hot gas (~10^4 K) of the
HII regions. Furthermore, we find several evolutionary stages within the same
complexes, ranging from infrared-observable clusters, via deeply embedded
regions associated with active star formation traced by 24\,m and cm
emission, to at least one high-mass gas clump devoid of any such signature. The
13CO(2-1) and C18O(2-1) spectral line observations reveal a large kinematic
breadth in the entire region with a total velocity range of approximately 90
km/s. While the average virial mass ratio for W31 is close to unity, the line
width analysis indicates large-scale evolutionary differences between the
southern and northern sub-regions (G10.2-0.3 and G10.3-0.1) of the whole W31
complex. The clump mass function - tracing cluster scales and not scales of
individual stars - derived from the 875mum continuum data has a slope of
1.5+-0.3, consistent with previous cloud mass functions.Comment: 13 pages, 11 figures, accepted for Astronomy and Astrophysics,
high-resolution version of paper at
http://www.mpia.de/homes/beuther/papers.htm
The alignment of molecular cloud magnetic fields with the spiral arms in M33
The formation of molecular clouds, which serve as stellar nurseries in
galaxies, is poorly understood. A class of cloud formation models suggests that
a large-scale galactic magnetic field is irrelevant at the scale of individual
clouds, because the turbulence and rotation of a cloud may randomize the
orientation of its magnetic field. Alternatively, galactic fields could be
strong enough to impose their direction upon individual clouds, thereby
regulating cloud accumulation and fragmentation, and affecting the rate and
efficiency of star formation. Our location in the disk of the Galaxy makes an
assessment of the situation difficult. Here we report observations of the
magnetic field orientation of six giant molecular cloud complexes in the
nearby, almost face-on, galaxy M33. The fields are aligned with the spiral
arms, suggesting that the large-scale field in M33 anchors the clouds.Comment: to appear in Natur
The mitochondrial fission protein Drp1 in liver is required to mitigate NASH and prevents the activation of the mitochondrial ISR
[Objective]: The mitochondrial fission protein Drp1 was proposed to promote NAFLD, as inhibition of hepatocyte Drp1 early in life prevents liver steatosis induced by high-fat diet in mice. However, whether Drp1-knockdown in older mice can reverse established NASH is unknown.
[Methods]: N-acetylgalactosamine-siRNA conjugates, an FDA approved method to deliver siRNA selectively to hepatocytes, were used to knockdown hepatocyte-Drp1 in mice (NAG-Drp1si). NASH was induced in C57BL/6NTac mice by Gubra-Amylin-NASH diet (D09100310, 40% fat, 22% fructose and 2% cholesterol) and treatment with NAG-Drp1si was started at week 24 of diet. Circulating transaminases, liver histology, gene expression of fibrosis and inflammation markers, and hydroxyproline synthesis determined NASH severity. Liver NEFA and triglycerides were quantified by GC/MS. Mitochondrial function was determined by respirometry. Western blots of Oma1, Opa1, p-eIf2α, as well as transcriptional analyses of Atf4-regulated genes determined ISR engagement.
[Results]: NAG-Drp1si treatment decreased body weight and induced liver inflammation in adult healthy mice. Increased hepatic Gdf15 production was the major contributor to body-weight loss caused by NAG-Drp1si treatment, as Gdf15 receptor deletion (Gfral KO) prevented the decrease in food intake and mitigated weight loss. NAG-Drp1si activated the Atf4-controlled integrated stress response (ISR) to increase hepatic Gdf15 expression. NAG-Drp1si in healthy mice caused ER stress and activated the mitochondrial protease Oma1, which are the ER and mitochondrial triggers that activate the Atf4-controlled ISR. Remarkably, induction of NASH was not sufficient to activate Oma1 in liver. However, NAG-Drp1si treatment was sufficient to activate Oma1 in adult mice with NASH, as well as exacerbating NASH-induced ER stress. Consequently, NAG-Drp1si treatment in mice with NASH led to higher ISR activation, exacerbated inflammation, fibrosis and necrosis.
[Conclusion]: Drp1 mitigates NASH by decreasing ER stress, preventing Oma1 activation and ISR exacerbation. The elevation in Gdf15 actions induced by NAG-Drp1si might represent an adaptive response decreasing the nutrient load to liver when mitochondria are misfunctional. Our study argues against blocking Drp1 in hepatocytes to combat NASH.M.L. and O.S.S. are funded by Janssen Research and Development, LLC, ICD #M3229099 – 846328. O.S.S. is funded by R01 DK099618-05; R01 CA232056-01; R21AG060456-01; R21 AG063373-01
Herschel / HIFI observations of CO, H2O and NH3 in Mon R2
Context. Mon R2 is the only ultracompact HII region (UCHII) where the
associated photon-dominated region (PDR) can be resolved with Herschel. Due to
its brightness and proximity, it is the best source to investigate the
chemistry and physics of highly UV-irradiated PDRs. Aims. Our goal is to
estimate the abundance of H2O and NH3 in this region and investigate their
origin. Methods. We present new observations obtained with HIFI and the
IRAM-30m telescope. Using a large velocity gradient approach, we model the line
intensities and derive an average abundance of H2O and NH3 across the region.
Finally, we model the line profiles with a non-local radiative transfer model
and compare these results with the abundance predicted by the Meudon PDR code.
Results. The variations of the line profiles and intensities indicate complex
geometrical and kinematical patterns. The H2O lines present a strong absorption
at the ambient velocity and emission in high velocity wings towards the HII
region. The spatial distribution of the o-H2^18O line shows that the its
emission arises in the PDR surrounding the HII region. By modeling the o-H2^18O
emission we derive a mean abundance of o-H2O of ~10^-8 relative to H2. The
ortho-H2O abundance is however larger, ~1x10^-7, in the high velocity wings.
Possible explanations for this larger abundance include an expanding hot PDR
and/or an outflow. Ammonia seems to be present only in the envelope with an
average abundance of ~2x10^-9 relative to H2. Conclusions. The Meudon PDR code
can account for the measured water abundance in the high velocity gas as long
as we assume that it originates from a <1 mag hot expanding layer of the PDR,
i.e. that the outflow has only a minor contribution to this emission. To
explain the abundances in the rest of the cloud the molecular freeze out and
grain surface chemistry would need to be included.Comment: 12 pages, 7 figures, 3 tables. Accepted for publication in A&A.
Abstract shortened. Updated references, language editing applied in v
CHESS, Chemical Herschel surveys of star forming regions:Peering into the protostellar shock L1157-B1
The outflow driven by the low-mass class 0 protostar L1157 is the prototype
of the so-called chemically active outflows. The bright bowshock B1 in the
southern outflow lobe is a privileged testbed of magneto-hydrodynamical (MHD)
shock models, for which dynamical and chemical processes are strongly
interdependent. We present the first results of the unbiased spectral survey of
the L1157-B1 bowshock, obtained in the framework of the key program "Chemical
Herschel Surveys of Star Forming Regions" (CHESS). The main aim is to trace the
warm and chemically enriched gas and to infer the excitation conditions in the
shock region. The CO 5-4 and H2O lines have been detected at high-spectral
resolution in the unbiased spectral survey of the HIFI-Band 1b spectral window
(555-636 GHz), presented by Codella et al. in this volume. Complementary
ground-based observations in the submm window help establish the origin of the
emission detected in the main-beam of HIFI, and the physical conditions in the
shock.}{Both lines exhibit broad wings, which extend to velocities much higher
than reported up to now. We find that the molecular emission arises from two
regions with distinct physical conditions: an extended, warm (100K), dense (3e5
cm-3) component at low-velocity, which dominates the water line flux in Band~1;
a secondary component in a small region of B1 (a few arcsec) associated with
high-velocity, hot (> 400 K) gas of moderate density ((1.0-3.0)e4 cm-3), which
appears to dominate the flux of the water line at 179mu observed with PACS. The
water abundance is enhanced by two orders of magnitude between the low- and the
high-velocity component, from 8e-7 up to 8e-5. The properties of the
high-velocity component agree well with the predictions of steady-state C-shock
models.Comment: Accepted for Publication in Astronomy and Astrophysics (Herschel
Special Issue
The CHESS chemical Herschel surveys of star forming regions: Peering into the protostellar shock L1157-B1. I. Shock chemical complexity
We present the first results of the unbiased survey of the L1157-B1 bow
shock, obtained with HIFI in the framework of the key program Chemical Herschel
surveys of star forming regions (CHESS). The L1157 outflow is driven by a
low-mass Class 0 protostar and is considered the prototype of the so-called
chemically active outflows. The bright blue-shifted bow shock B1 is the ideal
laboratory for studying the link between the hot (around 1000-2000 K) component
traced by H2 IR-emission and the cold (around 10-20 K) swept-up material. The
main aim is to trace the warm gas chemically enriched by the passage of a shock
and to infer the excitation conditions in L1157-B1. A total of 27 lines are
identified in the 555-636 GHz region, down to an average 3 sigma level of 30
mK. The emission is dominated by CO(5-4) and H2O(110-101) transitions, as
discussed by Lefloch et al. (2010). Here we report on the identification of
lines from NH3, H2CO, CH3OH, CS, HCN, and HCO+. The comparison between the
profiles produced by molecules released from dust mantles (NH3, H2CO, CH3OH)
and that of H2O is consistent with a scenario in which water is also formed in
the gas-phase in high-temperature regions where sputtering or grain-grain
collisions are not efficient. The high excitation range of the observed tracers
allows us to infer, for the first time for these species, the existence of a
warm (> 200 K) gas component coexisting in the B1 bow structure with the cold
and hot gas detected from ground
Discrepancy between German S3 Guideline Recommendations and Daily Urologic Practice in the Management of Nonmuscle Invasive Bladder Cancer: Results of a Binational Survey
Introduction: Guideline recommendations are meant to help minimize morbidity and to improve the care of nonmuscle invasive bladder cancer (NMIBC) patients but studies have suggested an underuse of guideline-recommended care. The aim of this study was to evaluate the level of adherence of German and Austrian urologists to German guideline recommendations. Methods: A survey of 27 items evaluating diagnostic and therapeutic recommendations (15 cases of strong consensus and 6 cases of consensus) for NMIBC was administered among 14 urologic training courses. Survey construction and realization followed the checklist for reporting results of internet e-surveys and was approved by an internal review board. Results: Between January 2018 and June 2019, a total of 307 urologists responded to the questionnaire, with a mean response rate of 71%. The data showed a weak role of urine cytology (54%) for initial diagnostics although it is strongly recommended by the guideline. The most frequently used supporting diagnostic tool during transurethral resection of the bladder was hexaminolevulinate (95%). Contrary to the guideline recommendation, 38% of the participants performed a second resection in the case of pTa low-grade NMIBC. Correct monitoring of Bacille Calmette-Guerin (BCG) response with cystoscopy and cytology was performed by only 34% of the urologists. Conclusions: We found a discrepancy between certain guideline recommendations and daily routine practice concerning the use of urine cytology for initial diagnostics, instillation therapy with a low monitoring rate of BCG response, and follow-up care with unnecessary second resection after pTa low-grade NMIBC in particular. Our survey showed a moderate overall adherence rate of 73%. These results demonstrate the need for sharpening awareness of German guideline recommendations by promoting more intense education of urologists to optimize NMIBC care thus decreasing morbidity and mortality rates
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