ABSTRACT
In typical environments of star-forming clouds, converging supersonic turbulence generates shock-compressed regions, and can create strongly magnetized sheet-like layers. Numerical ...magnetohydrodynamic simulations show that within these post-shock layers, dense filaments and embedded self-gravitating cores form via gathering material along the magnetic field lines. As a result of the preferred-direction mass collection, a velocity gradient perpendicular to the filament major axis is a common feature seen in simulations. We show that this prediction is in good agreement with recent observations from the CARMA Large Area Star Formation Survey (CLASSy), from which we identified several filaments with prominent velocity gradients perpendicular to their major axes. Highlighting a filament from the north-west part of Serpens South, we provide both qualitative and quantitative comparisons between simulation results and observational data. In particular, we show that the dimensionless ratio Cv ≡ Δvh2/(GM/L), where Δvh is half of the observed perpendicular velocity difference across a filament, and M/L is the filament’s mass per unit length, can distinguish between filaments formed purely due to turbulent compression and those formed due to gravity-induced accretion. We conclude that the perpendicular velocity gradient observed in the Serpens South north-west filament can be caused by gravity-induced anisotropic accretion of material from a flattened layer. Using synthetic observations of our simulated filaments, we also propose that a density-selection effect may explain observed subfilaments (one filament breaking into two components in velocity space) as reported in recent observations.
We present H13CO+ (J = 1-0) and HNC (J = 1-0) maps of regions in Serpens South, Serpens Main, and NGC 1333 containing filaments. We also observe the Serpens regions using H13CN (J = 1-0). These dense ...gas tracer molecular line observations carried out with CARMA have an angular resolution of ∼7″, a spectral resolution of ∼0.16 km s−1, and a sensitivity of 50-100 mJy beam−1. Although the large-scale structure compares well with the Herschel dust continuum maps, we resolve finer structure within the filaments identified by Herschel. The H13CO+ emission distribution agrees with the existing CARMA N2H+ (J = 1-0) maps, so they trace the same morphology and kinematics of the filaments. The H13CO+ maps additionally reveal that many regions have multiple structures partially overlapping in the line of sight. In two regions, the velocity differences are as high as 1.4 km s−1. We identify eight filamentary structures having typical widths of 0.03-0.08 pc in these tracers. At least 50% of the filamentary structures have distinct velocity gradients perpendicular to their major axis, with average values in the range of 4-10 km s−1 pc−1. These findings are in support of the theoretical models of filament formation by 2D inflow in the shock layer created by colliding turbulent cells. We also find evidence of velocity gradients along the length of two filamentary structures; the gradients suggest that these filaments are inflowing toward the cloud core.
Gravitational forces are expected to excite spiral density waves in protoplanetary disks, disks of gas and dust orbiting young stars. However, previous observations that showed spiral structure were ...not able to probe disk midplanes, where most of the mass is concentrated and where planet formation takes place. Using the Atacama Large Millimeter/submillimeter Array, we detected a pair of trailing symmetric spiral arms in the protoplanetary disk surrounding the young star Elias 2-27. The arms extend to the disk outer regions and can be traced down to the midplane. These millimeter-wave observations also reveal an emission gap closer to the star than the spiral arms. We argue that the observed spirals trace shocks of spiral density waves in the midplane of this young disk.
We use NH3 inversion transitions to trace the dense gas in the NGC 1333 region of the Perseus molecular cloud. NH3 (1, 1) and NH3 (2, 2) maps covering an area of 102 square arcminutes at an angular ...resolution of ∼3 7 are produced by combining Very Large Array interferometric observations with Green Bank Telescope single-dish maps. The combined maps have a spectral resolution of 0.14 km s−1 and a sensitivity of 4 mJy/beam. We produce integrated intensity maps, peak intensity maps, and dispersion maps of NH3 (1, 1) and NH3 (2, 2) and a line-of-sight velocity map of NH3 (1, 1). These are used to derive the optical depth for the NH3 (1, 1) main component, the excitation temperature of NH3 (1, 1), and the rotational temperature, kinetic temperature, and column density of NH3 over the mapped area. We compare these observations with the CARMA J = 1-0 observations of N2H+ and H13CO+ and conclude that they all trace the same material in these dense star-forming regions. From the NH3 (1, 1) velocity map, we find that a velocity gradient ridge extends in an arc across the entire southern part of NGC 1333. We propose that a large-scale turbulent cell is colliding with the cloud, which could result in the formation of a layer of compressed gas. This region along the velocity gradient ridge is dotted with Class 0/I young stellar objects, which could have formed from local overdensities in the compressed gas leading to gravitational instabilities. The NH3 (1, 1) velocity dispersion map also has relatively high values along this region, thereby substantiating the shock layer argument.
We present results of high-resolution imaging toward HL Tau by the Combined Array for Research in Millimeter-wave Astronomy. We have obtained Delta *l = 1.3 mm and 2.7 mm dust continua with an ...angular resolution down to 013. Through simultaneous model fitting to the two wavelength data sets in Bayesian inference using a flared viscous accretion disk model, we estimate the physical properties of HL Tau, such as density distribution, dust opacity spectral index, disk mass, disk size, inclination angle, position angle, and disk thickness. HL Tau has a circumstellar disk mass of 0.13 M , a characteristic radius of 79 AU, an inclination of 40?, and a position angle of 136?. Although a thin disk model is preferred by our two wavelength data sets, a thick disk model is needed to explain the high mid- and far-infrared emission of the HL Tau spectral energy distribution. This could imply large dust grains settled down on the midplane with fine dust grains mixed with gas. The HL Tau disk is likely gravitationally unstable and can be fragmented between 50 and 100 AU of radius. However, we did not detect dust thermal continuum supporting the protoplanet candidate claimed by a previous study using observations of the Very Large Array at Delta *l = 1.3 cm.
The most common human cancers --lung, breast and prostate -- have a great avidity for bone, leading to painful and untreatable consequences. What makes some cancers, but not others, metastasize to ...bone, and how do they alter its physiology? Some of the molecular mechanisms that are responsible have recently been identified, and provide new molecular targets for drug development.
Abstract
We investigate the physical structure and conditions of photodissociation regions (PDRs) and molecular gas within the Pillars of Creation in the Eagle Nebula using SOFIA FEEDBACK ...observations of the C
ii
158
μ
m line. These observations are velocity resolved to 0.5 km s
−1
and are analyzed alongside a collection of complimentary data with similar spatial and spectral resolution: the O
i
63
μ
m line, also observed with SOFIA, and rotational lines of CO, HCN, HCO
+
, CS, and N
2
H
+
. Using the superb spectral resolution of SOFIA, APEX, CARMA, and BIMA, we reveal the relationships between the warm PDR and cool molecular gas layers in context of the Pillars’ kinematic structure. We assemble a geometric picture of the Pillars and their surroundings informed by illumination patterns and kinematic relationships and derive physical conditions in the PDRs associated with the Pillars. We estimate an average molecular gas density
n
H
2
∼
1.3
×
10
5
cm
−3
and an average atomic gas density
n
H
∼ 1.8 × 10
4
cm
−3
and infer that the ionized, atomic, and molecular phases are in pressure equilibrium if the atomic gas is magnetically supported. We find pillar masses of 103, 78, 103, and 18
M
⊙
for P1a, P1b, P2, and P3, respectively, and evaporation times of ∼1–2 Myr. The dense clumps at the tops of the pillars are currently supported by the magnetic field. Our analysis suggests that ambipolar diffusion is rapid and these clumps are likely to collapse within their photoevaporation timescales.
Matrix extracellular phosphoglycoprotein (MEPE) is expressed exclusively in osteoblasts, osteocytes and odontoblasts with markedly elevated expression found in X-linked hypophosphatemic rickets (Hyp) ...osteoblasts and in oncogenic hypophosphatemic osteomalacia (OHO) tumors. Because these syndromes are associated with abnormalities in mineralization and renal phosphate excretion, we examined the effects of insect-expressed full-length human-MEPE (Hu-MEPE) on serum and urinary phosphate in vivo,
33PO
4 uptake in renal proximal tubule cultures and mineralization of osteoblast cultures. Dose-dependent hypophosphatemia and hyperphosphaturia occurred in mice following intraperitoneal (IP) administration of Hu-MEPE (up to 400 μg kg
−1 31 h
−1), similar to mice given the phosphaturic hormone PTH (80 μg kg
−1 31 h
−1). Also the fractional excretion of phosphate (FEP) was stimulated by MEPE 65.0% (
P < 0.001) and PTH groups 53.3% (
P < 0.001) relative to the vehicle group 28.7% (SEM 3.97). In addition, Hu-MEPE significantly inhibited
33PO
4 uptake in primary human proximal tubule renal cells (RPTEC) and a human renal cell line (Hu-CL8) in vitro (
V
max 53.4% inhibition;
K
m 27.4 ng/ml, and
V
max 9.1% inhibition;
K
m 23.8 ng/ml, respectively). Moreover, Hu-MEPE dose dependently (50–800 ng/ml) inhibited BMP2-mediated mineralization of a murine osteoblast cell line (2T3) in vitro. Inhibition of mineralization was localized to a small (2 kDa) cathepsin B released carboxy-terminal MEPE peptide (protease-resistant) containing the acidic serine–aspartate-rich motif (ASARM peptide). We conclude that MEPE promotes renal phosphate excretion and modulates mineralization.
ABSTRACT We describe the motivation, design, and implementation of the CORNISH survey, an arcsecond-resolution radio continuum survey of the inner galactic plane at 5 GHz using the Very Large Array ...(VLA). It is a blind survey coordinated with the northern Spitzer GLIMPSE I region covering 10° < l < 65° and |b| < 1° at similar resolution. We discuss in detail the strategy that we employed to control the shape of the synthesised beam across this survey, which covers a wide range of fairly low declinations. Two snapshots separated by 4h kept the beam elongation to less that 1.5 over 75% of the survey area and less than 2 over 98% of the survey. The prime scientific motivation is to provide an unbiased survey for ultra-compact H II regions to study this key phase in massive star formation. A sensitivity around 2 mJy will allow the automatic distinction between radio-loud and radio-quiet mid-IR sources found in the Spitzer surveys. This survey has many legacy applications beyond star formation, including evolved stars, active stars and binaries, and extragalactic sources. The CORNISH survey for compact ionized sources complements other Galactic plane surveys that target diffuse and nonthermal sources, as well as atomic and molecular phases to build up a complete picture of the interstellar medium in the Galaxy.
We compute the mid-IR extinction law from 3.6 to 24 is a subset of m in three molecular clouds-Ophiuchus, Perseus, and Serpens-by combining data from the 'Cores to Disks' Spitzer Legacy Science ...program with deep JHKs imaging. Using a new technique, we are able to calculate the line-of-sight (LOS) extinction law toward each background star in our fields. With these LOS measurements, we create, for the first time, maps of the xi 2 deviation of the data from two extinction law models. Because our xi 2 maps have the same spatial resolution as our extinction maps, we can directly observe the changing extinction law as a function of the total column density. In the Spitzer Infrared Array Camera (IRAC) bands, 3.6-8 is a subset of m, we see evidence for grain growth. Below , our extinction law is well fitted by the Weingartner and Draine RV = 3.1 diffuse interstellar-medium dust model. As the extinction increases, our law gradually flattens, and for , the data are more consistent with the Weingartner and Draine RV = 5.5 model that uses larger maximum dust grain sizes. At 24 is a subset of m, our extinction law is 2-4 times higher than the values predicted by theoretical dust models, but is more consistent with the observational results of Flaherty et al. Finally, from our xi 2 maps we identify a region in Perseus where the IRAC extinction law is anomalously high considering its column density. A steeper near-IR extinction law than the one we have assumed may partially explain the IRAC extinction law in this region.
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