669 research outputs found
Observations of Global and Local Infall in NGC 1333
We report ``infall asymmetry'' in the HCO (1--0) and (3--2) lines toward
NGC 1333, extended over , a larger extent than has been
reported be fore, for any star-forming region. The infall asymmetry extends
over a major portion of the star-forming complex, and is not limited to a
single protostar, or to a single dense core, or to a single spectral line. It
seems likely that the infall asymmetry represents inward motions, and that
these motions are physically associated with the complex. Both blue-asymmetric
and red-asymmetric lines are seen, but in both the (3--2) and (1--0) lines of
HCO the vast majority of the asymmetric lines are blue, indicating inward
motions. The (3--2) line, tracing denser gas, has the spectra with the
strongest asymmetry and these spectra are associated with the protostars IRAS
4A and 4B, which most likely indicates a warm central source is affecting the
line profiles. The (3--2) and (1--0) lines usually have the same sense of
asymmetry in common positions, but their profiles differ significantly, and the
(1--0) line appears to trace motions on much larger spatial scales than does
the (3--2) line. Line profile models fit the spectra well, but do not strongly
constrain their parameters. The mass accretion rate of the inward motions is of
order 10 M/yr, similar to the ratio of stellar mass to cluster
age.Comment: 28 pages, 11 figures, 1 colour figur
An S-shaped outflow from IRAS 03256+3055 in NGC 1333
The IRAS source 03256+3055 in the NGC 1333 star forming region is associated
with extended sub-millimeter emission of complex morphology, showing multiple
clumps. One of these is found to coincide with the driving source of a bipolar
jet of S-shaped morphology seen in the emission lines of H_alpha and [SII] as
well as in the H2 emission lines in the K-band. Detailed images of the driving
source at the wavelengths of H_alpha and [SII] and in the I, J, H, and K bands
as well as a K-band spectrum and polarimetry are discussed. The near-infrared
morphology is characterized by a combination of line emission from the jet and
scattered light from a source with a steep continuum spectrum. The morphology
and proper motion of the jet are discussed in the context of a binary system
with a precessing disk. We conclude that the molecular core associated with
IRAS 03256+3055 consists of several clumps, only one of which shows evidence of
recent star formation at optical and near-infrared wavelengths.We also briefly
discuss a second, newly found near-infrared source associated with a compact
sub-millimeter continuum source near IRAS 03256+3055, and conclude that this
source may be physically unrelated the cluster of molecular clumps.Comment: 25 pages, including 5 figures. Accepted for publication in The
Astronomical Journa
Opening up the Quantum Three-Box Problem with Undetectable Measurements
One of the most striking features of quantum mechanics is the profound effect
exerted by measurements alone. Sophisticated quantum control is now available
in several experimental systems, exposing discrepancies between quantum and
classical mechanics whenever measurement induces disturbance of the
interrogated system. In practice, such discrepancies may frequently be
explained as the back-action required by quantum mechanics adding quantum noise
to a classical signal. Here we implement the 'three-box' quantum game of
Aharonov and Vaidman in which quantum measurements add no detectable noise to a
classical signal, by utilising state-of-the-art control and measurement of the
nitrogen vacancy centre in diamond.
Quantum and classical mechanics then make contradictory predictions for the
same experimental procedure, however classical observers cannot invoke
measurement-induced disturbance to explain this discrepancy. We quantify the
residual disturbance of our measurements and obtain data that rule out any
classical model by > 7.8 standard deviations, allowing us for the first time to
exclude the property of macroscopic state-definiteness from our system. Our
experiment is then equivalent to a Kochen-Spekker test of quantum
non-contextuality that successfully addresses the measurement detectability
loophole
Using radium isotopes to characterize water ages and coastal mixing rates: A sensitivity analysis
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W., 2006, PAPERS SUMMER UNDERG, P51 Taniguchi M, 2003, BIOGEOCHEMISTRY, V66, P35, DOI 10.1023/B:BIOG.0000006090.25949.8d Taylor J. R., 1997, INTRO ERROR ANAL, P160 Turner IL, 1997, J COASTAL RES, V13, P46 Weinstein Y., 2006, RADIOACT ENV, V8, P360, DOI DOI 10.1016/S1569-4860(05)08029-0 Windom HL, 2006, MAR CHEM, V102, P252, DOI 10.1016/j.marchem.2006.06.016 Knee, Karen L. Garcia-Solsona, Ester Garcia-Orellana, Jordi Boehm, Alexandria B. Paytan, Adina 4 AMER SOC LIMNOLOGY OCEANOGRAPHY WACO LIMNOL OCEANOGR-METHNumerous studies have used naturally occurring Ra isotopes (Ra-223, Ra-224, Ra-226, and Ra-228, with half-lives of 11.4 d, 3.7 d, 1600 y, and 5.8 y, respectively) to quantify water mass ages, coastal ocean mixing rates, and submarine groundwater discharge (SGD). Using Monte Carlo models, this study investigated how uncertainties in Ra isotope activities and the derived activity ratios (AR) arising from analytical uncertainty and natural variability affect the uncertainty associated with Ra-derived water ages and eddy diffusion coefficients, both of which can be used to calculate SGD. Analytical uncertainties associated with Ra-224, Ra-226, and Ra-228 activities were reported in most published studies to be less than 10% of sample activity; those reported for Ra-223 ranged from 7% to 40%. Relative uncertainty related to natural variability-estimated from the variability in Ra-223 and Ra-224 activities of replicate field samples-ranged from 15% to 50% and was similar for Ra-223 activity, Ra-224 activity, and the Ra-224/Ra-223 AR. Our analysis revealed that AR-based water ages shorter than 3-5 d often have relative uncertainties greater than 100%, potentially limiting their utility. Uncertainties in eddy diffusion coefficients estimated based on cross-shore gradients in short-lived Ra isotope activity were greater when fewer points were used to determine the linear trend, when the coefficient of determination (R-2) was low, and when Ra-224, rather than Ra-223, was used. By exploring the uncertainties associated with Ra-derived water ages and eddy diffusion coefficients, this study will enable researchers to apply these methods more effectively and to reduce uncertainty
Picosecond mass spectrometry of a collisionless photodissociation reaction
We wish to report on the direct observation (in real time) of a photodissociation reaction under collisionless conditions. This is achieved by the technique of picosecond mass spectrometry in skimmed molecular beams
Spitzer Observations of NGC 1333: A Study of Structure and Evolution in a Nearby Embedded Cluster
We present a comprehensive analysis of structure in the young, embedded
cluster, NGC 1333 using members identified with Spitzer and 2MASS photometry
based on their IR-excess emission. In total, 137 members are identified in this
way, composed of 39 protostars and 98 more evolved pre-main sequence stars with
disks. Of the latter class, four are transition/debris disk candidates. The
fraction of exposed pre-main sequence stars with disks is 83% +/- 11%, showing
that there is a measurable diskless pre-main sequence population. The sources
in each of the Class I and Class II evolutionary states are shown to have very
different spatial distributions relative to the distribution of the dense gas
in their natal cloud. However, the distribution of nearest neighbor spacings
among these two groups of sources are found to be quite similar, with a strong
peak at spacings of 0.045 pc. Radial and azimuthal density profiles and surface
density maps computed from the identified YSOs show that NGC 1333 is elongated
and not strongly centrally concentrated, confirming previous claims in the
literature. We interpret these new results as signs of a low velocity
dispersion, extremely young cluster that is not in virial equilibrium.Comment: 59 pages, 20 figures, accepted to ApJ, verion with full resolution
figures available at
http://www.cfa.harvard.edu/~rgutermuth/preprints/gutermuth_ngc1333.pdf .
Updated to fix astro-ph figure garblin
Infall, Outflow, Rotation, and Turbulent Motions of Dense Gas within NGC 1333 IRAS 4
Millimeter wavelength observations are presented of NGC 1333 IRAS 4, a group
of highly-embedded young stellar objects in Perseus, that reveal motions of
infall, outflow, rotation, and turbulence in the dense gas around its two
brightest continuum objects, 4A and 4B. These data have finest angular
resolution of approximately 2" (0.0034 pc) and finest velocity resolution of
0.13 km/s. Infall motions are seen from inverse P-Cygni profiles observed in
H2CO 3_12-2_11 toward both objects, but also in CS 3-2 and N2H+ 1-0 toward 4A,
providing the least ambiguous evidence for such motions toward low-mass
protostellar objects. Outflow motions are probed by bright line wings of H2CO
3_12-2_11 and CS 3-2 observed at positions offset from 4A and 4B, likely
tracing dense cavity walls. Rotational motions of dense gas are traced by a
systematic variation of the N2H+ line velocities, and such variations are found
around 4A but not around 4B. Turbulent motions appear reduced with scale, given
N2H+ line widths around both 4A and 4B that are narrower by factors of 2 or 3
than those seen from single-dish observations. Minimum observed line widths of
approximately 0.2 km/s provide a new low, upper bound to the velocity
dispersion of the parent core to IRAS 4, and demonstrate that turbulence within
regions of clustered star formation can be reduced significantly. A third
continuum object in the region, 4B', shows no detectable line emission in any
of the observed molecular species.Comment: LateX, 51 pages, 9 figures, accepted by Ap
Turbulence driven by outflow-blown cavities in the molecular cloud of NGC 1333
Outflows from young stellar objects have been identified as a possible source
of turbulence in molecular clouds. To investigate the relationship between
outflows, cloud dynamics and turbulence, we compare the kinematics of the
molecular gas associated with NGC 1333, traced in 13CO(1-0), with the
distribution of young stellar objects (YSOs) within. We find a velocity
dispersion of ~ 1-1.6 km/s in 13CO that does not significantly vary across the
cloud, and is uncorrelated with the number of nearby young stellar outflows
identified from optical and submillimeter observations. However, from velocity
channel maps we identify about 20 cavities or depressions in the 13CO intensity
of scales > 0.1-0.2 pc and velocity widths 1-3 km/s. The cavities exhibit limb
brightened rims in both individual velocity channel maps and position velocity
diagrams, suggesting that they are slowly expanding. We interpret these
cavities to be remnants of past YSO outflow activity: If these cavities are
presently empty, they would fill in on time scales of a million years. This can
exceed the lifetime of a YSO outflow phase, or the transit time of the central
star through the cavity, explaining the the absence of any clear correlation
between the cavities and YSO outflows. We find that the momentum and energy
deposition associated with the expansion of the cavities is sufficient to power
the turbulence in the cloud. In this way we conclude that the cavities are an
important intermediary step between the conversion of YSO outflow energy and
momentum into cloud turbulent motions.Comment: Accepted for publication in ApJ. Check out
http://astro.pas.rochester.edu/~aquillen/coolpics.html for channel map and
PosVel movies of N133
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