285 research outputs found
The Arizona Radio Observatory CO Mapping Survey of Galactic Molecular Clouds: III. The Serpens Cloud in CO J=2-1 and 13CO J=2-1 Emission
We mapped 12CO and 13CO J = 2-1 emission over 1.04 square deg of the Serpens
molecular cloud with 38 arcsec spatial and 0.3 km/s spectral resolution using
the Arizona Radio Observatory Heinrich Hertz Submillimeter telescope. Our maps
resolve kinematic properties for the entire Serpens cloud. We also compare our
velocity moment maps with known positions of Young Stellar Objects (YSOs) and
1.1 mm continuum emission. We find that 12CO is self-absorbed and 13CO is
optically thick in the Serpens core. Outside of the Serpens core, gas appears
in filamentary structures having LSR velocities which are blue-shifted by up to
2 km/s relative to the 8 km/s systemic velocity of the Serpens cloud. We show
that the known Class I, Flat, and Class II YSOs in the Serpens core most likely
formed at the same spatial location and have since drifted apart. The spatial
and velocity structure of the 12CO line ratios implies that a detailed
3-dimensional radiative transfer model of the cloud will be necessary for full
interpretation of our spectral data. The starless cores region of the cloud is
likely to be the next site of star formation in Serpens.Comment: 41 pages, 15 figure
Buoyancy waves in Pluto's high atmosphere: Implications for stellar occultations
We apply scintillation theory to stellar signal fluctuations in the
high-resolution, high signal/noise, dual-wavelength data from the MMT
observation of the 2007 March 18 occultation of P445.3 by Pluto. A well-defined
high wavenumber cutoff in the fluctuations is consistent with viscous-thermal
dissipation of buoyancy waves (internal gravity waves) in Pluto's high
atmosphere, and provides strong evidence that the underlying density
fluctuations are governed by the gravity-wave dispersion relation.Comment: Accepted 18 June 2009 for publication in Icaru
Dust Stratification in Young Circumstellar Disks
We present high-resolution infrared spectra of four YSOs (T Tau N, T Tau S,
RNO 91, and HL Tau). The spectra exhibit narrow absorption lines of 12CO, 13CO,
and C18O as well as broad emission lines of gas phase12CO. The narrow
absorption lines of CO are shown to originate from the colder circumstellar
gas. We find that the line of sight gas column densities resulting from the CO
absorption lines are much higher than expected for the measured extinction for
each source and suggest the gas to dust ratio is measuring the dust settling
and/or grain coagulation in these extended disks. We provide a model of
turbulence, dust settling and grain growth to explain the results. The
techniques presented here allow us to provide some observationally-motivated
bounds on accretion disk alpha in protostellar systems
Molecular Line Emission from Gravitationally Unstable Protoplanetary Disks
In the era of high resolution submillimeter interferometers, it will soon be
possible to observe the neutral circumstellar medium directly involved in gas
giant planet (GGP) formation at physical scales previously unattainable. In
order to explore possible signatures of gas giant planet formation via disk
instabilities, we have combined a 3D, non-local thermodynamic equilibrium (LTE)
radiative transfer code with a 3D, finite differences hydrodynamical code to
model molecular emission lines from the vicinity of a 1.4 M_J self-gravitating
proto-GGP. Here, we explore the properties of rotational transitions of the
commonly observed dense gas tracer, HCO+. Our main results are the following:
1. Very high lying HCO+ transitions (e.g. HCO+ J=7-6) can trace dense planet
forming clumps around circumstellar disks. Depending on the molecular
abundance, the proto-GGP may be directly imageable by the Atacama Large
Millimeter Array (ALMA). 2. HCO+ emission lines are heavily self-absorbed
through the proto-GGP's dense molecular core. This signature is nearly
ubiquitous, and only weakly dependent on assumed HCO+ abundances. The
self-absorption features are most pronounced at higher angular resolutions.
Dense clumps that are not self-gravitating only show minor self-absorption
features. 3. Line temperatures are highest through the proto-GGP at all assumed
abundances and inclination angles. Conversely, due to self-absorption in the
line, the velocity-integrated intensity may not be. High angular resolution
interferometers such as the Submillimeter Array (SMA) and ALMA may be able to
differentiate between competing theories of gas giant planet formation.Comment: 10 pages, 13 figures; Accepted by Ap
Warm-Dense Molecular Gas in the ISM of Starbursts, LIRGs and ULIRGs
The role of star formation in luminous and ultraluminous infrared galaxies is
a hotly debated issue: while it is clear that starbursts play a large role in
powering the IR luminosity in these galaxies, the relative importance of
possible enshrouded AGNs is unknown. It is therefore important to better
understand the role of star forming gas in contributing to the infrared
luminosity in IR-bright galaxies. The J=3 level of 12CO lies 33K above ground
and has a critical density of ~1.5 X 10^4 cm^-3. The 12CO(J=3-2) line serves as
an effective tracer for warm-dense molecular gas heated by active star
formation. Here we report on 12CO (J=3-2) observations of 17 starburst spirals,
LIRGs and ULIRGs which we obtained with the Heinrich Hertz Submillimeter
Telescope on Mt. Graham, Arizona.
Our main results are the following: 1. We find a nearly linear relation
between the infrared luminosity and warm-dense molecular gas such that the
infrared luminosity increases as the warm-dense molecular gas to the power
0.92; We interpret this to be roughly consistent with the recent results of Gao
& Solomon (2004a,b). 2. We find L_IR/M_H2 ratios ranging from ~10 to ~128
L_sun/M_sun using a standard CO-H2 conversion factor of 3 X 10^20 cm^-2 (K km
s^-1)^-1. If this conversion factor is ~an order of magnitude less, as
suggested in a recent statistical survey (Yao et al. 2003), then 2-3 of our
objects may have significant contributions to the L_IR by dust-enshrouded AGNs.Comment: 15 Pages, 2 figures, Accepted for Publication in Ap
CycleTrak: A novel system for the semi-automated analysis of cell cycle dynamics
AbstractCell proliferation is crucial to tissue growth and form during embryogenesis, yet dynamic tracking of cell cycle progression and cell position presents a challenging roadblock. We have developed a fluorescent cell cycle indicator and single cell analysis method, called CycleTrak, which allows for better spatiotemporal resolution and quantification of cell cycle phase and cell position than current methods. Our method was developed on the basis of the existing Fucci method. CycleTrak uses a single lentiviral vector that integrates mKO2-hCdt1 (30/120), and a nuclear-localized eGFP reporter. The single vector and nuclear localized fluorescence signals simplify delivery into cells and allow for rapid, automated cell tracking and cell cycle phase readout in single and subpopulations of cells. We validated CycleTrak performance in metastatic melanoma cells and identified novel cell cycle dynamics in vitro and in vivo after transplantation and 3D confocal time-lapse imaging in a living chick embryo
The VAST Survey - IV. A wide brown dwarf companion to the A3V star Delphini
We report the discovery of a wide co-moving substellar companion to the
nearby ( pc) A3V star Delphini based on imaging and
follow-up spectroscopic observations obtained during the course of our
Volume-limited A-Star (VAST) multiplicity survey. Del was observed over
a five-year baseline with adaptive optics, revealing the presence of a
previously-unresolved companion with a proper motion consistent with that of
the A-type primary. The age of the Del system was estimated as
Myr based on the position of the primary on the colour-magnitude
and temperature-luminosity diagrams. Using intermediate-resolution
near-infrared spectroscopy, the spectrum of Del B is shown to be
consistent with a mid-L dwarf (L), at a temperature of K.
Combining the measured near-infrared magnitude of Del B with the
estimated temperature leads to a model-dependent mass estimate of
M, corresponding to a mass ratio of . At a
projected separation of au, Del B is among the most
widely-separated and extreme-mass ratio substellar companions to a
main-sequence star resolved to-date, providing a rare empirical constraint of
the formation of low-mass ratio companions at extremely wide separations.Comment: 12 pages, 11 figures, accepted for publication in the Monthly Notices
of the Royal Astronomical Society, 2014 September 25. Revised to incorporate
typographical errors noted during the proofing proces
Adaptive Optics Images of Kepler Objects of Interest
All transiting planets are at risk of contamination by blends with nearby,
unresolved stars. Blends dilute the transit signal, causing the planet to
appear smaller than it really is, or produce a false positive detection when
the target star is blended with eclipsing binary stars. This paper reports on
high spatial-resolution adaptive optics images of 90 Kepler planetary
candidates. Companion stars are detected as close as 0.1 arcsec from the target
star. Images were taken in the near-infrared (J and Ks bands) with ARIES on the
MMT and PHARO on the Palomar Hale 200-inch. Most objects (60%) have at least
one star within 6 arcsec separation and a magnitude difference of 9. Eighteen
objects (20%) have at least one companion within 2 arcsec of the target star; 6
companions (7%) are closer than 0.5 arcsec. Most of these companions were
previously unknown, and the associated planetary candidates should receive
additional scrutiny. Limits are placed on the presence of additional companions
for every system observed, which can be used to validate planets statistically
using the BLENDER method. Validation is particularly critical for low-mass,
potentially Earth-like worlds, which are not detectable with current-generation
radial velocity techniques. High-resolution images are thus a crucial component
of any transit follow-up program.Comment: 9 pages, 4 figures, accepted to A
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