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

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

The VAST Survey - IV. A wide brown dwarf companion to the A3V star ζ\zeta Delphini

We report the discovery of a wide co-moving substellar companion to the nearby ($D=67.5\pm1.1$ pc) A3V star $\zeta$ Delphini based on imaging and follow-up spectroscopic observations obtained during the course of our Volume-limited A-Star (VAST) multiplicity survey. $\zeta$ 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 $\zeta$ Del system was estimated as $525\pm125$ 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 $\zeta$ Del B is shown to be consistent with a mid-L dwarf (L$5\pm2$), at a temperature of $1650\pm200$ K. Combining the measured near-infrared magnitude of $\zeta$ Del B with the estimated temperature leads to a model-dependent mass estimate of $50\pm15$ M$_{\rm Jup}$, corresponding to a mass ratio of $q=0.019\pm0.006$. At a projected separation of $910\pm14$ au, $\zeta$ 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

Integrated heterodyne array receivers for submillimeter astronomy

The advent of large format (~100 pixel) spectroscopic imaging cameras at submillimeter wavelengths would fundamentally change the way in which astronomy is performed in this important wavelength regime. While the possibility of such instruments has been discussed for more than two decades, only recently have advances in mixer technology, device fabrication, micromachining, digital signal processing, and telescope design made the construction of such an instrument possible and economical. In our paper, we will present the design concept for a 10×10 heterodyne camera

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

Submillimeter observations of IRAS and WISE debris disk candidates

A set of six debris disk candidates identified with IRAS or WISE excesses were observed at either 350 μm or 450 μm with the Caltech Submillimeter Observatory. Five of the targets – HIP 51658, HIP 68160, HIP 73512, HIP 76375, and HIP 112460 – have among the largest measured excess emission from cold dust from IRAS in the 25–100 μm bands. Single temperature blackbody fits to the excess dust emission of these sources predict 350–450 μm fluxes above 240 mJy. The final target – HIP 73165 – exhibits weak excess emission above the stellar photosphere from WISE measurements at 22 μm, indicative of a population of warm circumstellar dust. None of the six targets were detected, with 3σ upper limits ranging from 51–239 mJy. These limits are significantly below the expected fluxes from SED fitting. Two potential causes of the null detections were explored – companion stars and contamination. To investigate the possible influence of companion stars, imaging data were analyzed from new adaptive optics data from the ARIES instrument on the 6.5 m MMT and archival HST, Gemini NIRI, and POSS/2MASS data. The images are sensitive to all stellar companions beyond a radius of 1–94 AU, with the inner limit depending on the distance and brightness of each target. One target is identified as a binary system, but with a separation too large to impact the disk. While the gravitational effects of a companion do not appear to provide an explanation for the submm upper limits, the majority of the IRAS excess targets show evidence for contaminating sources, based on investigation of higher resolution WISE and archival Spitzer and Herschel images. Finally, the exploratory submm measurements of the WISE excess source suggest that the hot dust present around these targets is not matched by a comparable population of colder, outer dust. More extensive and more sensitive Herschel observations of WISE excess sources will build upon this initial example to further define the characteristics of warm debris disks sources

The embryonic trunk neural crest microenvironment regulates the plasticity and invasion of human neuroblastoma via TrkB signaling

Mistakes in trunk neural crest (NC) cell migration may lead to birth defects of the sympathetic nervous system (SNS) and neuroblastoma (NB) cancer. Receptor tyrosine kinase B (TrkB) and its ligand BDNF critically regulate NC cell migration during normal SNS development and elevated expression of TrkB is correlated with high-risk NB patients. However, in the absence of a model with in vivo interrogation of human NB cell and gene expression dynamics, the mechanistic role of TrkB in NB disease progression remains unclear. Here, we study the functional relationship between TrkB, cell invasion and plasticity of human NB cells by taking advantage of our validated in vivo chick embryo transplant model. We find that LAN5 (high TrkB) and SHSY5Y (moderate TrkB) human NB cells aggressively invade host embryos and populate typical NC targets, however loss of TrkB function significantly reduces cell invasion. In contrast, NB1643 (low TrkB) cells remain near the transplant site, but over-expression of TrkB leads to significant cell invasion. Invasive NB cells show enhanced expression of genes indicative of the most invasive host NC cells. In contrast, transplanted human NB cells down-regulate known NB tumor initiating and stem cell markers. Human NB cells that remain within the dorsal neural tube transplant also show enhanced expression of cell differentiation genes, resulting in an improved disease outcome as predicted by a computational algorithm. These in vivo data support TrkB as an important biomarker and target to control NB aggressiveness and identify the chick embryonic trunk neural crest microenvironment as a source of signals to drive NB to a less aggressive state, likely acting at the dorsal neural tube

A field-deployed 810 GHz receiver incorporating a superconducting mixer developed for Herschel space telescope and a SiGe low noise amplifier

We have constructed an 810 GHz receiver system incorporating a HIFI Band-3 superconductor-insulator-superconductor (SIS) mixer developed for Herschel space observatory and a wide-band SiGe low noise amplifier (LNA) designed at Caltech. The instrument is currently installed at the RLT telescope (elevation 5500 m) in northern Chile. Hot/cold (280K/72K) load measurements performed at the telescope yield noise temperatures of 225 K (Y-factor = 1.7) including receiver optics. First-light observations indicate that the receiver is highly sensitive and functions stably. We present details of the receiver system, its performance at the telescope, and first-light observations with a Herschel mixer

A CO (J=3-2) Outflow Survey of the Elias 29 Region

We present a 5'x5' integrated intensity map of 12CO (J=3-2) emission from the rho-Ophiuchi cloud core that traces low-luminosity outflow emission from two protostars: Elias 29 and, most likely, LFAM 26. The morphology of the outflow from Elias 29 is bipolar and has a curved axis that traces the S-shaped symmetry seen in H_2 emission. The outflow from LFAM 26 is a new detection and oriented in the east/west direction near the plane of the sky with most of the blue-shifted emission being absorbed by intervening clouds. The outflow axis of this object also appears to intersect a knot of H_2 emission previously attributed to Elias 29. LFAM 26 is a low luminosity source (L_bol = 0.06 L_sun) which, in combination with the observed outflow, makes it a candidate Very Low Luminosity Object (VeLLO). We derive lower limits to the gas column densities and energetics for both outflows. The mechanical luminosities for Elias 29 and LFAM 26 are 6.4 and 10.3 x 10^{-3} L_sun, respectively.Comment: 9 pages, 2 figures, accepted to the ApJ