Embedded Oscillating Starless Cores (2008)
Broderick, Avery E., Narayan, Ramesh, Keto, Eric, Lada, Charles J.
In a previous paper we demonstrated that non-radial hydrodynamic oscillations of a thermally-supported (Bonnor-Ebert) sphere embedded in a low-density, high-temperature medium persist for many...
The Different Structures of the Two Classes of Starless Cores (2008)
We describe a model for the thermal and dynamical equilibrium of starless cores that includes the radiative transfer of the gas and dust and simple CO chemistry. The model shows that the structure...
The Ionization of Accretion Flows in High Mass Star Formation: W51e2 (2008)
Previous observations show that the hypercompact HII region W51e2 is surrounded by a massive molecular accretion flow centered on the HII region. New observations of the H53alpha radio recombination...
Time Variation in G24.78+0.08 A1: Evidence for an Accreting Hypercompact H II Region? (2008)
Galván-Madrid, Roberto, Rodríguez, Luis F., Ho, Paul T. P., Keto, Eric
Over a timescale of a few years, an observed change in the optically thick radio continuum flux can indicate whether an unresolved H II region around a newly formed massive star is changing in size....
Oscillating Starless Cores: The Nonlinear Regime (2007)
Broderick, Avery E., Keto, Eric, Lada, Charles J., Narayan, Ramesh
In a previous paper, we modeled the oscillations of a thermally-supported (Bonnor-Ebert) sphere as non-radial, linear perturbations following a standard analysis developed for stellar pulsations. The...
The Early Evolution of Massive Stars: Radio Recombination Line Spectra (2007)
Keto, Eric, Zhang, Qizhou, Kurtz, Stanley
Velocity shifts and differential broadening of radio recombination lines are used to estimate the densities and velocities of the ionized gas in several hypercompact and ultracompact HII regions....
The hypothesis that massive stars form by accretion can be investigated by simple analytical calculations that describe the effect that the formation of a massive star has on its own accretion flow....
Oscillations of starless cores (2006)
Keto, Eric, Broderick, Avery, Lada, Charles J., Narayan, Ramesh
If the split, asymmetric molecular spectral line profiles that are seen in many starless cores are interpreted as indicative of global collapse or expansion of the core then one possible implication...
A Model of Cloud Fragmentation (2006)
Field, George B., Blackman, Eric G., Keto, Eric
We present a model in which the supersonic motions observed in molecular clouds are driven by gravitational energy released as large structures fragment into smaller ones. The fragmentation process...
Observations on the Formation of Massive Stars by Accretion (2005)
Observations of the H66a recombination line from the ionized gas in the cluster of newly formed massive stars, G10.6-0.4, show that most of the continuum emission derives from the dense gas in an...
M82, Starbursts, Star Clusters, and the Formation of Globular Clusters (2005)
Keto, Eric, Ho, Luis C., Lo, K. Y.
We observed the nearby starburst galaxy M82 in CO in the higher frequency (2--1) transition to achieve an angular resolution below 1 arc second or 17 pc at the target. We resolved the molecular gas...
Dark cloud cores and gravitational decoupling from turbulent flows (2005)
We test the hypothesis that the starless cores may be gravitationally bound clouds supported largely by thermal pressure by comparing observed molecular line spectra to theoretical spectra produced...
An Infalling Torus of Molecular Gas Around the Ultra-Compact HII Region G28.20-0.05 (2005)
Sollins, Peter K., Zhang, Qizhou, Keto, Eric, Ho, Paul T. P
We present new observations of the ultra-compact HII region G28.20-0.05 in 23 GHz continuum, and the NH3(1,1), NH3(2.2), and NH3(3,3) lines. To explain the complicated kinematics of the molecular...
Spherical Infall in G10.6-0.4: Accretion Through an Ultracompact HII Region (2004)
Sollins, Peter K., Zhang, Qizhou, Keto, Eric, Ho, Paul T. P
We present high resolution (0.''12 x 0.''079) observations of the ultracompact HII region G10.6-0.4 in 23 GHz radio continuum and the NH3(3,3) line. Our data show that the infall in the molecular...
Radiative Transfer and Starless Cores (2004)
Keto, Eric, Rybicki, George B., Bergin, Edwin A., Plume, Rene
We develop a method of analyzing radio frequency spectral line observations to derive data on the temperature, density, velocity, and molecular abundance of the emitting gas. The method incorporates...
High velocity bipolar outflow and disk-like envelope in the carbon star V Hya (2004)
Hirano, Naomi, Shinnaga, Hiroko, Fong, David, Keto, Eric, Patel, Nimesh, ...
Using the partially completed Submillimeter Array with five antennas, we have observed the CO J=2-1 and 3-2 emission from the envelope surrounding the carbon star V Hya. The high-angular resolution...
The Formation of Massive Stars by Accretion Through Trapped Hypercompact HII Regions (2003)
The formation of massive stars may take place at relatively low accretion rates over a long period of time if the accretion can continue past the onset of core hydrogen ignition. The accretion may...
Mathematical sequences known as m-sequences can replace Walsh functions in a novel method of phase switching and sideband separation in radio interferometry. The use of shifted m-sequences of four...
Radiative Transfer Modelling of the Accretion Flow onto a Star-Forming Core in W51 (1998)
Young, Lisa M., Keto, Eric, Ho, Paul T. P.
We present an analysis of the temperature, density, and velocity of the molecular gas in the star-forming core around W51 e2. A previous paper (Ho and Young 1996) describes the kinematic evidence...
Mid-Infrared Imaging of Young Stellar Objects (1995)
Liu, Michael C., Graham, James R., Ghez, A. M., Meixner, M., Skinner, C. J., Keto, Eric, ...
We present arcsecond resolution mid-infrared (8--13 $\mu$m) images and photometry of four young stellar objects (YSOs)~--- L1551-IRS5, HL~Tau, AS~205, and AS~209 (V1121~Oph)~--- taken with the...