Stuartt A. Corder

THE 2014 ALMA LONG BASELINE CAMPAIGN: FIRST RESULTS FROM HIGH ANGULAR RESOLUTION OBSERVATIONS TOWARD THE HL TAU REGION

We present Atacama Large Millimeter/submillimeter Array (ALMA) observations from the 2014 Long Baseline Campaign in dust continuum and spectral line emission from the HL Tau region. The continuum images at wavelengths of 2.9, 1.3, and 0.87 mm have unprecedented angular resolutions of 0. ′′ 075 (10 AU) to 0. ′′ 025 (3.5 AU), revealing an astonishing level of detail in the cir cumstellar disk surrounding the young solar analogue HL Tau, with a pattern of bright and dark rings observed at all wavelengths. By fitting ellipses to the most distinct rings, we measure precise values for the disk inclination (46.72 ◦ ± 0.05 ◦ ) and position angle (+138.02 ◦ ± 0.07 ◦ ). We obtain a high-fidelity image of the 1.0 mm spectral index (�), which ranges from � � 2.0 in the optically-thick central peak and two brightest ring s, increasing to 2.3-3.0 in the dark rings. The dark rings are not devoid of emission, and we estimate a grain emissivity index of 0.8 for the innermost dark ring and lower for subsequent dark rings, consistent with some degree of grain growth and evolution. Additional clues that the rings arise from planet formation incl ude an increase in their central offsets with radius and the presence of numerous orbital resonances. At a resolution of 35 AU, we resolve the molecular component of the disk in HCO + (1-0) which exhibits a pattern over LSR velocities from 2-12 km s -1 consistent with Keplerian motion around a �1.3M⊙ star, although complicated by absorption at low blue-shifted velocities. We also serendipitously detect and resolve the nearby protost ars XZ Tau (A/B) and LkH�358 at 2.9 mm. Subject headings: stars: individual (HL Tau, XZ Tau, LkH�358) — protoplanetary disks — stars: formation — submillimeter: planetary systems — techniques: interferometric

Constraining the Planetary System of Fomalhaut Using High-resolution ALMA Observations

The dynamical evolution of planetary systems leaves observable signatures in debris disks. Optical images trace micron-sized grains, which are strongly affected by stellar radiation and need not coincide with their parent body population. Observations of millimeter-sized grains accurately trace parent bodies, but previous images lack the resolution and sensitivity needed to characterize the rings morphology. Here we present ALMA 350 GHz observations of the Fomalhaut debris ring. These observations demonstrate that the parent body population is 13-19 AU wide with a sharp inner and outer boundary. We discuss three possible origins for the ring and suggest that debris confined by shepherd planets is the most consistent with the rings morphology.

Dynamically driven evolution of the interstellar medium in M51

Massive star formation occurs in giant molecular clouds (GMCs); an understanding of the evolution of GMCs is a prerequisite to develop theories of star formation and galaxy evolution. We report the highest-fidelity observations of the grand-design spiral galaxy M51 in carbon monoxide (CO) emission, revealing the evolution of GMCs vis-a-vis the large-scale galactic structure and dynamics. The most massive GMCs (giant molecular associations (GMAs)) are first assembled and then broken up as the gas flow through the spiral arms. The GMAs and their H_2 molecules are not fully dissociated into atomic gas as predicted in stellar feedback scenarios, but are fragmented into smaller GMCs upon leaving the spiral arms. The remnants of GMAs are detected as the chains of GMCs that emerge from the spiral arms into interarm regions. The kinematic shear within the spiral arms is sufficient to unbind the GMAs against self-gravity. We conclude that the evolution of GMCs is driven by large-scale galactic dynamics—their coagulation into GMAs is due to spiral arm streaming motions upon entering the arms, followed by fragmentation due to shear as they leave the arms on the downstream side. In M51, the majority of the gas remains molecular from arm entry through the interarm region and into the next spiral arm passage.

DISK AND ENVELOPE STRUCTURE IN CLASS 0 PROTOSTARS. I. THE RESOLVED MASSIVE DISK IN SERPENS FIRS 1

We present the first results of a program to characterize the disk and envelope structure of typical Class 0 protostars in nearby low-mass star-forming regions. We use Spitzer Infrared Spectrograph (IRS) mid-infrared spectra, high-resolution Combined Array for Research in Millimeter-wave Astronomy (CARMA) 230 GHz continuum imaging, and two-dimensional radiative transfer models to constrain the envelope structure, as well as the size and mass of the circumprotostellar disk in Serpens FIRS 1. The primary envelope parameters (centrifugal radius, outer radius, outflow opening angle, and inclination) are well constrained by the spectral energy distribution (SED), including Spitzer IRAC and MIPS photometry, IRS spectra, and 1.1 mm Bolocam photometry. These together with the excellent uv-coverage (4.5-500 kλ) of multiple antenna configurations with CARMA allow for a robust separation of the envelope and a resolved disk. The SED of Serpens FIRS 1 is best fit by an envelope with the density profile of a rotating, collapsing spheroid with an inner (centrifugal) radius of approximately 600 AU, and the millimeter data by a large resolved disk with Mdisk ~ 1.0 M ☉ and Rdisk ~ 300 AU. These results suggest that large, massive disks can be present early in the main accretion phase. Results for the larger, unbiased sample of Class 0 sources in the Perseus, Serpens, and Ophiuchus molecular clouds are needed to determine if relatively massive disks are typical in the Class 0 stage.

Kinematics of the CO Gas in the Inner Regions of the TW Hya Disk

We present a detailed analysis of the spatially and spectrally resolved 12CO J = 2-1 and J = 3-2 emission lines from the TW Hya circumstellar disk, based on science verification data from the Atacama Large Millimeter/submillimeter Array (ALMA). These lines exhibit substantial emission in their high-velocity wings (with projected velocities out to 2.1 km s–1, corresponding to intrinsic orbital velocities >20 km s–1) that trace molecular gas as close as 2 AU from the central star. However, we are not able to reproduce the intensity of these wings and the general spatio-kinematic pattern of the lines with simple models for the disk structure and kinematics. Using three-dimensional non-local thermodynamic equilibrium molecular excitation and radiative transfer calculations, we construct some alternative models that successfully account for these features by modifying either (1) the temperature structure of the inner disk (inside the dust-depleted disk cavity; r < 4 AU), (2) the intrinsic (Keplerian) disk velocity field, or (3) the distribution of disk inclination angles (a warp). The latter approach is particularly compelling because a representative warped disk model qualitatively reproduces the observed azimuthal modulation of optical light scattered off the disk surface. In any model scenario, the ALMA data clearly require a substantial molecular gas reservoir located inside the region where dust optical depths are known to be substantially diminished in the TW Hya disk, in agreement with previous studies based on infrared spectroscopy. The results from these updated model prescriptions are discussed in terms of their potential physical origins, which might include dynamical perturbations from a low-mass companion with an orbital separation of a few AU.

The First ALMA view of IRAS 16293-2422: Direct detection of infall onto source B and high-resolution kinematics of source A

Aims: In this paper, we focus on the kinematical properties of a proto-binaryto study the infall and rotation of gas towards its two protostellarcomponents. Methods: We present ALMA Science Verification observations withhigh-spectral resolution of IRAS 16293-2422 at 220.2 GHz. The wealth ofmolecular lines in this source and the very high spectral resolution offered byALMA allow us to study the gas kinematics with unprecedented detail. Results:We present the first detection of an inverse P-Cygni profile towards source Bin the three brightest lines. The line profiles are fitted with a simpletwo-layer model to derive an infall rate of 4.5x10^-5 Msun/yr. This infalldetection would rule-out the previously suggested possibility of source B beinga T Tauri star. A position velocity diagram for source A shows evidence forrotation with an axis close to the line-of-sight.

ALMA Observations of the Debris Disk around the Young Solar Analog HD?107146

We present ALMA continuum observations at a wavelength of 1.25 mm of the debris disk surrounding the

Disk and Envelope Structure in Class 0 Protostars. II. High Resolution Millimeter Mapping of the Serpens Sample

\sim

GRAIN GROWTH IN THE CIRCUMSTELLAR DISKS OF THE YOUNG STARS CY Tau AND DoAr 25

100 Myr old solar analog HD 107146. The continuum emission extends from about 30 to 150 AU from the central star with a decrease in the surface brightness at intermediate radii. We analyze the ALMA interferometric visibilities using debris disk models with radial profiles for the dust surface density parametrized as i) a single power-law, ii) a single power-law with a gap, and iii) a double power-law. We find that models with a gap of radial width

Long-wavelength observations of debris discs around sun-like stars

\sim 8