Patrick M. Koch

SUNYAEV-ZEL'DOVICH-MEASURED PRESSURE PROFILES FROM THE BOLOCAM X-RAY/SZ GALAXY CLUSTER SAMPLE

We describe Sunyaev-Zel’dovich (SZ) effect measurements and analysis of the intracluster medium (ICM) pressure profiles of a set of 45 massive galaxy clusters imaged using Bolocam at the Caltech Submillimeter Observatory. We deproject the average pressure profile of our sample into 13 logarithmically spaced radial bins between 0.07R500 and 3.5R500, and we find that a generalized Navarro, Frenk, and White (gNFW) profile describes our data with sufficient goodness-of-fit and best-fit parameters (C500, �, �, , P0 = 1.18, 0.86, 3.67, 0.67, 4.29). We use X-ray data to define cool-core and disturbed subsamples of clusters, and we constrain the average pressure profiles of each of these subsamples. We find that, given the precision of our data, the average pressure profiles of disturbed and cool-core clusters are consistent with one another at R & 0.15R500, with cool-core systems showing indications of higher pressure at R . 0.15R500. In addition, for the first time, we place simultaneous constraints on the mass scaling of cluster pressure profiles, their ensemble mean profile, and their radius-dependent intrinsic scatter between 0.1R500 and 2.0R500. The scatter among profiles is minimized at radii between ≃ 0.2R500 and ≃ 0.5R500, with a value of ≃ 20%. These results for the intrinsic scatter are largely consistent with previous analyses, most of which have relied heavily on X-ray derived pressures of clusters at significantly lower masses and redshifts compared to our sample. Therefore, our data provide further evidence that cluster pressure profiles are largely universal with scatter of ≃ 20–40% about the universal profile over a wide range of masses and redshifts. Subject headings: galaxies: clusters: general — galaxies: clusters: intracluster medium

DR 21(OH): A HIGHLY FRAGMENTED, MAGNETIZED, TURBULENT DENSE CORE

We present high angular resolution observations of the massive star-forming core DR21(OH) at 880 μ mu sing the Submillimeter Array (SMA). The dense core exhibits an overall velocity gradient in a Keplerian-like pattern, which breaks at the center of the core where SMA 6 and SMA 7 are located. The dust polarization shows a complex magnetic field, compatible with a toroidal configuration. This is in contrast with the large, parsec-scale filament that surrounds the core, where there is a smooth magnetic field. The total magnetic field strengths in the filament and in the core are 0.9 and 2.1 mG, respectively. We found evidence of magnetic field diffusion at the core scales, far beyond the expected value for ambipolar diffusion. It is possible that the diffusion arises from fast magnetic reconnection in the presence of turbulence. The dynamics of the DR 21(OH) core appear to be controlled energetically in equal parts by the magnetic field, magnetohydrodynamic turbulence, and the angular momentum. The effect of the angular momentum (this is a fast rotating core) is probably causing the observed toroidal field configuration. Yet, gravitation overwhelms all the forces, making this a clear supercritical core with a mass-to-flux ratio of � 6 times the critical value. However, simulations show that this is not enough for the high level of fragmentation observed at 1000 AU scales. Thus, rotation and outflow feedback are probably the main causes of the observed fragmentation.

The AMiBA Hexapod Telescope Mount

The Array for Microwave Background Anisotropy (AMiBA) is the largest hexapod astronomical telescope in current operation. We present a description of this novel hexapod mount with its main mechanical components—the support cone, universal joints, jack screws, and platform—and outline the control system with the pointing model and the operating modes that are supported. The AMiBA hexapod mount performance is verified based on optical pointing tests and platform photogrammetry measurements. The photogrammetry results show that the deformations in the inner part of the platform are less than 120 μm rms. This is negligible for optical pointing corrections, radio alignment, and radio phase errors for the currently operational seven-element compact configuration. The optical pointing error in azimuth and elevation is successively reduced by a series of corrections to about 0 4 rms which meets our goal for the seven-element target specifications.

Greenland telescope project: Direct confirmation of black hole with sub‐millimeter VLBI

A 12 m diameter radio telescope will be deployed to the Summit Station in Greenland to provide direct confirmation of a Super Massive Black Hole (SMBH) by observing its shadow image in the active galaxy M87. The telescope (Greenland Telescope: GLT) is to become one of the Very Long Baseline Interferometry (VLBI) stations at sub-millimeter (submm) regime, providing the longest baseline >9000 km to achieve an exceptional angular resolution of 20 µas at 350 GHz, which will enable us to resolve the shadow size of ~40 µas. The triangle with the longest baselines formed by the GLT, the Atacama Large Millimeter/submillimeter Array (ALMA) in Chile, and the Submillimeter Array (SMA) in Hawaii will play a key role for the M87 observations. We have been working on the image simulations based on realistic conditions for a better understanding of the possible observed images. In parallel, retrofitting of the telescope and the site developments are in progress. Based on 3 years of opacity monitoring at 225 GHz, our measurements indicate that the site is excellent for submm observations, comparable to the ALMA site. The GLT is also expected to make single-dish observations up to 1.5 THz.

MAGNETIC FIELD STRENGTH MAPS FOR MOLECULAR CLOUDS: A NEW METHOD BASED ON A POLARIZATION-INTENSITY GRADIENT RELATION

Dust polarization orientations in molecular clouds often tend to be close to tangential to the Stokes I dust continuum emission contours. The magnetic field and the emission gradient orientations, therefore, show some correlation. A method is proposed, which—in the framework of ideal magnetohydrodynamics (MHD)—connects the measured angle between magnetic field and emission gradient orientations to the total field strength. The approach is based on the assumption that a change in emission intensity (gradient) is a measure for the resulting direction of motion in the MHD force equation. In particular, this new method leads to maps of position-dependent magnetic field strength estimates. When evaluating the field curvature and the gravity direction locally on a map, the method can be generalized to arbitrary cloud shapes. The technique is applied to high-resolution (~07) Submillimeter Array polarization data of the collapsing core W51 e2. A tentative ~7.7 mG field strength is found when averaging over the entire core. The analysis further reveals some structures and an azimuthally averaged radial profile ~r –1/2 for the field strength. Maximum values close to the center are around 19 mG. The currently available observations lack higher resolution data to probe the innermost part of the core where the largest field strength is expected from the method. Application regime and limitations of the method are discussed. As a further important outcome of this technique, the local significance of the magnetic field force compared to the other forces can be quantified in a model-independent way, from measured angles only. Finally, the method can potentially also be expanded and applied to other objects (besides molecular clouds) with measurements that reveal the field morphology, as, e.g., Faraday rotation measurements in galaxies.

SIGNS OF EARLY-STAGE DISK GROWTH REVEALED WITH ALMA

We present ALMA 1.3 mm continuum, 12CO, C18O, and SO data for the Class 0 protostars, Lupus 3 MMS, IRAS 15398-3559, and IRAS 16253-2429 at resolutions of ~100 AU. By measuring a rotational profile in C18O, a 100 AU Keplerian disk around a 0.3 Msun protostar is observed in Lupus 3 MMS. No 100 AU Keplerian disks are observed in IRAS 15398-3559 and IRAS 16253-2429. Nevertheless, embedded compact (<30 AU) continuum components are detected. The C18O emission in IRAS 15398-3559 shows signatures of infall with a constant angular momentum. IRAS 16253-2429 exhibits signatures of infall and rotation, but its rotational profile is unresolved. By fitting the C18O data with our kinematic models, the protostellar masses and the disk radii are inferred to be 0.01 Msun and 20 AU in IRAS 15398-3559, and 0.03 Msun and 6 AU in IRAS 16253-2429. By comparing the specific angular momentum profiles from 10,000 to 100 AU in 8 Class 0 and I protostars, we find that the evolution of envelope rotation can be described with conventional inside-out collapse models. In comparison with a sample of 18 protostars with known disk radii, our results reveal signs of disk growth, with the disk radius increasing as M*^{0.8+/-0.14} or t^{1.09+\-0.37} in the Class 0 stage, where M* is the protostellar mass and t is the age. The disk growth rate slows down in the Class I stage. Besides, we find a hint that the mass accretion rate declines as t^{-0.26+\-0.04} from the Class 0 to I stages.

MAGNETIC FIELD PROPERTIES IN HIGH-MASS STAR FORMATION FROM LARGE TO SMALL SCALES: A STATISTICAL ANALYSIS FROM POLARIZATION DATA

Polarization data from high-mass star formation regions (W51 e2/e8, Orion BN/KL) are used to derive statistical properties of the plane of sky projected magnetic field. Structure function and auto-correlation function are calculated for observations with various resolutions from the BIMA and SMA interferometers, covering a range in physical scales from ~70 mpc to ~2.1 mpc. Results for the magnetic field turbulent dispersion, its turbulent-to-mean field strength ratio, and the large-scale polarization angle correlation length are presented as a function of the physical scale at the star formation sites. Power-law scaling relations emerge for some of these physical quantities. The turbulent-to-mean field strength ratio is found to be close to constant over the sampled observing range, with a hint of a decrease toward smaller scales, indicating that the role of the magnetic field and turbulence is evolving with the physical scale. A statistical method is proposed to separate large- and small-scale correlations from an initial ensemble of polarization segments. This also leads to a definition of a turbulent polarization angle correlation length.

The TIME-Pilot intensity mapping experiment

TIME-Pilot is designed to make measurements from the Epoch of Reionization (EoR), when the first stars and galaxies formed and ionized the intergalactic medium. This will be done via measurements of the redshifted 157.7 um line of singly ionized carbon ([CII]). In particular, TIME-Pilot will produce the first detection of [CII] clustering fluctuations, a signal proportional to the integrated [CII] intensity, summed over all EoR galaxies. TIME-Pilot is thus sensitive to the emission from dwarf galaxies, thought to be responsible for the balance of ionizing UV photons, that will be difficult to detect individually with JWST and ALMA. A detection of [CII] clustering fluctuations would validate current theoretical estimates of the [CII] line as a new cosmological observable, opening the door for a new generation of instruments with advanced technology spectroscopic array focal planes that will map [CII] fluctuations to probe the EoR history of star formation, bubble size, and ionization state. Additionally, TIME-Pilot will produce high signal-to-noise measurements of CO clustering fluctuations, which trace the role of molecular gas in star-forming galaxies at redshifts 0 < z < 2. With its unique atmospheric noise mitigation, TIME-Pilot also significantly improves sensitivity for measuring the kinetic Sunyaev-Zel’dovich (kSZ) effect in galaxy clusters. TIME-Pilot will employ a linear array of spectrometers, each consisting of a parallel-plate diffraction grating. The spectrometer bandwidth covers 185-323 GHz to both probe the entire redshift range of interest and to include channels at the edges of the band for atmospheric noise mitigation. We illuminate the telescope with f/3 horns, which balances the desire to both couple to the sky with the best efficiency per beam, and to pack a large number of horns into the fixed field of view. Feedhorns couple radiation to the waveguide spectrometer gratings. Each spectrometer grating has 190 facets and provides resolving power above 100. At this resolution, the longest dimension of the grating is 31 cm, which allows us to stack gratings in two blocks (one for each polarization) of 16 within a single cryostat, providing a 1x16 array of beams in a 14 arcminute field of view. Direct absorber TES sensors sit at the output of the grating on six linear facets over the output arc, allowing us to package and read out the detectors as arrays in a modular manner. The 1840 detectors will be read out with the NIST time-domain-multiplexing (TDM) scheme and cooled to a base temperature of 250 mK with a 3He sorption refrigerator. We present preliminary designs for the TIME-Pilot cryogenics, spectrometers, bolometers, and optics.

THE IMPORTANCE OF THE MAGNETIC FIELD FROM AN SMA-CSO-COMBINED SAMPLE OF STAR-FORMING REGIONS

Submillimeter dust polarization measurements of a sample of 50 star-forming regions, observed with the SMA and the CSO covering pc-scale clouds to mpc-scale cores, are analyzed in order to quantify the magnetic field importance. The magnetic field misalignment

AMiBA WIDEBAND ANALOG CORRELATOR

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