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| CfA SMA Science Symposium 2009 | ||
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Oral Program (with links to pdf presentations)9:00 - 9:20 Session 1: Welcome and Intro
10:50 - 12:30 Session 3: Galactic Star Formation (chair Thushara Pillai)
3:50 - 5:10 Session 6: SgrA* and Nuclear Activity (chair Liz Humphreys)
Poster List
AbstractsDavid Wilner (CfA)Title: Introduction to SMA ScienceAbstract: The Submillimeter Array (SMA) was built near the summit of Mauna Kea, Hawaii by the Smithsonian Astrophysical Observatory (SAO) and the Academia Sinica Institute of Astronomy and Astrophysics (ASIAA) and dedicated in late 2003. The SMA is the first telescope for subarcsecond resolution imaging observations at submillimeter wavelengths, and observing time is highly competative. To set the stage for the symposium, I will describe the current capabilities of the SMA, illustrated by some interesting science data. Sean Andrews (CfA)Title: Protoplanetary Disks: Structure, Evolution, and A Glimpse at Planet FormationAbstract: With the growing number of planetary systems found around other stars, attention is increasingly focused on the origins of our Solar System and others like it. Direct observations of the primordial reservoirs of planet-building material - the disks around young stars - play a critical role in developing theoretical models of planet formation mechanisms and their efficiencies. I will present a state-of-the-art high angular resolution (0.3" = 40 AU) SubMillimeter Array survey of the 345 GHz (870 microns) dust continuum emission from young protoplanetary disks in the Ophiuchus star-forming region. Two-dimensional radiative transfer calculations are used to simultaneously fit the observed continuum visibilities and broadband SED for each disk with a parametric structure model. Compared to previous work, significant upgrades in the modeling, data quality, and angular resolution for this survey provide improved constraints on key structure parameters, particularly those that describe the spatial distribution of mass. Those modeling results will be used to help characterize the viscous properties and the likelihood of future (and perhaps even past) planet formation in these disks. A. Meredith Hughes (CfA), David J. Wilner (CfA), Jungyeon Cho (Wisconsin), Alex Lazarian (Wisconsin), Daniel P. Marrone (CfA), Ram Rao (ASIAA), Sean M. Andrews (CfA)Title: Constraining Polarized Emission from Circumstellar DisksAbstract: The structure and evolution of protoplanetary disks is largely governed by the viscous transport of material through the disk, and yet remarkably few observational constraints exist on the physical mechanisms thought to drive accretion in these systems. The most commonly invoked transport mechanism in disks is an anomalous turbulent viscosity, driven by the magnetorotational instability; this predicts the presence of a subthermal magnetic field threading the disk. Submillimeter polarimetry is uniquely suited for constraining magnetic field strength and geometry, independent of disk structure, using the orientation of polarization vectors produced by dust grains aligned with the magnetic field. We have been carrying out an SMA program to test the first realistic models of polarized emission from circumstellar disks, recently calculated by Cho & Laziarian (2007). Our resolved observations of two of the brightest nearby disks, HD 163296 and TW Hydrae, place limits on the polarized flux up to a factor of five below the predicted values. With these firm limits, the most stringent yet obtained, we are working within the context of the Cho & Lazarian (2007) models to determine the physical conditions in the disk that are most likely to contribute to the suppression of polarized emission. We present the SMA observations and the results of modeling work to disentangle the processes responsible for this low polarization fraction. Arielle Moullet (CfA)Title: Mapping of SO_2 , SO and NaCl in Io's atmosphereAbstract: Jupiter's volcanic moon Io holds a very tenuous and spatially heterogeneous atmosphere, mainly composed of SO_2 , that was extensively observed and studied in the past 15 years. Millimeter wavelengths observations in particular, by measuring thermal emission in atmospheric rotational lines from the lowest atmospheric layers, can provide a direct access to physical characteristics such as gas temperature and column density. The use of interferometers as IRAM-Plateau de Bure (Moullet et al., 2008) and SMA, providing sufficient spatial resolution to resolve Io's disk (1.2"), can bring information on the gas distribution, and, by mapping line Doppler-shifts, on atmospheric dynamics. SMA observations of SO_2 , SO and NaCl lines around 346 GHz, obtained in four tracks in 2006 and 2008, will be presented. Given the spatial resolution obtained in the extended configuration (0.7"x0.8"), measurements of the position and spatial extent of these gases' thermal emission was performed, and could help to understand what is the main mechanism acting as a continuous replenishment source for these species. In agreement with other studies, several arguments appear to favor sublimation equilibrium with SO_2 frost on the ground as the main replenishment mechanism for thi species, while direct volcanic output could play a more important role for SO and NaCl supply. Doppler-shift mapping on a strong SO_2 line was performed for the 4 tracks, revealing high temporal wind patterns variations. On one track only the wind field is consistent with the approximatively 200 m/s fast prograde flow observed at PdBI in 2005. Another observed pattern could be interpreted as a day-side to night-side flow, which is expected in the context of a sublimation-driven atmosphere. On the other tracks, a strong North-South Doppler-shift gradient is measured, that could not be reproduced by plume dynamic simulations. Tyler Bourke (CfA), Phil Myers (CfA), James Di Francesco (HIA), Paola Caselli (Leeds), Rachel Friesen (U. Vic), Rene Plume (Calgary), David Wilner, Arnaud Belloche (MPIfR)Title: The Initial Conditions for Star Formation in ClustersAbstract: It is now well established that low-mass stars form from the collapse of dense cores within molecular clouds, and much of our knowledge of star formation has come from studies of relatively isolated dense cores. Yet isolated star formation is at best a simpler picture of the more relevant problem, how do stars form in clusters of 100 or more members, in a region extended over ~1 pc, in a time period of ~1 Myr, with a mass distribution following the initial mass function. With the Submillimeter Array and single-dish mm/submm telescopes we are undertaking high spectral and spatial resolution molecular line observations of dense starless cores within nearby cluster forming regions, with the goal of comparing the properties of cores in cluster-forming regions to those of isolated dense cores, and so address the fundamental question, What are the initial conditions for star formation in clusters? In this contribution we will present our latest results for three regions observed with the SMA, with particular focus on the core Oph A N6. Steve Longmore (CfA), Thushara Pillai (CfA), Jill Rathborne (CfA), Qizhou Zhang (CfA), Jim Jackson (BU)Title: Peering into the cradle of galactic superpowers: homing in on the physics of massive star formationAbstract: Massive stars dominate their environment wherever they are found. These galactic superpowers thus play a pivotal role in shaping the observable universe. In an effort to develop our understand of their formation process, we have previously derived the physical and kinematic properties of molecular and ionised gas towards 21 massive star formation regions. From the differences in these properties, we have determined the relative evolutionary stages of the cores within the 21 regions. Building upon these results, we have recently completed SMA observations towards six of the closest regions at different evolutionary stages at high enough continuum sensitivity and angular resolution to resolve down to the global Jeans mass/length of each region. I will present recent intriguing results from these observations to investigate the physics of massive star formation regions, in particular core fragmentation, as a function of time. Keping Qiu (CfA), Qizhou Zhang (CfA)Title: A High-resolution Observational View of Massive Molecular OutflowsAbstract: Molecular outflows are known to commonly involved in processes forming massive stars, yet their basic properties are not well understood. Using observations from the SMA as well as short spacing information from single-dish telescopes, we are carrying out a systemic study of massive molecular outflows at high-angular-resolution. Based on a moderate sample we find a tentative evolutionary scenario concerning both morphology and energetics of massive molecular outflows, presenting a striking contrast to what established from previous single-dish studies. Here we present showcases of well-collimated and wide-angle massive molecular outflows, as well as a more general picture synthesizing the entire sample. Roberto Galvan-Madrid (CfA, CRyA-UNAM, ASIAA), Qizhou Zhang, and Eric Keto (CfA) Luis F. Rodriguez, and Stan Kurtz (CRyA-UNAM) Paul T. P. Ho (ASIAA, CfA)Title Very Small HII Regions Embedded in Massive Accretion FlowsAbstract: We present preliminary results of an SMA+VLA study of a small sample of hypercompact and small ultracompact HII regions with evidence of accretion flows surrounding them. Molecular-line observations at a resolution of a few arcseconds reveal motions in the natal cores indicative of rotation, infall, and/or outflow at scales > 20 000 AU. Sub-arcsecond resolution data often reveal the presence of a small group of massive (proto)stars, usually at different evolutionary stages. The hypercompact HII regions with positive spectral index from cm to mm wavelengths are the smallest and most embedded. Their flattened molecular envelopes show evidence of rotation, infall, and/or outflow at scales < 10 000 AU. At the smallest observed scales (< 2000 AU) the ionized gas is found to have organized motions, probably in the form of rotation and/or outflow. Spectral-index modelling indicates the presence of density gradients in the ionized gas. Multiepoch observations of the free-free continuum reveal large flux variations in timescales of years; we attribute them to interactions with the surrounding molecular gas. All these observations favor a picture in which: i) massive (O stars, M>20 Msun) form by accretion; ii) accretion can continue past the onset of an HII region, probably for a short period of time; iii) immediately after the central star(s) have reached their final mass, the HII region is kept confined by its own molecular accretion flow. Hua-bai Li (CfA), Alyssa Goodman (CfA), Steven Longmore (CfA), T. K. Sridharan (CfA), Erik Rosolowsky (U. British Columbia), Dan Marrone (U. Chicago), Ram Rao (ASIAA)Title: Can We Say Something More about Cloud B-fields before ALMA?Abstract: Determining the role of magnetic fields is one of the critical problems in star and cloud formation. After about a decade of operation, both teams behind the polarimeters of CSO and JCMT will release their archives in 2009. I will quickly show two of their very important results: 1. the correlation between fields in cloud cores and fields in inter cloud media, and 2. the correlation between field orientations and core shapes. Both results indicate that B-field is dynamically important on scales of molecular clouds. Using SMA, we can do similar research on M33. I will show preliminary result of this project. As far as we know, this is the first polarimetry result from clouds in a somewhat face-on galaxy, which allows us to study possible effects that can not be observed inside the Milky Way. It is very important to test the two previous mentioned correlations with higher resolution, so we can test the importance of B-field on scales closer to the site of star formation. I will present a field morphology study of the cores in NGC 6334, which show interesting correlations between the core fields and the cloud fields, and between the core fields and the outflows. Ken Young (CfA), Nimesh A. Patel (CfA), Robert W. Wilson (CfA), Patrick Thaddeus (CfA) et al.Title: SMA Line Survey of IRC+10216 in the 345 GHz bandAbstract: A spectral-line survey of IRC+10216 has been carried out with the SMA, covering a substantial portion of the 300-355 GHz range of frequencies. This is the first interferometric line-survey of IRC +10216. The angular resolution is ~3" and the typical rms noise level is 0.1 Jy/beam. Compared to previous single-dish line-surveys at submillimeter wavelengths, the SMA line survey is at least four times more sensitive. A large fraction of the newly detected lines have narrow line-widths indicating expansion velocities of ~4 km/s. These lines arise in the inner envelope, within ~60 AU of the star, in the region of dust-formation where the stellar wind is still being accelerated. There are at least 20 lines that are as yet unassigned to known transitions in standard line-catalogs. Several new lines are identified as rotational transitions in vibrationally excited states of previously known molecules such as SiCC, SiS, CS and their isotopologues. Lines of high excitation levels of >3000 K, such as CS v=2 J=7-6 and CO v=1 J=3-2 remain spatially unresolved in follow-up SMA observations at 0.8", suggesting deconvolved source size of < 0.2". Future observations by ALMA will have much higher sensitivity and angular resolution, up to 15 mas at 1 mm wavelength in its longest baseline configuration, allowing detailed studies of the dynamics and physical conditions of gas close to the stellar surface. D. Espada (CfA, IAA-CSIC)Title: SMA CO(2-1) BODEGA (Below 0 DEgree GAlaxies)Abstract: In this talk I will present a pilot study we are carrying out at SMA to image the circumnuclear regions (1 arcmin) of $\sim$ 30 CO-bright nearby galaxies in the southern hemisphere (-45 $<$ dec $<$ 0 degrees). The sample is mainly composed of late type spirals that have likely suffered a recent and relatively minor interaction (as traced by their IR brightness, optical asymmetries, dust lanes, etc.), and that likely represents the bulk of galaxies that are in an intermediate environmental density. The lack of mm/submm interferometers that can efficiently reach the southern hemisphere has prevented to study with high resolution the molecular gas properties of many of these interesting galaxies in the southern sky, but are now accesible with the advent of SMA. We have detected not only their CO(2-1) line, but also their 13CO and a few cases even C18O. I will present preliminar results about the molecular gas properties in such galaxies, from the variety of molecular gas morpho! logical types found (rings, arms, concentration, asymmetries) as well as the kinematics and physical conditions. We will also inspect the role of the circumnuclear molecular gas properties on the occurrence of starburst and/or nuclear activity episodes. This study will provide potential good candidates to be observed in the ALMA early science. Sergio Martin (CfA)Title: Chemical composition in galactic nuclei: From the Galactic center to ULIRGsAbstract: The study of the chemical composition has been shown to be a powerful tool to peer into the heavily obscured galactic nuclei in order to in vestigate the main power source (SB and/or AGN) leading the observed luminosity. This is particularly important in ultraluminous infrared galaxies whose elusive nuclei are severely obscured even in the far-infrared. I will present a review of the latest results on the chemical understanding of galaxies based on SMA observations. Special attention will be paid to two main topics. First, the impact of molecular line surveys which provide an overall view of the chemical complexity of the ISM within the central few hundred parsecs of galaxies. Line surveys has allowed the detection of up to 40 molecular species outside the Milky Way, and are the basis for a chemical classification of galaxies. On the other hand, i will focus on high resolution imaging of key molecular species both in the Galactic center and in prototypical galaxies. Mapping different key molecules allows us to trace the different ISM components affected by different heating mechanisms. A few thoughts and prospects will be given concerning the possibilities that the extra resolution and sensitivity of ALMA will provide. However, emphasis will be put on the possibilities of current instruments such as SMA towards the Galactic center and nearby prototypical galaxies. Joshua D. Younger (CfA), Giovanni G. Fazio (CfA), David Wilner (CfA), Jiasheng Huang (CfA), Min S. Yun (U. Mass), Grant W. Wilson (U. Mass)Title: What can we learn about submillimeter galaxies from high resolution interferometric imaging?Abstract: Over the past decade, it has become clear that a significant fraction of the far infrared extragalactic background is produced by high redshift starbursts. First revealed by SCUBA at the JCMT, submillimeter galaxies are now known to be massive, dusty, extremely luminous merging systems that may represent massive galaxies in formation. However, a detailed understanding of these objects has been hindered in part by the relatively poor resolution of submillimeter cameras. Over the past couple of years, we have used the Submillimeter Array to follow up the brightest 1.1mm sources detected by the AzTEC Camera. This has produced a flux-limited sample of 15 SMGs with 2 arcsec resolution (positions accurate to ~0.2 arcsec) that enable counterpart identification at other wavelengths observed with similarly high angular resolution. These unambiguous counterparts provide evidence for a population of extremely luminous systems at higher redshift (z > 3.5) than more commonly studied samples; a result that could have important consequences for models of galaxy formation and evolution. At the same time, recent imaging at even higher resolution (~0.3 arcsec, or 3x better) has provided measurements of the physical scale of the far infrared emission in two of the most luminous SMGs known. By way of a series of simplifying assumptions, we find evidence that these z~4 hyperluminous starbursts are radiating at close to or at their Eddington limit, and may constrain models of star formation and feedback in the most extreme environments. Mark Gurwell (CfA)Title: The SMA Flux Density Database: Millimeter/Submillimeter Lightcurves of QuasarsAbstract: The SMA maintains a unique and accessible online database of the 1.3 mm and 850 micron flux density history of over four hundred quasars, stretching back to 2003. The database currently includes more than 10600 indpendent measurements, and grows at an average rate of more than 2400 new measurements per year. While this is a service we provide to assist in the preparation of observation scripts and calibration of SMA science data (quasars are typically used for gain calibration), the database is also a rich trove of data useful for studying the time evolution of these powerful sources, particularly when combined with multiwavelength data such as from Chandra, Fermi, and the VLA. A few examples of the interesting science being done with the SMA in this field will be shown. Diego Munoz (CfA), D. Marrone (U. Chicago), J. Moran (CfA)Title: Detection of Circular Polarization from Sgr A* at Submillimeter WavelengthsAbstract: We report the detection of circularly polarized (CP) emission from the compact radio source Sagittarius A* at a level of 1.5% at a frequency of 235 GHz (1.4 mm). Sgr A* is associated with the supermassive black hole (SMBH) in the Galactic Center. The observations, taken with the Submillimeter Array (SMA) on 03/31/2007, also show a linearly polarized (LP) component of ~7%. The snr of our detection of CP is about 14. Before our measurements, CP had only been detected at frequencies between 1.4 and 15 GHz (21 and 2 cm) at levels <1%. In the same frequency range, LP has never been detected to a limit of 0.3%. Throughout our track, the sign of CP remains the same, indicating a consistent coherent production of CP. Previous polarization and variability studies of Sgr A* have supported a two-layer scenario of source plus cold plasma screen, in which Faraday rotation in the stationary screen (constant RM)acts on a time variable background source. A cold, optically thin plasma screen cannot be responsible for both a constant RM and Faraday conversion from LP to CP, therefore the observed amounts of CP are likely to be originated close to the central source. Sgr A* shows a flat-to-inverted radio spectrum and a submillimeter excess referred to as the "submillimeter bump". This excess it thought to come from the closest regions to the SMBH. In such a scenario, millimeter wavelength data is associated with regions in which the material is likely to be relativistic and the magnetic field ordered. We have carried out polarized radiative transfer calculations exploring different combinations of ordered and stochastic magnetic fields looking for a favored scenario that can explain the apparent constant increase of CP with frequency as well as the sudden jump in LP between 40 and 80 GHz. Jonathan Weintroub (CfA), Sheperd Doeleman (MIT Haystack), James Moran (CfA), Kenneth Young (CfA), Rurik Primiani (CfA) et al.Title: VLBI with the SMA: The Event Horizon of SgrA*Abstract: There is now very strong evidence that SgrA*, the compact source of radio, IR, and x-ray emission at the Galactic Center, eight kilo- parsecs away, marks the position of a four million solar mass black hole. Very Long Baseline Interferometry (VLBI) has the potential to probe, and eventually to image, emission from the innermost accretion region. This requires pushing the VLBI technique to submillimeter wavelengths where fringe spacings are of the order of the angular size of the Schwarzschild radius, and where scattering by the ionized ISM is greatly reduced. Thus intrinsic structure right at the event horizon can be directly observed. VLBI observations in April 2007 at a wavelength of 1.3 mm have now confirmed structure in SgrA* on scales of just a few Schwarzschild radii. More sensitive observations are planned in the next few years, and could detect time variable structures predicted by models of flaring activity in SgrA*. A key improvement in sensitivity is provided by the recent deployment and commissioning of a VLBI phased array processor at the SMA. This new instrument enables the SMA and the neighboring single dish submillimeter telescopes (CSO and JCMT) to contribute to future VLBI observations with all their collecting area. We also plan to add additional stations and over the next decade to assemble an 'Event Horizon Telescope' bringing a variety of existing submillimeter facilities, as well as those under construction into our VLBI array. This talk will describe what current and future submillimeter VLBI observations, enabled by new instrumentation, tell us about our neighboring super-massive black hole. Jun-Hui Zhao (CfA), Ray Blundell (CfA), James M. Moran (CfA) D. Downes (IRAM), Karl F. Schuster (IRAM) Dan Marrone (U. Chicago)Title: The Ionized Gas in The Central Parsec of The GalaxyAbstract: We report new results based on the observations of the H30a line emission at 1.3 mm from the central 1.5-parsec region of the Galactic center with the Submillimeter Array in a resolution of 2 arcsec. We measure the velocity profiles over the central 1' (radius of 1 parsec) of the Galactic Center region, which encompassed most of the mini-spiral. We developed an isothermal, homogeneous HII model in order to understand the physical conditions of the ionized gas in the mini-spiral arms. We show that the physical quantities, such as the kinetic temperature and electron density, are well constrained by the H30a line data together with the VLA data from both the H92a line at 3.6 cm and radio continuum emission at 1.3 cm. We also construct the 3D Cartesian geometry of the mini-spiral structure using the orbital parameters derived under the assumption that the three mini-spiral flows are in Keplerian motion. We show that the ionized flow in the Eastern Arm collides with the Northern Arm in the Bar region which located a few tenth parsec S of and behind Sgr A*. In comparison with the model, the H30a data shows that the ionized flows in the mini-spiral arms are dominated by the Keplerian motions around Sgr A* with a mass of 4.2 million solar masses. However, we have also observed that kinematics in some regions deviate significantly from the Keplerian motions. We will discuss possible sources that cause non-Keplerian motions. In addition, we will discuss the ionization and a possible connection between the ionized gas and the young massive stars found in IR recently. Chunhua Qi (CfA), D. J. Wilner (CfA), Y. Aikawa (Kobe U.), G.A. Blake (Caltech), M.R. Hogerheijde (Leiden U.), S.M. Andrews (CfA), A.M. Hughes (CfA)Title: Deuterium Fractionation in Protoplanetary DisksAbstract: Deuterated molecule chemistry is sensitive to the temperature history of interstellar and circumstellar gas, and observations of deuterated species can constrain the origin of primitive solar system bodies such as comets and other icy planetesimals. We present Submillimeter Array observations of the HCO+, DCO+, HCN and DCN J=3-2 lines in the disks around the K8V star TW Hya and the A1V star HD 163296 at arcsecond scales. We constrain the radial and vertical distributions of various species using a model where the molecular emission from an irradiated accretion disk is sampled with a 2D Monte Carlo radiative transfer code. We find enhanced molecular D/H ratios in both disks, and we attribute these enhancements to different processes. In the cold disk of TW Hya, the DCO+/HCO+ ratio increases with increasing radius due to low temperatures far from the star, as expected from low-temperature gas-phase deuterium fractionation processes. In the warm disk of HD 163296, these processes should be prohibited. The detailed processes leading to such high abundance of DCO+ is still unknown. Tyler Bourke (CfA), Jes Jorgensen (MPIfR), Shige Takakuwa (ASIAA) et al.Title: A Multi-wavelength SMA study of the protobinary IRAS 16293-2422Abstract: Over the past 4 years we have observed the nearby protobinary system IRAS 16293-2422 (160 pc) in a number of spectral setups with the SMA. A multititude of lines have been identified and imaged using observations in the 230, 345 and 690 GHz bands, using compact array data, including many deuterated species and complex organic molecules. At higher resolution, source A has been resolved into two components at 354 and 690 GHz, confirming the discovery result of Chandler et al. (2005; SMA 300 GHz), allowing us to determine the spectral index of each component. This contribution will present a brief summary of works already published, and an update on progress on the larger datasets. Jes Jorgensen (AIfA, Univ. Bonn), Tyler Bourke, David Wilner, Phil Myers (CfA), Ewine van Dishoeck (Leiden), Ruud Visser (Leiden), Dave Lommen (Leiden), Michiel Hogerheijde (Leiden)Title: Tracing the Evolution of Envelopes, Disks and Stars during the Embedded Stages of Low-Mass ProtostarsAbstract: We present the results from a large survey of 20 Class 0 and I low-mass protostars using the Submillimeter Array. The high angular resolution dust continuum observations in concert with larger-scale single-dish maps and detailed multi-dimensional radiative transfer models constrain the physical structures, including masses, of the protostellar disks and envelopes. Line observations of the disks around the more evolved Class I systems reveal rotational signatures which in turn constrain the central stellar masses. Together these observations allow us to trace evolution of the mass of the stars, disks and envelopes through these pivotal stages in the lifes of young stars. In comparison to classical models for protostellar collapse, the data paint a picture in which disks form early in the evolution of young low-mass stars: the inferred masses of the central disks are comparable for both Class 0 and I protostars, which suggests that disks are formed and grow to significant sizes early in the evolution of the protostars, but also are very efficient in channeling matter onto the central stars. Thushara Pillai (CfA)Title: The Internal Structure of High Mass Pre-protoclustersAbstract: The earliest phase in the formation of a high mass star would be a ``pre-protocluster stage'', which is hard to find. In spite of various efforts to spot them, there is no bona fide high mass pre- protocluster core yet! The knowledge of their properties is crucial in establishing an evolutionary paradigm and constraining any theoretical calculations on collapse. With the SMA we launched a large survey of candidate pre-protocluster cores that are massive, cold, very dense, highly deuterated and depleted in line and dust continuum. In order to understand the initial conditions, we study the velocity structure, excitation, stability, fragmentation, deuteration, and depletion in the cores. It is the result of this study that I will present in the talk. Without giving away much of the exciting results, we find that they are largely unexpected. For example, fragmentation appears not to be constrained by thermal pressure alone. Yet another example, in contrast to previous claims on the kinematic structure, high mass pre-protocluster regions have low core to core velocity dispersions. These pose challenges for one of the major theoretical models for the formation of massive stars. Jingwen Wu (CfA)Title: A SMA view of infall in massive star forming regionsAbstract: Recently, infall in massive star forming regions has been generally revealed by certain spectral line surveys using single-dish telescopes. But few sources have been followed-up with interferometers. In the single-dish surveys, we have found that HCN 3-2 and HCO+ 3-2 are good molecular infall tracers in high-mass star forming regions. We have conducted a project to use the SMA to study dynamics, especially infall, in cluster forming scales, following up some good massive infall candidates revealed by single-dish observations. A small sample of massive star forming regions with different evolutionary stages have been mapped with the SMA. With the wide 2GHz IF band of the SMA, HCN 3-2 and HCO+ 3-2, together with some other lines, were obtained simultaneously. Current result shows that the real case of infall revealed by high-resolution observation is more complex than seen from single-dishes. I will report the primary result of the study in this poster. Lei Zhu (CfA), Jun-Hui Zhao (CfA), M. Wright (Berkeley), Yue-Fang Wu (Peking University)Title: Outflows and Infall in W3-SEAbstract: We report the results from observations of W3-SE with the SMA, CARMA and JCMT. Located 2 kpc away, W3-SE is an intermediate-mass molecular core southeast to the high-mass star formation region W3-Main. Based on the measurements of flux densities of mm/sub-mm along with the Spitzer data at mid-IR wavelengths, the SED of the dust emission from W3-SE was determined and fitted with a two-component dust thermal model. Our best fitting suggested the presence of a dominant cold dust component with Td = 34 +/- 2 K and M = 180 +/- 70 Msun , as well as a mid-IR bump indicating that a small fraction of the dust has been heated in the core. The complex of the kinematics derived from the observations of HCO+ (1-0) line with the CARMA in resolution of 6 arcsec suggest that multiple outflows are present in this core. In 1-mm continuum, the SMA resolves W3-SE into two dust emission peaks (referred as SMA1 and SMA2 hereafter), which are separated by 3 arcsec. The primary one SMA1 is associated with a compact mid-IR source, and SMA2 is associated with extended mid-IR emission and a potential mid-IR jet. We will also show the preliminary results from the SMA observations in HCN(3-2), HCO+ (3-2), N2 H+ (3-2) and CH3OH lines. The spectra of HCN(3-2) show very broad line wings (> 40 km/s) near SMA1, suggesting a high-energy compact outflow in NE-SW driven by the energy source in SMA1. A similar but weaker detection has been made in HCO+ (3-2). We also detected a large-scale HCO+ (3-2) outflow which is perpendicular to the compact one and consistent with the previous CARMA observations. In addition, we also detect significant self-absorption in the line profiles of HCN(3-2) and HCO+(3-2) over the whole region, and in the N2 H+(3-2) spectra near the position of the SMA1. Such self-absorption features are red-shifted to the single emission peak of CH3OH(5,2,3-4,1,3) line. This could be an evidence for infall toward SMA1, although we need higher-resolution observations to verify this conclusion. Fred Baganoff (MIT), Dan Marrone (U. Chicago), and Jim Moran (CfA)Title: An Apparent Correlation Between the X-ray to NIR Flux Ratio and Submm Lag in Sgr A* FlaresAbstract: Sgr A* is a radio, IR, and X-ray source associated with an ~ 3.7 million solar mass black hole at the center of the Milky Way. It is extremely under-luminous, radiating at ~ $10^{-9}$ Eddington, either because the accretion rate is very low or because the accretion flow is radiatively inefficient, or both. Sgr A* flares daily at random intervals in the X-ray (Baganoff et al. 2001), NIR (Ghez et al. 2004), and mm/ submm (Marrone, 2008; Mauerhan et al. 2005). The origin of these flares is under vigorous debate. Some models propose that a weak jet is radiatively dominant, while others counter that the flares originate in a magnetized rotating plasma. In either case, the flares must originate from the inner few Schwarzschild radii, thus providing an unique probe of the physical environment just outside the event horizon of the nearest supermassive black hole. Several multiwavelength monitoring campaigns have been performed over the past six years to study these flares. Here we report observations and analyses of the first two flares with simultaneous monitoring in the X-ray, NIR, and submm (Marrone et al. 2008). The first flare occurred on 2005 July 31 and the second on 2006 July 17. Using an adiabatically expanding relativistic plasmon model (e.g., van der Laan 1966), we show that the X-ray-to-NIR flux ratio or inverse compton-to-synchrotron flux ratio and the lag of the peak flux of the submm light curve are related through the electron column density ($n_{e}R$) of the plasma bubble, where $n_{e}$ is the electron density and R is the radius of the bubble. Future monitoring campaigns will test the proposed correlation and determine the scaling parameters for the dynamical evolution of the electron density, size, and magnetic field of the plasma bubbles. Simultaneous fits to the temporally evolving spectra, fluxes, and polarization properties with realistic time-dependent shock/particle-acceleration codes may ultimately determine whether the flares originate in a jet or a magnetized rotating accretion flow. Rurik Primiani (CfA), Jonathan Weintroub (CfA), Ken Young (CfA), Sheperd Doeleman (MIT), John Test (CfA), James Moran (CfA), Chris Schaab (CfA)Title: A VLBI Phased Array Processor for the SMAAbstract: A phased-array processor is being deployed on Mauna Kea to allow the Submillimeter Array (SMA), and neighboring observatories (James Clerk Maxwell Telescope, JCMT, and Caltech Submillimeter Observatory, CSO) to participate, as a single station, in high frequency VLBI observations. A highly successful 1.3 mm observation of the Galactic Center radio source, SgrA* in April 2007 used just the JCMT on Mauna Kea and stations in California and Arizona. This observation reinforced the need to aggregate the available collecting area on Mauna Kea, since no detection was then obtained on the California-Hawaii baseline. The phased array coherently sums the signals from either eight SMA antennas, for a physical collecting area of 226 square meters, or six SMA antennas plus the JCMT, and CSO, for a collecting area of 424 square meters. A VLBI campaign is planned for early April 2009 to once again observe SgrA*, this time using the phased array to provide substantially increased sensitivity on the baselines to Hawaii. A detection on the full triangle of baselines would allow sensitive discrimination between competing models of intrinsic source structure. We will describe the design and capabilities of the new SMA VLBI Phased Array Processor, and report on operational tests of its performance, and its first use in observations. Abby Hedden (CfA)Title: New 660 GHz SIS Devices for SMA MixersAbstract: We have established a collaboration with the University of Cologne for the development and production of new SIS devices for the 600 GHz SMA mixers. We have designed a series of SIS devices with end-loaded stub integrated tuning circuits optimized for operation in the 640 - 700 GHz range. All designs consist of similar junction geometries (1.1 um diameter junction areas, Jc = 12 kA/cm2, 150 nm Nb groundplane, 250 nm SiO dielectric, 350 nm Nb wiring layer) and all devices were fabricated on fused quartz substrate. Two RF probe designs were investigated for use with the new devices (Loudkov et al. 2005, Zhang et al. 2003) in the 600 GHz SMA mixer waveguide environment using CST MWS. Since this wafer run was intended to produce robust replacements for existing 600 GHz mixers in the field, the standard SMA RF probe design (Zhang et al. 2003) was selected. Six device designs were optimized and a design layout was completed in May - June 2008. The fabricated wafer arrived at CfA in November, 2008 and further wafer processing, including lapping and dicing, has been ongoing at the CfA since January 2009. To date, we have achieved reasonable success in lapping the fused quartz chips reproducibly to the designed thickness (1.5 mils) within the required tolerance (+/- 0.1 mil) and dicing devices with high yield. Within the past several weeks, we have begun to diptest devices from this wafer run after lapping and dicing. The results compare favorably with device characteristics measured in Cologne, indicating that post-processing procedures are not affecting the device quality. We further characterized the performance of different devices (we have tested 3 designs so far) over the 630 - 690 GHz range. These measurements have made use of the lab's receiver test setup (incorporating a liquid-cooled cryostat) and further characterization in an SMA cryostat is forthcoming. Initial results are very encouraging. We have achieved receiver noise temperatures of about 140 K at 660 GHz, comparable to if not slightly improved over the performance of current SMA mixers (< 200 K Trec in the lab test cryostat at 660 GHz). One of these devices has been selected for incorporation into the SMA cryostat that will be shipped to Hawaii within the next several months. If further characterization shows improved performance, then new devices may be incorporated into 600 GHz SMA mixers before the end of the year. | |
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