The Alignment of the Magnetic Field and Collimated Outflows in Star-forming Regions: the Case of NGC 2071

The magnetic field is believed to play a crucial role in the process of star formation. From the support it provides during the initial collapse of molecular clouds to the creation of strong collimated jets responsible for large mass losses, current theories predict its importance in many different stages during the formation of stars. Here we report on observational evidence which tests one aspect that can be inferred from these theories: the alignment between the local magnetic field and collimated bipolar outflows in such environments. There is good evidence of an alignment in the case of NGC 2071.Comment: 11 pages, 4 figure

Wing Musculature Reconstruction in Extinct Flightless Auks (<i>Pinguinus</i> and <i>Mancalla</i>) Reveals Incomplete Convergence with Penguins (Spheniscidae) Due to Differing Ancestral States.

Despite longstanding interest in convergent evolution, factors that result in deviations from fully convergent phenotypes remain poorly understood. In birds, the evolution of flightless wing-propelled diving has emerged as a classic example of convergence, having arisen in disparate lineages including penguins (Sphenisciformes) and auks (Pan-Alcidae, Charadriiformes). Nevertheless, little is known about the functional anatomy of the wings of flightless auks because all such taxa are extinct, and their morphology is almost exclusively represented by skeletal remains. Here, in order to re-evaluate the extent of evolutionary convergence among flightless wing-propelled divers, wing muscles and ligaments were reconstructed in two extinct flightless auks, representing independent transitions to flightlessness: Pinguinus impennis (a crown-group alcid), and Mancalla (a stem-group alcid). Extensive anatomical data were gathered from dissections of 12 species of extant charadriiforms and 4 aequornithine waterbirds including a penguin. The results suggest that the wings of both flightless auk taxa were characterized by an increased mechanical advantage of wing elevator/retractor muscles, and decreased mobility of distal wing joints, both of which are likely advantageous for wing-propelled diving and parallel similar functional specializations in penguins. However, the conformations of individual muscles and ligaments underlying these specializations differ markedly between penguins and flightless auks, instead resembling those in each respective group's close relatives. Thus, the wings of these flightless wing-propelled divers can be described as convergent as overall functional units, but are incompletely convergent at lower levels of anatomical organization-a result of retaining differing conditions from each group's respective volant ancestors. Detailed investigations such as this one may indicate that, even in the face of similar functional demands, courses of phenotypic evolution are dictated to an important degree by ancestral starting points

IRC+10216's Innermost Envelope -- The eSMA's View

We used the Extended Submillimeter Array (eSMA) in its most extended configuration to investigate the innermost (within a radius of 290 R* from the star) circumstellar envelope (CSE) of IRC+10216. We imaged the CSE using HCN and other molecular lines with a beam size of 0."22 x 0."46, deeply into the very inner edge (15 R*) of the envelope where the expansion velocity is only 3 km/s. The excitation mechanism of hot HCN and KCl maser lines is discussed. HCN maser components are spatially resolved for the first time on an astronomical object. We identified two discrete regions in the envelope: a region with a radius of . 15 R*, where molecular species have just formed and the gas has begun to be accelerated (region I) and a shell region (region II) with a radius of 23 R* and a thickness of 15 R*, whose expansion velocity has reached up to 13 km/s, nearly the terminal velocity of 15 km/s. The Si$^{34}$S line detected in region I shows a large expansion velocity of 16 km/s due to strong wing components, indicating that the emission may arise from a shock region in the innermost envelope. In region II, the P.A. of the most copious mass loss direction was found to be 120 +/- 10 degrees, which may correspond to the equatorial direction of the star. Region II contains a torus-like feature. These two regions may have emerged due to significant differences in the size distributions of the dust particles in the two regions.Comment: 26 pages, 8 figures, accepted for publication in The Astrophysical Journal. Please find the pdf at http://www.submm.caltech.edu/~hs/astroph/0904.0280.pdf and the ps file at http://www.submm.caltech.edu/~hs/astroph/0904.0280.p

Open-closed homotopy algebra in mathematical physics

In this paper we discuss various aspects of open-closed homotopy algebras (OCHAs) presented in our previous paper, inspired by Zwiebach's open-closed string field theory, but that first paper concentrated on the mathematical aspects. Here we show how an OCHA is obtained by extracting the tree part of Zwiebach's quantum open-closed string field theory. We clarify the explicit relation of an OCHA with Kontsevich's deformation quantization and with the B-models of homological mirror symmetry. An explicit form of the minimal model for an OCHA is given as well as its relation to the perturbative expansion of open-closed string field theory. We show that our open-closed homotopy algebra gives us a general scheme for deformation of open string structures ($A_\infty$-algebras) by closed strings ($L_\infty$-algebras).Comment: 38 pages, 4 figures; v2: published versio

The eSMA: description and first results

The eSMA ("extended SMA") combines the SMA, JCMT and CSO into a single facility, providing enhanced sensitivity and spatial resolution owing to the increased collecting area at the longest baselines. Until ALMA early science observing (2011), the eSMA will be the facility capable of the highest angular resolution observations at 345 GHz. The gain in sensitivity and resolution will bring new insights in a variety of fields, such as protoplanetary/transition disks, high-mass star formation, solar system bodies, nearby and high-z galaxies. Therefore the eSMA is an important facility to prepare the grounds for ALMA and train scientists in the techniques. Over the last two years, and especially since November 2006, there has been substantial progress toward making the eSMA into a working interferometer. In particular, (i) new 345-GHz receivers, that match the capabilities of the SMA system, were installed at the JCMT and CSO; (ii) numerous tests have been performed for receiver, correlator and baseline calibrations in order to determine and take into account the effects arising from the differences between the three types of antennas; (iii) first fringes at 345 GHz were obtained on August 30 2007, and the array has entered the science-verification stage. We report on the characteristics of the eSMA and its measured performance at 230 GHz and that expected at 345 GHz. We also present the results of the commissioning and some initial science-verification observations, including the first absorption measurement of the C/CO ratio in a galaxy at z=0.89, located along the line of sight to the lensed quasar PKS1830-211, and on the imaging of the vibrationally excited HCN line towards IRC+10216.Comment: 12 pages, 7 figures, paper number 7012-12, to appear in Proceedings of SPIE vol. 7012: "Ground-based and Airborne Telescopes II", SPIE conference on Astronomical Instrumentation, Marseille, 23-28 June 200

Detection of CI in absorption towards PKS 1830-211 with the eSMA

We report the first science observations and results obtained with the "extended" SMA (eSMA), which is composed of the SMA (Submillimeter Array), JCMT (James Clerk Maxwell Telescope) and CSO (Caltech Submillimeter Observatory). Redshifted absorptions at z=0.886 of CI (^3P_1 - ^3P_0) were observed with the eSMA with an angular resolution of 0.55"x0.22" at 1.1 mm toward the southwestern image of the remarkable lensed quasar PKS 1830-211, but not toward the northeastern component at a separation of ~1". Additionally, SMA observations of CO, 13CO and C18O (all J=4-3) were obtained toward this object: CO was also detected toward the SW component, but none of the isotopologues were. This is the first time [CI] is detected in this object, allowing the first direct determination of relative abundances of neutral atomic carbon to CO in the molecular clouds of a spiral galaxy at z>0.1. The [CI] and CO profiles can be decomposed into two and three velocity components respectively. We derive C/CO column density ratios ranging from <0.5 (representative of dense cores) to ~2.5 (close to translucent clouds values). This could indicate that we are seeing environments with different physical conditions or that we are witnessing chemical evolution of regions where C has not completely been converted into CO.Comment: 6 pages using emulateapj, 3 tables, 2 figures ; accepted for publication in ApJ

SWCam: the short wavelength camera for the CCAT Observatory

We describe the Short Wavelength Camera (SWCam) for the CCAT observatory including the primary science drivers, the coupling of the science drivers to the instrument requirements, the resulting implementation of the design, and its performance expectations at first light. CCAT is a 25 m submillimeter telescope planned to operate at 5600 meters, near the summit of Cerro Chajnantor in the Atacama Desert in northern Chile. CCAT is designed to give a total wave front error of 12.5 μm rms, so that combined with its high and exceptionally dry site, the facility will provide unsurpassed point source sensitivity deep into the short submillimeter bands to wavelengths as short as the 200 μm telluric window. The SWCam system consists of 7 sub-cameras that address 4 different telluric windows: 4 subcameras at 350 μm, 1 at 450 μm, 1 at 850 μm, and 1 at 2 mm wavelength. Each sub-camera has a 6’ diameter field of view, so that the total instantaneous field of view for SWCam is equivalent to a 16’ diameter circle. Each focal plane is populated with near unit filling factor arrays of Lumped Element Kinetic Inductance Detectors (LEKIDs) with pixels scaled to subtend an solid angle of (λ/D)2 on the sky. The total pixel count is 57,160. We expect background limited performance at each wavelength, and to be able to map < 35(°)2 of sky to 5 σ on the confusion noise at each wavelength per year with this first light instrument. Our primary science goal is to resolve the Cosmic Far-IR Background (CIRB) in our four colors so that we may explore the star and galaxy formation history of the Universe extending to within 500 million years of the Big Bang. CCAT's large and high-accuracy aperture, its fast slewing speed, use of instruments with large format arrays, and being located at a superb site enables mapping speeds of up to three orders of magnitude larger than contemporary or near future facilities and makes it uniquely sensitive, especially in the short submm bands

1.6:1 bandwidth two-layer antireflection structure for silicon matched to the 190–310 GHz atmospheric window

Although high-resistivity, low-loss silicon is an excellent material for terahertz transmission optics, its high refractive index necessitates an antireflection treatment. We fabricated a wide-bandwidth, two-layer antireflection treatment by cutting subwavelength structures into the silicon surface using multi-depth deep reactive-ion etching (DRIE). A wafer with this treatment on both sides has <−20  dB (<1%) reflectance over 187–317 GHz at a 15° angle of incidence in TE polarization. We also demonstrated that bonding wafers introduce no reflection features above the −20  dB level (also in TE at 15°), reproducing previous work. Together these developments immediately enable construction of wide-bandwidth silicon vacuum windows and represent two important steps toward gradient-index silicon optics with integral broadband antireflection treatment

1.6:1 bandwidth two-layer antireflection structure for silicon matched to the 190–310 GHz atmospheric window

Although high-resistivity, low-loss silicon is an excellent material for terahertz transmission optics, its high refractive index necessitates an antireflection treatment. We fabricated a wide-bandwidth, two-layer antireflection treatment by cutting subwavelength structures into the silicon surface using multi-depth deep reactive-ion etching (DRIE). A wafer with this treatment on both sides has <−20  dB (<1%) reflectance over 187–317 GHz at a 15° angle of incidence in TE polarization. We also demonstrated that bonding wafers introduce no reflection features above the −20  dB level (also in TE at 15°), reproducing previous work. Together these developments immediately enable construction of wide-bandwidth silicon vacuum windows and represent two important steps toward gradient-index silicon optics with integral broadband antireflection treatment