A molecular shell with star formation toward the supernova remnant G349.7+0.2

A field of ~38'x38' around the supernova remnant (SNR) G349.7+0.2 has been surveyed in the CO J=1-0 transition with the 12 Meter Telescope of the NRAO, using the On-The-Fly technique. The resolution of the observations is 54". We have found that this remnant is interacting with a small CO cloud which, in turn, is part of a much larger molecular complex, which we call the ``Large CO Shell''. The Large CO Shell has a diameter of about 100 pc, an H_2 mass of 930,000 solar masses, and a density of 35 cm-3. We investigate the origin of this structure and suggest that an old supernova explosion ocurred about 4 million years ago, as a suitable hypothesis. Analyzing the interaction between G349.7+0.2 and the Large CO Shell, it is possible to determine that the shock front currently driven into the molecular gas is a non-dissociative shock (C-type), in agreement with the presence of OH 1720 MHz masers. The positional and kinematical coincidence among one of the CO clouds that constitute the Large CO Shell, an IRAS point-like source and an ultracompact H II region, indicate the presence of a recently formed star. We suggest that the formation of this star was triggered during the expansion of the Large CO Shell, and suggest the possibility that the same expansion also created the progenitor star of G349.7+0.2. The Large CO Shell would then be one of the few observational examples of supernova-induced star formation.Comment: accepted in Astronomical Journal, corrected typo in the abstract (in first line, 38' instead of 38"

Absolute calibration and beam reconstruction of MITO (a ground-based instrument in the millimetric region)

An efficient sky data reconstruction derives from a precise characterization of the observing instrument. Here we describe the reconstruction of performances of a single-pixel 4-band photometer installed at MITO (Millimeter and Infrared Testagrigia Observatory) focal plane. The strategy of differential sky observations at millimeter wavelengths, by scanning the field of view at constant elevation wobbling the subreflector, induces a good knowledge of beam profile and beam-throw amplitude, allowing efficient data recovery. The problems that arise estimating the detectors throughput by drift scanning on planets are shown. Atmospheric transmission, monitored by skydip technique, is considered for deriving final responsivities for the 4 channels using planets as primary calibrators.Comment: 14 pages, 6 fiugres, accepted for pubblication by New Astronomy (25 March

The chemistry of C3 & Carbon Chain Molecules in DR21(OH)

(Abridged) We have observed velocity resolved spectra of four ro-vibrational far-infrared transitions of C3 between the vibrational ground state and the low-energy nu2 bending mode at frequencies between 1654--1897 GHz using HIFI on board Herschel, in DR21(OH), a high mass star forming region. Several transitions of CCH and c-C3H2 have also been observed with HIFI and the IRAM 30m telescope. A gas and grain warm-up model was used to identify the primary C3 forming reactions in DR21(OH). We have detected C3 in absorption in four far-infrared transitions, P(4), P(10), Q(2) and Q(4). The continuum sources MM1 and MM2 in DR21(OH) though spatially unresolved, are sufficiently separated in velocity to be identified in the C3 spectra. All C3 transitions are detected from the embedded source MM2 and the surrounding envelope, whereas only Q(4) & P(4) are detected toward the hot core MM1. The abundance of C3 in the envelope and MM2 is \sim6x10^{-10} and \sim3x10^{-9} respectively. For CCH and c-C3H2 we only detect emission from the envelope and MM1. The observed CCH, C3, and c-C3H2 abundances are most consistent with a chemical model with n(H2)\sim5x10^{6} cm^-3 post-warm-up dust temperature, T_max =30 K and a time of \sim0.7-3 Myr. Post warm-up gas phase chemistry of CH4 released from the grain at t\sim 0.2 Myr and lasting for 1 Myr can explain the observed C3 abundance in the envelope of DR21(OH) and no mechanism involving photodestruction of PAH molecules is required. The chemistry in the envelope is similar to the warm carbon chain chemistry (WCCC) found in lukewarm corinos. The observed lower C3 abundance in MM1 as compared to MM2 and the envelope could be indicative of destruction of C3 in the more evolved MM1. The timescale for the chemistry derived for the envelope is consistent with the dynamical timescale of 2 Myr derived for DR21(OH) in other studies.Comment: 11 Pages, 6 figures, accepted for publication in A&

Theoretical HDO emission from low-mass protostellar envelopes

We present theoretical predictions of the rotational line emission of deuterated water in low-mass protostar collapsing envelopes. The model accounts for the density and temperature structure of the envelope, according the inside-out collapse framework. The deuterated water abundance profile is approximated by a step function, with a low value in the cold outer envelope and a higher value in the inner envelope where the grain mantles evaporate. The two abundances are the two main parameters of the modeling, along with the temperature at which the mantles evaporate. We report line flux predictions for a 30 and 5 L$_\odot$ source luminosity respectively. We show that ground based observations are capable to constrain the three parameters of the model in the case of bright low-mass protostars (L$>$10 L$_{\odot}$), and that no space based observations, like for example HSO observations, are required in this case. On the contrary, we show that the study of low-luminosity sources (L$<$10 L$_{\odot}$), assuming the same HDO abundance profile, requires too much integration time to be carried out either with available ground-based telescopes or with the HIFI instrument on board HSO. For these sources, only the large interferometer ALMA will allow to constrain the HDO abundance.Comment: 13 pages, 10 figures, accepted by A&

Three-dimensional condylar changes from Herbst appliance and multibracket treatment: A comparison with matched Class II elastics

INTRODUCTION: The purpose of this study was to quantify and qualify the 3-dimensional (3D) condylar changes using mandibular 3D regional superimposition techniques in adolescent patients with Class II Division 1 malocclusions treated with either a 2-phase or single-phase approach. METHODS: Twenty patients with Herbst appliances who met the inclusion criteria and had cone-beam computed tomography (CBCT) images taken before, 8 weeks after Herbst removal, and after the completion of multibracket appliance treatment constituted the Herbst group. They were compared with 11 subjects with Class II malocclusion who were treated with elastics and multibracket appliances and who had CBCT images taken before and after treatment. Three-dimensional models generated from the CBCT images were registered on the mandible using 3D voxel-based superimposition techniques and analyzed using semitransparent overlays and point-to-point measurements. RESULTS: The magnitude of lateral condylar growth during the orthodontic phase (T2-T3) was greater than that during the orthopedic phase (T1-T2) for all condylar fiducials with the exception of the superior condyle (P <0.05). Conversely, posterior condylar growth was greater during the orthopedic phase than the subsequent orthodontic phase for all condylar fiducials (P <0.05). The magnitude of vertical condylar development was similar during both the orthopedic (T1-T2) and orthodontic phases (T2-T3) across all condylar fiducials (P <0.05). Posterior condylar growth during the orthodontic phase (T2-T3) of the 2-phase approach decreased for all condylar fiducials with the exception of the posterior condylar fiducial (P <0.05) when compared with the single-phase approach. CONCLUSIONS: Two-phase treatment using a Herbst appliance accelerates condylar growth when compared with a single-phase regime with Class II elastics. Whereas the posterior condylar growth manifested primarily during the orthopedic phase, the vertical condylar gains occurred in equal magnitude throughout both phases of the 2-phase treatment regime

Proceedings of US - PRC international TOGA symposium

A series of 12 meridional transect along longitude 165°E in the Western Equatorial Pacific ocean were made between mid-1986 and mi-1988 : a time interval spanning an El Nino/Southern Oscillation (ENSO) event. Data collected on these cruises provide a detailed (albeit temporally sparse) view of the oceanic changes which occur in the Western Pacific during an ENSO event. The present work focuses on the evolution of the upper ocean thermohaline and zona velocity fields as revealed by high resolution hydrographic casts and direct near surface velocity measurements. (D'après résumé d'auteur

MUSTANG 3.3 Millimeter Continuum Observations of Class 0 Protostars

We present observations of six Class 0 protostars at 3.3 mm (90 GHz) using the 64-pixel MUSTANG bolometer camera on the 100-m Green Bank Telescope. The 3.3 mm photometry is analyzed along with shorter wavelength observations to derive spectral indices (S_nu ~ nu^alpha) of the measured emission. We utilize previously published dust continuum radiative transfer models to estimate the characteristic dust temperature within the central beam of our observations. We present constraints on the millimeter dust opacity index, beta, between 0.862 mm, 1.25 mm, and 3.3 mm. Beta_mm typically ranges from 1.0 to 2.4 for Class 0 sources. The relative contributions from disk emission and envelope emission are estimated at 3.3 mm. L483 is found to have negligible disk emission at 3.3 mm while L1527 is dominated by disk emission within the central beam. The beta_mm^disk <= 0.8 - 1.4 for L1527 indicates that grain growth is likely occurring in the disk. The photometry presented in this paper may be combined with future interferometric observations of Class 0 envelopes and disks.Comment: 19 pages, 3 figures, AJ accepted, in pres

Astrochemistry of Sub-Millimeter Sources in Orion: Studying the Variations of Molecular Tracers with Changing Physical Conditions

Cornerstone molecules (CO, H_2CO, CH_3OH, HCN, HNC, CN, CS, SO) were observed toward seven sub-millimeter bright sources in the Orion molecular cloud in order to quantify the range of conditions for which individual molecular line tracers provide physical and chemical information. Five of the sources observed were protostellar, ranging in energetics from 1 - 500L_sun, while the other two sources were located at a shock front and within a photodissociation region (PDR). Statistical equilibrium calculations were used to deduce from the measured line strengths the physical conditions within each source and the abundance of each molecule. In all cases except the shock and the PDR, the abundance of CO with respect to H_2 appears significantly below (factor of ten) the general molecular cloud value of 10^-4. {Formaldehyde measurements were used to estimate a mean temperature and density for the gas in each source. Evidence was found for trends between the derived abundance of CO, H_2CO, CH_3OH, and CS and the energetics of the source, with hotter sources having higher abundances.} Determining whether this is due to a linear progression of abundance with temperature or sharp jumps at particular temperatures will require more detailed modeling. The observed methanol transitions require high temperatures (T>50 K), and thus energetic sources, within all but one of the observed protostellar sources. The same conclusion is obtained from observations of the CS 7-6 transition. Analysis of the HCN and HNC 4-3 transitions provides further support for high densities n> 10^7 cm^-3 in all the protostellar sources.Comment: 36 pages, 8 figures, Astronomy and Astrophysics in pres