14433479
Search for CP violation at CLEO
Abstract Recent results from CLEO on the search for CP violation in beauty and charm meson decays are reviewed.
42580412
Identification of High Transverse-Momentum Hadrons with a Ring-Imaging Cerenkov Counter
We have constructed and operated a large aperture ring-imaging Cerenkov counter in a high transverse-momentum experiment at Fermilab. We used multistep proportional chambers with a He/TEA photosensitive gas mixture to observe approximately 3.5 photons per relativistic particle. Hadron identification is obtained with good efficiency from threshold to 250 GeV/c.
14365004
High-resolution observations of the near-infrared emission from NGC 6822 Hubble
We have observed Hubble V, the brightest H II region complex in the dwarf irregular galaxy NGC 6822, at near-infrared (near-IR; 1.8–2.4 μm) wavelengths. The line emission maps of Hubble V show the typical structure of a photodissociation region (PDR) where an ionized core, traced by compact He I emission (2.0587 μm) and Brγ emission (2.1661 μm), is surrounded by an outer layer traced by molecular hydrogen (H2) emission. The measured line ratios of H2 2– 1 S(1) (2.2477 μm)/1–0 S(1) (2.1218 μm) from 0.2 to 0.6 and the unshifted and unresolved line profiles suggest that the H2 emission originates purely from a PDR. We find no evidence for shock activity. By comparing the H2 results with a PDR model, we conclude that Hubble V includes dense (104.5 cm−3) and warm PDRs. In this environment, most of the H2 molecules are excited by far-ultraviolet photons (with a field strength of 102–4 times that of the average interstellar field), although collisional processes de-excite H2 and contribute significantly to the excitation of the first vibrational level. We expect that Hubble V is in the early stage of molecular cloud dissolution.
117152703
Young, Jupiter-Mass Objects in Ophiuchus
We have used 3.5 to 8 micron data from the Cores to Disks (c2d) Legacy survey and our own deep IJHKs images of a 0.5 square degree portion of the c2d fields in Ophiuchus to produce a sample of candidate young objects with probable masses between 1 and 10 Jupiter masses. The availability of photometry over whole range where these objects emit allows us to discriminate between young, extremely low-mass candidates and more massive foreground and background objects and means our survey will have fewer false positives than existing near-IR surveys. The sensitive inventory of a star forming cloud from the red to the mid-IR will allow us to constrain the IMF for these non-clustered star formation regions to well below the deuterium burning limit. For stars with fluxes in the broad gap between the 2MASS limits and our limits, our data will provide information about the photospheres. We will use the Spitzer results in combination with current disk models to learn about the presence and nature of circumstellar disks around young brown dwarfs.
55470700
MEDIUM RESOLUTION SPECTRAL LIBRARY OF LATE-TYPE STELLAR TEMPLATES IN NEAR-INFRARED BAND
We present medium resolution (R = 5000 6000) spectra in the near-infrared band, 1.4 1.8 µm, for template stars in G, K, and M types observed by the echelle spectrometer, IRCS, at the SUBARU 8.2 m telescope. The identification of lines is based on the spectra of Arcturus (K2 III) in the literature. We measured the equivalent of widths and compared our results to those of Meyer et al. (1998). We conclude that our spectral resolution (R = 6000) data can investigate more accurately the properties of lines in stellar spectra. The library of the template stellar spectra in ASCII format are available for download on the World Wide Web.
15532404
Molecular cloud structure in the magellanic clouds: Effect of metallicity
The chemical structure of neutral clouds in low-metallicity environments is examined, with particular emphasis on the H to H2 and C+ to CO transitions. We observed near-IR H2 (1, 0) S(1), (2, 1) S(1), and (5, 3) O(3) lines and the 12CO J = 1 → 0 line from 30 Doradus and N159/N160 in the Large Magellanic Cloud and from DEM S 16, DEM S 37, and LI-SMC 36 in the Small Magellanic Cloud. We find that the H2 emission is UV-excited and that (weak) CO emission always exists (in our surveyed regions) toward positions where H2 and [C II] emission have been detected. Using a PDR code and a radiative transfer code, we simulate the emission of line radiation from spherical clouds and from large planar clouds. Because [C II] emission and H2 emission arise on the surface of the cloud and because the lines are optically thin, these lines are not affected by changes in the relative sizes of the neutral cloud and the CO-bearing core, while the optically thick CO emission can be strongly affected. The sizes of clouds are estimated by measuring the deviation of CO emission strength from that predicted by a planar cloud model of a given size. The average cloud column density, and therefore its size, increases as the metallicity decreases. Our result agrees with the photoionization-regulated star formation theory of McKee.
119474065
R=100,000 Mid-IR Spectroscopy of UCHII Regions: High Resolution is Worth it!
Ultracompact HII regions are signposts of massive star formation and their properties provide diagnostics for the characteristics of very young O stars embedded in molecular clouds. While radio observations have given us a good picture of the morphology of these regions, they have not provided clear information about the kinematics. Using high spectral resolution observations of the 12.8 micron [NeII] line, it has been possible for the first time to trace the internal kinematics of several ultracompact HII regions. We find that the motions in the cometary ultracompact HII regions MonR2 and G29.96-0.02 are highly organized. The velocity patterns are consistent with parabolic ionized flows along a neutral boundary layer.