14473137
TEXES Observations of Pure Rotational H2 Emission from AB Aurigae
We present observations of pure rotational molecular hydrogen emission from the Herbig Ae star, AB Aur. Our observations were made using the Texas Echelon Cross Echelle Spectrograph (TEXES) at the NASA Infrared Telescope Facility and the Gemini North Observatory. We searched for H_2 emission in the S(1), S(2), and S(4) lines at high spectral resolution and detected all three. By fitting a simple model for the emission in the three transitions, we derive T = 670 ± 40 K and M = 0.52 ± 0.15 M_⊙ for the emitting gas. On the basis of the 8.5 km s^(-1) FWHM of the S(2) line, assuming the emission comes from the circumstellar disk, and with an inclination estimate of the AB Aur system taken from the literature, we place the location for the emission near 18 AU. Comparison of our derived temperature to a disk structure model suggests that UV and X-ray heating are important in heating the disk atmosphere.
16861138
High Sensitivity, High Spectral Resolution, Mid-infrared Spectroscopy
We broadly discuss mid-infrared spectroscopy and detail our new high spectral resolution instrument, the Texas Echelon-cross-Echelle Spectrograph (TEXES).
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.
16613665
NEAR-INFRARED MOLECULAR HYDROGEN EMISSION FROM THE CENTRAL REGIONS OF GALAXIES: REGULATED PHYSICAL CONDITIONS IN THE INTERSTELLAR MEDIUM
The central regions of many interacting and early-type spiral galaxies are actively forming stars. This process affects the physical and chemical properties of the local interstellar medium, as well as the evolution of the galaxies. We observed near-infrared H2 emission lines: v ¼ 1 0 S(1), 3–2 S(3), 1–0 S(0), and 2–1 S(1) from the central � 1 kpc regions of the archetypical starburst galaxies M82 and NGC 253 and the less dramatic but still vigorously star-forming galaxies NGC 6946 and IC 342. Like the far-infrared continuum luminosity, the nearinfrared H2 emission luminosity can directly trace the amount of star formation activity because the H2 emission lines arise from the interaction between hot and young stars and nearby neutral clouds. The observed H2 line ratios show that both thermal excitation and nonthermal excitation are responsible for the emission lines but that the great majority of the near-infrared H2 line emission in these galaxies arises from energy states excited by ultraviolet fluorescence. The derived physical conditions, e.g., far-ultraviolet radiation field and gas density, from [C ii ]a nd [O i] lines and far-infrared continuum observations when used as inputs to photodissociation models also explain the luminosity of the observed H2 1–0S(1) line. The ratio of the H2 1–0S(1) line to far-IR continuum luminosity is remarkably constant over a broad range of galaxy luminosities: LH2 =LFIR ’ 10 � 5 , in normal late-type galaxies (including the Galactic center), in nearby starburst galaxies, and in luminous IR galaxies (LIRGs: LFIR >10 11 L� ). Examining this constant ratio in the context of photodissociation region models, we conclude that it implies that the strength of the incident UV field on typical molecular clouds follows the gas density at the cloud surface. Subject headings: galaxies: individual(M82,NGC 253,NGC6946,IC 342) — galaxies: ISM — galaxies:spiral — galaxies: starburst — infrared: ISM — ISM: lines and bands
122125252
The TEXES Survey For H-2 Emission From Protoplanetary Disks
209907524
Photon - dominated regions in low UV fields : a study of the peripheral regions of L1204 /S140
119540499
Low cost lead glass cherenkov detectors
Abstract We have compared the optical properties of lead glass bars of three different surface qualities. One was ground and polished in the conventional manner; the other two were in the unimproved state resulting from the extrusion or casting process. We find that the three bars exhibit similar optical characteristics. Use of such unpolished lead glass Cherenkov bars in electromagnetic shower detectors should result in considerable cost savings.
118745241
Status of Neutrino Physics Experiments
Relevant results from neutrino physics experiments since FPCP2009 with an emphasis on oscillations and the ability to measure or limit the mixing angle {theta}{sub 13}.
123152124
Preliminary measurements of shadowing at very low XBj
The ratio of cross sections for inelastic muon scattering on xenon and deuterium nuclei was measured at very low XBj (0.00002<XBj<0.25) for 0.01<Q2<60 (GeV/c)2. The data were taken at Fermilab experiment E665 with an average muon beam energy of 490 GeV incident on 1.1 meter long deuterium and xenon targets. Two largely independent analysis techniques gave statistically consistent results and show a smooth decrease in the ratio of the xenon‐to‐deuterium per–nucleon cross sections from ∼1 to ∼0.7 as XBj decreases from ∼0.1 to ∼0.003. In the XBj range 0.00002 to 0.003, the ratio remains roughly constant at ∼0.7.
122340200
Identification of large-transverse-momentum hadrons using a ring-imaging Cherenkov counter
Abstract We have constructed and operated a large-aperture ring-imaging Cherenkov counter in a large-transverse-momentum experiment at Fermilab. Approximately 3 photons per relativistic particle are emitted in helium gas, focused by spherical mirrors and detected by multistep proportional chambers using a He/TEA gas mixture. Hadron identification is obtained from threshold to approximately 200 GeV c .
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.