1,012 research outputs found
Interpretation of Infrared Vibration-Rotation Spectra of Interstellar and Circumstellar Molecules
Infrared vibration-rotation lines can be valuable probes of interstellar and
circumstellar molecules, especially symmetric molecules, which have no pure
rotational transitions. But most such observations have been interpreted with
an isothermal absorbing slab model, which leaves out important radiative
transfer and molecular excitation effects. A more realistic non-LTE and
non-isothermal radiative transfer model has been constructed. The results of
this model are in much better agreement with the observations, including cases
where lines in one branch of a vibration-rotation band are in absorption and
another in emission. In general, conclusions based on the isothermal absorbing
slab model can be very misleading, but the assumption of LTE may not lead to
such large errors, particularly if the radiation field temperature is close to
the gas temperature.Comment: 10 pages, 5 figures, ApJ in pres
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Direct Imaging At 12 Microns Of The Star-Forming Region W51 IRS-2
Astronom
Ionized Gas in the Galactic Center: New Observations and Interpretation
We present new observations of the [Ne II] emission from the ionized gas in
Sgr A West with improved resolution and sensitivity. About half of the emission
comes from gas with kinematics indicating it is orbiting in a plane tipped
about 25\degree\ from the Galactic plane. This plane is consistent with that
derived previously for the circumnuclear molecular disk and the northern arm
and western arc ionized features. However, unlike most previous studies, we
conclude that the ionized gas is not moving along the ionized features, but on
more nearly circular paths. The observed speeds are close to, but probably
somewhat less than expected for orbital motions in the potential of the central
black hole and stars and have a small inward component. The spatial
distribution of the emission is well fitted by a spiral pattern. We discuss
possible physical explanations for the spatial distribution and kinematics of
the ionized gas, and conclude that both may be best explained by a one-armed
spiral density wave, which also accounts for both the observed low velocities
and the inward velocity component. We suggest that a density wave may result
from the precession of elliptical orbits in the potential of the black hole and
stellar mass distribution.Comment: 28 pages, 13 figures, ApJ in pres
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The Abundances Of Polyacetylenes Toward CRL618
We present a mid-infrared high spectral resolution spectrum of CRL618 in the frequency ranges 778-784 and 1227-1249 cm(-1) (8.01-8.15 and 12.75-12.85 mu m) taken with the Texas Echelon-cross-Echelle Spectrograph (TEXES) and the Infrared Telescope Facility (IRTF). We have identified more than 170 rovibrational lines arising from C2H2, HCN, C4H2, and C6H2. We have found no unmistakable trace of C8H2. The line profiles display a complex structure suggesting the presence of polyacetylenes in several components of the circumstellar envelope (CSE). We derive total column densities of 2.5x10(17), 3.1x10(17), 2.1x10(17), 9.3x10(16) cm(-2), and less than or similar to 5x10(16) cm(-2) for HCN, C2H2, C4H2, C6H2, and C8H2, respectively. The observations indicate that both the rotational and vibrational temperatures in the innermost CSE depend on the molecule, varying from 100 to 350 K for the rotational temperatures and 100 to 500 K for the vibrational temperatures. Our results support a chemistry in the innermost CSE based on radical-neutral reactions triggered by the intense UV radiation field.Spanish Ministerio de Educacion y Ciencia ESP2004-665, AYA2003-2785"Comunidad de Madrid" government S-0505/ESP-0237European Community MCRTN-CT-2004-51230CSICCONACyT SEP-2004-C01-47090UNAMNSF AST-0708074Astronom
Ionized Gas Kinematics At High Resolution. II. Discovery Of A Double Infrared Cluster In II Zw 40
The nearby dwarf galaxy II Zw 40 hosts an intense starburst. At the center of the starburst is a bright compact radio and infrared source, thought to be a giant dense H II region containing approximate to 14,000 O stars. Radio continuum images suggest that the compact source is actually a collection of several smaller emission regions. We accordingly use the kinematics of the ionized gas to probe the structure of the radio-infrared emission region. With TEXES on the NASA-IRTF we measured the 10.5 mu m [S IV] emission line with effective spectral resolutions, including thermal broadening, of similar to 25 and similar to 3 km s(-1) and spatial resolution similar to 1 ''. The line profile shows two distinct, spatially coextensive, emission features. The stronger feature is at galactic velocity and has FWHM 47 km s(-1). The second feature is similar to 44 km s(-1) redward of the first and has FWHM 32 km s(-1). We argue that these are two giant embedded clusters, and estimate their masses to be approximate to 3 x 10(5) M-circle dot and approximate to 1.5 x 10(5) M-circle dot. The velocity shift is unexpectedly large for such a small spatial offset. We suggest that it may arise in a previously undetected kinematic feature remaining from the violent merger that formed the galaxy.University of Hawaii NNX-08AE38ANSF AST-0607312NASAAstronom
Ionized Gas Kinematics at High Resolution IV: Star Formation and a Rotating Core in the Medusa (NGC 4194)
NGC 4194 is a post-merger starburst known as The Medusa for its striking
tidal features. We present here a detailed study of the structure and
kinematics of ionized gas in the central 0.65 kpc of the Medusa. The data
include radio continuum maps with resolution up to 0.18\arcsec (35 pc) and a
m [NeII] data cube with spectral resolution \kms: the first
{\it high resolution, extinction-free} observations of this remarkable object.
The ionized gas has the kinematic signature of a core in solid-body rotation.
The starburst has formed a complex of bright compact \HII~regions, probably
excited by deeply embedded super star clusters, but none of these sources is a
convincing candidate for a galactic nucleus. The nuclei of the merger partners
that created the Medusa have not yet been identified.Comment: to appear in Ap
Preservice teacher beliefs about education from their experiences as K-12 students and members of an adolescent subculture
Title from PDF of title page (University of Missouri--Columbia, viewed on Feb 24, 2010).The entire thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file; a non-technical public abstract appears in the public.pdf file.Dissertation advisor: Dr. Cynthia MacGregor.Vita.Ed. D. University of Missouri--Columbia 2009.Results from the National Assessment of Educational Progress test over the past 35 years have not shown significant, long term improvement of 17 year olds in math or reading. The purpose of the study was to describe beliefs preservice teachers bring to teacher preparation programs that arise from their K-12 experience and as members of an adolescent or youth subculture. Methods of phenomenology were used to address the research questions. From a sample of 162 preservice teachers, 11 themes depicting preservice teacher beliefs about education were identified. The influence of an adolescent or youth subculture in the development of the 11 themes seems obvious in four, related in four, and having no apparent connection to three of the themes. A mechanism of recycling beliefs about education through preservice teachers back to K-12 students is presented that illustrates how emerging adolescent beliefs may enter and how older, outdated beliefs are maintained within education culture. Implications for practice include the development of preservice teacher screening procedures that are able to identify the range of beliefs preservice teachers have about education. Once identified, teacher preparation programs must develop curriculum that will address those preservice teacher beliefs that run counter to program goals through guided reflection and increased exposure to desired behavior.Includes bibliographical reference
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