1,941 research outputs found
A λ = 1.3 Millimeter Aperture Synthesis Molecular Line Survey of Orion Kleinmann-Low
We present a 1".3 spatial resolution interferometric spectral line survey of the core of the Orion molecular cloud, obtained with the OVRO millimeter array. Covering 4 GHz bandwidth in total, the survey contains ~100 emission lines from 18 chemical species. The spatial distributions of a number of molecules point to source I near the IRc2 complex as the dominant energy source in the region but do not rule out the presence of additional lower luminosity objects. At arcsecond resolution, the offsets between dust emission and various molecular tracers suggest that the spectacular "hot core" emission in the Orion core arises via the heating and ablation of material from the surfaces of very high density clumps located ≳500 AU from source I and traced by the dust emission. We find no evidence for a strong internal heating source within the hot core condensation(s)
The estimation of the SZ effects with unbiased multifilters
In this work we study the performance of linear multifilters for the
estimation of the amplitudes of the thermal and kinematic Sunyaev-Zel'dovich
effects. We show that when both effects are present, estimation of these
effects with standard matched multifilters is intrinsically biased. This bias
is due to the fact that both signals have basically the same spatial profile.
We find a new family of multifilters related to the matched multifilters that
cancel this systematic bias, hence we call them Unbiased Matched Multifilters.
We test the unbiased matched multifilters and compare them with the standard
matched multifilters using simulations that reproduce the future Planck
mission's observations. We find that in the case of the standard matched
multifilters the systematic bias in the estimation of the kinematic
Sunyaev-Zel'dovich effect can be very large, even greater than the statistical
error bars. Unbiased matched multifilters cancel effectively this kind of bias.
In concordance with other works in the literature, our results indicate that
the sensitivity and resolution of Planck will not be enough to give reliable
estimations of the kinematic Sunyaev-Zel'dovich of individual clusters.
However, since the estimation with the unbiased matched multifilters is not
intrinsically biased, it can be possible to use them to statistically study
peculiar velocities in large scales using large sets of clusters.Comment: 12 pages, 6 figures, submitted to MNRA
A Sunyaev-Zel'dovich Effect Survey for High Redshift Clusters
Interferometric observations of the Sunyaev-Zel'dovich Effect (SZE) toward
clusters of galaxies provide sensitive cosmological probes. We present results
from 1 cm observations (at BIMA and OVRO) of a large, intermediate redshift
cluster sample. In addition, we describe a proposed, higher sensitivity array
which will enable us to survey large portions of the sky. Simulated
observations indicate that we will be able to survey one square degree of sky
per month to sufficient depth that we will detect all galaxy clusters more
massive than 2x10^{14} h^{-1}_{50}M_\odot, regardless of their redshift. We
describe the cluster yield and resulting cosmological constraints from such a
survey.Comment: 7 pages, 6 figures, latex, contribution to VLT Opening Symposiu
Dense gas and HII regions in the starburst galaxy NGC 253
The energetic activity in the nuclear barred region of NGC 253 is attributable to a burst of star formation. NGC 253 is in many ways a twin of the prototypical starburst galaxy M82; the strong non-thermal radio continuum, high far-infrared luminosity, and bright molecular emission of the central 1 Kpc parallel the morphology of the M82 starburst. Furthermore, the filamentary low ionization optical emission and extended x ray emission along the minor axis in NGC 253 is similar to a scaled down version of the well developed galactic bipolar wind in M82. The infrared luminosity of NGC 253, 3(exp 10) solar luminosity, is comparable to M82 but is emitted from a smaller region (Telesco and Harper 1980). This suggests that the NGC 253 starburst may be more intense and at an earlier evolutionary stage than M82. However, the presence of a non-stellar AGN in NGC 253 may complicate the comparison (Turner and Ho, 1985). Researchers used the Hat Creek millimeter interferometer to map emission from the J = 1 to 0 transitions of HCN and HCO(+) as well as 3 mm continuum emission, toward the nuclear region of NGC 253. The HCO(+) and continuum observations are sensitive to spatial scales from 6 to 45 seconds. The 2 minute field of view comfortably includes the entire starburst region (about 40 seconds; 650 pc). Because the longer baseline HCN observations are not yet complete, they are only sensitive to spatial scales from 15 to 45 seconds
Capital trading, stock trading, and the inflation tax on equity: a note
The authors show that there is more responsiveness of consumption and output to changes in the money supply than exists in the standard neoclassical growth models.Capital investments
Deprojection of Rich Cluster Images
We consider a general method of deprojecting 2D images to reconstruct the 3D
structure of the projected object, assuming axial symmetry. The method consists
of the application of the Fourier Slice Theorem to the general case where the
axis of symmetry is not necessarily perpendicular to the line of sight, and is
based on an extrapolation of the image Fourier transform into the so-called
cone of ignorance. The method is specifically designed for the deprojection of
X-ray, Sunyaev-Zeldovich (SZ) and gravitational lensing maps of rich clusters
of galaxies. For known values of the Hubble constant, H0, and inclination
angle, the quality of the projection depends on how exact is the extrapolation
in the cone of ignorance. In the case where the axis of symmetry is
perpendicular to the line of sight and the image is noise-free, the
deprojection is exact. Given an assumed value of H0, the inclination angle can
be found by matching the deprojected structure out of two different images of a
given cluster, e.g., SZ and X-ray maps. However, this solution is degenerate
with respect to its dependence on the assumed H0, and a third independent image
of the given cluster is needed to determine H0 as well. The application of the
deprojection algorithm to upcoming SZ, X-ray and weak lensing projected mass
images of clusters will serve to determine the structure of rich clusters, the
value of H0, and place constraints on the physics of the intra-cluster gas and
its relation to the total mass distribution.Comment: 7 pages, LaTeX, 2 Postscript figures, uses as2pp4.sty. Accepted for
publication in ApJ Letters. Also available at:
http://astro.berkeley.edu:80/~squires/papers/deproj.ps.g
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