710 research outputs found
16 x 25 Ge:Ga Detector Arrays for FIFI LS
We are developing two-dimensional 16 x 25 pixel detector arrays of both
unstressed and stressed Ge:Ga photoconductive detectors for far-infrared
astronomy from SOFIA. The arrays, based on earlier 5 x 5 detector arrays used
on the KAO, will be for our new instrument, the Far Infrared Field Imaging Line
Spectrometer (FIFI LS). The unstressed Ge:Ga detector array will cover the
wavelength range from 40 to 120 microns, and the stressed Ge:Ga detector array
from 120 to 210 microns. The detector arrays will be operated with multiplexed
integrating amplifiers with cryogenic readout electronics located close to the
detector arrays. The design of the stressed detector array and results of
current measurements on several prototype 16 pixel linear arrays are reported.
They demonstrate the feasibility of the current concept. ***This paper does not
include Figures due to astro-ph size limitations. Please download entire file
at http://fifi-ls.mpe-garching.mpg.de/spie.det.ps.gz ***Comment: 8 pages, SPIE Proceedings, Astronomical Telescopes and
Instrumentation 200
Testing Magnetic Field Models for the Class 0 Protostar L1527
For the Class 0 protostar, L1527, we compare 131 polarization vectors from
SCUPOL/JCMT, SHARP/CSO and TADPOL/CARMA observations with the corresponding
model polarization vectors of four ideal-MHD, non-turbulent, cloud core
collapse models. These four models differ by their initial magnetic fields
before collapse; two initially have aligned fields (strong and weak) and two
initially have orthogonal fields (strong and weak) with respect to the rotation
axis of the L1527 core. Only the initial weak orthogonal field model produces
the observed circumstellar disk within L1527. This is a characteristic of
nearly all ideal-MHD, non-turbulent, core collapse models. In this paper we
test whether this weak orthogonal model also has the best agreement between its
magnetic field structure and that inferred from the polarimetry observations of
L1527. We found that this is not the case; based on the polarimetry
observations the most favored model of the four is the weak aligned model.
However, this model does not produce a circumstellar disk, so our result
implies that a non-turbulent, ideal-MHD global collapse model probably does not
represent the core collapse that has occurred in L1527. Our study also
illustrates the importance of using polarization vectors covering a large area
of a cloud core to determine the initial magnetic field orientation before
collapse; the inner core magnetic field structure can be highly altered by a
collapse and so measurements from this region alone can give unreliable
estimates of the initial field configuration before collapse.Comment: 43 pages, 9 figures, 4 tables. Accepted by the Astrophysical Journa
1.3 mm Polarized emission in the circumstellar disk of a massive protostar
We present the first resolved observations of the 1.3 mm polarized emission from the disk-like structure surrounding the high-mass protostar Cepheus A HW2. These CARMA data partially resolve the dust polarization, suggesting a uniform morphology of polarization vectors with an average position angle of 57° ± 6° and an average polarization fraction of 2.0% ± 0.4%. The distribution of the polarization vectors can be attributed to (1) the direct emission of magnetically aligned grains of dust by a uniform magnetic field, or (2) the pattern produced by the scattering of an inclined disk. We show that both models can explain the observations, and perhaps a combination of the two mechanisms produces the polarized emission. A third model including a toroidal magnetic field does not match the observations. Assuming scattering is the polarization mechanism, these observations suggest that during the first few 104 years of high-mass star formation, grain sizes can grow from1 mm to several 10s μm.Fil: Fernandez Lopez, Manuel. Provincia de Buenos Aires. Gobernación. Comision de Investigaciones CientÃficas. Instituto Argentino de RadioastronomÃa. Consejo Nacional de Investigaciones CientÃficas y Técnicas. Centro CientÃfico Tecnológico Conicet - La Plata. Instituto Argentino de Radioastronomia; ArgentinaFil: Stephens, I. W.. Harvard-Smithsonian Center for Astrophysics; Estados Unidos. Boston University; Estados Unidos. University of Illinois; Estados UnidosFil: Girart, J. M.. Harvard-Smithsonian Center for Astrophysics; Estados Unidos. Institut de Ciències de l’Espai; EspañaFil: Looney, L.. University of Illinois; Estados UnidosFil: Curiel, S.. Universidad Nacional Autónoma de México; MéxicoFil: Segura Cox, D.. University of Illinois; Estados UnidosFil: Eswaraiah, C.. National Tsing Hua University; República de ChinaFil: Lai, S. P.. National Tsing Hua University; República de Chin
Tumour-associated macrophages and oncolytic virotherapies:a mathematical investigation into a complex dynamics
Anti-cancer therapies based on oncolytic viruses are emerging as important approaches in cancer treatment. However, the effectiveness of these therapies depends significantly on the interactions between the oncolytic viruses and the host immune response. Macrophages are one of the most important cell types in the anti-viral immune responses, by acting as a first line of defence against infections. Here, we consider a mathematical approach to investigate the possible outcomes of the interactions between two extreme phenotypes of macrophages (M1 and M2 cells) and an oncolytic virus (VSV), in the context of B16F10 melanoma. We show that polarization towards either an M1 or M2 phenotype can enhance oncolytic virus therapy through either (i) anti-tumour immune activation, or (ii) enhanced oncolysis. Moreover, we show that tumour reduction and elimination does not depend only on the ratio of M1:M2 cells, but also on the number of tumour-infiltrating macrophages
A Sub-arcsecond Survey Toward Class 0 Protostars in Perseus: Searching for Signatures of Protostellar Disks
We present a CARMA 1.3 mm continuum survey toward 9 Class 0 protostars in the
Perseus molecular cloud at 0.3 (70 AU) resolution. This
study approximately doubles the number of Class 0 protostars observed with
spatial resolutions 100 AU at millimeter wavelengths, enabling the presence
of protostellar disks and proto-binary systems to be probed. We detect
flattened structures with radii 100 AU around 2 sources (L1448 IRS2 and
Per-emb-14) and these sources may be strong disk candidates.
Marginally-resolved structures with position angles within 30 of
perpendicular to the outflow are found toward 3 protostars (L1448 IRS3C, IRAS
03282+3035, and L1448C) and are considered disk candidates. Two others (L1448
IRS3B and IRAS 03292+3039) have resolved structure, possibly indicative of
massive inner envelopes or disks; L1448 IRS3B also has a companion separated by
0.9 (210 AU). IC348-MMS does not have well-resolved
structure and the candidate first hydrostatic core L1451-MMS is marginally
resolved on 1 scales. The strong disk candidate sources were
followed-up with CO () observations, detecting velocity
gradients consistent with rotation, but it is unclear if the rotation is
Keplerian. We compare the observed visibility amplitudes to radiative transfer
models, finding that visibility amplitude ratios suggest a compact component
(possibly a disk) is necessary for 5 of 9 Class 0 sources; envelopes alone may
explain the other 4 systems. We conclude that there is evidence for the
formation of large disks in the Class 0 phase with a range of radii and masses
dependent upon their initial formation conditions.Comment: Accepted to ApJ, 58 pages, 19 Figures, 5 Table
Radioactive Probes of the Supernova-Contaminated Solar Nebula: Evidence that the Sun was Born in a Cluster
We construct a simple model for radioisotopic enrichment of the protosolar
nebula by injection from a nearby supernova, based on the inverse square law
for ejecta dispersion. We find that the presolar radioisotopes abundances
(i.e., in solar masses) demand a nearby supernova: its distance can be no
larger than 66 times the size of the protosolar nebula, at a 90% confidence
level, assuming 1 solar mass of protosolar material. The relevant size of the
nebula depends on its state of evolution at the time of radioactivity
injection. In one scenario, a collection of low-mass stars, including our sun,
formed in a group or cluster with an intermediate- to high-mass star that ended
its life as a supernova while our sun was still a protostar, a starless core,
or perhaps a diffuse cloud. Using recent observations of protostars to estimate
the size of the protosolar nebula constrains the distance of the supernova at
0.02 to 1.6 pc. The supernova distance limit is consistent with the scales of
low-mass stars formation around one or more massive stars, but it is closer
than expected were the sun formed in an isolated, solitary state. Consequently,
if any presolar radioactivities originated via supernova injection, we must
conclude that our sun was a member of such a group or cluster that has since
dispersed, and thus that solar system formation should be understood in this
context. In addition, we show that the timescale from explosion to the creation
of small bodies was on the order of 1.8 Myr (formal 90% confidence range of 0
to 2.2 Myr), and thus the temporal choreography from supernova ejecta to
meteorites is important. Finally, we can not distinguish between progenitor
masses from 15 to 25 solar masses in the nucleosynthesis models; however, the
20 solar mass model is somewhat preferred.Comment: ApJ accepted, 19 pages, 3 figure
- …