3,647 research outputs found
Thermal resistances of solder-boss/potting compound combinations
Formulas, which can be used as a design tool, are derived to calculate the thermal resistance of solder-boss/potting compound combinations, for different depths of a solder boss, in electronic cordwood modules. Since the solder boss is the heat source, its shape and position will affect the thermal resistance of the surrounding potting compound
MMTF Discovery of Giant Ionization Cones in MR 2251-178: Implications for Quasar Radiative Feedback
We report the discovery of giant ionization cones in the 140-kpc nebula
around quasar MR 2251-178 based on deep [O III] 5007/H-beta and [N II]
6583/H-alpha flux ratio maps obtained with the Maryland-Magellan Tunable Filter
(MMTF) on the Baade-Magellan 6.5m telescope. These cones are aligned with the
weak double-lobed radio source observed on smaller scale <30 kpc). They have an
opening angle ~120deg +/- 10deg and subtend ~65-90% of 4pi steradians, where
the large uncertainty takes into account possible projection effects. The
material in the outer ionization cones is matter-bounded, indicating that all
ionizing photons emitted through the cones escape from the system. The quasar
ionizing flux is ~2-3 times fainter outside of these cones, despite the largely
symmetric geometry of the nebula in [O III]. Overall, adding up the
contributions from both inside and outside the cones, we find that ~65-95% of
the quasar ionizing radiation makes its way out of the system. These results
emphasize the need for line ratio maps to quantify the escape fraction of
ionizing radiation from quasars and the importance of quasar radiative feedback
on the intergalactic medium.Comment: 9 pages, 4 figures, 1 table. Accepted for publication in ApJ Letter
X-QUEST: A Comprehensive X-ray Study of Local ULIRGs and QSOs
We present results from the X-ray portion of a multi-wavelength study of
local ULIRGs and QSOs called QUEST (Quasar-ULIRG Evolution STudy). The data
consist of new and archival X-ray data on 40 ULIRGs and 26 PG QSOs taken with
Chandra and XMM-Newton. A combination of traditional and hardness ratio
spectral fitting methods is used to characterize the X-ray properties of these
objects. The absorption-corrected 2-10 keV to bolometric luminosity ratios of
the ULIRGs and PG QSOs suggest that the likelihood for dominant nuclear
activity increases along the merger sequence from "cool" ULIRGs, "warm" ULIRGs,
infrared-bright QSOs, and infrared-faint QSOs. The starburst dominates the
total power in ULIRGs prior to the merger, and this is followed by rapid black
hole growth during and after coalescence. These results are in general
agreement with those obtained in the mid-infrared with Spitzer and recent
numerical simulations.Comment: 63 pages preprint style including 16 figures and 11 tables; accepted
by Ap
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