3,199 research outputs found
H. B. Reitlinger and the origins of the Efficiency at Maximum Power formula for Heat Engines
Even if not so ancient, the history of the heat engine efficiency at maximum
power expression have been yet turbulent. More than a decade after the
publication of the seminal article by Curzon and Ahlborn in 1975, one's
rediscovered two older works by Chambadal and Novikov, both dating from 1957.
Then, some years ago, the name of Yvon arose from a textual reference to this
famous relation in a conference article published in 1955. Thanks to an
historical study of French written books not anymore published for a long time,
and since never translated in other languages, we bring to light in this paper
that this relation was actually firstly proposed by Henri B. Reitlinger in
1929.Comment: 6 pages, 3 figure
Mission: Impossible (Escape from the Lyman Limit)
We investigate the intrinsic opacity of high-redshift galaxies to outgoing
ionising photons using high-quality photometry of a sample of 27
spectroscopically-identified galaxies of redshift 1.9<z<3.5 in the Hubble Deep
Field. Our measurement is based on maximum-likelihood fitting of model galaxy
spectral energy distributions-including the effects of intrinsic Lyman-limit
absorption and random realizations of intervening Lyman-series and Lyman-limit
absorption-to photometry of galaxies from space- and ground-based broad-band
images. Our method provides several important advantages over the methods used
by previous groups, including most importantly that two-dimensional sky
subtraction of faint-galaxy images is more robust than one-dimensional sky
subtraction of faint-galaxy spectra. We find at the 3sigma statistical
confidence level that on average no more than 4% of the ionising photons escape
galaxies of redshift 1.9<z<3.5. This result is consistent with observations of
low- and moderate-redshift galaxies but is in direct contradiction to a recent
result based on medium-resolution spectroscopy of high-redshift (z~3) galaxies.
Dividing our sample in subsamples according to luminosity, intrinsic
ultraviolet colour, and redshift, we find no evidence for selection effects
that could explain such discrepancy. Even when all systematic effects are
included, the data could not realistically accomodate any escape fraction value
larger than ~15%.Comment: Accepted for publication in Monthly Notices of the Royal Astronomical
Society. 8 pages, 4 b/w figures, MNRAS styl
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