The Case for an Accelerating Universe from
... features. Although formal statistics are not currently available, we are aware that the SCP candidates have yielded a
greater fraction of SNe Ia than the HZT candidates, a signiÐcant number of which turn out to be SNe II. Taken
together, about half of the two teamsÏ candidates are
revealed to be SNe ...
Decoding Galaxy Evolution with Gas
... guidance that made this dissertation possible. His excellent grasp of the larger
picture continually forced me to understand our results in a broader context. His
questions cut straight to the heart of the matter and would evoke sheer terror if
asked by anyone who does not possess David’s constantly ...
- Mineralogical Society of America
... The advent of multi-collector inductively coupled plasma mass spectrometers (MC-ICPMS), as well as improvements to thermal ionization mass spectrometers (TIMS) in the 1990s has
enabled very high precision measurement of isotope ratios for a variety of elements. These mass
spectrometers can efficient ...
REVIEW Early star-forming galaxies and the reionization of the Universe
... galaxies. Second, fQ and fesc must be observationally estimated by
determining the relative effects of stars, dust and nebular emission on
the rest-frame ultraviolet region of high-redshift galaxy spectral energy
distributions or by direct observations in the Lyman continuum at
lower redshift. To re ...
... see also . In this theory, inflation may begin either in the false vacuum, or in an unstable
state at the top of the effective potential. Then the inflaton field φ slowly rolls down to the
minimum of its effective potential. The motion of the field away from the false vacuum is of
crucial import ...
Determination of the Charon/Pluto Mass Ratio from Center-of
... and Charon has made resolved observations of Pluto and
Charon difficult: most groundbased images show only a
blended image. Millis et al. (1989) attempted to make a
determination of the mass ratio using blended images of
Pluto–Charon taken with a 1.55-m groundbased telescope
in support of the 1988 J ...
evidence for radiogenic sulfur-32 in type ab presolar
... et al. 1999). These stars experience a very-late thermal pulse
(VLTP) where convective-reactive nucleosynthesis occurs and
unprocessed, H-rich material is convectively mixed into the Heburning zone (Herwig et al. 2011). For the outer He intershell,
which extends almost up to the stellar surface, Her ...
APS Neutrino Study
... neutrinoless double beta experiments. If neutrino mass is discovered by cosmological observations,
it will confirm our assumption that the relativistic particle background required by BBN and the
CMB is indeed composed of neutrinos.
Leptogenesis models connect neutrinos to the unexplained matter dom ...
The HNC/HCN Ratio in Star-Forming Regions The Harvard
... mechanism was found to be the dissociative recombination of HCNH+ , forming both HNC and HCN in a 1:1
ratio. This branching ratio has been verified experimentally by Mendes et al. (2012). The same model predicted
that the temperature dependence of the HNC/HCN ratio is regulated by the destruction ef ...
Observational motivation for Dark Matter
... Transfer from Thomson cross section to neutral
Hydrogen makes the universe transparent to
photons (but not to electrons!)
Requires a full solution of the ionization and
Lithium abundances in nearby FGK dwarf and subgiant stars
... high resolution spectroscopic study of nearby stars from
about 500 to 800 objects (Ramı́rez, Allende Prieto, &
Lambert, in preparation, hereafter RAL). Their data are
being used to study oxygen abundances in local stellar
populations, but their spectra cover the 6708 Å region,
which contains the li ...
Early Star-Forming Galaxies and the Reionisation of the Universe
... slopes with β < -2.5 have been claimed42,44. As the youngest starburst galaxies in the
local Universe show UV spectra with β > -2.558,59, and extreme slopes (β < -3) may
indicate Population III stars60,61, the steep values derived from the new Hubble data are
The UV slope measurements be ...
Follow-up observations of extremely metal
... to enlarge this sample. We present the first results of an effort to identify new extremely metal-poor stars in the Milky Way halo.
Methods. Our targets have been selected from low-resolution spectra obtained as part of the Sloan Digital Sky Survey, and followedup with medium resolution spectroscopy ...
Circumstellar molecular composition of the oxygen
... 1965 by Neugebauer et al. (1965). It is an extremely red Miratype variable with spectral type ranging from M8.1 to M11.2 and
a period around 470 days (Wing & Lockwood 1973). From dust
shell motions detected at 11 μm with the ISI interferometer, Hale
et al. (1997) deduced a distance of 265 pc. This a ...
Europium, Samarium, and Neodymium Isotopic Fractions in Metal
... 4, respectively. We summarize the available atomic data
for each species in § 3. Our measurements of the elemental abundances and isotopic fractions are presented
in § 5 and § 6. In § 7 we discuss the implications of
our measurements in the context of using isotopic fractions of multiple species to ...
The evolution and explosion of massive stars
... Like all true stars, massive stars are gravitationally confined thermonuclear reactors whose
composition evolves as energy is lost to radiation and neutrinos. Unlike lower-mass stars ( M
ⱗ8M 䉺 ) , however, no point is ever reached at which a massive star can be fully supported by electron
Fundamentals in Nuclear Physics
... accelerators of Berkeley, Caen, Darmstadt and Dubna continue to produce
new nuclei whose characteristics challenge models of nuclear structure. It
has major technological applications, most notably in medicine and in energy production where a knowledge of some nuclear physics is essential for
Number Theory and the Periodicity of Matter
... on the basis of Balmer’s formula, managed to construct the ﬁrst convincing model of the atom and introduced the quantum theory into atomic
physics. The quantum mechanics that developed from Bohr’s model managed
to extend the Balmer formula into a complete description of atomic structure
on the basis ...
the reality of the wolf 630 moving group - TigerPrints
... and chemical evolution of the Galactic disk. To this end, one of the principle approaches
for probing the disk has been to study the so-called galactic (or open) clusters, broadly
defined as gravitionally bound groups of hundreds to thousands of stars in the galactic disk.
Clusters are valuable astr ...
Cosmology Astronomy 1 — Elementary Astronomy LA Mission College Spring F2015
... matter organizing the universe… occurred at about
100s. The actual galaxies appeared much later.
“A fraction of a second and the elements were made”
Inaccurate. H & He (a little Li) very quickly at few
second. Everything else as massive stars fused
elements up to iron in their core and then went
Here - NASA/IPAC Extragalactic Database
... higher Mneb or Q(H0 ).
The number fractions of He and heavy elements (C, N, O. . . )† in real nebulae are about
10% and 0.1% respectively. Helium, although ten times less abundant than hydrogen,
is the dominant source of absorption of photons at energies above 24.4 eV. For order of
magnitudes estima ...
The Animate and the Inanimate
... unavailable or reserve energy of matter; only Lord Kelvin, instead of deriving this from the ordinary
physical laws, immediately concluded that some mysterious vital force must be in operation. Under
my theory, this reversal an be explained on the pure basis of the theory of probability.
The Animate and the Inanimate
... differences will be equalised, and energy of a still higher level or to a greater amount
must become dissipated in order to re-create these difference of concentration. Of the
various varieties of energy, all kinds tend to turn into heat, which is the least concentrated
form of energy; and, even tho ...
... in that work. For line broadening by electron collisions,
the approximations according to Griem (1968) (ions) and
Cowley (1971) (neutrals) were applied. For the Si I and
Si II lines used here, radiation damping is small compared to collisional broadening, and the classical approximation for γrad is ...
Chemical composition of B-type supergiants in the OB8, OB10
... the blue arm of the spectrograph – signal-to-noise ratios in the
reduced spectra were always in excess of 200 for these bright
The CCD frames were reduced to wavelength calibrated
spectra using the IRAF reduction system1 . Standard procedures
were used to bias correct and flat fiel ...
Big Bang nucleosynthesis
In physical cosmology, Big Bang nucleosynthesis (abbreviated BBN, also known as primordial nucleosynthesis) refers to the production of nuclei other than those of the lightest isotope of hydrogen (hydrogen-1, 1H, having a single proton as a nucleus) during the early phases of the universe. Primordial nucleosynthesis is believed by most cosmologists to have taken place from 10 seconds to 20 minutes after the Big Bang, and is calculated to be responsible for the formation of most of the universe's helium as the isotope helium-4 (4He), along with small amounts of the hydrogen isotope deuterium (2H or D), the helium isotope helium-3 (3He), and a very small amount of the lithium isotope lithium-7 (7Li). In addition to these stable nuclei, two unstable or radioactive isotopes were also produced: the heavy hydrogen isotope tritium (3H or T); and the beryllium isotope beryllium-7 (7Be); but these unstable isotopes later decayed into 3He and 7Li, as above.Essentially all of the elements that are heavier than lithium and beryllium were created much later, by stellar nucleosynthesis in evolving and exploding stars.