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Variations in the Star Formation Efficiency of the Dense Molecular
Variations in the Star Formation Efficiency of the Dense Molecular

... to systematically study the effect of gas density on star formation over large parts of the universe. In this paper, we present new observations of the HCN (1–0) transition that cover large (∼ kpc) parts of nearby galaxy disks and compare them to estimates of the recent star formation rate and CO em ...
20. Meteorites and the chemical evolution of the Milky Way
20. Meteorites and the chemical evolution of the Milky Way

... (Scalo, 1986). In most models it is assumed that the IMF is constant in space and time; this is consistent with observational evidence (Kroupa, 2002). 5. Except for the simplest models (see next section), infall of gas from the halo onto the disk and outflows from galactic winds are often included i ...
Formation of Molecular Clouds and Global Conditions for Star
Formation of Molecular Clouds and Global Conditions for Star

... on scales from entire galaxies (Kennicutt 1989, 1998; Gao and Solomon 2004; Saintonge et al. 2011a) to kpc and subkpc regions (Wong and Blitz 2002; Bigiel et al. 2008; Rahman et al. 2012; Leroy et al. 2013) to individual GMCs (Evans et al. 2009; Heiderman et al. 2010; Lada et al. 2010, 2012). These ...
The formation and destruction of molecular clouds and galactic star
The formation and destruction of molecular clouds and galactic star

... We first model the growth of molecular clouds. Inoue & Inutsuka (2012) showed that we need multiple episodes of compression of HI clouds to create molecular clouds. According to the standard picture of supernova-regulated ISM dynamics (e.g., McKee & Ostriker 1977), the typical timescale between cons ...
X-Ray Properties of Young Stars and Stellar Clusters
X-Ray Properties of Young Stars and Stellar Clusters

... X-ray emission from high-velocity protostellar Herbig-Haro outflows. The reader interested in earlier X-ray studies is referred to reviews by Feigelson and Montmerle (1999), Glassgold et al. (2000), Favata and Micela (2003), Paerels and Kahn (2003), and Güdel (2004). The COUP is particularly valuabl ...
83-98
83-98

... The most commonly used relationships for determination of distances to Cepheids are the period-luminosity-colour (P-L-C) relationships of Sandage & Tammann (1969) and Tammann (1970). With this method, the accuracy of the derived distance depends upon the accuracy with which the colour excess is dete ...
Stars: Stellar Evol & “death” Galaxies Astronomy 1 — Elementary Astronomy
Stars: Stellar Evol & “death” Galaxies Astronomy 1 — Elementary Astronomy

... than a neutron star, there is nothing that can stop the inward collapse due to gravity ...
The Milky Way`s external disc constrained by 2MASS star counts
The Milky Way`s external disc constrained by 2MASS star counts

... warp, we then tentatively adjust the star counts on both sides of the galaxy, to check the values of the northern and the southern warps independently. As such, it is not possible for us to create a stellar overdensity in the model by a misalignment of the stellar and dusty warps. Figure 3 (top pane ...
The Life and Work of Edward Emerson Barnard
The Life and Work of Edward Emerson Barnard

... his sick bed long enough to note that the ring was still visible in the 40-inch telescope, though 'very thin' and with a satellite at each end. 'Without occultation it was almost impossible to see any trace of the ring on the sky,' he noted 'The condensations were feebly seen as slightly brighter pa ...
Clusters: age scales for stellar physics
Clusters: age scales for stellar physics

... we cannot make experiments except in very few situations and we rely on observations and theory. Thus, observational phenomena with very well defined ages, our anchors, are extremely important. As a matter of fact, there is a scarcity of them and, moreover, several results do not agree with each oth ...
The Ages of Stars
The Ages of Stars

... phases. But often we need to tie together observations of independent objects to arrive at an understanding of a process. Some examples include: • The formation and evolution of proto-planetary disks appear to occur in the first ∼ 100 Myr of a star’s life, with debris disks forming later. At present ...
Stars, Galaxies, and Beyond
Stars, Galaxies, and Beyond

... The Nature of Galaxies (Chapter 25) ..............................................................................................................................189 Spiral and Irregular Galaxies ........................................................................................................ ...
Magnetic cycles of Sun-like stars with different levels of coronal and
Magnetic cycles of Sun-like stars with different levels of coronal and

... It can be noted that among the databases of observations of Sun-like stars with known values of SHK the sample of stars of the HK-project was selected most carefully in order to study stars which are analogues of the Sun. Moreover, unlike different Planet Search Programs of observations of Sun-like ...
Barium and europium abundances in cool dwarf stars and
Barium and europium abundances in cool dwarf stars and

... Ba abundance consist of 88% and 12%, respectively, according to Cameron (1982), 87% and 13% according to Käppeler et al. (1989), and 81% and 19% according to the most recent data of Arlandini et al. (1999). The solar europium mostly originated from the r-process: 91% according to Cameron (1982) and ...
ASTRONOMY AND ASTROPHYSICS Barium and europium
ASTRONOMY AND ASTROPHYSICS Barium and europium

... halo stars are of the r-process origin. Much observational efforts were invested in testing this idea. For extremely metalpoor stars with metallicities [Fe/H] ≤ −2.4 McWilliam (1998) has derived an average [Eu/Ba] = 0.69, consistent with pure rprocess nucleosynthesis provided that the data of Arland ...
The physics and modes of star cluster formation: observations
The physics and modes of star cluster formation: observations

... hindered by the fact that open clusters are born in molecular clouds and, during their formation and early evolution, are completely embedded in molecular gas and dust. They are thus obscured from view at optical wavelengths, where the traditional astronomical techniques are most effective. Fortunat ...
The Life Cycle of Stars: Supernovae in Starbursts by Jason Kezwer
The Life Cycle of Stars: Supernovae in Starbursts by Jason Kezwer

... to search for obscured supernovae in this extreme star forming environment. This monitoring program was aimed as a feasibility study to determine the practicality of a large scale near-IR LIRG/ULIRG imaging survey. Establishing the supernova rate in these dusty galaxies is an important step toward c ...
2 Statistical properties of a sample of periodically variable B-type supergiants
2 Statistical properties of a sample of periodically variable B-type supergiants

Introduction_to_pulsar_astronomy
Introduction_to_pulsar_astronomy

... radius of these objects. They predicted radii of the order of 10 km! Such small objects should be undetectable by any telescope at the vast distances to the nearest supernova remnants (normally many thousands of light-years). ...
the stebbins galaxy: the origins of interstellar medium studies
the stebbins galaxy: the origins of interstellar medium studies

... Shapley was well aware that his cosmic conclusions were only valid if his distances to globular clusters were trustworthy, and his methods assumed that any interstellar absorption of starlight was negligible. For that reason he included a chapter on ―The Transparency of Space‖ in Star Clusters summa ...
12-1 - Piscataway High School
12-1 - Piscataway High School

... distant background when you look with first one eye and then with the other (see page 44). In this case, the baseline is the distance between your eyes, and the parallax is the angle through which your thumb appears to move when you change eyes. The farther away you hold your thumb, the smaller the p ...
Evolution of low mass stars
Evolution of low mass stars

... The HRD inspired an English astronomer, Sir Arthur Stanley Eddington (18821944), when Russell visited London and presented his diagram at a meeting of the Royal Astronomical Society in 1913 (Eisberg, 2002). At the time, Eddington was the chief assistant of the Royal Greenwich Observatory. In 1926 Ed ...
Strongly suggested reading: The stellar halo of the Galaxy
Strongly suggested reading: The stellar halo of the Galaxy

... time. There is a cosmological framework in place, the Λ cold dark matter (CDM) paradigm, which broadly describes from first principles how structures in the Universe have evolved (e.g. Springel et al. 2006 and references therein). In this model, galaxies form hierarchically, through the amalgamation ...
Master thesis
Master thesis

... the evolution of a planetary nebula (PN) envelope. The underlying framework is CRONOS, a fully parallel hydrodynamics framework (C++, OpenMPI) allowing the user to choose different Riemann solvers and limiters. The setup is based on a roadmap with clear defined milestones. Each milestone consists of ...
Type Ia supernovae as stellar endpoints and cosmological tools
Type Ia supernovae as stellar endpoints and cosmological tools

... because dark energy is so dilute (1 m3 contains the energy equivalent to a few atoms of hydrogen), its effects can only be seen on vast scales. We must compare supernovae across ~10 Gyr of cosmic time, during which stars and galaxies have undergone substantial evolution. Therefore, it is critical to ...
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Future of an expanding universe

Observations suggest that the expansion of the universe will continue forever. If so, the universe will cool as it expands, eventually becoming too cold to sustain life. For this reason, this future scenario is popularly called the Big Freeze.If dark energy—represented by the cosmological constant, a constant energy density filling space homogeneously, or scalar fields, such as quintessence or moduli, dynamic quantities whose energy density can vary in time and space—accelerates the expansion of the universe, then the space between clusters of galaxies will grow at an increasing rate. Redshift will stretch ancient, incoming photons (even gamma rays) to undetectably long wavelengths and low energies. Stars are expected to form normally for 1012 to 1014 (1–100 trillion) years, but eventually the supply of gas needed for star formation will be exhausted. And as existing stars run out of fuel and cease to shine, the universe will slowly and inexorably grow darker, one star at a time. According to theories that predict proton decay, the stellar remnants left behind will disappear, leaving behind only black holes, which themselves eventually disappear as they emit Hawking radiation. Ultimately, if the universe reaches a state in which the temperature approaches a uniform value, no further work will be possible, resulting in a final heat death of the universe.
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