Diapositiva 1
... A young pulsar evolves relatively fast and slows down The magnetic field of an old pulsar might eventually decay ...
... A young pulsar evolves relatively fast and slows down The magnetic field of an old pulsar might eventually decay ...
Co-production of Nitrogen-15 and Oxygen-18 in
... were cut into 70nm-thick slices with the use of a microtome and analyzed via NanoSIMS for their isotopic composition. As emphasized in Fig. 1.3, Groopman et al. found highly anomalous and spatially correlated hotspots in the δ 18 O/16 O and δ 15 N/14 N values of many of the slices. The ...
... were cut into 70nm-thick slices with the use of a microtome and analyzed via NanoSIMS for their isotopic composition. As emphasized in Fig. 1.3, Groopman et al. found highly anomalous and spatially correlated hotspots in the δ 18 O/16 O and δ 15 N/14 N values of many of the slices. The ...
Multiwavelength optical observations of chromospherically active
... Individual results about stellar parameters and the behaviour of the chromospheric excess emission in each system is reported in Sect. 4. Finally, in Sect. 5 the discussion and conclusions are given. 2. Observations and data reduction The spectroscopic echelle observations of the chromospherically a ...
... Individual results about stellar parameters and the behaviour of the chromospheric excess emission in each system is reported in Sect. 4. Finally, in Sect. 5 the discussion and conclusions are given. 2. Observations and data reduction The spectroscopic echelle observations of the chromospherically a ...
Abstract The Star Formation History of Low Surface Brightness Galaxies
... The star formation histories of low surface brightness galaxies are interesting but poorly constrained. These objects tend to be rather blue, contradicting the initial impression that they may simply be faded remnants of higher surface brightness galaxies whose star formation has finished. Other sce ...
... The star formation histories of low surface brightness galaxies are interesting but poorly constrained. These objects tend to be rather blue, contradicting the initial impression that they may simply be faded remnants of higher surface brightness galaxies whose star formation has finished. Other sce ...
pptx
... ・Many GRB hosts are less massive and low metallicity, But… ・High metallicity environment of dark GRBs ...
... ・Many GRB hosts are less massive and low metallicity, But… ・High metallicity environment of dark GRBs ...
Massive Disruptions in the Cool Core of MACS J1931.8-2634 Steven Ehlert
... disrupted or perhaps even outright destroyed by the physical processes ...
... disrupted or perhaps even outright destroyed by the physical processes ...
The Green Valley is a Red Herring: Galaxy Zoo reveals two
... We use SDSS+GALEX+Galaxy Zoo data to study the quenching of star formation in lowredshift galaxies. We show that the green valley between the blue cloud of star-forming galaxies and the red sequence of quiescent galaxies in the colour-mass diagram is not a single transitional state through which mos ...
... We use SDSS+GALEX+Galaxy Zoo data to study the quenching of star formation in lowredshift galaxies. We show that the green valley between the blue cloud of star-forming galaxies and the red sequence of quiescent galaxies in the colour-mass diagram is not a single transitional state through which mos ...
Discovery of a Dwarf Poststarburst Galaxy near a High Column
... Mg ii / Lyman limit absorbers are due to metal-rich gas in bound halos of brighter galaxies (0.1L*), while damped absorbers are due to metal-rich gas in disks of galaxies of all descriptions and luminosities. Weaker (NH i 1017 cm2) low-ionization (Mg ii and Fe ii) and high-ionization (C iv, Si i ...
... Mg ii / Lyman limit absorbers are due to metal-rich gas in bound halos of brighter galaxies (0.1L*), while damped absorbers are due to metal-rich gas in disks of galaxies of all descriptions and luminosities. Weaker (NH i 1017 cm2) low-ionization (Mg ii and Fe ii) and high-ionization (C iv, Si i ...
Star Formation in the Orion Nebula II: Gas, Dust, Proplyds and
... stars not optically visible because of the high extinction caused by these objects falling within the PDR or the molecular cloud. In Sect. 5 we consider the outflows encountered, which range from microjets with scales of hundreds of astronomical units to large scale outflows with scales of parsecs. ...
... stars not optically visible because of the high extinction caused by these objects falling within the PDR or the molecular cloud. In Sect. 5 we consider the outflows encountered, which range from microjets with scales of hundreds of astronomical units to large scale outflows with scales of parsecs. ...
Magnetic fields and mass loss in massive stars
... On the main sequence, magnetic fields are frequently found in late-type stars, which are thought to have dynamo generated fields, and in the chemically peculiar Ap/Bp stars. The chemical peculiarities in these stars are related to their strong magnetic fields. Only recently magnetic fields have been ...
... On the main sequence, magnetic fields are frequently found in late-type stars, which are thought to have dynamo generated fields, and in the chemically peculiar Ap/Bp stars. The chemical peculiarities in these stars are related to their strong magnetic fields. Only recently magnetic fields have been ...
evidence for radiogenic sulfur-32 in type ab presolar
... SN origin remains unlikely for the three AB grains considered here, because of missing evidence for 44 Ti, relatively low 26 Al/27 Al ratios (a few times 10−3 ), and radiogenic 32 S along with low 12 C/13 C ratios. Instead, we show that born-again asymptotic giant branch (AGB) stars that have underg ...
... SN origin remains unlikely for the three AB grains considered here, because of missing evidence for 44 Ti, relatively low 26 Al/27 Al ratios (a few times 10−3 ), and radiogenic 32 S along with low 12 C/13 C ratios. Instead, we show that born-again asymptotic giant branch (AGB) stars that have underg ...
MASSIVE GALAXIES IN COSMOLOGICAL SIMULATIONS: ULTRAVIOLET-SELECTED
... assume Calzetti extinction with E(B V ) ¼ 0:15. We find that the number density of simulated galaxies brighter than R < 25:5 at z ¼ 2 is about 2 ; 102 h3 Mpc3 for E(B V ) ¼ 0:15 in our most representative run, roughly 1 order of magnitude larger than that of Lyman break galaxies at z ¼ 3. The ...
... assume Calzetti extinction with E(B V ) ¼ 0:15. We find that the number density of simulated galaxies brighter than R < 25:5 at z ¼ 2 is about 2 ; 102 h3 Mpc3 for E(B V ) ¼ 0:15 in our most representative run, roughly 1 order of magnitude larger than that of Lyman break galaxies at z ¼ 3. The ...
Formation Process of the Circumstellar Disk
... We believe that stars are born with a circumstellar disk. The formation of the circumstellar disk is coupled with “the angular momentum problem” that is a serious problem in the star formation process, and the dynamics of disks may determine the mass accretion rate onto the protostar that determines ...
... We believe that stars are born with a circumstellar disk. The formation of the circumstellar disk is coupled with “the angular momentum problem” that is a serious problem in the star formation process, and the dynamics of disks may determine the mass accretion rate onto the protostar that determines ...
Why are most molecular clouds not gravitationally bound
... with star formation efficiencies, , of 1, 5 and 10 per cent (Runs B, C and D, respectively). This means that of the mass that satisfies the above criteria, a fraction of the molecular gas contained therein is assumed to form stars instantaneously and to provide an energy input (approximately 1/3 ...
... with star formation efficiencies, , of 1, 5 and 10 per cent (Runs B, C and D, respectively). This means that of the mass that satisfies the above criteria, a fraction of the molecular gas contained therein is assumed to form stars instantaneously and to provide an energy input (approximately 1/3 ...
The Star Cluster Population of M51: II. Age distribution and relations
... the youngest clusters having extended halos. It remains to be seen how other properties, such as mass, age and spatial distributions depend on the environment in which the clusters form. M51 provides an almost ideal astrophysical laboratory to study extragalactic star clusters. This is due to its re ...
... the youngest clusters having extended halos. It remains to be seen how other properties, such as mass, age and spatial distributions depend on the environment in which the clusters form. M51 provides an almost ideal astrophysical laboratory to study extragalactic star clusters. This is due to its re ...
Th`ese d`astrophysique Chemodynamical Simulations of Evolution
... by stars and I also show accretion, eg. dust production in ISM, is necessary to balance dust destruction by SNII. Our results suggest SNe production accelerates the dust mass evolution by few hundred of Myrs. AGB production with accretion could therefore be enough to explain high dust masses in quas ...
... by stars and I also show accretion, eg. dust production in ISM, is necessary to balance dust destruction by SNII. Our results suggest SNe production accelerates the dust mass evolution by few hundred of Myrs. AGB production with accretion could therefore be enough to explain high dust masses in quas ...
Full Text - Digital Access to Scholarship at Harvard
... has a broad range of energy levels and can interact with light over much of a star’s spectrum, whereas atomic hydrogen gas, for instance, can interact with light primarily only within a few lines for all wavelengths longward of ionizing hydrogen. Because of this, about 30% of the light leaving the G ...
... has a broad range of energy levels and can interact with light over much of a star’s spectrum, whereas atomic hydrogen gas, for instance, can interact with light primarily only within a few lines for all wavelengths longward of ionizing hydrogen. Because of this, about 30% of the light leaving the G ...
Stellar evolution
Stellar evolution is the process by which a star changes during its lifetime. Depending on the mass of the star, this lifetime ranges from a few million years for the most massive to trillions of years for the least massive, which is considerably longer than the age of the universe. The table shows the lifetimes of stars as a function of their masses. All stars are born from collapsing clouds of gas and dust, often called nebulae or molecular clouds. Over the course of millions of years, these protostars settle down into a state of equilibrium, becoming what is known as a main-sequence star.Nuclear fusion powers a star for most of its life. Initially the energy is generated by the fusion of hydrogen atoms at the core of the main-sequence star. Later, as the preponderance of atoms at the core becomes helium, stars like the Sun begin to fuse hydrogen along a spherical shell surrounding the core. This process causes the star to gradually grow in size, passing through the subgiant stage until it reaches the red giant phase. Stars with at least half the mass of the Sun can also begin to generate energy through the fusion of helium at their core, whereas more-massive stars can fuse heavier elements along a series of concentric shells. Once a star like the Sun has exhausted its nuclear fuel, its core collapses into a dense white dwarf and the outer layers are expelled as a planetary nebula. Stars with around ten or more times the mass of the Sun can explode in a supernova as their inert iron cores collapse into an extremely dense neutron star or black hole. Although the universe is not old enough for any of the smallest red dwarfs to have reached the end of their lives, stellar models suggest they will slowly become brighter and hotter before running out of hydrogen fuel and becoming low-mass white dwarfs.Stellar evolution is not studied by observing the life of a single star, as most stellar changes occur too slowly to be detected, even over many centuries. Instead, astrophysicists come to understand how stars evolve by observing numerous stars at various points in their lifetime, and by simulating stellar structure using computer models.In June 2015, astronomers reported evidence for Population III stars in the Cosmos Redshift 7 galaxy at z = 6.60. Such stars are likely to have existed in the very early universe (i.e., at high redshift), and may have started the production of chemical elements heavier than hydrogen that are needed for the later formation of planets and life as we know it.