the origin of the hubble sequence - Yale Astronomy
... galaxies are largely determined by a single parameter, which may be the total mass (Tully, Mould, and Aaronson 1982), the virial velocity (Lake and Carlberg 1988b), or just the bulge mass (Meisels and Ostriker 1984). The classification sequence proposed by Hubble (1936) for spiral galaxies is based o ...
... galaxies are largely determined by a single parameter, which may be the total mass (Tully, Mould, and Aaronson 1982), the virial velocity (Lake and Carlberg 1988b), or just the bulge mass (Meisels and Ostriker 1984). The classification sequence proposed by Hubble (1936) for spiral galaxies is based o ...
Asteroseismic Modelling of Solar-like Stars
... through nuclear fusion and emit it in the form of light. Furthermore, most of the elements that the Earth and all the living things are made up of have been produced in the stars. Scientists are in particular interested in understanding what is beyond apparent. However, all the information we have a ...
... through nuclear fusion and emit it in the form of light. Furthermore, most of the elements that the Earth and all the living things are made up of have been produced in the stars. Scientists are in particular interested in understanding what is beyond apparent. However, all the information we have a ...
Radial velocity planet detection biases at the stellar rotational period
... processes given certain conditions (e.g. Hatzes et al. 2011; Howard et al. 2013; Pepe et al. 2013). In some cases, it is difficult to distinguish a planetary RV signal from activity, for example when stellar rotation periods are close to the orbital period of a planet candidate (e.g. Dragomir et al. ...
... processes given certain conditions (e.g. Hatzes et al. 2011; Howard et al. 2013; Pepe et al. 2013). In some cases, it is difficult to distinguish a planetary RV signal from activity, for example when stellar rotation periods are close to the orbital period of a planet candidate (e.g. Dragomir et al. ...
Galaxies at High Redshift Encyclopedia of Astronomy & Astrophysics eaa.iop.org Mauro Giavalisco
... the hydrogen ionization edge or Lyman limit. Star-forming galaxies are very luminous at UV wavelengths and have a characteristic ‘blue’ spectrum, i.e. rich in radiation of short wavelengths, which is ‘flat’, namely the intensity of the light does not depend on the wavelength. In a diagram that plots ...
... the hydrogen ionization edge or Lyman limit. Star-forming galaxies are very luminous at UV wavelengths and have a characteristic ‘blue’ spectrum, i.e. rich in radiation of short wavelengths, which is ‘flat’, namely the intensity of the light does not depend on the wavelength. In a diagram that plots ...
The UV properties of E+ A galaxies: constraints on feedback
... systems follows that of the general galaxy population as a whole (Blake et al. 2004). The fraction of E+A systems in clusters shows a rapid decline from intermediate redshifts (z ∼ 0.5) where it is typically higher than 20 percent (e.g. Couch & Sharples 1987; Belloni et al. 1995) to less than 1 perc ...
... systems follows that of the general galaxy population as a whole (Blake et al. 2004). The fraction of E+A systems in clusters shows a rapid decline from intermediate redshifts (z ∼ 0.5) where it is typically higher than 20 percent (e.g. Couch & Sharples 1987; Belloni et al. 1995) to less than 1 perc ...
Variable Star Section Circular - Number 75
... This Circular, number 75, has been issued out of sequence - numbers 73 and 74 will follow soon after, at the end of February. This might create problems if your subscription has nearly run out. The number of Circulars that you still have to come is indicated by the part of the serial number followin ...
... This Circular, number 75, has been issued out of sequence - numbers 73 and 74 will follow soon after, at the end of February. This might create problems if your subscription has nearly run out. The number of Circulars that you still have to come is indicated by the part of the serial number followin ...
Transparencies - Rencontres de Moriond
... Confusion w HeI/HI emission line stars (≈ LBV or WR star) ? • No such star closer than 1.2" • Soft spectrum of W-R stars : cannot penetrate through the deep obscuration Colliding winds of binary system including a W-R star ? • Harder spectrum • Variability on days to years rather than hours Low mass ...
... Confusion w HeI/HI emission line stars (≈ LBV or WR star) ? • No such star closer than 1.2" • Soft spectrum of W-R stars : cannot penetrate through the deep obscuration Colliding winds of binary system including a W-R star ? • Harder spectrum • Variability on days to years rather than hours Low mass ...
Stellar Wind Mechanisms and Instabilities
... the realization that nearly all stars lose mass through a more or less continuous surface outflow called a “stellar wind”. While it was long apparent that stars could eject material in dramatic outburts like novae or supernovae, the concept of continuous mass loss in the relatively quiescent phases ...
... the realization that nearly all stars lose mass through a more or less continuous surface outflow called a “stellar wind”. While it was long apparent that stars could eject material in dramatic outburts like novae or supernovae, the concept of continuous mass loss in the relatively quiescent phases ...
VLT observations of GRS 1915+ 105
... several observers at different wavelengths. In spite of this work, the nature of the X-ray binary system in GRS 1915+105 is still a matter of debate. The strong interstellar absorption towards the source, that implies optical extinctions of AV ∼ 27 magnitudes (Chaty et al. 1996), appears as the main ...
... several observers at different wavelengths. In spite of this work, the nature of the X-ray binary system in GRS 1915+105 is still a matter of debate. The strong interstellar absorption towards the source, that implies optical extinctions of AV ∼ 27 magnitudes (Chaty et al. 1996), appears as the main ...
ULTRA-COMPACT HII REGIONS AND MASSIVE STAR FORMATION
... of forming. They are dense, gravitationally bound, molecular cloudlets that are undergoing quasistatic gravitational contraction. Formation of PSCs may be the most poorly understood stage of massive star formation (Garay & Lizano 1999). PSCs have not yet formed a central protostar and therefore will ...
... of forming. They are dense, gravitationally bound, molecular cloudlets that are undergoing quasistatic gravitational contraction. Formation of PSCs may be the most poorly understood stage of massive star formation (Garay & Lizano 1999). PSCs have not yet formed a central protostar and therefore will ...
IAC_L3_thickdisk
... the disk, e.g. via Jeans equation. Is there more matter in the disk that we can account for from census of visible objects ? The tracer sample must be in equilibrium so the stars need to be older than a few Gyr. The last few estimates have used K dwarfs and K giants - probably OK but they do include ...
... the disk, e.g. via Jeans equation. Is there more matter in the disk that we can account for from census of visible objects ? The tracer sample must be in equilibrium so the stars need to be older than a few Gyr. The last few estimates have used K dwarfs and K giants - probably OK but they do include ...
Circumstellar Material in Young Stellar Objects
... which collapse under the influence of their own gravity. However, after more than two centuries of research many important questions regarding the star formation process, and the fundamentals of planet formation, still remain unanswered. Nonetheless, the rapid progress in our knowledge of star forma ...
... which collapse under the influence of their own gravity. However, after more than two centuries of research many important questions regarding the star formation process, and the fundamentals of planet formation, still remain unanswered. Nonetheless, the rapid progress in our knowledge of star forma ...
Read Claudia`s PhD thesis
... and for the extragalactic RR Lyrae used to actually infer the distance. Our first target has been the Fornax dSph galaxy, one of the very few dwarf spheroidals, along with the Sagittarius and the Canis Maior dSph’s, found to possess globular clusters. In order to make a comprehensive and deep (V ≤ 2 ...
... and for the extragalactic RR Lyrae used to actually infer the distance. Our first target has been the Fornax dSph galaxy, one of the very few dwarf spheroidals, along with the Sagittarius and the Canis Maior dSph’s, found to possess globular clusters. In order to make a comprehensive and deep (V ≤ 2 ...
A new asteroseismic diagnostic for internal rotation in $\ gamma
... ten computed assuming simplifying hypotheses. This is the case with the traditional approximation of rotation (TAR, developed for geophysics by Eckart 1960, and applied to stellar pulsations by Berthomieu et al. 1978). It neglects the centrifugal distortion and part of the contributions of the Corio ...
... ten computed assuming simplifying hypotheses. This is the case with the traditional approximation of rotation (TAR, developed for geophysics by Eckart 1960, and applied to stellar pulsations by Berthomieu et al. 1978). It neglects the centrifugal distortion and part of the contributions of the Corio ...
Spectroscopic Studies of Evolved Stars and Planetary Nebulae
... Evolved stars and planetary nebulae are rich and varied sites of molecule and dust formation. These objects undergo dramatic mass loss which ultimately enriches the interstellar medium. In this thesis, a number of studies, outlined below, have been undertaken to better understand the chemical and ph ...
... Evolved stars and planetary nebulae are rich and varied sites of molecule and dust formation. These objects undergo dramatic mass loss which ultimately enriches the interstellar medium. In this thesis, a number of studies, outlined below, have been undertaken to better understand the chemical and ph ...
THE NEW GALAXY: Signatures of Its Formation
... to a disk for the first time. Two key observations emphasize what we consider to be the mystery of the main epoch of baryon dissipation. First, there are no stars with [Fe/H] < −2.2 that rotate with the disk. Second, despite all the activity associated with the Golden Age, at least 80% of the baryon ...
... to a disk for the first time. Two key observations emphasize what we consider to be the mystery of the main epoch of baryon dissipation. First, there are no stars with [Fe/H] < −2.2 that rotate with the disk. Second, despite all the activity associated with the Golden Age, at least 80% of the baryon ...
A Detection Method for Small Kuiper Belt Objects: The Search for
... a power law ρ −q (where ρ is the KBO radius) with an index q ≈ 4 (Luu and Jewitt 1998). This value is compatible with the guess that the Kuiper belt is the “reservoir” of short-period comets. The total mass of these Kuiper belt objects (called KBOs hereinafter) is estimated from 0.1 to 0.3 Earth mas ...
... a power law ρ −q (where ρ is the KBO radius) with an index q ≈ 4 (Luu and Jewitt 1998). This value is compatible with the guess that the Kuiper belt is the “reservoir” of short-period comets. The total mass of these Kuiper belt objects (called KBOs hereinafter) is estimated from 0.1 to 0.3 Earth mas ...
Chapter 4 The Formation of Population III stars in a ΛCDM universe
... in Section 2.2.5, following 9 separate species including molecular hydrogen (but excluding deuterium). Adaptive mesh refinement is turned on such that cells are refined by factors of two along each axis, with a maximum of 22 total levels of refinement. This corresponds to a maximum resolution of (11 ...
... in Section 2.2.5, following 9 separate species including molecular hydrogen (but excluding deuterium). Adaptive mesh refinement is turned on such that cells are refined by factors of two along each axis, with a maximum of 22 total levels of refinement. This corresponds to a maximum resolution of (11 ...
DISSERTATION
... This thesis deals with the comparison of interferometric data of Asymptotic Giant Branch (AGB) stars with hydrostatic and dynamic model atmospheres. The AGB is the late evolutionary stage of stars with masses below 8 M! . These stars are characterised by a C-O degenerated core and 2 shell with ongoi ...
... This thesis deals with the comparison of interferometric data of Asymptotic Giant Branch (AGB) stars with hydrostatic and dynamic model atmospheres. The AGB is the late evolutionary stage of stars with masses below 8 M! . These stars are characterised by a C-O degenerated core and 2 shell with ongoi ...
Black hole tidal problem in the Fermi normal coordinates
... Here, Q ≡ m/M . Thus, with increasing the mass ratio Q, the critical value of R/r for the tidal disruption increases: ...
... Here, Q ≡ m/M . Thus, with increasing the mass ratio Q, the critical value of R/r for the tidal disruption increases: ...
It is now well known that the constellations of the Zodiac
... The stars rising around the time of the summer solstice are thus fittingly informed by images of death, war and travel between the worlds. The Serpent is one of the primary symbols of death and the underworld. Like its Greek counterpart, the Hydra, the Babylonian Serpent was set in the heavens to gu ...
... The stars rising around the time of the summer solstice are thus fittingly informed by images of death, war and travel between the worlds. The Serpent is one of the primary symbols of death and the underworld. Like its Greek counterpart, the Hydra, the Babylonian Serpent was set in the heavens to gu ...
Global structure and kinematics of stellar haloes in cosmological
... hybrid methods. Finally, hybrid models appear to overproduce the degree of substructure seen in the stellar halo of the Milky Way (e.g., Helmi et al. 2011; Xue et al. 2011). Hybrid models implicitly assume that the spheroid is built entirely of the tidal disruption of infalling satellites, they do n ...
... hybrid methods. Finally, hybrid models appear to overproduce the degree of substructure seen in the stellar halo of the Milky Way (e.g., Helmi et al. 2011; Xue et al. 2011). Hybrid models implicitly assume that the spheroid is built entirely of the tidal disruption of infalling satellites, they do n ...
Properties of Galactic B supergiants
... redward track after 5.1 Myr, i.e. [N/O] = +1.2 dex, in perfect agreement with the mean nebular and stellar CMFGEN results. For the post-RSG stage after 5.2 Myr, [N/O] = +1.8 dex is predicted. Consequently, Sher 25 is consistent with a single star evolving towards the RSG phase. However, amongst the ...
... redward track after 5.1 Myr, i.e. [N/O] = +1.2 dex, in perfect agreement with the mean nebular and stellar CMFGEN results. For the post-RSG stage after 5.2 Myr, [N/O] = +1.8 dex is predicted. Consequently, Sher 25 is consistent with a single star evolving towards the RSG phase. However, amongst the ...
The Formation and Early Evolution of Young Massive Clusters
... cluster properties (e.g. Bressert et al. 2010), suggests that YMCs merely represent extreme examples of their less massive and dense counterparts – open clusters. As such, characterizing and understanding how YMCs form is critical to help make the connection between the range of physical conditions ...
... cluster properties (e.g. Bressert et al. 2010), suggests that YMCs merely represent extreme examples of their less massive and dense counterparts – open clusters. As such, characterizing and understanding how YMCs form is critical to help make the connection between the range of physical conditions ...
Main sequence
In astronomy, the main sequence is a continuous and distinctive band of stars that appears on plots of stellar color versus brightness. These color-magnitude plots are known as Hertzsprung–Russell diagrams after their co-developers, Ejnar Hertzsprung and Henry Norris Russell. Stars on this band are known as main-sequence stars or ""dwarf"" stars.After a star has formed, it generates thermal energy in the dense core region through the nuclear fusion of hydrogen atoms into helium. During this stage of the star's lifetime, it is located along the main sequence at a position determined primarily by its mass, but also based upon its chemical composition and other factors. All main-sequence stars are in hydrostatic equilibrium, where outward thermal pressure from the hot core is balanced by the inward pressure of gravitational collapse from the overlying layers. The strong dependence of the rate of energy generation in the core on the temperature and pressure helps to sustain this balance. Energy generated at the core makes its way to the surface and is radiated away at the photosphere. The energy is carried by either radiation or convection, with the latter occurring in regions with steeper temperature gradients, higher opacity or both.The main sequence is sometimes divided into upper and lower parts, based on the dominant process that a star uses to generate energy. Stars below about 1.5 times the mass of the Sun (or 1.5 solar masses (M☉)) primarily fuse hydrogen atoms together in a series of stages to form helium, a sequence called the proton–proton chain. Above this mass, in the upper main sequence, the nuclear fusion process mainly uses atoms of carbon, nitrogen and oxygen as intermediaries in the CNO cycle that produces helium from hydrogen atoms. Main-sequence stars with more than two solar masses undergo convection in their core regions, which acts to stir up the newly created helium and maintain the proportion of fuel needed for fusion to occur. Below this mass, stars have cores that are entirely radiative with convective zones near the surface. With decreasing stellar mass, the proportion of the star forming a convective envelope steadily increases, whereas main-sequence stars below 0.4 M☉ undergo convection throughout their mass. When core convection does not occur, a helium-rich core develops surrounded by an outer layer of hydrogen.In general, the more massive a star is, the shorter its lifespan on the main sequence. After the hydrogen fuel at the core has been consumed, the star evolves away from the main sequence on the HR diagram. The behavior of a star now depends on its mass, with stars below 0.23 M☉ becoming white dwarfs directly, whereas stars with up to ten solar masses pass through a red giant stage. More massive stars can explode as a supernova, or collapse directly into a black hole.