this article
... 15 foreground stars common to both images. This scale factor, however, often needs adjustments, since the foreground stars and the galaxy are sometimes different in color. Adjustments were made iteratively until a satisfactory subtraction was obtained for the majority of the galaxy. The application ...
... 15 foreground stars common to both images. This scale factor, however, often needs adjustments, since the foreground stars and the galaxy are sometimes different in color. Adjustments were made iteratively until a satisfactory subtraction was obtained for the majority of the galaxy. The application ...
Lyman-alpha imaging of starburst galaxies in the local universe and beyond Matthew Hayes
... faint and angular separations too small for stars to be observed individually and observers must instead rely upon the integrated stellar light from galaxies. Fortunately galaxies, at least the bright ones, can be observed out to the very large distances and the current record-holding galaxy candida ...
... faint and angular separations too small for stars to be observed individually and observers must instead rely upon the integrated stellar light from galaxies. Fortunately galaxies, at least the bright ones, can be observed out to the very large distances and the current record-holding galaxy candida ...
the mass distribution and lifetime of prestellar cores in perseus
... (2007) find a turnover in the CMD of starless SCUBA 850 m cores at 1.3 M. Those authors relate this turnover to a downturn in the Kroupa (2002) IMF at 0.1 M, and infer a much lower core-to-star efficiency of 6%. Large samples of prestellar cores are important for further addressing these proble ...
... (2007) find a turnover in the CMD of starless SCUBA 850 m cores at 1.3 M. Those authors relate this turnover to a downturn in the Kroupa (2002) IMF at 0.1 M, and infer a much lower core-to-star efficiency of 6%. Large samples of prestellar cores are important for further addressing these proble ...
The effect of stellar limb darkening values on the accuracy of the
... Some modellers fix the limb darkening coefficients according to these or other tables when they fit a transit curve. As is clear from the aforementioned discrepancies, in some temperature regions this is not a good strategy because the values of the limb darkening coefficients are not consistent and ...
... Some modellers fix the limb darkening coefficients according to these or other tables when they fit a transit curve. As is clear from the aforementioned discrepancies, in some temperature regions this is not a good strategy because the values of the limb darkening coefficients are not consistent and ...
The Observer`s Guide to the Gamma-Ray Burst
... to have a tighter grouping of velocities than Fe ii λ5169, though SN 2010bh is a notable outlier, being roughly 15,000 to 20,000 km s−1 more rapid than the other GRB-SNe. SN 2013ez is also a notable outlier due to its low line velocity (4000 − 6000 km s−1 ), and inspection of its spectrum (Fig. 5) r ...
... to have a tighter grouping of velocities than Fe ii λ5169, though SN 2010bh is a notable outlier, being roughly 15,000 to 20,000 km s−1 more rapid than the other GRB-SNe. SN 2013ez is also a notable outlier due to its low line velocity (4000 − 6000 km s−1 ), and inspection of its spectrum (Fig. 5) r ...
Watson et al. 2007a - Department of Physics and Astronomy
... free, several-AU-scale, central clearings or radial gaps are inferred from absence of infrared excess at the shorter IRS wavelengths. As we have discussed elsewhere (Forrest et al. 2004, d’Alessio et al. 2005, Calvet et al. 2005), the interstellar-like silicate profile is explained naturally in a le ...
... free, several-AU-scale, central clearings or radial gaps are inferred from absence of infrared excess at the shorter IRS wavelengths. As we have discussed elsewhere (Forrest et al. 2004, d’Alessio et al. 2005, Calvet et al. 2005), the interstellar-like silicate profile is explained naturally in a le ...
A SUB-SATURN MASS PLANET ORBITING HD 36511 Debra A
... Doppler precision. The Doppler shifts of our spectra are determined with the spectral synthesis technique described by Butler et al. (1996). Individual observations at Lick Observatory (particularly from the CAT) have photon-limited errors with a signalto-noise ratio of less than 100, so two or thre ...
... Doppler precision. The Doppler shifts of our spectra are determined with the spectral synthesis technique described by Butler et al. (1996). Individual observations at Lick Observatory (particularly from the CAT) have photon-limited errors with a signalto-noise ratio of less than 100, so two or thre ...
Galaxy Formation and Evolution.
... This publication is in copyright. Subject to statutory exception and to the provision of relevant collective licensing agreements, no reproduction of any part may take place without the written permission of Cambridge University Press. ...
... This publication is in copyright. Subject to statutory exception and to the provision of relevant collective licensing agreements, no reproduction of any part may take place without the written permission of Cambridge University Press. ...
DENSE CORES IN PERSEUS - Harvard
... quiescent. The critical density of ammonia is roughly 104 cm−3 (Ho & Townes 1983), so objects detected in NH3 are typically at or above this density and thus more dense than the bulk of the molecular cloud. Ammonia also provides one piece of the stability puzzle, namely how much internal non-thermal ...
... quiescent. The critical density of ammonia is roughly 104 cm−3 (Ho & Townes 1983), so objects detected in NH3 are typically at or above this density and thus more dense than the bulk of the molecular cloud. Ammonia also provides one piece of the stability puzzle, namely how much internal non-thermal ...
relative age difference between the metal
... analysis. From the present analysis, the relative ages of M53 and M92 are derived using the ∆(B − V ) method reported by VandenBerg et al. The relative age of M53 is found to be 1.6 ± 0.85 Gyr younger than that of M92 if the absolute age of M92 is taken to be 14 Gyr. This relative age difference bet ...
... analysis. From the present analysis, the relative ages of M53 and M92 are derived using the ∆(B − V ) method reported by VandenBerg et al. The relative age of M53 is found to be 1.6 ± 0.85 Gyr younger than that of M92 if the absolute age of M92 is taken to be 14 Gyr. This relative age difference bet ...
Dust attenuation up to z ≃ 2 in the AKARI North Ecliptic Pole Deep
... selected using different criteria will give us a global picture of the attenuation at work in star-forming galaxies and its evolution with redshift. Methods. We selected galaxies in the mid-IR from the deep survey of the North Ecliptic Field performed by the AKARI satellite. Using multiple filters o ...
... selected using different criteria will give us a global picture of the attenuation at work in star-forming galaxies and its evolution with redshift. Methods. We selected galaxies in the mid-IR from the deep survey of the North Ecliptic Field performed by the AKARI satellite. Using multiple filters o ...
Protoplanetary Disks and Their Evolution
... et al. 1999) have not been confirmed with interferometry, however, thus challenging theoretical understanding (Hughes et al. 2009b). Numerical models of both magnetic and nonmagnetic collapsing molecular cores show disks form rapidly, within ∼104 years (Yorke, Bodenheimer & Laughlin 1993, Hueso & Gui ...
... et al. 1999) have not been confirmed with interferometry, however, thus challenging theoretical understanding (Hughes et al. 2009b). Numerical models of both magnetic and nonmagnetic collapsing molecular cores show disks form rapidly, within ∼104 years (Yorke, Bodenheimer & Laughlin 1993, Hueso & Gui ...
The recent star-formation history of the Large and Small Magellanic
... that, a field at 2.3◦ is currently active in star-formation, while fields at 4.4◦ , 5.5◦, and 7.1◦ have 100 Myr, 0.8 Gyr, and 1.5 Gyr old stars as the youngest population, respectively. Thus, the age of the youngest stars in each field gradually increases with distance from the center and the popula ...
... that, a field at 2.3◦ is currently active in star-formation, while fields at 4.4◦ , 5.5◦, and 7.1◦ have 100 Myr, 0.8 Gyr, and 1.5 Gyr old stars as the youngest population, respectively. Thus, the age of the youngest stars in each field gradually increases with distance from the center and the popula ...
Modeling Spatially and Spectrally Resolved Observations to
... This thesis owes much to the support of my officemate, Zach Berta, for five years of advice on life, computers, and astronomy. I thank Diego Muñoz, Robert Harris, Ragnhild Lunnan, and Sarah Rugheimer for countless snack and coffee breaks; Wen-fai Fong and Nick Stone for leading camping trips and t ...
... This thesis owes much to the support of my officemate, Zach Berta, for five years of advice on life, computers, and astronomy. I thank Diego Muñoz, Robert Harris, Ragnhild Lunnan, and Sarah Rugheimer for countless snack and coffee breaks; Wen-fai Fong and Nick Stone for leading camping trips and t ...
Infrared identification of high-mass X
... the IRAF noao.digiphot.daophot package. After evaluating an aperture correction for each filter and each object (due to the difference of aperture radius used to perform photometry on standard stars and targets) and knowing the zero-point values, we derived the apparent magnitude of the targets in t ...
... the IRAF noao.digiphot.daophot package. After evaluating an aperture correction for each filter and each object (due to the difference of aperture radius used to perform photometry on standard stars and targets) and knowing the zero-point values, we derived the apparent magnitude of the targets in t ...
Pluto: improved astrometry from 19 years of observations ⋆⋆⋆⋆⋆⋆
... Methods. All astrometric positions of Pluto were reduced with the Platform for Reduction of Astronomical Images Automatically (PRAIA), using the USNO CCD Astrograph Catalogue 4 (UCAC4) as the reference catalog. We also used the planetary ephemeris DE421+plu021 for comparisons. The positions were cor ...
... Methods. All astrometric positions of Pluto were reduced with the Platform for Reduction of Astronomical Images Automatically (PRAIA), using the USNO CCD Astrograph Catalogue 4 (UCAC4) as the reference catalog. We also used the planetary ephemeris DE421+plu021 for comparisons. The positions were cor ...
Th`ese d`astrophysique Chemodynamical Simulations of Evolution
... mass in our Galaxy and in dwarf galaxies. I have searched for dust (re-)processing by stars and in the interstellar medium, using both observations and results from semi-analytic models (eliminating few of their assumptions). Once my model was set up, I have performed simulations of a massive galaxy ...
... mass in our Galaxy and in dwarf galaxies. I have searched for dust (re-)processing by stars and in the interstellar medium, using both observations and results from semi-analytic models (eliminating few of their assumptions). Once my model was set up, I have performed simulations of a massive galaxy ...
Hubble Space Telescope Astrometry of the Procyon System
... positioned near the center of the PC chip, for input to the PSF determination. The approach we used is described in eqs. (2) and (3) of Gilliland et al. (1999). A uniform spatial grid on a scale finer than the native pixel size is first defined. (In this case, we chose a factor of 50 finer than the ...
... positioned near the center of the PC chip, for input to the PSF determination. The approach we used is described in eqs. (2) and (3) of Gilliland et al. (1999). A uniform spatial grid on a scale finer than the native pixel size is first defined. (In this case, we chose a factor of 50 finer than the ...
Formation and evolution of giant molecular clouds in a barred spiral
... Understanding where and how gas is converted into stars in a galaxy is important for understanding a galaxy’s formation and evolution through each epoch of the universe. Which physical processes control the star formation in a galaxy is heavily debated. We are now at a stage where it is possible to ...
... Understanding where and how gas is converted into stars in a galaxy is important for understanding a galaxy’s formation and evolution through each epoch of the universe. Which physical processes control the star formation in a galaxy is heavily debated. We are now at a stage where it is possible to ...
Ch a n d
... Pre-main-sequence stars exhibit complex magnetic activity, accretion, and various kinds of mass outflow. The impact of plasma onto the stellar surface from magnetospheric accretion streams, can be a dominant source of energy and momentum in the upper atmospheres of T Tauri stars. We present models i ...
... Pre-main-sequence stars exhibit complex magnetic activity, accretion, and various kinds of mass outflow. The impact of plasma onto the stellar surface from magnetospheric accretion streams, can be a dominant source of energy and momentum in the upper atmospheres of T Tauri stars. We present models i ...
arXiv:astro-ph/0703091v1 5 Mar 2007
... The nature of rapid neutron-capture nucleosynthesis (the r-process) and its contributions to the abundances of post iron-peak elements (Z > 30) were first delineated in pioneering studies by Cameron (1957) and Burbidge et al. (1957). The details, however, still remain to be worked out (e.g., see Tru ...
... The nature of rapid neutron-capture nucleosynthesis (the r-process) and its contributions to the abundances of post iron-peak elements (Z > 30) were first delineated in pioneering studies by Cameron (1957) and Burbidge et al. (1957). The details, however, still remain to be worked out (e.g., see Tru ...
The Destruction of an Oort Cloud in a rich stellar cluster
... of the galactic disk tide plus field star encounters. The effect of the resulting present Oort Cloud being dominated by a tight, inner core was confirmed as well as the possibility of obtaining a Sedna-type population due to the random effects of the closest stellar encounters. An often cited model ...
... of the galactic disk tide plus field star encounters. The effect of the resulting present Oort Cloud being dominated by a tight, inner core was confirmed as well as the possibility of obtaining a Sedna-type population due to the random effects of the closest stellar encounters. An often cited model ...
Thesis (complete) - Research Explorer
... the counterbalance due to pressure from the particles that constitute them. Energy produced by nuclear burning continuously replenishes what is lost by radiation and allows stars to remain in stable configurations for long periods of time. As these stars evolve they undergo many different processes ...
... the counterbalance due to pressure from the particles that constitute them. Energy produced by nuclear burning continuously replenishes what is lost by radiation and allows stars to remain in stable configurations for long periods of time. As these stars evolve they undergo many different processes ...
diplomov a prace - Univerzita Karlova
... primary is distorting the secondary. When two stars are moving closer, the secondary becomes more and more distorted until the material in the outer layers, which is nearest the primary, experiences a greater gravitational attraction towards the white dwarf then back towards its own star. In this ca ...
... primary is distorting the secondary. When two stars are moving closer, the secondary becomes more and more distorted until the material in the outer layers, which is nearest the primary, experiences a greater gravitational attraction towards the white dwarf then back towards its own star. In this ca ...
Comparing Single-Epoch Virial Black Hole Mass Estimators for
... to Mg II coverage in optical SDSS spectra and our own near-IR spectra covering Hβ and Hα. Our sample probes the high-luminosity regime (L5100 > 1045.4 erg s−1 ) of quasars, and thus such a study will provide confidence on estimating virial BH masses for the most luminous quasars (such as z & 6 quasa ...
... to Mg II coverage in optical SDSS spectra and our own near-IR spectra covering Hβ and Hα. Our sample probes the high-luminosity regime (L5100 > 1045.4 erg s−1 ) of quasars, and thus such a study will provide confidence on estimating virial BH masses for the most luminous quasars (such as z & 6 quasa ...
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.