9,773 research outputs found
Dependence of the Fundamental Plane Scatter on Galaxy Age
The fundamental plane (FP) has an intrinsic scatter that can not be explained
purely by observational errors. Using recently available age estimates for
nearby early type galaxies, we show that a galaxy's position relative to the FP
depends on its age. In particular, the mean FP corresponds to ellipticals with
an age of ~10 Gyr. Younger galaxies are systematically brighter with higher
surface brightness relative to the mean relation. Old ellipticals form an
`upper envelope' to the FP. For our sample of mostly non-cluster galaxies, age
can account for almost half of the scatter in the B band FP. Distance
determinations based on the FP may have a systematic bias, if the mean age of
the sample varies with redshift.
We also show that fundamental plane residuals, B-V colors and Mg_2 line
strength are consistent with an ageing central burst superposed on an old
stellar population. This reinforces the view that these age estimates are
tracing the last major episode of star formation induced by a gaseous merger
event. We briefly discuss the empirical `evolutionary tracks' of
merger-remnants and young ellipticals in terms of their key observational
parameters.Comment: 14 pages, Latex, 2 figures, accepted by ApJ Letter
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Improved Log(gf) Values for Lines of Ti I and Abundance Determinations in the Photospheres of the Sun and Metal-Poor Star HD 84937 (Accurate Transition Probabilities for Ti I)
New atomic transition probability measurements for 948 lines of Ti I are reported. Branching fractions from Fourier transform spectra and from spectra recorded using a 3 m echelle spectrometer are combined with published radiative lifetimes from laser-induced fluorescence measurements to determine these transition probabilities. Generally good agreement is found in comparisons to the NIST Atomic Spectra Database. The new Ti I data are applied to re-determine the Ti abundance in the photospheres of the Sun and metal-poor star HD 84937 using many lines covering a range of wavelength and excitation potential to explore possible non-local thermal equilibrium effects. The variation of relative Ti/Fe abundance with metallicity in metal-poor stars observed in earlier studies is supported in this study.NSF AST-1211055, AST-0908978, AST-1211585NSF REU grant AST-1004881ESO Science Archive Facility 073.D-0024, 266.D-5655NASA NAS 5-26555Astronom
Optimum take-off angle in the long jump
In this study, we found that the optimum take-off angle for a long jumper may be predicted by combining the equation for the range of a projectile in free flight with the measured relations between take-off speed, take-off height and take-off angle for the athlete. The prediction method was evaluated using video measurements of three experienced male long jumpers who performed maximum-effort jumps over a wide range of take-off angles. To produce low take-off angles the athletes used a long and fast run-up, whereas higher take-off angles were produced using a progressively shorter and slower run-up. For all three athletes, the take-off speed decreased and the take-off height increased as the athlete jumped with a higher take-off angle. The calculated optimum take-off angles were in good agreement with the athletes' competition take-off angles
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Bioinspired snapping-claw apparatus to study hydrodynamic cavitation effects on the corrosion of metallic samples
A creative low-cost and compact mechanical device that mimics the rapid closure of the pistol shrimp claw was used to conduct electrochemical experiments, in order to study the effects of hydrodynamic cavitation on the corrosion of aluminum and steel samples. Current-time curves show significant changes associated with local variations in dissolved O2 concentration, cavitation-induced erosion and changes in the nature of the surface corrosion products
\u3cem\u3eβ\u3c/em\u3e-Homopipitzolone
The structure of β-homopipitzolone (one of the two isomers of an intermediate product in the homocedrole synthesis) has been unequivocally established as 1 O-hydroxy-2,6,9-trimetbyltricyclo[6.3.1.01,6] dodeca-9-ene-5, II, 12-trione with relative IR,2R,6R,8S configuration
The Nature of Nearby Counterparts to Intermediate Redshift Luminous Compact Blue Galaxies I. Optical/H I Properties and Dynamical Masses
We present single-dish H I spectra obtained with the Green Bank Telescope,
along with optical photometric properties from the Sloan Digital Sky Survey, of
20 nearby (D < 70 Mpc) Luminous Compact Blue Galaxies (LCBGs). These ~L*, blue,
high surface brightness, starbursting galaxies were selected with the same
criteria used to define LCBGs at higher redshifts. We find these galaxies are
gas-rich, with M(HI) ranging from 5*10^8 to 8*10^9 M_sun, and M(HI)/L_B ranging
from 0.2 to 2 M_sun/L_sun, consistent with a variety of morphological types of
galaxies. We find the dynamical masses (measured within R_25) span a wide
range, from 3*10^9 to 1*10^11 M_sun. However, at least half have dynamical
mass-to-light ratios smaller than nearby galaxies of all Hubble types, as found
for LCBGs at intermediate redshifts. By comparing line widths and effective
radii with local galaxy populations, we find that LCBGs are consistent with the
dynamical mass properties of Magellanic (low luminosity) spirals, and the more
massive irregulars and dwarf ellipticals, such as NGC 205.Comment: 33 pages, 8 figures, accepted by Ap
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