11,149 research outputs found
Continuation methods for nonlinear equations
Feasibility of overcoming local convergent nature of continuation methods for nonlinear equation
Isolated elliptical galaxies in the local Universe
We have studied a sample of 89 very isolated, elliptical galaxies at z < 0.08
and compared their properties with elliptical galaxies located in a
high-density environment such as the Coma supercluster. Our aim is to probe the
role of environment on the morphological transformation and quenching of
elliptical galaxies as a function of mass. In addition, we elucidate the nature
of a particular set of blue and star-forming isolated ellipticals identified
here. We study physical properties of ellipticals such as color, specific star
formation rate, galaxy size, and stellar age, as a function of stellar mass and
environment based on SDSS data. We analyze the blue star-forming isolated
ellipticals in more detail, through photometric characterization using GALFIT,
and infer their star formation history using STARLIGHT. Among the isolated
ellipticals ~ 20% are blue, 8% are star forming, and ~ 10% are recently
quenched, while among the Coma ellipticals ~ 8% are blue and just <= 1% are
star forming or recently quenched. There are four isolated galaxies (~ 4.5%)
that are blue and star forming at the same time. These galaxies, with masses
between 7 x 10^9 and 2 x 10^10 h-2 M_sun, are also the youngest galaxies with
light-weighted stellar ages <= 1 Gyr and exhibit bluer colors toward the galaxy
center. Around 30-60% of their present-day luminosity, but only < 5% of their
present-day mass, is due to star formation in the last 1 Gyr. The processes of
morphological transformation and quenching seem to be in general independent of
environment since most of elliptical galaxies are 'red and dead', although the
transition to the red sequence should be faster for isolated ellipticals. In
some cases, the isolated environment seems to propitiate the rejuvenation of
ellipticals by recent (< 1 Gyr) cold gas accretion.Comment: 23 pages, 15 figures (16 pages and 9 figures without appendices).
A&A, in pres
Irreversible magnetization under rotating fields and lock-in effect on ErBa_2Cu_3O_7 single crystal with columnar defects
We have measured the irreversible magnetization M_i of an ErBa_2Cu_3O_7
single crystal with columnar defects (CD), using a technique based on sample
rotation under a fixed magnetic field H. This method is valid for samples whose
magnetization vector remains perpendicular to the sample surface over a wide
angle range - which is the case for platelets and thin films - and presents
several advantages over measurements of M_L(H) loops at fixed angles. The
resulting M_i(\Theta) curves for several temperatures show a peak in the CD
direction at high fields. At lower fields, a very well defined plateau
indicative of the vortex lock-in to the CD develops. The H dependence of the
lock-in angle \phi_L follows the H^{-1} theoretical prediction, while the
temperature dependence is in agreement with entropic smearing effects
corresponding to short range vortex-defects interactions.Comment: 7 pages, 6 figures, to be published in Phys. Rev.
Anomalous infrared spectra of hybridized phonons in type-I clathrate BaGaGe
The optical conductivity spectra of the rattling phonons in the clathrate
BaGaGe are investigated in detail by use of the terahertz
time-domain spectroscopy. The experiment has revealed that the lowest-lying
vibrational mode of a Ba(2) ion consists of a sharp Lorentzian peak at
1.2 THz superimposed on a broad tail weighted in the lower frequency regime
around 1.0 THz. With decreasing temperature, an unexpected linewidth broadening
of the phonon peak is observed, together with monotonic softening of the phonon
peak and the enhancement of the tail structure. These observed anomalies are
discussed in terms of impurity scattering effects on the hybridized phonon
system of rattling and acoustic phonons.Comment: Submitted to JPS
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