50,109 research outputs found
Bar-induced central star formation as revealed by integral field spectroscopy from CALIFA
We investigate the recent star formation history (SFH) in the inner region of
57 nearly face-on spiral galaxies selected from the Calar Alto Legacy Integral
Field Area (CALIFA) survey. For each galaxy we use the integral field
spectroscopy from CALIFA to obtain two-dimensional maps and radial profiles of
three parameters that are sensitive indicators of the recent SFH: the 4000\AA\
break (D(4000)), and the equivalent width of H absorption
(EW(H)) and H emission (EW(H)). We have also
performed photometric decomposition of bulge/bar/disk components based on SDSS
optical image. We identify a class of 17 "turnover" galaxies whose central
region present significant drop in D(4000), and most of them
correspondingly show a central upturn in EW(H) and EW(H).
This indicates that the central region of the turnover galaxies has experienced
star formation in the past 1-2 Gyr, which makes the bulge younger and more
star-forming than surrounding regions. We find almost all (15/17) the turnover
galaxies are barred, while only half of the barred galaxies in our sample
(15/32) are classified as a turnover galaxy. This finding provides strong
evidence in support of the theoretical expectation that the bar may drive gas
from the disc inward to trigger star formation in galaxy center, an important
channel for the growth/rejuvenation of pseudobulges in disc galaxies.Comment: 19 pages, 10 figures, ApJ accepte
Signatures of strong correlation effects in RIXS on Cuprates
Recently, spin excitations in doped cuprates are measured using the resonant
inelastic X-ray scattering (RIXS). The paramagnon dispersions show the large
hardening effect in the electron-doped systems and seemingly
doping-independence in the hole-doped systems, with the energy scales
comparable to that of the antiferromagnetic magnons. This anomalous hardening
effect was partially explained by using the strong coupling t-J model but with
a three-site term(Nature communications 5, 3314 (2014)). However we show that
hardening effect is a signature of strong coupling physics even without
including this extra term. By considering the t-t'-t"-J model and using the
Slave-Boson (SB) mean field theory, we obtain, via the spin-spin
susceptibility, the spin excitations in qualitative agreement with the
experiments. These anomalies is mainly due to the doping-dependent bandwidth.
We further discuss the interplay between particle-hole-like and paramagnon-like
excitations in the RIXS measurements.Comment: 7 pages, 6 figure
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