13,545 research outputs found
The oxygen abundance in the IFU era
Spatially-resolved information of gas-phase emission provided by integral
field units (IFUs) are allowing us to perform a new generation of emission-line
surveys, based on large samples of HII regions and full two-dimensional
coverage. Here we present two highlights of our current studies employing this
technique: 1) A statistical approach to the abundance gradients of spiral
galaxies, which indicates an -universal- radial gradient for oxygen abundance;
and 2) The discovery of a new scaling relation of HII regions in spiral
galaxies, the "local" mass-metallicity relation of star-forming galaxies.Comment: 6 pages, to appear in Highlights of Spanish Astrophysics VII,
Proceedings of the X Scientific Meeting of the Spanish Astronomical Society
held on July 9-13, 2012, in Valencia, Spai
Synchronization in a ring of pulsating oscillators with bidirectional couplings
We study the dynamical behavior of an ensemble of oscillators interacting
through short range bidirectional pulses. The geometry is 1D with periodic
boundary conditions. Our interest is twofold. To explore the conditions
required to reach fully synchronization and to invewstigate the time needed to
get such state. We present both theoretical and numerical results.Comment: Revtex, 4 pages, 2 figures. To appear in Int. J. Bifurc. and Chao
Inner and outer star forming regions over the disks of spiral galaxies. I. Sample characterization
Context. The knowledge of abundance distributions is central to understanding
the formation and evolution of galaxies. Most of the relations employed for the
derivation of gas abundances have so far been derived from observations of
outer disk HII regions, despite the known differences between inner and outer
regions. Aims. Using integral field spectroscopy (IFS) observations we aim to
perform a systematic study and comparison of two inner and outer HII regions
samples. The spatial resolution of the IFS, the number of objects and the
homogeneity and coherence of the observations allow a complete characterization
of the main observational properties and differences of the regions. Methods.
We analyzed a sample of 725 inner HII regions and a sample of 671 outer HII
regions, all of them detected and extracted from the observations of a sample
of 263 nearby, isolated, spiral galaxies observed by the CALIFA survey.
Results. We find that inner HII regions show smaller equivalent widths, greater
extinction and luminosities, along with greater values of
[NII]{\lambda}6583/H{\alpha} and [OII]{\lambda}3727/[OIII]{\lambda}5007
emission-line ratios, indicating higher metallicites and lower ionization
parameters. Inner regions have also redder colors and higher photometric and
ionizing masses, although Mion/Mphot is slighty higher for the outer regions.
Conclusions. This work shows important observational differences between inner
and outer HII regions in star forming galaxies not previously studied in
detail. These differences indicate that inner regions have more evolved stellar
populations and are in a later evolution state with respect to outer regions,
which goes in line with the inside-out galaxy formation paradigm.Comment: 16 page
PPAK Wide-field Integral Field Spectroscopy of NGC 628: II. Emission line abundance analysis
In this second paper of the series, we present the 2-dimensional (2D)
emission line abundance analysis of NGC 628, the largest object within the PPAK
Integral Field Spectroscopy (IFS) Nearby Galaxies Survey: PINGS. We introduce
the methodology applied to the 2D IFS data in order to extract and deal with
large spectral samples, from which a 2D abundance analysis can be later
performed. We obtain the most complete and reliable abundance gradient of the
galaxy up-to-date, by using the largest number of spectroscopic points sampled
in the galaxy, and by comparing the statistical significance of different
strong-line metallicity indicators. We find features not previously reported
for this galaxy that imply a multi-modality of the abundance gradient
consistent with a nearly flat-distribution in the innermost regions of the
galaxy, a steep negative gradient along the disc and a shallow gradient or
nearly-constant metallicity beyond the optical edge of the galaxy. The N/O
ratio seems to follow the same radial behaviour. We demonstrate that the
observed dispersion in metallicity shows no systematic dependence with the
spatial position, signal-to-noise or ionization conditions, implying that the
scatter in abundance for a given radius is reflecting a true spatial physical
variation of the oxygen content. Furthermore, by exploiting the 2D IFS data, we
were able to construct the 2D metallicity structure of the galaxy, detecting
regions of metal enhancement, and showing that they vary depending on the
choice of the metallicity estimator. The analysis of axisymmetric variations in
the disc of NGC 628 suggest that the physical conditions and the star formation
history of different-symmetric regions of the galaxy have evolved in a
different manner.Comment: Accepted for publication in MNRAS, 40 pages, 22 figures, online data:
http://www.ast.cam.ac.uk/ioa/research/ping
A search for hydrogenated fullerenes in fullerene-containing planetary nebulae
Detections of C60 and C70 fullerenes in planetary nebulae (PNe) of the
Magellanic Clouds and of our own Galaxy have raised the idea that other forms
of carbon such as hydrogenated fullerenes (fulleranes like C60H36 and C60H18),
buckyonions, and carbon nanotubes, may be widespread in the Universe. Here we
present VLT/ISAAC spectra (R ~600) in the 2.9-4.1 microns spectral region for
the Galactic PNe Tc 1 and M 1-20, which have been used to search for
fullerene-based molecules in their fullerene-rich circumstellar environments.
We report the non-detection of the most intense infrared bands of several
fulleranes around ~3.4-3.6 microns in both PNe. We conclude that if fulleranes
are present in the fullerene-containing circumstellar environments of these
PNe, then they seem to be by far less abundant than C60 and C70. Our
non-detections together with the (tentative) fulleranes detection in the
proto-PN IRAS 01005+7910 suggest that fulleranes may be formed in the short
transition phase between AGB stars and PNe but they are quickly destroyed by
the UV radiation field from the central star.Comment: Accepted for publication in Astronomy & Astrophysics (7 pages, 3
figures, and 3 Tables
A microscopic NN to NN*(1440) potential
By means of a NN to NN*(1440) transition potential derived in a
parameter-free way from a quark-model based NN potential, we determine
simultaneously the and coupling constants.
We also present a study of the target Roper excitation diagram contributing to
the reaction.Comment: Talk presented at the Fourth International Conference on Perspectives
in Hadronic Physics (ICTP, Trieste, Italy, May 2003). To appear in EPJA. 6
pages, 9 figures, needs svepj.clo and svjour.cl
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