4,534 research outputs found
Rotation curves and metallicity gradients from HII regions in spiral galaxies
In this paper we study long slit spectra in the region of H emission
line of a sample of 111 spiral galaxies with recognizable and well defined
spiral morphology and with a well determined environmental status, ranging from
isolation to non-disruptive interaction with satellites or companions. The form
and properties of the rotation curves are considered as a function of the
isolation degree, morphological type and luminosity. The line ratios are used
to estimate the metallicity of all the detected HII regions, thus producing a
composite metallicity profile for different types of spirals. We have found
that isolated galaxies tend to be of later types and lower luminosity than the
interacting galaxies. The outer parts of the rotation curves of isolated
galaxies tend to be flatter than in interacting galaxies, but they show similar
relations between global parameters. The scatter of the Tully-Fisher relation
defined by isolated galaxies is significantly lower than that of interacting
galaxies. The [NII]/H ratios, used as metallicity indicator, show a
clear trend between Z and morphological type, t, with earlier spirals showing
larger ratios; this trend is tighter when instead of t the gradient of the
inner rotation curve, G, is used; no trend is found with the interaction
status. The Z-gradient of the disks depends on the type, being almost flat for
early spirals, and increasing for later types. The [NII]/H ratios
measured for disk HII regions of interacting galaxies are higher than for
normal/isolated objects, even if all the galaxy families present similar
distributions of H Equivalent Width.Comment: accepted for publication in A&A (tables for HII region parameters
incomplete, contact [email protected] for the whole set of tables
Development and evaluation of a prototype global volcano surveillance system utilizing the ERTS-1 satellite data collection system
There are no author-identified significant results in this report
Modulating motor learning through transcranial direct-current stimulation: An integrative view
Motor learning consists of the ability to improve motor actions through practice playing a major role in the acquisition of skills required for high-performance sports or motor function recovery after brain lesions. During the last decades, it has been reported that transcranial direct-current stimulation (tDCS), consisting in applying weak direct current through the scalp, is able of inducing polarity-specific changes in the excitability of cortical neurons. This low-cost, painless and well-tolerated portable technique has found a wide-spread use in the motor learning domain where it has been successfully applied to enhance motor learning in healthy individuals and for motor recovery after brain lesion as well as in pathological states associated to motor deficits. The main objective of this mini-review is to offer an integrative view about the potential use of tDCS for human motor learning modulation. Furthermore, we introduce the basic mechanisms underlying immediate and long-term effects associated to tDCS along with important considerations about its limitations and progression in recent years
The Broad Line Radio Galaxy J2114+820
In the frame of the study of a new sample of large angular size radio
galaxies selected from the NRAO VLA Sky Survey, we have made radio observations
of J2114+820, a low power radio galaxy with an angular size of 6'. Its radio
structure basically consists of a prominent core, a jet directed in north-west
direction and two extended S-shaped lobes. We have also observed the optical
counterpart of J2114+820, a bright elliptical galaxy with a strong unresolved
central component. The optical spectrum shows broad emission lines. This fact,
together with its low radio power and FR-I type morphology, renders J2114+820 a
non-trivial object from the point of view of the current unification schemes of
radio loud active galactic nuclei.Comment: 6 pages, 5 figures. To appear in the proceedings of EVN/JIVE
Symposium No. 4, New Astronomy Reviews (eds. Garrett et al.
FORGE enabling FIRE facilities for the eLearning community
International audienceMany engineering students at third-level institutions across the world will not have the advantage of using real-world experimentation equipment, as the infrastructure and resources required for this activity are too expensive. This paper explains how the FORGE (Forging Online Education through FIRE) FP7 project transforms Future Internet Research and Experimentation (FIRE) testbed facilities into educational resources for the eLearning community. This is achieved by providing a framework for remote experimentation that supports easy access and control to testbed infrastructure for students and educators. Moreover, we identify a list of recommendations to support development of eLearning courses that access these facilities and highlight some of the challenges encountered by FORGE
Active galactic nuclei synapses: X-ray versus optical classifications using artificial neural networks
(Abridged) Many classes of active galactic nuclei (AGN) have been defined
entirely throughout optical wavelengths while the X-ray spectra have been very
useful to investigate their inner regions. However, optical and X-ray results
show many discrepancies that have not been fully understood yet. The aim of
this paper is to study the "synapses" between the X-ray and optical
classifications.
For the first time, the new EFLUXER task allowed us to analyse broad band
X-ray spectra of emission line nuclei (ELN) without any prior spectral fitting
using artificial neural networks (ANNs). Our sample comprises 162 XMM-Newton/pn
spectra of 90 local ELN in the Palomar sample. It includes starbursts (SB),
transition objects (T2), LINERs (L1.8 and L2), and Seyferts (S1, S1.8, and S2).
The ANNs are 90% efficient at classifying the trained classes S1, S1.8, and
SB. The S1 and S1.8 classes show a wide range of S1- and S1.8-like components.
We suggest that this is related to a large degree of obscuration at X-rays. The
S1, S1.8, S2, L1.8, L2/T2/SB-AGN (SB with indications of AGN), and SB classes
have similar average X-ray spectra within each class, but these average spectra
can be distinguished from class to class. The S2 (L1.8) class is linked to the
S1.8 (S1) class with larger SB-like component than the S1.8 (S1) class. The L2,
T2, and SB-AGN classes conform a class in the X-rays similar to the S2 class
albeit with larger fractions of SB-like component. This SB-like component is
the contribution of the star-formation in the host galaxy, which is large when
the AGN is weak. An AGN-like component seems to be present in the vast majority
of the ELN, attending to the non-negligible fraction of S1-like or S1.8-like
component. This trained ANN could be used to infer optical properties from
X-ray spectra in surveys like eRosita.Comment: 15 pages, 7 figures, accepted for publication in A&A. Appendix B only
in the full version of the paper here:
https://dl.dropboxusercontent.com/u/3484086/AGNSynapsis_OGM_online.pd
âItâs Just a New Way of Looking at Learningâ: Evaluation of the Mediating Learning Support Assistant (MeLSA) Training Programme
This feasibility study evaluated the Mediating Learning Support Assistant (MeLSA) training programme. Two cohorts (N = 16) of learning support staff (teaching assistants and learning support assistants) completed the MeLSA training programme that consisted of six-day sessions delivered over six weeks. The MeLSA training content focuses on applying psychology to support childrenâs learning within schools. Feedback was gathered from four learning support staff, using semi-structured interviews to evaluate the training programme. The interviews were analysed thematically. Learning support staff reported on the impact of MeLSA on developing psychologically informed thinking, valued aspects of, and suggested improvements for, the training programme, and the implementation of MeLSA in schools. Facilitating school staff to mediate learning through providing training is discussed as an effective approach for educational psychologists to support children and young people to become independent and competent learners
Near-Infrared and Star-forming properties of Local Luminous Infrared Galaxies
We use HST NICMOS continuum and Pa-alpha observations to study the
near-infrared and star-formation properties of a representative sample of 30
local (d ~ 35-75Mpc) luminous infrared galaxies (LIRGs, infrared 8-1000um
luminosities of L_IR=11-11.9[Lsun]). The data provide spatial resolutions of
25-50pc and cover the central ~3.3-7.1kpc regions of these galaxies. About half
of the LIRGs show compact (~1-2kpc) Pa-alpha emission with a high surface
brightness in the form of nuclear emission, rings, and mini-spirals. The rest
of the sample show Pa-alpha emission along the disk and the spiral arms
extending over scales of 3-7kpc and larger. About half of the sample contains
HII regions with H-alpha luminosities significantly higher than those observed
in normal galaxies. There is a linear empirical relationship between the mid-IR
24um and hydrogen recombination (extinction-corrected Pa-alpha) luminosity for
these LIRGs, and the HII regions in the central part of M51. This relation
holds over more than four decades in luminosity suggesting that the mid-IR
emission is a good tracer of the star formation rate (SFR). Analogous to the
widely used relation between the SFR and total IR luminosity of Kennicutt
(1998), we derive an empirical calibration of the SFR in terms of the
monochromatic 24um luminosity that can be used for luminous, dusty galaxies.Comment: Accepted for publication in ApJ. Contact first author for high
qualitity version of figure
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