1,838 research outputs found
H.E.S.S. deeper observations on SNR RX J0852.0-4622
Supernova Remnants (SNRs) are believed to be acceleration sites of Galactic
cosmic rays. Therefore, deep studies of these objects are instrumental for an
understanding of the high energy processes in our Galaxy. RX J0852.0-4622, also
known as Vela Junior, is one of the few (4) shell-type SNRs resolved at Very
High Energies (VHE; E > 100 GeV). It is one of the largest known VHE sources (~
1.0 deg radius) and its flux level is comparable to the flux level of the Crab
Nebula in the same energy band. These characteristics allow for a detailed
analysis, shedding further light on the high-energy processes taking place in
the remnant. In this document we present further details on the spatial and
spectral morphology derived with an extended data set. The analysis of the
spectral morphology of the remnant is compatible with a constant power-law
photon index of 2.11 +/- 0.05_stat +/- 0.20_syst from the whole SNR in the
energy range from 0.5 TeV to 7 TeV. The analysis of the spatial morphology
shows an enhanced emission towards the direction of the pulsar PSR J0855-4644,
however as the pulsar is lying on the rim of the SNR, it is difficult to
disentangle both contributions. Therefore, assuming a point source, the upper
limit on the flux of the pulsar wind nebula (PWN) between 1 TeV and 10 TeV, is
estimated to be ~ 2% of the Crab Nebula flux in the same energy range
VHE gamma-ray observations of the young synchrotron-dominated SNRs G1.9+0.3 and G330.2+1.0 with H.E.S.S
Supernova remnants (SNRs) are widely considered to be accelerators of cosmic
rays (CR). They are also expected to produce very-high-energy (VHE;
GeV) gamma rays through interactions of high-energy particles with the
surrounding medium and photon fields. They are, therefore, promising targets
for observations with ground-based imaging atmospheric Cherenkov telescopes
like the H.E.S.S. telescope array. VHE gamma-ray emission has already been
discovered from a number of SNRs, establishing them as a prominent source class
in the VHE domain. Of particular interest are the handful of SNRs whose X-ray
spectra are dominated by non-thermal synchrotron emission, such as the VHE
gamma-ray emitters RX J0852.0-4622 (Vela Jr.) and RX J1713-3946. The shell-type
SNRs G1.9+0.3 and G330.2+1.0 also belong to this subclass and are further
notable for their young ages ( kyr), especially G1.9+0.3, which was
recently determined to be the youngest SNR in the Galaxy ( yr). These
unique characteristics motivated investigations with H.E.S.S. to search for VHE
gamma rays. The results of the H.E.S.S. observations and analyses are
presented, along with implications for potential particle acceleration
scenarios.Comment: ICRC 2011 proceedings, 4 pages, 2 figures, 3 table
A detailed two-dimensional stellar population study of M32
We present Two-Dimensional Spectroscopy of the 9x12 arcsec^2 central region
of M32 obtained with the 2D_FIS fibre spectrograph installed at the William
Herschel Telescope. From these spectra line strength maps have been
reconstructed for about 20 absorption lines, mostly belonging to the Lick
system. We find good agreement with long-slit line strength profiles in the
literature. In contrast with previous studies, indices were azimuthally
averaged along continuum isophotes of M32. A remarkable result is that no
gradients are presented in the spectral indices. So, we have fitted the mean
values of each spectral index and central colours to the models of Vazdekis et
al. (1996) and Worthey (1994), finding that an intermediate age (~4 Gyr) and
metallicity similar to solar (Z=0.02) are the best fitted values for the
innermost region of M32.Comment: accepted in MNRA
Integrated spectra extraction based on signal-to-noise optimization using Integral Field Spectroscopy
We propose and explore the potential of a method to extract high
signal-to-noise (S/N) integrated spectra related to physical and/or
morphological regions on a 2-dimensional field using Integral Field
Spectroscopy (IFS) observations by employing an optimization procedure based on
either continuum (stellar) or line (nebular) emission features. The
optimization method is applied to a set of IFS VLT-VIMOS observations of
(U)LIRG galaxies, describing the advantages of the optimization by comparing
the results with a fixed-aperture, single spectrum case, and by implementing
some statistical tests. We demonstrate that the S/N of the IFS optimized
integrated spectra is significantly enhanced when compared with the single
aperture unprocessed case. We provide an iterative user-friendly and versatile
IDL algorithm that allows the user to spatially integrate spectra following
more standard procedures. This is made available to the community as part of
the PINGSoft IFS software package.Comment: Accepted for publication in Astronomy & Astrophysics, 12 pages, 7
figure
Integral Field Spectroscopy based H\alpha\ sizes of local Luminous and Ultraluminous Infrared Galaxies. A Direct Comparison with high-z Massive Star Forming Galaxies
Aims. We study the analogy between local U/LIRGs and high-z massive SFGs by
comparing basic H{\alpha} structural characteristics, such as size, and
luminosity (and SFR) surface density, in an homogeneous way (i.e. same tracer
and size definition, similar physical scales). Methods. We use Integral Field
Spectroscopy based H{\alpha} emission maps for a representative sample of 54
local U/LIRGs (66 galaxies). From this initial sample we select 26 objects with
H{\alpha} luminosities (L(H{\alpha})) similar to those of massive (i.e. M\ast
\sim 10^10 M\odot or larger) SFGs at z \sim 2, and observed on similar physical
scales. Results. The sizes of the H{\alpha} emitting region in the sample of
local U/LIRGs span a large range, with r1/2(H{\alpha}) from 0.2 to 7 kpc.
However, about 2/3 of local U/LIRGs with Lir > 10^11.4 L\odot have compact
H{\alpha} emission (i.e. r1/2 < 2 kpc). The comparison sample of local U/LIRGs
also shows a higher fraction (59%) of objects with compact H{\alpha} emission
than the high-z sample (25%). This gives further support to the idea that for
this luminosity range the size of the star forming region is a distinctive
factor between local and distant galaxies of similar SF rates. However, when
using H{\alpha} as a tracer for both local and high-z samples, the differences
are smaller than the ones recently reported using a variety of other tracers.
Despite of the higher fraction of galaxies with compact H{\alpha} emission, a
sizable group (\sim 1/3) of local U/LIRGs are large (i.e. r1/2 > 2 kpc). These
are systems showing pre-coalescence merger activity and they are
indistinguishable from the massive high-z SFGs galaxies in terms of their
H{\alpha} sizes, and luminosity and SFR surface densities.Comment: Accepted for publication in A&A. (!5 pages, 7 figures, 2 tables
Two-Dimensional Line Strength Maps in Three Well-studied Early-Type Galaxies
Integral field spectroscopy has been obtained for the nuclear regions of 3
large, well-studied, early-type galaxies. From these spectra we have obtained
line strength maps for about 20 absorption lines, mostly belonging to the Lick
system. An extensive comparison with multi-lenslet spectroscopy shows that
accurate kinematic maps can be obtained, and also reproducible line strength
maps. Comparison with long-slit spectroscopy also produces good agreement. We
show that Mg is enhanced with respect to Fe in the inner disk of one of the
three galaxies studied, the Sombrero. [Mg/Fe] there is larger than in the rest
of the bulge. The large values of Mg/Fe in the central disk are consistent with
the centres of other early-type galaxies, and not with large disks, like the
disk of our Galaxy, where [Mg/Fe] is approximately 0. We confirm with this
observation a recent result of Worthey (1998) that Mg/Fe is determined by the
central kinetic energy, or escape velocity, of the stars, only, and not by the
formation time scale of the stars. A stellar population analysis using the
models of Vazdekis et al. (1996) shows that our observed H gamma agrees well
with what is predicted based on the other lines. Using the line strength of the
Ca II IR triplet as an indicator of the abundance of Ca, we find that Ca
follows Fe, and not Mg, in these galaxies. This is peculiar, given the fact
that Ca is an alpha-element. Finally, by combining the results of this paper
with those of Vazdekis et al. (1997) we find that the line strength gradients
in the three galaxies are primarily caused by variations in metallicity.Comment: 23 pages, Latex, includes mn.sty, accepted for publication in Monthly
Notices of the Royal Astronomical Societ
A reproducible notebook to acquire, process and analyse satellite imagery
Satellite imagery is often used to study and monitor Earth surface changes. The open availability and extensive temporal coverage of Landsat imagery has enabled changes in temperature, wind, vegetation and ice melting speed for a period of up to 46 years. Yet, the use of satellite imagery to study cities has remained underutilised, partly due to the lack of a methodological approach to capture features and changes in the urban environment. This notebook offers a framework based on Python tools to demonstrate how to batch-download high-resolution satellite imagery; and enable the extraction, analysis and visualisation of features of the built environment to capture long-term urban changes
Recurrence of the blue wing enhancements in the high ionization lines of SDSS 1004+4112 A
We present integral field spectroscopic observations of the quadruple-lensed
QSO SDSS 1004+4112 taken with the fiber system INTEGRAL at the William Herschel
Telescope on 2004 January 19. In May 2003 a blueward enhancement in the high
ionization lines of SDSS 1004+4112A was detected and then faded. Our
observations are the first to note a second event of similar characteristics
less than one year after. Although initially attributed to microlensing, the
resemblance among the spectra of both events and the absence of
microlensing-induced changes in the continuum of component A are puzzling. The
lack of a convincing explanation under the microlensing or intrinsic
variability hypotheses makes the observed enhancements particularly relevant,
calling for close monitoring of this object.Comment: 4 pages, 5 figure
Defying some difficulties of the assessment of several generic competences
A reference to concepts, procedures and attitudes and also to acquisition of capacities was frequent when people were interchanging opinions about the aspects that could be evaluated in a university-level student.
Now, we speak in terms of competences: there are specific competences, generic competences,. Just trying to speak about them is a hard job; to obtain competences will represent an enormous challenge. Itâs
important to mention the extensive difficulty to find a common definition of the word "competence". One of the many meanings is: the knowledge needed to do something, the knowledge needed to do something with people, the knowledge needed to do something with criteria, the knowledge of when and why is necessary to do something. Common elements to the numerous definitions are the references to: a set of
conceptual knowledge, the procedures and the attitudes, feasibility in its learning with recurrent training, an explanation on its attainment in the action, its use in an efficient work and a necessary context.
Some of the reasons used for the work by the competences in the educative sphere are the overcoming of the design based on content, the integration of diverse intelligences, the advance towards a unification of the areas of the knowledge, the true connection with a final applicability of the education in the work. A formation in competences demands several experiences that integrate knowledge and the practical design to apply these experiences â including several (and/or many) of them -, selecting and preparing the diverse scenes that promote them. One of the objectives of the hands-on session is to explain and to discuss about this kind of experiences, practical designs and stages.
Even with all their limitations, the conventional tools have been useful for an evaluation of the degree of assimilation of the concepts and the capacities; nevertheless, the task is much more arduous -and with less explicit experience transmissible and transmitted - when a person moves in the reach of the evaluation in values and attitudes, and of the evaluation of the competitions located within a profile. In order to evaluate competences, the educational team defines evidences. This task must be done in team
for many reasons. For example, the fact that many competences transfer the borders of the concrete territory in which an individual professor moves. The mentioned evidences will have to be pertinent, excellent, adapted and realistic.
Often, to elaborate a scheme of the knowledge associated to each competence will identify diverse possibilities to demonstrate the possession of this competence through its development in a practical frame. Nevertheless, some competences (or some groups of competences) can be resisted to the previous practice. Perhaps it would be possible to lodge here the ethical behaviour, the capacity to learn, the responsibility, the team work, the creative and enterprising capacity, the multiple attention to sustainability and the subjects around the communicative capacity. Also the evidences for this sort of
competences are targeted issues in the debates.
Within the previous frame, the authors of this contribution have made tasks destined to the specification of several elements, in the work of the "CAU-AIDA" group of the professors of several universities, within the project #SEJ2007-65786 âEvaluation of competences of the university students in the face of the challenge of the EEES: description of the current scenario, analysis of good practices and proposals of
transfer to different environmentsâ and can offer some results of their task that shows there are options to approach some assessments about many generic competences. The planned procedure is to expose briefly
some experiences and the referred evidences, devoted to the assessment that can be transferred, concerning each of the above mentioned generic competences.Peer Reviewe
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