The analysis and combination of data from different gamma-ray instruments involves the use of collaboration proprietary software and case-by-case methods. The effort of defining a common data format ...for high-level data, namely event lists and instrument response functions (IRFs), has recently started for very-high-energy gamma-ray instruments, driven by the upcoming Cherenkov Telescope Array (CTA). In this work we implemented this prototypical data format for a small set of MAGIC, VERITAS, FACT, and H.E.S.S. Crab nebula observations, and we analyzed them with the open-source gammapy software package. By combining data from Fermi-LAT, and from four of the currently operating imaging atmospheric Cherenkov telescopes, we produced a joint maximum likelihood fit of the Crab nebula spectrum. Aspects of the statistical errors and the evaluation of systematic uncertainty are also commented upon, along with the release format of spectral measurements. The results presented in this work are obtained using open-access on-line assets that allow for a long-term reproducibility of the results.
H-Distributions via Sobolev Spaces Aleksić, J.; Pilipović, S.; Vojnović, I.
Mediterranean journal of mathematics,
10/2016, Volume:
13, Issue:
5
Journal Article
Peer reviewed
H-distributions associated with weakly convergent sequences in Sobolev spaces are determined. It is shown that a weakly convergent sequence
(
u
n
)
in
W
-
k
,
p
(
R
d
)
has the property that
θ
u
n
...converges strongly in
W
-
k
,
p
(
R
d
)
for every
θ
∈
S
(
R
d
)
if and only if all H-distributions related to this sequence are equal to zero. Results are applied on a weakly convergent sequence of solutions to a family of linear first-order PDEs.
The Gaia DR2 reference frame should be without relative rotation to the quasars (QSOs) and consistent with the International Celestial Reference System (ICRS). For the faint part of DR2 (stars with ...Gaia magnitude G ? 16) that task was done via Gaia's observations of QSOs (G ? 17 mag), but the bright DR2 (G ? 13 mag) is difficult to validate and it rotates relative to the faint DR2 at rate of the order of 0.1 mas/yr. Very bright DR2 stars (G ? 6 mag) mostly have inferior astrometry. Here, the aim is to determine two spin components (?X and ?Y ) of the bright DR2 using International Latitude Service (ILS, for 387 stars) and independent latitude stations (INDLS, for 682 stars) catalogs of proper motion in declination ??; both are referred to the Hipparcos reference frame and their stars are mostly from 4 to 8 mag in the V-band (critical part of DR2). Also, using the new Hipparcos (NHIP) values ?? for ILS and INDLS stars, we can see that the merit of the ILS and INDLS is the long time baseline (?t ? 90 years) important for ?? because the standard deviation of ?? is opposite to ?t. Applying the least squares method (LSM) to the differences of ?? between two catalogs (ILS-DR2, INDLS-DR2, etc.), our results support the mentioned spin. The 3? criterion and Tukey's fences method were used to reject some stars, the Abbe criterion to explain the variability in ILS-DR2 and other ?? differences, and the Shapiro-Wilk test to check the standard distribution of differences. The obtained ?? is significant at the 2? level, and the ILS and INDLS catalogs could be useful for validation of the bright reference frame of Gaia DR2.
Discovering the nature of Dark Matter (DM) is one of the fundamental challenges of the modern physics. Indirect searches of DM are devoted to look for non-gravitational signals of its presence in the ...highly DM dominated cosmic regions. Within the weakly interacting massive particles (WIMPs) scenario, we expect very high energy (VHE) gamma-ray emissions resulting from annihilation and/or decay of DM particles. Since the beginning of operations, the Major Atmospheric Gamma Imaging Cherenkov (MAGIC) telescopes are carrying out deep observations of several promising DM targets, with the aim of detecting such signals or alternatively setting stringent constrains to DM particle models in the TeV mass region. In this contribution we present the latest indirect DM search results achieved by MAGIC on several targets, such as dwarf satellites - where MAGIC reached the strongest constraints on DM annihilation searches above few hundreds of GeV -, galaxy clusters, and the Galactic Center.
Accurate statistical measurement with large imaging surveys has traditionally required throwing away a sizable fraction of the data. This is because most measurements have relied on selecting nearly ...complete samples, where variations in the composition of the galaxy population with seeing, depth, or other survey characteristics are small. We introduce a new measurement method that aims to minimize this wastage, allowing precision measurement for any class of detectable stars or galaxies. We have implemented our proposal in balrog, software which embeds fake objects in real imaging to accurately characterize measurement biases. We demonstrate this technique with an angular clustering measurement using Dark Energy Survey (DES) data. We first show that recovery of our injected galaxies depends on a variety of survey characteristics in the same way as the real data. We then construct a flux-limited sample of the faintest galaxies in DES, chosen specifically for their sensitivity to depth and seeing variations. Using the synthetic galaxies as randoms in the Landy–Szalay estimator suppresses the effects of variable survey selection by at least two orders of magnitude. With this correction, our measured angular clustering is found to be in excellent agreement with that of a matched sample from much deeper, higher resolution space-based Cosmological Evolution Survey (COSMOS) imaging; over angular scales of 0
$_{.}^{\circ}$
004 < θ < 0
$_{.}^{\circ}$
2, we find a best-fitting scaling amplitude between the DES and COSMOS measurements of 1.00 ± 0.09. We expect this methodology to be broadly useful for extending measurements’ statistical reach in a variety of upcoming imaging surveys.
The last resort for conservation of rare tree populations in refugial areas under high risk of climate driven extinction may be ex situ conservation and assisted translocation. Although such actions ...require detailed knowledge about the spatial scale and heterogeneity of the within-population distribution of genetic diversity, it is still unknown whether fine-scale spatial genetic structure (FSGS) is present in refugial populations of forest trees. In order to address this issue, we carried out the first whole-population genetic characterisation of a small and isolated refugial population of the IUCN red-listed Serbian spruce
Picea omorika
(Panč.) Purk. from the Balkans. All 418 adult individuals were georeferenced and genotyped at nuclear EST-SSRs and at a mitochondrial (mtDNA) locus. Spatial autocorrelation analyses provided only a simplified description of FSGS, which is concordant with findings in wind-pollinated species with limited seed dispersal. However, Bayesian analysis revealed three heterogeneous, highly differentiated (pairwise
G’
ST
> 0.3), and spatially localised sub-populations showing only partial overlap with the distribution of mtDNA haplotypes. Such complex structure in only 0.34 ha, resulting mainly from historical events, restrictions to gene flow and high local density, was undetected in previous work based on more traditional sampling schemes for population genetics surveys. We demonstrate the usefulness of sampling schemes leaning towards a whole-population genetic characterisation in mining the finest characteristics of FSGS, and argue that our understanding of genetic structuring in highly heterogeneous refugial regions at both macro- and micro-scales is still rather limited and often oversimplified. This has severe implications on conservation of plant biodiversity from these regions in terms of responses to global climate change.
Shear peak statistics has gained a lot of attention recently as a practical alternative to the two-point statistics for constraining cosmological parameters. We perform a shear peak statistics ...analysis of the Dark Energy Survey (DES) Science Verification (SV) data, using weak gravitational lensing measurements from a 139 deg super( 2) field. We measure the abundance of peaks identified in aperture mass maps, as a function of their signal-to-noise ratio, in the signal-to-noise range ... To predict the peak counts as a function of cosmological parameters, we use a suite of N-body simulations spanning 158 models with varying ... and ..., fixing ..., to which we have applied the DES SV mask and redshift distribution. In our fiducial analysis we measure ..., after marginalizing over the shear multiplicative bias and the error on the mean redshift of the galaxy sample. We introduce models of intrinsic alignments, blending and source contamination by cluster members. These models indicate that peaks with ... would require significant corrections, which is why we do not include them in our analysis. We compare our results to the cosmological constraints from the two-point analysis on the SV field and find them to be in good agreement in both the central value and its uncertainty. We discuss prospects for future peak statistics analysis with upcoming DES data. (ProQuest: ... denotes formulae/symbols omitted.)
Supermassive black holes with masses of millions to billions of solar masses are commonly found in the centers of galaxies. Astronomers seek to image jet formation using radio interferometry but ...still suffer from insufficient angular resolution. An alternative method to resolve small structures is to measure the time variability of their emission. Here we report on gamma-ray observations of the radio galaxy IC 310 obtained with the MAGIC (Major Atmospheric Gamma-ray Imaging Cherenkov) telescopes, revealing variability with doubling time scales faster than 4.8 min. Causality constrains the size of the emission region to be smaller than 20% of the gravitational radius of its central black hole. We suggest that the emission is associated with pulsar-like particle acceleration by the electric field across a magnetospheric gap at the base of the radio jet.
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