Andes Large-area PArticle detector for Cosmic-ray physics and Astronomy (ALPACA) is an international experiment that applies southern very-high-energy (VHE) gamma-ray astronomy to determine the ...origin of cosmic rays around the knee energy region (10
15
eV − 10
16
eV). The experiment consists of an air shower (AS) array with a surface of 83,000m
2
and an underground water Cherenkov muon detector (MD) array covering 5,400m
2
. The experimental site is at the Mt. Chacaltaya plateau in La Paz, Bolivia, with an altitude of 4,740m corresponding to 572g/cm
2
atmospheric thickness. As the prototype experiment of ALPACA, the ALPAQUITA experiment aims to begin data acquisition in late 2021. The ALPAQUITA array consists of a smaller AS array (18,450m
2
) and underground MD (900m
2
), which are now under construction. ALPAQUITA’s sensitivity to gamma-ray sources is evaluated with Monte Carlo simulations. The simulation finds that five gamma-ray sources observed by H.E.S.S. and HAWC experiments will be detected by ALPAQUITA beyond 10TeV and ne out of these five - HESS J1702-420A - above 300 TeV in one calendar year observation. The latter finding means that scientific discussions can be made on the emission mechanism of gamma rays beyond 100TeV from southern sources on the basis of the observational results of this prototype experiment.
Observation techniques of high-energy gamma rays using air showers have remarkably progressed via the Tibet AS
γ
, HAWC, and LHAASO experiments. These observations have significantly contributed to ...gamma-ray astronomy in the northern sky’s sub-PeV region. Moreover, in the southern sky, the ALPACA experiment is underway at 4,740 m altitude on the Chacaltaya plateau in Bolivia. This experiment estimates the gamma-ray flux from the difference between the number of on-source and off-source events by real data, utilizing the gamma-ray detection efficiency calculated through Monte Carlo simulations, which in turn depends on the hadronic interaction models. Even though the number of cosmic-ray background events can be experimentally estimated, this model dependence affects the estimation of gamma-ray detection efficiency. However, previous reports have assumed that the model dependence is negligible and have not included it in the error of gamma-ray flux estimation. Using ALPAQUITA, the prototype experiment of ALPACA, we quantitatively evaluated the model dependence on hadronic interaction models for the first time. We evaluate the model dependence on hadronic interactions as less than 3.6 % in the typical gamma-ray flux estimation performed by ALPAQUITA; this is negligible compared with other uncertainties such as energy scale uncertainty in the energy range from 6 to 300 TeV, which is dominated by the Monte Carlo statistics. This upper limit of 3.6 % model dependence is expected to apply to ALPACA.
HESS J1843$-$033 is a very-high-energy gamma-ray source whose origin remains
unidentified. This work presents, for the first time, the energy spectrum of
gamma rays beyond $100\, {\rm TeV}$ from the ...HESS J1843$-$033 region using the
data recorded by the Tibet air shower array and its underground muon detector
array. A gamma-ray source with an extension of $0.34^{\circ} \pm 0.12^{\circ}$
is successfully detected above $25\, {\rm TeV}$ at $(\alpha,\, \delta) =
(281.09^{\circ}\pm 0.10^{\circ},\, -3.76^{\circ}\pm 0.09^{\circ})$ near HESS
J1843$-$033 with a statistical significance of $6.2\, \sigma$, and the source
is named TASG J1844$-$038. The position of TASG J1844$-$038 is consistent with
those of HESS J1843$-$033, eHWC J1842$-$035, and LHAASO J1843$-$0338. The
measured gamma-ray energy spectrum in $25\, {\rm TeV} < E < 130\, {\rm TeV}$ is
described with ${\rm d}N/{\rm d}E = (9.70\pm 1.89)\times 10^{-16} (E/40\, {\rm
TeV})^{-3.26\pm 0.30}\, {\rm TeV}^{-1} {\rm cm}^{-2} {\rm s}^{-1}$, and the
spectral fit to the combined spectra of HESS J1843$-$033, LHAASO J1843$-$0338,
and TASG J1844$-$038 implies the existence of a cutoff at $49.5\pm 9.0\, {\rm
TeV}$. Associations of TASG J1844-038 with SNR G28.6$-$0.1 and PSR J1844-0346
are also discussed in detail for the first time.
Gamma rays from HESS J1849\(-\)000, a middle-aged TeV pulsar wind nebula (PWN), are observed by the Tibet air shower array and the muon detector array. The detection significance of gamma rays ...reaches \(4.0\, \sigma\) and \(4.4\, \sigma\) levels above 25 TeV and 100 TeV, respectively, in units of Gaussian standard deviation \(\sigma\). The energy spectrum measured between \(40\, {\rm TeV} < E < 320\, {\rm TeV}\) for the first time is described with a simple power-law function of \({\rm d}N/{\rm d}E = (2.86 \pm 1.44) \times 10^{-16}(E/40\, {\rm TeV})^{-2.24 \pm 0.41}\, {\rm TeV}^{-1}\, {\rm cm}^{-2}\, {\rm s}^{-1}\). The gamma-ray energy spectrum from the sub-TeV (\(E < 1\, {\rm TeV}\)) to sub-PeV (\(100\, {\rm TeV} < E < 1\, {\rm PeV}\)) ranges including the results of previous studies can be modeled with the leptonic scenario, inverse Compton scattering by high-energy electrons accelerated by the PWN of PSR J1849\(-\)0001. On the other hand, the gamma-ray energy spectrum can also be modeled with the hadronic scenario in which gamma rays are generated from the decay of neutral pions produced by collisions between accelerated cosmic-ray protons and the ambient molecular cloud found in the gamma-ray emitting region. The cutoff energy of cosmic-ray protons \(E_{\rm p\, cut}\), cut is estimated at \({\rm log}_{10}(E_{\rm p,\, cut}/{\rm TeV}) = 3.73^{+2.98}_{-0.66}\), suggesting that protons are accelerated up to the PeV energy range. Our study thus proposes that HESS J1849\(-\)000 should be further investigated as a new candidate for a Galactic PeV cosmic-ray accelerator, PeVatron.
Andes Large-area PArticle detector for Cosmic-ray physics and Astronomy (ALPACA) is an international experiment that applies southern very-high-energy (VHE) gamma-ray astronomy to determine the ...origin of cosmic rays around the knee energy region (\(10^{15}\, {\rm eV} - 10^{16}\, {\rm eV}\)). The experiment consists of an air shower (AS) array with a surface of \(83, 000\, {\rm m}^2\) and an underground water Cherenkov muon detector (MD) array covering \(5, 400\, {\rm m}^2\). The experimental site is at the Mt. Chacaltaya plateau in La Paz, Bolivia, with an altitude of \(4, 740\, {\rm m}\) corresponding to \(572\, {\rm g}/{\rm cm}^2\) atmospheric thickness. As the prototype experiment of ALPACA, the ALPAQUITA experiment aims to begin data acquisition in late 2021. The ALPAQUITA array consists of a smaller AS array (\(18, 450\, {\rm m}^2\)) and underground MD (\(900\, {\rm m}^2\)), which are now under construction. ALPAQUITA's sensitivity to gamma-ray sources is evaluated with Monte Carlo simulations. The simulation finds that five gamma-ray sources observed by H.E.S.S. and HAWC experiments will be detected by ALPAQUITA beyond 10 TeV and one out of these five - HESS J1702-420A - above 300 TeV in one calendar year observation. The latter finding means that scientific discussions can be made on the emission mechanism of gamma rays beyond 100 TeV from southern sources on the basis of the observational results of this prototype experiment.
We report observations of gamma-ray emissions with energies in the 100 TeV energy region from the Cygnus region in our Galaxy. Two sources are significantly detected in the directions of the Cygnus ...OB1 and OB2 associations. Based on their positional coincidences, we associate one with a pulsar PSR J2032+4127 and the other mainly with a pulsar wind nebula PWN G75.2+0.1 with the pulsar moving away from its original birthplace situated around the centroid of the observed gamma-ray emission. This work would stimulate further studies of particle acceleration mechanisms at these gamma-ray sources.
1,2-Alkanediol exhibits antibacterial activity against several bacteria and yeast. However, few studies have reported antimicrobial tests on skin microbiome. Bacterial microbiome on the skin surface ...include Staphylococcus aureus (S. aureus), which causes rough skin and inflammation in atopic dermatitis and Staphylococcus epidermidis (S. epidermidis), which enhances innate immunity. In this study, the minimal inhibitory concentration (MIC) was evaluated for 1,2-alkanediol comprising 4–12 carbon atoms against S. aureus and S. epidermidis. 1,2-Alkanediol comprising 6–12 carbon atoms exhibited antimicrobial activity against both species of Staphylococcus. The antibacterial activity depended on the alkyl chain length. In addition, the minimum bactericidal concentration (MBC) on agar was evaluated for 1,2-alkanediol comprising 6–12 carbon atoms. 1,2-Octanediol and 1,2-decanediol exhibited significant bactericidal activity.
Fatty acids and their derivatives are interesting cosmetic ingredients because they show the selective antibacterial activity against Staphylococcus aureus (S. aureus). However, the antibacterial ...activity in mixed systems containing several active ingredients is unclear because previous studies focused antibacterial systems containing one kind of fatty acid. In the present study, the minimal inhibitory concentration (MIC) and the fractional inhibitory concentration (FIC) were evaluated for myristic acid/lauric acid, myristic acid/palmitoleic acid, and myristic acid/lactic acid mixed systems to show the effect of the coexisting components on the selective antibacterial activity of myristic acid. In the myristic acid/palmitoleic acid mixed system, the antibacterial activity against S. aureus was enhanced by additive effect, whereas the antibacterial activity was not observed against S. epidermidis. On the other hand, the myristic acid/lauric acid mixed system showed antibacterial activity against S. epidermidis: Lauric acid impaired the selectivity of antibacterial activity of myristic acid. These results suggest that the selective activity of myristic acid varies with the additives. The present findings are useful for designing formulations of cosmetics and body cleansers containing myristic acid.
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