arXiv subjects

Moritz Hütten

Publications and source records attributed to Moritz Hütten.

17 recordsLinked to original sources

arXiv2026

High-Resolution Mapping of Port Dynamics from Open-Access AIS Data in Tokyo Bay

Knowledge about vessel activity in port areas and around major industrial zones provides insights into economic trends, supports decision-making for shipping and port operators, and contributes to maritime safety. Vessel data from terrestrial receivers of the Automatic Identification System (AIS) have become increasingly openly available, and we demonstrate that such data can be used to infer port activities at high resolution and with precision comparable to official statistics. We analyze open-access AIS data from a three-month period in 2024 for Tokyo Bay, located in Japan's most densely populated urban region. Accounting for uneven data coverage, we reconstruct vessel activity in Tokyo Bay at $\sim\,$30~m resolution and identify 161 active berths across seven major port areas in the bay. During the analysis period, we find an average of $35\pm17_{\text{stat}}$ vessels moving within the bay at any given time, and $293\pm22_{\text{stat}}+65_{\text{syst}}-10_{\text{syst}}$ vessels entering or leaving the bay daily, with an average gross tonnage of $11{,}860^{+280}_{-\;\,50}$. These figures indicate an accelerating long-term trend toward fewer but larger vessels in Tokyo Bay's commercial traffic. Furthermore, we find that in dense urban environments, radio shadows in vessel AIS data can reveal the precise locations of inherently passive receiver stations.

cs.CE↗

arXiv2025

Maritime Activities Observed Through Open-Access Positioning Data: Moving and Stationary Vessels in the Baltic Sea

Understanding past and present maritime activity patterns is critical for navigation safety, environmental assessment, and commercial operations. An increasing number of services now openly provide positioning data from the Automatic Identification System (AIS) via ground-based receivers. We show that coastal vessel activity can be reconstructed from open access data with high accuracy, even with limited data quality and incomplete receiver coverage. For three months of open AIS data in the Baltic Sea from August to October 2024, we present (i) cleansing and reconstruction methods to improve the data quality, and (ii) a journey model that converts AIS message data into vessel counts, traffic estimates, and spatially resolved vessel density at a resolution of $\sim$400 m. Vessel counts are provided, along with their uncertainties, for both moving and stationary activity. Vessel density maps also enable the identification of port locations, and we infer the most crowded and busiest coastal areas in the Baltic Sea. We find that on average, $\gtrsim$4000 vessels simultaneously operate in the Baltic Sea, and more than 300 vessels enter or leave the area each day. Our results agree within 20\% with previous studies relying on proprietary data.

cs.CE↗

arXiv2025

Detecting dark matter sub-halos in the Galactic plane with the Cherenkov Telescope Array Observatory

Numerous observations confirm the existence of dark matter (DM) at astrophysical and cosmological scales. Theory and simulations of galaxy formation predict that DM should cluster on small scales in bound structures called sub-halos or DM clumps. While the most massive DM sub-halos host baryonic matter, less massive, unpopulated sub-halos could be abundant in the Milky Way (MW), as well and yield high-energy gamma rays as final products of DM annihilation. Recently, it has been highlighted that the brightest halos should also have a sizeable extension in the sky. In this study, we examine the prospects offered by the Cherenkov Telescope Array Observatory (CTAO), a next-generation gamma-ray instrument, for detecting and characterizing such objects. Previous studies have primarily focused on high-latitude observations; here, we assess the potential impact of the CTAO's Galactic Plane Survey, which will provide unprecedentedly deep survey data for the inner five degrees of the Galactic plane. Our modeling accounts for tidal effects on the sub-halo population, examining the conditions under which DM sub-halos can be detected and distinguished from conventional astrophysical sources. We find that regions a few degrees above or below the Galactic plane offer the highest likelihood for DM sub-halo detection. For an individual sub-halo -- the brightest from among various realizations of the MW subhalo population -- we find that detection at the 5$σ$ level is achievable for an annihilation cross section of $\langle σv \rangle \sim 3\times10^{-25}$ cm$^3$/s for TeV-scale DM annihilating into $b\bar{b}$. For a full population study, depending on the distribution and luminosity model of Galactic sub-halos, yet unconstrained cross sections in the range $\langle σv \rangle \sim 10^{-23}-10^{-22}$ cm$^3$/s for TeV DM candidates are necessary for the brightest sub-halos to be detected.

astro-ph.HE↗

arXiv2024

Dark Matter and Fundamental Physics Searches with IACTs

Cosmic gamma rays are a valid probe to search for fundamental physics. Some of these exotic and exciting scenarios are the subject of this contribution to the book. All current Imaging Atmospheric Cherenkov Telescopes (IACTs) have invested a great deal of time and resources in scouting these out. In this chapter, we focus on the case of indirect search for weakly interacting massive particles (Sec. 8.1) and that of search for axion-like particles (Sec. 8.2). We continue with less debated, yet interesting studies on the search for primordial black holes (Sec. 8.3), tau-neutrinos (8.4), and magnetic monopoles (8.5). Other scenarios of fundamental physics like the search for Lorentz Invariance violations are treated elsewhere in the book. We structured the contribution providing a self-contained (yet minimal) theoretical framework, as well as a complete report of all IACTs' published contribution to the topics under consideration (updated until 2022). Our aim is to provide a reference review as well as take a photograph of the effort of the current generation of IACTs and the challenges taken, in preparation of the next-generation instrument to come, the Cherenkov Telescope Array.

astro-ph.HE↗

arXiv2022

TeV Dark Matter Searches in the Extragalactic Gamma-Ray Sky

High-energetic gamma rays from astrophysical targets constitute a unique probe for annihilation or decay of heavy particle dark matter (DM). After several decades, diverse null detections have resulted in strong constraints for DM particle masses up to the TeV scale. While the gamma-ray signature is expected to be universal from various targets, uncertainties of astrophysical origin strongly affect and weaken the limits. At the same time, spurious signals may originate from non-DM related processes. The many gamma-ray targets in the extragalactic sky being searched for DM play a crucial role to keep these uncertainties under control and to ultimately achieve an unambiguous DM detection. Lately, a large progress has been made in combined analyses of TeV DM candidates towards different targets by using data from various instruments and over a wide range of gamma-ray energies. These approaches not only resulted in an optimal exploitation of existing data and an improved sensitivity, but also helped to level out target- and instrument-related uncertainties. This review gathers all searches in the extragalactic sky performed so far with the space-borne Fermi-Large Area Telescope, the ground-based imaging atmospheric Cherenkov telescopes, and the High-Altitude Water Cherenkov Gamma-Ray Observatory (HAWC). We discuss the different target classes and provide a complete list of all analyses so far.

astro-ph.HE↗

arXiv2019

Gamma-ray sensitivity to dark matter subhalo modelling at high latitudes

Searches for "dark" subhaloes in gamma-ray point-like source catalogues are among promising strategies for indirect dark matter detection. Such a search is nevertheless affected by uncertainties related, on the one hand, to the modelling of the dark matter subhalo distribution in Milky-Way-like galaxies, and, on the other hand, to the sensitivity of gamma-ray instruments to the dark matter subhalo signals. In the present work, we assess the detectability of dark matter subhaloes in Fermi-LAT catalogues, taking into accounts uncertainties associated with the modelling of the Galactic subhalo population. We use four different halo models bracketing a large set of uncertainties. For each model, adopting an accurate detection threshold of the LAT to dark matter subhalo signals and comparing model predictions with the number of unassociated point-sources in Fermi-LAT catalogues, we derive upper limits on the annihilation cross section as a function of dark matter mass. Our results show that, even in the best-case scenario (i.e. DMonly subhalo model), which does not include tidal disruption from baryons, the limits on the dark matter parameter space are less stringent than current gamma-ray limits from dwarf spheroidal galaxies. Comparing the results obtained with the different subhalo models, we find that baryonic effects on the subhalo population are significant and lead to dark matter constraints that are less stringent by a factor of about 2 to 5. This uncertainty comes from the unknown resilience of dark matter subhaloes to tidal disruption.

astro-ph.HE↗

arXiv2019

Search for Dark Matter decay signals in the Galactic Halo with the MAGIC telescopes

MAGIC is a system of two Cherenkov telescopes located in the Canary island of La Palma. A key part of MAGIC Fundamental Physics program is the search for indirect signals of Dark Matter (DM) from different sources. In the Milky Way, DM forms an almost spherically symmetric halo, with a density peaked towards the center of the Galaxy and decreasing toward the outer region. We search for DM decay signals from the Galactic Halo, with a special methodology developed for this work. Our strategy is to compare pairs of observations performed at different angular distances from the Galactic Center, selected in such a way that all the diffuse components cancel out, except for those coming from the DM. In order to keep the systematic uncertainty of this novel background estimation method down to a minimum, the observation pairs have been acquired during the same nights and follow exactly the same azimuth and zenith paths. We collected 20 hours of data during 2018. Using half of them to determine the systematic uncertainty in the background estimation of our analysis, we obtain a value of 4.8\% with no dependence on energy. Accounting for this systematic uncertainty in the likelihood analysis based on the 10 remaining hours of data collected so far, we present the limit to TeV DM particle with a lifetime of $10^{26}$ s in the $\mathrm{b\bar{b}}$ decay channel.

astro-ph.HE↗

arXiv2019

$γ$-ray and $ν$ searches for dark matter subhalos in the Milky Way with a baryonic potential

The distribution of dark matter (DM) subhalos in our Galaxy remains disputed, leading to varying $γ$-ray and $ν$ flux predictions from their annihilation or decay. In this work, we study how, in the inner Galaxy, subhalo tidal disruption from the Galactic baryonic potential impacts these signals. Based on state-of-the art modeling of this effect from numerical simulations and semi-analytical results, updated subhalo spatial distributions are derived and included in the CLUMPY code. The latter is used to produce a thousand realizations of the $γ$-ray and $ν$ sky. Compared to predictions based on DM only, we conclude a decrease of the flux of the brightest subhalo by a factor 2 to 7 for annihilating DM and no impact on decaying DM: the discovery prospects or limits subhalos can set on DM candidates are affected by the same factor. This study also provides probability density functions for the distance, mass, and angular distribution of the brightest subhalo, among which the mass may hint at its nature: it is most likely a dwarf spheroidal galaxy in the case of strong tidal effects from the baryonic potential, whereas it is lighter and possibly a dark halo for DM only or less pronounced tidal effects.

astro-ph.HE↗

arXiv2018

CLUMPY v3: $γ$-ray and $ν$ signals from dark matter at all scales

We present the third release of the CLUMPY code for calculating $γ$-ray and $ν$ signals from annihilations or decays in dark matter structures. This version includes the mean extragalactic signal with several pre-defined options and keywords related to cosmological parameters, mass functions for the dark matter structures, and $γ$-ray absorption up to high redshift. For more flexibility and consistency, dark matter halo masses and concentrations are now defined with respect to a user-defined overdensity $Δ$. We have also made changes for the user's benefit: distribution and versioning of the code via \git{}, less dependencies and a simplified installation, better handling of options in run command lines, consistent naming of parameters, and a new Sphinx documentation at http://lpsc.in2p3.fr/clumpy/.

astro-ph.CO↗

arXiv2018

Observing small-scale $γ$-ray anisotropies with the Cherenkov Telescope Array

Disentangling the composition of the diffuse gamma-ray background (DGRB) is a major challenge in gamma-ray astronomy. It is presumed that at the highest energies, the DGRB is dominated by relatively few, still unresolved point sources. This conjecture has recently been supported by the measurement of small-scale anisotropies in the DGRB by the Fermi Large Area Telescope (LAT) up to energies of 500 GeV. We show how such anisotropies can be searched for with the forthcoming Earth-bound Cherenkov Telescope Array (CTA) up to the TeV range. We investigate different observation modes to analyse CTA data for small-scale anisotropies and propose the projected extragalactic large-area sky survey as the most promising data set. Relying on an up-to-date model of the performance of the southern CTA, we find that CTA will be able to probe anisotropies in the DGRB from unresolved point sources at a relative amplitude of $C_{\rm P}^I/I^2_{\rm DGRB}\gtrsim 4\times 10^{-3}\,{\rm sr}$ at energies above 30 GeV and angular scales $\lesssim 1.5^{\circ}$. Such DGRB anisotropies have not yet been ruled out by the Fermi-LAT. The proposed analysis would primarily clarify the contribution from blazars and misaligned active galactic nuclei to the very-high-energy regime of the DGRB, as well as provide insight into dark matter annihilation in Galactic and extragalactic density structures. Finally, it constitutes a measurement with complementary systematic uncertainties compared to the Fermi-LAT.

astro-ph.HE↗

arXiv2018

Extragalactic diffuse gamma-rays from dark matter annihilation: revised prediction and full modelling uncertainties

Recent high-energy data from Fermi-LAT on the diffuse gamma-ray background have been used to set among the best constraints on annihilating TeV cold dark matter candidates. In order to assess the robustness of these limits, we revisit and update the calculation of the isotropic extragalactic gamma-ray intensity from dark matter annihilation. The emission from halos with masses $\geq10^{10}\,M_{\odot}$ provides a robust lower bound on the predicted intensity. The intensity including smaller halos whose properties are extrapolated from their higher mass counterparts is typically 5 times higher, and boost from subhalos yields an additional factor ~1.5. We also rank the uncertainties from all ingredients and provide a detailed error budget for them. Overall, our fiducial intensity is a factor 5 lower than the one derived by the Fermi-LAT collaboration in their latest analysis. This indicates that the limits set on extragalactic dark matter annihilations could be relaxed by the same factor. We also calculate the expected intensity for self-interacting dark matter in massive halos and find the emission reduced by a factor 3 compared to the collisionless counterpart. The next release of the CLUMPY code will provide all the tools necessary to reproduce and ease future improvements of this prediction.

astro-ph.CO↗

arXiv2017

The International Cosmic Day - An Outreach Event for Astroparticle Physics

The International Cosmic Day (ICD) is an astroparticle physics outreach event for high-school students and brings together students and different physics outreach projects from all over the world. Groups of scientists, teachers, and students meet for one day to learn about cosmic rays and perform an experiment with atmospheric muons. All participating groups investigate an identical question. The students are enabled to work together like in an international collaboration, discussing their results in joint video conferences. Analyzing data, comparing and discussing with other "young scientists" gives the students a glimpse of how professional scientific research works. Scientists join the video conferences and give lectures to provide an insight in current astroparticle physics research. Several participating research experiments analyze big science data tailored to the questions addressed by the students and present their results on equal terms with the students. To create a lasting event, proceedings with measurement results of all participating groups are published. Every participant receives a personal e-mail with his certificate and the proceedings booklet. Organized by DESY in cooperation with Netzwerk Teilchenwelt, IPPOG, QuarkNet, Fermilab, and national partners like INFN, the ICD is a growing event with more and more popularity. We present the organization of the event and the experience from five years of ICD.

astro-ph.IM↗

arXiv2016

Dark matter substructure modelling and sensitivity of the Cherenkov Telescope Array to Galactic dark halos

Hierarchical structure formation leads to a clumpy distribution of dark matter in the Milky Way. These clumps are possible targets to search for dark matter annihilation with present and future $γ$-ray instruments. Many uncertainties exist on the clump distribution, leading to disputed conclusions about the expected number of detectable clumps and the ensuing limits that can be obtained from non-detection. In this paper, we use the CLUMPY code to simulate thousands of skymaps for several clump distributions. This allows us to statistically assess the typical properties (mass, distance, angular size, luminosity) of the detectable clumps. Varying parameters of the clump distributions allows us to identify the key quantities to which the number of detectable clumps is the most sensitive. Focusing our analysis on two extreme clump configurations, yet consistent with results from numerical simulations, we revisit and compare various calculations made for the Fermi-LAT instrument, in terms of number of dark clumps expected and the angular power spectrum for the Galactic signal. We then focus on the prospects of detecting dark clumps with the future CTA instrument, for which we make a detailed sensitivity analysis using open-source CTA software. Based on a realistic scenario for the foreseen CTA extragalactic survey, and accounting for a post-trial sensitivity in the survey, we show that we obtain competitive and complementary limits to those based on long observation of a single bright dwarf spheroidal galaxy.

astro-ph.HE↗

arXiv2015

CLUMPY: Jeans analysis, $γ$-ray and neutrino fluxes from dark matter (sub-)structures

We present an update of the CLUMPY code for the calculation of the astrophysical J-factors (from dark matter annihilation/decay) for any Galactic or extragalactic dark matter halo including substructures: halo-to-halo concentration scatter may now be enabled, boost factors can include several levels of substructures, and triaxiality is a new option for dark matter haloes. This new version takes advantage of the CFITSIO and HEALPix libraries to propose FITS output maps using the HEALPix pixelisation scheme. Skymaps for $γ$-ray and $ν$ signals from generic annihilation/decay spectra are now direct outputs of CLUMPY. Making use of HEALPix routines, smoothing by a user-defined instrumental Gaussian beam and computing the angular power spectrum of the maps is now possible. In addition to these improvements, the main novelty is the implementation of a Jeans analysis module, to obtain dark matter density profiles from kinematic data in relaxed spherical systems (e.g., dwarf spheroidal galaxies). The code is also interfaced with the GreAT toolkit designed for Markov Chain Monte Carlo analyses, from which probability density functions and credible intervals can be obtained for velocity dispersions, dark matter profiles, and J-factors.

astro-ph.CO↗

arXiv2015

High energy astroparticle physics for high school students

The questions about the origin and type of cosmic particles are not only fascinating for scientists in astrophysics, but also for young enthusiastic high school students. To familiarize them with research in astroparticle physics, the Pierre Auger Collaboration agreed to make 1% of its data publicly available. The Pierre Auger Observatory investigates cosmic rays at the highest energies and consists of more than 1600 water Cherenkov detectors, located near Malargüe, Argentina. With publicly available data from the experiment, students can perform their own hands-on analysis. In the framework of a so-called Astroparticle Masterclass organized alongside the context of the German outreach network Netzwerk Teilchenwelt, students get a valuable insight into cosmic ray physics and scientific research concepts. We present the project and experiences with students.

astro-ph.IM↗

arXiv2015

Search for Galactic dark matter substructures with Cherenkov telescopes

Weakly interacting massive dark matter (DM) particles are expected to self-annihilate or decay, generating high-energy photons in these processes. This establishes the possibility for indirect detection of DM by γ-ray telescopes. For probing the secondary products of DM, accurate knowledge about the DM density distribution in potential astrophysical targets is crucial. In this contribution, the prospects for the detection of subhalos in the Galactic DM halo with present and future imaging atmospheric Cherenkov telescopes (IACT) are investigated. The source count distribution and angular power spectra for γ-rays originating from annihilating DM in subhalos are calculated from N-body simulation results. To study the systematic uncertainties coming from the modeling of the DM density distribution, parameters describing the γ-ray yield from subhalos are varied in 16 benchmark models. We conclude that Galactic subhalos of annihilating DM are probably too faint to be a promising target for IACT observations, even with the prospective Cherenkov Telescope Array (CTA).

astro-ph.CO↗

arXiv2011

On the black hole limit of electrically counterpoised dust configurations

By means of a simple scaling transformation any asymptotically flat Papapetrou-Majumdar solution of the Einstein-Maxwell equations corresponding to a localized regular distribution of electrically counterpoised dust can be reformulated as a one-parameter family of solutions admitting a black hole limit. In the limit, a characteristic separation of spacetimes occurs: From the exterior point of view, the extreme Reissner-Nordstrom metric outside the event horizon is formed. From the interior point of view, a regular, non-asymptotically flat (and in general non-spherically symmetric) spacetime with the extreme Reissner-Nordstrom near-horizon geometry at spatial infinity results.

gr-qc↗