31. Sensitivity of the Cherenkov Telescope Array to a dark matter signal from the Galactic centreChristopher Eckner, Saptashwa Bhattacharyya, Barbara MARČUN, Judit Pérez Romero, Samo Stanič, Veronika Vodeb, Serguei Vorobiov, Gabrijela Zaharijas, Marko Zavrtanik, Danilo Zavrtanik, Miha Živec, 2021, published scientific conference contribution Abstract: High-energy gamma rays are promising tools to constrain or reveal the nature of dark matter, in particular Weakly Interacting Massive Particles. Being well into its pre-construction phase, the Cherenkov Telescope Array (CTA) will soon probe the sky in the 20 GeV - 300 TeV energy range. Thanks to its improved energy and angular resolutions as well as significantly larger e˙ective area when compared to the current generation of Cherenkov telescopes, CTA is expected to probe heavier dark matter, with unprecedented sensitivity, reaching the thermal annihilation cross-section at 1 TeV.
This talk will summarise the planned dark matter search strategies with CTA, focusing on the signal from the Galactic centre. As observed with the Fermi LAT at lower energies, this region is rather complex and CTA will be the first ground-based observatory sensitive to the large scale di˙use astrophysical emission from that region. We report on the collaboration e˙ort to study the impact of such extended astrophysical backgrounds on the dark matter search, based on Fermi-LAT data in order to guide our observational strategies, taking into account various sources of systematic uncertainty.
Keywords: high-energy gamma rays, Cherenkov Telescope Array, dark matter, galactic centre
Published in RUNG: 18.09.2023; Views: 542; Downloads: 8
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32. Cherenkov Telescope Array: the World's largest VHE gamma-ray observatoryRoberta Zanin, Saptashwa Bhattacharyya, Barbara MARČUN, Judit Pérez Romero, Samo Stanič, Veronika Vodeb, Serguei Vorobiov, Gabrijela Zaharijas, Marko Zavrtanik, Danilo Zavrtanik, Miha Živec, 2021, published scientific conference contribution (invited lecture) Abstract: Very-High Energy (VHE) gamma-ray astroparticle physics is a relatively young field, and obser-vations over the past decade have surprisingly revealed almost two hundred VHE emitters which appear to act as cosmic particle accelerators. These sources are an important component of the Universe, influencing the evolution of stars and galaxies. At the same time, they also act as a probe of physics in the most extreme environments known - such as in supernova explosions, and around or after the merging of black holes and neutron stars. However, the existing experiments have provided exciting glimpses, but often falling short of supplying the full answer. A deeper understanding of the TeV sky requires a significant improvement in sensitivity at TeV energies, a wider energy coverage from tens of GeV to hundreds of TeV and a much better angular and energy resolution with respect to the currently running facilities. The next generation gamma-ray observatory, the Cherenkov Telescope Array Observatory (CTAO), is the answer to this need. In this talk I will present this upcoming observatory from its design to the construction, and its potential science exploitation. CTAO will allow the entire astronomical community to explore a new discovery space that will likely lead to paradigm-changing breakthroughs. In particular, CTA has an unprecedented sensitivity to short (sub-minute) timescale phenomena, placing it as a key instrument in the future of multi-messenger and multi-wavelength time domain astronomy. I will conclude the talk presenting the first scientific results obtained by the LST-1, the prototype of one CTA telescope type - the Large Sized Telescope, that is currently under commission.
Keywords: Very-High Energy Gamma-rays, Cherenkov Telescope Array
Published in RUNG: 18.09.2023; Views: 469; Downloads: 6
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33. Bright blazar flares with CTAM. Cerruti, Saptashwa Bhattacharyya, Judit Pérez Romero, Samo Stanič, Veronika Vodeb, Serguei Vorobiov, Danilo Zavrtanik, Marko Zavrtanik, Miha Živec, 2023, published scientific conference contribution Abstract: The TeV extragalactic sky is dominated by blazars, radio-loud active galactic nuclei with a
relativistic jet pointing towards the Earth. Blazars show variability that can be quite exceptional
both in terms of flux (orders of magnitude of brightening) and time (down to the minute timescale).
This bright flaring activity contains key information on the physics of particle acceleration and
photon production in the emitting region, as well as the structure and physical properties of the
jet itself. The TeV band is accessed from the ground by Cherenkov telescopes that image the
pair cascade triggered by the interaction of the gamma ray with the Earth’s atmosphere. The
Cherenkov Telescope Array (CTA) represents the upcoming generation of imaging atmospheric
Cherenkov telescopes, with a significantly higher sensitivity and larger energy coverage with
respect to current instruments. It will thus provide us with unprecedented statistics on blazar
light-curves and spectra. In this contribution we present the results from realistic simulations of
CTA observations of bright blazar flares, taking as input state-of-the-art numerical simulations of
blazar emission models and including all relevant observational constraints.
Keywords: active galactic nuclei, radio-loud AGN, blazars
Published in RUNG: 15.09.2023; Views: 673; Downloads: 5
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34. Chasing gravitational waves with the Cherenkov Telescope ArrayJ. G. Green, Saptashwa Bhattacharyya, Judit Pérez Romero, Samo Stanič, Veronika Vodeb, Serguei Vorobiov, Danilo Zavrtanik, Marko Zavrtanik, Miha Živec, 2023, published scientific conference contribution Abstract: The detection of gravitational waves (GWs) from a binary neutron star (BNS) merger by Advanced
LIGO and Advanced Virgo (GW170817), along with the discovery of the electromagnetic counterparts
of this GW event, ushered in a new era of multimessenger astronomy, providing the first
direct evidence that BNS mergers are progenitors of short gamma-ray bursts (GRBs). Such events
may also produce very-high-energy (VHE, > 100 GeV) photons which have yet to be detected
in coincidence with a GW signal. The Cherenkov Telescope Array (CTA) is a next-generation
VHE observatory which aims to be indispensable in this search, with an unparalleled sensitivity
and ability to slew anywhere on the sky within a few tens of seconds. Achieving such a feat
will require a comprehensive real-time strategy capable of coordinating searches over potentially
very large regions of the sky. This work will evaluate and provide estimations on the number of
GW-CTA events determined from simulated BNS systems and short GRBs, considering both on and
off-axis emission. In addition, we will present and discuss the prospects of potential follow-up
strategies with CTA.
Keywords: gravitational waves, binary neutron star merger, short gamma-ray bursts
Published in RUNG: 15.09.2023; Views: 759; Downloads: 4
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35. MINOT: Modeling the intracluster medium (non-)thermal content and observable prediction toolsRémi Adam, Hazal Gosku, A. Leingärtner-Goth, Steffano Ettori, R. Gnatyk, B. Hnatyk, Moritz Hütten, Judit Pérez Romero, Miguel Sánchez-Conde, Olga Sergijenko, original scientific article Abstract: In the past decade, the observations of diffuse radio synchrotron emission toward galaxy clusters revealed cosmic-ray (CR) electrons and magnetic fields on megaparsec scales. However, their origin remains poorly understood to date, and several models have been discussed in the literature. CR protons are also expected to accumulate during the formation of clusters and probably contribute to the production of these high-energy electrons. In order to understand the physics of CRs in clusters, combining of observations at various wavelengths is particularly relevant. The exploitation of such data requires using a self-consistent approach including both the thermal and the nonthermal components, so that it is capable of predicting observables associated with the multiwavelength probes at play, in particular in the radio, millimeter, X-ray, and γ-ray bands. We develop and describe such a self-consistent modeling framework, called MINOT (modeling the intracluster medium (non-)thermal content and observable prediction tools) and make this tool available to the community. MINOT models the intracluster diffuse components of a cluster (thermal and nonthermal) as spherically symmetric. It therefore focuses on CRs associated with radio halos. The spectral properties of the cluster CRs are also modeled using various possible approaches. All the thermodynamic properties of a cluster can be computed self-consistently, and the particle physics interactions at play are processed using a framework based on the Naima software. The multiwavelength observables (spectra, profiles, flux, and images) are computed based on the relevant physical process, according to the cluster location (sky and redshift), and based on the sampling defined by the user. With a standard personal computer, the computing time for most cases is far shorter than one second and it can reach about one second for the most complex models. This makes MINOT suitable for instance for Monte Carlo analyses. We describe the implementation of MINOT and how to use it. We also discuss the different assumptions and approximations that are involved and provide various examples regarding the production of output products at different wavelengths. As an illustration, we model the clusters Abell 1795, Abell 2142, and Abell 2255 and compare the MINOT predictions to literature data. While MINOT was originally build to simulate and model data in the γ-ray band, it can be used to model the cluster thermal and nonthermal physical processes for a wide variety of datasets in the radio, millimeter, X-ray, and γ-ray bands, as well as the neutrino emission.
Keywords: galaxy clusters, intracluster medium, cosmic rays, radiation mechanisms, numerical methods
Published in RUNG: 27.01.2023; Views: 936; Downloads: 0
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36. Classification of gamma-ray targets for velocity-dependent and subhalo-boosted dark-matter annihilationThomas Lacroix, Gaetán Facchinetti, Judit Pérez Romero, Martin Stref, Julien Lavalle, David Maurin, Miguel Sánchez-Conde, original scientific article Abstract: Gamma-ray observations have long been used to constrain the properties of dark matter (DM), with a strong focus on weakly interacting massive particles annihilating through velocity-independent processes. However, in the absence of clear-cut observational evidence for the simplest candidates, the interest of the community in more complex DM scenarios involving a velocity-dependent cross-section has been growing steadily over the past few years. We present the first systematic study of velocity-dependent DM annihilation (in particular p-wave annihilation and Sommerfeld enhancement) in a variety of astrophysical objects, not only including the well-studied Milky Way dwarf satellite galaxies, but nearby dwarf irregular galaxies and local galaxy clusters as well. Particular attention is given to the interplay between velocity dependence and DM halo substructure. Uncertainties related to halo mass, phase-space and substructure modelling are also discussed in this velocity-dependent context. We show that, for s-wave annihilation, extremely large subhalo boost factors are to be expected, up to 10^11 in clusters and up to 10^6–10^7 in dwarf galaxies where subhalos are usually assumed not to play an important role. Boost factors for p-wave annihilation are smaller but can still reach 10^3 in clusters. The angular extension of the DM signal is also significantly impacted, with e.g. the cluster typical emission radius increasing by a factor of order 10 in the s-wave case. We also compute the signal contrast of the objects in our sample with respect to annihilation happening in the Milky Way halo. Overall, we find that the hierarchy between the brightest considered targets depends on the specific details of the assumed particle-physics model.
Keywords: dark matter theory, dwarf galaxies, galaxy clusters, gamma-ray theory
Published in RUNG: 27.01.2023; Views: 1194; Downloads: 0
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37. Sensitivity of CTA to gamma-ray emission from the Perseus galaxy clusterJudit Pérez Romero, published scientific conference contribution Abstract: In these proceedings we summarize the current status of the study of the sensitivity of the Cherenkov Telescope Array (CTA) to detect diffuse gamma-ray emission from the Perseus galaxy cluster. Gamma-ray emission is expected in galaxy clusters both from interactions of cosmic rays (CR) with the intra-cluster medium, or as a product of annihilation or decay of dark matter
(DM) particles in case they are weakly interactive massive particles (WIMPs). The observation of Perseus constitutes one of the Key Science Projects to be carried out by the CTA Consortium. In this contribution, we focus on the DM-induced component of the flux. OurDMmodelling includes the substructures we expect in the main halo which will boost the annihilation signal significantly. We adopt an ON/OFF observation strategy and simulate the expected gamma-ray signals. Finally we compute the expected CTA sensitivity using a likelihood maximization analysis including the most recent CTA instrument response functions. In absence of signal, we show that CTA will allow us to provide stringent and competitive constraints on TeV DM, especially for the case of
DM decay.
Keywords: dark matter, gamma-ray astronomy, galaxy clusters, cosmic rays and astroparticles
Published in RUNG: 27.01.2023; Views: 1030; Downloads: 15
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38. Spatial extension of dark subhalos as seen by Fermi-LAT and the implications for WIMP constraintsJavier Coronado-Blázquez, Miguel Sánchez-Conde, Judit Pérez Romero, Alejandra Aguirre-Santaella, 2022, original scientific article Abstract: Spatial extension has been hailed as a “smoking gun” in the gamma-ray search of dark galactic subhalos, which would appear as unidentified sources for gamma-ray telescopes. In this work, we study the sensitivity of the Fermi-LAT to extended subhalos using simulated data based on a realistic sky model. We simulate spatial templates for a set of representative subhalos, whose parameters were derived from our previous work with N-body cosmological simulation data. We find that detecting an extended subhalo and finding an unequivocal signal of angular extension requires, respectively, a flux 2 to 10 times larger than in the case of a pointlike source. By studying a large grid of models, where parameters such as the WIMP mass, annihilation channel, or subhalo model are varied significantly, we obtain the response of the LAT as a function of the product of annihilation cross-section times the J-factor. Indeed, we show that spatial extension can be used as an additional “filter” to reject subhalos candidates among the pool of unidentified LAT sources, as well as a smoking gun for positive identification. For instance, typical angular extensions of a few tenths of a degree are expected for the considered scenarios. Finally, we also study the impact of the obtained LAT sensitivity to such extended subhalos on the achievable dark matter constraints, which are a few times less constraining than comparable point-source limits.
Keywords: dark matter, cosmic rays and astroparticles, gamma-ray astronomy, particle astrophysics, particle dark matter
Published in RUNG: 26.01.2023; Views: 1276; Downloads: 0
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39. Dark matter search in dwarf irregular galaxies with the Fermi Large Area TelescopeViviana Gammaldi, Judit Pérez Romero, Javier Coronado-Blázquez, Mattia di Mauro, Ekaterina Karukes, Miguel Sánchez-Conde, Paolo Salucci, 2021, original scientific article Abstract: We analyze 11 years of Fermi-Large Area Telescope (LAT) data corresponding to the sky regions of seven dwarf irregular (dIrr) galaxies. DIrrs are dark matter (DM)-dominated systems, proposed as interesting targets for the indirect search of DM with gamma rays. The galaxies represent interesting cases with a strong disagreement between the density profiles (core versus cusp) inferred from observations and numerical simulations. In this work, we addressed the problem by considering two different DM profiles, based on both the fit to the rotation curve (in this case, a Burkert cored profile) and results from N-body cosmological simulations (i.e., Navarro-Frenk-White cuspy profile). We also include halo substructure in our analysis, which is expected to boost the DM signal by a factor of 10 in halos such as those of dIrrs. For each DM model and dIrr, we create a spatial template of the expected DM-induced gamma-ray signal to be used in the analysis of Fermi-LAT data. No significant emission is detected from any of the targets in our sample. Thus, we compute upper limits on the DM annihilation cross section versus mass parameter space.
Among the seven dIrrs, we find IC10 and NGC6822 to yield the most stringent individual constraints, independently of the adopted DM profile. We also produce combined DM limits for all objects in the sample, which turn out to be dominated by IC10 for all DM models and annihilation channels, i.e., b¯b, τ+τ−, and W+W−. The strongest constraints are obtained for b¯b and are at the level of <σv>∼7×10−26 cm3 s−1 at mχ ∼ 6 GeV. Though these limits are a factor of ∼3 higher than the thermal relic cross section at low weakly interacting massive particles masses, they are independent from and complementary to those obtained by means of other targets.
Keywords: Dark matter, gamma-ray astronomy, galaxies, astronomical masses and mass distributions
Published in RUNG: 26.01.2023; Views: 976; Downloads: 0
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