Dark photon is a new gauge boson beyond the Standard Model as a kind of dark matter (DM) candidate. Dark photon dark matter (DPDM) interacts with electromagnetic fields via kinetic mixing, implicating an approach to give a constraint with extragalactic very high energy (VHE) sources. In this work, we attempt to constrain the kinetic mixing from the photon-dark photon scattering process in the host galaxy of blazar, the intergalactic medium and the Milky Way. The VHE photons from a blazar would pass through a dense DM spike around the supermassive black hole where the absorption from DPDM is dramatically enhanced. The kinetic mixing is constrained to be $ε\sim 10^{-7}$ at a 95$\%$ confidence level with $m_{\rm D}\sim 0.03 - 1$ eV mass range from the observations of Markarian (Mrk) 421 and Mrk 501.
Our goal is to research the upper limits on the extragalactic background light (EBL). The upper limits on the extragalactic background light (EBL), using the Fermi and very high energy (VHE) spectra recently observed in TeV blazars, are presented. We use an assumption that the VHE intrinsic photon index cannot be harder than the Fermi index measured by the Fermi-LAT. Totally, these upper limits on the EBL are compatible with ones given by most of EBL models. However, the models of high EBL density are denied by TeV blazars.
Recently, a new method to constrain the distances of blazars with unknown redshift using combined observations in the GeV and TeV regimes has been developed. The underlying assumption is that the Very High Energy (VHE, E > 100 GeV) spectrum corrected for the absorption of TeV photons by the Extragalactic Background Light (EBL) via photon-photon interaction should still be softer than the gamma-ray spectrum observed by Fermi/LAT. The constraints found are related to the real redshifts by a simple linear relation, that has been used to infer the unknown or uncertain distance of blazars. The samp…
In this paper, we present a novel method to test the Einstein's Equivalence Principle (EEP) using (simultaneous) multi-wavelength radio observations of polarized blazars. We analyze simultaneous multi-wavelength polarization observations of 3C 279 at 22, 43, and 86 GHz obtained by two antennas of the Korean VLBI Network. We obtained 15 groups of polarization data, and applied the Metropolis-Hastings Markov Chain (MHMC) to simulate the parameters when considering the EEP effect and the simplest form of Faraday rotation (single external Faraday screen). The final results show the constraint of t…
The X-ray spectrum of extreme HBL type blazars is located in the synchrotron branch of the broadband spectral energy distribution (SED), at energies below the peak. A joint fit of the extrapolated X-ray spectra together with a host galaxy template allows characterizing the synchrotron branch in the SED. The X-ray spectrum is usually characterized either with a pure or a curved power-law model. In the latter case, however, it is hard to distinguish an intrinsic curvature from excess absorption. In this paper, we focus on five well-observed blazars: 1ES 0229+200, PKS 0548-322, RX J1136+6737, 1ES…
Relativistic effects dominate the emission of blazar jets complicating our understanding of their intrinsic properties. Although many methods have been proposed to account for them, the variability Doppler factor method has been shown to describe the blazar populations best. We use a Bayesian hierarchical code called {\it Magnetron} to model the light curves of 1029 sources observed by the Owens Valley Radio Observatory's 40-m telescope as a series of flares with an exponential rise and decay, and estimate their variability brightness temperature. Our analysis allows us to place the most strin…
We analyze the shock-in-jet models for the gamma-ray flaring blazars 0420-014, OJ 287, and 1156+295 presented in Aller et al. (2014, Paper I), quantifying how well the modeling constrains internal properties of the flow (low energy spectral cutoff, partition between random and ordered magnetic field), the flow dynamics (quiescent flow speed and orientation), and the number and strength of the shocks responsible for radio-band flaring. We conclude that well-sampled, multifrequency polarized flux light curves are crucial for defining source properties. We argue for few, if any, low energy partic…
In this paper, we discuss an artificial intelligence based approach to constrain the redshift of blazars using combined $γ$--ray observations from the \emph{Fermi} Large Area Telescope (LAT) and ground based atmospheric Cherenkov telescopes (ACTs) in GeV and \emph{sub} TeV energy regimes respectively. The spectral measurements in GeV and TeV energy bands show a redshift dependent spectral break in the $γ$--ray spectra of blazars. We use this observational feature of blazars to constrain their redshift. The observed spectral information of blazars with known redshifts reported in the \emph{Ferm…
We discuss a method to constrain the distance of blazars with unknown redshift using combined observations in the GeV and TeV regimes. We assume that the VHE spectrum corrected for the absorption through the interaction with the Extragalactic Background Light can not be harder than the spectrum in the Fermi/LAT band. Starting from the observed VHE spectral data we derive the EBL-corrected spectra as a function of the redshift z and fit them with power laws to be compared with power law fits to the LAT data. We apply the method to all TeV blazars detected by LAT with known distance and derive a…
The spatially resolved broad-band spectroscopy with Very Long Baseline Interferometry (VLBI) is one of the few methods that can probe the physical conditions inside blazar jets. We report on measurements of the magnetic field strength in parsec-scale radio structures of selected bright Fermi blazars, based on fitting the synchrotron spectrum to VLBA images made at seven frequencies in a 4.6 -- 43.2 GHz range. Upper limits of B <= 10^-2 -- 10^2 G (observer's frame) could be placed on the magnetic field strength in 13 sources. Hard radio spectra (-0.5 <= a <= +0.1, S_nu ~ nu^a) observed above th…
Axion-like particles (ALPs) are a broad class of pseudo-scalar bosons that generically arise from broken symmetries in extensions of the standard model. In many scenarios, ALPs can mix with photons in regions with high magnetic fields. Photons from distant sources can mix with ALPs, which then travel unattenuated through the Universe, before they mix back to photons in the Milky Way galactic magnetic field. Thus, photons can traverse regions where their signals would normally be blocked or attenuated. In this paper, we study TeV $γ$-ray observations from distant blazars, utilizing the signific…
Many luminous blazars which are associated with quasar-type active galactic nuclei display broad-band spectra characterized by a large luminosity ratio of their high-energy (gamma-ray) and low-energy (synchrotron) spectral components. This large ratio, reaching values up to 100, challenges the standard synchrotron self-Compton models by means of substantial departures from the minimum power condition. Luminous blazars have also typically very hard X-ray spectra, and those in turn seem to challenge hadronic scenarios for the high energy blazar emission. As shown in this paper, no such problems …
To investigate parsec-scale jet flow conditions during GeV gamma-ray flares detected by the Fermi Large Angle Telescope, we obtained centimeter-band total flux density and linear polarization monitoring observations from 2009.5 through 2012.5 with the 26-meter Michigan radio telescope for a sample of core-dominated blazars. We use these data to constrain radiative transfer simulations incorporating propagating shocks oriented at an arbitrary angle to the flow direction in order to set limits on the jet flow and shock parameters during flares temporally associated with gamma-ray flares in 0420-…
The intermediate-frequency-peaked BL Lac object 3C 66A was detected in a flaring state by the Fermi-LAT and VERITAS observatories in October 2008. These data and follow-up observations at other wavelengths create a rich sample of light curves and a constraining spectral energy distribution (SED). This is the first time that simultaneous observations at GeV and TeV energies were obtained for a flaring blazar. Results from these joint Fermi-LAT and VERITAS observations are presented in this conference proceeding.
Dark matter particles near the center of a blazar, after being accelerated by the elastic collisions with relativistic electrons and protons in the blazar jet, can be energetic enough to trigger detectable signals at terrestrial detectors. In this work, focusing on the blazars TXS 0506+056 and BL Lacertae, we derive novel limits on the cross section of the elastic scattering between dark matter and electrons by means of the available Super-Kamiokande data. Thanks to the large blazar-boosted dark matter flux, the limit on the dark matter-electron scattering cross section for dark matter masses …
We explore the possibility that relativistic protons in the extremely powerful jets of blazars may boost via elastic collisions the dark matter particles in the surroundings of the source to high energies. We concentrate on two sample blazars, TXS 0506+056 - towards which IceCube recently reported evidence for a high-energy neutrino flux - and BL Lacertae, a representative nearby blazar. We find that the dark matter flux at Earth induced by these sources may be sizable, larger than the flux associated with the analogous process of dark matter boosted by galactic cosmic rays, and relevant to ac…
In the past decade, gamma-ray observations and radio observations of our Milky Way and the Milky Way dwarf spheroidal satellite galaxies put very strong constraints on annihilation cross sections of dark matter. In this article, we suggest a new target object (NGC 2976) that can be used for constraining annihilating dark matter. The radio and x-ray data of NGC 2976 can put very tight constraints on the leptophilic channels of dark matter annihilation. The lower limits of dark matter mass annihilating via $e^+e^-$, $μ^+μ^-$ and $τ^+τ^-$ channels are 200 GeV, 130 GeV and 110 GeV respectively wit…
Locating the gamma-ray emission sites in blazar jets is a long-standing and highly controversial issue. We investigate jointly several constraints on the distance scale r and Lorentz factor Gamma of the gamma-ray emitting regions in luminous blazars (primarily flat spectrum radio quasars, FSRQs). Working in the framework of one-zone external radiation Comptonization (ERC) models, we perform a parameter space study for several representative cases of actual gamma-ray flares in their multiwavelength context. We find a particularly useful combination of three constraints: from an upper limit on t…
The Hawking evaporation of small black holes formed by the collapse of dark matter at the center of neutron stars plays a key role in loosing the constraint on the mass of asymmetric bosonic non-interacting dark matter particles. Different from previous works we show that such a kind of dark matter is viable in the mass range from 3.3 GeV to ~ 10 TeV, which covers the most attractive regions, including the preferred asymmetric dark matter mass ~ 5.7 GeV as well as the 5-15 GeV range favored by DAMA and CoGeNT.
Constraining the synchrotron peak and estimating the VHE brightness of a sample of extreme high synchrotron peak blazars
Università di Bologna（博洛尼亚大学）；INAF-Osservatorio di Astrofisica e Scienza dello Spazio (OAS)（意大利国家天体物理研究所空间科学与天体物理观测台）；Clemson University（克莱姆森大学）；INFN Sezione di Padova and Università degli Studi di Padova（帕多瓦大学意大利国家核物理研究所帕多瓦分部）；Deutsches Elektronen-Synchrotron DESY（德国电子同步辐射研究所）
The location of $γ$-ray emitting region in blazars has been an open issue for several decades and is still being debated. We use the Paliya et al. sample of 619 $γ$-ray-loud flat-spectrum radio quasars with the available spectral energy distributions, and employ a seed photon factor approach, to locate the $γ$-rays production region. This method efficiently set up a relation between the peak frequencies and luminosities for the synchrotron emission and inverse Compton scattering, together with a combination of the energy density and characteristic energy for the external seed photon field, nam…
Constraining the Photon Intensity of Extragalactic Background Light with the HAWC Observatory for the Blazar Mrk 421
Instituto de Física, Universidad Nacional Autónoma de México（墨西哥国立自治大学物理研究所）；Universidad Autónoma de Chiapas（恰帕斯自治大学）；Instituto de Astronomía, Universidad Nacional Autónoma de México（墨西哥国立自治大学天文学研究所）；Universidad de Costa Rica（哥斯达黎加大学）；Universidad Michoacana de San Nicolás de Hidalgo（米却肯圣尼古拉斯德伊达尔戈大学）；Department of Physics and Astronomy, Michigan State University（密歇根州立大学物理与天文系）；Temple University（天普大学）
Recent studies of radio data put strong constraints on annihilation cross section for dark matter. In this article, we provide the first analysis of using M33 radio data in constraining annihilating dark matter. The resulting constraints of annihilation cross sections for some channels are more stringent than that obtained from 6 years of Fermi Large Area Telescope (Fermi-LAT) gamma-ray observations of the Milky Way dwarf spheroidal satellite galaxies. In particular, the conservative lower limits of dark matter mass annihilating via $e^+e^-$, $μ^+μ^-$and $τ^+τ^-$ channels are 190 GeV, 120 GeV …
Context: Hadronic models, involving matter (proton or nuclei) acceleration in blazar jets, imply high energy photon and neutrino emissions due to interactions of high-energy protons with matter and/or radiation in the source environment. Aims: This paper shows that the sensitivity of the IceCube neutrino telescope in its 40-string configuration (IC-40) is already at the level of constraining the parameter space of purely hadronic scenarios of activity of blazars. Methods: Assuming that the entire source power originates from hadronic interactions, and assuming that the models describe the data…
Dwarf spheroidal galaxies have a large mass to light ratio and low astrophysical background, and are therefore considered one of the most promising targets for dark matter searches in the gamma-ray band. By applying a joint likelihood analysis, the power of resultant limits in case of no detection can be enhanced and robust constraints on the dark matter parameter space can be obtained. We present results from a combined analysis of 10 dwarf spheroidal galaxies using Fermi-LAT data. Different annihilation channels have been analyzed and uncertainties from astrophysical properties have been tak…
Dwarf spheroidal galaxies are compact stellar objects with small or negligible astrophysical backgrounds, widely considered as promising targets to search for a signal from the dark matter decay and annihilation. We present constraints on the lifetime of the superheavy decaying dark matter branching to the $q\bar{q}$ channel in the mass range $10^{19} - 10^{25}$ eV based on the directional limits on the ultra-high-energy (UHE) gamma rays obtained by the Pierre Auger Observatory and the Telescope Array experiment. Attenuation effects during the propagation of UHE photons towards Earth are taken…
Neutrino emission in coincidence with gamma rays has been observed from the blazar TXS 0506+056 by the IceCube telescope. Neutrinos from the blazar had to pass through a dense spike of dark matter (DM) surrounding the central black hole. The observation of such a neutrino implies new upper bounds on the neutrino-DM scattering cross section as a function of DM mass. The constraint is stronger than existing ones for a range of DM masses, if the cross section rises linearly with energy. For constant cross sections, competitive bounds are also possible, depending on details of the DM spike.
Setting limits on blazar-boosted dark matter with xenon-based detectors
University of Zurich（苏黎世大学）；The University of Sydney（悉尼大学）；European Southern Observatory（欧洲南方天文台）；New York University Abu Dhabi（阿布扎比纽约大学）；University of Oslo（奥斯陆大学）；University of California（加利福尼亚大学）
Relativistic jets from blazars are known to be sources of very-high-energy gamma rays (VHEGRs). During their propagation in the intergalactic space, VHEGRs interact with pervasive cosmological photon fields such as the extragalactic background light (EBL) and the cosmic microwave background (CMB), producing electron-positron pairs. These pairs can upscatter CMB/EBL photons to high energies via inverse Compton scattering, thereby continuing the cascade process. This is often used to set limits on intergalactic magnetic fields (IGMFs). However, the picture may change if plasma instabilities, ari…
We use the recent measurement of the isotropic $γ$-ray background (IGRB) by Fermi LAT and analysis of the contribution of unresolved point $γ$-ray sources to IGRB to build constraints on the models of ultra-high cosmic rays (UHECR) origin. We also calculate the minimal expected diffuse $γ$-ray flux produced by UHECR interactions with an interstellar photon background. Finally, for the subclass of dark matter (DM) models with decaying weakly interacting massive particles (WIMP), we build constraints on the particle decay time using minimal expected contributions to the IGRB from unresolved poin…
We study the quasi-simultaneous near-IR, optical, UV, and X-ray photometry of eleven gamma-ray selected blazars for which redshift estimates larger than 1.2 have been recently provided. Four of these objects turn out to be high-power blazars with the peak of their synchrotron emission between ~ 3 x 10^15 and ~ 10^16 Hz, and therefore of a kind predicted to exist but never seen before. This discovery has important implications for our understanding of physical processes in blazars, including the so-called "blazar sequence", and might also help constraining the extragalactic background light thr…
At redshift larger than 3 there is a disagreement between the number of blazars (whose jet is pointing at us) and the number of expected parents (whose jet is pointing elsewhere). Now we strengthen this claim because (i) the number of blazars identified within the SDSS+FIRST survey footprint increased, demanding a more numerous parent population, and (ii) the detected blazars have a radio flux large enough to be above the FIRST flux limit even if the jet is slightly misaligned. The foreseen number of these slightly misaligned jets, in principle detectable, is much larger than the radio-detecte…
The origin of the extragalactic $γ$-ray background (EGB) has been debated for some time. { The EGB comprises the $γ$-ray emission from resolved and unresolved extragalactic sources, such as blazars, star-forming galaxies and radio galaxies, as well as radiation from truly diffuse processes.} This letter focuses on the blazar source class, the most numerous detected population, and presents an updated luminosity function and spectral energy distribution model consistent with the blazar observations performed by the {\it Fermi} Large Area Telescope (LAT). We show that blazars account for 50$^{+1…
Our Moon is a natural giant direct-detection target for constraining dark matter. By considering the dark matter capture rate of the Moon, we obtain some constraints of the spin-independent elastic scattering cross section of dark matter particles on nucleons $σ_p^{\rm SI}$ using the background neutrino data. The upper limits of $σ_p^{\rm SI}$ can be constrained to $\sim 10^{-38}-10^{-36}$ cm$^2$ for certain `resonance dark matter mass' ranges. These stringent astrophysical constraints are complementary to the constraints obtained by the direct-detection experiments.
The Fermi LAT collaboration has recently presented constraints on the gamma-ray signal from annihilating dark matter using separate analyses of a number of dwarf spheroidal galaxies. Since the expected annihilation signal has the same physical properties regardless of the target (except for a normalization scale), it is possible to enhance the constraining power using a combined analysis, the initial results of which will be presented here.
We consider decaying dark matter with masses $10^{7} \lesssim M \lesssim 10^{16}$ GeV, as a source of ultra-high energy (UHE) gamma rays. Using recent limits on UHE gamma-ray flux for energies $E_γ> 2 \cdot 10^{14}$ eV, provided by extensive air shower observatories, we put limits on masses and lifetimes of the dark matter. We also discuss possible dark matter decay origin of tentative 100 PeV photon flux detected with EAS-MSU experiment.
Studying the propagation of gamma rays on cosmological distances encompasses a variety of scientific fields, focusing on diffuse radiation fields such as the extragalactic background light, on the probe of the magnetism of the Universe on large scales, and on physics beyond the standard models of cosmology and particle physics. The measurements, constraints and hints from observations of gamma-ray blazars by airborne and ground-based instruments are briefly reviewed. These observations point to gamma-ray cosmology as one of the major science cases of the Cherenkov Telescope Array, CTA.
We revisited the decaying dark matter (DDM) model, in which one collisionless particle decays early into two collisionless particles, that are potentially dark matter particles today. The effect of DDM will be manifested in the cosmic microwave background (CMB) and structure formation. With a systematic modification of CMB calculation tool \texttt{camb}, we can numerically calculated this effect, and compare it to observations. Further Markov Chain Monte Carlo \texttt{cosmomc} runnings update the constraints in that model: the free streaming length $λ_{FS}\lesssim0.5$Mpc for nonrelativistic de…
Very-high energy observations of blazars can be used to constrain the strength of the intergalactic magnetic field. A simplifying assumption which is often made is that of a magnetic field of constant strength composed by randomly oriented and identical cells. In this paper, we demonstrate that a more realistic description of the structure of the intergalactic magnetic field is indeed needed. If such a description is adopted, the observational bounds on the field strength are significantly affected in the limit of short field correlation lengths: in particular, they acquire a dependence on the…
We put constraints on asymmetric dark matter candidates with spin-dependent interactions based on the simple existence of white dwarfs and neutron stars in globular clusters. For a wide range of the parameters (WIMP mass and WIMP-nucleon cross section), WIMPs can be trapped in progenitors in large numbers and once the original star collapses to a white dwarf or a neutron star, these WIMPs might self-gravitate and eventually collapse forming a mini-black hole that eventually destroys the star. We impose constraints competitive to direct dark matter search experiments, for WIMPs with masses down…
We employ data from the recently observed high-energy neutrino events at the IceCube Neutrino Observatory to constrain interactions between the dark matter (DM) in the Milky Way and the neutrino sector. We construct an extended un-binned likelihood in order to explore the parameter space of allowed interactions. We present results in the specific case of a scalar DM candidate interacting via a scalar mediator, and show that due to the energy dependence of the interaction cross section, this approach can constrain the coupling more strongly than traditional cosmological probes for some regions …
We perform a detailed examination of current constraints on annihilating and decaying dark matter models from both prompt and inverse-Compton emission photons, including both model-dependent and model-independent bounds. We also show that the observed isotropic diffuse gamma-ray background (DGRB), which provides one of the most conservative constraints on models of annihilating weak-scale dark matter particles, may enhance its sensitivity by a factor of ~2 to 3 (95% C.L.) as the Fermi-LAT experiment resolves DGRB contributing blazar sources with five years of observation. For our forecasts, we…
Recent gamma-ray and radio observations provide stringent constraints for annihilating dark matter. The current $2σ$ lower limits of dark matter mass can be constrained to $\sim 100$ GeV for thermal relic annihilation cross section. In this article, we use the radio continuum spectral data of a nearby galaxy NGC4214 and differentiate the thermal contribution, dark matter annihilation contribution and cosmic-ray contribution. We can get more stringent constraints of dark matter mass and annihilation cross sections. The $5σ$ lower limits of thermal relic annihilating dark matter mass obtained ar…
Recently, constraints on bosonic asymmetric dark matter have been imposed based on the existence of old neutron stars excluding the dark matter masses in the range from $\sim 2$ keV up to several GeV. The constraints are based on the star destruction scenario where the dark matter particles captured by the star collapse forming a black hole that eventually consumes the host star. In addition, there were claims in the literature that similar constraints can be obtained for dark matter masses heavier than a few TeV. Here we argue that it is not possible to extend to these constraints. We show th…
The 79-string IceCube search for dark matter in the Sun public data is used to test Secluded Dark Matter models. No significant excess over background is observed and constraints on the parameters of the models are derived. Moreover, the search is also used to constrain the dark photon model in the region of the parameter space with dark photon masses between 0.22 and $\sim$ 1 GeV and a kinetic mixing parameter $\varepsilon \sim 10^{-9}$, which remains unconstrained. These are the first constraints of dark photons from neutrino telescopes. It is expected that neutrino telescopes will be effici…
Cosmic-ray observations provide a powerful probe of dark matter annihilation in the Galaxy. In this paper we derive constraints on heavy dark matter from the recent precise AMS-02 antiproton data. We consider all possible annihilation channels into pairs of standard model particles. Furthermore, we interpret our results in the context of minimal dark matter, including higgsino, wino and quintuplet dark matter. We compare the cosmic-ray antiproton limits to limits from $γ$-ray observations of dwarf spheroidal galaxies and to limits from $γ$-ray and $γ$-line observations towards the Galactic cen…
Recent radio observations have obtained stringent constraints for annihilating dark matter. In this article, we use the radio continuum spectral data of the Large Magellanic Cloud (LMC) to analyze the dark matter annihilation signals. We have discovered a slightly positive signal of dark matter annihilation with a $1.5σ$ statistical significance. The overall best-fit dark matter mass is $m_{\rm DM} \approx 90$ GeV, annihilating via $b\bar{b}$ channel. We have also constrained the $3σ$ lower limits of dark matter mass with the standard thermal dark matter annihilation cross section for the $e^+…
Probing Extragalactic Ultralight Axion Dark Matter with Decade-long Blazar Optical Polarimetry of 1ES 1959+650
Purple Mountain Observatory, Chinese Academy of Sciences（中国科学院紫金山天文台）；School of Astronomy and Space Sciences, University of Science and Technology of China（中国科学技术大学天文与空间科学学院）
In the past decade, the properties of annihilating dark matter models were examined by various kinds of data, including the data of gamma rays, radio waves, X-ray, positrons, electrons, antiprotons and neutrinos. In particular, most of the studies focus on the data of our Galaxy, nearby galaxies (e.g. M31 galaxy) or nearby galaxy clusters (e.g. Fornax cluster). In this article, we examine the archival radio continuum spectral data of a relatively high-redshift galaxy cluster (A697 cluster) to constrain the properties of annihilating dark matter. We find that leptophilic annihilation channels (…
We present the first branon dark matter (DM) search in the very high-energy gamma-ray band with observations of the dwarf spheroidal galaxy Segue~1 carried out by the Major Atmospheric Gamma Imaging Cherenkov (MAGIC) telescope system. Branons are new degrees of freedom that appear in flexible brane-world models corresponding to brane fluctuations. They behave as weakly interacting massive particles, which are natural DM candidates. In the absence of a gamma-ray signal in the Segue~1 data, we place constraints on the branon DM parameter space by using a binned likelihood analysis. Our most cons…
