Hunting dark matter in galaxy clusters with non-thermal electrons

ABSTRACT The electron population inferred to be responsible for the mini-halo within the Ophiuchus galaxy cluster is a steep power law in energy with a slope of 3.8. This is substantially different to that predicted by dark matter (DM) annihilation models. In this work, we present a method of indirect comparison between the observed electron spectrum and that predicted for indirect DM emissions. This method utilizes differences in the consequences of a given electron distribution on the subsequent spectral features of synchrotron emissions. To fully exploit this difference, by leveraging the fact that the peak and cut-off synchrotron frequencies are substantially different to hard power-law cases for WIMP masses above ∼50 GeV, we find that we need μJy sensitivities at frequencies above 10 GHz while being sensitive to arcminute scales. We explore the extent to which this electron spectrum comparison can be validated with the up-coming next-generation Very Large Array (ngVLA) instrument. We show that, with the ngVLA, this method allows us to produce far stronger constraints than existing VLA data, indeed these exceed the Fermi-LAT dwarf searches in a wide variety of annihilation channels and for all studied magnetic field scenarios.

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Accretion and jets in a low-luminosity AGN: the nucleus of NGC 1052

Astronomy and Astrophysics ◽

10.1051/0004-6361/202037516 ◽

2020 ◽

Vol 638 ◽

pp. A67

Author(s):

S. Falocco ◽

J. Larsson ◽

S. Nandi

Keyword(s):

Power Law ◽

Hot Spots ◽

Surrounding Medium ◽

Central Area ◽

Energy Bands ◽

Very Large Array ◽

X Ray ◽

Hard Power ◽

Photon Index ◽

Extended Emission

Aims. We aim to determine the properties of the central region of NGC 1052 using X-ray and radio data. NGC 1052 (z = 0.005) has been investigated for decades in different energy bands and shows radio lobes and a low-luminosity active galactic nucleus. Methods. We used X-ray images from Chandra and radio images from Very Large Array to explore the morphology of the central area. We also studied the spectra of the nucleus and the surrounding region using observations from Chandra and XMM-Newton. Results. We find diffuse soft X-ray radiation and hot-spots along the radio lobes. The spectrum of the circum-nuclear region is well described by a thermal plasma (T ∼ 0.6 keV) and a power law with photon index Γ ∼ 2.3. The nucleus shows a hard power law (Γ ∼ 1.4) modified by complex absorption. A narrow iron Kα line is also clearly detected in all observations, but there is no evidence for relativistic reflection. Conclusions. The extended emission is consistent with originating from extended jets and from jet-triggered shocks in the surrounding medium. The hard power-law emission from the nucleus and the lack of relativistic reflection supports the scenario of inefficient accretion in an advection-dominated accretion flow.

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Chandra and XMM–Newton observations of A2256: cold fronts, merger shocks, and constraint on the IC emission

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa2320 ◽

2020 ◽

Vol 497 (4) ◽

pp. 4704-4717

Author(s):

Chong Ge ◽

Ruo-Yu Liu ◽

Ming Sun ◽

Heng Yu ◽

Lawrence Rudnick ◽

...

Keyword(s):

Power Law ◽

Electron Spectrum ◽

Galaxy Cluster ◽

X Ray ◽

Cold Fronts ◽

Inverse Compton ◽

Galaxy Kinematics ◽

The Magnetic Field ◽

Primary Cluster ◽

Shock Fronts

ABSTRACT We present the results of deep Chandra and XMM–Newton observations of a complex merging galaxy cluster Abell 2256 (A2256) that hosts a spectacular radio relic (RR). The temperature and metallicity maps show clear evidence of a merger between the western subcluster (SC) and the primary cluster (PC). We detect five X-ray surface brightness edges. Three of them near the cluster centre are cold fronts (CFs): CF1 is associated with the infalling SC; CF2 is located in the east of the PC; and CF3 is located to the west of the PC core. The other two edges at cluster outskirts are shock fronts (SFs): SF1 near the RR in the NW has Mach numbers derived from the temperature and the density jumps, respectively, of MT = 1.62 ± 0.12 and Mρ = 1.23 ± 0.06; SF2 in the SE has MT = 1.54 ± 0.05 and Mρ = 1.16 ± 0.13. In the region of the RR, there is no evidence for the correlation between X-ray and radio substructures, from which we estimate an upper limit for the inverse-Compton emission, and therefore set a lower limit on the magnetic field (∼ 450 kpc from PC centre) of B > 1.0 μG for a single power-law electron spectrum or B > 0.4 μG for a broken power-law electron spectrum. We propose a merger scenario including a PC, an SC, and a group. Our merger scenario accounts for the X-ray edges, diffuse radio features, and galaxy kinematics, as well as projection effects.

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Spectral Index of the Filaments in the Abell 523 Radio Halo

Galaxies ◽

10.3390/galaxies9040112 ◽

2021 ◽

Vol 9 (4) ◽

pp. 112

Author(s):

Valentina Vacca ◽

Federica Govoni ◽

Richard A. Perley ◽

Matteo Murgia ◽

Ettore Carretti ◽

...

Keyword(s):

Spectral Index ◽

Galaxy Cluster ◽

Large Array ◽

Spectral Indices ◽

Very Large Array ◽

Radio Halo ◽

Highly Efficient ◽

The Galaxy

The galaxy cluster Abell 523 hosts a radio halo characterized by the presence of two filaments transversely located with respect to the cluster merger axis. In this paper, we present a spectral index image of these filaments between 1.410 and 1.782 GHz obtained with Jansky Very Large Array observations. We find a steepening of the spectral index of the filaments at frequencies ≳1.4 GHz and an indication that bright patches are characterized by flat spectral indices. Our results are consistent with a scenario of highly-efficient turbulence induced by merger phenomena.

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Multiwavelength analysis of OH Megamaser galaxies: The case of IRAS11506-3851

Proceedings of the International Astronomical Union ◽

10.1017/s1743921320004317 ◽

2020 ◽

Vol 15 (S359) ◽

pp. 347-349

Author(s):

Carpes P. Hekatelyne ◽

Thaisa Storchi-Bergmann

Keyword(s):

Active Galactic Nuclei ◽

Hubble Space Telescope ◽

Galactic Nuclei ◽

Large Array ◽

Very Large Array ◽

Star Forming ◽

Star Forming Regions ◽

Field Unit ◽

Mixed Transition ◽

Integral Field

AbstractWe present Multi-Object Spectrograph (GMOS) Integral Field Unit (IFU), Hubble Space Telescope (HST) and Very Large Array (VLA) observations of the inner kpc of the OH Megamaser galaxy IRAS 11506-3851. In this work we discuss the kinematics and excitation of the gas as well as its radio emission. The HST images reveal an isolated spiral galaxy and the combination with the GMOS-IFU flux distributions allowed us to identify a partial ring of star-forming regions surrounding the nucleus with a radius of ≍500 pc. The emission-line ratios and excitation map reveal that the region inside the ring present mixed/transition excitation between those of Starbursts and Active Galactic Nuclei (AGN), while regions along the ring are excited by Starbursts. We suggest that we are probing a buried or fading AGN that could be both exciting the gas and originating an outflow.

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Study of a wide-area coherent/synchronous system for next generation Very Large Array

2020 IEEE International Symposium on Antennas and Propagation and North American Radio Science Meeting ◽

10.1109/ieeeconf35879.2020.9329617 ◽

2020 ◽

Author(s):

Hitoshi Kiuchi

Keyword(s):

Wide Area ◽

Large Array ◽

Next Generation ◽

Very Large Array ◽

Synchronous System

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OH main line masers in the M 82 starburst

Proceedings of the International Astronomical Union ◽

10.1017/s1743921307013543 ◽

2007 ◽

Vol 3 (S242) ◽

pp. 427-431

Author(s):

M. K. Argo ◽

A. Pedlar ◽

T. W. B. Muxlow ◽

R. J. Beswick

Keyword(s):

Central Region ◽

Supernova Remnants ◽

Main Line ◽

Line Of Sight ◽

Starburst Galaxy ◽

Large Array ◽

Satellite Line ◽

Very Large Array

AbstractA study of the distribution of OH gas in the central region of the nearby active starburst galaxy M82 has confirmed two previously known bright masers and revealed several new main line masers. Three of these are seen only at 1665 MHz, one is detected only at 1667 MHz, while the rest are detected in both lines. Observations covering both the 1665 and 1667 MHz lines, conducted with both the Very Large Array (VLA) and the Multi-Element Radio Linked Interferometer Network (MERLIN), have been used to accurately measure the positions and velocities of these features. This has allowed a comparison with catalogued continuum features in the starburst such as HII regions and supernova remnants, as well as known water and satellite line OH masers. Most of the main line masers appear to be associated with known HII regions although the two detected only at 1665 MHz are seen along the same line of sight as known supernova remnants.

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Bipolar outflow of gas in the spiral galaxy NGC 3079

Canadian Journal of Physics ◽

10.1139/p86-100 ◽

1986 ◽

Vol 64 (4) ◽

pp. 531-535 ◽

Cited By ~ 1

Author(s):

Nebojsa Duric ◽

E. R. Seaquist

Keyword(s):

Spectral Index ◽

Spiral Galaxy ◽

Central Region ◽

Qualitative Description ◽

Radio Continuum ◽

Large Array ◽

Very Large Array ◽

Bipolar Outflow ◽

The Galaxy

Very large array, radio-continuum observations of the edge-on spiral galaxy NGC 3079 are presented. The observations reveal that the nucleus has windlike properties and that the central region of the galaxy exhibits an unusual figure-eight morphology that shows evidence of severe depolarization and a flattening spectral index away from the nucleus. A qualitative description of a model is presented to account for the observed radio properties. It is shown that a wind-driven shock propagating away from the nucleus and focused by the ambient disk gas can give rise to the observed morphology.

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