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X-ray astronomy and fundamental physics

Scientific meeting

Starts:

October
242018

09:00

Ends:

October
252018

17:00

Location

Kavli Royal Society Centre, Chicheley Hall, Newport Pagnell, Buckinghamshire, MK16 9JJ

Overview

Theo Murphy international scientific meeting organised by Professor Joseph Conlon, Dr David Marsh and Dr Helen Russell.

X-ray: NASA/CXC/CfA/M.Markevitch et al.; Optical: NASA/STScI; Magellan/U.Arizona/D.Clowe et al.; Lensing Map: NASA/STScI; ESO WFI; Magellan/U.Arizona/D.Clowe et al; Athena: ESA and ACO team.

The use of X-ray astronomy for fundamental physics has been seen in two areas; dark matter through the 3.5 keV line, and in searches for axion-like particles. In advance of satellite technological leaps, this meeting brought together astronomy and particle physics communities with a focus on the ability of existing and future X-ray observatories to search for and constrain fundamental physics. It explored the opportunities open to astronomers to probe fundamental physics with both existing archival data and also with future satellites such as ATHENA. 

The schedule of talks and speaker biographies are available below. Recorded audio of the presentations will be available on this page after the meeting has taken place.

Enquiries: Contact the Scientific Programmes team.


Event organisers

Select an organiser for more information

Schedule of talks

24 October

Session 1 09:00-12:30

X-ray searches for dark matter

5 talks Show detail Hide detail

Chairs

Professor Malcolm Fairburn, King's College London, UK

09:05-09:30 The current status of 3.5 keV line and sterile neutrino dark matter

Professor Alexey Boyarsky, Leiden University, The Netherlands

Abstract

Professor Boyarsky will review the current status of the attempts to figure our the origin of the 3.5 kev line and of sterile neutrino as dark matter candidate.

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09:30-09:45 Discussion

09:45-10:15 Plasma models and charge exchange

Professor Jelle Kaastra, SRON and Leiden University, The Netherlands

Abstract

Charge exchange (CX) is the process where an electron is transferred from one atom to another. Here Professor Kaastra considers CX between cold, neutral hydrogen gas and hot plasma. The CX process can give rise to line radiation in the X–ray and other spectral bands. The spectrum for this process is quite different from the normal X–ray emission spectrum from the hot plasma. CX with oxygen ions has been seen in many spectra from Solar System objects. Professor Kaastra shows that the CX process in clusters of galaxies occurring between the hot intracluster gas and cold gas filaments is very effective and produces significant line radiation near 3.5 keV due to interaction with sulphur. Additional evidence for this process in clusters comes from grating spectra of clusters in the oxygen band, as well as from UV spectroscopy. Professor Kaastra concludes this presentation with a brief summary of atomic physics, spectral modelling and calibration issues related to the 3.5 keV band.

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10:15-10:30 Discussion

10:30-11:00 Coffee

11:00-11:30 X–ray probes of dark matter

Professor Tesla Jeltema, University of California, Santa Cruz, USA

Abstract

Professor Jeltema will discuss the use of X–ray observations to constrain particle dark matter models.  In particular, she will review searches for X–ray lines including observations of and constraints on the 3.5 keV line. She will also discuss the use of X–ray observations of galaxies and clusters to constrain dark matter self–interaction.

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11:30-11:45 Discussion

11:45-12:00 Laboratory X–ray astrophysics with highly charged ions

Dr Chintan Shah, Max Planck Institute for Nuclear Physics, Heidelberg, Germany

Abstract

X–ray observations provide insight into the state and dynamics of a variety of astrophysical plasmas. Its interpretation relies on synthetic spectra which are based on plasma models. Those models, in turn, depend heavily on the accurate knowledge of the underlying atomic processes. A recent Hitomi observation of the Perseus cluster [1] provided an unprecedented high–resolution spectrum. It revealed not only well–resolved lines originating from most abundant highly charged ions, but also uncovered significant shortcomings of present spectral packages SPEX and AtomDB, namely inaccurate energies and atomic–scale processes completely missing from the models. For example, a weak line feature around 3.5 keV found in the spectra of galaxy clusters sparked tremendous interest when it was attributed to a possible dark matter decay process [2]. However, charge exchange between bare sulphur ions and hydrogen, a process not included in spectral models, was found to be a more plausible explanation. This talk will report on laboratory electron beam ion trap experiments that compellingly supported charge–exchange mechanism for 3.5 keV X–ray line [3]. It will further underpin how the incomplete knowledge of atomic processes limits the amount of information that can be extracted from current and next–generation X–ray satellites such as Athena and XRISM.

REFERENCES:

[1] Hitomi Collaboration, Nature 535, 117–121 (2016)

[2] E Bulbul et al, Astrophys. J 789, 13 (2014)

[3] C Shah et al, Astrophys. J 833, 52 (2016)

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12:00-12:15 Sterile neutrino constraints from Chandra to eROSITA

Dr Florian Hofmann, Max Planck Institute for Extraterrestrial Physics (MPE), Germany

Abstract

There is an ongoing debate on the nature of the 3.55 keV emission line in X-ray spectra of astronomical objects. One possible explanation is the decay of 7.1 keV sterile neutrinos, which have been proposed as a candidate for dark matter. The authors performed an independent search for the emission line in X-ray spectra of galaxy clusters obtained from the Chandra observatory data archive. They will also discuss future capabilities of the eROSITA observatory in the search for dark matter.

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12:15-12:30 Discussion

12:30-13:30

Lunch

Session 2 13:30-17:00

Particle physics models with X-ray signature

5 talks Show detail Hide detail

Chairs

Professor Chris Reynolds, University of Cambridge, UK

13:30-14:00 keV Neutrinos and Dark Matter

Professor Kevork N Abazajian, University of California, USA

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14:00-14:15 Discussion

14:15-14:45 CELIBE (collisionally excited lines in blustering environments) dark matter

Professor Stefano Profumo, University of California, Santa Cruz, USA

Abstract

Professor Profumo introduces models where the dark matter can up–scatter to a heavier, unstable state whose decay produces quasi–monochromatic photons. He describes the minimal set of field theoretic ingredients necessary to this class of models, and the key resulting phenomenology. He then discusses some novel phenomena that might occur in the early universe such as dark matter kinetic re–coupling.

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14:45-15:00 Discussion

15:00-15:30 Tea

15:30-16:00 X–ray, SZ & dark matter in galaxy clusters

Professor Stefano Ettori, INAF - Astronomical Observatory in Bologna, Italy

Abstract

Galaxy clusters are the nodes of the Cosmic Web, constantly growing through accretion of matter along filaments and via occasional mergers. Their matter content reflects that of the Universe (85% dark matter, with visible baryons distributed among X–ray emitting plasma – about 12% of the total mass – and galaxies –3%). Clusters are thus excellent laboratories for probing the physics of the gravitational collapse of dark matter and baryons, and for studying the non–gravitational physics that affects their baryonic component. Professor Ettori will revise the present constraints on the hot plasma, the dominant baryonic component in galaxy clusters, in the regions approaching the virial radius from his team’s ongoing X–COP project, what are the open questions on the properties of this intracluster medium there, and how we can try to characterize it with the future generation of X–ray telescope like Athena, the second L–class mission of the ESA Cosmic Vision program. In doing this, he will touch most of the topics covered from the workshop, like X–ray searches for dark matter, the Particle physics models with X–ray signature, and the Future capabilities of X–ray satellites.


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16:00-16:15 Discussion

16:15-16:30 Investigating a potential temperature–dependence in the presence of an unidentified emission line in the spectra of XMM–Newton galaxy clusters

Sunayana Bhargava, University of Sussex

Abstract

Sunayana is currently writing a paper following the methodology outlined in Bulbul et al (2014), using data from the XMM Cluster Survey. Her team is hoping to use the highest quality cluster data to search for an unidentified emission line, which could point towards the presence of a sterile neutrino dark matter candidate. In particular, they hope to improve on recent works by investigating a temperature dependence on the prominence of the signal – exploiting the fact that the cluster temperature as a strong correlation with the overall cluster mass. An additional motivation for this is to diminish crowding of the weak signal from astrophysical emission lines, as these lines are less prominent at higher temperatures.

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16:30-16:45 XMM-Newton's impact on fundamental physics

Norbert Schartel, ESA

Abstract

With about 360 refereed papers published each year, XMM–Newton is one of the most successful scientific missions of ESA ever. XMM–Newton observations are pioneering several aspects of fundamental physics, eg 3.5 keV line, searches for axion–like particles, constraining the equation of state (EoS) of cold and dens nuclear matter (in neutron stars), constraining  the (EoS) dark matter and testing general relativity near massive objects. The main focus of the talk will be the discussion of scientific highlight results of these topics based on XMM–Newton observations.

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16:45-17:00 Discussion

17:00-18:15

Poster session

25 October

Session 3 09:00-12:30

Axions and their astrophysical signatures

5 talks Show detail Hide detail

Chairs

Dr Andreas Ringwald, University of Hamburg

09:00-09:30 Simulating axion miniclusters

Dr Javier Redondo, Ludwig Maximilian University of Munich, Germany

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09:30-09:45 Discussion

09:45-10:15 Axions and X–ray polarimetry

Dr Francesca Day, University of Cambridge, UK

Abstract

X–ray telescope observations have already placed world leading bounds on the axion–photon coupling by searching for axion–photon interconversion in the magnetic fields of galaxy clusters. However, current X–ray telescopes are unable to exploit one of the most striking features of this effect: only photons polarised parallel to the background magnetic field mix with axions. This leads to distinctive polarisation signatures from astrophysical sources. The next generation of polarising X–ray telescopes could detect these signatures. Dr Day will discuss the opportunities and difficulties of detecting axions with X–ray polarimetry. In particular, she considers polarimetry observations of bright point sources in or behind galaxy clusters. The polarisation spectrum is affected by both the properties of the source and by any axion–photon interconversion in the cluster's magnetic field. She will outline characteristic features of axion induced polarisation, and discuss promising targets for detecting these features. Dr Day will present projected bounds on the axion–photon coupling from upcoming missions. X–ray polarimetry has the potential to probe unexplored axion parameter space, and will allow us to search for a new kind of axion signal.

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10:15-10:30 Discussion

10:30-11:00 Coffee

11:00-11:30 Radio signatures from conversion of axion–like particles to photons

Professor Guenter Sigl, University of Hamburg, Germany

Abstract

Axion–like particles (ALPs) can convert into photons in several different ways: in an external magnetic field (known as the Primakoff effect), by decay into two photons, or through parametric amplification of incoming radio photons in an oscillating ALP field within a narrow frequency range. For non–relativistic ALPs all three effects can give rise to radio lines, in particular from astrophysical objects with strong magnetic fields or from regions with ALP over–densities, such as ALP stars. Professor Sigl gives a short overview over estimated intensities and prospects for detectability of such radio lines.

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11:30-11:45 Discussion

11:45-12:00 New constraints on ALPs from a deep Chandra grating observation of NGC 1275

Professor Chris Reynolds, University of Cambridge, UK

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12:00-12:15 Terrestrial axion/ALP searches

Dr Andreas Ringwald, University of Hamburg

Abstract

Dr Ringwald will review the different methods to detect axions and ALPs in terrestrial experiments. He will report on their current status and their future prospects.

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12:15-12:30 Discussion

12:30-13:30

Lunch

Session 4 13:30-17:00

Future capabilities of X-ray satellites

5 talks Show detail Hide detail

Chairs

Professor Kathy Romer, University of Sussex, UK

13:30-14:00 Prospects for XRISM – the successor to Hitomi

Dr Poshak Gandhi, University of Southampton, UK

Abstract

XRISM, the X–Ray Imaging and Spectroscopy Mission, is the successor to the JAXA/NASA/ESA mission Hitomi. Scheduled for launch around 2021, XRISM will be the premier high spectral resolution astronomy mission for the next decade, and there are high expectations for it to deliver on the promise of in–orbit X–ray microcalorimetry science demonstrated by Hitomi before its untimely demise. XRISM's primary instrument, Resolve, will closely replicate the performance of Hitomi/SXS, and early laboratory tests have validated expectations. The mission will also carry a large–area soft X–ray imager (Xtend). Dr Gandhi will review the status of the mission, novel science prospects, and ongoing community efforts in high spectral resolution X–ray astronomy.

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14:00-14:15 Discussion

14:15-14:45 Exploring fundamental physics with the Athena X–ray observatory

Dr Jeremy Sanders, Max Planck Institute for Extraterrestrial Physics, Garching, Germany

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14:45-15:00 Discussion

15:00-15:30 Tea

15:30-16:00 X–Ray polarimetry and fundamental physics

Dr Enrico Costa, Istituto di Astrofisica e Planetologia Spaziali, Italy

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16:00-16:15 Discussion

16:15-17:00 Roundtable discussion

X-ray astronomy and fundamental physics

Theo Murphy international scientific meeting organised by Professor Joseph Conlon, Dr David Marsh and Dr Helen Russell.

Kavli Royal Society Centre, Chicheley Hall Newport Pagnell Buckinghamshire MK16 9JJ
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