Thermal history of the Universe at intermediate redshift: progress with 21cm absorption measurements

Europe/Zurich
4-3-006 - TH Conference Room (CERN)

4-3-006 - TH Conference Room

CERN

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Description

Organisers : Kfir Blum, Guido D'Amico, Andi Hektor, Paolo Panci, Sergey Sibiryakov, Zvonimir Vlah

Registration
Registration Form
Participants
  • Adam Falkowski
  • Alexandre Arbey
  • Andi Hektor
  • Aurel Schneider
  • Elisabetta Majerotto
  • Farbod Hassani
  • Gert Hütsi
  • James Chan
  • Josef Pradler
  • Joshua Ruderman
  • Mason Proffitt
  • maxim pospelov
  • Mona Jalilvand
  • Neal Weiner
  • Paolo Panci
  • Raul Monsalve
  • Rennan Barkana
  • Saleem Zaroubi
  • Sergey Sibiryakov
  • Tejaswi Venumadhav
  • Yu-Dai Tsai
    • 09:30 10:00
      Coffee 30m 4-2-011 - TH common room

      4-2-011 - TH common room

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    • 10:00 10:45
      An Absorption Feature in the Sky-Averaged Radio Spectrum 45m 4-3-006 - TH Conference Room

      4-3-006 - TH Conference Room

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      The EDGES experiment has detected with high S/N an absorption feature in the radio spectrum centered at 78 MHz. This feature is broadly consistent with expectations for the global 21-cm absorption signal from cosmic dawn. However, important aspects of the signal differ from physical predictions. In particular, 1) its absorption amplitude is larger than expected, 2) its profile has surprisingly sharp features, and 3) the center frequency is in tension with predictions from high-z UV galaxy luminosity functions. Understanding the key experimental aspects is crucial when interpreting this challenging measurement. In my talk I will describe the EDGES detection of this absorption feature using our two Low-Band instruments. I will discuss the lab and field calibrations, the verifications tests, the data analysis, and the parameter estimation. I will also summarize recent efforts to constrain traditional 21-cm models using EDGES High-Band data.

      Speaker: Dr Raul Monsalve
    • 11:00 11:45
      Dark matter revealed by the first stars? 45m 4-3-006 - TH Conference Room

      4-3-006 - TH Conference Room

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      The EDGES global 21-cm experiment has detected stronger absorption than expected at cosmic dawn. This absorption can be explained by invoking excess cooling of the cosmic gas induced by an interaction with dark matter. This would have far reaching consequences, including an upper limit on the mass of dark matter particles that conflicts with the expectations for WIMPs. Specific particle physics models are highly constrained, but further observations will decide. In particular, we predict that 21-cm fluctuations at cosmic dawn are likely to be much larger than previously expected, and may exhibit a specific signature of the effect of dark matter.

      Speaker: Prof. Rennan Barkana
    • 12:00 15:00
      Lunch 3h R1 ()

      R1

    • 15:00 15:30
      Coffee 30m 4-2-011 - TH common room

      4-2-011 - TH common room

      CERN

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    • 15:30 16:00
      Bounds on Dark Matter annihilations from 21 cm data 30m 4-3-006 - TH Conference Room

      4-3-006 - TH Conference Room

      CERN

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      The observation of an absorption feature in the 21 cm spectrum at redshift z ≈ 17 implies bounds on Dark Matter annihilations for a broad range of masses, given that significant heating of the intergalactic medium would have erased such feature. The resulting bounds on the DM annihilation cross sections are comparable to the strongest ones from all other observables.

      Speaker: Dr Guido D'Amico
    • 16:15 16:45
      Speculations on the EDGES 21cm anomaly 30m 4-3-006 - TH Conference Room

      4-3-006 - TH Conference Room

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      Possible attempts to resolve the EDGES anomaly rely on cooling cosmic hydrogen gas via interactions between dark and visible sector or modifying the soft photon background beyond CMB. The first solution is in tension with cosmological dark matter probes once simple dark sector models are considered. The second solution can be realised as soft photon emission from dark sector. However, the proposed mechanisms to produce soft photons need rather complex physics, e.g. axion miniclusters. The talk is based on our recent paper 1803.03245.

      Speaker: Dr Andi Hektor
    • 17:00 17:30
      Constraints on energy injection from 21-cm measurements: primordial black holes, axion-like particles and excited dark matter 30m 4-3-006 - TH Conference Room

      4-3-006 - TH Conference Room

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      I will review our recent papers 1803.09697 and 1805.09319

      Speaker: Dr Gert Hutsi
    • 18:00 20:00
      Cocktail R1 ()

      R1

  • Wednesday, 27 June
    • 09:30 10:00
      Coffee 30m 4-2-011 - TH common room

      4-2-011 - TH common room

      CERN

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    • 10:00 10:45
      21 cm Cosmology: The status of the current redshifted 21 cm experiments 45m 4-3-006 - TH Conference Room

      4-3-006 - TH Conference Room

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      In the last decade a large effort has been dedicated to detect one of the last phase transitions in the Universe called the Epoch of Reionization and its preceding epoch know as the Cosmic Dawn, specially with redshifted 21 cm probes. I will review the current status of the various constraints that we currently have on reionization. I will also show the current results from the few redshifted 21 cm operating telescopes, a special
      attention will be paid to the recent results obtained with EDGES and the LOFAR telescope. A discussion about the future of this effort will conclude my talk.

      Speaker: Dr Saleem Zaroubi
    • 11:00 11:45
      Probing non-cold dark matter models with the global 21-cm signal 45m 4-3-006 - TH Conference Room

      4-3-006 - TH Conference Room

      CERN

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      The global 21-cm absorption signal induced by the first stars provides unique insights into structure formation at very high redshifts. I will show how the timing of such a signal can be used to obtain unprecedented constraints on the nature of dark matter.

      Speaker: Dr Aurel Schneider
    • 12:00 15:00
      Lunch 3h R1 ()

      R1

    • 15:00 15:30
      Coffee 30m 4-2-011 - TH common room

      4-2-011 - TH common room

      CERN

      40
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    • 15:30 16:00
      Stronger 21cm absorption from charge sequestration 30m 4-3-006 - TH Conference Room

      4-3-006 - TH Conference Room

      CERN

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      The unexpectedly strong 21cm absorption signal detected by the EDGES experiment suggests that the baryonic gas at the end of the dark ages was colder than predicted in the standard scenario. We discuss a mechanism to lower the baryon temperature after recombination. We introduce a stable, negatively-charged particle with a significant cosmological abundance, such that the universe remains charge-neutral but the electron and proton numbers are no longer equal. The deficit of electrons after recombination results in an earlier decoupling of the baryon and CMB temperatures, and thus in a colder gas at the cosmic dawn.

      Speaker: Dr Adam Falkowski
    • 16:15 16:45
      The 21-cm signal and the high redshift IGM 30m 4-3-006 - TH Conference Room

      4-3-006 - TH Conference Room

      CERN

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      The recent results of the EDGES experiment motivate us to take a closer look at the standard calculation of the 21cm signal. I will give a short introduction to the physics of the 21cm line, and how its brightness temperature depends on the physical conditions in the high redshift IGM, namely the local gas temperature and the flux of Lyman-alpha photons. I will then describe recent work that shows how the CMB heats the gas in the presence of the same Lyman-alpha photons that are needed to produce the signal. Time permitting, I will also touch on the implications of the shape of the EDGES signal for the fluctuations in the 21cm background from the same cosmological period.

      Speaker: Dr Tejaswi Venumadhav
    • 17:00 17:30
      21 cm physics as a probe of (a case for?) dark radiation. 30m 4-3-006 - TH Conference Room

      4-3-006 - TH Conference Room

      CERN

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      Numerous quanta of soft dark radiation ( e.g. more abundant than CMB photons) could be created in the early Universe by means of various non-thermal processes. The dark radiation
      can be resonantly converted to the "normal" photons, creating over-population of Rayleigh-Jeans photons, increasing the contrast of the 21 cm absorption feature. We construct specific classes of models to that effect, where the dark radiation in the form of the dark photons is sourced by the decay of sub-eV dark matter particles. We show that such models are perfectly consistent with all astrophysical, cosmological and terrestrial data, and 21 cm physics provides the leading constraint on it. In a more speculative vein, the strength of the EDGES signal can also be explained suing such a setup.

      Speaker: Dr Maxim Pospelov
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