{
  "$schema": "./item.schema.json",
  "id": "cmb-spectrum-distortions",
  "type": "publication",
  "cvs": [
    "np",
    "2page"
  ],
  "featured": true,
  "date": {
    "start": "2024-03"
  },
  "title": "Angular Correlations of Cosmic Microwave Background Spectrum Distortions from Photon Diffusion",
  "shortTitle": "CMB Spectrum Distortions from Photon Diffusion",
  "nickTitle": "CMB Spectrum Distortions",
  "status": "published",
  "entryType": "article",
  "authors": [
    {
      "family": "Starkman",
      "given": "Nathaniel",
      "me": true,
      "orcid": "0000-0003-3954-3291"
    },
    {
      "family": "Starkman",
      "given": "Glenn",
      "orcid": "0000-0002-5053-1542",
      "affiliation": "Physics Department/CERCA/ISO Case Western Reserve University Cleveland , Ohio 44106-7079 , USA"
    },
    {
      "family": "Kosowsky",
      "given": "Arthur",
      "orcid": "0000-0002-3734-331X",
      "affiliation": "Department of Physics and Astronomy, University of Pittsburgh , Pittsburgh, PA 15260 , USA"
    }
  ],
  "venue": {
    "journal": "Monthly Notices of the Royal Astronomical Society",
    "volume": "529",
    "pages": "2274"
  },
  "doi": "10.1093/mnras/stae665",
  "arxiv": "2310.01578",
  "primaryClass": "astro-ph.CO",
  "links": [
    {
      "rel": "paper",
      "url": "https://academic.oup.com/mnras/article/529/3/2274/7630233"
    },
    {
      "rel": "repo",
      "url": "https://github.com/nstarman/Temperature-Diffusion-Spectral-Distortion-Paper"
    },
    {
      "rel": "data",
      "url": "https://zenodo.org/record/8400583"
    }
  ],
  "tags": [
    "cmb",
    "cosmology"
  ],
  "citekey": "Starkman+:2024:cmb-spectral-distortions",
  "abstract": "During cosmic recombination, charged particles bind into neutral atoms and the mean free path of photons rapidly increases, resulting in the familiar diffusion damping of primordial radiation temperature variations. An additional effect is a small photon spectrum distortion, because photons arriving from a particular sky direction were originally in thermal equilibrium at various spatial locations with different temperatures; the combination of these different blackbody temperature distributions results in a spectrum with a Compton y-distortion. Using the approximation that photons had zero mean free path prior to their second-to-last scattering, we derive an expression for the resulting y-distortion, and compute the angular correlation function of the diffusion y-distortion and its cross-correlation with the square of the photon temperature fluctuation. Detection of the cross-correlation is within reach of existing arcminute-resolution microwave background experiments such as the Atacama Cosmology Telescope and the South Pole Telescope.",
  "highlight": {
    "topic": "cmb",
    "image": "highlights/cmb-spectrum-distortions.webp",
    "alt": "Angular power spectra of the squared temperature fluctuations (blue), their cross-correlation with the diffusion y-distortion (purple, scaled by 50), and the y-distortion’s own autocorrelation (red, scaled by 1000). The blue and purple curves carry acoustic oscillations.",
    "description": "As the universe became transparent, the photons reaching us from any one direction last scattered off regions at slightly different temperatures. Blending those blackbodies leaves a small Compton y-distortion in the CMB spectrum. Its cross-correlation with the squared temperature fluctuations should already be detectable by ACT and SPT, at a forecast signal-to-noise of about 12, and CMB-S4 could turn it into a new cosmological probe."
  }
}