{
  "id": "2408.13572",
  "version": "v1",
  "published": "2024-08-24T12:53:21.000Z",
  "updated": "2024-08-24T12:53:21.000Z",
  "title": "X-ray observations of Blueberry galaxies",
  "authors": [
    "B. Adamcová",
    "J. Svoboda",
    "E. Kyritsis",
    "K. Kouroumpatzakis",
    "A. Zezas",
    "P. G. Boorman",
    "A. Borkar",
    "M. Bílek",
    "M. Clavel",
    "P. -O. Petrucci"
  ],
  "comment": "10 pages, 4 + 1 (appendix) figures, accepted for publication in Astronomy & Astrophysics on 9.8.2024",
  "categories": [
    "astro-ph.GA"
  ],
  "abstract": "Compact star-forming galaxies were dominant galaxy types in the early Universe. Blueberry galaxies (BBs) represent their local analogues being very compact and having intensive star formation. Motivated by high X-ray emission recently found in other analogical dwarf galaxies, called Green Peas, we probe into the X-ray properties of BBs to determine if their X-ray emission is consistent with the empirical laws for star-forming galaxies. We performed the first X-ray observations of a small sample of BBs with the XMM-Newton satellite. Spectral analysis for detected sources and upper limits measured via Bayesian-based analysis for very low-count measurements were used to determine the X-ray properties of our galaxy sample. Clear detection was obtained only for 2 sources, with one source exhibiting an enhanced X-ray luminosity to the scaling relations. For the remaining 5 sources, only an upper limit was constrained, suggesting BBs to be rather underluminous as a whole. Our analysis shows that the large scatter cannot be easily explained by the stochasticity effects. While the bright source is above and inconsistent at almost the 99% confidence level, the upper limits of the two sources are below the expected distribution. These results indicate that the empirical relations between the star formation rate, metallicity, and X-ray luminosity might not hold for BBs with uniquely high specific star formation rates. One possible explanation could be that the BBs may not be old enough to have a significant X-ray binary population. The high luminosity of the only bright source can be then caused by an additional X-ray source, such as a hidden active galactic nucleus or more extreme ultraluminous X-ray sources.",
  "revisions": [
    {
      "version": "v1",
      "updated": "2024-08-24T12:53:21.000Z"
    }
  ],
  "analyses": {
    "keywords": [
      "blueberry galaxies",
      "x-ray observations",
      "upper limit",
      "high specific star formation rates",
      "x-ray source"
    ],
    "note": {
      "typesetting": "TeX",
      "pages": 10,
      "language": "en",
      "license": "arXiv",
      "status": "editable"
    }
  }
}