Imaging the cold molecular gas in SDSS J1148 + 5251 at z = 6.4

Irina I. Stefan, Chris L. Carilli, Jeff Wagg, Fabian Walter, Dominik A. Riechers, Frank Bertoldi, David A. Green, Xiaohui Fan, Karl Menten, Ran Wang

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17 Scopus citations


We present Karl G. Jansky Very Large Array (VLA) observations of the CO (J = 2→1) line emission towards the z = 6.419 quasar SDSS J114816.64 + 525150.3 (J1148 + 5251). The molecular gas is found to be marginally resolved with amajor axis of 0.9 arcsec (consistent with previous size measurements of the CO (J = 7→6) emission). We observe tentative evidence for extended line emission towards the south-west on a scale of ~1.4 arcsec, but this is only detected at 3.3σ significance and should be confirmed. The position of the molecular emission region is in excellent agreement with previous detections of low-frequency radio continuum emission as well as [C II] line and thermal dust continuum emission. These CO (J = 2→1) observations provide an anchor for the low-excitation part of the molecular line spectral energy distribution. We find no evidence for extended low-excitation component, neither in the spectral line energy distribution nor the image. We fit a single kinetic gas temperature model of 50 K. We revisit the gas and dynamical masses in light of this new detection of a low-order transition of CO, and confirm previous findings that there is no extended reservoir of cold molecular gas in J1148 + 5251, and that the source departs substantially from the low-z relationship between black hole mass and bulge mass. Hence, the characteristics of J1148 + 5251 at z = 6.419 are very similar to z ~ 2 quasars, in the lack of a diffuse cold gas reservoir and kpc-size compactness of the star-forming region.

Original languageEnglish (US)
Pages (from-to)1713-1718
Number of pages6
JournalMonthly Notices of the Royal Astronomical Society
Issue number2
StatePublished - May 1 2015


  • Cosmology: observations
  • Galaxies: active
  • Galaxies: formation
  • Galaxies: high-redshift
  • Galaxies: individual: SDSS J114816.64 + 525150.3
  • Radio lines: galaxies

ASJC Scopus subject areas

  • Space and Planetary Science
  • Astronomy and Astrophysics

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    Stefan, I. I., Carilli, C. L., Wagg, J., Walter, F., Riechers, D. A., Bertoldi, F., Green, D. A., Fan, X., Menten, K., & Wang, R. (2015). Imaging the cold molecular gas in SDSS J1148 + 5251 at z = 6.4. Monthly Notices of the Royal Astronomical Society, 451(2), 1713-1718.