Journal Article

Imaging the cold molecular gas in SDSS J<i>1148 + 5251</i> at <i>z = 6.4</i>

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

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 451, issue 2, pages 1713-1718
ISSN: 0035-8711
Published online June 2015 | e-ISSN: 1365-2966 | DOI:
Imaging the cold molecular gas in SDSS J1148 + 5251 at z = 6.4

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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 a major 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.

Keywords: galaxies: active; galaxies: formation; galaxies: high-redshift; galaxies: individual: SDSS J114816.64 + 525150.3; cosmology: observations; radio lines: galaxies

Journal Article.  3445 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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