ALMA [N ii] 205 μm imaging spectroscopy of the interacting galaxy system BRI 1202-0725 at redshift 4.7

Journal article

We present the results from Atacama Large Millimeter/submillimeter Array imaging in the [N ii] 205μm fine-structure line (hereafter [N ii] ) and the underlying continuum of BRI 1202-0725, an interacting galaxy system at z = 4.7, consisting of a quasi-stellar object (QSO), a submillimeter galaxy (SMG), and two Ly emitters, all within ∼25 kpc of the QSO. We detect the QSO and SMG in both [N ii] and continuum. At the ∼1″ (or 6.6 kpc) resolution, both the QSO and SMG are resolved in [N ii] , with the de-convolved major axes of ∼9 and ∼14 kpc, respectively. In contrast, their continuum emissions are much more compact and unresolved even at an enhanced resolution of ∼0.″7. The ratio of the [N ii] flux to the existing CO(7-6) flux is used to constrain the dust temperature (T dust ) for a more accurate determination of the FIR luminosity LFIR . Our best estimated T dust equals 43 (±2) K for both galaxies (assuming an emissivity index β = 1.8). The resulting LCO(7-6) /L FIR ratios are statistically consistent with that of local luminous infrared galaxies, confirming that LCO(7-6) traces the star formation (SF) rate (SFR) in these galaxies. We estimate that the ongoing SF of the QSO (SMG) has an SFR of 5.1 (6.9) × 10^3 M⊙ yr^-1 (±30%) assuming Chabrier initial mass function, takes place within a diameter (at half maximum) of 1.3 (1.5) kpc, and will consume the existing 5 (5) × 10^11 M⊙ of molecular gas in 10 (7) × 10 7 years.

Authors: Lu, N; Zhao, Y; Díaz-Santos, T; Xu, C; Charmandaris, V

• Publication status: Published
• Peer review status: Peer reviewed
• Publisher: Institute of Physics
• Journal: Astrophysical Journal Letters
• Volume: 842
• Issue: 2
• Pages: L16
• Publication date: 2017-06-01
• Acceptance date: 2017-06-07
• DOI: 10.3847/2041-8213/aa77fc
• EISSN: 2041-8213
• ISSN: 2041-8205
• Keywords: ISM: molecules; galaxies: ISM; infrared: galaxies; galaxies: star formation; submillimeter: galaxies; galaxies: active