An ALMA Multiline Survey of the Interstellar Medium of the Redshift 7.5 Quasar Host Galaxy J1342+0928

Abstract

We use Atacama Large Millimeter Array observations of the host galaxy of the quasar ULAS J1342+0928 at z = 7.54, to study the dust continuum and far-infrared lines emitted from its interstellar medium (ISM). The Rayleigh-Jeans tail of the dust continuum is well sampled with eight different spectral setups, and from a modified blackbody fit we obtain an emissivity coefficient of beta = 1.85 +/- 0.3. Assuming a standard dust temperature of 47 K we derive a dust mass of M-dust = 0.35 x 10(8) M circle dot and a star formation rate of 150 +/- 30 M circle dot yr(-1). We have >4 sigma detections of the [C II](158) (mu m), [O III](88 mu m), and [N II](205) (mu m) atomic fine structure lines and limits on the [C I](369) mu m, [O I](146) mu m, and [N II](205) (mu m) emission. We also report multiple limits of CO rotational lines with J up >= 7, as well as a tentative 3.3 sigma detection of the stack of four CO lines (J(up) = 11, 10, 8, and 7). We find line deficits that are in agreement with local ultra-luminous infrared galaxies. Comparison of the [N II](205) (mu m) and [C II](158) (mu m) lines indicates that the [C II](158) (mu m) emission arises predominantly from the neutral medium, and we estimate that the photodisassociation regions in J1342+0928 have densities less than or similar to 5 x 10(4) cm(-3). The data suggest that similar to 16% of hydrogen is in ionized form and that the H II regions have high electron densities of n(e) > 180 cm(-3). Our observations favor a low gas-to-dust ratio of <100, and a metallicity of the ISM comparable to the solar value. All the measurements presented here suggest that the host galaxy of J1342+0928 is highly enriched in metal and dust, despite being observed just 680 Myr after the big bang.