First Detection of the [O i] 63 μm Emission from a Redshift 6 Dusty Galaxy

Abstract

We report a ground-based detection of the [O I] 63-µm line in a z = 6.027 gravitationally lensed dusty star-forming galaxy (DSFG) G09.83808 using the APEX SEPIA 660 receiver, the first unambiguous detection of the [O I] 63 line beyond redshift 3, and the first obtained from the ground. The [O I] 63 line is robustly detected at 22±5 Jy km s −1 , corresponding to an intrinsic (de-lensed) luminosity of (5.4 ± 1.3) × 10 9 L . With the [O I] 63 /[C II] luminosity ratio of 4, the [O I] 63 line is the main coolant of the neutral gas in this galaxy, in agreement with model predictions. The high [O I] 63 luminosity compensates for the pronounced [C II] deficit ([C II]/FIR 4 × 10 −4 ). Using photon-dominated region models, we derive a source-averaged gas density n = 10 4.0 cm −3 , and far-UV field strength G = 10 4 G 0 , comparable to the z = 2 − 4 DSFG population. If G09.83808 represents a typical high-redshift DSFG, the [O I] 63 line from z = 6 non-lensed DSFGs should be routinely detectable in ALMA Band 9 observations with ∼15 min on-source, opening a new window to study the properties of the earliest DSFGs.

Observations of [OI]63 μm line emission in main-sequence galaxies at z ∼ 1.5

“…A spectral stacking analysis of the data from the three non-detections reveals a significant signal, implying L [OI]63 µm = (1.1 ± 0.2) × 10 9 L . The line-to-total infrared luminosity ratio in BzK-21000 is similar to that of a dusty, z ∼ 6 galaxy (Rybak et al 2020), but lower than that typically observed in massive submm galaxies at z ∼ 1 − 3. Combined with PDR models, the relative strengths of the [OI]63µm and CO J =2-1 lines compared to the infrared luminosity imply a UV field intensity, G ∼ 320G 0 , and a gas density, n ∼ 1800 cm −3 .…”

“…The Herschel -PACS spectrometer enabled observations of the [OI]63 µm line emission in high-redshift, submm-selected starburst galaxies (Sturm et al 2010;Coppin et al 2012;Brisbin et al 2015;Wardlow et al 2017;Zhang et al 2018), which confirm the FIR line deficit observed in nearby luminous and ultraluminous galaxies. Most recently, Rybak et al (2020) have made a ground-based detection of [OI]63 µm in G09.83808, a dusty z∼6 galaxy, and from these data they infer a gas density, n = 10 4 cm −3 , and FUV field strength, G= 10 4 G 0 1 . To date, few observations of this line have been presented for lower redshift, main sequence star-forming objects like the BzK galaxies.…”

“…2017), compared to those galaxies which have been detected at high-redshift. The stars show the luminosity ratios of lensed and unlensed submm galaxies at z ∼ 1 − 3(Coppin et al 2012;Brisbin et al 2015;Zhang et al 2018), whileRybak et al (2020) detect line emission in G09.83808 at z ∼ 6 using the APEX telescope. Where applicable, the luminosities have been corrected for gravitational lensing.…”

The nature of high [O iii]88 μ m/[C ii]158 μm galaxies in the epoch of reionization: Low carbon abundance and a top-heavy IMF?

“…Nev ertheless, there hav e been many situations where simulations have agreed on emission-line properties of high-redshift galaxies and provide deep insights into or predictions of the early Univ erse. F or e xample, the necessary but insufficient condition that LyC leakers have high O32 (Barrow et al 2020 ;Katz et al 2020b ) as confirmed at z ∼ 2-3 (Nakajima et al 2020 ) or the strong [O I ] 63 μm (hereafter [O I ]) emission line (Olsen et al 2017 ;Katz et al 2019b ), that was recently observed at z > 6 (Rybak et al 2020 ).…”

Galaxy evolution through infrared and submillimeter spectroscopy: Measuring star formation and black hole accretion with JWST and ALMA

“…This value is unrealistic for a ground-based telescope, such as ALMA, and in principle could be achieved only by summing up the results of various observing runs of few hours each. As a matter of fact, the only detection of the [OI]63µm line available so far for a high-redshift galaxy is the one reported by Rybak et al (2020) for a strongly gravitationally lensed galaxy (magnification µ FIR 9) obtained with the APEX 12m telescope (Güsten et al, 2006), and the Swedish ESO PI (SEPIA) Band 9 receiver (Belitsky et al, 2018) 2020). We note that, while all reported detections have σ=5 or higher, the integration times can reach values of the order of 7.5 hrs.…”