The ‘Red Radio Ring’: ionized and molecular gas in a starburst/active galactic nucleus at z ∼ 2.55

Abstract

<jats:title>ABSTRACT</jats:title> <jats:p>We report the detection of the far-infrared (FIR) fine-structure line of singly ionized nitrogen, [N ii] 205 $\mu$m , within the peak epoch of galaxy assembly, from a strongly lensed galaxy, hereafter ‘The Red Radio Ring’; the RRR, at z = 2.55. We combine new observations of the ground-state and mid-J transitions of CO (Jup = 1, 5, 8), and the FIR spectral energy distribution (SED), to explore the multiphase interstellar medium (ISM) properties of the RRR. All line profiles suggest that the H ii regions, traced by [N ii] 205 $\mu$m , and the (diffuse and dense) molecular gas, traced by CO, are cospatial when averaged over kpc-sized regions. Using its mid-IR-to-millimetre (mm) SED, we derive a non-negligible dust attenuation of the [N ii] 205 $\mu$m line emission. Assuming a uniform dust screen approximation results a mean molecular gas column density &amp;gt;1024 cm−2, with a molecular gas-to-dust mass ratio of 100. It is clear that dust attenuation corrections should be accounted for when studying FIR fine-structure lines in such systems. The attenuation corrected ratio of $L_{\rm N\,{\small II}205} / L_{\rm IR(8\!-\!1000\, \mu m)} = 2.7 \times 10^{-4}$ is consistent with the dispersion of local and z &amp;gt; 4 SFGs. We find that the lower limit, [N ii] 205 $\mu$m -based star formation rate (SFR) is less than the IR-derived SFR by a factor of 4. Finally, the dust SED, CO line SED, and $L_{\rm N\,{\small II}205}$ line-to-IR luminosity ratio of the RRR is consistent with a starburst-powered ISM.</jats:p>

[N ii] Fine-structure Emission at 122 and 205 μm in a Galaxy at z = 2.6: A Globally Dense Star-forming Interstellar Medium

“…Using our measurements of the line intensities, we find an electron density of n e = 290 +90 −70 cm −3 . This elevated electron density could explain the discrepancy found between the [N II] 205µm and L IR -derived SFRs by Harrington et al (2019), since in that work a low electron densityn e ≈ 30 cm −3 -was assumed.…”

VLA–ALMA Spectroscopic Survey in the Hubble Ultra Deep Field (VLASPECS): Total Cold Gas Masses and CO Line Ratios for z = 2–3 Main-sequence Galaxies

“…All samples cover a similar range in t dep , but the average t dep for the (higher M gas ) high-z samples appear lower. Top right: the r 31 brightness temperature ratio of VLASPECS galaxies (green circles) is similar to that of strongly lensed z∼3 Lyman-break galaxies (red triangles; Riechers et al 2010), z>2 main-sequence galaxies from the PHIBSS survey (gray crosses; Bolatto et al 2015), and z>2 dusty star-forming galaxies (DSFGs; blue squares; compilation from Sharon et al 2016; including data from Danielson et al 2011;Ivison et al 2011;Riechers et al 2011aRiechers et al , 2011bRiechers et al , 2013Thomson et al 2012;Fu et al 2013;Sharon et al 2013Sharon et al , 2015 other DSFGs shown as light gray squares are from Nayyeri et al 2017;Dannerbauer et al 2019;Harrington et al 2019;Leung et al 2019;Sharon et al 2019) and clustered DSFGs (dark gray squares; Bussmann et al 2015;Gómez-Guijarro et al 2019), but ∼2 times higher on average than BzK-selected main-sequence galaxies at z∼1.5 (magenta crosses; Daddi et al 2015). Nearby galaxy samples from the xCOLD GASS survey (Lamperti et al 2020) and two studies of infrared-luminous galaxies (Yao et al 2003;Papadopoulos et al 2012) are shown for comparison.…”

Turbulent Gas in Lensed Planck-selected Starbursts at redshifts 1-3.5

“…We therefore consider them starburst galaxies, without alluding to an assumed SF history. (Harrington et al 2016), (3) (Harrington et al 2019), (4) (Geach et al 2015), ( 5) (Su et al 2017), ( 6) (Geach et al 2018), ( 7) (Rivera et al 2019), ( 8) Kamieneski et al (in prep), ( 9) (Khatri & Gaspari 2016), (10) (Amodeo et al 2018), ( 11) (Cañameras et al 2015), ( 12) (Cañameras et al 2018a), ( 13) (Frye et al 2019), ( 14) (Cañameras et al 2017a), ( 15) (Cañameras et al 2017b), ( 16) (Harrington et al 2018), ( 17) (Cañameras et al 2018c), ( 17) (Bussmann et al 2013)…”

“…Focus measurements were repeated roughly 1.5hr after sunset/sunrise and every 3-4hr to correct for thermal deformations of the primary dish and/or secondary mirror. In the same manner presented in Harrington et al (2019), all scans were reduced using GILDAS package 4 , smoothed to ∼ 50 − 150 km s −1 channel resolution, followed by a visual inspection of a baseline-subtracted spectrum and subsequent averaging of the rms-weighted spectrum. We dropped 5-20% of the scans per line due to unstable baselines or noise spikes, which may strongly depend on the specific tuning setup and weather.…”