ALMA multiline survey of the ISM in two quasar host–companion galaxy pairs atz> 6

Abstract

We present a multiline survey of the interstellar medium (ISM) in two z > 6 quasar host galaxies, PJ231−20 (z = 6.59) and PJ308−21 (z = 6.23), and their two companion galaxies. Observations were carried out using the Atacama Large (sub-)Millimeter Array (ALMA). We targeted 11 transitions including atomic fine-structure lines (FSLs) and molecular lines: [NII]205 μm, [CI]369 μm, CO (Jup = 7, 10, 15, 16), H2O 312 − 221, 321 − 312, 303 − 212, and the OH163 μm doublet. The underlying far-infrared (FIR) continuum samples the Rayleigh-Jeans tail of the respective dust emission. By combining this information with our earlier ALMA [CII]158 μm observations, we explored the effects of star formation and black hole feedback on the ISM of the galaxies using the CLOUDY radiative transfer models. We estimated dust masses, spectral indexes, IR luminosities, and star-formation rates from the FIR continuum. The analysis of the FSLs indicates that the [CII]158 μm and [CI]369 μm emission arises predominantly from the neutral medium in photodissociation regions (PDRs). We find that line deficits agree with those of local luminous IR galaxies. The CO spectral line energy distributions (SLEDs) reveal significant high-J CO excitation in both quasar hosts. Our CO SLED modeling of the quasar PJ231−20 shows that PDRs dominate the molecular mass and CO luminosities for Jup ≤ 7, while the Jup ≥ 10 CO emission is likely driven by X-ray dissociation regions produced by the active galactic nucleus (AGN) at the very center of the quasar host. The Jup > 10 lines are undetected in the other galaxies in our study. The H2O 321 − 312 line detection in the same quasar places this object on the LH2O − LTIR relation found for low-z sources, thus suggesting that this water vapor transition is predominantly excited by IR pumping. Models of the H2O SLED and of the H2O-to-OH163 μm ratio point to PDR contributions with high volume and column density (nH ∼ 0.8 × 105 cm−3, NH = 1024 cm−2) in an intense radiation field. Our analysis suggests a less highly excited medium in the companion galaxies. However, the current data do not allow us to definitively rule out an AGN in these sources, as suggested by previous studies of the same objects. This work demonstrates the power of multiline studies of FIR diagnostics in order to dissect the physical conditions in the first massive galaxies emerging from cosmic dawn.

Molecular gas in z~6 quasar host galaxies

“…In Fig. 7, we compare the observed [C ii]/[C i] and CO(7-6)/IR luminosity ratios in individual sources from our sample with other high-redshift quasars and SMGs (from Weiß et al 2003;Riechers et al 2009;Bradford et al 2009;Ivison et al 2010;Cox et al 2011;De Breuck et al 2011;Danielson et al 2011;Wagg et al 2012;Salomé et al 2012;Walter et al 2012;Weiß et al 2013;Riechers et al 2013;Rawle et al 2014;Leipski et al 2014;Decarli et al 2014;Venemans et al 2017a;Zhao et al 2020;Pensabene et al 2021) as well local galaxies (based on the compilation in Rosenberg et al 2015) and with the predictions from the models presented in Fig. 6.…”

“…This assumption allows us to directly compare our observations with the line and continuum luminosity predictions of Photo-Dissociation Regions (PDRs) and X-ray Dominated Regions (XDRs). The models are based on the analysis presented in Pensabene et al (2021) and briefly summarized here. We use the CLOUDY radiative-transfer code (version c.17.01;Ferland et al 2017) to predict the line emission of a single plane-parallel semi-infinite cloud impinged by a radiation field in both the PDR and XDR regimes.…”

“…6). We assume that all the line emission arises from the neutral or molecular gas phase, in particular the contribution of Hii regions to the [C ii] emission is neglected (see, e.g., Díaz-Santos et al 2017;Pensabene et al 2021). The relative strength of all of the targeted lines is sensitive to the gas density, as well as to the intensity and hardness of the incident radiation field.…”

Organic Molecules in Interstellar Space: Latest Advances

“…The Planck/HIFI, Hershell/HerMES, H-ATLAS and South Pole Telescope far-infrared/sub-millimetre surveys show that a fair fraction (several percent) of the high-z sub-millimetre-bright galaxies are magnified by gravitational lensing (Ade et al, 2016;Spilker et al, 2016, as well as references therein; Hodge and da Cunha, 2020). Nonetheless, and except for the relatively strong CO and H 2 O lines (Yang et al, 2016;Pensabene et al, 2021), rare are the cases where the magnification is large enough to allow a clear detection of molecular lines from the intervening galaxies, or from the background quasar itself. Besides the detections in a handful of lensed quasars (e.g., APM08279+5255) of a few lines of HCN, HNC and HCO + (García-Burillo et al, 2006;Guélin et al, 2007), one has essentially to rely on source stacking methods to barely detect more molecular species (Spilker et al, 2014;Reuter et al, 2020).…”

Multi-Phase ISM in the z = 5.7 Hyperluminous Starburst SPT0346-52

“…Grey dots are galaxy-integrated values from SHINING (Herrera-Camus et al 2018) and black are from GOALS (Díaz-Santos et al 2017;Lutz et al 2016;Lu et al 2017). Tan dots are a selection of high-z line detections: J1342+0928 (Venemans et al 2017;Bañados et al 2019;Novak et al 2019), SPT0311-58 (Marrone et al 2018), PJ231-20 (Pensabene et al 2021), HFLS3 (Riechers 2013), PJ308-21 (Decarli et al 2019;Pensabene et al 2021), G09.83808 (Zavala et al 2018;Rybak et al 2020), J2310+1855 (Shao et al 2019;Li et al 2020), BR1202-0725 (Decarli et al 2014;Lu et al 2017;Lee et al 2019Lee et al , 2021, SMMJ02399 (Weiß et al 2007;Ivison et al 2010;Ferkinhoff et al 2011), Cloverleaf (Weiß et al 2003;Ferkinhoff et al 2011), SDP.11 (Lamarche et al 2018, and MIPS J1428 (Iono et al 2006;Hailey-Dunsheath et al 2010Sturm et al 2010). In the spatially resolved SHINING galaxies, a sample of nearby galaxies that includes star-forming galaxies, AGN host galaxies, and LIRGs, Herrera-Camus et al (2018) found the trend of decreasing line/L FIR strongest for singly ionized lines like [NII]122µm and [CII]158µm and weakest for neutral [OI]146µm and [OI]63µm.…”