Coalas

Abstract

We report a detailed CO(1−0) survey of a galaxy protocluster field at z = 2.16, based on 475 h of observations with the Australia Telescope Compact Array. We constructed a large mosaic of 13 individual pointings, covering an area of 21 arcmin2 and ±6500 km s−1 range in velocity. We obtained a robust sample of 46 CO(1−0) detections spanning z = 2.09 − 2.22, constituting the largest sample of molecular gas measurements in protoclusters to date. The CO emitters show an overdensity at z = 2.12 − 2.21, suggesting a galaxy super-protocluster or a protocluster connected to large-scale filaments of ∼120 cMpc in size. We find that 90% of CO emitters have distances >0.′5−4′ to the center galaxy, indicating that small area surveys would miss the majority of gas reservoirs in similar structures. Half of the CO emitters have velocities larger than escape velocities, which appears gravitationally unbound to the cluster core. These unbound sources are barely found within the R200 radius around the center, which is consistent with a picture in which the cluster core is collapsed while outer regions are still in formation. Compared to other protoclusters, this structure contains a relatively higher number of CO emitters with relatively narrow line widths and high luminosities, indicating galaxy mergers. We used these CO emitters to place the first constraint on the CO luminosity function and molecular gas density in an overdense environment. The amplitude of the CO luminosity function is 1.6 ± 0.5 orders of magnitude higher than that observed for field galaxy samples at z ∼ 2, and one order of magnitude higher than predictions for galaxy protoclusters from semi-analytical SHARK models. We derive a high molecular gas density of 0.6 − 1.3 × 109 M⊙ cMpc−3 for this structure, which is consistent with predictions for cold gas density of massive structures from hydro-dynamical DIANOGA simulations.

The 700 ks Chandra Spiderweb Field I: evidence for widespread nuclear activity in the Protocluster

“…Given the mass scale and the distribution of sources in the sky, the virialized, single-halo hypothesis is clearly unrealistic. In addition, we notice that excluding the new spectroscopic sources identified by Jin et al (2021) with the CO(1-0) line, the velocity dispersion drops to σ v = 980±100 km/s (that would correspond to a temperature of ∼ 6 keV for a virialized halo). As already shown in Jin et al (2021), this points out that the CO sources show a different dynamical behavior, and are probably distributed along a large-scale filament or a galaxy superprotocluster.…”

“…In addition, we notice that excluding the new spectroscopic sources identified by Jin et al (2021) with the CO(1-0) line, the velocity dispersion drops to σ v = 980±100 km/s (that would correspond to a temperature of ∼ 6 keV for a virialized halo). As already shown in Jin et al (2021), this points out that the CO sources show a different dynamical behavior, and are probably distributed along a large-scale filament or a galaxy superprotocluster. In addition, half of the CO emitters have measured velocities larger than the escape velocities of any realistic virialized halo hosting the Spiderweb Galaxy, suggesting that the outer regions traced by the CO sources are still far from being accreted onto the main halo.…”

“…We note that most of the sources without a K S counterpart are from the COALAS survey. In fact, from Table 3 of Jin et al (2021), we notice that half of them are not detected in the K S band, while 90% of them are detected in the I band, and therefore these sources should correspond to relatively low-mass galaxies. The distribution of M * in the protocluster is shown in Figure 21.…”

“…For the sake of clarity, we refer to the radio galaxy and its immediate surroundings as the Spiderweb Galaxy, or J1140-2629, while "Spiderweb Complex" indicates the largescale structure potentially associated to the radio galaxy in a broad redshift range (2.0 < z < 2.3). The term "protocluster" is instead used to include only the galaxies in the narrower red-shift range 2.11 < z < 2.20 (see also Jin et al 2021), assuming that all the protocluster members will end up in a massive (∼few times 10 14 M ) cluster today. Throughout this paper, we adopt the seven-year WMAP cosmology with Ω Λ = 0.73, Ω m = 0.27, and H 0 = 70.4 km s −1 Mpc −1 (Komatsu et al 2011).…”

X-ray Emission and Radio Emission from the Jets and Lobes of the Spiderweb Radio Galaxy

“…The protocluster shows a dense distribution of galaxies extending to radii > 100 kpc, as well as a Lyα halo on a similar scale, with a major axis along the jet axis (Miley et al 2006). Many of these galaxies have been detected in CO and thermal emission from warm dust, including the host galaxy of the radio source itself (Gullberg et al 2016;Dannerbauer et al 2014;Jin et al 2021). There also appears to be a diffuse CO emitting component on ∼ 100 kpc scale (Emonts et al 2016).…”