Expansive Intergalactic Stream Of Cold Cosmic Carbon Feeding A Massive Galaxy

By Keith Cowing
Press Release
April 1, 2023
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Expansive Intergalactic Stream Of Cold Cosmic Carbon Feeding A Massive Galaxy
All [C I] emission around 4C 41.17. (A) The blue and cyan [C I] contours are the same as Figure 1A; the green (marked as radio galaxy `RG’) and red (marked as South-East `SE’) contours show additional velocity channels. The background image is the same as Fig. S1A. The [C I] emission is integrated across the velocity ranges indicated in the legend. Blue and red contour levels start at 2σ and increase by 1σ, with σ = 0.011 Jy bm-1 × km s-1. The green contours start at 3σ and increase by 1σ, with σ = 0.015 Jy bm-1 × km s-1. No correction for primary beam (PB) response was applied. The gray contours show the Lyα halo (background image in Fig. 1A). Two red galaxies in the HST imaging at the base of the stream are probably dusty star-forming galaxies (DSFGs) (27), marked with arrows. The dotted gray lines indicate two prominent dark lanes (DL) previously identified in the Lyα imaging (17 ,24). Other symbols and labels are the same as Figure 1. (B-H) Spectra of [C I] extracted at the locations of the white crosses in panel A, which capture regions NW1, NW2, NW3, and NW4 of the stream, as well as the radio galaxy (RG), the region West of the radio galaxy that connects to the stream (W), and the region South-East of the radio galaxy (SE). The spectra are Hanning smoothed to a velocity resolution of 29 km s-1 and values have been corrected for the PB response to give flux densities. The colored shaded regions correspond to the velocity ranges in the legend. — Science

Radio telescope observations have revealed a cold stream of intergalactic atomic carbon gas feeding star formation in a massive radio galaxy in the young Universe.

The findings provide observational evidence supporting theoretical cosmological models and offer new insights into the origins of the cosmic materials that enable galaxy and star formation. Galaxies grow and evolve by accreting gas, either in mergers with other galaxies or from streams of cold molecular gas that thread through the intergalactic medium. Simulations suggest that this latter type of accretion, also known as cold stream accretion, may be a key mechanism driving the observed high star formation rates and rapid development of galaxies early in the history of the Universe.

However, the physics underlying cold accretion streams are not well understood and, due to their elusive nature, it has been challenging to observe and confirm the existence of such streams feeding massive galaxies. Using the Atacama Large Millimeter/submillimeter Array (ALMA), Bjorn Emonts and colleagues mapped the atomic carbon gas surrounding the galaxy 4C 41.17 – a massive radio galaxy in the early Universe at redshift 3.8.

To maximize the radio telescopes surface brightness sensitivity, Emonts et al. used ALMA’s most compact and low-resolution configuration, which likely helped them detect a cold molecular stream where past studies haven’t, the authors say. The submillimeter observations revealed a narrow stream of cold gas extending at least 100 kiloparsecs (~326,000 lightyears) outside the galaxy and into the intergalactic medium – a distance several times larger than the galaxy it appears to be feeding. According to the authors, the observations are consistent with cold gas streams predicted by cosmological models, and the mass of the cold atomic gas being funneled into the massive galaxy could fuel star formation for more than 500 million years.

“Having observations that match well to previous predictions from simulations has been long in the making,” writes Caitlin Casey in a related Perspective. “Further observations of cold streams that span a broad range of galaxies are needed to determine the processes that feed gas into galaxies.”

A cosmic stream of atomic carbon gas connected to a massive radio galaxy at redshift 3.8, Science

Astrobiology, Astrochemstry

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