Absorption-line systems in simulated galaxies fed by cold streams

By M. Fumagalli, J. Xavier Prochaska, D. Kasen, A. Dekel, D. Ceverino, Joel R. Primack. 2011

258 citations recorded by the source corpus.

Hydro-cosmological simulations reveal that massive galaxies at high redshift are fed by long narrow streams of merging galaxies and a smoother component of cold gas. We postprocess seven high-resolution simulated galaxies with radiative transfer to study the absorption characteristics of the gas in galaxies and streams, in comparison with the statistics of observed absorption-line systems. We find that much of the stream gas is ionized by UV radiation from background and local stellar sources, but still optically thick (NH I > 10 17 cm −2 ) so that the streams appear as Lyman-limit systems (LLSs). At z > 3, the fraction of neutral gas in streams becomes non-negligible, giving rise to damped Lyman α absorbers (DLAs) as well. The gas in the central and incoming galaxies remains mostly neutral, responsible for DLAs. Within one (two) virial radii, the covering factor of optically thick gas is 30 per cent of the observed absorbers in the foreground of quasars, the rest possibly arising from smaller galaxies or the intergalactic medium. The mean metallicity in the streams is ∼1 per cent solar, much lower than in the galaxies. The simulated galaxies reproduce the Lyα-absorption equivalent widths observed around Lymanbreak galaxies, but they severely underpredict the equivalent widths in metal lines, suggesting that the latter may arise from outflows. We conclude that the observed metal-poor LLSs are likely detections of the predicted cold streams. Revised analysis of the observed LLSs kinematics and simulations with more massive outflows in conjunction with the inflows may enable a clearer distinction between the signatures of the various gas modes.

Subfields: Astronomy and Astrophysics, Atomic and Molecular Physics, and Optics, Instrumentation

View Paper: https://www.semanticscholar.org/paper/a95f208e9e3496dfba42db5eed2d8e37566fc1e8

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Citations in the corpus

Extended Lyman-alpha emission from cold accretion streams (2011, background): “…CGM and ISM regions correspond mostly to damped Lyα absorbers (DLAs, NH > 2 10 20 cm−2) and the streams to Lyman limit systems (LLSs, NH = 1.6 10 17− 1019 cm−2) and even super Lyman limit systems (SLLSs, NH = 10 19 − 2 1020 cm−2), according to the definitions found in e.g. Fumagalli et al. (2011).”
The difficulty of getting high escape fractions of ionizing photons from high-redshift galaxies: A view from the FIRE cosmological simulations (2015, methodology): “The code is derived from the MCRT code SEDONA base (Kasen et al. 2006) and focuses specifically on radiative transfer of hydrogen ionizing photons in galaxies (see Fumagalli et al. 2011, 2014).”
METALLICITY EVOLUTION OF DAMPED Lyα SYSTEMS OUT TO z ∼ 5 (2012, methodology): “…if high redshift galaxies are surrounded by a thick disk of neutral gas (Prochaska & Wolfe 1997b; Wolfe et al. 2003, 2008; Rafelski et al. 2009, 2011; Fumagalli et al. 2011b), then stars that formedin situ in such gas at high redshift should be present inz = 0 galaxies, such as the Milk Way.”
The Giant Gemini GMOS survey of zem > 4.4 quasars – I. Measuring the mean free path across cosmic time (2014, background): “This will include dense, collapsed structures (e.g. galaxies) but the opacity may be dominated by more diffuse gas in the outskirts of dark matter haloes (e.g. Fumagalli et al. 2011) and even more distant and diffuse structures in the IGM.”
Four phases of angular-momentum buildup in high-z galaxies: from cosmic-web streams through an extended ring to disc and bulge (2014, methodology): “Our analysis here is rather simplified, not involving proper radiative transport (unlike, e.g. Fumagalli et al. 2011).”
Neutral hydrogen in galaxy haloes at the peak of the cosmic star formation history (2014, methodology): “The simulations of Fumagalli et al. (2011) included weak stellar feedback, but that feedback was insufficient to drive strong galactic outflows.”
Rotational support of giant clumps in high-z disc galaxies (2011, background): “, while the cold streams can also be detected in absorption mostly as Lyman-limit systems (Fumagalli et al. 2011).”
Toy models for galaxy formation versus simulations (2013, background): “They flow in at a constant inflow velocity that is comparable to the virial velocity, and they keep cold at >∼ 104K while dissipating the gained gravitational energy into cooling Lyman-alpha radiation (Dijkstra & Loeb 2009; Goerdt et al. 2010; Fumagalli et al. 2011).1”
THE BIMODAL METALLICITY DISTRIBUTION OF THE COOL CIRCUMGALACTIC MEDIUM AT z ≲ 1 (2013, background): “…Maller & Bullock 2004; Dekel & Birnboim 2006), while feedback from star formation and AGN activity can fuel massive outflows from a gas-rich galaxy that may choke off star formation (e.g., Kacprzak et al. 2008; Oppenheimer et al. 2010, 2012; Fumagalli et al. 2011b; Faucher-Giguère et al. 2011).”
EVIDENCE FOR UBIQUITOUS COLLIMATED GALACTIC-SCALE OUTFLOWS ALONG THE STAR-FORMING SEQUENCE AT z ∼ 0.5 (2013, background): “…gaseous halos with hydrogen and metals have already been used to better understand feedback models via comparison of ‘observations’ of the gas distribution along sightlines through the simulated halos with QSO absorption line studies (Fumagalli et al. 2011; Shen et al. 2012; Stinson et al. 2012).”
UBIQUITOUS GIANT Lyα NEBULAE AROUND THE BRIGHTEST QUASARS AT z ∼ 3.5 REVEALED WITH MUSE (2016, background): “These filaments represent a rich reservoir of pristine gas that drives galaxy formation and evolution, especially in the early Universe (e.g., Kereš et al. 2005; Dekel et al. 2009; van de Voort et al. 2011; Fumagalli et al. 2011).”
The MUSE Hubble Ultra Deep Field Survey - VIII. Extended Lyman-α haloes around high-z star-forming galaxies (2017, background): “Theoretical analyses and numerical simulations indeed predict that neutral hydrogen should be present around high-redshift star-forming galaxies (e.g. Kereš et al. 2005; Fumagalli et al. 2011; Faucher-Giguère et al. 2015).”
THE GASEOUS ENVIRONMENT OF HIGH-z GALAXIES: PRECISION MEASUREMENTS OF NEUTRAL HYDROGEN IN THE CIRCUMGALACTIC MEDIUM OF z ∼ 2–3 GALAXIES IN THE KECK BARYONIC STRUCTURE SURVEY (2012, methodology): “Fumagalli et al. (2011) also considered the covering fraction of H I surrounding 6 LBG-type galaxies atz = 2− 3 using cosmological zoom-in simulations with galactic winds included (though they are relatively weak with their particular implementation).”
THE CIRCUMGALACTIC MEDIUM OF MASSIVE GALAXIES AT z ∼ 3: A TEST FOR STELLAR FEEDBACK, GALACTIC OUTFLOWS, AND COLD STREAMS (2012, methodology): “Eris2’s covering factor of LLSs appears comparable or higher than those predicted at high redshift by Faucher-Giguère & Kereš (2011) and Fumagalli et al. (2011) for galaxies in the same mass range.”
Star formation sustained by gas accretion (2014, background): “3, central row, right panel), with a very large scatter indicating that the metals are not uniformly spread (Fumagalli et al. 2011b).”
DEMOGRAPHICS AND PHYSICAL PROPERTIES OF GAS OUTFLOWS/INFLOWS AT 0.4 < z < 1.4 (2012, methodology): “According to some models (Kimm et al. 2011; Fumagalli et al. 2011), detection of the inflows via a metal line definitely implies these are not cold accretion flows.”
On the evolution of the H i column density distribution in cosmological simulations (2012, result): “Only very recent works incorporated RT, primarily to account for the attenuation of the UVB (Razoumov et al. 2006; Pontzen et al. 2008; Fumagalli et al. 2011; Altay et al. 2011; McQuinn et al. 2011) and found a sharp transition between optically thin and self-shielded gas that is expected from the…”