Extended Lyman-alpha emission from cold accretion streams

By J. Rosdahl, Jérémy Blaizot. 2011

154 citations recorded by the source corpus.

{Abridged} We investigate the observability of cold accretion streams at redshift 3 via Lyman-alpha (Lya) emission and the feasibility of cold accretion as the main driver of Lya blobs (LABs). We run cosmological zoom simulations focusing on 3 halos spanning two orders of magnitude in mass, roughly from 10^11 to 10^13 solar masses. We use a version of the Ramses code that includes radiative transfer of UV photons, and we employ a refinement strategy that allows us to resolve accretion streams in their natural environment to an unprecedented level. For the first time, we self-consistently model self-shielding in the cold streams from the cosmological UV background, which enables us to predict their temperatures, ionization states and Lya luminosities with improved accuracy. We find the efficiency of gravitational heating in cold streams in a ~10^11 solar mass halo is around 10-20% throughout most of the halo but reaching much higher values close to the center. As a result most of the Lya luminosity comes from gas which is concentrated at the central 20% of the halo radius, leading to Lya emission which is not extended. In more massive halos, of >10^12 solar masses, cold accretion is complex and disrupted, and gravitational heating does not happen as a steady process. Ignoring the factors of Lya scattering, local UV enhancement, and SNe feedback, cold accretion alone in these massive halos can produce LABs that largely agree with observations in terms of morphology, extent, and luminosity. Our simulations slightly and systematically over-predict LAB abundances, perhaps hinting that the interplay of these ignored factors may have a negative net effect on extent and luminosity. We predict that a factor of a few increase in sensitivity from current observational limits should unambiguously reveal continuum-free accretion streams around massive galaxies at z=3.

Subfields: Astronomy and Astrophysics

View Paper: https://www.semanticscholar.org/paper/5aa3f18ae7ff10a9f632e4d384a0a7a06082a26d

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Citations in the corpus

• Lyα Emitting Galaxies as a Probe of Reionisation (2014, methodology): “…give rise to spatially extended Lyα radiation (Haiman, Spaans, & Quataert 2000; Fardal et al. 2001), and provides a possible explanation for Lyα ‘blobs’ PASA, 31, e040 (2014) doi:10.1017/pasa.2014.33 (Dijkstra & Loeb 2009; Goerdt et al. 2010; Faucher-Giguère et al. 2010; Rosdahl & Blaizot 2012).”
• Star formation sustained by gas accretion (2014, background): “Simulations by Rosdahl & Blaizot (2012) also suggest that cold stream accretion can account for the Lyα emission.”
• UBIQUITOUS GIANT Lyα NEBULAE AROUND THE BRIGHTEST QUASARS AT z ∼ 3.5 REVEALED WITH MUSE (2016, background): “…al. 2014); ii) "continuumpumping" or Lyα scattering from the quasar broad-line region (see e.g. Cantalupo et al. 2014); iii) Lyα collisional excitation (so called Lyα "cooling radiation"; Haiman et al. 2000; Fardal et al. 2001; Dijkstra et al. 2006; Cantalupo et al. 2008,Rosdahl & Blaizot 2012 ).”
• Fluctuating feedback-regulated escape fraction of ionizing radiation in low-mass, high-redshift galaxies (2017, unknown): “Even so, the simulations of Rosdahl & Blaizot (2012) constrain the global effect of the UV background to the gas at densities below nH .”
• ESCAPE FRACTION OF IONIZING PHOTONS DURING REIONIZATION: EFFECTS DUE TO SUPERNOVA FEEDBACK AND RUNAWAY OB STARS (2014, background): “However, this is unlikely the case, given that galaxies in the atomic cooling halos are fed mainly by dense filaments and satellites at high redshift (e.g.,Powell et al. 2011), which are self-shielded from the background radiation (Faucher-Giguère et al. 2010; Rosdahl & Blaizot 2012).”
• Extended Lyman α haloes around individual high-redshift galaxies revealed by MUSE (2015, background): “Cooling radiation has been proposed as the main power source for the so-called Lyα “blobs” (e.g. Fardal et al. 2001; Goerdt et al. 2010) and may also produce spatially extended Lyα emission around normal high-redshift galaxies (e.g. Faucher-Giguère et al. 2010; Rosdahl & Blaizot 2012).”
• The MUSE Hubble Ultra Deep Field Survey - VIII. Extended Lyman-α haloes around high-z star-forming galaxies (2017, background): “However, because the density is higher at the centre of the DM halo and the Lyα emissivity resulting from cooling is proportional to the density squared if the gas is warm enough, the Lyα emission is expected to be centrally concentrated (as found in Rosdahl & Blaizot 2012).”