Lyα COOLING EMISSION FROM GALAXY FORMATION

By C. Faucher-Giguére, D. Keres̆, M. Dijkstra, L. Hernquist, M. Zaldarriaga. 2010

177 citations recorded by the source corpus.

Recent numerical and analytical studies have shown that galaxies accrete most of their baryons via the cold mode, from streams with temperatures T ∼ 104–105 K. At these temperatures, the streams should radiate primarily in the Lyα line and have therefore been proposed as a model to power the extended, high-redshift objects known as Lyα blobs, and may also be relevant for powering a range of less luminous Lyα sources. We introduce a new Lyα radiative transfer code, αRT, and calculate the transport of the Lyα emission from cold accretion in cosmological hydrodynamical simulations. In this paper, we describe our methodology, and address physical and numerical issues that are critical to making accurate predictions for the cooling luminosity, but that have been mostly neglected or treated simplistically so far. In particular, we highlight the importance of self-shielding and of properly treating sub-resolution models in numerical simulations. Most existing simulations do not self-consistently incorporate these effects, which can lead to order-of-magnitude errors in the predicted cooling luminosity. Using a combination of post-processing ionizing radiative transfer and re-simulation techniques, we develop an approximation to the consistent evolution of the self-shielded gas. We quantify the dependence of the Lyα cooling luminosity on halo mass at z = 3 for the simplified problem of pure gas accretion embedded in the cosmic radiation background and without feedback, and present radiative transfer results for a particular system. While pure cooling in massive halos (without additional energy input from star formation and active galactic nuclei) is in principle sufficient to produce Lα ∼ 1043–1044 erg s−1 blobs, this requires including energy released in gas of density sufficient to form stars, but which is kept 100% gaseous in our optimistic estimates. Excluding emission from such dense gas yields lower luminosities by up to one to two orders of magnitude at high masses, making it difficult to explain the observed Lyα blobs with pure cooling. Resonant scattering produces diffuse Lyα halos, even for centrally concentrated emission, and broad double peaked line profiles. In particular, the emergent line widths are in general not representative of the velocity dispersion within galactic halos and cannot be directly used to infer host halo masses.

Subfields: Astronomy and Astrophysics, Electrical and Electronic Engineering, Instrumentation

View Paper: https://www.semanticscholar.org/paper/169819fa9d9b61b0470881342d6ce8abafd3fec7

How researchers see this paper

The researchers whose trusted networks rank it highest, strongest advocate first. Every researcher gets a different order.

In Astronomy and Astrophysics

In Electrical and Electronic Engineering

In Instrumentation

Citations in the corpus

Neutral hydrogen in galaxy haloes at the peak of the cosmic star formation history (2014, methodology): “Confirmation of the accuracy of this approximation in radiative transfer experiments can be found in Faucher-Giguère et al. (2010) and Rahmati et al. (2013).”
FIRE-2 simulations: physics versus numerics in galaxy formation (2017, methodology): “We account for self-shielding with a local Sobolev/Jeans-length approximation (Appendix B), calibrated in full radiative transfer experiments in Faucher-Giguère et al. (2010) and Rahmati et al. (2013).”
The MUSE Hubble Ultra Deep Field Survey - VIII. Extended Lyman-α haloes around high-z star-forming galaxies (2017, background): “A number of other theoretical analyses have been carried out to predict the expected cooling radiation contribution (Furlanetto et al. 2005; Dijkstra & Loeb 2009; Faucher-Giguère et al. 2010; Rosdahl & Blaizot 2012).”
The baryonic assembly of dark matter haloes (2011, methodology): “…et al. 2006; Dekel, Sari & Ceverino 2009b; Dekel et al. 2009a), Lyα blobs (e.g. Fardal et al. 2001; Dijkstra & Loeb 2009; Goerdt et al. 2010, but see Faucher-Giguère et al. 2010), dense absorption systems in quasar and galaxy spectra (e.g. Dekel et al. 2009a; Kimm et al. 2011; Stewart et al.…”
Using Lyman-α to detect galaxies that leak Lyman continuum (2014, background): “…of 13 (FWHM ∼ 1000 km s−1), which differentiates them from LyCleaking candidates, as well as images, with extended Lyα emission over several tens of kpc. Faucher-Giguère et al. (2010) computed the Lyα spectra of cold streams, which they find double-peaked, almost symmetrical (note that the IGM…”
Extended Lyman-alpha emission from cold accretion streams (2011, result): “This generic result is consistent with early expectations from Schaye (2001) and recent numerical estimates (e.g. Kollmeier et al. 2010; Faucher-Giguère et al. 2010; Aubert & Teyssier 2010).”
Toy models for galaxy formation versus simulations (2013, result): “…at 0.1Rv 1 Note that SPH simulations, which tend to underestimate the dissipation rate in the cold streams, may yield somewhat different results (Faucher-Giguère et al. 2010; van de Voort et al. 2011b; Nelson et al. 2013). should be compared to that shown in the left panels for Rv, and to the…”
Galaxies on FIRE (Feedback In Realistic Environments): stellar feedback explains cosmologically inefficient star formation (2013, methodology): “Confirmation of the accuracy of this approximation in radiative transfer experiments can be found in Faucher-Giguère et al. (2010) and Rahmati et al. (2013).”
ON LYMAN-LIMIT SYSTEMS AND THE EVOLUTION OF THE INTERGALACTIC IONIZING BACKGROUND (2011, methodology): “…and the intensity that 3 Over and above our radiative transfer calculations, the ionizing background is turned off on-the-fly in these simulations for regions with number densities of hydrogen greater than 10−2 cm−3 in order to mimic self-shielding as described in Faucher-Giguère et al. (2010).”
Star formation sustained by gas accretion (2014, background): “Faucher-Giguère et al. (2011) showed from simulations that a factor of 2 increase in the mass loading factor or a factor of 2”
On the evolution of the H i column density distribution in cosmological simulations (2012, result): “This transition can also be seen in the photoionization rate (right panel) which drops at n H & 0.01 cm−3, consistent with equation (13) and previous studies (Tajiri & Umemura 1998; Razoumov et al. 2006; Faucher-Giguère et al. 2010; Nagamine et al. 2010; Fumagalli et al. 2011; Altay et al. 2011).”
Absorption-line systems in simulated galaxies fed by cold streams (2011, background): “Moreover, a sensible determination of the temperature has obvious implications for collision ionization and emission properties (Faucher-Giguère et al. 2010).”
EVIDENCE FOR PopIII-LIKE STELLAR POPULATIONS IN THE MOST LUMINOUS Lyα EMITTERS AT THE EPOCH OF REIONIZATION: SPECTROSCOPIC CONFIRMATION (2015, background): “Faucher-Giguère et al. (2010) provides predictions of the total Lyα cooling luminosity as a function of halo mass and redshift.”
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).”
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).”
The structure and dynamical evolution of the stellar disc of a simulated Milky Way-mass galaxy (2016, methodology): “Gas self-shielding is accounted for with a local Jeans-length approximation, which is consistent with the radiative transfer calculations in Faucher-Giguère et al. (2010).”
The origin and evolution of the galaxy mass–metallicity relation (2015, methodology): “Gas self-shielding is accounted for with a local Jeans-length approximation, which is consistent with the radiative transfer calculations in Faucher-Giguère et al. (2010).”