Cooling Radiation and the Lyα Luminosity of Forming Galaxies

By Mark A. Fardal, Neal Katz, J. Gardner, L. Hernquist, D. Weinberg, R. Dav'e. 2000

230 citations recorded by the source corpus.

We examine the cooling radiation from forming galaxies in hydrodynamic simulations of the LCDM model (cold dark matter with a cosmological constant), focusing on the Lyα line luminosities of high-redshift systems. Primordial composition gas condenses within dark matter potential wells, forming objects with masses and sizes comparable to the luminous regions of observed galaxies. As expected, the energy radiated in this process is comparable to the gravitational binding energy of the baryons, and the total cooling luminosity of the galaxy population peaks at z ≈ 2. However, in contrast to the classical picture of gas cooling from the ~106 K virial temperature of a typical dark matter halo, we find that most of the cooling radiation is emitted by gas with T < 20,000 K. As a consequence, roughly 50% of this cooling radiation emerges in the Lyα line. While a galaxy's cooling luminosity is usually smaller than the ionizing continuum luminosity of its young stars, the two are comparable in the most massive systems, and the cooling radiation is produced at larger radii, where the Lyα photons are less likely to be extinguished by dust. We suggest, in particular, that cooling radiation could explain the two large (~100 kpc), luminous (LLyα ~ 1044 ergs s-1) "blobs" of Lyα emission found in the narrowband survey of a z = 3 protocluster by Steidel and collaborators. Our simulations predict objects of the observed luminosity at about the right space density, and radiative transfer effects can account for the observed sizes and line widths. We discuss observable tests of this hypothesis for the nature of the Lyα blobs, and we present predictions for the contribution of cooling radiation to the Lyα luminosity function of galaxies as a function of redshift.

Subfields: Astronomy and Astrophysics, Instrumentation, Statistical and Nonlinear Physics

View Paper: https://www.semanticscholar.org/paper/eeab5bfca263f64de6458cbea5e72263aa0b51fa

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Citations in the corpus

SWIRE: The SIRTF Wide‐Area Infrared Extragalactic Survey (2001, methodology): “Indeed, no CDM-based model, whether semi-analytic or N-body, has successfully reproduced the observed numbers of high redshift ULIRGs from the submm data (Guiderdoni et al. 1998; Fardal et al. 2001; Devriendt & Guiderdoni 2000; Somerville et al. 2001; Somerville 2003).”
The baryonic assembly of dark matter haloes (2011, background): “…star-forming galaxies (Elmegreen & Elmegreen 2006; Genzel 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…”
The MUSE Hubble Ultra Deep Field Survey - VIII. Extended Lyman-α haloes around high-z star-forming galaxies (2017, background): “Another scenario to explain the extended Lyα emission is the socalled "cooling radiation" (e.g. Haiman et al. 2000; Fardal et al. 2001; Furlanetto et al. 2005).”
Extended Lyman-alpha emission from cold accretion streams (2011, background): “…all of the following processes: (a) Cold stream accretion is a natural explanation, where the fuel source is the dissipation of gravitational potential, also termed gravitational heating (e.g. Steidel et al. 2000; Haiman et al. 2000; Fardal et al. 2001; Dijkstra et al. 2006; Dijkstra & Loeb 2009).”
Constraining galaxy formation and cosmology with the conditional luminosity function of galaxies (2002, methodology): “…the lumi- c© 0000 RAS, MNRAS 000, 000–000 nosities of central galaxies are tightly correlated with the masses of their host haloes (e.g. Katz, Weinberg & Hernquist 1996; Fardal et al. 2001; Pearce et al. 2000; Kay et al. 2001; Kauffmann et al. 1993; Somerville & Primack 1999; Cole et al. 2000).”
Galaxy formation theory (2010, background): “Recent 3D hydrodynamical simulations (Fardal et al. 2001; see also Kereš et al. 2005; Ocvirk et al. 2008; Kereš et al. 2009), have suggested that a significant fraction of gas in low mass galaxies has never been shock heated ( t least within regions adequately resolved by the simulations; for…”
Lyα Emitting Galaxies as a Probe of Reionisation (2014, background): “Lyα cooling radiation has been predicted to 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;…”
Fluorescent Lyα Emission from the High-Redshift Intergalactic Medium (2005, background): “Within gravitationally collapsed objects, the gas tends to dissipate its internal energy by emitting line photons (e.g. Haiman, Spaans & Quataert 2000; Fardal et al. 2001; Furlanetto et al. 2005).”
Galaxies in a simulated ΛCDM Universe – I. Cold mode and hot cores (2008, background): “…the key result of K05, we find that galaxies with baryonic masses below 2 − 3× 1010M⊙ or halo masses below 2−3×1011M⊙ gain most of their mass through “cold” accretion of gas that has never been close to the halo virial temperature (see also Kay et al. 2000; Fardal et al. 2001; Katz et al. 2003).”
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).”
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 ).”
Star formation sustained by gas accretion (2014, background): “The structures have sizes from 50 to 100 kpc, luminosities between 1043 and 1044 erg s−1, and are identified by some authors as the observed Lyα blobs (LABs; Steidel et al. 2000; Fardal et al. 2001; Ouchi et al. 2009; Latif et al. 2011, see Sect.”
The First Cosmic Structures and Their Effects (2004, background): “This radiation has been advocated (Haiman, Spaans & Quataert 1999; Fardal et al. 2001) to explain the large (≈ 100 kpc), luminous (L ≈ 1044 erg s−1) “blobs” of Lyα emission found in narrow-band surveys of z ≈ 3 protoclusters (Steidel et al. 2000). review.tex; 15/06/2008; 8:20; p.21 22 In addition…”
Lyα COOLING EMISSION FROM GALAXY FORMATION (2010, background): “Our analysis of a sample of halos from a cosmological volume at z ≈ 3 confirms that (in agreement with previous studies; Haiman et al. 2000; Fardal et al. 2001; Dijkstra & Loeb 2009; Goerdt et al. 2010) cooling emission alone can in principle produce luminosities Lα ∼ 1043 − 1044 erg s−1 sufficient…”
Virial shocks in galactic haloes (2003, background): “Nevertheless, we notice that Katz et al. (2001) and Fardal et al. (2001) observe in their cosmological simulations that a large fraction of the mass accreted onto haloes indeed remains cold and is never heated to the virial temperature.”
Linking early‐ and late‐type galaxies to their dark matter haloes (2002, methodology): “…is therefore to consider ab initio models for galaxy formation, using either numerical simulations (e.g., Katz, Weinberg & Hernquist 1996; Fardal et al. 2001; Pearce et al. 2000; Kay et al. 2002) and/or “semi-analytical” models (e.g., White & Rees 1978; Kauffmann, White & Guiderdoni…”