Lyα blobs as an observational signature of cold accretion streams into galaxies

By M. Dijkstra, Abraham Loeb. 2009

158 citations recorded by the source corpus.

Recent hydrodynamic simulations of galaxy formation reveal streams of cold (T ∼ 10 4 K) gas flowing into the centres of dark matter haloes as massive as 10 12-13.5 M ⊙ at redshifts z ∼ 1-3. In this paper, we show that if ≳20 per cent of the gravitational binding energy of the gas is radiated away then the simulated cold flows are spatially extended Lyα sources with luminosities, Lyα linewidths and number densities that are comparable to those of observed Lyα blobs. Furthermore, the filamentary structure of the cold flows can explain the wide range of observed Lyα blob morphologies. Since the most massive haloes form in dense environments, the association of Lyα blobs with overdense regions arise naturally. We argue that Lyα blobs - even those which are clearly associated with starburst galaxies or quasars -provide direct observational support for the cold accretion mode of galaxies. We discuss various testable predictions of this association.

Subfields: Astronomy and Astrophysics, Instrumentation

View Paper: https://www.semanticscholar.org/paper/0f0d780e49469a0f84d6d5f1feeabdd9c591c00d

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In Astronomy and Astrophysics

1. P. Hopkins
2. L. Hernquist
3. R. Dav'e
4. C. Faucher-Giguére
5. D. Keres̆
6. A. Dekel
7. R. Somerville
8. E. Quataert

In Instrumentation

1. P. Hopkins
2. L. Hernquist
3. A. Dekel
4. C. Faucher-Giguére
5. R. Dav'e
6. D. Keres̆
7. A. Shapley
8. C. Steidel

Citations in the corpus

• FORMATION OF MASSIVE GALAXIES AT HIGH REDSHIFT: COLD STREAMS, CLUMPY DISKS, AND COMPACT SPHEROIDS (2009, unknown): “The simulations allow us to predict the observable appearance of the cold streams that drive galaxy formation at high redshift, either in emission as Lyman-alpha Blobs (Dijkstra & Loeb 2009; Goerdt et al. 2009), or in absorption as Lymanlimit systems or Damped Lyman-alpha systems (Dekel et al. 2009)”
• 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).”
• Lyα COOLING EMISSION FROM GALAXY FORMATION (2010, methodology): “The analytic model of Dijkstra & Loeb (2009) is more sophisticated than the simple energetic argument above, as it accounts for the fact that the fraction of cold gas in halos diminishes with increasing mass.”
• 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).”
• DIFFUSE Lyα EMITTING HALOS: A GENERIC PROPERTY OF HIGH-REDSHIFT STAR-FORMING GALAXIES (2011, background): “…theoretical investigations focusing primarily on diffuse and extended Lyα from the outer parts of galaxies or LAEs have deliberately neglected the scattering of Lyα from the inside out (Dijkstra et al. 2006; Dijkstra & Loeb 2009; Kereš et al. 2009; Faucher-Giguere et al. 2010; Goerdt et al. 2009).”
• GIANT GAMMA-RAY BUBBLES FROM FERMI-LAT: ACTIVE GALACTIC NUCLEUS ACTIVITY OR BIPOLAR GALACTIC WIND? (2010, background): “Momentum wind outflowing galactic supershells can also be driven by Lyα radiation pressure around starforming regions (Dijkstra & Loeb 2009).”
• Lyα Emitting Galaxies as a Probe of Reionisation (2014, background): “…via the Balmer lines, because Lyα cooling radiation is accompanied by an Hα luminosity that is jcoll,Lyα jcoll,Hα = EαEHα 〈 1s2p〉 〈 13〉 exp ( EHα kBT ) ∼ 100 times weaker, which is much weaker than expected for case-B recombination (where the Hα flux is ∼ 8 times weaker, e.g. Dijkstra & Loeb 2009).”
• THE STRUCTURE AND KINEMATICS OF THE CIRCUMGALACTIC MEDIUM FROM FAR-ULTRAVIOLET SPECTRA OF z ≃ 2–3 GALAXIES (2010, background): “…including giant Lyα “blobs” (Steidel et al. 2000) has been ascribed to cooling radiation from the denser portions of the cold streams as they are accreting directly onto the galaxy’s central regions (e.g., Haiman et al. 2000; Furlanetto et al. 2005; Dijkstra & Loeb 2009; Goerdt et al. 2009).”
• The baryonic assembly of dark matter haloes (2011, background): “…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 spectra (e.g. Dekel…”
• Absorption-line systems in simulated galaxies fed by cold streams (2011, background): “…proposed as a signature of cold gas accretion that powers Lyα blobs (e.g. Haiman, Spaans & Quataert 2000; Fardal et al. 2001; Furlanetto et al. 2005; Dijkstra & Loeb 2009; Goerdt et al. 2010; Matsuda et al. 2010), but the resonant nature of the Lyα line and the different physical mechanisms that…”
• 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”