Ly$\alpha$ Blobs from Cold Streams Undergoing Kelvin-Helmholtz Instabilities

Abstract

We present an analytic toy model for the radiation produced by the interaction between the cold streams thought to feed massive halos at high redshift and their hot CGM. We begin by deriving cosmologically motivated parameters for the streams as they enter the halo virial radius, $R_{\mathrm{v}}$, as a function of halo mass and redshift. For $10^{12}{M}_{\odot }$ halos at $z=2$, we find the Hydrogen number density in streams to be $n_{\mathrm{H},\mathrm{s}}\sim (0.1-5)\times 10^{-2}{\mathrm{cm}}^{-3}$, a factor of $\delta \sim (30-300)$ times denser than the hot CGM density, while the stream radii are in the range $R_{\mathrm{s}}\sim (0.03-0.50)R_{\mathrm{v}}$. As the streams accelerate towards the halo centre, they become denser and narrower. The stream-CGM interaction induces Kelvin-Helmholtz Instability (KHI), which leads to entrainment of CGM mass by the stream and therefore to stream deceleration by momentum conservation. Assuming that the entrainment rates derived by Mandelker et al. 2019 in the absence of gravity can be applied locally at each halocentric radius, we derive equations of motion for the stream in the halo. Using these, we derive the net acceleration, mass growth, and energy dissipation induced by the stream-CGM interaction, as a function of halo mass and redshift, for different CGM density profiles. For the range of model parameters considered, we find that the interaction can induce dissipation luminosities $L_{\mathrm{diss}}>10^{42}\mathrm{erg}{\mathrm{s}}^{-1}$ within $\le 0.6R_{\mathrm{v}}$ of halos with $M_{\mathrm{v}}>10^{12}{M}_{\odot }$ at $z=2$, with the emission scaling with halo mass and redshift approximately as $\propto M_{\mathrm{v}}(1+z{)}^2$. The magnitude and spatial extent of the emission produced in massive halos at high redshift is consistent with observed Ly$\alpha$ blobs, though better treatment of the UV background and self-shielding is needed to solidify this conclusion.

16 pages, 6 figures, resubmitted to MNRAS with minor revisions following referee report. Model has been refined with fewer simplifying assumptions, but with no significant changes to our results. Several subtleties and caveats have been more clearly presented

References in corpus (84)

• E pur si muove: Galiliean-invariant cosmological hydrodynamical simulations on a moving mesh
• How Do Galaxies Get Their Gas?
• Galaxy Bimodality due to Cold Flows and Shock Heating
• Cold streams in early massive hot haloes as the main mode of galaxy formation
• Radiative Transfer in a Clumpy Universe: II. The Utraviolet Extragalactic Background
• Virial shocks in galactic haloes?
• Cosmological Simulations with TreeSPH
• Lyman Alpha Imaging of a Proto-Cluster Region at <z>=3.09
• A cosmic web filament revealed in Lyman-alpha emission around a luminous high-redshift quasar
• Diffuse Lyman Alpha Emitting Halos: A Generic Property of High Redshift Star Forming Galaxies
• Moving mesh cosmology: tracing cosmological gas accretion
• Bimodal gas accretion in the Horizon-MareNostrum galaxy formation simulation
• Lyman Alpha Radiation From Collapsing Protogalaxies I: Characteristics of the Emergent Spectrum
• Four phases of angular-momentum buildup in high-z galaxies: from cosmic-web streams through an extended ring to disc and bulge
• A Subaru Search for Ly-alpha Blobs in and around the Proto-cluster Region at Redshift z=3.1
• The rates and modes of gas accretion on to galaxies and their gaseous haloes
• Toy Models for Galaxy Formation versus Simulations
• Absorption line systems in simulated galaxies fed by cold streams
• Ubiquitous giant Ly $\alpha$ nebulae around the brightest quasars at $z\sim 3.5$ revealed with MUSE
• The Baryonic Assembly of Dark Matter Halos
• The growth and entrainment of cold gas in a hot wind
• High-redshift clumpy discs and bulges in cosmological simulations
• Cooling Radiation and the Lyman-alpha Luminosity of Forming Galaxies
• Quasar Quartet Embedded in Giant Nebula Reveals Rare Massive Structure in Distant Universe
• Signatures of Cool Gas Fueling a Star-Forming Galaxy at Redshift 2.3
• A Population of Faint Extended Line Emitters and the Host Galaxies of Optically Thick QSO Absorption Systems
• Lyman-alpha Cooling Emission from Galaxy Formation
• Universal gas density and temperature profile
• Moving mesh cosmology: numerical techniques and global statistics
• Lyman Alpha Blobs as an Observational Signature of Cold Accretion Streams into Galaxies
• The Impact of Star Formation Feedback on the Circumgalactic Medium
• Properties of gas in and around galaxy haloes
• QSO MUSEUM I: A sample of 61 extended Ly$\alpha$-emission nebulae surrounding $z\sim 3$ quasars
• Gravity-driven Lyman-alpha blobs from cold streams into galaxies
• Multiphase Gas and the Fractal Nature of Radiative Turbulent Mixing Layers
• How cold gas continuously entrains mass and momentum from a hot wind
• Seeding the formation of cold gaseous clouds in Milky Way size halos
• Cold accretion flows and the nature of high column density HI absorption at redshift 3
• Co-planar streams, pancakes, and angular-momentum exchange in high-z disc galaxies
• A Lyman-alpha blob in the GOODS South field: evidence for cold accretion onto a dark matter halo
• Extended Lyman Alpha Emission Around Young Quasars: a Constraint on Galaxy Formation
• Lyman-alpha Emission from Structure Formation
• The Chandra Deep Protocluster Survey: Ly-alpha Blobs are powered by heating, not cooling
• IGM Emission Observations with the Cosmic Web Imager: I. The Circum-QSO Medium of QSO 1549+19, and Evidence for a Filamentary Gas Inflow
• Lyman alpha Resonant Scattering in Young Galaxies - Predictions from Cosmological Simulations
• Quasars Probing Quasars VII. The Pinnacle of the Cool Circumgalactic Medium Surrounds Massive z~2 Galaxies
• On the Survival of Cool Clouds in the Circum-Galactic Medium
• Zooming in on accretion - I. The structure of halo gas
• The discovery of a galaxy-wide superwind from a young massive galaxy at redshift z~3
• Extended Lyman Alpha Nebulae at z ~ 2.3: An Extremely Rare and Strongly Clustered Population?
• Inspiraling Halo Accretion Mapped in Lyman-$\alpha$ Emission around a $z\sim 3$ Quasar
• The Subaru Ly-alpha blob survey: A sample of 100 kpc Ly-alpha blobs at z=3
• Simulations of radiative turbulent mixing layers
• Possible Signatures of a Cold-Flow Disk from MUSE using a z=1 galaxy--quasar pair towards SDSSJ1422-0001
• The Distribution of Lya-Emitting Galaxies at z=2.3
• Instability of Supersonic Cold Streams Feeding Galaxies IV: Survival of Radiatively Cooling Streams
• Evidence for Cold Accretion onto a Massive Galaxy at High Redshift?
• Systematic Survey of Extended Lyman-alpha Sources over z~3-5
• The Overdense Environment of a Large Lyman-alpha Nebula at z~2.7
• Strong Field-to-Field Variation of Lyman alpha Nebulae Populations at z~2.3
• The Nature of Lya Blobs: Supernova-Dominated Primordial Galaxies
• A Keck/DEIMOS Spectroscopy of Lyman Alpha Blobs at Redshift z=3.1
• Cold Filamentary Accretion and the Formation of Metal Poor Globular Clusters and Halo Stars
• The Lyman-alpha glow of gas falling into the dark matter halo of a z=3 galaxy
• Instability of Supersonic Cold Streams Feeding Galaxies I: Linear Kelvin-Helmholtz Instability with Body Modes
• The MUSE Hubble Ultra Deep Field Survey VIII : Extended Lyman-alpha haloes around high-redshift star-forming galaxies
• The extended Lyman-alpha emission surrounding the z=3.04 radio-quiet QSO1205-30: Primordial infalling gas illuminated by the quasar?
• IGM Emission Observations with the Cosmic Web Imager: II. Discovery of Extended, Kinematically-Linked Emission around SSA22 Lyman-alpha Blob 2
• On the Origin of Lyman-$\alpha$ Blobs at High Redshift: Kinematic Evidence for a Hyperwind Galaxy at z = 3.1
• Instability of Supersonic Cold Streams Feeding Galaxies III: Kelvin-Helmholtz Instability in Three Dimensions
• Inflow velocities of cold flows streaming into massive galaxies at high redshifts
• Witnessing galaxy assembly in an extended z~3 structure
• Spitzer identifications and classifications of submillimeter galaxies in giant, high-redshift Lyman-alpha emission-line nebulae
• Detectability of cold streams into high-redshift galaxies by absorption lines
• The impact of magnetic fields on cold streams feeding galaxies
• Lyman-alpha blobs: polarization arising from cold accretion
• High-Resolution Submillimeter Imaging of the Ly-alpha Blob1 in SSA 22
• Instability of Supersonic Cold Streams Feeding Galaxies II. Nonlinear Evolution of Surface and Body Modes of Kelvin-Helmholtz Instability
• Kelvin-Helmholtz Instability in Self-Gravitating Streams
• CGM properties in VELA and NIHAO simulations; the OVI ionization mechanism: dependence on redshift, halo mass and radius
• X-ray and SZ constraints on the properties of hot CGM
• The hydrodynamic stability of gaseous cosmic filaments
• A high baryon fraction in massive haloes at z~3
• Positive feedback at the disc-halo interface

Cited by in corpus (22)

• Instability of Supersonic Cold Streams Feeding Galaxies IV: Survival of Radiatively Cooling Streams
• Three Lyman-alpha emitting filaments converging to a massive galaxy group at z=2.91: discussing the case for cold gas infall
• Resolving shocks and filaments in galaxy formation simulations: effects on gas properties and star formation in the circumgalactic medium
• The bending of the star-forming main sequence traces the cold- to hot-accretion transition mass over 0<z<4
• The evolution of turbulent galactic discs: gravitational instability, feedback and accretion
• A cosmic stream of atomic carbon gas connected to a massive radio galaxy at redshift 3.8
• OVI Traces Photoionized Streams With Collisionally Ionized Boundaries in Cosmological Simulations of $z\sim 1$ Massive Galaxies
• The interplay between feedback, accretion, transport and winds in setting gas-phase metal distribution in galaxies
• Directly tracing cool filamentary accretion over >100 kpc into the interstellar medium of a quasar host at z=1
• A Multiwavelength Study of ELAN Environments (AMUSE${}^2$). Mass budget, satellites spin alignment and gas infall in a massive $z\sim 3$ quasar host halo
• Mapping the "invisible" circumgalactic medium around a z $\sim$ 4.5 radio galaxy with MUSE
• The AGORA High-resolution Galaxy Simulations Comparison Project. VI. Similarities and Differences in the Circumgalactic Medium
• Entrainment of Hot Gas into Cold Streams: The Origin of Excessive Star-formation Rates at Cosmic Noon
• Radiative Turbulent Mixing Layers and the Survival of Magellanic Debris
• The Origin and Evolution of Lyman-alpha Blobs in Cosmological Galaxy Formation Simulations
• Cosmic gas highways in C-EAGLE simulations
• Formation of compact galaxies in the Extreme-Horizon simulation
• Stability and Ly$\alpha$ emission of Cold Stream in the Circumgalactic Medium: impact of magnetic fields and thermal conduction
• Distinguishing Between Photoionized and Collisionally Ionized Gas in the Circumgalactic Medium
• A path towards constraining the evolution of the interstellar medium and outflows in the Milky Way using APOGEE
• Magnetising galaxies with cold inflows
• Statistical Properties of Cold Streams In Massive Star-Forming Halos in TNG50