Theory suggests that there are two primary modes of accretion through which dark-matter halos acquire the gas to form and fuel galaxies: hot- and cold-flow accretion. In cold-flow accretion, gas streams along cosmic web filaments to the centre of the halo, allowing for the efficient delivery of star-forming fuel. Recently, two quasar-illuminated H i Lyman ɑ (Lyα)-emitting objects were reported to have properties of cold, rotating structures1,2. However, the spatial and spectral resolution available was insufficient to constrain the radial flows associated with connecting filaments. With the Keck Cosmic Web Imager (KCWI)3, we now have eight times the spatial resolution, permitting the detection of these inspiralling flows. To detect these inflows, we introduce a suite of models that incorporate zonal radial flows, demonstrate their performance on a numerical simulation that exhibits cold-flow accretion, and show that they are an excellent match to KCWI velocity maps of two Lyα emitters observed around high-redshift quasars. These multi-filament inflow models kinematically isolate zones of radial inflow that correspond to extended filamentary emission. The derived gas flux and inflow path is sufficient to fuel the inferred central galaxy star-formation rate and angular momentum. Thus, our kinematic emission maps provide strong evidence that the inflow of gas from the cosmic web is building galaxies at the peak of star formation.
Access optionsAccess options
Subscribe to Journal
Get full journal access for 1 year
only $8.67 per issue
All prices are NET prices.
VAT will be added later in the checkout.
Rent or Buy article
Get time limited or full article access on ReadCube.
All prices are NET prices.
KCWI data on CSO38 and UM287 is publicly available. Data on UM287 will be available 18 months after the observation in Oct 2017. The data that support the plots within this paper and other findings of this study are available from the corresponding author upon reasonable request.
KCWI pipeline code is available on the W. M. Keck Observatory website.
Martin, D. C. et al. A giant protogalactic disk linked to the cosmic web. Nature 524, 192 (2015).
Martin, D. C. et al. A newly forming cold flow protogalactic disk, a signature of cold accretion from the cosmic web. Astrophys. J. 824, L5 (2016).
Morrissey, P. et al. The Keck Cosmic Web Imager Integral Field Spectrograph. Astrophys. J. 864, 93 (2018).
Danovich, M. et al. Four phases of angular-momentum buildup in high- z galaxies: from cosmic-web streams through an extended ring to disc and bulge. Mon. Not. R. Astron. Soc. 449, 2087–2111 (2015).
Danovich, M., Dekel, A., Hahn, O. & Teyssier, R. Coplanar streams, pancakes and angular-momentum exchange in high- z disc galaxies. Astrophys. J. 422, 1732–1749 (2012).
Stewart, K. et al. Orbiting circumgalactic gas as a signature of cosmological accretion. Astrophys. J. 738, 39 (2011).
Stewart, K. R. et al. Angular momentum acquisition in galaxy halos. Astrophys. J. 769, 74 (2013).
Arrigoni-Battaia, F. et al. Inspiraling halo accretion mapped in Lyα emission around a z ∼ 3 quasar. Mon. Not. R. Astron. Soc. 473, 3907–3940 (2017).
Vanzella, E. et al. Illuminating gas inflows/outflows in the MUSE deepest fields: Lyɑ nebulae around forming galaxies at z ≃ 3.3.Mon. Not. R. Astron. Soc. 465, 3803–3816 (2017).
Navarro, J. F., Frenk, C. S. & White, S. D. M. A universal density profile from hierarchical clustering. Astrophys. J. 490, 493–508 (1997).
Zolotov, A. et al. Compaction and quenching of high-z galaxies in cosmological simulations: blue and red nuggets. Mon. Not. R. Astron. Soc. 450, 2327–2353 (2015).
Ceverino, D. et al. Radiative feedback and the low efficiency of galaxy formation in low-mass haloes at high redshift. Mon. Not. R. Astron. Soc. 442, 1545–1559 (2014).
Akaike, H. A new look at the statistical model identification. IEEE Trans. Autom. Control 19, 716–723 (1974).
Cantalupo, S., Arrigoni-Battaia, F., Prochaska, J. X., Hennawi, J. F. & Madau, P. A cosmic web filament revealed in Lyman-α emission around a luminous high-redshift quasar. Nature 506, 63–66 (2014).
Trainor, R. & Steidel, C. C. Constraints on hyperluminous QSO lifetimes via fluorescent Lyα emitters at z≃ 2.7. Astrophys. J. 775, L3 (2013).
Trainor, R. F. & Steidel, C. C. The halo masses and galaxy environments of hyperluminous QSOs at z≃ 2.7 in the Keck Baryonic Structure Survey. Astrophys. J. 752, 39–51 (2012).
Martin, D. C. et al. IGM emission observations with the Cosmic Web Imager: I. The circum-QSO medium of QSO 1549+19, and evidence for a filamentary gas inflow. Astrophys. J. 786, 106–131 (2014).
Martin, D. C. et al. IGM emission observations with the Cosmic Web Imager: II. Discovery of extended, kinematically-linked emission around SSA22 Lymanɑ Blob 2. Astrophys. J. 786, 107–135 (2014).
Dekel, A. et al. Cold streams in early massive hot haloes as the main mode of galaxy formation. Nature 457, 451–454 (2009).
Dekel, A. & Birnboim, Y. Galaxy bimodality due to cold flows and shock heating. Mon. Not. R. Astron. Soc. 368, 2–20 (2006).
Ceverino, D. & Klypin, A. The role of stellar feedback in the formation of galaxies. Astrophys. J. 695, 292–309 (2009).
Kravtsov, A. V. On the origin of the global Schmidt law of star formation. Astrophys. J. 590, L1–L4 (2003).
Kravtsov, A. V., Klypin, A. A. & Khokhlov, A. M. Adaptive Refinement Tree: a new high‐resolution N‐body code for cosmological simulations. Astrophys. J. Suppl. 111, 73–94 (1997).
Kennicutt, R. C. J. The global Schmidt law in star-forming galaxies. Astrophys. J. 498, 541–552 (1998).
Dekel, A. & Krumholz, M. R. Steady outflows in giant clumps of high-z disc galaxies during migration and growth by accretion. Mon. Not. R. Astron. Soc. 432, 455–467 (2013).
Komatsu, E. et al. Five-year Wilkinson microwave anisotropy probeobservations: cosmological interpretation. Astrophys. J. Suppl. 180, 330–376 (2009).
Ceverino, D., Dekel, A. & Bournaud, F. High-redshift clumpy discs and bulges in cosmological simulations. Mon. Not. R. Astron. Soc. 404, 2151–2169 (2010).
Neufeld, D. A. The transfer of resonance-line radiation in static astrophysical media. Astrophys. J. 350, 216 (1990).
Verhamme, A., Schaerer, D. & Maselli, A. 3D Lyα radiation transfer. Astron. Astrophys. 460, 397–413 (2006).
Zheng, Z. & Miralda-Escudé, J. Monte Carlo simulation of Lyα scattering and application to damped Lyα systems. Astrophys. J. 578, 33–42 (2002).
Ferland, G. J., Korista, K. T., Verner, D. A., Ferguson, J. W., Kingdon, J. B. & Verner, E. M. CLOUDY 90: numerical simulation of plasmas and their spectra. Publ. Astron. Soc. Pac. 110, 761–778 (1998).
Goerdt, T. & Ceverino, D. Inflow velocities of cold flows streaming into massive galaxies at high redshifts. Mon. Not. R. Astron. Soc. 450, 3359–3370 (2015).
Cen, R. Evolution of cold streams and the emergence of the Hubble sequence. Astrophys. J. 789, L21 (2014).
Powell, M. J. D. An efficient method for finding the minimum of a function of several variables without calculating derivatives. Comput. J. 7, 155–162 (1964).
Schwarz, G. Estimating the dimension of a model. Ann. Stat. 6, 461–464 (1978).
Wisotzki, L. et al. Extended Lyman α haloes around individual high-redshift galaxies revealed by MUSE. Astron. Astrophys. 587, A98 (2016).
Heckman, T. M., Armus, L. & Miley, G. K. On the nature and implications of starburst-driven galactic superwinds. Astrophys. J. Suppl. 74, 833–868 (1990).
Steidel, C. C. et al. Diffuse Lyα emitting halos: a generic property of high-redshift star-forming galaxies. Astrophys. J. 736, 160–177 (2011).
Ocvirk, P., Pichon, C. & Teyssier, R. Bimodal gas accretion in the Horizon-Mare Nostrum galaxy formation simulation. Mon. Not. R. Astron. Soc 390, 1326–1338 (2008).
Hibbard, J. E., van der Hulst, J. M., Barnes, J. E. & Rich, R. M. High-resolution H [CSC]i[/CSC] mapping of NGC 4038/39 (“The Antennae”) and its tidal dwarf galaxy candidates. Astron. J. 122, 2969–2992 (2001).
This work was supported by the National Science Foundation, the W. M. Keck Observatory and the California Institute of Technology. The VELA simulations were performed at NASA Advanced Supercomputing at NASA Ames Research Center. D.C. is funded by the ERC Advanced Grant, STARLIGHT: Formation of the First Stars (project number 339177).
The authors declare no competing interests.
Publisher’s note: Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
Supplementary Figures 1–11, Supplementary Tables 1–8, Supplementary References 1–3.