Where Outflows Meet Inflows: Gas Kinematics in SSA22 Lyman-$\alpha$ Blob 2 Decoded by Advanced Radiative Transfer Modelling

Abstract

We present new spectroscopic observations of Lyman-$\alpha$ (Ly$\alpha$) Blob 2 ($z\sim$ 3.1). We observed extended Ly$\alpha$ emission in three distinct regions, where the highest Ly$\alpha$ surface brightness (SB) center is far away from the known continuum sources. We searched through the MOSFIRE slits that cover the high Ly$\alpha$ SB regions, but were unable to detect any significant nebular emission near the highest SB center. We further mapped the flux ratio of the blue peak to the red peak and found it is anti-correlated with Ly$\alpha$ SB with a power-law index of $\sim$ -0.4. We used radiative transfer models with both multiphase, clumpy and shell geometries and successfully reproduced the diverse Ly$\alpha$ morphologies. We found that most spectra suggest outflow-dominated kinematics, while 4/15 spectra imply inflows. A significant correlation exists between parameter pairs, and the multiphase, clumpy model may alleviate previously reported discrepancies. We also modeled Ly$\alpha$ spectra at different positions simultaneously and found that the variation of the inferred clump outflow velocities can be approximately explained by line-of-sight projection effects. Our results support the `central powering + scattering' scenario, i.e. the Ly$\alpha$ photons are generated by a central powering source and then scatter with outflowing, multiphase HI gas while propagating outwards. The infalling of cool gas near the blob outskirts shapes the observed blue-dominated Ly$\alpha$ profiles, but its energy contribution to the total Ly$\alpha$ luminosity is less than 10%, i.e. minor compared to the photo-ionization by star-forming galaxies and/or AGNs.

v1: 13 pages, 6 figures + Appendix. Submitted to MNRAS. v2: accepted version with moderate revision

References in corpus (17)

• Array Programming with NumPy
• The Circumgalactic Medium
• Strong Nebular Line Ratios in the Spectra of z~2-3 Star-forming Galaxies: First Results from KBSS-MOSFIRE
• 3D Lyman-alpha radiation transfer. I. Understanding Lyman-alpha line profile morphologies
• Nebular Emission Line Ratios in z~2-3 Star-Forming Galaxies with KBSS-MOSFIRE: Exploring the Impact of Ionization, Excitation, and Nitrogen-to-Oxygen Ratio
• The Launching of Cold Clouds by Galaxy Outflows I: Hydrodynamic Interactions with Radiative Cooling
• The Chandra Deep Protocluster Survey: Ly-alpha Blobs are powered by heating, not cooling
• Evidence for Cold Accretion onto a Massive Galaxy at High Redshift?
• The Overdense Environment of a Large Lyman-alpha Nebula at z~2.7
• The Keck Baryonic Structure Survey: Using foreground/background galaxy pairs to trace the structure and kinematics of circumgalactic neutral hydrogen at $z\sim 2$
• From Mirrors to Windows: Lyman-Alpha Radiative Transfer in a Very Clumpy Medium
• The Polarization of Scattered Lyman Alpha Radiation Around High-Redshift Galaxies
• Modeling $237$ Lyman-$\alpha$ spectra of the MUSE-Wide survey
• A z = 3 Lyman Alpha Blob Associated with a Damped Lyman Alpha System Proximate to its Background Quasar
• Deep Spectroscopy of Systematically Surveyed Extended Lyman-alpha Sources at z~3-5
• The KBSS-KCWI Survey: The connection between extended Ly$\alpha$ halos and galaxy azimuthal angle at $z\sim 2-3$
• Infrared and millimetre-wavelength evidence for cold accretion within a z = 2.83 Lyman-alpha blob

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