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1. Resolved galactic superwinds reconstructed around their host galaxies at z > 3

   https://doi.org/10.1093/mnras/stab1041  

   Chen, Mandy C ; Chen, Hsiao-Wen ; Gronke, Max ; Rauch, Michael ; Broadhurst, Tom ( May 2021 , Monthly Notices of the Royal Astronomical Society)

   ABSTRACT This paper presents a detailed analysis of two giant Lyman-alpha (Ly α) arcs detected near galaxies at z = 3.038 and z = 3.754 lensed by the massive cluster MACS 1206−0847 (z = 0.44). The Ly α nebulae revealed in deep MUSE observations exhibit a double-peaked profile with a dominant red peak, indicating expansion/outflowing motions. One of the arcs stretches over 1 arcmin around the cluster Einstein radius, resolving the velocity field of the line-emitting gas on kpc scales around three star-forming galaxies of 0.3–$1.6\, L_*$ at z = 3.038. The second arc spans 15 arcsec in size, roughly centred around two low-mass Ly α emitters of $\approx 0.03\, L_*$ at z = 3.754. All three galaxies in the z = 3.038 group exhibit prominent damped Ly α absorption (DLA) and several metal absorption lines, in addition to nebular emission lines such as $\hbox{He ii}$$\lambda \, 1640$ and C iii]λλ1906, 1908. Extended Ly α emission appears to emerge from star-forming regions with suppressed surface brightness at the centre of each galaxy. Significant spatial variations in the Ly α line profile are observed which, when unaccounted for in the integrated line, leads to biased constraints for the underlying gas kinematics. The observed spatial variations indicate the presence of a steep velocity gradient in amore »continuous flow of high column density gas from star-forming regions into a low-density halo environment. A detailed inspection of available galaxy spectra shows no evidence of AGN activity in the galaxies, and the observed Ly α signals are primarily explained by resonant scattering. The study presented in this paper shows that spatially resolved imaging spectroscopy provides the most detailed insights yet into the kinematics of galactic superwinds associated with star-forming galaxies.« less
2. Brighter and More Massive Galaxies in the Vicinity of Lyα Nebulae

   https://doi.org/10.3847/1538-4357/aca3ac  

   Wells, Natalie K. ; Prescott, Moire K. M. ; Finlator, Kristian M. ( December 2022 , The Astrophysical Journal)

   It has been well established in the local universe that galaxy properties differ based on the large-scale environment in which they reside. As luminous Lyαnebulae have been shown to trace overdense environments atz∼ 2–3, comparing the properties of galaxies within Lyαnebulae systems to those in the field can provide insight into how and when locally observed trends between galaxy properties and environment emerged. Six Lyαnebulae were discovered atz∼ 2.3 in a blind search of the GOODS-S extragalactic field, a region also covered by the 3D-HST spectroscopic survey. Utilizing 3D-HST data, we identified 86 galaxies in the vicinity of these nebulae and used statistical tests to compare their physical properties to galaxies elsewhere in the field. Galaxies lying within 320 proper kpc of a Lyαnebula are roughly half a magnitude brighter than those in the field, with higher stellar masses, higher star formation rates, and larger effective radii. Even when considering the effects of sample incompleteness, our study suggests that galaxies in overdensities atz∼ 2.3 traced by Lyαnebulae are being influenced by their environment. Furthermore, Lyα-nebula-associated galaxies lie on the same main sequence of star formation as field galaxies but have a larger proportion of high-mass galaxies, consistent with themore »idea that galaxy evolution is accelerated in rich environments. Expanded surveys for Lyαnebulae in other deep extragalactic fields and galaxy spectroscopic follow-up with the James Webb Space Telescope (JWST) will better constrain the demographics of Lyα-nebula-associated galaxies.

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3. Where outflows meet inflows: gas kinematics in SSA22 Ly α blob 2 decoded by advanced radiative transfer modelling

   https://doi.org/10.1093/mnras/stac958  

   Li, Zhihui ; Steidel, Charles C. ; Gronke, Max ; Chen, Yuguang ; Matsuda, Yuichi ( April 2022 , Monthly Notices of the Royal Astronomical Society)

   We present new spectroscopic observations of Ly α (Ly α) Blob 2 (z ∼ 3.1). We observed extended Ly α emission in three distinct regions, where the highest Ly α surface brightness (SB) centre is far away from the known continuum sources. We searched through the MOSFIRE slits that cover the high Ly α SB regions, but were unable to detect any significant nebular emission near the highest SB centre. We further mapped the flux ratio of the blue peak to the red peak and found it is anticorrelated with Ly α SB with a power-law index of ∼ –0.4. We used radiative transfer models with both multiphase, clumpy, and shell geometries and successfully reproduced the diverse Ly α 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 modelled Ly α 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 α photons are generated by a central powering source and then scatter with outflowing, multiphase H  i gas whilemore »propagating outwards. The infalling of cool gas near the blob outskirts shapes the observed blue-dominated Ly α profiles, but its energy contribution to the total Ly α luminosity is less than 10 per cent, i.e. minor compared to the photoionization by star-forming galaxies and/or AGNs.

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4. Ubiquitous cold and massive filaments in cool core clusters

   https://doi.org/10.1051/0004-6361/201935350  

   Olivares, V. ; Salome, P. ; Combes, F. ; Hamer, S. ; Guillard, P. ; Lehnert, M. D. ; Polles, F. L. ; Beckmann, R. S. ; Dubois, Y. ; Donahue, M. ; et al ( November 2019 , Astronomy & Astrophysics)

   Multi-phase filamentary structures around brightest cluster galaxies (BCG) are likely a key step of AGN-feedback. We observed molecular gas in three cool cluster cores, namely Centaurus, Abell S1101, and RXJ1539.5, and gathered ALMA (Atacama Large Millimeter/submillimeter Array) and MUSE (Multi Unit Spectroscopic Explorer) data for 12 other clusters. Those observations show clumpy, massive, and long (3−25 kpc) molecular filaments, preferentially located around the radio bubbles inflated by the AGN. Two objects show nuclear molecular disks. The optical nebula is certainly tracing the warm envelopes of cold molecular filaments. Surprisingly, the radial profile of the H α /CO flux ratio is roughly constant for most of the objects, suggesting that (i) between 1.2 and 6 times more cold gas could be present and (ii) local processes must be responsible for the excitation. Projected velocities are between 100 and 400 km s −1 , with disturbed kinematics and sometimes coherent gradients. This is likely due to the mixing in projection of several thin (and as yet) unresolved filaments. The velocity fields may be stirred by turbulence induced by bubbles, jets, or merger-induced sloshing. Velocity and dispersions are low, below the escape velocity. Cold clouds should eventually fall back and fuel the AGN.more »We compare the radial extent of the filaments, r fil , with the region where the X-ray gas can become thermally unstable. The filaments are always inside the low-entropy and short-cooling-time region, where t cool / t ff  <  20 (9 of 13 sources). The range of t cool / t ff of 8−23 at r fil , is likely due to (i) a more complex gravitational potential affecting the free-fall time t ff (sloshing, mergers, etc.) and (ii) the presence of inhomogeneities or uplifted gas in the ICM, affecting the cooling time t cool . For some of the sources, r fil lies where the ratio of the cooling time to the eddy-turnover time, t cool / t eddy , is approximately unity.« less
5. Discovery of a Protocluster Core Associated with an Enormous Lya Nebula at z = 2.3

   https://doi.org/10.3847/1538-4357/ac29c6  

   Li, Qiong ; Wang, Ran ; Dannerbauer, Helmut ; Cai, Zheng ; Emonts, Bjorn ; Prochaska, Jason Xavier ; Battaia, Fabrizio Arrigoni ; Neri, Roberto ; Zhang, Chengpeng ; Fan, Xiaohui ; et al ( December 2021 , The Astrophysical Journal)

   Abstract The MAMMOTH-1 nebula at z = 2.317 is an enormous Ly α nebula (ELAN) extending to a ∼440 kpc scale at the center of the extreme galaxy overdensity BOSS 1441. In this paper, we present observations of the CO(3 − 2) and 250 GHz dust-continuum emission from MAMMOTH-1 using the IRAM NOrthern Extended Millimeter Array. Our observations show that CO(3 − 2) emission in this ELAN has not extended widespread emission into the circum- and inter-galactic media. We also find a remarkable concentration of six massive galaxies in CO(3 − 2) emission in the central ∼100 kpc region of the ELAN. Their velocity dispersions suggest a total halo mass of M 200 c ∼ 10 13.1 M ⊙ , marking a possible protocluster core associated with the ELAN. The peak position of the CO(3 − 2) line emission from the obscured AGN is consistent with the location of the intensity peak of MAMMOTH-1 in the rest-frame UV band. Its luminosity line ratio between the CO(3 − 2) and CO(1 − 0) r 3,1 is 0.61 ± 0.17. The other five galaxies have CO(3 − 2) luminosities in the range of (2.1–7.1) × 10 9 K km s −1 pcmore »2 , with the star-formation rates derived from the 250 GHz continuum of (<36)–224 M ⊙ yr −1 . Follow-up spectroscopic observations will further confirm more member galaxies and improve the accuracy of the halo mass estimation.« less