TY - JOUR A1 - Becker, George D. A1 - D'Aloisio, Anson A1 - Christenson, Holly M. A1 - Zhu, Yongda A1 - Worseck, Gábor A1 - Bolton, James S. T1 - The mean free path of ionizing photons at 5 < z < 6 BT - evidence for rapid evolution near reionization JF - Monthly notices of the Royal Astronomical Society N2 - The mean free path of ionizing photons, lambda(mfp), is a key factor in the photoionization of the intergalactic medium (IGM). At z greater than or similar to 5, however, lambda(mfp) may be short enough that measurements towards QSOs are biased by the QSO proximity effect. We present new direct measurements of lambda(mfp) that address this bias and extend up to z similar to 6 for the first time. Our measurements at z similar to 5 are based on data from the Giant Gemini GMOS survey and new Keck LRIS observations of low-luminosity QSOs. At z similar to 6 we use QSO spectra from Keck ESI and VLT X-Shooter. We measure lambda(mfp) = 9.09(-1.28)(+1.62) proper Mpc and 0.75(-0.45)(+0.65) proper Mpc (68 percent confidence) at z = 5.1 and 6.0, respectively. The results at z = 5.1 are consistent with existing measurements, suggesting that bias from the proximity effect is minor at this redshift. At z = 6.0, however, we find that neglecting the proximity effect biases the result high by a factor of two or more. Our measurement at z = 6.0 falls well below extrapolations from lower redshifts, indicating rapid evolution in lambda(mfp) over 5 < z < 6. This evolution disfavours models in which reionization ended early enough that the IGM had time to fully relax hydrodynamically by z = 6, but is qualitatively consistent with models wherein reionization completed at z = 6 or even significantly later. Our mean free path results are most consistent with late reionization models wherein the IGM is still 20 percent neutral at z = 6, although our measurement at z = 6.0 is even lower than these models prefer. KW - intergalactic medium KW - quasars: absorption lines KW - cosmology: observations KW - dark ages KW - large-scale structure of Universe KW - reionization KW - first stars Y1 - 2021 U6 - https://doi.org/10.1093/mnras/stab2696 SN - 0035-8711 SN - 1365-2966 VL - 508 IS - 2 SP - 1853 EP - 1869 PB - Oxford Univ. Press CY - Oxford ER - TY - JOUR A1 - Bouma, Sietske Jeltje Deirdre A1 - Richter, Philipp A1 - Wendt, Martin T1 - The relation between Ly alpha absorbers and local galaxy filaments JF - Astronomy and astrophysics : an international weekly journal N2 - Context. The intergalactic medium (IGM) is believed to contain the majority of baryons in the universe and to trace the same dark matter structure as galaxies, forming filaments and sheets. Ly alpha absorbers, which sample the neutral component of the IGM, have been extensively studied at low and high redshift, but the exact relation between Ly alpha absorption, galaxies, and the large-scale structure is observationally not well constrained.Aims. In this study, we aim at characterising the relation between Ly alpha absorbers and nearby over-dense cosmological structures (galaxy filaments) at recession velocities Delta v <= 6700 km s(-1) by using archival observational data from various instruments.Methods. We analyse 587 intervening Ly alpha absorbers in the spectra of 302 extragalactic background sources obtained with the Cosmic Origins Spectrograph (COS) installed on the Hubble Space Telescope (HST). We combine the absorption line information with galaxy data of five local galaxy filaments from the V8k catalogue.Results. Along the 91 sightlines that pass close to a filament, we identify 215 (227) Ly alpha absorption systems (components). Among these, 74 Ly alpha systems are aligned in position and velocity with the galaxy filaments, indicating that these absorbers and the galaxies trace the same large-scale structure. The filament-aligned Ly alpha absorbers have a similar to 90% higher rate of incidence (d?/dz=189 for log N(HI) >= 13.2) and a slightly shallower column density distribution function slope (-beta=-1.47) relative to the general Ly alpha population at z=0, reflecting the filaments' matter over-density. The strongest Ly alpha absorbers are preferentially found near galaxies or close to the axis of a filament, although there is substantial scatter in this relation. Our sample of absorbers clusters more strongly around filament axes than a randomly distributed sample would do (as confirmed by a Kolmogorov-Smirnov test), but the clustering signal is less pronounced than for the galaxies in the filaments. KW - galaxies: halos KW - intergalactic medium KW - quasars: absorption lines KW - large-scale structure of Universe KW - techniques: spectroscopic KW - ultraviolet: general Y1 - 2021 U6 - https://doi.org/10.1051/0004-6361/202039786 SN - 0004-6361 SN - 1432-0746 VL - 647 PB - EDP Sciences CY - Les Ulis ER - TY - JOUR A1 - Husemann, Bernd A1 - Bielby, R. A1 - Jahnke, K. A1 - Arrigoni-Battaia, F. A1 - Worseck, Gabor A1 - Shanks, T. A1 - Wardlow, J. A1 - Scholtz, J. T1 - Cosmic dance at z similar to 3 BT - Detecting the host galaxies of the dual AGN system LBQS 0302-0019 and Jil with HAWK-I plus GRAAL JF - Astronomy and astrophysics : an international weekly journal N2 - We recently discovered that the luminous radio-quiet (QSO) LBQS 0302-0019 at z=3.286 is likely accompanied by an obscured AGN at 20 kpc projected distance, which we dubbed Jil. It represents the tightest candidate obscured/unobscured dual AGN system at z >3. To verify the dual AGN scenario we obtained deep K-s band (rest-frame V band) imaging with the VLT/HAWK-I+GRAAL instrument at 0 '.4 resolution during science verification in January 2018. Indeed, we detect the individual host galaxies of the QSO and Jil with estimated stellar masses of log(M-*/M-circle dot)=11.4 +/- 0.5 and log(M-*/M-circle dot)=10.9 +/- 0.5, respectively. Near-IR spectra obtained with VLT-KMOS reveal a clear [O-III] lambda 5007 line detection at the location of Jil which does not contribute significantly to the Ks band flux. Both observations therefore corroborate the dual AGN scenario. A comparison to Illustris cosmological simulations suggests a parent halo mass of log(M-halo/M-*)=13.2 +/- 0.5 for this interacting galaxy system, corresponding to a very massive dark matter halo at that epoch. KW - Galaxies: interactions KW - Galaxies: high-redshift KW - large-scale structure of Universe KW - instrumentation: adaptive optics KW - quasars: individual: LBQS 0302-0018 Y1 - 2018 U6 - https://doi.org/10.1051/0004-6361/201833363 SN - 1432-0746 VL - 614 PB - EDP Sciences CY - Les Ulis ER - TY - JOUR A1 - Nuza, Sebastian E. A1 - Parisi, Florencia A1 - Scannapieco, Cecilia A1 - Richter, Philipp A1 - Gottloeber, Stefan A1 - Steinmetz, Matthias T1 - The distribution of gas in the Local Group from constrained cosmological simulations: the case for Andromeda and the Milky Way galaxies JF - Monthly notices of the Royal Astronomical Society N2 - We study the gas distribution in the Milky Way and Andromeda using a constrained cosmological simulation of the Local Group (LG) within the context of the CLUES (Constrained Local UniversE Simulations) project. We analyse the properties of gas in the simulated galaxies at z = 0 for three different phases: 'cold', 'hot' and H i, and compare our results with observations. The amount of material in the hot halo (M-hot a parts per thousand 4-5 x 10(10) M-aS (TM)), and the cold (M-cold(r a parts per thousand(2) 10 kpc) a parts per thousand 10(8) M-aS (TM)) and H i components displays reasonable agreement with observations. We also compute the accretion/ejection rates together with the H i (radial and all-sky) covering fractions. The integrated H i accretion rate within r = 50 kpc gives similar to 0.2-0.3 M-aS (TM) yr(-1), i.e. close to that obtained from high-velocity clouds in the Milky Way. We find that the global accretion rate is dominated by hot material, although ionized gas with T a parts per thousand(2) 10(5) K can contribute significantly too. The net accretion rates of all material at the virial radii are 6-8 M-aS (TM) yr(-1). At z = 0, we find a significant gas excess between the two galaxies, as compared to any other direction, resulting from the overlap of their gaseous haloes. In our simulation, the gas excess first occurs at z similar to 1, as a result of the kinematical evolution of the LG. KW - methods: numerical KW - Galaxy: halo KW - intergalactic medium KW - Local Group KW - large-scale structure of Universe Y1 - 2014 U6 - https://doi.org/10.1093/mnras/stu643 SN - 0035-8711 SN - 1365-2966 VL - 441 IS - 3 SP - 2593 EP - 2612 PB - Oxford Univ. Press CY - Oxford ER -