TY  - JOUR
A1  - Crighton, Neil H. M.
A1  - Prochaska, J. Xavier
A1  - Murphy, Michael T.
A1  - Worseck, Gabor
A1  - Smith, Britton D.
T1  - Imprints of the first billion years
BT  - Lyman limit systems at z similar to 5
JF  - Monthly notices of the Royal Astronomical Society
N2  - Lyman limit systems (LLSs) trace the low-density circumgalactic medium and the most dense regions of the intergalactic medium, so their number density and evolution at high-redshift, just after reionization, are important to constrain. We present a survey for LLSs at high redshifts, z(LLS) = 3.5-5.4, in the homogeneous data set of 153 optical quasar spectra at z similar to 5 from the Giant Gemini GMOS survey. Our analysis includes detailed investigation of survey biases using mock spectra which provide important corrections to the raw measurements. We estimate the incidence of LLSs per unit redshift at z approximate to 4.4 to be l(z) = 2.6 +/- 0.4. Combining our results with previous surveys at z(LLS) < 4, the best-fit power-law evolution is l(z) = l(*)[(1 + z)/4](alpha) with l* = 1.46 +/- 0.11 and alpha = 1.70 +/- 0.22 (68 per cent confidence intervals). Despite hints in previous z(LLS) < 4 results, there is no indication for a deviation from this single power-law soon after reionization. Finally, we integrate our new results with previous surveys of the intergalactic and circumgalactic media to constrain the hydrogen column density distribution function, f(N-HI, X), over 10 orders ofmagnitude. The data at z similar to 5 are not well-described by the f(N-HI, X) model previously reported for z similar to 2-3 (after re-scaling) and a 7-pivot model fitting the full z similar to 2-5 data set is statistically unacceptable. We conclude that there is significant evolution in the shape of f(N-HI, X) over this similar to 2-billion-year period.
KW  - quasars: absorption lines
KW  - cosmological parameters
KW  - cosmology: observations
Y1  - 2019
U6  - https://doi.org/10.1093/mnras/sty2762
SN  - 0035-8711
SN  - 1365-2966
VL  - 482
IS  - 2
SP  - 1456
EP  - 1470
PB  - Oxford Univ. Press
CY  - Oxford
ER  - 
TY  - JOUR
A1  - Chen, Hsiao-Wen
A1  - Johnson, Sean D.
A1  - Straka, Lorrie A.
A1  - Zahedy, Fakhri S.
A1  - Schaye, Joop
A1  - Muzahid, Sowgat
A1  - Bouche, Nicolas
A1  - Cantalupo, Sebastiano
A1  - Marino, Raffaella Anna
A1  - Wendt, Martin
T1  - Characterizing circumgalactic gas around massive ellipticals at z approximate to 0.4-III.
BT  - the galactic environment of a chemically pristine Lyman limit absorber
JF  - Monthly notices of the Royal Astronomical Society
N2  - This paper presents a study of the galactic environment of a chemically pristine (<0.6 per cent solar metallicity) Lyman Limit system (LLS) discovered along the sightline towards QSO SDSSJ 135726.27+043541.4 (Z(QSO) = 1.233) at projected distance d = 126 physical kpc (pkpc) from a luminous red galaxy (LRG) at z = 0.33. Combining deep Hubble Space Telescope images, MUSE integral field spectroscopic data, and wide-field redshift survey data has enabled an unprecedented, ultradeep view of the environment around this LRG-LLS pair. A total of 12 galaxies, including the LRG, are found at d less than or similar to 400 pkpc and line-of-sight velocity Delta v < 600 km S-1 of the LLS, with intrinsic luminosity ranging from 0.001 L-* to 2 L-* and a corresponding stellar mass range of M-star approximate to 10(7-11) M-circle dot. All 12 galaxies contribute to a total mass of M-star = 1.6 x 10(11) M-circle dot with approximate to 80 per cent contained in the LRG. The line-of-sight velocity dispersion of these galaxies is found to be sigma (group) = 230 km s(-1) with the centre of mass at d(group) = 118 pkpc and line-of-sight velocity offset of Delta v(group) = 181 km s(-1) from the LLS. Three of these are located at d less than or similar to 100 pkpc from the LLS, and they are all faint with intrinsic luminosity less than or similar to 0.02 L-* and gas-phase metallicity of approximate to 10 per cent solar in their interstellar medium. The disparity in the chemical enrichment level between the LLS and the group members suggests that the LLS originates in infalling intergalactic medium and that parts of the intergalactic gas near old and massive galaxies can still remain chemically pristine through the not too distant past.
KW  - galaxies: elliptical and lenticular, cD
KW  - galaxies: formation
KW  - intergalactic medium
KW  - quasars: absorption lines
Y1  - 2019
U6  - https://doi.org/10.1093/mnras/sty3513
SN  - 0035-8711
SN  - 1365-2966
VL  - 484
IS  - 1
SP  - 431
EP  - 441
PB  - Oxford Univ. Press
CY  - Oxford
ER  - 
TY  - JOUR
A1  - Worseck, Gabor
A1  - Davies, Frederick B.
A1  - Hennawi, Joseph F.
A1  - Prochaska, J. Xavier
T1  - The Evolution of the He II-ionizing Background at Redshifts 2.3 < z < 3.8 Inferred from a Statistical Sample of 24 HST/COS He II Lyα Absorption Spectra
JF  - The astrophysical journal : an international review of spectroscopy and astronomical physics
N2  - We present measurements of the large-scale (≈40 comoving Mpc) effective optical depth of He ii Lyα absorption, ${\tau }_{\mathrm{eff}}$, at 2.54 < z < 3.86 toward 16 He ii-transparent quasars observed with the Cosmic Origins Spectrograph on the Hubble Space Telescope, to characterize the ionization state of helium in the intergalactic medium (IGM). We provide the first statistical sample of ${\tau }_{\mathrm{eff}}$ measurements in six signal-to-noise ratio gsim3 He ii sightlines at z > 3.5, and study the redshift evolution and sightline-to-sightline variance of ${\tau }_{\mathrm{eff}}$ in 24 He ii sightlines. We confirm an increase of the median ${\tau }_{\mathrm{eff}}$ from sime2 at z = 2.7 to ${\tau }_{\mathrm{eff}}\gtrsim 5$ at z > 3, and a scatter in ${\tau }_{\mathrm{eff}}$ that increases with redshift. The z > 3.5 He ii absorption is predominantly saturated, but isolated narrow (Δv < 650 km s−1) transmission spikes indicate patches of reionized helium. We compare our measurements to predictions for a range of UV background models applied to outputs of a large-volume (146 comoving Mpc)3 hydrodynamical simulation by forward-modeling our sample's quality and size. At z > 2.74, the variance in ${\tau }_{\mathrm{eff}}$ significantly exceeds expectations for a spatially uniform UV background, but is consistent with a fluctuating radiation field sourced by variations in the quasar number density and the mean free path in the post-reionization IGM. We develop a method to infer the approximate median He ii photoionization rate ${{\rm{\Gamma }}}_{\mathrm{He}{\rm{II}}}$ of a fluctuating UV background from the median ${\tau }_{\mathrm{eff}}$, finding a factor sime5 decrease in ${{\rm{\Gamma }}}_{\mathrm{He}{\rm{II}}}$ between z sime 2.6 and z sime 3.1. At z sime 3.1, ${{\rm{\Gamma }}}_{\mathrm{He}{\rm{II}}}=\left[{9.1}_{-1.2}^{+1.1}\,(\mathrm{stat}.){\,}_{-3.4}^{+2.4}\,(\mathrm{sys}.)\right]\times {10}^{-16}$ s−1 corresponds to a median He ii fraction of sime2.5%, indicating that our data probe the tail end of He ii reionization.
KW  - dark ages, reionization, first stars
KW  - diffuse radiation
KW  - intergalactic medium
KW  - quasars: absorption lines
Y1  - 2019
U6  - https://doi.org/10.3847/1538-4357/ab0fa1
SN  - 0004-637X
SN  - 1538-4357
VL  - 875
IS  - 2
PB  - IOP Publ. Ltd.
CY  - Bristol
ER  - 
TY  - JOUR
A1  - Zabl, Johannes
A1  - Bouche, Nicolas F.
A1  - Schroetter, Ilane
A1  - Wendt, Martin
A1  - Finley, Hayley
A1  - Schaye, Joop
A1  - Conseil, Simon
A1  - Contini, Thierry
A1  - Marino, Raffaella Anna
A1  - Mitchell, Peter
A1  - Muzahid, Sowgat
A1  - Pezzulli, Gabriele
A1  - Wisotzki, Lutz
T1  - MusE GAs FLOw and Wind (MEGAFLOW)
BT  - II. A study of gas accretion around z approximate to 1 star-forming galaxies with background quasars
JF  - Monthly notices of the Royal Astronomical Society
N2  - We use the MusE GAs FLOw and Wind (MEGAFLOW) survey to study the kinematics of extended disc-like structures of cold gas around z approximate to 1 star-forming galaxies. The combination of VLT/MUSE and VLT/UVES observations allows us to connect the kinematics of the gas measured through MgII quasar absorption spectroscopy to the kinematics and orientation of the associated galaxies constrained through integral field spectroscopy. Confirming previous results, we find that the galaxy-absorber pairs of the MEGAFLOW survey follow a strong bimodal distribution, consistent with a picture of MgII absorption being predominantly present in outflow cones and extended disc-like structures. This allows us to select a bona-fide sample of galaxy-absorber pairs probing these discs for impact paramometers of 10-70 kpc. We test the hypothesis that the disc-like gas is co-rotating with the galaxy discs, and find that for seven out of nine pairs the absorption velocity shares the sign of the disc velocity, disfavouring random orbits. We further show that the data are roughly consistent with inflow velocities and angular momenta predicted by simulations, and that the corresponding mass accretion rates are sufficient to balance the star formation rates.
KW  - galaxies: evolution
KW  - galaxies: formation
KW  - galaxies: haloes
KW  - galaxies: kinematics and dynamics
KW  - quasars: absorption lines
Y1  - 2019
U6  - https://doi.org/10.1093/mnras/stz392
SN  - 0035-8711
SN  - 1365-2966
VL  - 485
IS  - 2
SP  - 1961
EP  - 1980
PB  - Oxford Univ. Press
CY  - Oxford
ER  - 
TY  - JOUR
A1  - Berg, Trystyn A. M.
A1  - Ellison, Sara L.
A1  - Sanchez-Ramirez, Ruben
A1  - Lopez, Sebastian
A1  - Becker, George D.
A1  - Christensen, Lise
A1  - Cupani, Guido
A1  - Denney, Kelly D.
A1  - Worseck, Gabor
T1  - Sub-damped Lyman alpha systems in the XQ-100 survey - I. Identification and contribution to the cosmological H I budget
JF  - Monthly notices of the Royal Astronomical Society
KW  - galaxies: high-redshift
KW  - galaxies: ISM
KW  - quasars: absorption lines
Y1  - 2019
U6  - https://doi.org/10.1093/mnras/stz2012
SN  - 0035-8711
SN  - 1365-2966
VL  - 488
IS  - 3
SP  - 4356
EP  - 4369
PB  - Oxford Univ. Press
CY  - Oxford
ER  - 
TY  - JOUR
A1  - Schroetter, Ilane
A1  - Bouche, Nicolas F.
A1  - Zabl, Johannes
A1  - Contini, Thierry
A1  - Wendt, Martin
A1  - Schaye, Joop
A1  - Mitchell, Peter
A1  - Muzahid, Sowgat
A1  - Marino, Raffaella Anna
A1  - Bacon, Roland
A1  - Lilly, Simon J.
A1  - Richard, Johan
A1  - Wisotzki, Lutz
T1  - MusE GAs FLOw andWind (MEGAFLOW)
BT  - III. Galactic wind properties using background quasars
JF  - Monthly notices of the Royal Astronomical Society
N2  - We present results from our on-going MusE GAs FLOw and Wind (MEGAFLOW) survey, which consists of 22 quasar lines of sight, each observed with the integral field unit MUSE and the UVES spectrograph at the ESO Very Large Telescopes (VLT). The goals of this survey are to study the properties of the circumgalactic medium around z similar to 1 star-forming galaxies. The absorption-line selected survey consists of 79 strong MgII absorbers (with rest-frame equivalent width greater than or similar to 0.3 angstrom) and, currently, 86 associated galaxies within 100 projected kpc of the quasar with stellar masses (M-star) from 109 to 1011 M-circle dot. We find that the cool halo gas traced by MgII is not isotropically distributed around these galaxies from the strong bi-modal distribution in the azimuthal angle of the apparent location of the quasar with respect to the galaxy major axis. This supports a scenario in which outflows are bi-conical in nature and co-exist with a co-planar gaseous structure extending at least up to 60-80 kpc. Assuming that absorbers near the minor axis probe outflows, the current MEGAFLOW sample allowed us to select 26 galaxy-quasar pairs suitable for studying winds. From this sample, using a simple geometrical model, we find that the outflow velocity only exceeds the escape velocity when M-star less than or similar to 4 x 10(9) M-circle dot, implying the cool material is likely to fall back except in the smallest haloes. Finally, we find that the mass loading factor., the ratio between the ejected mass rate and the star formation rate, appears to be roughly constant with respect to the galaxy mass.
KW  - galaxies: evolution
KW  - galaxies: formation
KW  - intergalactic medium
KW  - quasars: absorption lines
Y1  - 2019
U6  - https://doi.org/10.1093/mnras/stz2822
SN  - 0035-8711
SN  - 1365-2966
VL  - 490
IS  - 3
SP  - 4368
EP  - 4381
PB  - Oxford Univ. Press
CY  - Oxford
ER  -