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  - 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  - Wisotzki, Lutz
A1  - Bacon, Roland
A1  - Blaizot, J.
A1  - Brinchmann, Jarle
A1  - Herenz, Edmund Christian
A1  - Schaye, Joop
A1  - Bouche, Nicolas
A1  - Cantalupo, Sebastiano
A1  - Contini, Thierry
A1  - Carollo, C. M.
A1  - Caruana, Joseph
A1  - Courbot, J. -B.
A1  - Emsellem, E.
A1  - Kamann, S.
A1  - Kerutt, Josephine Victoria
A1  - Leclercq, F.
A1  - Lilly, S. J.
A1  - Patricio, V.
A1  - Sandin, C.
A1  - Steinmetz, Matthias
A1  - Straka, Lorrie A.
A1  - Urrutia, Tanya
A1  - Verhamme, A.
A1  - Weilbacher, Peter Michael
A1  - Wendt, Martin
T1  - Extended Lyman alpha haloes around individual high-redshift galaxies revealed by MUSE
JF  - Science
N2  - We report the detection of extended Ly alpha emission around individual star-forming galaxies at redshifts z = 3-6 in an ultradeep exposure of the Hubble Deep Field South obtained with MUSE on the ESO-VLT. The data reach a limiting surface brightness (1 sigma) of similar to 1 x 10(-19) erg s(-1) cm(-2) arcsec(-2) in azimuthally averaged radial profiles, an order of magnitude improvement over previous narrowband imaging. Our sample consists of 26 spectroscopically confirmed Ly alpha-emitting, but mostly continuum-faint (m(AB) greater than or similar to 27) galaxies. In most objects the Ly alpha emission is considerably more extended than the UV continuum light. While five of the faintest galaxies in the sample show no significantly detected Ly alpha haloes, the derived upper limits suggest that this is due to insufficient S/N. Ly alpha haloes therefore appear to be ubiquitous even for low-mass (similar to 10(8)-10(9) M-circle dot) star-forming galaxies at z > 3. We decompose the Ly alpha emission of each object into a compact component tracing the UV continuum and an extended halo component, and infer sizes and luminosities of the haloes. The extended Ly alpha emission approximately follows an exponential surface brightness distribution with a scale length of a few kpc. While these haloes are thus quite modest in terms of their absolute sizes, they are larger by a factor of 5-15 than the corresponding rest-frame UV continuum sources as seen by HST. They are also much more extended, by a factor similar to 5, than Ly alpha haloes around low-redshift star-forming galaxies. Between similar to 40% and greater than or similar to 90% of the observed Ly alpha flux comes from the extended halo component, with no obvious correlation of this fraction with either the absolute or the relative size of the Ly alpha halo. Our observations provide direct insights into the spatial distribution of at least partly neutral gas residing in the circumgalactic medium of low to intermediate mass galaxies at z > 3.
KW  - galaxies: high-redshift
KW  - galaxies: evolution
KW  - galaxies: formation
KW  - cosmology: observations
KW  - intergalactic medium
Y1  - 2016
U6  - https://doi.org/10.1051/0004-6361/201527384
SN  - 1432-0746
VL  - 587
PB  - EDP Sciences
CY  - Les Ulis
ER  - 
TY  - JOUR
A1  - Evans, T. M.
A1  - Murphy, M. T.
A1  - Whitmore, J. B.
A1  - Misawa, T.
A1  - Centurion, Martin
A1  - Lopez, S.
A1  - Martins, C. J. A. P.
A1  - Molaro, P.
A1  - Petitjean, P.
A1  - Rahmani, H.
A1  - Srianand, R.
A1  - Wendt, Martin
T1  - The UVES Large Program for testing fundamental physics - III. Constraints on the fine-structure constant from three telescopes
JF  - Monthly notices of the Royal Astronomical Society
KW  - intergalactic medium
KW  - quasars: absorption lines
KW  - quasars: individual: HS 1549+1919
KW  - cosmology: miscellaneous
KW  - cosmology: observations
Y1  - 2014
U6  - https://doi.org/10.1093/mnras/stu1754
SN  - 0035-8711
SN  - 1365-2966
VL  - 445
IS  - 1
SP  - 128
EP  - 150
PB  - Oxford Univ. Press
CY  - Oxford
ER  - 
TY  - JOUR
A1  - Bonifacio, P.
A1  - Rahmani, H.
A1  - Whitmore, J. B.
A1  - Wendt, Martin
A1  - Centurion, Martin
A1  - Molaro, P.
A1  - Srianand, R.
A1  - Murphy, M. T.
A1  - Petitjean, P.
A1  - Agafonova, I. I.
A1  - Evans, T. M.
A1  - Levshakov, S. A.
A1  - Lopez, S.
A1  - Martins, C. J. A. P.
A1  - Reimers, D.
A1  - Vladilo, G.
T1  - Fundamental constants and high-resolution spectroscopy
JF  - Astronomische Nachrichten = Astronomical notes
KW  - atomic processes
KW  - cosmology: observations
KW  - elementary particles
KW  - line: formation
KW  - quasars: absorption lines
KW  - techniques: spectroscopic
Y1  - 2014
U6  - https://doi.org/10.1002/asna.201312005
SN  - 0004-6337
SN  - 1521-3994
VL  - 335
IS  - 1
SP  - 83
EP  - 91
PB  - Wiley-VCH
CY  - Weinheim
ER  - 
TY  - JOUR
A1  - Wendt, Martin
T1  - Constraints on variations of m(p)/m(e) based on UVES observations of H-2
JF  - Astronomische Nachrichten = Astronomical notes
N2  - This article summarizes the latest results on the proton-to-electron mass ratio derived from H-2 observations at high redshift in the light of possible variations of fundamental physical constants. The focus lies on UVES observations of the past years as enormous progress was achieved since the first positive results on / were published. With the better understanding of systematics, dedicated observation runs, and numerous approaches to improve wavelength calibration accuracy, all current findings are in reasonable good agreement with no variation and provide an upper limit of / < 1 x 10(-5) for the redshift range of 2 < z < 3. ((
KW  - cosmology: observations
KW  - early Universe
KW  - quasars: absorption lines
Y1  - 2014
U6  - https://doi.org/10.1002/asna.201312008
SN  - 0004-6337
SN  - 1521-3994
VL  - 335
IS  - 1
SP  - 106
EP  - 112
PB  - Wiley-VCH
CY  - Weinheim
ER  - 
TY  - JOUR
A1  - Draganova, Nadya
A1  - Richter, Philipp
A1  - Fechner, Cora
T1  - High-resolution observations of two O VI absorbers at z approximate to 2 toward PKS 1448-232
JF  - Astronomy and astrophysics : an international weekly journal
N2  - To explore the ionization conditions in highly-ionized absorbers at high redshift, we study in detail two intervening O vi absorbers at z approximate to 2 toward the quasar PKS 1448-232, based on high (R approximate to 75 000) and intermediate (R approximate to 45 000) resolution optical VLT/UVES spectra. We find that both absorption systems are composed of several narrow subcomponents with typical Civ/O VI Doppler-parameters of b < 10 km s(-1). This implies that the gas temperatures are T < 10(5) K and that the absorbers are photoionized by the UV background. The system at z = 2.1098 represents a simple, isolated O VI absorber that has only two absorption components and is relatively metal-rich (Z similar to 0.6 solar). Ioinization modeling implies that the system is photoionized with O VI, C IV, and H I coexisting in the same gas phase. The second system at z = 2.1660 represents a complicated, multi-component absorption system with eight O VI components spanning almost 300 km s(-1) in radial velocity. The photoionization modeling implies that the metallicity is non-uniform and relatively low (<= 0.1 solar) and that the O VI absorption must arise in a gas phase that differs from that traced by C IV, C III, and H I. Our detailed study of the two O VI systems towards PKS 1448-232 shows that multi-phase, multi-component high-ion absorbers similar to the one at z = 2.1660 can be described by applying a detailed ionization modeling of the various subcomponents to obtain reliable measurements of the physical conditions and the metal abundances in the gas.
KW  - intergalactic medium
KW  - quasars: absorption lines
KW  - cosmology: observations
Y1  - 2012
U6  - https://doi.org/10.1051/0004-6361/201116730
SN  - 0004-6361
VL  - 538
IS  - 1
PB  - EDP Sciences
CY  - Les Ulis
ER  - 
TY  - JOUR
A1  - Wendt, Martin
A1  - Molaro, P.
T1  - QSO 0347-383 and the invariance of m(p)/m(e) in the course of cosmic time
JF  - Astronomy and astrophysics : an international weekly journal
N2  - Context. The variation of the dimensionless fundamental physical constant mu = m(p)/m(e) - the proton to electron mass ratio - can be constrained via observation of Lyman and Werner lines of molecular hydrogen in the spectra of damped Lyman alpha systems (DLAs) in the line of sight to distant QSOs.
 Aims. Our intention is to maximize the possible precision of quasar absorption spectroscopy with regard to the investigation of the variation of the proton-to-electron mass-ratio mu. The demand for precision requires an understanding of the errors involved and effective techniques to handle present systematic errors.
 Methods. An analysis based on UVES high resolution data sets of QSO 0347-383 and its DLA is put forward and new approaches to some of the steps involved in the data analysis are introduced. We apply corrections for the observed offsets between discrete spectra and for the first time we find indications for inter-order distortions.
 Results. Drawing on VLT-UVES observations of QSO 0347-383 in 2009 our analysis yields Delta mu/mu = (4.3 +/- 7.2) x 10(-6) at z(abs) = 3.025.
 Conclusions. Current analyzes tend to underestimate the impact of systematic errors. Based on the scatter of the measured redshifts and the corresponding low significance of the redshift-sensitivity correlation we estimate the limit of accuracy of line position measurements to similar to 220 m s (1), consisting of roughly 150 m s (1) due to the uncertainty of the absorption line fit and about 150 m s (1) allocated to systematics related to instrumentation and calibration.
KW  - cosmology: observations
KW  - quasars: absorption lines
KW  - quasars: individual: QSO 0347-383
KW  - early Universe
Y1  - 2012
U6  - https://doi.org/10.1051/0004-6361/201218862
SN  - 0004-6361
VL  - 541
IS  - 3
PB  - EDP Sciences
CY  - Les Ulis
ER  -