2001A&A...373..757K


C.D.S. - SIMBAD4 rel 1.7 - 2020.08.09CEST04:43:47

2001A&A...373..757K - Astronomy and Astrophysics, volume 373, 757-781 (2001/7-3)

The Lyα forest at 1.5 < z < 4.

KIM T.-S., CRISTIANI S. and D'ODORICO S.

Abstract (from CDS):

Using high resolution (R∼45000), high S/N (∼20-50) VLT/UVES data, we have analyzed the Lyα forest of 3 QSOs in the neutral hydrogen (HI) column density range NHI=1012.5–16cm–2 at 1.5<z<2.4. We combined our results with similar high-resolution, high S/N data in the literature at z>2.4 to study the redshift evolution of the Lyα forest at 1.5<z<4. We have applied two types of analysis: the traditional Voigt profile fitting and statistics on the transmitted flux. The results from both analyses are in good agreement: 1. The differential column density distribution function, f(NHI), of the Lyα forest shows little evolution in the column density range NHI=1012.5–14cm–2, f(NHI)∝NHI–β, with β∼1.4-1.5 at 1.5<z<4 and with a possible increase of β to β∼1.7 at z<1.8. A flattening of the power law slope at lower column densities at higher z can be attributed to more severe line blending. A deficiency of lines with NHI>1014cm–2 is more noticeable at lower z than at higher z. The one-point function and the two-point function of the flux confirm that strong lines do evolve faster than weak lines; 2. The line number density per unit redshift, dn/dz, at NHI=1013.64–16cm–2 is well fitted by a single power law, dn/dz∝(1+z)2.19±0.27, at 1.5<z<4. In combination with the HST results from the HST QSO absorption line key project, the present data indicate that a flattening in the number density evolution occurs at z∼1.2. The line counts as a function of the filling factor at the transmitted flux F in the range 0<F<0.9 are constant in the interval 1.5<z<4. This suggests that the Hubble expansion is the main drive governing the forest evolution at z>1.5 and that the metagalactic UV background changes more slowly than a QSO-dominated background at z<2; 3. The observed cutoff Doppler parameter at the fixed column density NHI=1013.5cm–2, b_c, 13.5_, shows a weak increase with decreasing z, with a possible local b_c, 13.5_ maximum at z∼2.9; 4. The two-point velocity correlation function and the step optical depth correlation function show that the clustering strength increases as z decreases; 5. The evolution of the mean HI opacity, <τ>HI, is well approximated by an empirical power law, <τ>HI∝(1+z)3.34±0.17, at 1.5<z<4; 6. The baryon density, Ωb, derived both from the mean HI opacity and from the one-point function of the flux is consistent with the hypothesis that most baryons (over 90%) reside in the forest at 1.5<z<4, with little change in the contribution to the density, Ω, as a function of z.

Abstract Copyright:

Journal keyword(s): cosmology: observations - quasars: absorption lines

VizieR on-line data: <Available at CDS (J/A+A/373/757): tablea1.dat tablea2.dat tablea3.dat>

CDS comments: in ref list Crotts 1987MNRAS.228p..41C instead of 228.41

Simbad objects: 12

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Number of rows : 12

N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2020
#notes
1 QSO J0003-2603 QSO 00 03 22.9530051057 -26 03 18.306624161   18 17.53     ~ 272 0
2 QSO B0002+0507 QSO 00 05 20.2154590 +05 24 10.802383   16.56 16.21 16.26   ~ 170 1
3 6C 001403+811827 QSO 00 17 08.4748554 +81 35 08.136591   17.60 16.52 15.95   ~ 359 1
4 LBQS 0302-0019 QSO 03 04 49.8591748182 -00 08 13.537401746   18.08 17.80 17.5   ~ 237 0
5 HE 0515-4414 QSO 05 17 07.6239672230 -44 10 55.578294294 14.74 15.49 15.16     ~ 97 0
6 QSO B0636+68 QSO 06 42 04.2571549110 +67 58 35.621670643     16.46 16.01   ~ 205 1
7 PG 1101-264 QSO 11 03 25.2992132616 -26 45 15.809136362   16.08 16.02     ~ 238 0
8 QSO B1331+170 QSO 13 33 35.7826224 +16 49 04.014213   16.84 16.71 16.41   ~ 409 1
9 QSO B1946+770 QSO 19 44 54.8535021452 +77 05 52.674235091     15.8     ~ 140 0
10 QSO J2220-2803 QSO 22 20 06.7586653848 -28 03 23.466203761     16.0 16.10   ~ 88 0
11 QSO J2233-606 QSO 22 33 37.5814904803 -60 33 29.146578276 16.90 17.39 17.16 16.93 16.51 ~ 86 0
12 QSO B2237-0607 QSO 22 39 53.6809406614 -05 52 20.001981102     18.3     ~ 101 0

    Equat.    Gal    SGal    Ecl

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2020.08.09-04:43:47

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