Publications (3)0 Total impact
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R. Bielby,
M. D. Hill,
T. Shanks,
N. H. M. Crighton,
L. Infante,
C. G. Bornancini,
H. Francke,
P. Heraudeau, D. G. Lambas,
N. Metcalfe,
D. Minniti,
N. Padilla,
T. Theuns,
P. Tummuangpak,
P. Weilbacher
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ABSTRACT: We present a catalogue of 2135 galaxy redshifts from the VLT LBG Redshift
Survey (VLRS), a spectroscopic survey of z ~ 3 galaxies in wide fields centred
on background quasi-stellar objects. We have used deep optical imaging to
select galaxies via the Lyman-break technique. Spectroscopy of the Lyman-break
galaxies (LBGs) was then made using the Visible Multi-Object Spectrograph
(VIMOS), giving a mean redshift of z=2.79. We analyse the clustering properties
of the VLRS sample and also of the VLRS sample combined with the smaller area
Keck-based survey of Steidel et al. From the semiprojected correlation
function, wp({\sigma}) we find that the results are well fit with a single
power-law model, with clustering scale lengths of r0=3.46+-0.41 and 3.83+-0.24
Mpc/h, respectively. We note that the corresponding combined {\xi}(r) slope is
flatter than for local galaxies at {\gamma} = 1.5-1.6 rather than {\gamma}=1.8.
This flat slope is confirmed by the z-space correlation function, {\xi}(s), and
in the range 10<s<100 Mpc/h the VLRS shows ~2.5{\sigma} excess over the
{\Lambda} cold dark matter. This excess may be consistent with recent evidence
for non-Gaussianity in clustering results at z~1. We then analyse the LBG
z-space distortions using the 2D correlation function, {\xi}({\sigma}, {\pi}),
finding for the combined sample a large-scale infall parameter of $\beta$ =
0.38+-0.19 and a velocity dispersion of 420km/s. Based on our measured {\beta},
we are able to determine the gravitational growth rate, finding a value of f(z
= 3)=0.99+-0.50 (or f{\sigma}8 = 0.26+-0.13), which is the highest redshift
measurement of the growth rate via galaxy clustering and is consistent with
{\Lambda}CDM. Finally, we constrain the mean halo mass for the LBG population,
finding that the VLRS and combined sample suggest mean halo masses of
log(MDM/Msun) = 11.57+-0.15 and 11.73+-0.07, respectively.
04/2012;
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N. H. M. Crighton,
R. Bielby,
T. Shanks,
L. Infante,
C. G. Bornancini,
N. Bouche, D. G. Lambas,
J. D. Lowenthal,
D. Minniti,
S. L. Morris,
N. Padilla,
C. Peroux,
P. Petitjean,
T. Theuns,
P. Tummuangpak,
P. M. Weilbacher,
L. Wisotzki,
G. Worseck
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ABSTRACT: We have measured redshifts for 243 z ~3 quasars in nine VLT VIMOS LBG redshift survey areas, each of which is centred on a known bright quasar. Using spectra of these quasars, we measure the cross-correlation between neutral hydrogen gas causing the Lya forest and 1020 Lyman-break galaxies at z ~3. We find an increase in neutral hydrogen absorption within 5 h^-1 Mpc of a galaxy in agreement with the results of Adelberger et al. (2003, 2005). The Lya-LBG cross-correlation can be described by a power-law on scales larger than 3 h^-1 Mpc. When galaxy velocity dispersions are taken into account our results at smaller scales (<2 h^-1 Mpc) are also in good agreement with the results of Adelberger et al. (2005). There is little immediate indication of a region with a transmission spike above the mean IGM value which might indicate the presence of star-formation feedback. To measure the galaxy velocity dispersions, which include both intrinsic LBG velocity dispersion and redshift errors, we have used the LBG-LBG redshift space distortion measurements of Bielby et al. (2010). We find that the redshift-space transmission spike implied in the results of Adelberger et al. (2003) is too narrow to be physical in the presence of the likely LBG velocity dispersion and is likely to be a statistical fluke. Nevertheless, neither our nor previous data can rule out the presence of a narrow, real-space transmission spike, given the evidence of the increased Lya absorption surrounding LBGs which can mask the spike's presence when convolved with a realistic LBG velocity dispersion. Finally, we identify 176 CIV systems in the quasar spectra and find an LBG-CIV correlation strength on scales of 10 h^-1 Mpc consistent with the relation measured at ~Mpc scales. Comment: 33 pages, 16 figures, accepted by MNRAS
06/2010;
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Rich Bielby,
T. Shanks,
P. M. Weilbacher,
L. Infante,
N. H. M. Crighton,
Carlos Bornancini,
N. Bouché,
P. Héraudeau, D. G. Lambas,
J. Lowenthal,
D. Minniti,
N. Padilla,
P. Petitjean,
T. Theuns
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ABSTRACT: We present the initial imaging and spectroscopic data acquired as part of the
VLT VIMOS Lyman-break galaxy Survey. UBR (or UBVI) imaging covers five 36'x36'
fields centred on bright z>3 QSOs, allowing ~21,000 2<z<3.5 galaxy candidates
to be selected using the Lyman-break technique. We performed spectroscopic
follow-up using VIMOS, measuring redshifts for 1020 z>2 LBGs and 10 z>2 QSOs
from a total of 19 VIMOS pointings. From the galaxy spectra, we observe a
625+-510 km/s velocity offset between the ISM absorption and Ly-alpha emission
line redshifts. Using the photometric and spectroscopic catalogues, we have
analysed the galaxy clustering at z~3. In the photometric case, the angular
correlation function, w(theta), is well fit by a double power-law with
clustering scale-length, r_0 = 3.19+0.32-0.54 Mpc/h for r < 1 Mpc/h and r_0 =
4.59+0.31-0.33 Mpc/h at larger scales. Using the redshift sample we estimate
the semi-projected correlation function, w_p(sigma) and find r_0 =
3.67+0.23-0.24 Mpc/h for the VLT sample and r_0 = 3.98+0.14-0.15 Mpc/h for a
combined VLT+Keck sample. From the z-space correlation functions and assuming
the above xi(r) models, we find that the combined VLT and Keck surveys require
a galaxy velocity dispersion, <w_z^2>^1/2 ~ 700 km/s, higher than the ~400 km/s
found by previous authors. We also measure a value for the gravitational growth
rate parameter of beta(z=3) = 0.48+-0.17, implying a low value for the bias of
b = 2.06+1.1-0.5. This value is consistent with the galaxy clustering amplitude
which gives b = 2.22+-0.16, assuming the standard cosmology, implying that the
evolution of the gravitational growth rate is also consistent with Einstein
gravity. We have compared our LBG clustering amplitudes with lower redshift
measurements and find that the clustering strength is not inconsistent with
that of low-redshift L* spirals for simple 'long-lived' galaxy models.
05/2010;
