367 research outputs found
First Results from Viper: Detection of Small-Scale Anisotropy at 40 GHZ
Results of a search for small-scale anisotropy in the cosmic microwave
background (CMB) are presented. Observations were made at the South Pole using
the Viper telescope, with a .26 degree (FWHM) beam and a passband centered at
40 GHz. Anisotropy band-power measurements in bands centered at l = 108, 173,
237, 263, 422 and 589 are reported. Statistically significant anisotropy is
detected in all bands.Comment: 5 pages, 4 figures, uses emulateapj.sty, submitted to ApJ Letter
No excess of bright galaxies around the redshift 7.1 quasar ULAS J1120+0641
We present optical and near-infrared imaging of the field of the z = 7.0842 quasar ULAS J112001.48+064124.3 taken with the Hubble Space Telescope. We use these data to search for galaxies that may be physically associated with the quasar, using the Lyman break technique, and find three such objects, although the detection of one in Spitzer Space Telescope imaging strongly suggests it lies at z ⌠2. This is consistent with the field luminosity function and indicates that there is no excess of >Lâ
galaxies within 1 Mpc of the quasar. A detection of the quasar shortwards of the Lyα line is consistent with the previously observed evolution of the intergalactic medium at z > 5.5.SC acknowledges support from the NSF grant AST-1010004 and NASA HST grant GO-13033.06-A, RJM acknowledges ERC funding via the award of a consolidator grant, and BV has been supported by the ERC grant âCosmic Dawnâ.This is the final published version. It originally appeared in MNRAS at http://www.mnras.org/content/442/4/3454.full
A Joint Sunyaev-Zel'dovich Effect and X-ray Analysis of Abell 3667
We present a 40GHz (7.5 mm) raster scan image of a 3.6x2 degree region
centered on the low redshift (z=0.055) cluster of galaxies Abell 3667. The
cluster was observed during the Antarctic winter of 1999 using the Corona
instrument (15.7' FWHM beam) on the Viper Telescope at the South Pole. The
Corona image of A3667 is one of the first direct (i.e. rather than
interferometer) thermal Sunyaev-Zel'dovich effect images of a low redshift
cluster. The brightness temperature decrement at the X-ray centroid (20h 12m
28.9s, -56 49 51 J2000) was measured to be . We
have used the 40GHz map of A3667 in conjunction with a deep ROSAT PSPC (X-ray)
image of the cluster, to make a measurement of the Hubble Constant. We find
km s Mpc (68% confidence interval). Our
calculation assumes that the cluster can be described using an
isothermal, tri-axial ellipsoidal, -model and includes several new
analysis techniques including an automated method to remove point sources from
X-ray images with variable point spread functions, and an efficient method for
determining the errors in multi-parameter maximum likelihood analyzes. The
large errors on the measurement are primarily due to the statistical
noise in the Corona image. We plan to increase the precision of our measurement
by including additional clusters in our analysis and by increasing the
sensitivity of the Viper SZE maps.Comment: 15 pages, 4 figures, submitted to ApJ (count rate units corrected in
Table 1 and Figure 4
The MUSE Hubble Ultra Deep Field Survey X. Ly Equivalent Widths at
We present rest-frame Ly equivalent widths (EW) of 417 Ly
emitters (LAEs) detected with Multi Unit Spectroscopic Explorer (MUSE) on the
Very Large Telescope (VLT) at in the Hubble Ultra Deep Field.
Based on the deep MUSE spectroscopy and ancillary Hubble Space Telescope (HST)
photometry data, we carefully measured EW values taking into account extended
Ly emission and UV continuum slopes (). Our LAEs reach
unprecedented depths, both in Ly luminosities and UV absolute
magnitudes, from log(/erg s) 41.0 to 43.0 and
from Muv -16 to -21 (0.01-1.0 ). The EW values span the
range of 5 to 240 \AA\ or larger, and their distribution can be well
fitted by an exponential law exp(EW/). Owing to
the high dynamic range in Muv, we find that the scale factor, ,
depends on Muv in the sense that including fainter Muv objects increases
, i.e., the Ando effect. The results indicate that selection
functions affect the EW scale factor. Taking these effects into account, we
find that our values are consistent with those in the literature
within uncertainties at at a given threshold of Muv
and . Interestingly, we find 12 objects with EW \AA\
above uncertainties. Two of these 12 LAEs show signatures of merger
or AGN activity: the weak CIV emission line. For the remaining
10 very large EW LAEs, we find that the EW values can be reproduced by young
stellar ages ( Myr) and low metallicities ( ). Otherwise, at least part of the Ly emission in these LAEs
needs to arise from anisotropic radiative transfer effects, fluorescence by
hidden AGN or quasi-stellar object activity, or gravitational cooling.Comment: 22 pages, 12 figures, 9 tables, accepted for publication in A&A (MUSE
UDF Series Paper X
Possible Signatures of a Cold-Flow Disk from MUSE using a z=1 galaxy--quasar pair towards SDSSJ1422-0001
We use a background quasar to detect the presence of circum-galactic gas
around a low-mass star forming galaxy. Data from the new Multi Unit
Spectroscopic Explorer (MUSE) on the VLT show that the host galaxy has a
dust-corrected star-formation rate (SFR) of 4.70.2 Msun/yr, with no
companion down to 0.22 Msun/yr (5 ) within 240 kpc (30"). Using a
high-resolution spectrum (UVES) of the background quasar, which is fortuitously
aligned with the galaxy major axis (with an azimuth angle of only
), we find, in the gas kinematics traced by low-ionization lines,
distinct signatures consistent with those expected for a "cold flow disk"
extending at least 12 kpc (). We estimate the mass accretion
rate to be at least two to three times larger than the SFR,
using the geometric constraints from the IFU data and the HI column density of
obtained from a {\it HST}/COS NUV spectrum. From
a detailed analysis of the low-ionization lines (e.g. ZnII, CrII, TiII, MnII,
SiII), the accreting material appears to be enriched to about 0.4
(albeit with large uncertainties: ), which is
comparable to the galaxy metallicity (), implying a
large recycling fraction from past outflows. Blue-shifted MgII and FeII
absorptions in the galaxy spectrum from the MUSE data reveal the presence of an
outflow. The MgII and FeII doublet ratios indicate emission infilling due to
scattering processes, but the MUSE data do not show any signs of fluorescent
FeII* emission.Comment: 17 pages, 11 figures, in press (ApJ), minor edits after the proofs.
Data available at http://muse-vlt.eu/science/j1422
How neutral is the intergalactic medium surrounding the redshift z=7.085 quasar ULAS J1120+0641?
The quasar ULAS J1120+0641 at redshift z=7.085 has a highly ionised near zone
which is smaller than those around quasars of similar luminosity at z~6. The
spectrum also exhibits evidence for a damping wing extending redward of the
systemic Lya redshift. We use radiative transfer simulations in a cosmological
context to investigate the implications for the ionisation state of the
inhomogeneous IGM surrounding this quasar. Our simulations show that the
transmission profile is consistent with an IGM in the vicinity of the quasar
with a volume averaged HI fraction of f_HI>0.1 and that ULAS J1120+0641 has
been bright for 10^6--10^7 yr. The observed spectrum is also consistent with
smaller IGM neutral fractions, f_HI ~ 10^-3--10-4, if a damped Lya system in an
otherwise highly ionised IGM lies within 5 proper Mpc of the quasar. This is,
however, predicted to occur in only ~5 per cent of our simulated sight-lines
for a bright phase of 10^6--10^7 yr. Unless ULAS J1120+0641 grows during a
previous optically obscured phase, the low age inferred for the quasar adds to
the theoretical challenge of forming a 2x10^9 M_sol black hole at this high
redshift.Comment: 5 pages, 4 figures, accepted to MNRAS letter
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