40,403 research outputs found
Inferences on the Timeline of Reionization at z~8 From the KMOS Lens-Amplified Spectroscopic Survey
Detections and non-detections of Lyman alpha (Ly) emission from
galaxies ( Gyr after the Big Bang) can be used to measure the timeline of
cosmic reionization. Of key interest to measuring reionization's mid-stages,
but also increasing observational challenge, are observations at z > 7, where
Ly redshifts to near infra-red wavelengths. Here we present a search
for z > 7.2 Ly emission in 53 intrinsically faint Lyman Break Galaxy
candidates, gravitationally lensed by massive galaxy clusters, in the KMOS
Lens-Amplified Spectroscopic Survey (KLASS). With integration times of ~7-10
hours, we detect no Ly emission with S/N>5 in our sample. We determine
our observations to be 80% complete for 5 spatially and spectrally
unresolved emission lines with integrated line flux erg
s cm. We define a photometrically selected sub-sample of 29
targets at , with a median 5 Ly EW limit of 58A.
We perform a Bayesian inference of the average intergalactic medium (IGM)
neutral hydrogen fraction using their spectra. Our inference accounts for the
wavelength sensitivity and incomplete redshift coverage of our observations,
and the photometric redshift probability distribution of each target. These
observations, combined with samples from the literature, enable us to place a
lower limit on the average IGM neutral hydrogen fraction of at z ~ 8, providing further evidence of rapid reionization
at z~6-8. We show that this is consistent with reionization history models
extending the galaxy luminosity function to , with
low ionizing photon escape fractions, .Comment: Accepted for publication in MNRA
Lissitzky : new materialism and diagrammatic living
Lissitsky\u27s spatial and architectural work anticipates the contemporary fascination with expanded fields of activity that have resulted in transdisciplinary approaches to research and the role of practice-led research. This paper will discuss Lissitzky\u27s suprematist perspective in relation to contemporary practices - under the rubric of the "diagram" - that re-imagine and enact the relationship between the built surround and embodied cognition. Lissitzky\u27s work will serve as the starting point for a discussion of contemporary practitioners and theorists working across philosophy, cognitive science and built environment in order to draw out, through the act of diagramming, life on new terms.<br /
A sample of Seyfert-2 galaxies with ultra-luminous galaxy-wide NLRs -- Quasar light echos?
We report the discovery of Seyfert-2 galaxies in SDSS-DR8 with galaxy-wide,
ultra-luminous narrow-line regions (NLRs) at redshifts z=0.2-0.6. With a space
density of 4.4 per cubic Gpc at z~0.3, these "Green Beans" (GBs) are amongst
the rarest objects in the Universe. We are witnessing an exceptional and/or
short-lived phenomenon in the life cycle of AGN. The main focus of this paper
is on a detailed analysis of the GB prototype galaxy J2240-0927 (z=0.326). Its
NLR extends over 26x44 kpc and is surrounded by an extended narrow-line region
(ENLR). With a total [OIII]5008 luminosity of (5.7+/-0.9)x10e43 erg/s, this is
one of the most luminous NLR known around any type-2 galaxy. Using VLT/XSHOOTER
we show that the NLR is powered by an AGN, and we derive resolved extinction,
density and ionization maps. Gas kinematics is disturbed on a global scale, and
high velocity outflows are absent or faint. This NLR is unlike any other NLR or
extended emission line region (EELR) known. Spectroscopy with Gemini/GMOS
reveals extended, high luminosity [OIII] emission also in other GBs. WISE
24micron luminosities are 5-50 times lower than predicted by the [OIII] fluxes,
suggesting that the NLRs reflect earlier, very active quasar states that have
strongly subsided in less than a galaxies' light crossing time. These light
echos are about 100 times more luminous than any other such light echo known to
date. X-ray data are needed for photo-ionization modeling and to verify the
light echos.Comment: This is an update of our previous submission (1211.7098). Apart from
layout it is identical to the publication in ApJ. Compared to v1 (1211.7098)
type settings and language errors have been corrected. We also added 4 more
redshifts, confirming 3 sources (objects #002, #017, #21) and rejecting one
(#020, low-z HII region
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