155 research outputs found
First Results from the Lyman Alpha Galaxies in the Epoch of Reionization (LAGER) Survey: Cosmological Reionization at z ~ 7
We present the first results from the ongoing LAGER project (Lyman Alpha
Galaxies in the Epoch of Reionization), which is the largest narrowband survey
for 7 galaxies to date. Using a specially built narrowband filter
NB964 for the superb large-area Dark-Energy Camera (DECam) on the NOAO/CTIO 4m
Blanco telescope, LAGER has collected 34 hours NB964 narrowband imaging data in
the 3 deg COSMOS field. We have identified 23 Lyman Alpha Emitter (LAE)
candidates at = 6.9 in the central 2-deg region, where DECam and public
COSMOS multi-band images exist. The resulting luminosity function can be
described as a Schechter function modified by a significant excess at the
bright end (4 galaxies with 10 erg
s). The number density at 10 erg
s is little changed from z= 6.6, while at fainter it is
substantially reduced. Overall, we see a fourfold reduction in Ly
luminosity density from = 5.7 to 6.9. Combined with a more modest evolution
of the continuum UV luminosity density, this suggests a factor of
suppression of Ly by radiative transfer through the 7
intergalactic medium (IGM). It indicates an IGM neutral fraction
0.4--0.6 (assuming Ly velocity offsets of 100-200 km s).
The changing shape of the Ly luminosity function between and supports the hypothesis of ionized bubbles in a patchy
reionization at 7.Comment: 7 pages, 3 figures (updated), 2 tables (updated), Accepted for
publication in ApJ Letter
Project Overview of the Beijing-Arizona Sky Survey
The Beijing-Arizona Sky Survey (BASS) is a wide-field two-band photometric
survey of the Northern Galactic Cap using the 90Prime imager on the 2.3 m Bok
telescope at Kitt Peak. It is a four-year collaboration between the National
Astronomical Observatory of China and Steward Observatory, the University of
Arizona, serving as one of the three imaging surveys to provide photometric
input catalogs for target selection of the Dark Energy Spectroscopic Instrument
(DESI) project. BASS will take up to 240 dark/grey nights to cover an area of
about 5400 deg in the and bands. The 5 limiting AB
magnitudes for point sources in the two bands, corrected for the Galactic
extinction, are 24.0 and 23.4 mag, respectively. BASS, together with other DESI
imaging surveys, will provide unique science opportunities that cover a wide
range of topics in both Galactic and extragalactic astronomy.Comment: 10 pages, submitted to PAS
First Spectroscopic Confirmations of z ~ 7.0 Lya Emitting Galaxies in the LAGER Survey
Narrowband imaging is a highly successful approach for finding large numbers
of high redshift Lya emitting galaxies (LAEs) up to z~6.6. However, at z>~7
there are as yet only 3 narrowband selected LAEs with spectroscopic
confirmations (two at z~6.9-7.0, one at z~7.3), which hinders extensive studies
on cosmic reionization and galaxy evolution at this key epoch. We have selected
23 candidate z~6.9 LAEs in COSMOS field with the large area narrowband survey
LAGER (Lyman-Alpha Galaxies at the End of Reionization). In this work we
present spectroscopic followup observations of 12 candidates using IMACS on
Magellan. For 9 of these, the observations are sufficiently deep to detect the
expected lines. Lya emission lines are identified in six sources (yielding a
success rate of 2/3), including 3 luminous LAEs with Lya luminosities of L(Lya)
~ 10^{43.5} erg/s, the highest among known spectroscopically confirmed galaxies
at >~7.0. This triples the sample size of spectroscopically confirmed
narrowband selected LAEs at z>~7, and confirms the bright end bump in the Lya
luminosity function we previously derived based on the photometric sample,
supporting a patchy reionization scenario. Two luminous LAEs appear physically
linked with projected distance of 1.1 pMpc and velocity difference of ~ 170
km/s. They likely sit in a common ionized bubble produced by themselves or with
close neighbors, which reduces the IGM attenuation of Lya. A tentative narrow
NV1240 line is seen in one source, hinting at activity of a central
massive black hole with metal rich line emitting gas.Comment: 6 pages, 3 figures, 2 tables, accepted by ApJ
The First Data Release of the Beijing-Arizona Sky Survey
The Beijing-Arizona Sky Survey (BASS) is a new wide-field legacy imaging
survey in the northern Galactic cap using the 2.3m Bok telescope. The survey
will cover about 5400 deg in the and bands, and the expected
5 depths (corrected for the Galactic extinction) in the two bands are
24.0 and 23.4 mag, respectively. BASS started observations in January 2015, and
has completed about 41% of the whole area as of July 2016. The first data
release contains both calibrated images and photometric catalogs obtained in
2015 and 2016. The depths of single-epoch images in the two bands are 23.4 and
22.9 mag, and the full depths of three epochs are about 24.1 and 23.5 mag,
respectively.Comment: 16 pages, published by A
An Essential Role for RIG-I in Toll-like Receptor-Stimulated Phagocytosis
SummaryRetinoic acid-inducible gene-I (RIG-I) plays an important role in antiviral response by recognizing double-stranded RNA. Here we demonstrate an unanticipated role of RIG-I in Toll-like receptor (TLR)-stimulated phagocytosis. Stimulation with lipopolysaccharide (LPS), a ligand of TLR4, induced the expression of RIG-I in macrophages. Depletion of RIG-I by RNAi or gene targeting inhibited the LPS-induced phagocytosis of bacteria. Cellular processes involved in phagocytosis, such as small GTPase Cdc42/Rac1 activation, actin polymerization, and actin-regulator Arp2/3 recruitment, were also impaired in RIG-I-deficient macrophages activated by LPS. Moreover, RIG-I−/− mice were found to be more susceptible to infection with Escherichia coli as compared to wild-type mice. Thus, the regulatory functions of RIG-I are strikingly broad, including a role not only in antiviral responses but in antibacterial responses as well
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