35 research outputs found
The QUEST RR Lyrae Survey: III. The Low Galactic Latitude Catalogue
We present results for the QUEST RR Lyrae Survey at low galactic latitude,
conducted entirely with observations obtained with the QUEST mosaic camera and
the 1.0/1.5m J\"urgen Stock Schmidt telescope at the National Observatory of
Venezuela. The survey spans an area of 476 sq. deg on the sky, with multi-epoch
observations in the V, R and I photometric bands for 6.5x10^6 stars in the
galactic latitude range 30<= b(deg) <=+25, in a direction close to the Galactic
Anticenter 190<= l(deg)<= 230. The variability survey has a typical number of
30 observations per object in V and I and ~25 in R, with up to ~120-150 epochs
in V and I and up to ~100 in R in the best sampled regions. The completeness
magnitudes of the survey are V=R=18.5 mag, and I=18.0 mag. We identified 211 RR
Lyrae stars, 160 bona fide stars of type ab and 51 candidates of type c, ours
being the first deep RR Lyrae survey conducted at low galactic latitude.The
completeness of the RR Lyrae survey was estimated in >95 per cent and ~85 per
cent for RRab and RRc stars respectively. Photometric metallicities were
computed based on the light curves and individual extinctions calculated from
minimum light colours for each RRab star. Distances were obtained with typical
errors ~7 per cent. The RR Lyrae survey simultaneously spans a large range of
heliocentric distances 0.5<= R_hel(kpc)<=40 and heights above the plane
-15<=z(kpc)<=+20, with well known completeness across the survey area, making
it an ideal set for studying the struc ture of the Galactic thick disk.Comment: 24 pages, 17 figures, 8 tables. Accepted for publication in MNRA
Kinematic identification of young nearby moving groups from a sample of chromospherically active stars in the RAVE catalog
The purpose of this study is the identification of young (
Myr), nearby ( pc) moving groups (YNMGs) through their
kinematic signature. YNMGs could be the result of the recent dispersal of young
embedded clusters, such that they still represent kinematically cold groups,
carrying the residual motion of their parental cloud. Using the fact that a
large number ( 14000) of the RAVE sources with evidence of chromospheric
activity, also present signatures of stellar youth, we selected a sample of
solar type sources with the highest probability of chromospheric activity to
look for common kinematics. We made use of radial velocity information from
RAVE and astrometric parameters from GAIA DR2 to construct a 6-dimension
position-velocity vector catalog for our full sample. We developed a method
based on the grouping of stars with similar orientation of their velocity
vectors, which we call the Cone Method Sampling. Using this method, we detected
646 sources with high significance in the velocity space, with respect to the
average orientation of artificial distributions made from a purely Gaussian
velocity ellipsoid with null vertex deviation. We compared this sample of
highly significant sources with a catalog of YNMGs reported in previous
studies, which yield 75 confirmed members. From the remaining sample, about 50%
of the sources have ages younger than 100 Myr, which indicate they are highly
probable candidates to be new members of identified or even other YNMGs in the
solar neighborhood.Comment: Complete tables (table 1 and table 2) will be available in the
electronic versio
A large-scale optical-near infrared survey for brown dwarfs and very low-mass stars in the Orion OB1 association
We report the initial results of a large-scale optical-near infrared survey
to extend the known young population of the entire Orion star-forming region
down to the substellar domain. Using deep optical I-band photometry and data
from the 2MASS survey, we selected candidates across ~14.8 deg^2 in the ~8 Myr
old Ori OB1a subassociation and over ~6.7 deg^2 in the Ori OB1b subassociation
(age ~3), with completeness down to 0.05Mo and 0.072Mo respectively. We
obtained low resolution optical spectra for a subsample of 4 candidates in Ori
OB1a and 26 in Ori OB1b; as a result we confirmed 3 new members in Ori OB1a,
one of which is substellar, and 19 new members in Ori OB1b, out of which 7 are
at the substellar limit and 5 are substellar. We looked into the presence of
accretion signatures by measuring the strength of the Ha line in emission.
Accordingly, we classified the new members as having Classical T-Tauri star
(CTTS) or Weak Lined T Tauri star-like (WTTS) nature. We found that all the new
members confirmed in Ori OB1a are WTTSs, while 39 +25/-22 % of the new members
in Ori OB1b exhibit CTTS-like behavior, suggestive of ongoing accretion from a
circum(sub)stellar disk. Additionally we found that none of the members
confirmed in OB1a show near-IR color excess while 38 +26/-21 % of OB1b members
show H-K color excess. These results are consistent with recent findings for
low mass young stars in Orion OB1. The similarity in CTTS-like properties and
near-IR excess across the substellar boundary gives support to the idea of a
common formation mechanism for low mass stars and at least the most massive
brown dwarfs. Finally, we remark the discovery of two new members classified as
CTTSs, both exhibiting W(Ha) < -140 A, suggesting significant ongoing
accretion.Comment: Accepted for publication in Astronomical Journa
The Fourteenth Data Release of the Sloan Digital Sky Survey: First Spectroscopic Data from the extended Baryon Oscillation Spectroscopic Survey and from the second phase of the Apache Point Observatory Galactic Evolution Experiment
The fourth generation of the Sloan Digital Sky Survey (SDSS-IV) has been in
operation since July 2014. This paper describes the second data release from
this phase, and the fourteenth from SDSS overall (making this, Data Release
Fourteen or DR14). This release makes public data taken by SDSS-IV in its first
two years of operation (July 2014-2016). Like all previous SDSS releases, DR14
is cumulative, including the most recent reductions and calibrations of all
data taken by SDSS since the first phase began operations in 2000. New in DR14
is the first public release of data from the extended Baryon Oscillation
Spectroscopic Survey (eBOSS); the first data from the second phase of the
Apache Point Observatory (APO) Galactic Evolution Experiment (APOGEE-2),
including stellar parameter estimates from an innovative data driven machine
learning algorithm known as "The Cannon"; and almost twice as many data cubes
from the Mapping Nearby Galaxies at APO (MaNGA) survey as were in the previous
release (N = 2812 in total). This paper describes the location and format of
the publicly available data from SDSS-IV surveys. We provide references to the
important technical papers describing how these data have been taken (both
targeting and observation details) and processed for scientific use. The SDSS
website (www.sdss.org) has been updated for this release, and provides links to
data downloads, as well as tutorials and examples of data use. SDSS-IV is
planning to continue to collect astronomical data until 2020, and will be
followed by SDSS-V.Comment: SDSS-IV collaboration alphabetical author data release paper. DR14
happened on 31st July 2017. 19 pages, 5 figures. Accepted by ApJS on 28th Nov
2017 (this is the "post-print" and "post-proofs" version; minor corrections
only from v1, and most of errors found in proofs corrected
Genome-wide analysis of differential transcriptional and epigenetic variability across human immune cell types
Abstract
Background
A healthy immune system requires immune cells that adapt rapidly to environmental challenges. This phenotypic plasticity can be mediated by transcriptional and epigenetic variability.
Results
We apply a novel analytical approach to measure and compare transcriptional and epigenetic variability genome-wide across CD14+CD16− monocytes, CD66b+CD16+ neutrophils, and CD4+CD45RA+ naïve T cells from the same 125 healthy individuals. We discover substantially increased variability in neutrophils compared to monocytes and T cells. In neutrophils, genes with hypervariable expression are found to be implicated in key immune pathways and are associated with cellular properties and environmental exposure. We also observe increased sex-specific gene expression differences in neutrophils. Neutrophil-specific DNA methylation hypervariable sites are enriched at dynamic chromatin regions and active enhancers.
Conclusions
Our data highlight the importance of transcriptional and epigenetic variability for the key role of neutrophils as the first responders to inflammatory stimuli. We provide a resource to enable further functional studies into the plasticity of immune cells, which can be accessed from:
http://blueprint-dev.bioinfo.cnio.es/WP10/hypervariability