260 research outputs found
Aphasia Centers in North America: A Survey
Aphasia management has traditionally targeted language impairments. However, programs have begun to address other consequences of aphasia such as social isolation, well-being, or participation. One means of addressing these consequences is via an “aphasia center.” An online survey was developed and distributed in order to learn more about aphasia centers in North America. Thirty one respondents provided information (e.g. demographics, mission/goals, admission and discharge criteria, funding sources, programming). The data were analyzed via frequency counts and charts, as well as qualitatively by identifying key themes that helped to describe characteristics of aphasia centers
APOGEE Kinematics I: Overview of the Kinematics of the Galactic Bulge as Mapped by APOGEE
We present the stellar kinematics across the Galactic bulge and into the disk
at positive longitudes from the SDSS-III APOGEE spectroscopic survey of the
Milky Way. APOGEE includes extensive coverage of the stellar populations of the
bulge along the mid-plane and near-plane regions. From these data, we have
produced kinematic maps of 10,000 stars across longitudes 0 deg < l < 65 deg,
and primarily across latitudes of |b| < 5 deg in the bulge region. The APOGEE
data reveal that the bulge is cylindrically rotating across all latitudes and
is kinematically hottest at the very centre of the bulge, with the smallest
gradients in both kinematic and chemical space inside the inner-most region
(l,|b|) < (5,5) deg. The results from APOGEE show good agreement with data from
other surveys at higher latitudes and a remarkable similarity to the rotation
and dispersion maps of barred galaxies viewed edge on. The thin bar that is
reported to be present in the inner disk within a narrow latitude range of |b|
< 2 deg appears to have a corresponding signature in [Fe/H] and [alpha/Fe].
Stars with [Fe/H] > -0.5 have dispersion and rotation profiles that are similar
to that of N-body models of boxy/peanut bulges. There is a smooth kinematic
transition from the thin bar and boxy bulge (l,|b|) < (15,12) deg out into the
disk for stars with [Fe/H] > -1.0, and the chemodynamics across (l,b) suggests
the stars in the inner Galaxy with [Fe/H] > -1.0 have an origin in the disk.Comment: Accepted by ApJ 15 December 201
The Sloan Digital Sky Survey Reverberation Mapping Project: Ensemble Spectroscopic Variability of Quasar Broad Emission Lines
We explore the variability of quasars in the MgII and Hbeta broad emission
lines and UV/optical continuum emission using the Sloan Digital Sky Survey
Reverberation Mapping project (SDSS-RM). This is the largest spectroscopic
study of quasar variability to date: our study includes 29 spectroscopic epochs
from SDSS-RM over months, containing 357 quasars with MgII and 41 quasars
with Hbeta . On longer timescales, the study is also supplemented with
two-epoch data from SDSS-I/II. The SDSS-I/II data include an additional
quasars with MgII and 572 quasars with Hbeta. The MgII emission line is
significantly variable ( 10% on 100-day timescales), a necessary
prerequisite for its use for reverberation mapping studies. The data also
confirm that continuum variability increases with timescale and decreases with
luminosity, and the continuum light curves are consistent with a damped
random-walk model on rest-frame timescales of days. We compare the
emission-line and continuum variability to investigate the structure of the
broad-line region. Broad-line variability shows a shallower increase with
timescale compared to the continuum emission, demonstrating that the broad-line
transfer function is not a -function. Hbeta is more variable than MgII
(roughly by a factor of ), suggesting different excitation mechanisms,
optical depths and/or geometrical configuration for each emission line. The
ensemble spectroscopic variability measurements enabled by the SDSS-RM project
have important consequences for future studies of reverberation mapping and
black hole mass estimation of quasars.Comment: 20 pages, 25 figures. ApJ accepted: minor revisions following referee
repor
High-resolution, H band Spectroscopy of Be Stars with SDSS-III/APOGEE: I. New Be Stars, Line Identifications, and Line Profiles
APOGEE has amassed the largest ever collection of multi-epoch,
high-resolution (R~22,500), H-band spectra for B-type emission line (Be) stars.
The 128/238 APOGEE Be stars for which emission had never previously been
reported serve to increase the total number of known Be stars by ~6%. We focus
on identification of the H-band lines and analysis of the emission peak
velocity separations (v_p) and emission peak intensity ratios (V/R) of the
usually double-peaked H I and non-hydrogen emission lines. H I Br11 emission is
found to preferentially form in the circumstellar disks at an average distance
of ~2.2 stellar radii. Increasing v_p toward the weaker Br12--Br20 lines
suggests these lines are formed interior to Br11. By contrast, the observed IR
Fe II emission lines present evidence of having significantly larger formation
radii; distinctive phase lags between IR Fe II and H I Brackett emission lines
further supports that these species arise from different radii in Be disks.
Several emission lines have been identified for the first time including
~16895, a prominent feature in the spectra for almost a fifth of the sample
and, as inferred from relatively large v_p compared to the Br11-Br20, a tracer
of the inner regions of Be disks. Unlike the typical metallic lines observed
for Be stars in the optical, the H-band metallic lines, such as Fe II 16878,
never exhibit any evidence of shell absorption, even when the H I lines are
clearly shell-dominated. The first known example of a quasi-triple-peaked Br11
line profile is reported for HD 253659, one of several stars exhibiting intra-
and/or extra-species V/R and radial velocity variation within individual
spectra. Br11 profiles are presented for all discussed stars, as are full
APOGEE spectra for a portion of the sample.Comment: accepted in A
Chemical abundance gradients from open clusters in the Milky Way disk: results from the APOGEE survey
Metallicity gradients provide strong constraints for understanding the
chemical evolution of the Galaxy. We report on radial abundance gradients of
Fe, Ni, Ca, Si, and Mg obtained from a sample of 304 red-giant members of 29
disk open clusters, mostly concentrated at galactocentric distances between ~8
- 15 kpc, but including two open clusters in the outer disk. The observations
are from the APOGEE survey. The chemical abundances were derived automatically
by the ASPCAP pipeline and these are part of the SDSS III Data Release 12. The
gradients, obtained from least squares fits to the data, are relatively flat,
with slopes ranging from -0.026 to -0.033 dex/kpc for the alpha-elements [O/H],
[Ca/H], [Si/H] and [Mg/H] and -0.035 dex/kpc and -0.040 dex/kpc for [Fe/H] and
[Ni/H], respectively. Our results are not at odds with the possibility that
metallicity ([Fe/H]) gradients are steeper in the inner disk (R_GC ~7 - 12 kpc)
and flatter towards the outer disk. The open cluster sample studied spans a
significant range in age. When breaking the sample into age bins, there is some
indication that the younger open cluster population in our sample (log age <
8.7) has a flatter metallicity gradient when compared with the gradients
obtained from older open clusters.Comment: 4 pages, 3 figures, To appear in Astronomische Nachrichten, special
issue "Reconstruction the Milky Way's History: Spectroscopic surveys,
Asteroseismology and Chemo-dynamical models", Guest Editors C. Chiappini, J.
Montalb\'an, and M. Steffen, AN 2016 (in press)
Update on the Nature of Virgo Overdensity
We use the Eighth Data Release of Sloan Digital Sky Survey (SDSS DR8) catalog
with its additional sky coverage of the southern Galactic hemisphere, to
measure the extent and study the nature of the Virgo Overdensity (VOD; Juric et
al. 2008). The data show that the VOD extends over no less than 2000 deg^2,
with its true extent likely closer to 3000 deg^2. We test whether the VOD can
be attributed to a tilt in the stellar halo ellipsoid with respect to the plane
of the Galactic disk and find that the observed symmetry of the north-south
Galactic hemisphere star counts excludes this possibility. We argue that the
Virgo Overdensity, in spite of its wide area and cloud-like appearance, is
still best explained by a minor merger. Its appearance and position is
qualitatively similar to a near perigalacticon merger event and, assuming that
the VOD and the Virgo Stellar Stream share the same progenitor, consistent with
the VSS orbit determined by Casetti-Dinescu et al. (2009).Comment: 9 pages,6 figures; accepted for publication in A
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