42 research outputs found
BiDi screen: a thin, depth-sensing LCD for 3D interaction using light fields
We transform an LCD into a display that supports both 2D multi-touch and unencumbered 3D gestures. Our BiDirectional (BiDi) screen, capable of both image capture and display, is inspired by emerging LCDs that use embedded optical sensors to detect multiple points of contact. Our key contribution is to exploit the spatial light modulation capability of LCDs to allow lensless imaging without interfering with display functionality. We switch between a display mode showing traditional graphics and a capture mode in which the backlight is disabled and the LCD displays a pinhole array or an equivalent tiled-broadband code. A large-format image sensor is placed slightly behind the liquid crystal layer. Together, the image sensor and LCD form a mask-based light field camera, capturing an array of images equivalent to that produced by a camera array spanning the display surface. The recovered multi-view orthographic imagery is used to passively estimate the depth of scene points. Two motivating applications are described: a hybrid touch plus gesture interaction and a light-gun mode for interacting with external light-emitting widgets. We show a working prototype that simulates the image sensor with a camera and diffuser, allowing interaction up to 50 cm in front of a modified 20.1 inch LCD.National Science Foundation (U.S.) (Grant CCF-0729126)Alfred P. Sloan Foundatio
The Star Cluster Population of M51: II. Age distribution and relations among the derived parameters
We use archival {\it Hubble Space Telescope} observations of broad-band
images from the ultraviolet (F255W-filter) through the near infrared (NICMOS
F160W-filter) to study the star cluster population of the interacting spiral
galaxy M51. We obtain age, mass, extinction, and effective radius estimates for
1152 star clusters in a region of kpc centered on the
nucleus and extending into the outer spiral arms. In this paper we present the
data set and exploit it to determine the age distribution and relationships
among the fundamental parameters (i.e. age, mass, effective radius). Using this
dataset we find: {\it i}) that the cluster formation rate seems to have had a
large increase 50-70 Myr ago, which is coincident with the suggested
{\it second passage} of its companion, NGC 5195, {\it ii}) a large number of
extremely young ( 10 Myr) star clusters, which we interpret as a population
of unbound clusters of which a large majority will disrupt within the next
10 Myr, and {\it iii)} that the distribution of cluster sizescan be well
approximated by a power-law with exponent, , which is
very similar to that of Galactic globular clusters, indicating that cluster
disruption is largely independent of cluster radius. In addition, we have used
this dataset to search for correlations among the derived parameters. In
particular, we do not find any strong trends between the age and mass, mass and
effective radius, nor between the galactocentric distance and effective radius.
There is, however, a strong correlation between the age of a cluster and its
extinction, with younger clusters being more heavily reddened than older
clusters.Comment: 21 pages, 20 figures, accepted A&
Abundance and evolution of galaxy clusters in cosmological models with massive neutrino
The time evolution of the number density of galaxy clusters and their mass
and temperature functions are used to constrain cosmological parameters in the
spatially flat dark matter models containing a fraction of hot particles
(massive neutrino) additional to cold and baryonic matter. We test the modified
MDM models with cosmic gravitational waves and show that they neither pass the
cluster evolution test nor reproduce the observed height of the first acoustic
peak in spectrum, and therefore should be ruled out. The models
with a non-zero cosmological constant are in better agreement with
observations. We estimate the free cosmological parameters in MDM with
a negligible abundance of gravitational waves, and find that within the
parameter ranges , , (i) the value of
is strongly affected by a small fraction of hot dark matter,
:
( CL), and (ii) the redshift evolution of galaxy clusters alone
reveals the following explicit correlation between and
: . The present accuracy of
observational data allows only to bound the fraction of hot matter, (the number of massive neutrino species remains undelimited, ).Comment: 9 pages, 7 figures, submitted in A&
Dark matter and structure formation a review
This paper provides a review of the variants of dark matter which are thought
to be fundamental components of the universe and their role in origin and
evolution of structures and some new original results concerning improvements
to the spherical collapse model. In particular, I show how the spherical
collapse model is modified when we take into account dynamical friction and
tidal torques
Detection of intergalactic red-giant-branch stars in the Virgo cluster
It has been suspected for nearly 50 years that clusters of galaxies contain a
population of intergalactic stars, ripped from galaxies during cluster
formation or when the galaxies' orbits take them through the cluster center.
Support for the existence of such a population of free-floating stars comes
from measurements of the diffuse light in clusters, and from recent detections
of planetary nebulae with positions and/or velocities far removed from any
observed cluster galaxy. But estimates for the mass of the diffuse population
and its distribution relative to the galaxies are still highly uncertain. Here
we report the direct detection of intergalactic stars in deep images of a blank
field in the Virgo Cluster. The data suggest that approximately 10% of the
stellar mass of the cluster is in intergalactic stars. We observe a relatively
homogeneous distribution of stars, with evidence of a slight gradient toward
M87.Comment: Accepted for publication in Nature. 10 pages, 2 postscript figures
included. Uses nature.sty and astrobib.sty. (Astrobib is available from
http://www.stsci.edu/software/TeX.html.
Dwarf Elliptical Galaxies
Dwarf elliptical (dE) galaxies, with blue absolute magnitudes typically
fainter than , are the most numerous type of galaxy in the nearby
universe. Tremendous advances have been made over the past several years in
delineating the properties of both Local Group satellite dE's and the large dE
populations of nearby clusters. We review some of these advances, with
particular attention to how well currently available data can constrain 1)
models for the formation of dE's, 2) the physical and evolutionary connections
between different types of galaxies (nucleated and nonnucleated dE's, compact
E's, irregulars, and blue compact dwarfs) that overlap in the same portion of
the mass-spectrum of galaxies, 3) the contribution of dE's to the galaxy
luminosity functions in clusters and the field, 4) the star-forming histories
of dE's and their possible contribution to faint galaxy counts, and 5) the
clustering properties of dE's. In addressing these issues, we highlight the
extent to which selection effects temper these constraints, and outline areas
where new data would be particularly valuable.Comment: 63p, uuencoded compressed postscript, 2/8 figs included, A&A Review
in press, request paper copies from [email protected], STScI 86
The Seventeenth Data Release of the Sloan Digital Sky Surveys: Complete Release of MaNGA, MaStar and APOGEE-2 Data
This paper documents the seventeenth data release (DR17) from the Sloan Digital Sky Surveys; the fifth and final release from the fourth phase (SDSS-IV). DR17 contains the complete release of the Mapping Nearby Galaxies at Apache Point Observatory (MaNGA) survey, which reached its goal of surveying over 10,000 nearby galaxies. The complete release of the MaNGA Stellar Library (MaStar) accompanies this data, providing observations of almost 30,000 stars through the MaNGA instrument during bright time. DR17 also contains the complete release of the Apache Point Observatory Galactic Evolution Experiment 2 (APOGEE-2) survey which publicly releases infra-red spectra of over 650,000 stars. The main sample from the Extended Baryon Oscillation Spectroscopic Survey (eBOSS), as well as the sub-survey Time Domain Spectroscopic Survey (TDSS) data were fully released in DR16. New single-fiber optical spectroscopy released in DR17 is from the SPectroscipic IDentification of ERosita Survey (SPIDERS) sub-survey and the eBOSS-RM program. Along with the primary data sets, DR17 includes 25 new or updated Value Added Catalogs (VACs). This paper concludes the release of SDSS-IV survey data. SDSS continues into its fifth phase with observations already underway for the Milky Way Mapper (MWM), Local Volume Mapper (LVM) and Black Hole Mapper (BHM) surveys
The 16th Data Release of the Sloan Digital Sky Surveys: First Release from the APOGEE-2 Southern Survey and Full Release of eBOSS Spectra
This paper documents the 16th data release (DR16) from the Sloan Digital Sky Surveys (SDSS), the fourth and penultimate from the fourth phase (SDSS-IV). This is the first release of data from the Southern Hemisphere survey of the Apache Point Observatory Galactic Evolution Experiment 2 (APOGEE-2); new data from APOGEE-2 North are also included. DR16 is also notable as the final data release for the main cosmological program of the Extended Baryon Oscillation Spectroscopic Survey (eBOSS), and all raw and reduced spectra from that project are released here. DR16 also includes all the data from the Time Domain Spectroscopic Survey and new data from the SPectroscopic IDentification of ERosita Survey programs, both of which were co-observed on eBOSS plates. DR16 has no new data from the Mapping Nearby Galaxies at Apache Point Observatory (MaNGA) survey (or the MaNGA Stellar Library "MaStar"). We also preview future SDSS-V operations (due to start in 2020), and summarize plans for the final SDSS-IV data release (DR17)
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The 16th Data Release of the Sloan Digital Sky Surveys: First Release from the APOGEE-2 Southern Survey and Full Release of eBOSS Spectra
This paper documents the 16th data release (DR16) from the Sloan Digital Sky Surveys (SDSS), the fourth and penultimate from the fourth phase (SDSS-IV). This is the first release of data from the Southern Hemisphere survey of the Apache Point Observatory Galactic Evolution Experiment 2 (APOGEE-2); new data from APOGEE-2 North are also included. DR16 is also notable as the final data release for the main cosmological program of the Extended Baryon Oscillation Spectroscopic Survey (eBOSS), and all raw and reduced spectra from that project are released here. DR16 also includes all the data from the Time Domain Spectroscopic Survey and new data from the SPectroscopic IDentification of ERosita Survey programs, both of which were co-observed on eBOSS plates. DR16 has no new data from the Mapping Nearby Galaxies at Apache Point Observatory (MaNGA) survey (or the MaNGA Stellar Library "MaStar"). We also preview future SDSS-V operations (due to start in 2020), and summarize plans for the final SDSS-IV data release (DR17)
The 16th Data Release of the Sloan Digital Sky Surveys : First Release from the APOGEE-2 Southern Survey and Full Release of eBOSS Spectra
This paper documents the 16th data release (DR16) from the Sloan Digital Sky Surveys (SDSS), the fourth and penultimate from the fourth phase (SDSS-IV). This is the first release of data from the Southern Hemisphere survey of the Apache Point Observatory Galactic Evolution Experiment 2 (APOGEE-2); new data from APOGEE-2 North are also included. DR16 is also notable as the final data release for the main cosmological program of the Extended Baryon Oscillation Spectroscopic Survey (eBOSS), and all raw and reduced spectra from that project are released here. DR16 also includes all the data from the Time Domain Spectroscopic Survey and new data from the SPectroscopic IDentification of ERosita Survey programs, both of which were co-observed on eBOSS plates. DR16 has no new data from the Mapping Nearby Galaxies at Apache Point Observatory (MaNGA) survey (or the MaNGA Stellar Library "MaStar"). We also preview future SDSS-V operations (due to start in 2020), and summarize plans for the final SDSS-IV data release (DR17).Peer reviewe