1,756 research outputs found
3D scene modeling and understanding from image sequences
A new method for 3D modeling is proposed, which generates a content-based 3D mosaic (CB3M) representation for long video sequences of 3D, dynamic urban scenes captured by a camera on a mobile platform. In the first phase, a set of parallel-perspective (pushbroom) mosaics with varying viewing directions is generated to capture both the 3D and dynamic aspects of the scene under the camera coverage. In the second phase, a unified patch-based stereo matching algorithm is applied to extract parametric representations of the color, structure and motion of the dynamic and/or 3D objects in urban scenes, where a lot of planar surfaces exist. Multiple pairs of stereo mosaics are used for facilitating reliable stereo matching, occlusion handling, accurate 3D reconstruction and robust moving target detection. The outcome of this phase is a CB3M representation, which is a highly compressed visual representation for a dynamic 3D scene, and has object contents of both 3D and motion information. In the third phase, a multi-layer based scene understanding algorithm is proposed, resulting in a planar surface model for higher-level object representations. Experimental results are given for both simulated and several different real video sequences of large-scale 3D scenes to show the accuracy and effectiveness of the representation. We also show the patch-based stereo matching algorithm and the CB3M representation can be generalized to 3D modeling with perspective views using either a single camera or a stereovision head on a ground mobile platform or a pedestrian. Applications of the proposed method include airborne or ground video surveillance, 3D urban scene modeling, traffic survey, transportation planning and the visual aid for perception and navigation of blind people
Herbig-Haro flows in B335
We have observed optical (Halpha and [SII]) and near-IR (S(1) line of H2)
deep fields and taken optical spectra using the 2.56m NOT, as well as a near-UV
deep field (U band) using the 3.58m NTT. In addition we present new SPITZER
(IRAC and MIPS) mid-IR observations. We use previous Halpha and S(1)
observations taken 15 and 9 years earlier to make proper motion maps. We then
investigate the shock physics by matching our spectra with planar shock models.
We discover six new HH objects in B335. From proper motions we find an
optically bright, roughly E-W oriented group with high space velocities
(200-280 km/s) and a near-IR bright, slower group (15-75 km/s) moving to the
ESE. We also find a system of at least 15 H2 knots in the western lobe. This
(WNW) counterflow suggests the possibility of a binary outflow source, giving
rise to two outflow axes with slightly different orientations. We find that the
E-W flow is symmetrical with evidence for two outbursts. We make the first
detection of [OI] 6300/63 in HH119 B and Hbeta in HH119 A and B and find their
extinctions to be AV~1.4 and 4.4, respectively. HH119 A is found to expand much
faster than expected from linear expansion with distance from the outflow
source. Using planar shock models we find shock velocities of ~60 km/s (A) and
~35 km/s (B and C). This agrees with A being of higher excitation than B and C.
In our U image we detect three of the HH objects and propose that the emission
arise from the [OII] 3728 line and the blue continuum. New SPITZER observations
show most of the HH objects at 4.5 micron and a E-W elongated hour-glass shaped
structure at the outflow source. Even at 24 micron it is not clear whether most
of the light is direct or reflected.Comment: 23 pages, 15 figures, accepted in A&
HST/NICMOS observations of the GLIMPSE9 stellar cluster
We present HST/NICMOS photometry, and low-resolution K-band spectra of the
GLIMPSE9 stellar cluster. The newly obtained color-magnitude diagram shows a
cluster sequence with H-Ks =1 mag, indicating an interstellar extinction
Aks=1.6\pm0.2 mag. The spectra of the three brightest stars show deep CO
band-heads, which indicate red supergiants with spectral type M1-M2. Two 09-B2
supergiants are also identified, which yield a spectrophotometric distance of
4.2\pm0.4 kpc. Presuming that the population is coeval, we derive an age
between 15 and 27 Myr, and a total cluster mass of 1600\pm400 Msun, integrated
down to 1 Msun. In the vicinity of GLIMPSE9 are several HII regions and SNRs,
all of which (including GLIMPSE 9) are probably associated with a giant
molecular cloud (GMC) in the inner galaxy. GLIMPSE9 probably represents one
episode of massive star formation in this GMC. We have identified several other
candidate stellar clusters of the same complex.Comment: 13 pages, 14 figures. accepted for publication in ApJ. A version with
high-resolution figures can be found at the following location
ftp://ftp.rssd.esa.int/pub/mmessine/ms.pdf New version with updated
reference
The Massive End of the Stellar Mass Function
We derive average flux corrections to the \texttt{Model} magnitudes of the
Sloan Digital Sky Survey (SDSS) galaxies by stacking together mosaics of
similar galaxies in bins of stellar mass and concentration. Extra flux is
detected in the outer low surface brightness part of the galaxies, leading to
corrections ranging from 0.05 to 0.32 mag for the highest stellar mass
galaxies. We apply these corrections to the MPA-JHU (Max-Planck Institute for
Astrophysics - John Hopkins University) stellar masses for a complete sample of
half a million galaxies from the SDSS survey to derive a corrected galaxy
stellar mass function at in the stellar mass range
. We find that the flux corrections and the use
of the MPA-JHU stellar masses have a significant impact on the massive end of
the stellar mass function, making the slope significantly shallower than that
estimated by Li \& White (2009), but steeper than derived by Bernardi et al.
(2013). This corresponds to a mean comoving stellar mass density of galaxies
with stellar masses that is a factor of 3.36
larger than the estimate by Li \& White (2009), but is 43\% smaller than
reported by Bernardi et al. (2013).Comment: 11 pages, 8 figures, Accepted to MNRA
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