10,091 research outputs found
A Multiwavelength Study of a Sample of 70 μm Selected Galaxies in the COSMOS Field. II. The Role of Mergers in Galaxy Evolution
We analyze the morphological properties of a large sample of 1503 70 μm selected galaxies in the COSMOS field spanning the redshift range 0.01 10^(12) L_☉) being up to ~50%. We also find that the fraction of spirals drops dramatically with L_(IR). Minor mergers likely play a role in boosting the infrared luminosity for sources with low luminosities (L_(IR) 1 being difficult to classify and subject to the effects of bandpass shifting; therefore, these numbers can only be considered lower limits. At z 1, the fraction of major mergers is lower, but is at least 30%-40% for ULIRGs. In a comparison of our visual classifications with several automated classification techniques we find general agreement; however, the fraction of identified mergers is underestimated due to automated classification methods being sensitive to only certain timescales of a major merger. Although the general morphological trends agree with what has been observed for local (U)LIRGs, the fraction of major mergers is slightly lower than seen locally. This is in part due to the difficulty of identifying merger signatures at high redshift. The distribution of the U – V color of the galaxies in our sample peaks in the green valley (= 1.1) with a large spread at bluer and redder colors and with the major mergers peaking more strongly in the green valley than the rest of the morphological classes. We argue that, given the number of major gas-rich mergers observed and the relatively short timescale that they would be observable in the (U)LIRG phase, it is plausible for the observed red sequence of massive ellipticals (<10^(12) M_☉) to have been formed entirely by gas-rich major mergers
Interoceptive robustness through environment-mediated morphological development
Typically, AI researchers and roboticists try to realize intelligent behavior
in machines by tuning parameters of a predefined structure (body plan and/or
neural network architecture) using evolutionary or learning algorithms. Another
but not unrelated longstanding property of these systems is their brittleness
to slight aberrations, as highlighted by the growing deep learning literature
on adversarial examples. Here we show robustness can be achieved by evolving
the geometry of soft robots, their control systems, and how their material
properties develop in response to one particular interoceptive stimulus
(engineering stress) during their lifetimes. By doing so we realized robots
that were equally fit but more robust to extreme material defects (such as
might occur during fabrication or by damage thereafter) than robots that did
not develop during their lifetimes, or developed in response to a different
interoceptive stimulus (pressure). This suggests that the interplay between
changes in the containing systems of agents (body plan and/or neural
architecture) at different temporal scales (evolutionary and developmental)
along different modalities (geometry, material properties, synaptic weights)
and in response to different signals (interoceptive and external perception)
all dictate those agents' abilities to evolve or learn capable and robust
strategies
A Multiwavelength Study of a Sample of 70 micron Selected Galaxies in the COSMOS Field II: The Role of Mergers in Galaxy Evolution
We analyze the morphological properties of a large sample of 1503 70 micron
selected galaxies in the COSMOS field spanning the redshift range 0.01<z< 3.5
with a median redshift of 0.5 and an infrared luminosity range of
10^8<L_IR<10^14L_sun with a median luminosity of 10^11.4 L_sun. In general
these galaxies are massive, with a stellar mass range of 10^10-10^12 M_sun, and
luminous, with -25<M_K<-20. We find a strong correlation between the fraction
of major mergers and L_IR, with the fraction at the highest luminosity being up
to 50%. We also find that the fraction of spirals drops dramatically with L_IR.
Minor mergers likely play a role in boosting the infrared luminosity for
sources with low luminosities. The precise fraction of mergers in any given
L_IR bin varies by redshift due to sources at z>1 being difficult to classify
and subject to the effects of band pass shifting, therefore, these numbers can
only be considered lower limits. At z<1, where the morphological
classifications are most robust, major mergers clearly dominate the ULIRG
population (50-80%) and are important for the LIRG population (25-40%). At z>1
the fraction of major mergers is at least 30-40% for ULIRGs. Although the
general morphological trends agree with what has been observed for local
(U)LIRGs, the fraction of major mergers is slightly lower than seen locally.
This is in part due to the difficulty of identifying merger signatures at high
redshift. We argue that given the number of major gas-rich mergers observed and
the relatively short timescale that they would be observable in the (U)LIRG
phase that it is plausible for the observed red sequence of massive ellipticals
(<10^12 M_sun) to have been formed entirely by gas-rich major mergers.Comment: 30 pages, 27 figures, and 6 tables. Accepted for publication in ApJ.
The full resolution version can be found at:
http://www.ifa.hawaii.edu/~jeyhan/paperII/Kartaltepe_70mic_PaperII.pd
Model-based pattern speed estimates for 38 barred galaxies
We have modelled 38 barred galaxies by using near-IR and optical data from
the Ohio State University Bright Spiral Galaxy Survey. We constructed the
gravitational potentials of the galaxies from -band photometry, assuming
constant mass-to-light ratio. The halo component we chose corresponds to the so
called universal rotation curve. In each case, we used the response of gaseous
and stellar particle disc to rigidly rotating potential to determine the
pattern speed.
We find that the pattern speed of the bar depends roughly on the
morphological type. The average value of corotation resonance radius to bar
radius, , increases from in types SB0/a -- SBab to
in SBb and in SBbc -- SBc. Within the error
estimates for the pattern speed and bar radius, all galaxies of type SBab or
earlier have a fast bar (), whereas the bars in later type
galaxies include both fast and slow rotators. Of 16 later type galaxies with a
nominal value of , there are five cases, where the fast
rotating bar is ruled out by the adopted error estimates.
We also study the correlation between the parameter and other
galactic properties. The clearest correlation is with the bar size: the slowest
bars are also the shortest bars when compared to the galaxy size. A weaker
correlation is seen with bar strength in a sense that slow bars tend to be
weaker. These correlations leave room for a possibility that the determined
pattern speed in many galaxies corresponds actually that of the spiral, which
rotates more slowly than the bar. No clear correlation is seen with either the
galaxy luminosity or colour.Comment: 18 pages, 13 figures, accepted for publication in MNRA
Photomorphic analysis techniques: An interim spatial analysis using satellite remote sensor imagery and historical data
The use of machine scanning and/or computer-based techniques to provide greater objectivity in the photomorphic approach was investigated. Photomorphic analysis and its application in regional planning are discussed. Topics included: delineation of photomorphic regions; inadequacies of existing classification systems; tonal and textural characteristics and signature analysis techniques; pattern recognition and Fourier transform analysis; and optical experiments. A bibliography is included
Computer Aided Multi-Data Fusion Dismount Modeling
Recent research efforts strive to address the growing need for dismount surveillance, dismount tracking and characterization. Current work in this area utilizes hyperspectral and multispectral imaging systems to exploit spectral properties in order to detect areas of exposed skin and clothing characteristics. Because of the large bandwidth and high resolution, hyperspectral imaging systems pose great ability to characterize and detect dismounts. A multi-data dismount modeling system where the development and manipulation of dismount models is a necessity. This thesis demonstrates a computer aided multi-data fused dismount model, which facilitates studies of dismount detection, characterization and identification. The system is created by fusing: pixel mapping, signature attachment, and pixel mixing algorithms. The developed multi-data dismount model produces simulated hyperspectral images that closely represent an image collected by a hyperspectral imager. The dismount model can be modified to fit the researcher\u27s needs. The multi-data model structure allows the employment of a database of signatures acquired from several sources. The model is flexible enough to allow further exploitation, enhancement and manipulation. The multi-data dismount model developed in this effort fulfills the need for a dismount modeling tool in a hyperspectral imaging environment
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