225 research outputs found
The Size-Mass Relation of Post-Starburst Galaxies in the Local Universe
We present a study of the size--mass relation for local post-starburst (PSB)
galaxies at selected from the Sloan Digital Sky Survey Data
Release 8. We find that PSB galaxies with stellar mass () at
have their galaxy size smaller than or
comparable with those of quiescent galaxies (QGs). After controlling redshift
and stellar mass, the sizes of PSBs are smaller on average than
those of QGs, such differences become larger and significant towards the
low- end, especially at where PSBs can be on average smaller than QGs.
In comparison with predictions of possible PSB evolutionary pathways from
cosmological simulations, we suggest that a fast quenching of star formation
following a short-lived starburst event (might be induced by major merger)
should be the dominated pathway of our PSB sample. Furthermore, by
cross-matching with group catalogs, we confirm that local PSBs at
are more clustered than more massive ones. PSBs
resided in groups are found to be slightly larger in galaxy size and more
disk-like compared to field PSBs, which is qualitatively consistent with and
thus hints the environment-driven fast quenching pathway for group PSBs. Taken
together, our results support multiple evolutionary pathways for local PSB
galaxies: while massive PSBs are thought of as products of fast quenching
following a major merger-induced starburst, environment-induced fast quenching
should play a role in the evolution of less massive PSBs, especially at
.Comment: 16 pages, 7 figures; accepted for publication in Ap
Meeting-Merging-Mission: A Multi-robot Coordinate Framework for Large-Scale Communication-Limited Exploration
This letter presents a complete framework Meeting-Merging-Mission for
multi-robot exploration under communication restriction. Considering
communication is limited in both bandwidth and range in the real world, we
propose a lightweight environment presentation method and an efficient
cooperative exploration strategy. For lower bandwidth, each robot utilizes
specific polytopes to maintains free space and super frontier information (SFI)
as the source for exploration decision-making. To reduce repeated exploration,
we develop a mission-based protocol that drives robots to share collected
information in stable rendezvous. We also design a complete path planning
scheme for both centralized and decentralized cases. To validate that our
framework is practical and generic, we present an extensive benchmark and
deploy our system into multi-UGV and multi-UAV platforms
Dwarf galaxies with the highest concentration are not thicker than ordinary dwarf galaxies
The formation mechanism of high-concentration dwarf galaxies is still a
mystery. We perform a comparative study of the intrinsic shape of nearby
low-mass galaxies with different stellar concentration. The intrinsic shape is
parameterized by the intermediate-to-major axis ratios B/A and the
minor-to-major axis ratios C/A of triaxial ellipsoidal models. Our galaxies
( < < ) are selected to have
spectroscopic redshift from SDSS or GAMA, and have broadband optical images
from the HSC-SSP Wide layer survey. The deep HSC-SSP images allow to measure
the apparent axis ratios at galactic radii beyond the central star-forming
area of our galaxies. We infer the intrinsic axis ratios based on the
distributions. We find that 1) our galaxies have typical intrinsic shape
similarly close to be oblate ( 0.9--1), regardless of the
concentration, stellar mass, star formation activity, and local environment
(being central or satellite); 2) galaxies with the highest concentration tend
to have intrinsic thickness similar to or (in virtually all cases) slightly
thinner (i.e. smaller mean or equivalently lower triaxiality) than
ordinary galaxies, regardless of other properties explored here. This appears
to be in contrast with the expectation of the classic merger scenario for
high-concentration galaxies. Given the lack of a complete understanding of
dwarf-dwarf merger, we cannot draw a definite conclusion about the relevance of
mergers in the formation of high-concentration dwarfs. Other mechanisms such as
halo spin may also play important roles in the formation of high-concentration
dwarf galaxies.Comment: 12 pages, 8 figures, 2 tables, accepted for publication in Ap
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