461,927 research outputs found
The Differences of Star Formation History Between Merging Galaxies and Field Galaxies in the EDR of the SDSS
Based on the catalog of merging galaxies in the Early Data Release (EDR) of
the Sloan Digital Sky Survey (SDSS), the differences of star formation history
between merging galaxies and field galaxies are studied statistically by means
of three spectroscopic indicators the 4000-\r{A} break strength, the Balmer
absorption-line index, and the specific star formation rate. It is found that
for early-type merging galaxies the interactions will not induce significant
enhancement of the star-formation activity because of its stability and lack of
cool gas. On the other hand, late-type merging galaxies always in general
display more active star formation than field galaxies on different timescales
within about 1Gyr. We also conclude that the mean stellar ages of late-type
merging galaxies are younger than those of late-type field galaxies.Comment: 9 pages, 4 figures, accepted for publication in PAS
Post-Band Merge Utilities Applied to Spitzer Pleiades Data
Band merging extracted point sources observed in multiple wavelength bands is generally done purely on the basis of positional information in order to avoid photometric biases. Automated merge decisions can be more optimal with better position estimation and more realistic modeling of positional estimation errors. Unfortunately, extraction software often does not provide the most accurate positional information possible, and so post-band merge utilities have been developed and implemented to refine both the source positions and the error modeling. Subsequent band merging of the refined detections improves the completeness and reliability of the multi-band source catalog. Application to Spitzer Space Telescope mapping observations of the Pleiades star cluster demonstrates some aspects of the improved band merging
Morphologically-Identified Merging Galaxies in the SWIRE Fields
We investigate the evolutional and environmental effects on star formation
efficiency for more than 400 merging galaxies. The ~400 merging systems, with
photometric redshifts smaller than 0.7, are obtained from a catalog of ~15000
morphologically identified merging galaxies derived from observations of the
Canada-France-Hawaii Telescope. We also obtained the IR data of the merging
galaxies from the Spitzer Wide-area InfraRed Extragalactic Survey (SWIRE). The
redshift differences \Delta z between the member galaxies of these merging
pairs show a large distribution with 0 < \Delta z < 0.4. We divide our merging
pairs into two sub-samples with \Delta z 0.05 for further
analyses. We find a statistically significant anti-correlation between the
specific star formation rate (SSFR) and the separation of the merging galaxies
for both sub-samples. Our analyses also show that although most of the merging
systems do have enhanced star formation activity, only very rare ones display
extremely high SFRs. Additionally, the SSFR of the merging galaxies also
decreases when the magnitude difference between two member galaxies becomes
large. However, we find that for the merging pairs with large luminosity
contrast, the fainter components show higher SSFR than the brighter ones.
Finally, there is a higher fraction of gas-poor mergers in galaxy clusters, and
the SSFR of gas-rich mergers is reduced in cluster environments.Comment: 32 pages, 12 figures and 7 tables; accepted for publication in Ap
Branch merging on continuum trees with applications to regenerative tree growth
We introduce a family of branch merging operations on continuum trees and
show that Ford CRTs are distributionally invariant. This operation is new even
in the special case of the Brownian CRT, which we explore in more detail. The
operations are based on spinal decompositions and a regenerativity preserving
merging procedure of -strings of beads, that is, random
intervals equipped with a random discrete measure
arising in the limit of ordered -Chinese restaurant
processes as introduced recently by Pitman and Winkel. Indeed, we iterate the
branch merging operation recursively and give an alternative approach to the
leaf embedding problem on Ford CRTs related to -regenerative tree growth processes.Comment: 40 pages, 5 figure
Progressive and merging-proof taxation
We investigate the implications and logical relations between progressivity (a principle of distributive justice) and merging-proofness (a strategic principle) in taxation. By means of two characterization results, we show that these two principles are intimately related, despite their different nature. In particular, we show that, in the presence of continuity and consistency (a widely accepted framework for taxation) progressivity implies merging-proofness and that the converse implication holds if we add an additional strategic principle extending the scope of merging-proofness to a multilateral setting. By considering operators on the space of taxation rules, we also show that progressivity is slightly more robust than merging-proofness.taxation, progressivity, merging-proofness, consistency, operators
More than putting on a performance in commercial homes: merging family practices and critical hospitality studies
Critical hospitality studies and family studies have shown a developing theoretical convergence predicated by the âsocial turnâ in the study of hospitality. Recent hospitality research on âCommercial Homesâ has drawn strongly on Goffman's concept of performance to examine both guest and host behaviours. In contrast, this article introduces the family studies concept of âdisplaying familiesâ. This concept emphasises the family practices of host families as well as the commercial practices privileged in studies of hospitality. It also widens the often individualised focus on the (adult) host(s) to one that incorporates the host family. Drawing on empirical evidence, it appears that, for the hosts, displaying families in Commercial Homes is a complex and, apparently paradoxical, mix of presentation and reticence â the family has to be highly visible but not publicly privileged over guests. The inclusion of the concept of display will serve to illuminate further the arenas where family, commercial and hospitality practices intersect
Progressive and merging-proof taxation
We investigate the implications and logical relations between progressivity (a principle of distributive justice) and merging-proofness (a strategic principle) in taxation. By means of two characterization results, we show that these two principles are intimately related, despite their different nature. In particular, we show that, in the presence of continuity and consistency (a widely accepted framework for taxation) progressivity implies merging-proofness and that the converse implication holds if we add an additional strategic principle extending the scope of merging-proofness to a multilateral setting. By considering operators on the space of taxation rules, we also show that progressivity is slightly more robust than merging-proofness.taxation, progressivity, merging-proofness, consistency, operators.
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