Comparison of AGN and Nuclear Starburst Activity in Seyfert 1 and 2 Galaxies over a Wide Luminosity Range Based on Near-infrared 2-4 micrometer Spectroscopy

We present near-infrared K- (1.9-2.5 micrometer) and L- (2.8-4.2 micrometer) band spectroscopy of 22 Seyfert nuclei. We use two methods to investigate the presence of nuclear starbursts: (1) the Polycyclic Aromatic Hydrocarbon (PAH) emission feature at lambda_rest = 3.3 micrometer in the rest frame of L-band spectrum (a starburst indicator) and (2) the CO absorption feature at lambda_rest = 2.3-2.4 micrometer in the rest frame of the K-band spectrum, originating in the CO molecule. We clearly detected the 3.3 micrometer PAH emission features in five objects and the CO absorption features in 17 objects. Seyfert 2 galaxies tend to show bluer K-L colors compared with Seyfert 1 galaxies. We interpret the discrepancy as resulting from relative strength of stellar emission because AGN emission is affected by dust extinction. The 3.3 micrometer PAH emission luminosity (L_3.3PAH) distributions for the Seyfert 1s and Seyfert 2s are very similar when normalized to the AGN power. Star-formation rates estimated from L_3.3PAH could be large enough to inflate the dusty torus by supernova explosion. We find that L_3.3PAH positively correlates with N-band luminosity with small aperture over a wide AGN luminosity range, and is independent of physical area we probed. The results suggest that nuclear region has a concentration of star formation and the star formation would control AGN activity.Comment: 21 pages, 9 figures, 3 tables, accepted for publication in PAS

Infrared 3-4 Micron Spectroscopy of Nearby PG QSOs and AGN-Nuclear Starburst Connections in High-luminosity AGN Populations

We present the results of infrared L-band (3-4 micron) slit spectroscopy of 30 PG QSOs at z < 0.17, the representative sample of local high-luminosity, optically selected AGNs. The 3.3 micron polycyclic aromatic hydrocarbon (PAH) emission feature is used to probe nuclear (< a few kpc) starburst activity and to investigate the connections between AGNs and nuclear starbursts in PG QSOs. The 3.3 micron PAH emission is detected in the individual spectra of 5/30 of the observed PG QSOs. We construct a composite spectrum of PAH-undetected PG QSOs and discern the presence of the 3.3 micron PAH emission therein. We estimate the nuclear-starburst and AGN luminosities from the observed 3.3 micron PAH emission and 3.35 micron continuum luminosities, respectively, and find that the nuclear-starburst-to-AGN luminosity ratios in PG QSOs are similar to those of previously studied AGN populations with lower luminosities, suggesting that AGN-nuclear starburst connections are valid over the wide luminosity range of AGNs in the local universe. The observed nuclear-starburst-to-AGN luminosity ratios in PG QSOs with available supermassive black hole masses are comparable to a theoretical prediction based on the assumption that the growth of a supermassive black hole is controlled by starburst-induced turbulence.Comment: 10 pages, 5 figures, accepted for publication in PASJ (No. 63, 2011 March, Subaru special issue

On chip interconnects for multiprocessor turbo decoding architectures

International audienc

Analysis of Performance of Dynamic Multicast Routing Algorithms

In this paper, three new dynamic multicast routing algorithms based on the greedy tree technique are proposed; Source Optimised Tree, Topology Based Tree and Minimum Diameter Tree. A simulation analysis is presented showing various performance aspects of the algorithms, in which a comparison is made with the greedy and core based tree techniques. The effects of the tree source location on dynamic membership change are also examined. The simulations demonstrate that the Source Optimised Tree algorithm achieves a significant improvement in terms of delay and link usage when compared to the Core Based Tree, and greedy algorithm

Relaxing the Irrevocability Requirement for Online Graph Algorithms

Online graph problems are considered in models where the irrevocability requirement is relaxed. Motivated by practical examples where, for example, there is a cost associated with building a facility and no extra cost associated with doing it later, we consider the Late Accept model, where a request can be accepted at a later point, but any acceptance is irrevocable. Similarly, we also consider a Late Reject model, where an accepted request can later be rejected, but any rejection is irrevocable (this is sometimes called preemption). Finally, we consider the Late Accept/Reject model, where late accepts and rejects are both allowed, but any late reject is irrevocable. For Independent Set, the Late Accept/Reject model is necessary to obtain a constant competitive ratio, but for Vertex Cover the Late Accept model is sufficient and for Minimum Spanning Forest the Late Reject model is sufficient. The Matching problem has a competitive ratio of 2, but in the Late Accept/Reject model, its competitive ratio is 3/2

A Superstabilizing log⁡(n)\log(n)-Approximation Algorithm for Dynamic Steiner Trees

In this paper we design and prove correct a fully dynamic distributed algorithm for maintaining an approximate Steiner tree that connects via a minimum-weight spanning tree a subset of nodes of a network (referred as Steiner members or Steiner group) . Steiner trees are good candidates to efficiently implement communication primitives such as publish/subscribe or multicast, essential building blocks for the new emergent networks (e.g. P2P, sensor or adhoc networks). The cost of the solution returned by our algorithm is at most $\log |S|$ times the cost of an optimal solution, where $S$ is the group of members. Our algorithm improves over existing solutions in several ways. First, it tolerates the dynamism of both the group members and the network. Next, our algorithm is self-stabilizing, that is, it copes with nodes memory corruption. Last but not least, our algorithm is \emph{superstabilizing}. That is, while converging to a correct configuration (i.e., a Steiner tree) after a modification of the network, it keeps offering the Steiner tree service during the stabilization time to all members that have not been affected by this modification

Subaru and Gemini High Spatial Resolution Infrared 18 Micron Imaging Observations of Nearby Luminous Infrared Galaxies

We present the results of a ground-based, high spatial resolution infrared 18 micron imaging study of nearby luminous infrared galaxies (LIRGs), using the Subaru 8.2-m and Gemini South 8.1-m telescopes. The diffraction-limited images routinely achieved with these telescopes in the Q-band (17-23 micron) allow us to investigate the detailed spatial distribution of infrared emission in these LIRGs. We then investigate whether the emission surface brightnesses are modest, as observed in starbursts, or are so high that luminous active galactic nuclei (AGNs; high emission surface brightness energy sources) are indicated. The sample consists of 18 luminous buried AGN candidates and starburst-classified LIRGs identified in earlier infrared spectroscopy. We find that the infrared 18 micron emission from the buried AGN candidates is generally compact, and the estimated emission surface brightnesses are high, sometimes exceeding the maximum value observed in and theoretically predicted for a starburst phenomenon. The starburst-classified LIRGs usually display spatially extended 18 micron emission and the estimated emission surface brightnesses are modest, within the range sustained by a starburst phenomenon. The general agreement between infrared spectroscopic and imaging energy diagnostic methods suggests that both are useful tools for understanding the hidden energy sources of the dusty LIRG population.Comment: 17 pages, 3 figures, accepted for publication in AJ (No. 141, 2011 May issue). Higher resolution version is available at http://optik2.mtk.nao.ac.jp/~imanishi/Paper/20um/20um.pd

Dynamic Steiner Tree Problem

This paper proposes a new problem, which we call the Dynamic Steiner Tree Problem. This is related to multipoint connection routing in communications networks, where the set of nodes to be connected changes over time. This problem can be divided into two cases, one in which rearrangement of existing routes is not allowed and a second in which rearrangement is allowed. In the first case, we show that there is no algorithm whose worst error ratio is less than 1/2 log n where n is the number of nodes to be connected. In the second case, we present an algorithm whose error rate is bounded by a constant and rearrangement is relatively small

Improving Network-on-Chip-based Turbo Decoder Architectures

In this work novel results concerning Networkon- Chip-based turbo decoder architectures are presented. Stemming from previous publications, this work concentrates first on improving the throughput by exploiting adaptive-bandwidth-reduction techniques. This technique shows in the best case an improvement of more than 60 Mb/s. Moreover, it is known that double-binary turbo decoders require higher area than binary ones. This characteristic has the negative effect of increasing the data width of the network nodes. Thus, the second contribution of this work is to reduce the network complexity to support doublebinary codes, by exploiting bit-level and pseudo-floatingpoint representation of the extrinsic information. These two techniques allow for an area reduction of up to more than the 40 % with a performance degradation of about 0.2 d

Comparison of AGN and Nuclear Starburst Activity in Seyfert 1 and 2 Galaxies over a Wide Luminosity Range Based on Near-infrared 2-4 micrometer Spectroscopy

We present near-infrared K- (1.9-2.5 micrometer) and L- (2.8-4.2 micrometer) band spectroscopy of 22 Seyfert nuclei. We use two methods to investigate the presence of nuclear starbursts: (1) the Polycyclic Aromatic Hydrocarbon (PAH) emission feature at lambda_rest = 3.3 micrometer in the rest frame of L-band spectrum (a starburst indicator) and (2) the CO absorption feature at lambda_rest = 2.3-2.4 micrometer in the rest frame of the K-band spectrum, originating in the CO molecule. We clearly detected the 3.3 micrometer PAH emission features in five objects and the CO absorption features in 17 objects. Seyfert 2 galaxies tend to show bluer K-L colors compared with Seyfert 1 galaxies. We interpret the discrepancy as resulting from relative strength of stellar emission because AGN emission is affected by dust extinction. The 3.3 micrometer PAH emission luminosity (L_3.3PAH) distributions for the Seyfert 1s and Seyfert 2s are very similar when normalized to the AGN power. Star-formation rates estimated from L_3.3PAH could be large enough to inflate the dusty torus by supernova explosion. We find that L_3.3PAH positively correlates with N-band luminosity with small aperture over a wide AGN luminosity range, and is independent of physical area we probed. The results suggest that nuclear region has a concentration of star formation and the star formation would control AGN activity.Comment: 21 pages, 9 figures, 3 tables, accepted for publication in PAS