Stellar and Gas Kinematics in the core and bar regions of M100

Original paper can be found at http://www.virtualjournals.org/proceedings/confproceed/783.jsp Copyright American Institute of Physics. DOI: 10.1063/1.2034969 [Full text of this article is not available in the UHRA]Two-dimensional maps of the stellar and gas kinematics of the bar and starbursting circumnuclear region in the barred spiral galaxy M100 are presented. In this progress report, we present maps of the total intensity, mean velocity and velocity dispersion for the stars and the gas. The gas velocity field shows significant kinematic signatures of gas streaming along the inner part of the bar, and across the miniature spiral arms in the nuclear pseudo-ring. The stellar velocity field, presented here for the first time, also shows non-circular motions. The gas velocity dispersion is notably smaller where the star formation occurs in the nuclear zone and HII regions. We outline our further plans with the data set.otherPeer reviewe

A Subarcsecond Resolution Near-infrared Study of Seyfert and Normal Galaxies II. Morphology

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Density wave triggered star formation in grand design spirals

In normal spiral galaxies the arms are the main sites for star formation. This is the cause of their optical contrast compared with the rest of the disc. The spiral structure can be observed as a higher concentration of H2 regions, neutral gas (both atomic and molecular via CO), dust and stars than in the interarm disc. It seens generally accepted that, at least in grand design spirals, there are density waves in the discs. However, several questions are not clear yet and still under discussion. An important question could be termed the triggering dilemma (by analogy with the 'winding dilemma' raised in the forties): Is the enhanced star formation in the spiral arms triggered by the passage of a system of density waves or is it simply due to the presence of a higher column density of gas there? In the present work, we use triggering in the same sense as the moderate to strong triggering defined by Elmegreen (1992), that is to say that star formation in the arms occurs at a rate faster than that in the interarm zone, relative to the available placental gas. Our group has designed several tests to elucidate whether or not star formation is triggered in the arms with respect to the interarm region and we summarize one of them, that of the ratio of the star formation efficiency in the arms divided by that of the interarm zone at the same galactocentric distance which we may call the relative massive star formation efficiency, where the efficiency is defined using the ratio of the mass of stars (evaluated via the H alpha flux) to the mass of neutral gas, atomic plus molecular (which must be measured with the adequate angular resolution). If the relative efficiency is of order unity, the star formation is proportional to the mass of gas, if some kind of induced star formation is present, the relative efficiency should be considerably larger than unity

Gamma-rays from Dark Showers with Twin Higgs Models

We consider a twin WIMP scenario whose twin sector contains a full dark copy of the SM hadrons, where the lightest twin particles are twin pions. By analogy to the standard WIMP paradigm, the dark matter (DM) freezes out through twin electroweak interactions, and annihilates into a dark shower of light twin hadrons. These are either stable or decay predominantly to standard model (SM) photons. We show that this 'hadrosymmetric' scenario can be consistent with all applicable astrophysical, cosmological and collider constraints. In order to decay the twin hadrons before the big-bang nucleosynthesis epoch, an additional portal between the SM and twin sector is required. In most cases we find this additional mediator is within reach of either the LHC or future intensity frontier experiments. Furthermore, we conduct simulations of the dark shower and consequent photon spectra. We find that fits of these spectra to the claimed galactic center gamma-ray excess seen by Fermi-LAT non-trivially coincide with regions of parameter space that both successfully generate the observed DM abundance and exhibit minimal fine-tuning.Comment: 45 pages, 11 figures, v2: journal version, extended discussions in Secs. III-V, references adde

Structure and star formation in disk galaxies. II. Optical Imaging

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Non-circular motion evidences in the circumnuclear region of M100 (NGC 4321)

We analyse new integral field spectroscopy of the inner region (central 2.5 kpc) of the spiral galaxy NGC 4321 to study the peculiar kinematics of this region. Fourier analysis of the velocity residuals obtained by subtracting an axisymmetric rotation model from the $\rm H\alpha$ velocity field, indicates that the distortions are {\em global} features generated by an $m=2$ perturbation of the gravitational potential which can be explained by the nuclear bar. This bar has been previously observed in the near-infrared but not in the optical continuum dominated by star formation. We detect the optical counterpart of this bar in the 2D distribution of the old stellar population (inferred from the equivalent width map of the stellar absorption lines). We apply the Tremaine--Weinberg method to the stellar velocity field to calculate the pattern speed of the inner bar, obtaining a value of $\Omega_b$=160$\pm70\rm km s^{-1} kpc^{-1}$. This value is considerably la rger than the one obtained when a simple bar model is considered. However the uncertainties in the pattern speed determination prevent us to give support to alternative scenarios.Comment: 11 pages, 11 figures, accepted for publication in MNRA

Triggering Soft Bombs at the LHC

Very high multiplicity, spherically-symmetric distributions of soft particles, with $p_T$ ~ few hundred MeV, may be a signature of strongly-coupled hidden valleys that exhibit long, efficient showering windows. With traditional triggers, such "soft bomb" events closely resemble pile-up and are therefore only recorded with minimum bias triggers at a very low efficiency. We demonstrate a proof-of-concept for a high-level triggering strategy that efficiently separates soft bombs from pile-up by searching for a "belt of fire": A high density band of hits on the innermost layer of the tracker. Seeding our proposed high-level trigger with existing jet, missing transverse energy or lepton hardware-level triggers, we show that net trigger efficiencies of order 10% are possible for bombs of mass several hundred GeV. We also consider the special case that soft bombs are the result of an exotic decay of the 125 GeV Higgs. The fiducial rate for "Higgs bombs" triggered in this manner is marginally higher than the rate achievable by triggering directly on a hard muon from associated Higgs production.Comment: 38 pages, 5 tables, 14 figure

A SINFONI view of Galaxy Centers: Morphology and Kinematics of five Nuclear Star Formation Rings

We present near-infrared (H- and K-band) integral-field observations of the circumnuclear star formation rings in five nearby spiral galaxies. The data, obtained at the Very Large Telescope with the SINFONI spectrograph, are used to construct maps of various emission lines that reveal the individual star forming regions ("hot spots") delineating the rings. We derive the morphological parameters of the rings, and construct velocity fields of the stars and the emission line gas. We propose a qualitative, but robust, diagnostic for relative hot spot ages based on the intensity ratios of the emission lines Brackett gamma, HeI, and [FeII]. Application of this diagnostic to the data presented here provides tentative support for a scenario in which star formation in the rings is triggered predominantly at two well-defined regions close to, and downstream from, the intersection of dust lanes along the bar with the inner Lindblad resonance.Comment: 45 pages incl. 4 tables and 12 (mostly color) figures. Accepted for publication in AJ. A version with full resolution figures can be obtained at ftp://ftp.rssd.esa.int/pub/tboeker/SINFONI/ms.pd