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Register a new userH-alpha Kinematics of the SINGS Nearby Galaxies Survey. II
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I. Dicaire
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This is the second part of an H-alpha kinematics follow-up survey of the Spitzer Infrared Nearby Galaxies Survey (SINGS) sample. The aim of this program is to shed new light on the role of baryons and their kinematics and on the dark/luminous matter relation in the star forming regions of galaxies, in relation with studies at other wavelengths. The data for 37 galaxies are presented. The observations were made using Fabry-Perot interferometry with the photon-counting camera FaNTOmM on 4 different telescopes, namely the Canada-France-Hawaii 3.6m, the ESO La Silla 3.6m, the William Herschel 4.2m, and the Observatoire du mont Megantic 1.6m telescopes. The velocity fields are computed using custom IDL routines designed for an optimal use of the data. The kinematical parameters and rotation curves are derived using the GIPSY software. It is shown that non-circular motions associated with galactic bars affect the kinematical parameters fitting and the velocity gradient of the rotation curves. This leads to incorrect determinations of the baryonic and dark matter distributions in the mass models derived from those rotation curves.
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We perform a deep wide-field imaging survey of nearby galaxies using H$alpha$ and broadband filters to investigate the characteristics of star formation in galaxies. Motivated by the finding that star formation rates (SFRs) derived from H$alpha$ fluxes in dwarf galaxies are systematically lower than those inferred from far-ultraviolet (FUV) fluxes, we attempt to determine whether the same trend exists in the extended disks of two star-forming galaxies. We perform spatially resolved photometry using grid-shaped apertures to measure the FUV and H$alpha$ fluxes of star-forming regions. We also perform spectral energy distribution (SED) fittings using 11 photometric data (FUV-to-MIR) including data from the literature to estimate the local properties such as internal attenuation of individual star-forming clumps. Comparing SFR$_mathrm{FUV}$ and SFR$_mathrm{Halpha}$, which are converted from the H$alpha$ and FUV fluxes corrected for the local properties, we find that SFR$_mathrm{Halpha}$/SFR$_mathrm{FUV}$ tends to decrease as the SFR decreases. We evaluate possible causes of this discrepancy between the two SFRs by restricting parameters in the SED fitting and conclude that deficient H$alpha$ fluxes in the extended disks of galaxies are tightly correlated with recent starbursts. The strong and short starburst which is being rapidly suppressed over the last 10 Myr seems to induce a significant discrepancy between the SFR$_mathrm{Halpha}$ and SFR$_mathrm{FUV}$. In addition, the recent bursts in the extended disks of galaxies appear to have occurred azimuth-symmetrically, implying that these were likely triggered by gas accretion or internal processes rather than external perturbation.
We summarize several results based on the velocity data-set for cluster galaxies provided by ENACS (the ESO Nearby Abell Cluster Survey). We describe the distribution of velocity dispersions of a complete sample of rich galaxy clusters, and compare it to the distribution of cluster X-ray temperatures, and with predictions of theoretical models. We then address the issue of the existence of a Fundamental Plane (FP) for rich clusters, first suggested by Schaeffer et al. We confirm the existence of this FP with the ENACS data-set. The cluster FP is different from the FP of elliptical galaxies, and from the virial prediction. Some implications of the cluster FP are discussed. Finally, we describe the phase-space distributions of different populations of cluster galaxies. Different galaxy classes are defined according to their morphological or spectral type, and the presence of emission-lines. Star-forming (late-type) galaxies have a velocity dispersion profile that (in combination with their wider spatial distribution) is suggestive of first infall into the cluster. On the contrary, quiescent (early-type) galaxies show evidence of a dynamically relaxed distribution.
The mechanisms of planet formation are still under debate. We know little about how planets form, even if more than 4000 exoplanets have been detected to date. Recent investigations target the cot of newly born planets: the protoplanetary disk. At the first stages of their life, exoplanets still accrete material from the gas-rich disk in which they are embedded. Transitional disks are indeed disks that show peculiarities, such as gaps, spiral arms, and rings, which can be connected to the presence of substellar companions. To investigate what is responsible for these features, we selected all the known transitional disks in the solar neighborhood (<200 pc) that are visible from the southern hemisphere. We conducted a survey of 11 transitional disks (TDs) with the SPHERE instrument at the VLT. This is the largest Halpha survey that has been conducted so far to look for protoplanets. The observations were performed with the Halpha filter of ZIMPOL in order to target protoplanets that are still in the accretion stage. All the selected targets are very young stars, less than 20 Myr, and show low extinction in the visible. We reduced the ZIMPOL pupil stabilized data by applying the method of the angular spectral differential imaging (ASDI), which combines both techniques. The datacubes are composed of the CntHalpha and the narrow band filter Halpha, which are taken simultaneously to permit the suppression of the speckle pattern. The principal component analysis (PCA) method was employed for the reduction of the data. For each dataset, we derived the 5sigma contrast limit and converted it in upper limits on the accretion luminosity. We do not detect any new accreting substellar companions around the targeted transition disks down to an average contrast of 12 magnitudes at 0.2 arcsec from the central star (continues in the manuscript).
In this work we present scanning Fabry-Perot H$alpha$ observations of the isolated interacting galaxy pair NGC 5278/79 obtained with the PUMA Fabry-Perot interferometer. We derived velocity fields, various kinematic parameters and rotation curves for both galaxies. Our kinematical results together with the fact that dust lanes have been detected in both galaxies, as well as the analysis of surface brightness profiles along the minor axis, allowed us to determine that both components of the interacting pair are trailing spirals.
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